Title

SCHEDULING IN A COMMUNICA ION SYSTEM CAPABLE OF USING MUTED OR ALMOST BLANK SUBFRAMES

This disclosure relates to control of transmissions in a communication system, and more particularly to scheduling of transmissions.

A communication system can be seen as a facility that enables communication sessions between two or more entities such as fixed or mobile communication devices, machine- type terminals, base stations, servers and/or other communication nodes. A

communication system and compatible communicating entities typically operate in accordance with a given standard or specification which sets out what the various entities associated with the system are permitted to do and how that should be achieved. For example, the standards, specifications and related protocols can define the manner how various aspects of communication shall be implemented between communicating devices. A communication can be carried on wired or wireless carriers. In a wireless

communication system at least a part of communications between stations occurs over a wireless link. Examples of wireless systems include public land mobile networks (PLMN) such as cellular networks, satellite based communication systems and different wireless local networks, for example wireless local area networks (WLAN). A wireless system can be divided into cells or other radio coverage or service areas.

A user can access the communication system by means of an appropriate communication device. A communication device of a user is often referred to as user equipment (UE) or terminal. A communication device is provided with an appropriate signal receiving and transmitting arrangement for enabling communications with other parties. Typically a communication device is used for enabling receiving and transmission of communications such as speech and data. In wireless systems a communication device provides a transceiver station that can communicate with another communication node such as e.g. a base station and/or another user equipment.

An example of communication systems is an architecture that is being standardized by the 3rd Generation Partnership Project (3GPP). This system is often referred to as the long- term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio- access technology. A further development of the LTE is often referred to as LTE- Advanced. The various development stages of the 3GPP LTE specifications are referred to as releases.

A communication system can comprise different types of radio service areas providing transmission/reception points for the users. For example, in LTE-Advanced the

transmission/reception points can comprise wide area network nodes such as a macro eNode B (eNB) which may, for example, provide coverage for an entire cell or similar radio service area. Network nodes can also be small or local radio service area network nodes, for example Home eNBs (HeNB), pico eNodeBs (pico-eNB), or femto nodes.

Some applications utilise radio remote heads (RRH) that are connected to for example an eNB. The smaller radio service areas can be located wholly or partially within the larger radio service area. Also, radio service areas of the same type may overlap. A user equipment (UE) may thus be located within more than one radio service area. This can cause interference.

Muting patterns can be used to address issues caused by interference. For example, 3GPP Release 10 specifications introduced a concept called time domain (TDM) enhanced inter-cell interference coordination (elCIC) where muting patterns are used. The elCIC concept provides coordination mechanisms for enabling reduction in downlink interference caused by an aggressor cell to a victim cell. However, muting patterns can have some undesirable effects on uplink performance. Two exemplifying cases can be mentioned to illustrate this. In Pico-Macro case the coverage area of a pico cell is extended by a mechanism where a macro cell mutes given subframes in the time domain thereby causing a reduction of interference seen by user equipments connected to the pico node. This may be especially the case for user equipments that are close to the edge of a pico coverage area. This may also be the case when a pico node is using a range extension feature such that pico-connected user equipments are kept in connected mode towards the pico node, even if the macro downlink (DL) connection may have better conditions. In Macro-Femto case an aggressor cell can be for example a closed subscriber group (CSG) Home eNB. The HeNB can apply some time domain muting patterns to give user equipments within the coverage area of the CSG HeNB the chance of "hearing" the macro cell. In this way, all macro connected user equipments can potentially be connected to the macro node and avoid experiencing a coverage hole.

Downlink muting patterns can be indicated to user equipments through dedicated signalling proving information on which subframes in the time domain are to be used for which purpose. One possibility for muting patterns is to indicate almost blank subframes (ABS). When applying such a scheme, an aggressor node or cell only transmits limited information such as information vital to the operation of the system. Examples of these include reference symbols, synchronization sequences, broadcast channels, and so on. No other physical downlink control channel (PDCCH) will be transmitted with the current proposals. A bit map pattern is used to indicate the ABS pattern which is exchanged between the macro eNB and pico eNB through an X2 message. Thus under the current elCIC schemes, the macro eNodeB applies almost blank sub-frames according to a predefined pattern, the ABS pattern, to guarantee the pico cell edge user equipment performance. The concept of almost blank subframe (ABS) and what is transmitted during these is described in more detail for example in 3GPP TR 36.300, Version 10.3.0 of March 2011.

