This application claims the benefit of U.S. Provisional Application No. 61/256,645 entitled "Optimized Backhaul Communications for a Relay-Enhanced Packet-Based Wireless Communication System," filed on October 30, 2009, which is incorporated herein by reference.

TECHNICAL FIELD

The present invention is directed, in general, to communication systems and, more particularly, to a system and method for providing the use relay nodes communicating with user equipment, base stations, or mobile transceiver devices in a packet based communication system that includes Voice over Internet Protocol ("VoIP") packet support and frequency division duplex ("FDD") or time division duplex ("TDD") signaling using an over the air interface between communication devices, while allowing for efficient use, simple implementation and conservation of system resources.

BACKGROUND As wireless communication systems such as cellular telephone, satellite, and microwave communication systems become widely deployed and continue to attract a growing number of users, there is a pressing need to accommodate a large and variable number of communication subsystems transmitting a growing volume of data with a fixed resource such as a fixed channel bandwidth accommodating a fixed data packet size. Traditional communication system designs employing a fixed resource (e.g., a fixed data rate for each user) have become challenged to provide high, but flexible, data transmission rates in view of the rapidly growing customer base.

The third generation partnership project long term evolution ("3GPP LTE") is the name generally used to describe an ongoing effort across the industry to improve the universal mobile telecommunications system ("UMTS") for mobile communications. The improvements are being made to cope with continuing new requirements and the growing base of users. Goals of this broadly based project include improving communication efficiency, lowering costs, improving services, making use of new spectrum opportunities, and achieving better integration with other open standards and backwards compatibility with some existing infrastructure that is compliant with earlier standards. The project envisions a packet switched communications environment with support for such services as VoIP. The 3GPP LTE project is not itself a standard-generating effort, but will result in new recommendations for standards for the UMTS. Recently, the project moved to planning the next generation standards, sometimes referred to as LTE-Advanced, IMT-Advanced, or sometimes casually as "4G".

LTE systems may include a centralized or decentralized entity for control information. In UTRAN operation, each radio network controller ("RNC") may be connected to multiple base stations (Node Bs or eNBs) which are the UMTS counterparts to Global System for Mobile Communications ("GSM") base stations. In E-UTRAN systems, the e-NB may be, or is, connected directly to the access gateway ("aGW," sometimes referred to as the services gateway "sGW"). Each Node B may be in radio contact with multiple User Equipment ("UE")

(generally, user equipment including mobile transceivers or cell phones, although other devices such as fixed cellular phones, mobile web browsers, laptops, PDAs, MP3 players, gaming devices with transceivers may also be UEs) via the radio Uu interface.

The wireless communication systems as described herein are applicable to, for instance, 3GPP LTE compatible wireless communication systems and of interest is an aspect of LTE referred to as "evolved UMTS Terrestrial Radio Access Network," or E-UTRAN. In general, E- UTRAN resources are assigned more or less temporarily by the network to one or more UEs by use of allocation tables, or more generally by use of a downlink resource assignment channel or physical downlink control channel (PDCCH). LTE is a packet-based system and, therefore, there may not be a dedicated connection reserved for communication between a UE and the network. Users are generally scheduled on a shared channel every transmission time interval ("TTI") by a Node B or an evolved Node B (e-NB). A Node B or an e-NB controls the communications between user equipment terminals in a cell served by the Node B or e-NB. In general, one Node B or e-Node B serves each cell. A Node B may be sometimes referred to as a "base station." Resources needed for data transfer are assigned either as one time assignments or in a persistent/semi-static way. The LTE, also referred to as 3.9G, generally supports a large number of users per cell with quasi-instantaneous access to radio resources in the active state. It is a design requirement that at least 200 users per cell should be supported in the active state for spectrum allocations up to 5 megahertz (MHz), and at least 400 users for a higher spectrum allocation.

In order to facilitate scheduling on the shared channel, the e-NB transmits a resource allocation to a particular UE in a downlink-shared channel ("PDCCH") to the UE. The allocation information may be related to both uplink and downlink channels. The allocation information may include information about which resource blocks in the frequency domain are allocated to the scheduled user(s), the modulation and coding schemes to use, what the size of the transport block is, and the like. The lowest level of communication in the e-UTRAN system, Level 1, is implemented by the Physical Layer ("PHY") in the UE and in the e-NB and the PHY performs the physical transport of the packets between them over the air interface using radio frequency signals. In order to ensure a transmitted packet was received, an automatic retransmit request ("ARQ") and a hybrid automatic retransmit request ("HARQ") approach is provided. Thus whenever the UE receives packets through one of several downlink channels, including command channels and shared channels, the UE performs a communications error check on the received packets, typically a Cyclic Redundancy Check ("CRC"), and in a later sub frame following the reception of the packets, transmits a response on the uplink to the e-Node B or base station. The response is either an Acknowledge ("ACK") or a Not Acknowledged ("NACK") message. If the response is an NACK, the e-Node B automatically retransmits the packets in a later sub frame on the downlink ("DL"). In the same manner, any uplink ("UL") transmission from the UE to the e- Node B is responded to, at a specific sub frame later in time, by a NACK/ ACK message on the DL channel to complete the HARQ. In this manner, the packet communications system remains robust with a low latency time and fast turnaround time.

