METHOD AND APPARATUS FOR IMPLEMENTING COVERAGE ENHANCEMENT (CE) OPERATIONS

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional

Application No. 61/932,977 filed January 29, 2014, the contents of which is hereby incorporated by reference herein.

BACKGROUND

[0002] In the 3rd Generation Partnership (3GPP) Long Term Evolution

(LTE) Advanced, coverage enhancement techniques have been studied to support Wireless Transmit/Receive Units (WTRUs) which may be located in a coverage limited area. Such a WTRU may be delay-tolerant, have reduced capabilities, or operate with limited service when located in a coverage limited area. An example is a low-cost or low- complexity machine type communication (LC-MTC) WTRU such as a smart meter or sensor which may be located in the basement of a house where very high penetration loss is expected.

SUMMARY

[0003] A method and apparatus for reconfiguration of coverage enhancement (CE) mode and/or level in connected mode are disclosed herein. A method in a wireless transmit/receive unit (WTRU) includes transmitting an indication to an evolved Node B (eNB), wherein the indication includes a request for reconfiguration of a CE mode and level, receiving a configuration of a new CE mode and level from the eNB, and reconfiguring the CE mode and level based on the received configuration.

BRIEF DESCRIPTION OF THE DRAWINGS

[0004] A more detailed understanding may be had from the following description, given by way of example in conjunction with the accompanying drawings, wherein: [0005] FIG. 1A is a system diagram of an example communications system in which one or more disclosed embodiments may be implemented;

[0006] FIG. IB is a system diagram of an example wireless transmit/receive unit (WTRU) that may be used within the communications system illustrated in FIG. 1A;

[0007] FIG. 1C is a system diagram of an example radio access network and an example core network that may be used within the communications system illustrated in FIG. 1A;

[0008] FIG. 2 shows example downlink (DL)/uplink (UL) coupled and decoupled scenarios for wireless communication.

[0009] FIG. 3 is a signal flow diagram of an example intra-long term evolution (LTE) X2 handover procedure;

[0010] FIG. 4 is an example of configuration information for a coverage enhancement (CE) mode physical random access channel (PRACH);

[0011] FIG. 4A is an example of a WTRU in idle mode performing cell re- selection;

[0012] FIG. 5 is an example of dedicated RRC signaling used to indicate

CE mode and/or level change;

[0013] FIG. 6 is an example of a measurement report used to indicate

CE mode and/or level change;

[0014] FIG. 7 is an example of a MAC control element used to indicate

CE mode and/or level change;

[0015] FIG. 8 is an example of utilizing random access to indicate CE mode and/or level change;

[0016] FIG. 9 is an example of a power headroom report used to indicate

CE mode and/or level change;

[0017] FIG. 10 is an example of downlink control information (DCI) usage with fallback operation DCI monitored by a WTRU in a subframe configured by higher layer signaling; and

[0018] FIG. 11 is an example flow diagram of a handover for a WTRU operating with decoupled UL/DL. DETAILED DESCRIPTION

[0019] Figure 1A shows an example communications system 100 in which one or more disclosed embodiments may be implemented. The communications system 100 may be a multiple access system that provides content, such as voice, data, video, messaging, broadcast, and the like, to multiple wireless users or MTC devices. The communications system 100 may enable multiple wireless users to access such content through the sharing of system resources, including wireless bandwidth. For example, the communications systems 100 may employ one or more channel access methods, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), and the like.

[0020] As shown in Figure 1A, the communications system 100 may include wireless transmit/receive units (WTRUs) 102a, 102b, 102c, and/or 102d, a radio access network (RAN) 104, a core network 106, a public switched telephone network (PSTN) 108, the Internet 110, and other networks 112, though it will be appreciated that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and/or network elements. Each of the WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and/or communicate in a wireless environment. By way of example, the WTRUs 102a, 102b, 102c, 102d may be configured to transmit and/or receive wireless signals and may include user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a pager, a cellular telephone, a personal digital assistant (PDA), a smartphone, a laptop, a netbook, a personal computer, a wireless sensor, consumer electronics, MTC devices and the like.

[0021] The communications systems 100 may also include a base station

114a and/or a base station 114b. Each of the base stations 114a, 114b may be any type of device configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, 102d to facilitate access to one or more communication networks, such as the core network 106, the Internet 110, and/or the other networks 112. By way of example, the base stations 114a, 114b may be a base transceiver station (BTS), a Node-B, an evolved Node-B (eNB), a home Node-B (HNB), a home eNB (HeNB), a site controller, an access point (AP), a wireless router, and the like. While the base stations 114a, 114b are each depicted as a single element, it will be appreciated that the base stations 114a, 114b may include any number of interconnected base stations and/or network elements.

[0022] The base station 114a may be part of the RAN 104, which may also include other base stations and/or network elements (not shown), such as a base station controller (BSC), a radio network controller (RNC), relay nodes, and the like. The base station 114a and/or the base station 114b may be configured to transmit and/or receive wireless signals within a particular geographic region, which may be referred to as a cell (not shown). The cell may further be divided into sectors, e.g., cell sectors. For example, the cell associated with the base station 114a may be divided into three sectors. Thus, in one embodiment, the base station 114a may include three transceivers, e.g., one for each sector of the cell. In another embodiment, the base station 114a may employ multiple -input multiple -output (MIMO) technology and, therefore, may utilize multiple transceivers for each sector of the cell.

[0023] The base stations 114a, 114b may communicate with one or more of the WTRUs 102a, 102b, 102c, 102d over an air interface 116, which may be any suitable wireless communication link, (e.g., radio frequency (RF), microwave, infrared (IR), ultraviolet (UV), visible light, and the like). The air interface 116 may be established using any suitable radio access technology (RAT).

[0024] More specifically, as noted above, the communications system

100 may be a multiple access system and may employ one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. For example, the base station 114a in the RAN 104 and the WTRUs 102a, 102b, 102c may implement a radio technology such as universal mobile telecommunications system (UMTS) terrestrial radio access (UTRA), which may establish the air interface 116 using wideband CDMA (WCDMA). WCDMA may include communication protocols such as high-speed packet access (HSPA) and/or evolved HSPA (HSPA+). HSPA may include high-speed downlink packet access (HSDPA) and/or high-speed uplink packet access (HSUPA).

[0025] In another embodiment, the base station 114a and the WTRUs

102a, 102b, 102c may implement a radio technology such as evolved UTRA (E- UTRA), which may establish the air interface 116 using long term evolution (LTE) and/or LTE-advanced (LTE-A).

[0026] In other embodiments, the base station 114a and the WTRUs

102a, 102b, 102c may implement radio technologies such as IEEE 802.16 (i.e., worldwide interoperability for microwave access (WiMAX)), CDMA2000, CDMA2000 IX, CDMA2000 evolution- data optimized (EV-DO), Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), global system for mobile communications (GSM), enhanced data rates for GSM evolution (EDGE), GSM/EDGE RAN (GERAN), and the like.

[0027] The base station 114b in Figure 1A may be a wireless router,

HNB, HeNB, or AP, for example, and may utilize any suitable RAT for facilitating wireless connectivity in a localized area, such as a place of business, a home, a vehicle, a campus, and the like. In one embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.11 to establish a wireless local area network (WLAN). In another embodiment, the base station 114b and the WTRUs 102c, 102d may implement a radio technology such as IEEE 802.15 to establish a wireless personal area network (WPAN). In yet another embodiment, the base station 114b and the WTRUs 102c, 102d may utilize a cellular-based RAT, (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, and the like), to establish a picocell or femtocell. As shown in Figure 1A, the base station 114b may have a direct connection to the Internet 110. Thus, the base station 114b may not be required to access the Internet 110 via the core network 106.

[0028] The RAN 104 may be in communication with the core network

106, which may be any type of network configured to provide voice, data, applications, and/or voice over Internet protocol (VoIP) services to one or more of the WTRUs 102a, 102b, 102c, 102d. For example, the core network 106 may provide call control, billing services, mobile location-based services, pre-paid calling, Internet connectivity, video distribution, and the like, and/or perform high-level security functions, such as user authentication. Although not shown in Figure 1A, it will be appreciated that the RAN 104 and/or the core network 106 may be in direct or indirect communication with other RANs that employ the same RAT as the RAN 104 or a different RAT. For example, in addition to being connected to the RAN 104, which may be utilizing an E- UTRA radio technology, the core network 106 may also be in communication with another RAN (not shown) employing a GSM radio technology.

[0029] The core network 106 may also serve as a gateway for the

WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet 110, and/or other networks 112. The PSTN 108 may include circuit-switched telephone networks that provide plain old telephone service (POTS). The Internet 110 may include a global system of interconnected computer networks and devices that use common communication protocols, such as the transmission control protocol (TCP), user datagram protocol (UDP) and the Internet protocol (IP) in the TCP/IP suite. The networks 112 may include wired or wireless communications networks owned and/or operated by other service providers. For example, the networks 112 may include another core network connected to one or more RANs, which may employ the same RAT as the RAN 104 or a different RAT.

[0030] Some or all of the WTRUs 102a, 102b, 102c, 102d in the communications system 100 may include multi-mode capabilities, i.e., the WTRUs 102a, 102b, 102c, 102d may include multiple transceivers for communicating with different wireless networks over different wireless links. For example, the WTRU 102c shown in Figure 1A may be configured to communicate with the base station 114a, which may employ a cellular -based radio technology, and with the base station 114b, which may employ an IEEE 802 radio technology.

[0031] Figure IB shows an example WTRU 102 that may be used within the communications system 100 shown in Figure 1A. As shown in Figure IB, the WTRU 102 may include a processor 118, a transceiver 120, a transmit/receive element, (e.g., an antenna), 122, a speaker/microphone 124, a keypad 126, a display/touchpad 128, a non-removable memory 130, a removable memory 132, a power source 134, a global positioning system (GPS) chipset 136, and peripherals 138. It will be appreciated that the WTRU 102 may include any sub-combination of the foregoing elements while remaining consistent with an embodiment.

[0032] The processor 118 may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a microprocessor, one or more microprocessors in association with a DSP core, a controller, a microcontroller, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) circuit, an integrated circuit (IC), a state machine, and the like. The processor 118 may perform signal coding, data processing, power control, input/output processing, and/or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 may be coupled to the transceiver 120, which may be coupled to the transmit/receive element 122. While Figure IB depicts the processor 118 and the transceiver 120 as separate components, the processor 118 and the transceiver 120 may be integrated together in an electronic package or chip.

[0033] The transmit/receive element 122 may be configured to transmit signals to, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in one embodiment, the transmit/receive element 122 may be an antenna configured to transmit and/or receive RF signals. In another embodiment, the transmit/receive element 122 may be an emitter/detector configured to transmit and/or receive IR, UV, or visible light signals, for example. In yet another embodiment, the transmit/receive element 122 may be configured to transmit and receive both RF and light signals. The transmit/receive element 122 may be configured to transmit and/or receive any combination of wireless signals.

[0034] In addition, although the transmit/receive element 122 is depicted in Figure IB as a single element, the WTRU 102 may include any number of transmit/receive elements 122. More specifically, the WTRU 102 may employ MIMO technology. Thus, in one embodiment, the WTRU 102 may include two or more transmit/receive elements 122, (e.g., multiple antennas), for transmitting and receiving wireless signals over the air interface 116.