A result of use of downlink time domain muting patterns is that only essential information is conveyed from an aggressor cell during the ABS. This can mean that the aggressor cell is not allowed to transmit any information that is related to the uplink direction.

Considering from downlink scheduling point of view this is a sensible configuration, as the downlink data channel (physical downlink shared channel; PDSCH) is transmitted within the same transmit time interval (TTI) as the downlink control channel (physical downlink control channel; PDCCH). However, as data on the uplink may also need control operations such as scheduling through the PDCCH there will be a loss of uplink capacity. This is so because the uplink scheduling is indicated in a subframe that is a fixed period ahead of the allocated transmission resource, and this subframe may be muted. In here it shall be appreciated that scheduling decisions, including scheduling decisions for the uplink direction are taken at the network side, typically by a controller associated with the base station. If a muted downlink subframe is the one that would have been used for granting of resources in the uplink, then the uplink transmission following the fixed period cannot take place as the grant information is not received. Thus, with muting there can be a reduction in the uplink capacity as some uplink transmit timing intervals are not addressable using current PDCCH allocations.

It is noted that the above discussed issues are not limited to any particular communication environment, but may occur in any appropriate communication system with retransmission mechanism.

Embodiments of the invention aim to address one or several of the above issues.

In accordance with an embodiment there is provided a method for receiving scheduling information by a device, comprising determining that at least one subframe capable of carrying scheduling information is muted, and determining scheduling information from at least one received subframe, the at least one received subframe being differently located from a subframe where the scheduling information would have been located without the muting.

In accordance with an embodiment, there is provided a method for transmitting scheduling information, comprising differentiating scheduling information between a first scheduling information and at least one second scheduling information, wherein the transmission of the first scheduling information coincides with a non-muted subframe and the transmission of the at least one second information coincides with a muted subframe, and

communicating scheduling information to at least one communication device in at least one subframe, wherein said at least one second scheduling information is included in at least one subframe that is differently located from a subframe where the at least one second scheduling information would have been transmitted without the muting.

In accordance with another embodiment, there is provided an apparatus for receiving scheduling information, the apparatus comprising at least one processor, and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to determine that at least one subframe capable of carrying scheduling information is muted, and determine scheduling information from at least one received subframe, the at least one received subframe being differently located from a subframe where the scheduling information would have been located without the muting.

In accordance with yet another embodiment, there is provided an apparatus for scheduling communications, the apparatus comprising at least one processor, and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to differentiate scheduling information between a first scheduling information and at least one second scheduling information, wherein the transmission of the first scheduling information coincides with a non-muted subframe and the transmission of the at least one second information coincides with a muted subframe, and communicate scheduling information to at least one communication device in at least one subframe, wherein said at least one second scheduling information is included in at least one subframe that is differently located from a subframe where the at least one second scheduling information would have been transmitted without the muting.

In accordance with a more specific embodiment switching to a scheduling mode where scheduling information received for at least two subframes can be distinguished is provided in response to the determining of muting of the at least one subframe.

The differentiation can be based on information identifying the device differently depending on muting state of relevant at least one subframe.

Information about temporary identifiers may be communicated for use by the device when determining scheduling information, wherein the temporary identifiers are different depending on muting state of relevant at least one subframe.

Information identifying the device may be used when searching within a physical downlink control channel search space.

The differentiation can be based on radio network temporary identifiers and/or on difference in at least one of scrambling, interleaving, Cyclic Redundancy Check and search space.

The device may be assigned with a set of search spaces and extending at least one of the search spaces based on information of a temporary identifier and timing of the relevant subframe.