E-UTRAN networks may provide VoIP support. To provide this support, the UE may transmit to the e-Node B over the air interface packets at a predetermined timing interval, so that the voice signals that are eventually formed from these VoIP packets are free of jitter and noise that would otherwise result. Semi-persistent scheduling ("SPS") may be used to allocate (UL physical resource blocks ("PRBs") to ensure the VoIP packets are delivered at appropriate intervals to maintain quality of service and reduce control signaling cost. The need to provide UL packets from the UE to the eNB has certain impacts on other aspects of the operations of the physical layer, including retransmit requests and synchronous HARQ processes that result from previous UL packet transmissions that were not received by the eNB. A UE may have a transmission conflict between a scheduled UL resource such as an initial transmission for a VoIP packet and a need to service a HARQ retransmission request packet at the appropriate time.

Recently proposals are being made to increase the capacity, efficiency, and quality of service in the next generation networks, LTE-Advanced. One of these proposals includes the use of relay, and relay nodes ("RN"). The forwarding procedures of the relay node can be performed at different levels in the protocol stack, for example LI, L2 and L3. Currently the primary focus is on a relay node at level L3, which features "self backhauling." Such a relay node is configured essentially as another eNB, however, it also capable of UL communications with a host eNB. For the discussions herein, the relay nodes are assumed to be L3 relay nodes. A relay node can be placed to extend or improve the cell service of an eNB. The RN is connected to the eNB by a wireless connection known as the backhaul link. The RN also has UEs that are "attached" to it. For example applications, RNs may be placed in urban areas where shadowing and reflections occur, in high traffic areas, in remote areas where another eNB is not available, and otherwise placed to extend or improve cell coverage at cell boundaries.

For LTE- Advanced, support of wider bandwidth is an important consideration. To provide this, carrier aggregation schemes have been proposed. This approach has advantages in providing backward capability with LTE compliant UEs, and, higher peak throughput to LTE UEs, simultaneously.

A continuing need thus exists for a system, methods and circuitry to implement support for the use of relay in advanced cellular networks, without the need for additional

communications from higher layers or burdening other radio resources.

SUMMARY OF THE INVENTION

These and other problems are generally solved or circumvented, and technical advantages are generally achieved, by advantageous embodiments of the present invention which include an apparatus and methods according to an embodiment for providing an RN interface that efficiently performs backhaul communications and UE communications to the RN, while supporting various scheduled services on a radio communications interface with retransmit requests.

According to an illustrative embodiment, a communication network node such as an RN is provided. Aggregation of component carriers is used. At least one of the aggregated component carriers is split in to two sub-bands. One sub-band is used to form the wireless backhaul connection between the RN and its assigned eNB. The other is used to provide a direct link between the eNB and other UEs. By splitting the carrier into sub-bands, and by using the aggregated band (for example, C2) with original band (for example, CI) in a manner where they are spatially separated, efficient communication between the eNB, the RN, and its attached UEs, and with minimal relay delays and interferences problems, is achieved.

According to another illustrative embodiment, a communication base station such as an eNB is provided that may determine the sub-band assigned to the backhaul bandwidth for a RN. The UEs attached to the eNB are then assigned other component carriers based on the unique range of Identifiers ("IDs") of the UEs in an initialization process. In this manner the UEs are not using the bandwidth reserved for the RNs backhaul messages. Messages between the eNB and the RN may then be simultaneously transmitted with messages between the RN and its attached UEs, as the messages are using different frequency resources, and thus no delay is imposed on the message traffic by the use of the RN. In this manner the required periodicity for support of retransmit requests, for example, is provided while adding the capabilities of a relay node.

According to another illustrative embodiment, a communication network node such as a

RN is provided and the embodiment described above uses an aggregated CC, which is non- backward compatible with Rel-8. A backhaul bandwidth frequency is assigned to the RN by a corresponding eNB, using a master information block ("MIB") message. The UEs attached to the eNB are also configured to avoid the use of the backhaul bandwidth ("BW") by the MIB message. In this manner collisions are avoided and the RN may communicate on the backhaul interface while simultaneously communicating over an access link to the UEs attached to the RN; as these communications are separated in frequency resources. In one exemplary embodiment, a method is provided comprising providing a

communication network node configured to receive and transmit packet signals over a radio frequency air interface; receiving an indication of a primary carrier; receiving an indication of a aggregate carrier sub-band; communicating backhaul messages over the air interface using the aggregate carrier sub-band; and communicating access messages to a second device using the primary carrier over the air interface. In another exemplary embodiment, the above method is provided and the backhaul messages are transceived to an enhanced Node B base station. In another exemplary embodiment, the above method is provided and the access messages are transceived to at least one user equipment using the primary carrier. In another exemplary embodiment, the above method is performed and the communication network node is a relay node that forwards messages from an eNB to one or more user equipments. In another embodiment, the above described method is performed and the user equipments are LTE Release 8 compliant. In yet another method embodiment, the user equipment are LTE- Advanced compliant.

In another exemplary embodiment, the method comprises providing a user equipment configured to receive and transmit packet signals over a radio frequency air interface; receiving a master interface block message having a configuration field indicating an component carrier sub- band that is reserved; and attaching to a relay node for over the air communications using a primary carrier different from the aggregate carrier sub band.

In another embodiment, a relay node apparatus is provided comprising a programmable processor for transceiving radio frequency signals over an air interface. A computer readable medium is provided comprising instructions that, when performed by the programmable processor, cause the programmable processor to perform the steps of receiving an indication of a aggregate carrier sub-band; receiving an indication of a primary carrier; communicating backhaul messages over the air interface using the aggregate carrier sub-band; and

communicating access messages to a second device using the primary carrier over the air interface. In another exemplary embodiment, the computer readable medium is provided further comprising instructions that when executed cause the programmable processor to perform transceiving backhaul messages to an enhanced Node B base station. In another exemplary embodiment, the above method is provided and the computer readable medium further comprises instructions that, when executed, cause the programmable processor to perform transceiving access messages to at least one user equipment using the primary carrier. In another exemplary embodiment, the above method is performed and the communication network node having a programmable processor is a relay node programmably configured to forward messages from an eNB to one or more user equipments. In another embodiment, the above described method is performed and the user equipments are LTE Release 8 compliant. In yet another method embodiment, the user equipment are LTE- Advanced compliant.