[0035] The transceiver 120 may be configured to modulate the signals that are to be transmitted by the transmit/receive element 122 and to demodulate the signals that are received by the transmit/receive element 122. As noted above, the WTRU 102 may have multi-mode capabilities. Thus, the transceiver 120 may include multiple transceivers for enabling the WTRU 102 to communicate via multiple RATs, such as UTRA and IEEE 802.11, for example.

[0036] The processor 118 of the WTRU 102 may be coupled to, and may receive user input data from, the speaker/microphone 124, the keypad 126, and/or the display/touchpad 128 (e.g., a liquid crystal display (LCD) display unit or organic light- emitting diode (OLED) display unit). The processor 118 may also output user data to the speaker/microphone 124, the keypad 126, and/or the display/touchpad 128. In addition, the processor 118 may access information from, and store data in, any type of suitable memory, such as the non-removable memory 130 and/or the removable memory 132. The nonremovable memory 130 may include random-access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 132 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, and the like. In other embodiments, the processor 118 may access information from, and store data in, memory that is not physically located on the WTRU 102, such as on a server or a home computer (not shown).

[0037] The processor 118 may receive power from the power source 134, and may be configured to distribute and/or control the power to the other components in the WTRU 102. The power source 134 may be any suitable device for powering the WTRU 102. For example, the power source 134 may include one or more dry cell batteries (e.g., nickel- cadmium (NiCd), nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion), and the like), solar cells, fuel cells, and the like.

[0038] The processor 118 may also be coupled to the GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU 102. In addition to, or in lieu of, the information from the GPS chipset 136, the WTRU 102 may receive location information over the air interface 116 from a base station, (e.g., base stations 114a, 114b), and/or determine its location based on the timing of the signals being received from two or more nearby base stations. The WTRU 102 may acquire location information by way of any suitable location- determination method while remaining consistent with an embodiment.

[0039] The processor 118 may further be coupled to other peripherals

138, which may include one or more software and/or hardware modules that provide additional features, functionality and/or wired or wireless connectivity. For example, the peripherals 138 may include an accelerometer, an e-compass, a satellite transceiver, a digital camera (for photographs or video), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands free headset, a Bluetooth® module, a frequency modulated (FM) radio unit, a digital music player, a media player, a video game player module, an Internet browser, and the like.

[0040] Figure 1C shows an example RAN 104 and an example core network 106 that may be used within the communications system 100 shown in Figure 1A. As noted above, the RAN 104 may employ an E-UTRA radio technology to communicate with the WTRUs 102a, 102b, 102c over the air interface 116. The RAN 104 may also be in communication with the core network 106.

[0041] The RAN 104 may include eNBs 140a, 140b, 140c, though it will be appreciated that the RAN 104 may include any number of eNBs while remaining consistent with an embodiment. The eNBs 140a, 140b, 140c may each include one or more transceivers for communicating with the WTRUs 102a, 102b, 102c over the air interface 116. In one embodiment, the eNBs 140a, 140b, 140c may implement MIMO technology. Thus, the eNB 140a, for example, may use multiple antennas to transmit wireless signals to, and receive wireless signals from, the WTRU 102a.

[0042] Each of the eNBs 140a, 140b, 140c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the uplink and/or downlink, and the like. As shown in Figure 1C, the eNBs 140a, 140b, 140c may communicate with one another over an X2 interface.

[0043] The core network 106 shown in Figure 1C may include a mobility management entity (MME) 142, a serving gateway 144, and a packet data network (PDN) gateway 146. While each of the foregoing elements are depicted as part of the core network 106, it will be appreciated that any one of these elements may be owned and/or operated by an entity other than the core network operator.

[0044] The MME 142 may be connected to each of the eNBs 140a, 140b,

140c in the RAN 104 via an Si interface and may serve as a control node. For example, the MME 142 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, bearer activation/deactivation, selecting a particular serving gateway during an initial attach of the WTRUs 102a, 102b, 102c, and the like. The MME 142 may also provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as GSM or WCDMA.

[0045] The serving gateway 144 may be connected to each of the eNBs

140a, 140b, 140c in the RAN 104 via the Si interface. The serving gateway 144 may generally route and forward user data packets to/from the WTRUs 102a, 102b, 102c. The serving gateway 144 may also perform other functions, such as anchoring user planes during inter-eNB handovers, triggering paging when downlink data is available for the WTRUs 102a, 102b, 102c, managing and storing contexts of the WTRUs 102a, 102b, 102c, and the like.

[0046] The serving gateway 144 may also be connected to the PDN gateway 146, which may provide the WTRUs 102a, 102b, 102c with access to packet- switched networks, such as the Internet 110, to facilitate communications between the WTRUs 102a, 102b, 102c and IP-enabled devices.

[0047] The core network 106 may facilitate communications with other networks. For example, the core network 106 may provide the WTRUs 102a, 102b, 102c with access to circuit- switched networks, such as the PSTN 108, to facilitate communications between the WTRUs 102a, 102b, 102c and traditional land-line communications devices. For example, the core network 106 may include, or may communicate with, an IP gateway, (e.g., an IP multimedia subsystem (IMS) server), that serves as an interface between the core network 106 and the PSTN 108. In addition, the core network 106 may provide the WTRUs 102a, 102b, 102c with access to the networks 112, which may include other wired or wireless networks that are owned and/or operated by other service providers.

[0048] Hereafter, WTRU and device may reference normal and low cost or low complexity (e.g., "category 0") WTRUs which may be MTC or LC-MTC WTRUs. WTRU and device may be used interchangeably.

[0049] Figure 2 shows example DL/UL coupled and decoupled scenarios for wireless communications. Figure 2 illustrates a heterogeneous network environment 200 where a WTRU (or LC-MTC device) 201 may be located nearby a low power node 202. In this example, a WTRU (or LC-MTC device) 201 may be located indoors (e.g., inside, including a basement of a house, depicted in Figure 2). In this example, a WTRU (or LC-MTC device) 201 that is not located near the low power node 202 may communicate with a macro eNB 203 for both UL and DL (coupled case), and a WTRU (or LC-MTC device)

201 near the low power node 202 may communicate with the macro eNB 203 in one direction (e.g., DL) and with the low power node 202 in the other direction (e.g., UL). Use of the macro eNB 203 for DL and the low power node

202 for UL may improve coverage because of the transmission power differences between the two nodes. For example, if the macro eNB transmission power is 46 dBm and the low power node transmission power is 27 dBm, the macro eNB 203 may provide much better DL coverage. For the UL, however, coverage may be limited by the UL transmission power of the WTRU (or LC-MTC device) 201. Thus, the closer proximity to the low power node 202 may result in better UL coverage. In some decoupled scenarios, all UL communication of a WTRU may be with a different cell (or cells) than the cell (or cells) the WTRU communicates with in the DL. The cells may belong to different eNBs or the same eNB. In some decoupled scenarios, certain UL communication of a WTRU may be with a different cell (or cells) than the cell (or cells) the WTRU uses for certain DL communication. Some UL communication and some DL communication may be with one cell. The cells may belong to different eNBs or the same eNB.

[0050] An eNB and/or a WTRU may use a Random Access (RA) procedure for at least one of: (i) WTRU initial access (for example to a cell or eNB) and/or registration and/or a Radio Resource Control (RRC) Connection Request such as for initial access or registration; (ii) connection re- establishment such as RRC Connection re-establishment which may follow radio link failure; (iii) access to a handover target cell and/or reset or alignment of WTRU UL timing to a handover target cell, for example for or during a handover; (iv) reset or alignment of WTRU UL timing with respect to a certain cell such as a serving cell, for example to obtain UL synchronization with the cell, such as when UL synchronization may be lost and DL data may arrive or there may be UL data to send; (v) sending and/or receiving a scheduling request (SR), for example when the WTRU may have UL data to send and there may be no dedicated resources (e.g., no PUCCH resources) assigned which may be used for the SR; and/or (vi) positioning purposes such as when timing advance, which may be used for UL timing alignment, may be needed for WTRU positioning.

[0051] A RA procedure may be contention-based (which may also be called common) or non- contention based (which may also be called contention free or dedicated).

[0052] When using a RA procedure which may be a contention-based RA procedure, the WTRU may initiate the process by transmitting a RA preamble that it may randomly select from a common pool of preambles that may be communicated to the WTRU by the network such as via broadcasted system information. The WTRU may transmit the preamble on a PRACH resource (e.g., a resource in time and frequency) that the WTRU may select from a set of allowed resources that may be communicated to the WTRU by the network such as via broadcasted system information. The cell's configured set of PRACH resources may be or may include this set of allowed PRACH resources. The unit of time for the PRACH resource may be a subframe. The subframe the WTRU may select for the PRACH resource may be the next subframe configured for PRACH in which the WTRU may transmit the PRACH (e.g., based on timing, measurement, and/or other WTRU considerations). The WTRU may select a frequency aspect of the PRACH resource (e.g., the resource blocks (RBs)) in the selected subframe, for example, based on parameters which may be communicated to the WTRU by the network, e.g., via broadcasted system information. A frequency resource (e.g., one or at least one frequency resource) may be allowed for PRACH in a subframe for FDD or other cases. It may be defined by a starting (e.g., lowest) RB number that may be provided by the network, e.g., prach- Frequency Offset, and may have a fixed bandwidth such as six RBs.

[0053] Multiple WTRUs may select the same resources (e.g., preamble and PRACH resource) for random access, and a contention situation may be resolved when a contention-based random access procedure is used, or in other cases.

[0054] The WTRU may transmit a RA preamble that may be (e.g., explicitly) signaled to the WTRU by the network, e.g., ra-Preamblelndex, when using a non-contention based RA procedure. The WTRU may transmit the preamble on a PRACH resource that it may select from a specific subset of the cell's configured PRACH resources. The subset (e.g., the mask) may be (e.g., explicitly) signaled to the WTRU by the network, e.g., ra-PRACH- Masklndex. The WTRU may use the indicated resource when the subset may include one choice or in other cases.

[0055] It is contemplated that a preamble transmission may span or be repeated over more than one subframe, for example for contention-based and/or contention-free RA. The selected subframe (e.g., for transmission) may be the starting subframe for the transmission, for example in this and/or other cases.

[0056] A PRACH preamble may be considered a PRACH resource. For example, PRACH resources may include a PRACH preamble, time, and/or frequency resources.

[0057] It is contemplated that the terms RACH resources and PRACH resources may be used interchangeably. It is further contemplated that RA, RACH, and PRACH may be used interchangeably. It is further contemplated that PDCCH and EPDCCH may be used interchangeably. (E)PDCCH may be used to represent PDCCH and/or EPDCCH.

[0058] Mobility for a WTRU in idle mode may require or use a cell selection procedure and/or a cell reselection procedure. Cell selection may be a procedure for the WTRU to find a suitable cell for normal camping and connectivity. A WTRU may perform cell selection for initial access to the network, for transitions from connected mode to idle mode, or for recovery from connectivity failures such as radio link failures. A WTRU with no prior knowledge of the network or cells may perform initial cell selection. A WTRU with some previously stored information about the network and cells may perform cell selection which may be based on the stored information, which may be referred to as a stored information cell selection. In order for a WTRU to deem a cell as a suitable cell, the reference signal received power (RSRP) and reference signal received quality (RSRQ) measurements of the cell may (or may need to) meet the cell selection criterion S. The criterion S may be fulfilled when the following conditions are fulfilled:

Srxlev > 0 and Squal > 0; Equation (1) where:

SrxleV = Qrxlevmeas - (Qrxlevmin + Qrxlevminoffset) - PcOmpenSatlOn; and

Equation (2)

Squal = Qqualmeas— (Qqualmin + Qqualminoffset). Equation (3)

[0059] Qrxlevmeas may be the measured RSRP and Q _qu aimeas may be the measured RSRQ. The other parameters may be cell specific parameters which may be included or specified in system information, such as system information block 1 (SIB1) that may be broadcasted by the cell. If the cell fails to meet the criterion, the WTRU may move to the next detected cell and perform the same check until the criterion may be fulfilled and a suitable cell may be found.