The determining of muting may comprise determining existence of an almost blank subframe. Information of muting of subframes may be communicated to a user equipment, this including information about an almost blank subframe pattern of a cell.

Muting may also be determined based on power measurement on at least one downlink channel.

The delay between a downlink subframe carrying uplink scheduling information and relevant at least one uplink subframe may be longer when muting is determined than when muting is not determined.

Scheduling information for at least two uplink subframes may be communicated in a single downlink subframe. Decoding for the earliest of the uplink subframes may be performed first and the decoding of the later at least one subframe may be delayed.

A computer program comprising program code means adapted to perform the clamed method may also be provided.

Various other aspects and further embodiments are also described in the following detailed description and in the attached claims.

The invention will now be described in detail, by way of example only, with reference to the following examples and accompanying drawings, in which:

Figure 1 shows a schematic diagram of a network according to some embodiments; Figure 2 shows a schematic diagram of a mobile communication device according to some embodiments;

Figure 3 shows a schematic diagram of a control apparatus according to some

embodiments;

Figures 4 and 5 show flow charts according to certain embodiments; and

Figure 6 is a schematic illustration of subframes in a frame.

In the following certain exemplifying embodiments are explained with reference to a wireless or mobile communication system serving mobile communication devices. Before explaining in detail the exemplifying embodiments, certain general principles of a wireless communication system and mobile communication devices are briefly explained with reference to Figures 1 to 3 to assist in understanding the technology underlying the described examples.

In a wireless communication system mobile communication devices or user equipments (UE) 102, 103 are provided wireless access via at least one base station or similar wireless transmitting and/or receiving node or point. In the figure 1 example several overlapping access systems or radio service areas of a cellular system 100 and smaller radio service areas 1 10, 1 15, 1 17 provided by base stations 106, 107, 1 18 and 120 are shown. Each mobile communication device and station may have one or more radio channels open at the same time and may send signals to and/or receive signals from more than one source. It is noted that the radio service area borders or edges are schematically shown for illustration purposes only in Figure 1 . It shall also be understood that the sizes and shapes of radio service areas may vary considerably from the shapes of Figure 1. A base station site can provide one or more cells. A base station can also provide a plurality of sectors, for example three radio sectors, each sector providing a cell or a subarea of a cell. All sectors within a cell can be served by the same base station.

Base stations are typically controlled by at least one appropriate controller apparatus so as to enable operation thereof and management of mobile communication devices in communication with the base stations. In Figure 1 control apparatus 108 and 109 is shown to control the respective base stations 106 and 107. The control apparatus of a base station can be interconnected with other control entities. The control apparatus is typically provided with memory capacity and at least one data processor. The control apparatus and functions may be distributed between a plurality of control units.

In Figure 1 stations 106 and 107 are shown as connected to a wider communications network 1 13 via gateway 1 12. A further gateway function may be provided to connect to another network. The stations 1 18 and 120 can also be connected to the network 1 13, for example by a separate gateway function and/or via the controllers of a macro level station. In the example, station 1 18 is connected via a gateway 1 1 1 whilst station 120 connects via the controller apparatus 108.

A non-limiting example of the recent developments in communication system architectures is the long-term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) that is being standardized by the 3rd Generation Partnership Project (3GPP). As explained above, further development of the LTE is referred to as LTE-Advanced. Non- limiting examples of appropriate LTE access nodes are a macro base station, for example what is known as NodeB (NB) in the vocabulary of the 3GPP specifications, Home eNBs (HeNB), pico eNodeBs (pico-eNB), femto nodes, and radio remote heads (RRH) connected to an eNB.