The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures or processes for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in claims that may be presented.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

FIGURE 1 illustrates a system level diagram of a radio frequency interface

communication system including a wireless communication system;

FIGURE 2 illustrates a simplified system level diagram of an example communication element of a communication system;

FIGURE 3 illustrates a block diagram of an embodiment of a UE and an eNB with service layers;

FIGURE 4 illustrates the type 1 transport frame used in the e-UTRAN system to physically communicate packets to and from, for example, an e-Node B device using FDD;

FIGURE 5 illustrates the type 2 transport frame used in the e-UTRAN system to physically communicate packets to and from, for example, an e-Node B device using TDD;

FIGURE 6 depicts examples of component carriers that are contiguous and noncontiguous in the frequency domain;

FIGURE 7 illustrates an example of a communications system using relay in a conventional approach;

FIGURE 8 illustrates an example of a communications system using relay in a split band, aggregate component carrier approach according to exemplary embodiments of the present invention;

FIGURE 9 illustrates two frequency diagrams for carriers at an eNB and RN using an embodiment of the present invention;

FIGURE 10 illustrates the use of physical resource blocks in a split band component carrier at an e-Node B device using an exemplary embodiment of the present invention;

FIGURE 11 illustrates uplink and downlink communications in a system using embodiments of the present invention; and

FIGURE 12 illustrates a master information block used to configure devices in an embodiment of the present invention. DETAILED DESCRIPTION

The illustrative embodiments described are directed to an application for the use of relay in an LTE- Advanced system with FDD or TDD signaling. However, the embodiments are not limited to this example application and the use of the embodiments in other communications systems to provide an enhanced relay function and relay nodes with efficient backhaul communications.

Referring initially to FIGURE 1, illustrated is a system level diagram of a radio frequency interface communication system 10 including a wireless communication system that provides an environment for the application of the principles of the present invention. The wireless communication system may be configured to provide features included in the evolved UMTS terrestrial radio access network ("e-UTRAN") universal mobile telecommunications services. Mobile management entities ("MMEs") and user plane entities ("UPEs") labeled MME/UPEO and MME/UPE1 provide control functionality for one or more e-UTRAN node Bs (designated "eNB," an "evolved node B," also commonly referred to as a "base station") labeled eNBO, eNB l, eNB2, via an SI interface or communication link. The eNBs communicate via an X2 interface or communication link. The various communication links are typically fiber, microwave, or other high-frequency metallic communication paths such as coaxial links, or combinations thereof.

The eNBs communicate over an air interface with user equipment (designated "UE") labeled UE0, UE1, which are typically a mobile transceiver carried by a user. Alternatively the user equipment may be a mobile web browser, text messaging appliance, a laptop with a mobile PC modem, or other user device configured for cellular or mobile services. Thus,

communication links (designated "Uu" communication links) coupling the base stations to the user equipment are air links employing a wireless communication signal. For example the devices may communicate using a known signaling approach such as a 1.8 GHz orthogonal frequency division multiplex ("OFDM") signal. Other radio frequency signals may be used.

The eNBs may host functions such as radio resource management (e.g. , internet protocol ("IP"), header compression and encryption of user data streams, ciphering of user data streams, radio bearer control, radio admission control, connection mobility control, dynamic allocation of resources to user equipment in both the uplink and the downlink), selection of a mobility management entity at the user equipment attachment, routing of user plane data towards the user plane entity, scheduling and transmission of paging messages (originated from the mobility management entity), scheduling and transmission of broadcast information (originated from the mobility management entity or operations and maintenance), and measurement and reporting configuration for mobility and scheduling. The MME/UPEs may host functions such as distribution of paging messages to the base stations, security control, terminating U-plane packets for paging reasons, switching of U-plane for support of the user equipment mobility, idle state mobility control, and system architecture evolution bearer control. The UEs receive an allocation of a group of information blocks labeled physical resource blocks ("PRBs") from the eNBs.

FIGURE 2 illustrates a simplified system level diagram of an example communication element of a communication system 20 that provides an environment and structure for application of the principles of the present invention. The communication element 21 may represent, without limitation, an apparatus including an eNB, UE such as a terminal or mobile station, a relay node, or the like. The communication element 21 includes, at least, a processor 23, memory 27 that stores programs and data of a temporary or more permanent nature, an antenna, and a radio frequency transceiver 25 coupled to the antenna and the processor 23 for bidirectional wireless communication. Other functions may also be provided. The

communication element 21 may provide point-to-point and/or point-to-multipoint

communication services.