[0060] A WTRU may perform cell re-selection in idle mode when a neighboring cell may become a better choice than the current serving cell, for example, in terms of RSRP and/or RSRQ. The neighboring cell may be an intra-frequency LTE cell, inter-frequency LTE cell or inter-radio access technology (RAT), e.g., UMTS or GSM, cell. The measurements and the determination of cell selection criteria which may trigger the WTRU to reselect to another cell may be performed or implemented by the WTRU based on information which may be provided by the eNB. A WTRU may (e.g., continually) measure and monitor the serving cell. When the serving cell quality falls below a certain threshold, the WTRU may begin to detect and measure neighboring cells. Information regarding neighboring cells and cell reselection criteria may be indicated to a WTRU in SIBs broadcasted from the eNB. There may be certain priorities that may be specified by both eNB and WTRU as part of the evaluation for cell re- selection. For example, the WTRU may be provided with higher priorities for certain frequencies over the current serving cell frequency such that eNB may, to a certain extent, control the frequencies and cells to which the WTRU may re- select. WTRU- determined priorities for cell re- selection may, for example, include the prioritizing of multimedia broadcast multicast service (MBMS) frequencies over other frequencies when a WTRU may prefer to receive MBMS services.

[0061] Mobility of a connected mode WTRU within a LTE network may be supported by network-controlled WTRU-assisted handovers. The decision to handover a WTRU from one cell to another may be made by the source eNB which may be servicing the WTRU. The decision may be based on measurement reports which may be provided by the WTRU and/or other network aspects including traffic load. Once the source eNB decides to move the WTRU to another cell with a target eNB, the source eNB may initiate the handover procedure. The resources which may be required to support moving the WTRU to the target eNB may be prepared prior to notifying the WTRU of the handover.

[0062] Figure 3 is a signal flow diagram of an example intra-LTE X2 handover procedure. A source (or serving) eNB 302 may transmit 307 a measurement control (e.g., a measurement configuration) request (or message) to a WTRU 301 which may indicate (or request) one or more measurements and may provide associated parameters which may include reporting schedules (e.g., for periodic measurement reporting), thresholds or other criteria for triggering a measurement report, and the like. The WTRU 301 may transmit 308 measurement reports to the source eNB 302, for example, according to a periodic reporting schedule or as a result of triggering events such as a measurement crossing a threshold or the result of a comparison of measurements crossing a threshold. The WTRU 301 may transmit 308 a measurement report on UL resources, which may be granted by the source eNB 302 in an UL resource allocation. Based on the measurement reports from a WTRU 301, load conditions, and other criteria, the source eNB 302 may decide 309 to hand the WTRU 301 over to a target eNB 303.

[0063] The source eNB 302 may transmit 310 a handover request to the target eNB 303. The source eNB 302 may provide WTRU-specific information to the target eNB 303, including information regarding the active evolved UMTS terrestrial radio access network (E-UTRAN) radio access bearers (E- RABs) of the WTRU 301. The target eNB 303 may then perform 311 admission control for the WTRU 301, and may provide the source eNB 302 with information which may be necessary for the WTRU 301 to be able to synchronize to the new cell and resume E-RAB services. The target eNB 303 may transmit 312 a handover request acknowledgement to the source eNB 302. The source eNB 302 may transmit 313 an RRC connection reconfiguration message to the WTRU 301. The RRC connection reconfiguration message may include mobility control information. The WTRU 301 may detach from the old cell and synchronize to the new cell. The source eNB 302 may deliver buffered and in transit packets to the target eNB 303. [0064] The source eNB 302 may transmit 314 a sequence number (SN) status transfer message to the target eNB 303. The target eNB 303 may buffer packets (e.g., data packets which may be forwarded) from the source eNB 302. The WTRU 301 may attempt to synchronize 315 with the target eNB 303 by means of a dedicated RA procedure. As part of synchronization 315, the WTRU 301 may transmit a RA preamble on a PRACH resource to the target eNB 303. The target eNB 303 may transmit (e.g., in a RAR) UL allocation and timing alignment 316 for the WTRU 301. Dedicated RA information, e.g., the preamble index and PRACH mask index, may be provided to the WTRU 301 by the source eNB 302 via the RRC connection reconfiguration message 313 (which may be referred to as a handover command). The WTRU 301 may transmit a complete (e.g., RRC reconfiguration complete) message 317 on the allocated UL resources which may complete the execution of the handover by the WTRU 301.

[0065] The source eNB 302 and the target eNB 303, along with an evolved packet core (EPC), may switch the data path from the source eNB 302 to the target eNB 303. The target eNB 303 may transmit a path switch request to an MME 304. The MME 304 may transmit a modify bearer request to a serving gateway 305. The serving gateway 305 may switch the DL path 320. The serving gateway 305 may transmit a modify bearer response 321 to the MME 304. The MME 304 may transmit a path switch request acknowledgement (ACK) 322 to the target eNB 303. The target eNB 303 may transmit a WTRU context release 323 to the source eNB 302. The source eNB 302 may release any resources 324 allocated for the WTRU 301.

[0066] Si handover may involve an MME in between (e.g., handling message transfer between) the source and target eNBs during the handover preparation steps which may include the handover request 310, admission control 311, and handover request ACK 312. The interaction between the source eNB and WTRU, and subsequently the target eNB and WTRU may remain the same in an Si handover procedure as in a X2 handover procedure.

[0067] A WTRU and/or eNB may determine whether a WTRU may operate in normal or coverage enhancement (CE) mode. A WTRU and/or eNB may (or may also) determine the level of coverage enhancement which may enable or be necessary for the WTRU to properly receive from and/or transmit to the eNB. The determination of CE mode and/or level may apply to a WTRU in idle mode and/or connected mode. A WTRU in idle mode may, for example, determine its CE mode and/or level for the purpose of initial access and/or transition to connected mode, e.g., for the purpose of registration and/or data transfer. A WTRU in connected mode may, e.g., continually, monitor its coverage condition: to determine its current CE mode and/or level; and/or to determine a more optimal mode and/or level. A WTRU in connected mode may (or may also), e.g., continually monitor its coverage condition for the possibility of a handover to another cell. For example, the WTRU may or may need to monitor its coverage condition since it may be moving.

[0068] The terms normal mode and non-CE mode may be used interchangeably.

[0069] CE mode may correspond to a mode of operation in which one or more CE levels is (are) supported and/or used and/or coverage enhancement techniques may be used, for example by a WTRU and/or eNB. In some embodiments a CE level of CE mode may be no coverage enhancements which may be the same as normal mode.

[0070] In some embodiments mode and CE mode may be used interchangeably.

[0071] In some embodiments, transmit and send may be used interchangeably.

[0072] A WTRU configured with or for a certain mode such as CE mode may use or be in that mode. In some embodiments, configured with or for a mode may be used interchangeably with using the mode or being in the mode.

[0073] In an embodiment, a WTRU may determine whether it may (or may need to) operate in CE mode or normal mode, for example, for a certain cell which may be a cell selection or reselection candidate, based on DL measurements. The measurements may be based on existing measurements defined for cell selection which may be based on RSRP e.g., Qrxievmeas and RSRQ e.g., Qrxievmeas or new measurements defined for the coverage enhancement determination. The WTRU may perform the measurements to obtain the CE level it may use (or to be used) for cell selection (e.g., for cell prioritization and/or selection decisions).

[0074] A WTRU in idle mode may use the measurements Qrxievmeas and

Qqualmeas for cell selection.

[0075] The WTRU may be provided with different values (e.g., different from the ordinary or normal mode value) of Qrxievmin which may correspond to CE mode and/or CE levels that it may use or operate with. For example, the WTRU may be provided (e.g., via signaling from the eNB such as broadcast signaling) with one or more of: Qrxievmin_CE_Mode, , Qrxievminoffset_CE_Mode, and Pcompensation_cE_Mode.

[0076] For a cell which may be a candidate or may be considered for cell selection, the following criteria (or calculations) may be used, e.g., by the WTRU, to select the mode (e.g., CE mode or normal mode) of the WTRU for the cell:

SrxleV_CE_mode = Qrxievmeas ^~ (Qrxievmin _. _CE_Mode + Qrxlevminoffset_CE_Mode) ^—

Pcompensation_cE_Mod _e ; and Equation (4)

Squal_CE_mode = Qqualmeas - (Qqualmin + Qqualminoffset). Equation (5)

[0077] The CE mode cell selection criteria may be fulfilled (e.g., the mode for the cell may be CE mode) when:

Srxlev_CE_mode > 0 and Squal_CE_mode > 0. Equation (6)

[0078] Thresholds may be provided (e.g., by the eNB) such that if the CE level cell selection criteria is fulfilled, the CE level may be determined from Srxlev_CE_mode and the thresholds, e.g., from the highest (or lowest) threshold exceeded by Srxlev_CE_mode. For example, given normal mode (e.g., Level Normal) and 3 CE levels, e.g., Levell with lowest coverage enhancement, Level2 and Level3 with highest coverage enhancement, which may, for example, correspond to 5, 10, and 15 dB coverage enhancement, the CE level of the WTRU may be determined, e.g., by the WTRU, as follows: CE Level Normal: Srxlev_CE_mode > CE_Level_Normal_Thresh; Equation (7) Where CE_Level_Normal_Thresh may be 0 or Odb CE Level 1: Srxlev_CE_mode < CE_Level_Normal_Thresh AND Srxlev_CE_mode > CE_Levell_Thresh; Equation (8)

CE Level 2: Srxlev_CE_mode < CE_Levell_Thresh AND

Srxlev_CE_mode > CE_Level2_Thresh; and Equation (9)

CE Level 3: Srxlev_CE_mode < CE_Level2_Thresh AND

Srxlev_CE_mode > CE_Level3_Thresh. Equation (10)

[0079] The number of levels of CE mode available may be signaled explicitly or may be determined from the (or the number of) threshold parameters which may be configured. Similar calculations may be configured to use RSRQ using Squal_CE_mode.

[0080] The WTRU may stop the cell selection procedure when a suitable cell with normal coverage is found. For each cell considered, the WTRU may determine if it is suitable for normal mode operation, and if not, if it is suitable for CE mode operation, and if so, may determine the CE level which the WTRU may use or need to use for the cell. The WTRU may maintain a list (e.g., an ordered list) of cells determined for CE mode operation. When a WTRU may find a cell which may meet the suitability criteria for CE mode operation, the WTRU may add the cell to the available list of cells. The WTRU may maintain the list in prioritized order, for example, such that the cells for which the WTRU may use or need less coverage enhancement (e.g., lower CE level) may be higher priority than cells for which the WTRU may use or need more coverage enhancement (e.g., higher CE level). For example, a cell with CE level 1, which may correspond to 5dB coverage enhancement, may be prioritized over a cell with CE level 2, which may correspond to coverage enhancement of 10 dB. When a WTRU completes the cell selection procedure and a normal coverage cell may be found, the WTRU may consider camping on the cell. If no cell may be found with normal coverage, the WTRU may consider camping on a cell which may need the lowest coverage enhancement and/or the highest priority cell in the list which may be ordered based on coverage enhancement which may be needed or required. [0081] As an example of the CE mode cell selection procedure, a WTRU may (e.g., first) search for a cell that may meet suitability criteria in normal operation, for example, out of some or all the cells that may be detected by the WTRU, or possibly from some or all the cells that may have been stored in the WTRU. Once a WTRU has determined that no cell may be found to meet the normal suitability criteria, it may initiate the cell selection procedure for CE mode.

