Adaptive transmission modes for transparent relay

There is transmitted to a user equipment UE in a first subframe of a radio frame a downlink shared channel DSCH according to a first relay-transmission mode (e.g., mode A or A′ in the examples); then switch to a second relay-transmission mode (e.g., mode C or C′ in the examples) within the radio frame based on a channel quality of the DSCH. After switching, then transmit to the UE, in a subsequent subframe of the radio frame, the DSCH according to the second relay-transmission mode. In this embodiment the HARQ process is synchronous and non-adaptive for mode C: the eNB re-transmits packets to the UE in a predetermined fashion to be concurrent with transmission of those same packets from the relay node, as scheduled by the eNB. In this embodiment the eNB receives the UE's NACK for the data that is to be retransmitted via relay through the relay node.

TECHNICAL FIELD

The teachings herein relate generally to wireless networks that employ a relay between the access node and the user equipment, and are particularly relevant for the time division duplex mode of E-UTRAN (evolved UTRAN).

BACKGROUND

The following abbreviations and terms are herewith defined:

3GPP third generation partnership project

ACK acknowledgment

CQI channel quality indicator(s)

CRS/DRS common reference signal/dedicated reference signal

DL downlink

eNB Node B of an E-UTRAN system

HARQ hybrid automatic repeat request

LTE long term evolution of UTRAN (E-UTRAN or 3.9G)

MCS modulation and coding scheme

NACK negative acknowledgment

Node B base station or similar network access node

OFDM orthogonal frequency division multiplex

P-BCH physical broadcast channel

PDCCH physical downlink control channel

PDSCH physical downlink shared channel

PHICH physical HARQ indicator channel

PRB physical resource block

P-RACH physical radio access channel

PUCCH physical uplink control channel

PUSCH physical uplink shared channel

QoS quality of service

RN relay node

SFBC space frequency block coding

UE user equipment (e.g., mobile equipment/station)

UL uplink

UMTS universal mobile telecommunications system

UTRAN UMTS terrestrial radio access network

3GPP is standardizing the long-term evolution (LTE) of the UTRAN radio-access technology which aims to achieve reduced latency, higher user data rates, improved system capacity and coverage, and reduced cost for the operator. The current understanding of LTE relevant to these teachings may be seen at 3GPP TR 25.814 (v7.1.0, 2006-09) entitled PHYSICAL LAYER ASPECTS OF EVOLVED UTRA and herein incorporated by reference. Both frequency division duplex (FDD) and time division duplex (TDD) are considered in LTE.

One variation of LTE is termed LTE-Advanced or LTE-A. LTE-Advanced aims to provide significantly enhanced services by means of even higher data rates and lower latencies with reduced cost. Since the new spectrum bands for IMT (international mobile telecommunication, such as detailed at IMT-2000) contain higher frequency bands and LTE-Advanced is aiming at higher data rates, coverage of one eNB is limited due to the high propagation loss and limited energy per bit. Relaying has been proposed in many workshop presentations to enlarge the coverage, to improve the capacity and to improve the cell edge performance. Details of such proposals may be seen, for example, at document R1-082024 entitled “A discussion on some technology components for LTE-Advanced” by Ericsson (3GPP TSG RAN WG1 #53; Kansas City, Mo., USA; May 5-9, 2008); document REV-080006 entitled “Requirements for LTE advanced” by Panasonic (dated Apr. 7, 2008); and document R1-081791 entitled “Technical proposals and considerations for LTE advanced” also by Panasonic (3GPP TSG RAN WG1 #53; Kansas City, Mo., USA; May 5-9, 2008). These are attached to the priority document (U.S. Provisional Patent Application Ser. No. 60/191,485) as respective exhibits A, B and C.

Backward compatibility of LTE-Advanced with LTE is required. For this reason, the design of a transparent relay concept to LTE Release 8 (Rel.8) UEs is attractive, where the node performing relay of data/signaling between the eNB and the UE is essentially transparent to the UE. Though the higher layer relay (referred to at document R1-082024 as self backhauling) will have little impact on the published standard implementation of LTE-Advanced, the relay concept introduces large delay and overhead.