The communication element 21, such as an eNB in a cellular network, may be coupled to a communication network element, such as a network control element 28 of a public switched telecommunication network ("PSTN")- The network control element 28 may, in turn, be formed with a processor 23, memory 27, and other electronic elements (not shown). Access to the PSTN may be provided using fiber optic, coaxial, twisted pair, microwave communication, or similar communication links coupled to an appropriate link-terminating element. A communication element 21 formed as a UE is generally a self-contained device intended to be carried by an end user and communicating over an air interface to other elements in the network

The processor 23 in the communication element 21, which may be implemented with one or a plurality of processing devices, performs functions associated with its operation including, without limitation, encoding and decoding of individual bits forming a communication message, formatting of information, and overall control of the communication element, including processes related to management of resources. Exemplary functions related to management of resources include, without limitation, hardware installation, traffic management, performance data analysis, tracking of end users and mobile stations, configuration management, end user administration, management of the mobile station, management of tariffs, subscriptions, and billing, and the like. The execution of all or portions of particular functions or processes related to management of resources may be performed in equipment separate from and/or coupled to the communication element 21 , with the results of such functions or processes communicated for execution to the communication element 21. The processor 23 of the communication element 21 may be of any type suitable to the local application environment, and may include one or more of general-purpose computers, special-purpose computers, microprocessors, digital signal processors ("DSPs"), and processors based on a multi-core processor architecture, as non- limiting examples.

The transceiver 25 of the communication element 21 modulates information onto a carrier waveform for transmission by the communication element 21 via the antenna to another communication element. The transceiver 25 demodulates information received via the antenna for further processing by other communication elements.

The memory 27 of the communication element 21, as introduced above, may be of any type suitable to the local application environment, and may be implemented using any suitable volatile or nonvolatile data storage technology, such as a semiconductor-based memory device, a magnetic memory device and system, an optical memory device and system, fixed memory, and removable memory. The programs stored in the memory 27 may include program instructions that, when executed by an associated processor, enable the communication element 21 to perform tasks as described herein. Exemplary embodiments of the system, subsystems, and modules as described herein may be implemented, at least in part, by computer software executable by processors of, for instance, the mobile station and the base station, or by hardware, or by combinations thereof. Other programming may be used such as firmware and/or state machines. As will become more apparent, systems, subsystems and modules may be embodied in the communication element 21 as illustrated and described above.

FIGURE 3 depicts a block diagram of an embodiment of a UE 31 and an eNB 33 constructed according to the principles of the present invention and coupled to an Mobile

Management Entity ("MME") 35. The UE 31 and the eNB 33 each include a variety of layers and subsystems: the physical layer ("PHY") subsystem, a medium access control layer ("MAC") subsystem, a radio link control layer ("RLC") subsystem, a packet data convergence protocol layer ("PDCP") subsystem, and a radio resource control layer ("RRC") subsystem. Additionally, the user equipment and the mobile management entity ("MME") include a non-access stratum ("NAS") subsystem.

The physical layer subsystem supports the physical transport of packets over the LTE air interface and provides, as non-limiting examples, cyclic redundancy check ("CRC") insertion (e.g. , a 24 bit CRC is a baseline for physical downlink shared channel ("PDSCH"), channel coding (e.g. , turbo coding based on quadratic polynomial permutation ("QPP") inner interleaving with trellis termination), physical layer hybrid-automatic repeat or retransmit request ("HARQ") processing, and channel interleaving. The physical layer subsystem also performs scrambling such as transport-channel specific scrambling on a downlink-shared channel ("DL-SCH"), broadcast channel ("BCH") and paging channel ("PCH"), as well as common multicast channel ("MCH") scrambling for all cells involved in a specific multimedia broadcast multicast service single frequency network ("MBSFN") transmission. The physical layer subsystem also performs signal modulation such as quadrature phase shift keying ("QPSK"), 16 quadrature amplitude modulation ("QAM") and 64 QAM, layer mapping and pre-coding, and mapping to assigned resources and antenna ports. The media access layer or MAC performs the HARQ functionality and other important functions between the logical transport layer, or Level 2, and the physical transport layer, or Level 1.

Each layer is implemented in the system and may be implemented in a variety of ways. A layer such as the PHY in the UE may be implemented using hardware, software,

programmable hardware, firmware, or a combination of these as is known in the art.

Programmable devices such as digital signal processors ("DSPs"), reduced instruction set computer ("RISC"), complex instruction set computer ("CISC"), microprocessors,

microcontrollers, and the like may be used to perform the functions of a layer. Reusable design cores or macros as are provided by vendors as application specific integrated circuit ("ASIC") library functions, for example, may be created to provide some or all of the functions and these may be qualified with various semiconductor foundry providers to make design of new UEs, or e-Node B implementations, faster and easier to perform in the design and commercial production of new devices.

The e-UTRAN system architecture has several significant features that impact timing in the system. A transmission time interval ("TTI") is defined and users (e.g. UE or mobile transceivers) are scheduled on a shared channel every TTI. The majority of UE or mobile transceivers considered in the implementation of the e-UTRAN are full duplex devices. These UEs can therefore receive control and data allocations and packets from the e-NODE B or base station they are connected to in any sub frame interval in which they are active. The UE detects when resources are allocated to it in the allocation messages on the physical downlink control channel ("PDCCH"). When downlink resources are allocated to a UE, the UE can determine that data or other packets are going to be transmitted towards it in the present frame or coming frames. Also, the UE may have uplink resources allocated to it. In this case the UE will be expected to transmit towards the e-Node B in coming frames on the uplink based on the allocated UL resources.

Additional timing related services are present in the environment. The e-UTRAN communications environment supports VoIP communication. The use of VoIP packets creates another cyclic pattern within the system. A typical cycle for VoIP would be 20 milliseconds although 40 milliseconds, 60 milliseconds and 80 milliseconds may also be used in case packet bundling is used. Twenty milliseconds as VoIP interval will be used as a non-limiting default example for VoIP packets throughout the rest of this specification text. Further, the e-UTRAN communications system provides automatic retransmission request ("ARQ") and hybrid automatic retransmission request ("HARQ") support. The HARQ is supported by the UE and this support has two different dimensions. In the downlink direction, asynchronous HARQ are supported. However, the uplink or UL channel is a different standard channel that uses single carrier Frequency Division Multiple Access ("FDMA") or ("SC-FDMA) and as currently provided, requires a synchronous HARQ. That is, in the uplink direction, after a packet is transmitted to the eNB, an ACK/NACK (acknowledged/not acknowledged) response is transmitted by the eNB towards the UE a definite time period later, after which the UE, in case NACK was received, will retransmit the packet in UL direction in a given sub frame after a predetermined delay.