[0082] In another example, a WTRU may detect that a cell may be capable of supporting coverage enhanced operation. For example, a WTRU may detect in a Master Information block (MIB) or other broadcasted system information, an indication that a cell supports coverage enhancements, and may be part of the cell selection and suitability check.

[0083] A way in which a WTRU may determine whether a cell may support coverage enhancement (CE) mode may be based on the cell's transmission or lack of transmission of repeated PBCH. If a cell may transmit PBCH in a subframe other than subframe 0 or may transmit PBCH more than 4 times in a 40 ms window, the WTRU may assume or determine that the cell may support CE mode (e.g., operation).

[0084] A WTRU, which may be in connected mode, may use existing measurements with additional triggers or be configured with new measurements and triggers for detecting and reporting change in CE level. The WTRU may be configured with a measurement configuration to perform CE measurements which may include at least one of: subframes to be used for measurements, measurement periodicity, and triggers to start and stop measurement. The triggers to start measurement may be event based triggers. For example, when the serving cell measurement may be detected (e.g., by the WTRU) to fall below a configured threshold, the WTRU may (or may be configured to) initiate CE measurements. The WTRU may be triggered to stop measurements when the serving cell measurements may be detected (e.g., by the WTRU) above a configured threshold.

[0085] The WTRU may be configured with and/or use a new event and/or new thresholds for existing events for determining change in mode or CE level for the serving cell. For example, the WTRU may be provided with and/or use a new event to trigger the WTRU to transmit a report when it detects the measurement has fallen below a threshold which may correspond to a CE mode or level (e.g., which may be different from the current CE mode or level). The WTRU may be provided with and/or use a new event to trigger the WTRU to transmit a report when it may detect the measurement has fallen below a threshold for the normal conditions (normal threshold) but may be above a CE threshold, e.g., in range of CE operation.

[0086] As an example, consider Event AX:

Entering condition: Ms -Hys < Thresh AND Ms - Hys > CE _ Thresh · _an( J

Equation (11)

Leaving condition: Ms + Hys > Thresh OR Ms - Hys < CE_Thresh , Equation (12) where Ms may represent a measurement, Hys may represent a hysteresis parameter and Thresh and CE_Thresh may represent thresholds which may be provided by the eNB, e.g., via broadcast or other signaling.

[0087] In one embodiment, a WTRU may (e.g., regularly or periodically) evaluate the measurements against a state detection criteria, such as if a serving cell measurement may fall below a configured threshold for normal operations, or if the serving cell may fulfill:

Ms -Hys < Thresh AND Ms - Hys > CE _ Thresh Equation (13) for a configured time TCE, the WTRU may initiate the procedure to determine CE mode for operation. For example, for 3 CE levels, e.g., Levell with lowest coverage enhancement, Level2, and Level3 with highest coverage enhancement, which may, for example correspond to 5, 10, and 15 dB coverage enhancement. The WTRU may select the mode and/or CE level of operation according to the following:

Normal Mode operation: Ms - Hys - Thresh > CE_Level_Normal_Thresh where CE_Level_Normal_Thresh may be 0 or OdB Equation (14)

If the criteria for Normal mode is not satisfied and

if Ms - Hys - CE_Thresh > CE_Level_Normal_Thresh, then:

Equation (15) CE Levell operation : Ms_CE_mode < CE_Level_Normal_Thresh AND

Ms_CE_mode > CE_Levell_Thresh Equation (16)

CE Level2 operation: Ms_CE_mode < CE_Levell_Thresh AND

Ms_CE_mode > CE_Level2_Thresh; and Equation (17)

CE Level3 operation: Ms_CE_mode < CE_Level2_Thresh AND

Ms_CE_mode > CE_Level3_Thresh. Equation (18) where Ms_CE_Mode = Ms - Hys - CE_Thresh. Equation (19)

[0088] The value of Thresh and CE_Thresh may be associated with a threshold for a normal mode operation and threshold for CE mode operation, respectively, and configured or a priori provided by the network. The number of levels and the coverage enhancement of the levels described are for exemplary purposes.

[0089] In addition, the use of 0 dB as the threshold crossing for normal mode or to begin or end a procedure is also exemplary.

[0090] A WTRU may perform a RACH procedure to assist eNB determination of CE level, or to indicate the CE level selected by the WTRU to the eNB. A WTRU may select the PRACH resources and number of repetitions based on the CE level, either determined by the WTRU using WTRU determined means, or explicitly signaled by the eNB.

[0091] In an example, the WTRU may obtain PRACH resource and/or procedure information for CE mode from eNB, e.g., in broadcasted system information such as a System Information Block (SIB), e.g., SIB2 and/or a CE specific SIB. The information may include for each CE level at least one of, the corresponding number of PRACH repetitions, the number of physical resources within a certain number (e.g., 64) subframes, and the preamble sequence number.

[0092] Figure 4 is an example of configuration information for a coverage enhancement (CE) mode PRACH, where 4 CE levels are supported. In a CE_LEVEL_1, e.g. 5Bb, 401 the repetition level 402 may be 4, the number of physical resources within 64 subframes 404 may be 16, and the preamble sequence number 406 may be 4. In a CE_LEVEL_2, e.g. lOdB, 403 the repetition level 402 may be 8, the number of physical resources within 64 subframes 404 may be 8, and the preamble sequence number 406 may be 4. In a CE_LEVEL_3, e.g. 15dB, 405 the repetition level 402 may be 16, the number of physical resources within 64 subframes 404 may be 4, and the preamble sequence number 406 may be 8. In a CE_LEVEL_4, e.g. 20dB, 407 the repetition level 402 may be 32, the number of physical resources within 64 subframes 404 may be 2, and the preamble sequence number 406 may be 16.

[0093] If ra-Preamblelndex, ra-Masklndex and numberOfRepetitions may be provided (e.g., explicitly) by the eNB, then the WTRU may use the values signaled by the eNB. The numberOfRepetitions may be used to indicate the number of repetitions for a PRACH preamble transmission. If one or more of these parameters may be specific to a CE level, then the choice of these parameters may implicitly indicate to the eNB the CE level chosen by the WTRU. Based on the CE level, the WTRU may select an appropriate ra- Preamblelndex and numberOfRepetitions.

[0094] The eNB may, or may also, provide, (e.g., in broadcast or other signaling), the initial PRACH power to (or which may) be used by the WTRU. The eNB may, or may also, provide powerRampingStep if ramping may or is to be performed between consecutive repetitions and/or between preamble transmission attempts (e.g., where one attempt may constitute one set of repeated transmissions).

[0095] The eNB may provide parameters for the CE mode operation in a

CE medium access control (MAC) control element, which may be processed by the WTRU, for example in case of a successful random access response (RAR). The eNB may indicate (e.g., explicitly) the CE level to be, or which may be, used by the WTRU. The eNB may (e.g., explicitly) transmit the UL and/or DL CE level to the WTRU using a MAC control element (e.g., in the RAR). The eNB may provide UL and DL CE levels separately and/or may provide different levels for UL and DL, for example in a case where the eNB may determine the DL and UL may have different CE levels. If no RAR is received by the WTRU within the RAR window, or if none of the received RARs contains the same random access (RA) preamble identity (ID) as the transmitted preamble ID, the RA procedure may be considered unsuccessful. [0096] In case the DL and UL may have different CE levels, the PRACH resources which may be selected by the WTRU which may be based on DL measurements may not be sufficient for the UL. For a WTRU capable of operating in CE mode, when the initial attempt of RA may be unsuccessful, the WTRU may decide or determine to re-initiate or retry the RA procedure with parameters from a PRACH group which may be associated with another, e.g., the next higher CE level (e.g., the level with the next higher amount of coverage enhancement). For example, the WTRU may initiate a RA procedure using normal RA parameters, and if unsuccessful, may re-try with RA parameters for a first (e.g., lowest) CE level, e.g., CE_level_5dB, and so on, until it may be successful or until the maximum number of attempts have been made and/or one or more (e.g., all) CE levels have been tried.

[0097] A WTRU may, e.g., upon or following successful reception of

RAR, receive (e.g., included in the RAR) an indication from the eNB to use a different CE level (e.g., DL and/or UL CE level) compared to the CE level the WTRU may have used for successful preamble transmission. For example, a WTRU may be indicated to configure the CE level (e.g., DL and/or UL CE level) to a reduced CE level, e.g., 5 dB CE level after successfully completing a RA procedure with the eNB at a higher chosen CE level, e.g., 10 dB. The WTRU may receive this indication in the RAR and/or an appropriate configuration message, e.g., RRC reconfiguration message, e.g., to properly configure for the eNB indicated CE level. The WTRU may use the indicated UL and/or DL CE level for transmission in the UL and/or reception in the DL accordingly.

[0098] As part of handover to a target cell, the WTRU may be or may need to be configured with CE mode and CE level when moving to the target eNB and cell. As part of the handover procedure for a CE mode WTRU in connected mode, it may be possible for a WTRU and/or eNB to determine whether the WTRU may operate in CE mode and what CE level it may operate in once it moves to the target cell. The target cell may be of the same eNB as the source cell or a different eNB. As part of a handover procedure, an eNB may handover a WTRU which may be operating in CE mode to a cell in which the WTRU may need less coverage enhancement or even no coverage enhancement.

[0099] In an embodiment, a WTRU may include an indication for possible CE mode operation and/or determined CE level for one or more (e.g., each) detected neighbor cell measurement result in a measurement report. A WTRU may be configured by the eNB to include the CE mode and/or level information as part of the measurement and reporting configuration or may do so for all measurement reports while operating in CE mode. A WTRU may optionally omit that indication if the WTRU determines that it may possibly operate in normal mode if connected to that particular neighbor cell. A WTRU may use the determination of CE mode or normal mode operation and possible CE level on a neighbor cell based on one or more of the procedures defined herein. A WTRU may, for example, as part of determining CE mode and/or level attempt to receive and/or decode a neighboring cell PSS, SSS, legacy PBCH and/or coverage enhanced PBCH. A WTRU may be indicated by the source eNB, e.g., in a measurement configuration, that certain neighboring cells, which may be identified with a physical cell ID (PCI) may support CE mode operation. A WTRU may, or may also, be indicated in the measurement configuration to read PSS/SSS, legacy PBCH and/or enhanced PBCH for certain identified neighboring cells. For example, a WTRU may receive a RRC measurement configuration which may contain an information element indicating "reportCEMode" for certain neighboring cells. As a response, a WTRU may include in the measurement report for the indicated neighboring cell, CE mode and/or level, e.g., along with RSRP/RSRQ measurements. The measurement report may be periodic and/or event triggered.

[0100] Prior to determination of WTRU handover from the source to target cell, the source eNB may determine or receive an indication, for example as part of its neighbor cell management function that the neighboring and target eNB supports CE mode operation. In an embodiment, the source eNB and/or target eNB may determine the CE mode and level for a WTRU with which to operate on the target cell. [0101] The source and/or target eNB may determine the appropriate CE mode and level as a function of at least one of: the current CE mode and level in source cell, WTRU reported measurement result of the target cell, WTRU determination of CE mode and level for the target cell as reported in the measurement report, location information of the WTRU, location information of the source/target eNB, and UL quality information, for example received sounding reference symbol (SRS) quality information or UL PUSCH/PUCCH block error rate (BLER)/bit error rate (BER).