In certain terminal implementations consistent with Rel.8 of LTE for TDD, the channel estimator uses a CRS across subframe boundaries. The channel estimator is reset after each UL subframe. Introduction of relays in the network will need to be compatible with these pre-existing/pre-designed UEs. As relays are not yet specified, this means these Rel.8 UEs have no knowledge of relays in the network. To achieve backward-compatibility with these Rel.8 UEs, the already-designed channel estimation algorithm must be addressed as well as common and shared signaling.

The problem is illustrated by example. Consider the case where a current DL subframe is received by a UE from a RN, and a previous (contiguous) DL subframe is only received by the UE from the eNB. This forms two links: RN to UE and eNB to UE, over the current and previous sub-frames respectively. If that UE is one of the Rel.8 (or similar) ones, it has no way of knowing that it received the two different subframes over two different links. The channel estimator in the UE will interpolate the CRS over both of those sub-frames to estimate the channel for demodulation and decoding. As applied to the PDSCH in the current subframe, this will yield the wrong channel estimate and have a significant impact on PDSCH detection reliability. The problem also exists if, in the current subframe, both the RN and eNB transmit to the UE in a co-operative diversity mode.

Simply said, backward-compatibility with Rel.8 UEs means that relays must not interfere with UEs, since the UEs must be able to receive eNB common signaling for initial cell access (e.g. CRS, P/S-SCH, P-BCH), for neighbor cell monitoring, and also for shared control signaling (e.g. PDCCH, PHICH, PUCCH) so as to acquire parameters that are used for data transmission. This implies that a transparent relay needs to be used, for which one embodiment is set forth at document R1-082470 entitled “Self-backhauling and lower layer signaling” by Ericsson (3GPP TSG RAN SG1 #53 bis; Warsaw, Poland; Jun. 30-Jul. 4, 2008), attached to the above-referenced priority document as Exhibit D.

There are additional issues to consider in making transparent relays compatible with Rel.8 UEs. Asynchronous HARQ was agreed for LTE DL in Rel.8, where the eNB always needs to send PDCCH for retransmission. For the case where relays are used, another issue arises is how the coordination can be done by the eNB and the RN to do concurrent transmission. In the DL, the eNB will send PDCCH and PDSCH in one sub-frame for retransmission when a NACK was received. But prior to that retransmission, the RN has to know which physical resources (time and frequency) are used for retransmission of the packet by the eNB, so that the RN can use the same resources to transmit the same packet concurrently.

Another issue that arises concerns PUCCH coverage. Consider the case where an ACK/NACK response from the UE is erroneously decoded in the eNB and/or in the RN. In such case, the inconsistent interpretation of the UE's ACK/NACK will cause some degradation of QoS. For example, if the Rel.8 UE sends back a NACK, then the eNB may receive/decode an ACK and the RN may receive/decode a NACK. In such a case, the eNB will re-allocate this resource to other users and the RN will do non-adaptive retransmissions. This can easily result in a serious resource collision, and in the presence of that collision the QoS of two users cannot be guaranteed.

DRS for relays was recently proposed by Nortel at document R1-083158 entitled “Some further considerations for Downlink Transparent Relay for LTE-A” (3GPP TSG RAN1 #54; Jeju, Korea; Aug. 18-22, 2008), attached to the above-referenced priority document as Exhibit E.

SUMMARY

In a first aspect thereof the exemplary embodiments of this invention provide a method which comprises: transmitting to a user equipment in a first subframe of a radio frame at least one downlink shared channel according to a first relay-transmission mode; switching to a second relay-transmission mode within the radio frame based on a channel quality of the downlink shared channel; after switching, transmitting to the user equipment in a subsequent subframe of the radio frame on the at least one downlink shared channel according to the second relay-transmission mode; and for the case of a packet re-transmission according to the second relay-transmission mode, re-transmitting the packet to the user equipment in a pre-determined manner so as to be concurrent with transmission of a same packet from a relay node.