The LTE employs a mobile architecture known as the Evolved Universal Terrestrial Radio Access Network (E-UTRAN). Base stations of such systems are known as evolved or enhanced Node Bs (eNBs) and may provide E-UTRAN features such as user plane Radio Link Control/Medium Access Control/Physical layer protocol (RLC/MAC/PHY) and control plane Radio Resource Control (RRC) protocol terminations towards the user devices. Of these Radio Resource Control (RRC) protocol is used to configure and control the radio resource between eNodeBs and user equipment. For example, RRC is used to configure the RLC/MAC and PHY layer at a user equipment and eNodeB. Functionalities of the RRC include establishment, modification and/or release of a RRC Connection, including for example assignment or modification of a user equipment (UE) identity (ID). The UE ID can be provided for example by a Radio Network Temporary Identifier (RNTI) used in the LTE for identifying user equipment when an RRC (Radio Resource Control) connection exists. Examples of different types of RNTI include Cell specific RNTI (C-RNTI) and semi- persistent scheduling RNTI (SPS-RNTI).

Other examples of radio access system include those provided by base stations of systems that are based on technologies such as wireless local area network (WLAN) and/or WiMax (Worldwide Interoperability for Microwave Access).

A possible mobile communication device for transmitting and retransmitting information blocks, such as subframes of transmission frames towards the stations of the system will now be described in more detail in reference to Figure 2 showing a schematic, partially sectioned view of a communication device 200. Such a communication device is often referred to as user equipment (UE) or terminal. An appropriate mobile communication device may be provided by any device capable of sending and receiving radio signals. Non-limiting examples include a mobile station (MS) such as a mobile phone or what is known as a 'smart phone', a portable computer provided with a wireless interface card or other wireless interface facility, personal data assistant (PDA) provided with wireless communication capabilities, or any combinations of these or the like. A mobile

communication device may provide, for example, communication of data for carrying communications such as voice, electronic mail (email), text message, multimedia and so on. Users may thus be offered and provided numerous services via their communication devices. Non-limiting examples of these services include two-way or multi-way calls, data communication or multimedia services or simply an access to a data communications network system, such as the Internet. User may also be provided broadcast or multicast data. Non-limiting examples of the content include downloads, television and radio programs, videos, advertisements, various alerts and other information. The mobile device may receive signals over an air interface 207 via appropriate apparatus for receiving and may transmit signals via appropriate apparatus for transmitting radio signals. In Figure 2 transceiver apparatus is designated schematically by block 206. The transceiver apparatus 206 may be provided for example by means of a radio part and associated antenna arrangement. The antenna arrangement may be arranged internally or externally to the mobile device.

A mobile device is also typically provided with at least one data processing entity 201 , at least one memory 202 and other possible components 203 for use in software and hardware aided execution of tasks it is designed to perform, including control of access to and communications with access systems and other communication devices. The data processing, storage and other relevant control apparatus can be provided on an appropriate circuit board and/or in chipsets. This feature is denoted by reference 204. The control apparatus of a user equipment can be configured to handle determining of muting state of information blocks and the subsequent control of uplink scheduling according to the herein described principles when the network (e.g. eNB) is using muting of some information blocks, for example for the purpose of reduced interference in certain areas of the network. The processor may also provide processing for an error correction mechanism, such as hybrid automatic repeat request (HARQ) processes.

A user may control the operation of the mobile device by means of a suitable user interface such as key pad 205, voice commands, touch sensitive screen or pad, combinations thereof or the like. A display 208, a speaker and a microphone can be also provided. Furthermore, a mobile communication device may comprise appropriate connectors (either wired or wireless) to other devices and/or for connecting external accessories, for example hands-free equipment, thereto.

Figure 3 shows an example of a control apparatus for a communication system, for example to be coupled to and/or for controlling a station of an access system. In some embodiments base stations comprise a separate control apparatus. In other embodiments the control apparatus can be another network element. The control apparatus 300 can be arranged to provide control on communications in the service area of the system. The control apparatus 300 can be configured to provide control functions in association with scheduling and muting by means of the data processing facility in accordance with certain embodiments described below. For this purpose the control apparatus comprises at least one memory 301 , at least one data processing unit 302, 303 and an input/output interface 304. Via the interface the control apparatus can be coupled to a receiver and a transmitter of the base station. The control apparatus can be configured to execute an appropriate software code to provide the control functions. It shall be appreciated that similar components can be provided in a control apparatus provided elsewhere in the system for controlling scheduling of uplink transmissions and muting of information blocks in the downlink.