[0102] An eNB may indicate one or more of the above information to a target eNB. For example, the source eNB may include one or more of the above information in an X2 or Si message, possibly as part of the handover preparation procedure. The source eNB may, additionally or instead, indicate its own determined or recommended CE mode and level to the target eNB, which may be based on at least one of the above information. A target eNB, e.g., based on receiving such information along with the handover preparation message (e.g., handover request), may determine whether the WTRU may operate in CE or normal mode on the target cell and which CE level, if CE mode operation may be chosen. For example, CE mode and level determination by the target eNB may be part of its call admission control for the incoming WTRU. Possibly the target eNB may not allow admission of the incoming WTRU based on the determined CE level, which may result in a handover preparation failure. For example, an eNB may reject the handover of a WTRU based on the determination that the CE level for the incoming WTRU may be higher, e.g., 15 dB CE instead of 10 dB CE level, compared to the CE level used in the source eNB. The target eNB may, or may only, admit WTRUs which may operate in normal mode, reduced, e.g., 5 dB instead of 10 dB CE level, or equivalent CE level if operating in CE mode on the target cell.

[0103] A target eNB may determine a different CE mode and level separately for DL and UL of the incoming WTRU, based on the information provided by the source eNB. As another example, based on the determined CE mode and level, the target eNB may partially admit certain allocated radio resources of the incoming WTRU. For example, based on the determined CE level for UL, the target eNB may reject the UL radio bearer that has been configured for the WTRU or may reconfigure the radio bearer that is better suited for the newly determined CE level. The target eNB may apply the partial admission of radio bearers to DL. For example, the target eNB may reject certain DL radio bearers with lower QoS priority to reduce resources or may reject the incoming WTRU.

[0104] A target eNB may indicate its determined CE mode and level, and any call admission decisions, for example, accepted and rejected radio bearers, to the source eNB. For example, this may be signaled in an X2 or Si Handover Preparation Acknowledge message. The target eNB may indicate the determined CE mode and level to the WTRU, e.g., by providing the WTRU with dedicated RACH information which may indicate the CE mode and level that may be used on the target cell. For example, the dedicated pre-amble index and/or subframe mask index may indicate to the WTRU to operate in CE mode and with a determined CE level. An eNB may also indicate CE mode specific frequency/time resources for PRACH to the WTRU to use for contention free (CF) RA on the target cell.

[0105] A target eNB may allocate a CE specific time/frequency resource for the specific purpose of contention free (CF) RA by the CE mode WTRU, and may not allocate the same resource to other CE mode or normal operating WTRUs, as indicated in RA resource configurations, for example in SIB2 or a CE SIB.

[0106] In an embodiment, a WTRU may determine whether to operate in normal mode or CE mode on the target cell upon, or following, receiving the handover command from the source cell, and if in CE mode, which CE level to select initially. For example, the WTRU may use prior measurements of the target cell to determine CE mode and level. A WTRU may determine to use the same CE mode and level as the source cell, without use of measurements for determination.

[0107] A WTRU may indicate the CE mode and level to the target cell by performing contention based (CB) RA towards the target cell, e.g., for the purpose of synchronization as part of the handover procedure. For example, a WTRU may perform CB RA if dedicated RA information may not be provided in the handover command for the target cell. Even if provided with dedicated RA information, the WTRU may perform CB RACH if CE mode is needed in the target cell, for example as determined by the WTRU based on measurements or other means or as indicated by the source eNB.

[0108] A WTRU may indicate to the target cell the desired CE mode and

CE level by choosing the appropriate preamble sequence index and/or PRACH time, e.g., subframe, and/or frequency resource, as allocated in the target cell which may be included in the handover command (which may be an RRC reconfiguration message).

[0109] A WTRU may indicate the CE mode and level to the target cell by performing contention free (CF) RA and choosing the appropriate PRACH frequency resource specifically allocated for CE mode WTRUs. For example, a WTRU may use the preamble index and subframe resource as indicated in the dedicated RA configuration included in the handover command, and may then choose the PRACH frequency resource to reflect the desired CE level. A WTRU may choose a PRACH frequency resource that may be allocated to a CE level that may be different than the CE level that has been determined by the target cell, and possibly indicated in the dedicated PRACH preamble index.

[0110] Using normal mode cell selection and re-selection criteria and priorities, for example for selecting a suitable cell, may result in a WTRU which may be using or may need CE mode to lose coverage and connectivity in idle mode while there may be a cell with which it may operate using CE mode. Modifications to these procedures may therefore be needed.

[0111] Figure 4A is an example of a WTRU in idle mode performing cell re-selection. While in idle mode, a WTRU 400(a) may, e.g., continuously monitor 403(a) the serving cell 401(a) and, e.g., continuously or based on serving cell measurement results of neighboring cells, for example 402(a) and evaluate these cells for possible cell re- selection. A WTRU 400(a) which may be camped on a cell in normal mode, e.g., operating in normal mode, may evaluate for cell re- selection to another cell in normal mode, and may use legacy cell re-selection evaluation. A normal mode WTRU may also consider cell re- selection to the same or another cell and may operate in CE mode upon cell re- selection. For example, the WTRU 400(a) may be operating in normal mode with its serving cell 401(a). The WTRU 400(a) may move out of the normal coverage area of its serving cell 401(a) and into the normal, e.g., outdoor, coverage area of neighbor cell 402(a) but may move indoors which may be out of the normal coverage area of neighbor cell 402(a). The WTRU 401(a) may perform CE mode cell re-selection and may re-select to its serving cell 401(a) using CE mode, for example if the eNB of neighbor cell 402(a) may not support CE mode. The WTRU 400(a), e.g., as part of the CE mode cell re- selection procedure, may perform a RA procedure 404(a) on the re- selected cell to indicate to the eNB that the WTRU 400(a) is (or may be) using CE mode, has (or may have) transitioned from normal mode to CE mode or has (or may have) changed CE levels.

[0112] A WTRU camped on a cell in CE mode may, or may also, perform evaluations for cell re- selection to other cells in CE mode, and for cell re- selection to the same cell and other cells for normal mode operations.

[0113] A WTRU may change its mode (e.g., normal or CE) and/or CE level in its serving cell using a cell re-selection procedure. It is contemplated that CE level change may be a separate procedure from cell re- selection, but may involve one or more steps or actions which may be described for CE mode or CE level cell re-selection. For example, a RA procedure may be used, for example to access the cell with the changed level and/or inform the cell of the change.

[0114] A WTRU which may be camped normally on a cell may initiate measurements and evaluation for cell re-selection to the same cell or to a neighboring cell for CE mode operation, for example, when the measured RSRP and/or RSRQ of the current serving cell may have dropped below a certain threshold. A WTRU may use the threshold, for example indicated by the eNB in a broadcasted SIB such as SIB3 or a CE mode SIB, or in dedicated signaling. The WTRU may initiate measurements and evaluation for CE mode re-selection if the threshold has been reached or crossed and there may be no neighbor cell candidates in any frequency (or certain frequencies) for (e.g., that satisfy the criteria for) normal mode or normal mode cell re-selection.

[0115] A WTRU may evaluate some or all detectable neighbor cells for

CE mode cell re-selection as higher priority inter-frequency cells. A WTRU may determine whether a detected neighbor cell may support CE mode WTRU operation by finding an indication of such support in broadcasted system information, or by attempting to decode PBCH using the enhanced repetition burst. A WTRU may consider a neighbor cell as a candidate cell (e.g., for CE mode re-selection) if, e.g., only if, the indication or PBCH repetition burst may be detected. A WTRU may, or may also, receive indication as to whether neighboring cells support CE mode in the current serving cell broadcast information or via dedicated signaling from the current serving cell.

[0116] A cell which may support CE mode operation may provide repetitions of a PBCH within a radio frame. The set of repetitions, which may include or exclude the legacy PBCH, may constitute a PBCH repetition burst.

[0117] A WTRU which may be operating in normal (or CE) mode may re-select in CE (or normal) mode to a neighbor cell if the RSRP and/or RSRQ values of a neighbor cell may cross (e.g., exceed) a threshold for a specified duration of time. A WTRU may re-select to another cell without comparing the current serving cell measured RSRP and/or RSRQ value against a threshold.

[0118] For example, a WTRU may receive parameters ScE_SearchP and

Threshx, CE_P, (e.g., in a SIB) from the cell on which the WTRU may be camped normally. The WTRU may use the parameters, respectively, as a RSRP measurement threshold for starting CE mode cell re- selection evaluations and a threshold value for re- selecting to a candidate cell. For example, once (or when) RSRP measurements (e.g., for the serving cell) fall below ScE_SearchP, e.g., Srxlev < SCE_ _SearchP, and there are no longer any cell re-selection candidates for normal cell re-selection, a WTRU may start evaluations for CE mode cell re- selection. A WTRU may use existing detected neighbor cells and measurements to evaluate CE mode cell re-selection candidates. If a candidate cell RSRP may exceed the Threshx, CE_P threshold, e.g., Srxlev, n > Threshx, CE_P, a WTRU may re- select to that cell, and consider it to be camped on that cell in CE mode. A WTRU may perform a RA procedure to indicate to the re- selected cell that a WTRU may camp on that cell in CE mode or a different CE level. One threshold may be provided, e.g., Threshx,cE_p, for CE mode in general and/or a threshold may be provided for each CE level and may be used by the WTRU to determine the CE level for the re- selected cell.

[0119] A WTRU which may be camped on a cell in CE mode may initiate measurements and evaluation for cell re- selection to either another cell in CE mode or normal mode where this may be done with or without any evaluation of the current cell RSRP or RSRQ falling below a threshold. A WTRU may consider all neighbor cells to be of higher priority than the current one. A WTRU may evaluate for normal re- selection based on thresholds and evaluations based on legacy cell re-selection procedures. A WTRU may evaluate for CE mode cell re-selection based on a CE mode re-selection threshold. For example, a WTRU may be provided with Threshx, CE_P threshold parameter. If any neighboring cell RSRP may exceed this threshold parameter, then the WTRU may re-select to that candidate cell in CE mode.

[0120] A CE mode WTRU in connected mode which is moving, may experience more dynamic changes to its coverage environment which in turn may change the CE mode operation and/or CE level needed. In order to maintain optimal use of resources by WTRU and eNB, a reconfiguration of CE mode and level may be desirable.

[0121] A WTRU which may be operating in CE mode and may be moving within a cell may experience changes to its coverage conditions. Additionally, a WTRU which may be in connected mode may benefit from the dynamic reconfiguration of CE mode and level. For example, a WTRU may experience improved coverage conditions, to the extent that the level of CE may be decreased, e.g., from 10 dB CE to 5 dB CE level, or possibly change to operate in normal mode without any coverage enhancements. A reconfiguration of CE mode and/or level, in improved coverage conditions may allow for a WTRU to operate more efficiently, e.g., both from resource and power perspective, while maintaining coverage and any on-going data transfer. In another example, a WTRU may experience worsening coverage conditions, in which case a WTRU may reconfigure from normal operation to CE mode operation or reconfigure such that the CE level may be increased, e.g., from 5 dB to 10 dB CE level. It may be beneficial for a WTRU to be able to reconfigure the CE mode and/or level in worsening coverage conditions to be able to maintain coverage without losing connectivity.