The e-UTRAN specifications support air interface signaling using both frequency division duplex ("FDD"), where uplink (signaling from the UE to the eNB) and downlink (signaling from the eNB towards the UE) can occur at the same time but are spaced apart at different frequencies; and time division duplex ("TDD"), where the UL and DL frames are communicated on the same carrier but spaced apart in time. For particular interest to the embodiments of the present invention are the frame structures of TDD radio frames. The frame structures have been selected so that TDD and FDD services may be supported in the same environment and dual-mode devices may be easily implemented. The selection of the FDD or TDD services may depend on the type of data, whether the data transmission is asymmetric (for example, internet browsing tends to be very heavy on the downlink, while voice may be more or less symmetric on both downlink and uplink) the environment, and other parameters, there are advantages and disadvantages to each that are known to those skilled in the art.

The technical specifications ("TS") document entitled "3GPP TS 36.300" version 8.5.0 (2008-05) available from the website www.3gpp.org provides in part the specifications for the physical interfaces for the E-UTRAN networks. The technical report ("TR") document entitled

"3GPP TR 25.913 V8.0.0 ₍ 2oos-i2), "3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Requirements for Evolved UTRA (E-UTRA) and Evolved UTRAN (E-UTRAN) (Release 8);" describes the capabilities and requirements of UE and eNBs that are LTE devices, sometimes called "Release 8" devices.

Figure 4 depicts, in very simple form, the type 1 format transport frame 40 used in the e- UTRAN system to physically communicate packets to and from, for example, an e-Node B device and one or more UE devices over the air interface using FDD. In Figure 1, the radio frame is defined as having 10 milliseconds duration. The frame consists of 10 subframes, each of 1 millisecond duration, and each divided into two slots, each of 0.5 milliseconds duration, thus there are 20 slots numbered from 0 to 19. Because the FDD transport separates transmission in frequency, no time division between transmitting and receiving is required.

Figure 5 depicts, in very simple form, the type 2 transport frame 41 used in the e- UTRAN system to physically communicate packets to and from, for example, an e-Node B device and one or more UE devices over the air interface using TDD. TS 36.300 v8.5.0 describes the TDD frame in more detail at pages 19-20. A radio frame in the system is presently defined as having a length T _s of 10 milliseconds. The radio frame is further subdivided into 10 sub frames, each having a length T _s of 1 millisecond. Each sub frame is further divided again into two slots; each slot has a length of 0.5 milliseconds as shown in block 43. Note that the subframes numbered 1 and 6, have additional special functions that require certain timing.

The TDD frame 41 further has three special fields that may be varied in length to form a 1 millisecond sub-frame. These special fields are the downlink pilot time slot ("DwPTS"), the guard period ("GP") and the uplink pilot time slot ("UpPTS") (not shown). The TDD frame 41 is the same length (10 milliseconds, which is 2 half-frames, or 10 sub-frames, each having two slots) as the FDD transport frame, making dual mode equipment easier to implement. Because certain subframes have special functions, these may not be easily shifted in time or direction and certain timing periods must be maintained.

Recent proposals for extending the capabilities of LTE systems to LTE- Advanced include the concept of component carrier ("CC") aggregation. Using component carrier aggregation, the bandwidth used by a particular device may be expanded. For example, it is proposed that a carrier aggregation may include from 2-5 aggregate carriers in addition to the original carrier. Figure 6 depicts, in the frequency domain, two cases. In the top portion, line 52 depicts 5, 20 MHz carriers in a contiguous (frequency spacing is contiguous) case. Carriers Cl- C5 are shown with no spacing between them. In the lower portion of Figure 5, line 54 depicts 3, 20 MHz component carriers, with spacing between them - a non-contiguous case. A technical report from the 3GPP, entitled "Further Advancements for E-UTRA Physical Layer Aspects (Release 9)," and numbered 3GPP TR 36.814, available at www.3gpp.org, provides that a terminal may simultaneously receive or transmit one or multiple component carriers, depending on its capabilities.

Further, to enhance the operation of the communications systems particularly at the cell edges farthest from the corresponding eNB, and in difficult environments such as urban areas with building shadows and reflection problems, the use of relay, and relay nodes ("RNs"), is proposed. These relay nodes may be implemented essentially as additional eNBs that communicate with their own attached UEs, and these nodes relay or forward communications to the corresponding eNB, that is, they forward uplink (UL) and downlink (DL) packets to the eNB, or UE, respectively.

In relay, a link between the relay node and a corresponding eNB is called the "backhaul" link; the link between an eNB or an RN and the UE is called the "access" link.

Figure 7 depicts a simple example relay environment with a single relay node, RN1. The communication links between a UE and an eNB or a relay node are called "access" links. The communications links between a relay node and an eNB are called "backhaul" links. In the conventional system approach of Figure 7, a straightforward in-band approach with a single carrier "CI" is used. That is all of the communications links, 51, 53, 57, and 55 are in the same band. Thus the direct access link 51 is in band "CI", as is the backhaul link 53, the access links 57 and 55 between the RN, RN1 and the UEs attached to it, UE2 and UE3.