As discussed above the current muting schemes may result in non-optimal use of uplink capacity. A possible way of making use of the currently unutilized uplink resources is to schedule resources ahead. That is, scheduling received at a particular time may not be for a subframe that would normally be scheduled in accordance with a 'normal' scheduling scheme but for another subframe or even for a plurality of other subframes. In accordance with an embodiment scheduling information received in a subframe can be intended for a subframe that is further ahead from a uplink subframe that is a fixed time ahead, as stipulated by a 'normal' delayed scheduling scheme. Figure 4 shows a flowchart for operation at a communication device, for example a user equipment, receiving scheduling information in accordance with an embodiment. The control apparatus of the device is responsive to determination that uplink scheduling can be affected by muting. At 40 it can be determined that at least one subframe the communication device receives is muted, the subframe being one that is capable of carrying transmission scheduling information. At 42 the communication device monitoring for scheduling information differentiates in received subframes between scheduling information that is intended for allocations of transmission resources in at least two subframes in different locations, depending on the determined muting state. According to a possibility a particular enabling mode where transmission scheduling information received for at least two subframes can be distinguished is switched on in response to the determination at step 40. Alternatively the communication device may be arranged to provide the differentiation continuously.

At 44 scheduling information in at least one received subframe can be detected. If it was determined at 40 that muting is applied it can be now determined, based on a

differentiation characteristic associated with the information, if the information in a subframe should have been transmitted in a muted location and is thus differently located from a timing where the transmission scheduling information would have been received without the muting. The transmission scheduling information can then be applied in transmission control at 46 to the correct subframe depending on determination whether it was received in a 'normal' or 'shifted' subframe.

The device can determine whether it is capable of scheduling ahead and decode a subframe where the control channel can schedule differently from the fixed scheme, depending on the muting state of the relevant control channel subframe. For example, it can be determined that a PDCCH can schedule ahead because of muting. The device can then look for the scheduling information through for example RNTI masking, as will be explained in more detail below

Figure 5 illustrates a method for communicating scheduling infrmation by a network controller element, for example at a macro eNB, in accordance with an embodiment where it is determined whether different scheduling, e.g. scheduling ahead, is needed because of a muted subframe further ahead in time. The controller can identify whether there is any user equipment or other nodes that need to be scheduled, and do the actual scheduling. More particularly, the controller can determine that at least one subframe capable of carrying transmission scheduling information is muted at 50. This information can be derived e.g. from the muting patterns. The controller can then at 52 enable differentiation of scheduling information in a subframe between first information transmission of which coincides with a non-muted subframes and at least one second information transmission of which would coincide with a muted subframe and thus cannot be successfully transmitted. By means of this feature the network controller can include in a downlink subframe uplink scheduling information that can relate to differently located subframes depending on the muting state of downlink subframes. At 54 the scheduling information can be communicated to at least one communication device in at least one subframe. The scheduling information that should have been communicated in muted downlink subframes is included in at least one non-muted downlink subframe that is differently located from a subframe where the transmission scheduling information would have been included without the muting.

Certain more specific exemplifying embodiments where a scheduling ahead functionality is provided are described in the following. In accordance with an embodiment the distinguishing feature is provided by the radio access system that assigns an user equipment different identifiers depending on which scheduling ('normal' or 'delayed') shall be applied. For example, a set of delayed scheduling radio network temporary identifiers (RNTIs) can be assigned to a user equipment (UE) that is in a mode where muting is applied, for example where almost blank subframes (ABS) are utilised.

If muting patterns are used a user equipment can be made aware of the own cell muting pattern. Information about the own cell muting patterns can be provided by a relevant network transceiver elements such as one or more eNBs to all connected user

equipments. The eNB(s) may also inform the user equipment(s) of which RNTIs shall be looked for when delayed scheduling is applied to subframes.