[0122] The embodiments described herein provide means to enable a

WTRU and/or eNB to perform reconfiguration of a current CE mode and/or level while remaining in connected mode. A WTRU and/or eNB may reconfigure the CE mode and/or level while the WTRU may remain in connected mode, for example, based on measurements and other mechanisms for CE mode and level determination described herein.

[0123] In an embodiment, a WTRU may provide an indication for reconfiguration of CE mode and/or CE level to the eNB in one or more of the following ways: using dedicated RRC signaling, using a measurement report, using a MAC control element, using random access, using power headroom, and/or using CE level pre-configuration.

[0124] Figure 5 is an example of dedicated RRC signaling which may be used to indicate a need, desire, or request for mode (or CE mode) and/or CE level change. A WTRU 501 may indicate the reconfiguration (or needed or desired reconfiguration) of mode (or CE mode) and/or CE level 503 to the eNB 502 in a RRC message. For example, a WTRU 501 may indicate in the RRC message to the eNB 502 to (or a desire to or request to) reconfigure from CE mode to normal mode operation, or from normal mode operation to CE mode operation possibly with a CE level indicated, or may indicate a different CE level for use while maintaining CE mode operation. An eNB 502 may respond with a configuration to update CE mode operation for the indicated (or another) CE level 504, or possibly with configuration for normal operation. The WTRU 501 may update its mode (e.g., to or from CE mode) and/or CE level 505 and the related parameters according to the configuration 504 provided by the eNB 502. The WTRU and eNB may (e.g., now) communicate using the updated mode and/or CE level. A WTRU 501 may perform "smooth reconfiguration" of the mode (or CE mode) and/or CE level using dedicated RRC signaling in both worsening and improving coverage conditions, possibly without losing connectivity or on-going data transfers with the eNB 502.

[0125] Figure 6 is an example of a measurement report which may be used to indicate a need, desire, or request for mode (or CE mode) and/or CE level change. A WTRU 601 may be configured to transmit an event triggered measurement report 603 to the eNB 602 in case coverage conditions change and a mode (or CE mode) or CE level reconfiguration may be needed or possible. A WTRU 601 may include in the measurement report RSRP and/or RSRQ measurement results for the serving cell and possibly the event, e.g., Event AX, that triggered the measurement report. The eNB 602 may respond with a configuration to update CE mode operation for the indicated or another CE level 604, or possibly with configurations for normal operation. The WTRU 601 may update its mode (e.g., to or from CE mode) and/or CE level 605 and the related parameters according to the configuration 604 provided by the eNB 602. The WTRU and eNB may (e.g., now) communicate using the updated mode and/or CE level.

[0126] Figure 7 is an example of a MAC control element which may be used to indicate a need, desire, or request for mode (or CE mode) and/or CE level change. A WTRU 701 may include a MAC control element in a scheduled PUSCH transmission 703 to indicate a requested/desired reconfiguration of mode (or CE mode) and/or CE level to the eNB 702. A WTRU 701 may include the requested/desired reconfigured mode (or CE mode) and/or CE level in the MAC control element. The eNB 702 may respond with a configuration to update CE mode operation for the indicated (or another) CE level 704, or possibly configurations for normal operation. The WTRU 701 may update its mode (e.g., to or from CE mode) and/or CE level 705 and the related parameters according to the configuration 704 provided by the eNB 702. The WTRU and eNB may (e.g., now) communicate using the updated mode and/or CE level.

[0127] Figure 8 is an example of utilizing random access (RA) to indicate mode (or CE mode) and/or CE level change. A WTRU 801 may initiate 803 and perform contention based (CB) RA 804 to indicate to the eNB 802 a reconfiguration (e.g., which may be performed autonomously by the WTRU) of mode (or CE mode) and/or CE level. The WTRU 801 may choose the preamble index and/or PRACH time and frequency resources based on the reconfigured CE or normal mode operation and/or CE level. For example, a WTRU 801 may perform CB RA based on a normal RA procedure, e.g., no repetition, and may choose the preamble index and PRACH resources allocated to normal mode operations, e.g., as specified in the cell broadcasted SIB2, in order to indicate a reconfiguration from CE mode to normal operation which may be due to improved coverage conditions. In another example, a WTRU 801 may perform CB RA based on a coverage enhancement RA procedure, e.g., with repetition, and may choose the preamble index and PRACH resources which may be allocated to the desired CE level of CE mode to indicate a reconfiguration from normal mode to CE mode operation, for example, due to worsened coverage conditions. A WTRU 801 may suspend any scheduled PUCCH and/or PUSCH transmissions in a subframe, in order to start the CB RA procedure and transmit the PRACH preamble in that subframe. The eNB 802 may respond with configuration for the updated mode (or CE mode) operation for the indicated CE level 805. The eNB may respond using the updated mode and/or CE level for the communication with the WTRU. Alternatively, the eNB 802 may respond with a configuration to update CE mode operation for the indicated (or another) CE level 805, or possibly configurations for normal operation. The WTRU 801 may apply a configuration of mode, CE level and/or related parameters 806 it may receive from the eNB 802. The WTRU and eNB may (e.g., now) communicate using the updated mode and/or CE level.

[0128] Figure 9 is an example of a power headroom report used to indicate mode (or CE mode) and/or CE level change. A WTRU 901 may indicate to the eNB 902 to (or the need, desire, or request to) reconfigure the current mode (or CE mode) and/or CE level by transmitting a power headroom report (PHR) 903. A WTRU 901 may trigger the transmission of PHR based on the determination to (or that there is a need or desire to) reconfigure the mode (or CE mode) and/or CE level. This PHR transmission may coincide with a PHR trigger which may be based on pathloss change due to changes in coverage conditions and/or RSRP measurements, or may be separate from the pathloss change trigger. Possibly, the WTRU 901 may use the two reserved bits in the PHR control element to indicate the (e.g., the needed or desired) CE mode and level. For example '00' may indicate normal mode operation whereas '11' may indicate a certain level of CE mode operation such as 15dB CE mode. The eNB 902 may respond with a configuration to update CE mode operation for the indicated (or another) CE level 904, or possibly configurations for normal operation. The WTRU 701 may update its mode (e.g., to or from CE mode) and/or CE level 905 and the related parameters according to the configuration 904 provided by the eNB 902. The WTRU and eNB may (e.g., now) communicate using the updated mode and/or CE level.

[0129] CE Level Pre-configuration may be provided and/or used. A

WTRU may be configured with step mechanisms to increase or decrease the CE level state, e.g., move to a higher CE level or lower CE level based on a step quantity provided. For example, a WTRU may be configured with a "CE level increment" command to move from CE_Level_xdB to CE_Level_x+ydB and/or "CE level decrement" mechanisms to reduce the CE level, e.g., move from CE_Level_xdB to CE_Level_x-ydB, where x may be the existing CE level, and y may be the step increment for the procedure. The x and y values may be pre-configured, or signaled a priori for the cell or signaled using a dedicated message with the reconfiguration command.

[0130] In an embodiment, an eNB may provide a PDCCH ordered RA procedure, e.g., PDCCH downlink control indicator (DCI) format 1A to the WTRU. For example, an eNB may order the WTRU to initiate a RA procedure based on its own internal measurement which may indicate a possible change to CE mode and level for the WTRU. Possibly, the PDCCH ordered RA may be in response to one of the above indications which may be received from the WTRU. An eNB may include a PRACH preamble index and/or subframe mask, e.g., in the PDCCH, such that the WTRU may perform a CF RA. The preamble index and subframe mask may be based on the PRACH resources allocated for CE mode operation and CE level by the eNB. Possibly, the eNB may omit the preamble index or subframe mask in the PDCCH, such that the WTRU may perform a CB RA, and the WTRU may indicate its determined CE mode and level.

[0131] In response to the indications from the WTRU, an eNB may provide a RRC reconfiguration message or MAC control element which may contain the reconfigured mode (or CE mode) and CE level configuration information to the WTRU. During the transition period in which there may be some ambiguity between the eNB and the WTRU in terms of which CE level configuration may be used for reception and transmissions, a WTRU may use a fallback scheme for both transmission and reception.

[0132] The terms PDCCH, enhanced PDCCH (EPDCCH), (E)PDCCH, and MTC PDCCH (M-PDCCH) may be used interchangeably.

[0133] For a WTRU in CE mode, when radio link failure (RLF) may be detected and access stratum (AS) security may have been activated, a WTRU may initiate the re-establishment procedure using a contention based RA.

[0134] The RLF procedure may be enhanced or replaced for WTRUs which may support Coverage Enhancement. For example, the normal RLF may be detected because the WTRU may have moved out of an area of normal coverage and detected out-of-sync indication may be triggered from physical layer. A WTRU which supports CE mode may initiate operation in CE mode rather than declaring RLF or performing one or more actions or procedures which may be associated with RLF. The WTRU may recompute (or determine or select) a CE level, for example according to an embodiment described herein. The WTRU may perform a re-establishment procedure with its serving cell in a CE mode.

[0135] As part of the re-establishment procedure, a WTRU may determine to reconfigure to CE mode or change the CE level, and may indicate that information to the eNB, for example, by a random access procedure which may be associated with the re-establishment procedure. A reconfiguration of CE mode and level where the WTRU loses connectivity to the eNB and then re-establishes the connection with an increased CE level may be considered a "hard" CE level reconfiguration. As part of the re-establishment procedure in CE mode, a WTRU may also consider other cells besides the current serving cell as part of its cell selection to perform the RA procedure. A WTRU may initiate a contention based (CB) RACH to transmit the re-establishment message to indicate to the eNB a reconfiguration of CE mode and/or CE level.

[0136] A WTRU may perform radio link monitoring (RLM) for normal coverage and may monitor for the different levels in CE mode. A WTRU may allocate a minimum quality threshold for each CE level, e.g., QsdB _. CE, QiodB_CE, Qi5dB_CE, along with the RLM in-sync and out-of-sync thresholds, Qi _n and Q _ou t respectively. A WTRU may allocate the CE level thresholds based on one or more of the following quality parameters: PDCCH BLER, coverage enhancement repetition level, PDSCH BLER, and/or PUCCH/PUSCH BLER.

[0137] PDCCH BLER: Each threshold may be based on the received or theoretical PDCCH BLER. One or more of the Q thresholds for the CE levels may be below Qout of 10%.

[0138] Coverage enhancement repetition level: Each threshold may be based on the expected received repetition of a signal or channel before the data may be received and decoded without error in the corresponding coverage level. For example, the threshold may be based on number of PSS/SSS or PBCH repetitions before correct decoding of that signal or channel. If that number exceeds a threshold for one CE level (e.g., 5 dB CE level), it may indicate to the WTRU that a higher CE level (e.g., lOdB CE level) may be better suited for the current coverage conditions.

[0139] PDSCH BLER: Each threshold may be based on the received or theoretical PDSCH BLER, given a fixed modulation and coding scheme

(MCS). For example, a LC-MTC device may be provided with a Q threshold based on PDSCH BLER given a fixed MCS for each PDSCH transmission and limited PRB (e.g., 6 PRB) channel bandwidth for PDSCH.

[0140] PUCCH/PUSCH BLER: A WTRU may allocate the Q threshold based on BLER of an UL channel such as PUCCH or PUSCH.

[0141] A WTRU may monitor for the above thresholds directly as part of radio link monitoring, or may monitor by comparing the threshold to a quality measurement such as RSRP or RSRQ. A WTRU may set the above quality thresholds for RSRP/RSRQ based on a theoretical measurement of the above quality parameters.