The eNB can communicate with UE0 and RN1 at the same time, however, the uplink and downlink traffic to RN1 is limited. Essentially, if RN1 is receiving DL traffic on backhaul link 53, it cannot simultaneously receive uplink traffic on access links 55 and 57 at the same time - the same band or carrier is used. This means that the messages must be spaced apart in time, thus there is a relay node delay in the UE-eNB communications path. Further, certain time critical messages may be lost. For example, at a given time following a downlink message from the RN to one of the UEs, UE2 for example, a HARQ acknowledge/not acknowledge (HARQ

ACK/NACK) message must be sent on the uplink. If the RN is receiving backhaul downlink traffic at that time, the ACK/NACK message may be lost. Similarly, support for VoIP packets may impose periodic time constraints on the eNB->UE messages that the use of the relay node RN1 cannot meet by using this conventional approach.

Thus, current approaches that have been presented for relay standards are typically for one carrier component, and, use in-band relay. In these approaches, the backhaul and the access links operate on the same frequency bandwidth and are necessarily separated in time to reduce or prevent in band interference between the two links at the relay node. In these current schemes, the relay node RN may not be able to receive UE transmissions simultaneously with transmitting backhaul communications to the eNB, because the RN works on the same band as the received messages coming in. Various frame structure approaches have been presented to address problems with this in band relay node. These conventional approaches have several

disadvantages; such as: the possible loss of a hybrid automatic retransmission request (HARQ) ACK/NACK message from a UE, which occurs while the RN is receiving backhaul

communications as a downlink from the eNB; the RN is essentially limited to "half duplex" and cannot forward a UE message data packet at the same time it is receiving it, causing a relay node forwarding delay; certain subframes are protected due to signaling defined within a portion of those subframes and cannot be used for backhaul; there may be near-far interference problems due to the single carrier in an in-band solution; and generally the backhaul connection is limited due to the frame and subframe uplink (UL) and downlink (DL) configurations defined for TDD. These limitations result in a backhaul capacity issue, limiting throughput.

Embodiments of the present invention provide novel methods and apparatus for addressing these problems. In the embodiments, an aggregate carrier scheme is used along with a split-band carrier approach to increase the efficiency of the system and overcome the problems of supporting relay that occur when using a conventional approach.

Figure 8 depicts a system implementing an exemplary, non-limiting embodiment of the invention. In Figure 8, eNBl is now directly linked to UEO and UE1, that is, they are shown "camped" on eNBl. Further, RNl is directly linked to UE2 and UE3. RNl has a backhaul link to eNB 1 as before.

However, in this embodiment, a carrier aggregation scheme is used. Instead of all of the access links and the backhaul link being communicated on carrier CI, a second carrier C2 is also used. Further the second carrier C2 is split into two halves, C21, and C22, in the frequency band. Using this approach, the RN can forward data from eNB to RN to UE from one end to the other end of the link using two carrier components.

Now, C22 is a carrier component used only for the backhaul link between the relay node RNl and eNBl. Carrier CI is used for the access links between RNl and its attached UEs, UE2 and UE3, in the macro cell served by RNl. Similarly, the eNB l uses carrier "CI" for the access link to UEO in its cell. However, carrier "C21" is used for the access link between eNB to UE1, in cell. By using the relay exemplary embodiment of Figure 8, the system capacity is improved. This is true because RN1 can receive downlink (DL) communications from the eNB while simultaneously receiving uplink (UL) communications from the UEs (UE2 and UE3 in Figure 8) attached to it. Put another way, RN1 is now capable of "full duplex" operation. In this arrangement, the relay node delay is reduced or eliminated from the communications loop between eNBl and the UEs camped on RN1, UE2 and UE3. Further, in this embodiment, the need for certain timing relationships to be maintained for HARQ ACK/NACK messaging, and for VoIP support, are met. The embodiments of the present invention are applicable to both LTE (Release 8) and LTE-Advanced UEs. The approach has several benefits, including without limitation the ability to handle HARQ ACK/NACK messages without loss, improved backhaul capacity thus improving throughput, improved support for time critical communications such as VoIP packets, and reducing or eliminating RN forwarding data delay. The embodiments may be used advantageously with both FDD and TDD configured devices.

Figure 9 provides additional advantages of the use of the embodiments. As shown in Figure 9, two aggregated component carriers CI and C2 are used. Further, the second carrier C2 is split into two sub-bands C21 and C22. The upper portion of the figure labeled RN shows the carriers used at the relay node, such as RN1 in Figure 8. The lower portion of Figure 9 illustrates the carriers used at the eNB, for example eNB l in Figure 8.

In this non-limiting embodiment, Carrier C2, sub-band C22, is used for the backhaul. In order to further ensure that there is minimal interference between the C2 sub-bands, the sub-band C21 is assigned to a UE that is not attached to RN1, thus these sub-bands are used by devices that are intentionally spatially separated. This spatial separation effectively creates more frequency separation between transmitted and received messages at the RN. The attached UEs in Figure 8, UE2, and UE3, are transmitting to the RN, RN1 at carrier CI frequency, while the backhaul traffic is at carrier C22 frequency, which is spaced from CI by a frequency spacing Af in Figure 9. C22 is actually farther (frequency spacing) from CI than C21, thus additional frequency separation is provided between the backhaul and the direct or access link traffic.