A user equipment may need various information to be able to provide this. The user equipment may need to be able to distinguish between the muted and non-muted subframes, such as ABS and non-ABS in the time domain. The determination of the muting state may be provided on various basis. The user equipment may know the muting state of relevant subframes in advance. Explicit signaling can be introduced for enabling the user equipment to determine which subframes are muted and which are not and/or for other relevant information in this context. The signaling may directly inform the user equipment of which subframes are muted and which are not. The signaling may be based, for example, on radio resource control (RRC) or medium access control (MAC) signaling. The user equipment may also determine the muting state based on its own monitoring, for example on the basis that the physical control format indicator channel (PCFICH) is missing. A missing channel may be determined for example based on power detection. Power detection of the physical HARQ indicator channel (PHICH) can also be used for the determination whether ABS or non-ABS configuration is in use.

The user equipment may be switched into a delayed scheduling mode in response to detection of muting. The detection may comprise detection of muting of a particular downlink subframe or subframes. In accordance with a possibility detection of muting in association with received downlink frames triggers the delayed scheduling mode. Once in the delayed scheduling mode the user equipment is aware that it can be potentially scheduled for uplink transmissions on subframes that are normally not reachable via the almost blank subframes or other muted subframes.

The user equipment can be provided with information of an alternative set of RNTIs that should be searched for within a physical downlink control channel (PDCCH) search space in order to obtain scheduling information that cannot be sent due to ABS. A physical downlink control channel (PDCCH) carries scheduling assignments and other control information, and is transmitted on one or several control channel elements (CCEs). In LTE blind decoding a user equipment checks predefined PDCCH locations, PDCCH formats, and downlink control information (DCI) formats and acts on messages satisfying predefined criteria. Carrying out such a 'blind decoding' of all the possible combinations would require the user equipment to make many PDCCH decoding attempts in every subframe, and thus LTE specifications define that each user equipment has only a limited set of control channel element (CCE) locations where a PDCCH may be placed. The set of CCE locations in which a user equipment may find its PDCCH can be considered as its 'search space'. A search space can be of a different size for each control channel format. Separate dedicated and common search spaces can also be defined. In such case a dedicated search space can be configured for each user equipment individually while all user equipments can be informed of the extent and location of a common search space. Such common search space is typically located in a fixed location such that it is possible to address all user equipments within a cell using only one signalling message on the PDCCH.

A possible operation will be discussed next with reference to the subframes of frame 60 of Figure 6. In a normal LTE operation there is a fixed timing relationship between the PDCCH transmitted in the downlink and the uplink transmission on the physical uplink shared channel (PUSCH). For example, Although Figure 6 shows a fixed delay of four subframes between the reception of the grant and the transmission, this is just an example to illustrate th principle and any other appropriate value can be used as well. The delay is arranged such that a PDCCH grant for uplink (UL) data in subframe 'k' will result in physical uplink shared channel (PUSCH) transmission in subframe 'k+4'. In the example of Figure 6 two such subframe pairs within the transmission scheme are considered. For simplicity, these are denoted 'k+0' (i.e. 'k') and 'k+1', the "+" part of the subframe number referring to the timing relative to the starting point of these

considerations. For simplicity, the starting point k in Figure 6 is shown to be the first subframe of frame 60 but this does not necessarily need to be so.

With a normal operation as described above and shown by the two uppermost arrows 64 and 65 in frame 60 subframe 'k+0' would be able to schedule uplink resources for transmission in subframe 'k+4' and subframe 'k+1' would be able to schedule for UL transmission in subframe 'k+5', and so forth. That is, a scheduling delay of 4 subframes can be applied for UL transmissions/allocations when in a 'normal' mode.

In accordance with a possibility the method can be applied for time domain enhanced inter cell interference coordination (TDM elCIC) in an environment such the LTE. In a TDM elCIC scenario where subframe 'k+1 ' is subject to ABS muting it is not possible to transmit PDCCH in subframe 'k+1'. Consequently there can be no uplink transmission in subframe 'k+5'. In accordance with an embodiment uplink allocations that would normally be transmitted in subframe 'k+1' are embedded in the earlier subframe 'k+0' using a different user equipment identity, for example RNTI information element. Use of a delay period of five subframes for subframe k+5 is illustrated by arrow 62 in Figure 6. Uplink grant for subframe k+4 can be communicated normally, and thus can be according to the 'normal' delay of four subframes, as shown by arrow 64.