[0142] A WTRU may be provided with RLM related counters, e.g., N310, for consecutive out-of-sync indications, for each or all of the CE level Q thresholds. A default set of counters may be defined in RRC or otherwise a WTRU may receive the counter values via SIB2 or another broadcasted SIB from the eNB.

[0143] In an example, a WTRU operating in CE mode may monitor

RSRP for the purpose of RLM, may specify (or determine or use) the Q thresholds in terms of RSRP values, and may compare the thresholds to measured RSRP value. A WTRU may be operating in CE mode with a certain CE level (e.g., 5dB level CE). A WTRU then may perform RLM for the various thresholds based on the continued RSRP measurements of the current serving cell. For example, a WTRU may experience improved coverage enhancement such that the RSRP measurements exceed Qi _n threshold value for specified consecutive number (e.g., N310) of measurement intervals, then a WTRU may consider the coverage condition has improved to a point where CE mode may no longer be needed and may operate in normal mode. As part of the RLM procedure, a WTRU may then perform contention based RA to indicate to the eNB to reconfigure from CE mode to normal mode operations. As another example, a WTRU may measure RSRP such that coverage conditions become worse, and a WTRU measures that the RSRP value falls below a threshold (e.g., QsdB _. CE threshold), for N consecutive number of measurement intervals. In this WTRU may determine that CE mode with increased (or higher)

CE level (e.g., lOdB rather than 5 dB) may be preferred and may indicate this to the eNB by performing a contention based RACH to the eNB. A WTRU may maintain the current CE level (e.g., 5 dB) if RSRP measurements improve within the N consecutive measurement interval.

[0144] In another example, a WTRU may define one of the CE level Q thresholds to be lower than that of Qout in terms of RSRP value. In this WTRU which may measure an RSRP value below Qout threshold for N310 consecutive measurement interval may not declare radio link failure if the measured RSRP value is still above another CE level Q threshold. Instead, a WTRU may declare radio link failure once the measured RSRP value falls below the higher CE level Q threshold, e.g., Qi5dB_CE, for N consecutive measurement intervals.

[0145] A WTRU in connected mode may be (re)configured semi- statically or dynamically with either normal mode or CE mode. The normal mode may include a transmission mode without coverage enhancement operations such as repetitive transmission of data channels (e.g., PDSCH, PUSCH), control channels (e.g., PUCCH, (E)PDCCH), and broadcast/multicast channels. In addition, the CE mode may include a transmission mode using CE operations. For the reconfiguration of the mode of operation between normal mode and CE mode, fallback transmission scheme may be used in order to handle ambiguity period during higher layer configuration and reconfiguration.

[0146] In an embodiment, a DCI format may be defined for the fallback transmission scheme which may be used in both normal mode and CE mode. The DCI format may be newly defined or modified from an existing DCI format. If a new DCI format is defined, one or more of following may apply.

[0147] A WTRU, e.g., a WTRU capable of both normal mode and CE mode, may monitor a new DCI format (e.g., fallback DCI, DCI format 5) associated with the fallback transmission. The new DCI format may be used to support mode adaptation between normal mode and CE mode, wherein the new DCI format may be monitored (e.g. by the WTRU) in all downlink subframes or in a subset of downlink subframes. The new DCI format associated with the fallback transmission may be based on a transmission scheme used in CE mode. For example, a WTRU, e.g., a WTRU operating in the normal mode and capable of both normal mode and CE mode, may monitor the fallback DCI in all downlink subframes or in a subset of subframes, wherein the fallback DCI may be transmitted via a PDCCH (or EPDCCH) used in CE mode (e.g. PDCCH or EPDCCH transmitted with repetitions). The fallback DCI may be monitored (e.g., by the WTRU) with a certain transmission mode (which may support the mode adaptation between normal mode and CE mode), wherein the certain transmission mode may be a subset of transmission modes used in normal mode and/or CE mode (e.g., transmission modes 1, 2, and 7 in normal mode of operation).

[0148] Figure 10 shows an example of the new DCI format usage. Figure

10 is an example of downlink control information (DCI) usage with fallback operation DCI monitored by a WTRU in a subframe configured by higher layer signaling. Figure 10 shows DCI format 1001, search space in a DL subframe 1002, and search space across DL subframes 1003, for different transmission modes 1000. For example, the different transmission modes 1000 may be transmission mode 1, transmission mode 2, transmission mode 3, transmission mode 4, transmission mode 5, transmission mode 6, transmission mode 7, transmission mode 8, and transmission mode 9.

[0149] The downlink subframe wherein a WTRU may need to monitor the new DCI format (e.g., fallback DCI) may be defined (or determined) based on at least one of the following: a set of downlink subframes configured via higher layer signaling, a set of downlink subframes that may be predefined, and a set of downlink subframes that may be defined as a function of physical cell ID. A WTRU, e.g., a WTRU capable of both normal and CE modes, may or may need to monitor the new DCI format (e.g., fallback DCI) in a (e.g., each) subframe of the set of downlink subframes that is at least one of: configured, defined, or a function of physical cell ID.

[0150] A set of downlink subframes to monitor may be configured via higher layer signaling. A WTRU, e.g., a WTRU capable of both normal and CE modes which may be configured with a transmission mode supporting mode adaptation, may (or may need to) monitor the new DCI format (e.g., fallback DCI) in the downlink subframes configured to monitor.

[0151] A set of downlink subframes may be predefined. For example, the subframes in the range of system frame number (SFN) 0 to SFN 9 may be used for the new DCI format monitoring.

[0152] A set of downlink subframes may be defined as a function of physical cell ID. For example, a starting SFN number may be determined as a function of the physical cell ID and consecutive Nseq SFN may be used to indicate the downlink subframes in which the WTRU may (or may need to) monitor the fallback DCI.

[0153] The mode adaptation between normal mode and CE mode may be supported within a transmission mode. For example, a WTRU may be configured (or change) from normal mode to CE mode when the WTRU may be configured and operating with TM1 for both normal mode and CE mode. However, a WTRU may not be (re)configured (or change) from TM1 normal mode to TM2 CE mode.

[0154] The mode switching between transmission modes (e.g., TM1-

TM9) may be allowed in the normal mode operation, e.g., only. If a WTRU may be (or may need to be) (re)configured to CE mode with a specific transmission mode, the WTRU may need to be in the same transmission mode in the normal mode.

[0155] The new DCI format (e.g., fallback DCI) may be transmitted with repetition over multiple TTIs. One or more of following may apply: the number of repetitions (or CE level) for the new DCI format may be configured via higher layer signaling, or a set of repetitions may be predefined and a WTRU may monitor the new DCI format with multiple attempts (e.g., blind decoding of multiple decoding candidates), or the lowest CE level may be used, or the highest CE level may be used.

[0156] A new DCI format (e.g., fallback DCI, DCI format 5) associated with the fallback transmission may include at least one of following: resource allocation fields, modulation and coding scheme, localized/distributed virtual resource block (VRB) assignment flag, hybrid automatic repeat request (HARQ) process number, new data indicator, redundancy version, transmit power control (TPC) command, SRS request, and the number of repetition for PDSCH or PUSCH.

[0157] In another embodiment, a WTRU may be configured with two types of C-RNTI such as C-RNTI and coverage enhancement C-RNTI (CE-C- RNTI). In this case, one or more of following may apply.

[0158] If a WTRU is configured (or operating) with normal mode, the C-

RNTI may be used to monitor (E)PDCCH and may be used for the scrambling sequence of the demodulation reference signals (DM-RS) while the CE-C- RNTI may be used to monitor (E)PDCCH and may be used for scrambling of the DM-RS if a WTRU is configured (or operating) with CE mode.

[0159] A WTRU may monitor (E)PDCCH with CE-C-RNTI in a first set of downlink subframes and the WTRU may monitor (E)PDCCH with C-RNTI in a second set of downlink subframes which may be non- overlapping with the first set of downlink subframes. Alternatively, a WTRU may monitor (E)PDCCH with both CE-C-RNTI and C-RNTI in a subset of downlink subframes, wherein the search space for C-RNTI and CE-C-RNTI may be determined by at least one of following: (i) the same search space may be used, thus a WTRU may decode a (E)PDCCH candidate and check with both C- RNTI and CE-C-RNTI; (ii) a different search space may be used, wherein the search space for each RNTI may be determined with a hashing function which may use the RNTI as an input; and/or (iii) the search space for CE-C-RNTI may be predetermined while the search space for C-RNTI may be determined by a hashing function.

[0160] The subset of subframes for which the WTRU may (or may need to) monitor (E)PDCCH with CE-C-RNTI may be determined by (i) higher layer signaling; (ii) dynamic indication from a DCI; and/or (iii)a predefined set.

[0161] A WTRU may (or may need to) monitor (E)PDCCH with CE-C-

RNTI associated with one direction (e.g., uplink) and (E)PDCCH with C-RNTI associated with the other direction (e.g., downlink). Alternatively, a WTRU may (or may need to) monitor (E)PDCCH with both CE-C-RNTI and C-RNTI associated with one direction (e.g., downlink), while the WTRU may (or may need to) monitor (E)PDCCH with either C-RNTI or CE-C-RNTI associated with the other direction (e.g., uplink).

[0162] In another example, a modified DCI format may be used for the fallback transmission. For instance, DCI format 1A may be modified for fallback transmission for the mode adaptation between normal mode and CE mode.

[0163] The DCI format 1A may be used if a WTRU is in normal mode and not supporting mode adaptation between normal mode and CE mode. The modified DCI format 1A may be used if a WTRU is supporting mode adaptation between normal mode and CE mode.

[0164] The modified DCI format 1A payload size may be the same as for

DCI format 1A. A WTRU may differentiate DCI format 1A and modified DCI format 1A by using a flag (e.g., a bit) within the DCI format. A WTRU may differentiate DCI format 1A and modified DCI format 1A by RNTI, subframe, search space, or time/frequency resource. For example, the DCI format 1A may be monitored with C-RNTI while the modified DCI format 1A may be monitored with coverage enhancement C-RNTI (CE- C-RNTI).

[0165] For the modified DCI format 1A, one or more bits within the DCI format 1A payload may be reused to indicate a number of repetitions for PDSCH or PUSCH. Alternatively, a single bit within the DCI format 1A payload may be reused to indicate the mode of operation between normal mode and CE mode.

[0166] The search space for DCI format 1A and modified DCI format 1A may be different. For example, search space for DCI format 1A may be defined in PDCCH region while the search space for modified DCI format 1A may be located in EPDCCH region, where the PDCCH region and the EPDCCH region may be non-overlapped in time and frequency. One DCI format located in PDCCH region and the other DCI format located in EPDCCH region may be used.

[0167] The aggregation level may be different between DCI format 1A and modified DCI format 1A. For example, the DCI format 1A may be monitored by using the aggregation levels, e.g., {1, 2, 4, 8}, in a subframe while the modified DCI format 1A may be monitored with a set of larger aggregation levels, e.g., {4, 8, 16, 32}, or vice versa. Alternatively, the DCI format 1A may be monitored with a set of aggregation levels, e.g., {1, 2, 4, 8}, while the modified DCI format 1A may be monitored in a subset of the aggregation levels, e.g., {4, 8}, or vice versa.

[0168] A WTRU may operate (e.g,. in CE mode) with a decoupled UL/DL where the cell from which the WTRU may receive DL and the cell to which WTRU may transmit UL may be different. A moving WTRU in this scenario may experience changes to coverage differently for the DL and UL.