In a second aspect thereof the exemplary embodiments of this invention provide a computer readable memory storing a program of instructions. In this aspect of the invention, when the stored instructions are executed by a processor they result in actions which comprise: transmitting to a user equipment in a first subframe of a radio frame at least one downlink shared channel according to a first relay-transmission mode; switching to a second relay-transmission mode within the radio frame based on a channel quality of the downlink shared channel; after switching, transmitting to the user equipment in a subsequent subframe of the radio frame on the at least one downlink shared channel according to the second relay-transmission mode; and for the case of a packet re-transmission according to the second relay-transmission mode, re-transmitting the packet to the user equipment in a pre-determined manner so as to be concurrent with transmission of a same packet from a relay node.

In a third aspect thereof the exemplary embodiments of this invention provide an apparatus comprising sending means (for example a transmitter or a transceiver) and processing means (for example a digital signal processor or a general purpose processor). The sending means is for sending to a user equipment in a first subframe of a radio frame at least one downlink shared channel according to a first relay-transmission mode. The processing means is for switching to a second relay-transmission mode within the radio frame based on a channel quality of the downlink shared channel. Then, after switching, the sending means is for transmitting to the user equipment in a subsequent subframe of the radio frame on the at least one downlink shared channel according to the second relay-transmission mode. For the case of a packet re-transmission according to the second relay-transmission mode, the sending means is further for re-transmitting the packet to the user equipment in a pre-determined manner so as to be concurrent with transmission of a same packet from a relay node.

These and other aspects of the invention are set forth with more particularity below.

DETAILED DESCRIPTION

It is initially noted that the non-limiting examples and the explanations below are in the context of a LTE or LTE-Advanced network, but embodiments of this invention are not so limited and may be employed in any network protocol, such as for example UTRAN (universal mobile telecommunications system terrestrial radio access network), GSM (global system for mobile communications), WCDMA (wideband code division multiple access, also known as 3G or UTRAN), WLAN (wireless local area network), WiMAX (worldwide interoperability for microwave access) and the like, in which transmissions between the access node (eNB) and the UE (subscriber station) may pass through a relay node. Further, the various names used in the description below (e.g., DRS/CRS, PDSCH, ACK/NACK, eNB etc.) are not intended to be limiting in any respect but rather serve as particularized examples directed to specific LTE implementations using current LTE terms for a clearer understanding of the invention. These terms/names may be later changed in LTE and they may be referred to by other terms/names in different network protocols, and these teachings are readily adapted and extended to such other protocols.

Embodiments of this invention relate to different relay-transmission modes that are switched within a frame (e.g., at sub-frame boundaries within a single radio frame). The switching is done based on estimated channel quality, which may be measured/determined in different ways as detailed below. The different relay-transmission modes relate to initial transmissions, not re-transmissions such as may be sent in response to receiving a NACK from the UE. The transmissions may be of data on a shared channel PDSCH and/or control signaling on various common or shared control channels P-BCH, PDCCH and PHICH. It is noted that not every one of the modes must employ a relay, but since they are relay-transmission modes at least one of the modes that is a viable transmission option for the eNB must employ a relay, which in the examples is transparent to the UE. In an exemplary embodiment detailed below there are three relay-transmission modes, termed mode A, mode B and mode C.

In mode A the eNB transmits to the UE (on the P-BCH, PDCCH, PHICH, and PDSCH) a CRS but no DRS. In this mode A the relay (RN) is not used. Of course, the same eNB may simultaneously transmit to other UEs in a different mode in which a relay is used, but these non-limiting examples are in the context of a single UE. The UE uses the CRS to compute CQI for the PDSCH and for the control channels, and since the relay does not transmit in mode A there is no interference from it. In mode B the eNB transmits to the UE a CRS with the control channels P-BCH, PDCCH and PHICH and again does not transmit to the UE a DRS, but under mode B instance the eNB does not transmit to the UE the PDSCH; instead in this mode the relay transmits the PDSCH with a DRS to the UE. The UE can then use the DRS to compute its CQI for the PDSCH, and the CRS to compute its CQI for the control channels. In mode C the eNB transmits to the UE a CRS with the control channels P-BCH, PDCCH and PHICH, and also a DRS with the PDSCH. But further in mode C the relay also transmits to the UE, concurrently with the eNB's transmissions, the DRS and the PDSCH. The UE can use the DRS to compute its CQI on the PDSCH. Since this DRS is transmitted concurrently by both the eNB and the relay, the DRS is beamformed for cooperative diversity, and MIMO may also be used by the relay in mode C (since it is assumed the RN-to-UE link is the stronger of the two).