In this mode the user equipment can search for allocations in subframe 'k+0' using its regular RNTI(s), and act according to the scheduling information detected. In the next subframe, the user equipment can search the same PDCCH but with a different search space. This search space can be defined through the combination of the different RNTI and subframe number. Wthout being limited by this, a detailed example of a search space can be found from 3GPP TS in 36.213, version 10.2.0, June 2011 , section 9.1.1. In short, search spaces are used to create a high degree of randomization between UEs and their search positions. Each UE will have a specific search space that is divided into four different aggregation levels. At each aggregation level the UE starts looking for a possible allocation on a control channel. A hashing function is used that takes the RNTI and "time" (subframe number) into account when defining the starting point. When the starting point at a given time for a given UE has been determined, the UE will look for a control channel at the starting point and the following search positions. Another UE with another RNTI will have another starting point, and also the same UE at another time will have yet another starting point. Thus there will be a high randomization between starting points and the probability of collisions when scheduling multiple UEs is reduced. Wth delayed scheduling through RNTI separation it is possible to have both time and RNTI to separate the search spaces for "normal" and "delayed" scheduling. A benefit of this approach is that the user equipment blind decoding effort for delayed scheduling occasions can be distributed over subframes where the actual scheduling decision is applied.

The user equipment can perform blind decoding twice in a subframe that contains both normal and delayed grants. However, the decoding does not need to take place simultaneously. The decoding for the delayed grant can also be done one subframe later (i.e. in subframe 'k+1' in this example) because the scheduling information is needed one subframe later. Because of this the decoding performance of the user equipment is not necessarily impacted and the same hardware can be reused for both sets of decoding attempts. Some additional memory may be needed to store the received samples that are going to be re- investigated.

Thus different RNTIs can be used to distinguish different grants. An advantage of this is that an existing functionality can be reused. However, it is also be possible to use other schemes to differentiate among the different scheduling options. The differentiation may be based on, for example, changed or added scrambling, interleaving, changed cyclic redundancy check (CRC) calculation, use of different search spaces (i.e. the place where to find the UL grants would be different for normal and delayed grants - other than what is currently given by the search space definitions). Also a combination of these schemes can be used.

If there are two or more consecutive muted subframes, two or more additional uplink grants can be sent in the same earlier subframe using two or more different RNTIs, or other differentiator.

Certain embodiments may allow scheduling of two uplink grants in the same downlink subframe without changing the format of the downlink assignment of group grant message, for example a message according to one of the Downlink Control Information (DCI) formats. Currently such scheduling would require additional explicit information to distinguish delayed scheduling from normal scheduling, e.g. by adding an additional bit. This overhead may be avoided by introducing additional blind decoding options. The blind decoding options can be associated with delayed scheduling and are different to the ones used for non-delayed grants. In accordance with an alternative embodiment, a modified DCI format is used. For example, to address the restriction that the DL DCI format is not applicable for a scheduling ahead subframe, special UL scheduling information in the DCI fields that are currently used for DL scheduling. For example, in case of 10 MHz system bandwidth, a regular UL DCI contains 43 bits, while the regular DL DCI (format 1) contains 47 bits. These downlink DCI bits can be used as bit for UL allocation and some additional scheduling.

In accordance with an embodiment the relocated scheduling information can be located in a subframe that follows a muted frame, for example ABS.