Figure 10 depicts the use of resource blocks in the component carrier C2. In the figure time is the vertical axis and frequency is the horizontal axis, and so the columnar resource blocks show the use of the frequency bandwidth over a period of time. The carrier C2, for example, a 20 MHz component carrier, is split into two sub-bands C21 and C22 and some frequency spacing is provided by assigning only a portion of the resource blocks as "active" RN resource blocks. Note that multiple RNs may use resource blocks in carrier C22, for example, as shown in the Figure 10. Figure 10 depicts, for example that at one eNB a flexible band splitting between the backhaul link and access link is possible. The two sub-bands C21 and C22 are configured to provide eNB-RN and eNB-UE links at one eNB. The eNB can perform transmitting or receiving on the two sub-bands C21 and C22 at the same time, thus there is no need to consider the frequency guard gap between C21 and C22 at the eNB. A dynamic scheduling of the resources for C21 and C22 may be feasible due to system load.

Figure 11 depicts, for an example TDD frame configuration, the use of the carriers CI and C2 (split into sub-bands C21, C22) in an example scenario for a system incorporating the invention. In Figure 11, time is running along the horizontal axis and the subframes are shown labeled as downlink ("D"), switch points ("S"), and uplink ("UL") subframes. The lines are illustrating, for an eNB, a relay node RN, and UEs attached to the RN and eNB, the use of the carriers in certain subframes. Line 101 depicts the eNB subframes on carrier CI. Line 103 depicts the eNB subframes on C2. Line 105 depicts the carrier CI at the relay node RN. Line 107 depicts the carrier C2, sub-band C22 at the relay node RN. Line 109 depicts a UE attached to the RN and using carrier CI. Line 111 depicts a UE attached to the eNB and using carrier CI. Line 113 depicts a UE attached to the eNB on carrier C2, sub-band C21. Each line depicts the TDD subframes for a periodic repeating frame configuration.

At a time labeled "Ul", in the third subframe from the origin, uplink communications are depicted including RN-> eNB backhauling. A short arrow from line 109, the UE attached to the relay node RN on carrier CI and extending to the line 105, the RN subframes at carrier CI, shows an uplink message at that subframe. At the same time, a longer arrow from line 111 extending up to line 101 depicts an uplink message from the UE attached to the eNB on carrier CI, to the eNB on carrier CI. Similarly, a long arrow extending upwards from line 113, the UE attached to the eNB on carrier C21 (carrier 2, sub-band 21) extends to the line 103, showing the subframes at the eNB on carrier C2. Finally a shorter, dashed arrow extending upwards from line 107 to line 103 depicts an uplink message from the relay node RN on carrier C22 to the eNB on carrier 2; this is a backhaul message from the RN up to the eNB. Thus the RN is forwarding an uplink message received from the UE attached to the RN on carrier CI to the eNB on the backhaul link using carrier C22.

At a time Dl, in the 8th subframe from the origin, downlink traffic is depicted including eNB->RN backhaul data. At time Dl, an arrow is shown extending from the line 101, the eNB subframes at carrier CI, to line 111, the subframes for the UE attached to the eNB at carrier CI. Another arrow is shown extending from line 103, the ENB at carrier C2, down to the line 111, the subframes for the UE attached to the eNB at carrier C21. These UEs are directly attached to the eNB, as shown in Figure 8. Also shown in Figure 11 at time Dl is another arrow extending down from line 105, from the relay node RN on carrier CI to the UE attached to the RN on carrier CI, that is, line 109. Finally, backhaul downlink traffic is depicted by the dashed arrow that extends from the eNB on carrier C2 at line 103 to the line 107, the subframes for the RN on carrier C22. Thus, the figure illustrates that the RN can forward a downlink message received from the eNB on carrier C22 to the UE attached to the RN on carrier CI, using the two component carriers to receive and transmit at the same time.

Note that since the RN is forwarding data in the same subframe as it is receiving, the delay in the earlier approaches is minimized. Also, HARQ or control information which results in a reserved subframe will be kept, there is no collision as the backhaul and access links are on different carriers, so the RN can maintain the timing needed for these signals. Essentially, by using the embodiments of the present invention, the capacity of the RN is doubled in terms of network performance.

The embodiments may be applied to FDD as well. The split carrier band may be used by reserving half of the aggregated band for backhaul transmission and the other half of the band may be used for eNB->attached UE access link usage.

Implementing the methods of the embodiments shown may be done in several ways. The use of the methods may be done in a backwards compatible manner, so that LTE UEs that are "Release 8" compatible may operate properly with the RNs and eNBs that implement embodiments of the invention. The eNB can assign carrier bandwidth to the UEs at initialization in a manner to separate them from the carrier assigned to the backhaul link, for example carrier 2 sub-band C22 as shown above. Of course the use of carrier C2 is not limiting, the proposals for LTE- Advanced contemplate aggregation of up to 5 component carriers and thus a different carrier, for example C3, could be split into two sub bands as described above.

In one method to implement this approach, the RNs and UEs are required to transmit their unique IDs to the eNB in an initialization process. The IDs of the RNs and the UEs are different so that the eNB can distinguish an RN from UEs. By the use of the IDs, the eNB can force the UEs on one of the half bands of the aggregate carrier and the RN can be assigned the other half-band. In case the RN IDs have a similar rage as the UE IDs, the methods of the invention can be applicable to the non-backwards aggregated carrier component. The eNB can then send a modified physical broadcast channel ("PBCH") message to the release 8 devices; for example a spare bit may be used in the master information block to indicate that no permission is granted to release 10 (LTE- Advanced) UEs to camp on the backhaul carrier. This assumes C2 is a non-backward compatible component carrier. Figure 12 depicts a master information block ("MIB") 110 that could be used. In this approach, the MIB has an additional bit or byte telling the Release 10 UEs that the bandwidth for the backhaul is not available for them to use in camping on the RN or the eNB. In this manner the RN->eNB backhaul carrier is reserved.