[0169] A WTRU may be commanded to handover its DL or UL to a target cell in separate commands when for example the WTRU moves in decoupled UL/DL mode (e.g., decoupled CE mode).

[0170] The term eNB/cell may be used to represent eNB and/or cell. The eNB/cell currently serving the DL of the WTRU may be referred to as source DL eNB/cell. The eNB/cell currently serving the UL may be referred to as source UL eNB/cell. The eNB/cell which is targeted for DL or UL handover may be referred to as target DL eNB/cell or target UL eNB/cell respectively.

[0171] Figure 11 is an example flow diagram of a handover for a WTRU with decoupled UL/DL. A WTRU may include or use a decoupled UL 1101(a) and DL 1101(b). A WTRU may be used herein to represent one or both of the UL 1101(a) and DL 1101(b) functions which may or may not be implemented as separate functions within the WTRU. The separation shown is for non- limiting exemplary purposes. The eNBs which are the serving UL and DL eNBs before handover are referred to as the source UL and DL eNBs. In this example, the serving UL eNB does not change.

[0172] The WTRU may communicate in the UL 1105 with (e.g., transmit

UL transmissions to) a source UL eNB 1102 and communicate in the DL 1107 with (e.g., receive DL transmissions from) a source DL eNB 1103. The source UL eNB 1102 and source DL eNB 1103 may communicate with each other 1106. The WTRU may perform measurements 1108 on the DL signals from the cells of the source eNBs 1102, 1103 and one or more potential target cells of one or more potential target eNBs 1104. The WTRU may transmit a measurement report 1109 to the source UL eNB 1102. Based on this measurement report, a handover decision 1110 may be made by the source UL eNB 1102 or the source DL eNB 1103. The source UL eNB 1102 may forward the measurement report and other information to the source DL eNB 1103 to support the handover decision process. Alternatively, the source UL eNB 1102 may make the handover decision 1110 and send it to the source DL eNB 1103. The handover decision 1110 may include a selection of a target DL cell of a target DL eNB 1104. The source DL eNB 1103 may perform handover preparation 1111 with the target DL eNB 1104 which may include a handover request by the source DL eNB 1103, information exchange (e.g., transfer of WTRU related information by the source DL eNB 1103 to the target DL eNB 1104), admission control by the target DL eNB 1104, and a handover request acceptance (e.g., acknowledgment) or rejection, and the like. If the request is accepted, the source DL eNB 1103 may send a handover command 1112 to the WTRU and the WTRU may perform DL handover 1113 which may include synchronization with the target cell. If successful, the WTRU may send a handover complete message 1114 to the source UL eNB 1102. The source UL eNB 1102 may communicate 1115 with the target DL eNB 1104 to inform it of the success and the target DL eNB 1104 may communicate with the source DL eNB 1103 to inform it that the handover is completed. The target DL eNB 1104 may now communicate in the DL 1117 with the WTRU.

[0173] In the example shown in Figure 11, the source UL and source DL cells as well as the target DL cell belong to different eNBs. This is for example purpose only. One or more cells may belong to the same eNB. If the source UL and source DL cells belong to the same eNB, for example if one or both are remote radio heads of an eNB, the communication 1106 shown between the eNBs may be internal or unnecessary. Similarly, depending on which cells belong to which eNB, inter-eNB communication 1115 and/or 1116 may be internal or unnecessary.

[0174] In an embodiment, a WTRU may be commanded by the source eNB serving the DL of the WTRU to perform a DL only handover to a target cell. The decision for an eNB to trigger the DL handover may be based on a measurement report from the WTRU, which may include RSRP and/or RSRQ measurements of neighboring cells. The source eNB for DL only handover may perform handover preparations with the target eNB, which may include information exchange. For example, the source eNB (e.g., for DL) may provide WTRU information to the target eNB (for DL). An eNB other than the source eNB for DL may or may also send information to or exchange information with the target eNB for DL. [0175] The information which may be sent to or received from the target eNB for DL may include WTRU context related information, for example, C- RNTI, WTRU security context.

[0176] The information which may be sent to or received from the target eNB for DL may include DL physical and radio bearer resource allocations, for example, currently configured radio bearers and E-RABs in the DL direction for the WTRU and possibly, related QoS parameters.

[0177] The information which may be sent to or received from the target eNB for DL may include DL CE mode and level information, for example, the currently supported DL CE mode and level of the WTRU, or possibly the expected DL CE mode and level on the target cell.

[0178] The information which may be sent to or received from the target eNB for DL may include measurement results, for example, WTRU reported RSRP and/or RSRQ measurement results of the current DL serving cell and/or measurements of the target and neighbor cell.

[0179] The information which may be sent to or received from the target eNB for DL may include information regarding the eNB which is currently supporting the UL of the WTRU, e.g., the eNB ID. For example, the eNB currently serving the UL of the WTRU may be the source eNB, or possibly the target eNB. The former may be a DL only handover scenario where the CE mode WTRU may transition from a coupled UL/DL to a decoupled scenario, whereas the latter may be a DL only handover scenario where the WTRU may transition from a decoupled to a coupled UL/DL CE mode scenario.

[0180] As part of the handover preparation, the target eNB for DL handover may perform call admission based on one or more of: requested DL resources, the eNB's ability to support DL only handover or decoupled operation, the need for CE mode support for the WTRU, the CE level needed for the WTRU, and/or the available connectivity to the eNB supporting the UL of the WTRU.

[0181] A call admission decision may be based at least in part on the requested or needed DL resources. The target eNB may or may not be able to support the requested resources. If the target eNB is not able to support the requested resources, the target eNB may deny admission, e.g., reject the handover request.

[0182] A call admission decision may be based at least in part on the eNB capability to support DL only of the decoupled UL/DL (e.g., decoupled UL/DL CE mode) WTRU. The target eNB may or may not support DL only for decoupled WTRUs. If the target eNB does not support the DL only for decoupled WTRUs, the target eNB may deny admission, e.g., reject the handover request.

[0183] A call admission decision may be based at least in part on CE mode support and level for DL. The target eNB may not support CE mode WTRUs, or the CE level needed by the WTRU, or may not have the resources to support CE mode WTRUs. If the target eNB is not able to support the CE mode, the CE level, or does not have available resources for a CE mode WTRU, the target eNB may deny admission, e.g., reject the handover request.

[0184] A call admission decision may be based at least in part on connectivity to the eNB supporting the UL of WTRU. The target DL eNB may or may not have connectivity, e.g., X2 connectivity, or may not have sufficient connectivity, e.g., ideal X2 backhaul connectivity, to the eNB supporting the UL of the decoupled WTRU. If such connectivity is not available or insufficient, the target eNB may deny admission, e.g., reject the handover request.

[0185] An eNB, e.g., the target eNB, may admit the DL of an incoming decoupled mode (e.g., decoupled CE mode) WTRU and may provide the handover command, e.g., RRC reconfiguration with mobilityControlInfo IE, to the source eNB which may be forwarded to the WTRU. In the message, a eNB may include common DL and dedicated physical channel information and admitted and rejected DL radio bearer information.

[0186] As part of the handover preparation, the source eNB may indicate to the current UL serving eNB that the DL serving cell for a WTRU is being handed over to the target cell. For example, the source DL eNB may provide this information to the UL serving eNB upon receiving the handover preparation acknowledge, e.g., X2 Handover Request Acknowledge message, from the target DL serving eNB.

[0187] A WTRU which receives the handover command from the source eNB may detect and synchronize in terms of the DL to the target cell. For example, as part of DL synchronization, a WTRU may detect the PSS/SSS and gain frame and slot level timing with a target cell. A WTRU may not perform CB or CF RA, and may provide the handover completion message, e.g., RRC Reconfiguration Complete message, to the UL supporting cell, possibly by PUSCH. A WTRU may consider at this instance for the DL only handover to have been successfully completed.

[0188] The UL serving eNB may then forward the handover completion message from the WTRU to source DL eNB and/or the target DL eNB to indicate the successful DL handover to the target DL cell.

[0189] In another embodiment, a WTRU may be commanded to perform a UL only handover, directing the UL transmission from the source UL cell to an indicated target UL cell. Both a source DL eNB and/or a source UL eNB may make a decision for UL only handover. A DL serving eNB may trigger a UL only handover to the WTRU based on measurement reports from the WTRU. A source UL eNB may trigger a UL only handover based on measurement reports received from the WTRU and/or possibly based on its measured UL quality as received from the UL transmissions of the WTRU. For example, UL quality may be derived from metrics such as PUCCH and/or PUSCH BLER, UL RS received signal strength, received SRS quality. A UL eNB, based on its own decision to handover the UL of the WTRU or based on an indication from the DL eNB for a UL only handover may initiate the handover preparation with a target UL eNB and cell. For example, X2 or Si may be used to initiate the handover preparation procedure. Similar to DL only handover, a source UL eNB may provide information concerning the WTRU, target UL cell ID, allocated UL resources and UL security context to the target UL eNB. The target UL eNB may then respond with a message indicating whether the WTRU has been accepted or not as part of the call admission process and also provide the handover command which may be forwarded to the WTRU. Similar to DL only handover, the target UL eNB may include information regarding allocated UL resources, dedicated RACH information, allocated CE mode and level in the handover command to the WTRU. Upon completion of the handover preparation, the target UL eNB may provide the current DL serving eNB with the received handover command for DL transmission to the WTRU, along with the indication of the target UL eNB.

[0190] A WTRU may execute the handover command to the target UL cell by performing a CF RA based on the received dedicated RA (e.g., PRACH) information in the handover command for the purpose of UL synchronization. A WTRU may, based on successful a RA procedure, provide a message to the target UL cell indicating the completion of the handover. The target UL cell may forward this message to the source UL eNB and DL eNB to complete the handover procedure.

[0191] As an example, it may be possible for source UL eNB to handover the UL only of a decoupled (e.g., decoupled CE) mode WTRU to the eNB which currently supports the DL as the target UL eNB, such that WTRU (e.g., CE mode WTRU) operating in decoupled UL/DL mode may operate in a coupled UL/DL mode. In this the DL eNB and target UL eNB are the same, the handover procedure may be completed with fewer message interactions between the eNBs.

[0192] A WTRU may also execute the above UL and DL only handovers together in a single handover procedure. For example, a WTRU may be commanded by the source DL eNB to handover both UL and DL to the target cell. In this case, the source DL eNB may provide a single handover command, signaled by a target eNB, to a WTRU and may contain handover information for both UL and DL resources.

[0193] In another example, a WTRU may execute the UL and DL only handovers together to separate DL and UL supporting target cells. In this case, a WTRU may complete the DL only handover to the target DL cell, and then complete the UL only handover to target UL cell, and upon completion of both provide a handover completion message to the target UL cell, indicating completion of one or both DL and UL only handovers.

[0194] Although features and elements are described above in particular combinations, one of ordinary skill in the art will appreciate that each feature or element may be used alone or in combination with any of the other features and elements. In addition, the embodiments described herein may be implemented in a computer program, software, or firmware incorporated in a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals, (transmitted over wired or wireless connections), and computer-readable storage media. Examples of computer-readable storage media include, but are not limited to, a read only memory (ROM), a random access memory (RAM), a register, a cache memory, a semiconductor memory device, a magnetic media, (e.g., an internal hard disc or a removable disc), a magneto-optical media, and an optical media such as a compact disc (CD) or a digital versatile disc (DVD). A processor in association with software may be used to implement a radio frequency transceiver for use in a WTRU, WTRU, terminal, base station, Node-B, eNB, HNB, HeNB, AP, RNC, wireless router or any host computer.