The user equipment specific search space can be modified so that the UE searches the grants in different areas, depending on the state of the muting. One approach can be that the UE is assigned a given set of search spaces, and these are extended in a linear fashion according to the delay (basically, the search space for the delayed allocation is not derived from the new timing and new RNTI, but rather from the original RNTI and timing). More particularly, on an aggregation level "time" and RNTI can be used to define the search space. For instance, one may have "normal" search space start at location 12 and ending at location 17 (six positions in total at this aggregation level). With a new RNTI and "time" it is possible to have the search space start at any position, for instance at 45 or any other number. In principle, the new starting point could also be e.g. 1 1 or 13, with five positions overlapping. With this alternative, the "delay" search space can simply start at location 18 and continue to location 23. In this way it is possible to ensure the least overlap between original allocations and delayed ones for the same UE.

A communication system can be provided with error correction functionality, such as with a possibility of requesting for retransmission of any information that the recipient could not successfully decode. For example, the 3GPP LTE uses a hybrid automatic repeat request

(HARQ) error control mechanism. The error control mechanism can be implemented such that a device which receives either a positive or a negative acknowledgement

(ACK/NACK) or other indication from another device of an error free or erroneous receipt of transmitted data can take appropriate action. Typically this means resending of a protocol data unit to the receiving device in response to a negative acknowledgement. In

LTE the acknowledgement signalling can be communicated on a physical HARQ indicator channel (PHICH) based on a HARQ timing scheme. Release 8 of the LTE specifications defines that HARQ for uplink shall be based on synchronous operation. A benefit from this is reduced signalling as well as fixed and known timing relations between transmissions and potential retransmissions. Because of this user equipments do not need to stay awake looking for retransmission requests/grants at random times, but can tie these to fixed time instants. Further, fixed round trip times and subframe lengths may be provided. To illustrate, for example in accordance with LTE Release 8 eight ms HARQ round trip time (RTT) is provided while the transmission time interval (TTI) is 1 ms. Thus a total of eight HARQ processes is made available in LTE Release 8 to facilitate continuous uplink transmission from a single user equipment. A drawback of synchronous uplink hybrid automatic repeat request (UL HARQ) is that if a retransmission grant on the downlink is missed by a user equipment the next scheduling opportunity will be located an additional delay later corresponding to the RTT. In the LTE based systems that would be 8 ms. If UL HARQ is combined with use of muting such as almost blank subframes (ABS) retransmission delays can be impacted heavily by the introduction of the muting. This may be the case especially when extensive muting is applied potentially causing high retransmission delays for uplink data. The shifted sending of transmission scheduling information in subframes that are not the ones the information should have been sent can also be used to address this issue.

The required data processing apparatus and functions of a control apparatus for the determinations and control of scheduling of transmission in subframes at a communication device, a base station and any other node or element may be provided by means of one or more data processors. The described functions may be provided by separate processors or by an integrated processor. The data processors may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASIC), gate level circuits and processors based on multi core processor architecture, as non limiting examples. The data processing may be distributed across several data processing modules. A data processor may be provided by means of, for example, at least one chip. Appropriate memory capacity can also be provided in the relevant devices. The memory or memories may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory.

An appropriately adapted computer program code product or products may be used for implementing the embodiments, when loaded or otherwise provided on an appropriate data processing apparatus, for example for causing determinations for adaptive assignment of retransmission subframe identities and for the related operations. The program code product for providing the operation may be stored on, provided and embodied by means of an appropriate carrier medium. An appropriate computer program can be embodied on a computer readable record medium. A possibility is to download the program code product via a data network. In general, the various embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Embodiments of the inventions may thus be practiced in various components such as integrated circuit modules. The design of integrated circuits is by and large a highly automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate.

It is noted that whilst embodiments have been described in relation to LTE-Advanced, similar principles can be applied to any other communication system where a carrier comprising a multiple of component carriers is employed. Therefore, although certain embodiments were described above by way of example with reference to certain exemplifying architectures for wireless networks, technologies and standards,

embodiments may be applied to any other suitable forms of communication systems than those illustrated and described herein.

The foregoing description has provided by way of exemplary and non-limiting examples a full and informative description of the exemplary embodiment of this invention. However, various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings and the appended claims. For example, a combination of one or more of any of the other embodiments previously discussed can be provided. All such and similar modifications of the teachings of this invention will still fall within the scope of this invention as defined in the appended claims.