Additional alternative embodiments are possible for TDD and FDD systems. For example, there may be an unequal "split" of the sub-bands in the backhaul link. The band may be one whole band that is "split" by dynamically allocating resources for the backhaul and for the access link according to the carrier capacities. This is possible because the eNB sees the RN as another UE. This alternative band splitting approach provides additional embodiments of the present invention that may further increase the capacity in the cell.

According to another illustrative embodiment, a communication base station such as an eNB is provided that may determine the sub-band assigned to the backhaul bandwidth for a relay node ("RN"). The UEs attached to the eNB are then assigned other component carriers based on the unique range of IDs of the UEs in an initialization process. In this manner the UEs are not using the bandwidth reserved for the RNs backhaul messages. Messages between the eNB and the RN may then be simultaneously transmitted with messages between the RN and its attached UEs, as the messages are using different frequency resources, and thus no delay is imposed on the message traffic by the use of the RN. In this manner the required periodicity for support of retransmit requests, for example, is provided while adding the capabilities of a relay node.

According to another illustrative embodiment, a communication network node such as a

RN is provided and one of the embodiments described above uses an aggregated component carrier CC, which is non-backward compatible with Rel-8. A backhaul bandwidth frequency is assigned to the RN by a corresponding eNB, using a master information block ("MIB") message. The UEs attached to the eNB are also configured to avoid the use of the backhaul BW by the MIB message. In this manner collisions are avoided and the RN may communicate on the backhaul interface while simultaneously communicating over an access link to the UEs attached to the RN; as these communications are separated in frequency resources.

In one exemplary embodiment, a method is provided comprising providing a

communication network node configured to receive and transmit packet signals over a radio frequency air interface; receiving an indication of a primary carrier; receiving an indication of a aggregate carrier sub-band; communicating backhaul messages over the air interface using the aggregate carrier sub-band; and communicating access messages to a second device using the primary carrier over the air interface. In another exemplary embodiment, the above method is provided and the backhaul messages are transceived to an enhanced Node B base station. In another exemplary embodiment, the above method is provided and the access messages are transceived to at least one user equipment using the primary carrier. In another method embodiment, the above method is performed and the communication network node is a relay node that forwards messages from an eNB to one or more user equipments. In another embodiment, the above described method is performed and the user equipments are LTE Release 8 compliant. In yet another method embodiment, the user equipment are LTE- Advanced compliant.

In another exemplary embodiment, the method comprises providing a user equipment configured to receive and transmit packet signals over a radio frequency air interface; receiving a master interface block message having a configuration field indicating an component carrier sub- band that is reserved; and attaching to a relay node for over the air communications using a primary carrier different from the aggregate carrier sub band.

In another embodiment, a relay node apparatus is provided comprising a programmable processor for transceiving radio frequency signals over an air interface. A computer readable medium is provided comprising instructions that, when performed by the programmable processor, cause the programmable processor to perform the steps of receiving an indication of a aggregate carrier sub-band; receiving an indication of a primary carrier; communicating backhaul messages over the air interface using the aggregate carrier sub-band; and

communicating access messages to a second device using the primary carrier over the air interface. In another exemplary embodiment, the computer readable medium is provided further comprises instructions that when executed cause the programmable processor to perform transceiving backhaul messages are to an enhanced Node B base station. In another exemplary embodiment, the above method is provided and the computer readable medium further comprises instructions that, when executed, cause the programmable processor to perform transceiving access messages to at least one user equipment using the primary carrier. In another exemplary embodiment, the above method is performed and the communication network node having a programmable processor is a relay node programmably configured to forward messages from an eNB to one or more user equipments. In another embodiment, the above described method is performed and the user equipments are LTE Release 8 compliant. In yet another method embodiment, the user equipment are LTE- Advanced compliant.

The advantages obtained with the embodiments of the present invention may include, without limitation, and depending on the application, reducing RN data forwarding delay, eliminating the need to reuse multi-band single frequency network ("MBSFN") subframes for relaying data, eliminating problems caused by loss of HARQ information, increasing the system capacity due to the "full duplex" operations. These advantages are obtained with only slight modification to the existing standards. The embodiments may be arranged to be backwards compatible with Release 8 UEs. Backhaul data may be concentrated on one component carrier and then forwarded to the RN attached UEs on several access component carriers.

Note that the implementation of any of the embodiments above may be performed in software, hardware, firmware, and may be provided as a set of instructions that are retrieved from storage and executed by a programmable processor or other programmable device that is part of an RN, UE or eNB implementation including without limitation core processors such as RISC, ARM, CPU, DSP and microcontroller cores, standalone integrated circuit devices, the method may be implemented as a state machine with associated logic circuitry, a field programmable gate array ("FPGA") or complex programmable logic device ("CPLD"), ASIC, semi-custom IC or the like may be used. The storage may be non- volatile memory such as FLASH or programmed memory such as programmable read-only memory ("PROM"), readonly memory ("ROM"), erasable programmable read-only memory ("EPROM") and the like. The storage may be a compact disc ("CD") or digital video disc ("DVD") program storage medium containing the executable instructions for performing the embodiments. In one embodiment executable instructions are provided on a computer readable medium that when executed, perform the method of assigning a primary carrier and an aggregate carrier that has two sub-bands for use with relay nodes, as discussed above.

The illustrative embodiments described above are directed to an E-UTRAN system primarily described with TDD. However, the embodiments are not limited to this example application and the use of the embodiments in other communications is envisioned as part of the present invention and within the scope of any claims presented. For example, the embodiments may be used in an E-UTRAN system with FDD.