In general terms, the eNB transmits, to a UE in a first subframe of a frame, a CRS with no DRS on a DL shared channel (DL-SCH) using a first relay-transmission mode (e.g., mode A). Based on a channel quality of the DL-SCH the eNB switches to a second relay-transmission mode (e.g., mode C), and transmits to the UE in a different subframe of the frame a DRS on the DL-SCH using the second relay-transmission mode. Further details below add HARQ aspects to the above embodiment.

Reference is now made toFIG. 1Afor illustrating a simplified block diagram of various electronic devices that are suitable for use in practicing the exemplary embodiments of this invention. InFIG. 1Aa wireless network9is adapted for communication between a UE10and an access node (eNB)12. The network9may include a gateway GW/serving mobility entity MME/radio network controller RNC14or other radio controller function known by various terms in different wireless communication systems. The UE10includes a digital processor (DP)10A, a memory (MEM)10B that stores a program (PROG)10C, and a suitable radio frequency (RF) transceiver10D coupled to one or more antennas10E (one shown) for bidirectional wireless communications over one or more wireless links20with the eNB12.

The eNB12also includes a DP12A, a MEM12B, that stores a PROG12C, and a suitable RF transceiver12D coupled to one or more antennas12E. Typically the eNB12operates an array of antennas for beamforming, MIMO operations, and the like, as is well known in the art. Each of these antennas is identified below by an antenna port number (port1, port2, etc.). The eNB12may be coupled via a data path30(e.g., lub or S1 interface) to the serving or other GW/MME/RNC14. The GW/MME/RNC14includes a DP14A, a MEM14B that stores a PROG14C, and a suitable modem and/or transceiver (not shown) for communication with the eNB12over the lub link30.

Also within the eNB12is a scheduler12F that schedules the various UEs under its control for the various UL and DL subframes on the PDSCH. Once scheduled, the eNB12sends messages on the PDCCH to the UEs with the scheduling grants (typically multiplexing grants for multiple UEs in one message). Generally, the eNB12of an LTE/LTE-A system is fairly autonomous in its scheduling and need not coordinate with the GW/MME14excepting during handover of one of its UEs to another eNB.

AtFIG. 1Bare shown four nodes operating in a LTE-A system: the eNB12, the remote UE10, a local UE11which is near enough to the eNB12or has sufficient signal strength/channel reliability that relayed communications are not necessary to maintain a guaranteed quality of service, and a relay node16. Each of the LUE11and the RUE10is similar to the UE10apparatus detailed above with respect toFIG. 1A; and each of the relay node16and the eNB12is similar to the eNB12apparatus detailed above with respect toFIG. 1A. The relay node16may be embodied as a UE or as a fixed relay that is network-owned or at least network-operated (e.g., mounted to a building, tower or train), so in some instances the relay may be MIMO capable and in other instances it may not. Major components of the nodes atFIG. 1Bare shown being similar to those detailed with respect toFIG. 1Aand are not detailed again. Also atFIG. 1Bare links between the various nodes, each of which is shown as bi-directional: link31is between the eNB12and the local UE11; link36is between the eNB12and the relay node16; link20is as described atFIG. 1Abetween the eNB12and the (remote) UE10, and link26is between the relay node16and the (remote) UE10. There may be a link (not shown) between the relay16and the local UE11, though if that were to be achieved by the relay-transmission mode switching detailed herein the LUE11would be considered a RUE10instead; the relay node16is used for transmissions to the RUE10but is not used for transmissions to the LUE11, and the difference is based on the channel conditions which determine the relay-transmission mode in use.

At least one of the PROGs10C,12C and14C is assumed to include program instructions that, when executed by the associated DP, enable the electronic device to operate in accordance with the exemplary embodiments of this invention, as detailed above. Inherent in the DPs10A,12A, and14A is a clock to enable synchronism among the various apparatus for transmissions and receptions within the appropriate time intervals and subframes/slots required, as the scheduling grants and the granted resources/subframes are time dependent.

The PROGs10C,12C,14C may be embodied in software, firmware and/or hardware, as is appropriate. In general, the exemplary embodiments of this invention may be implemented by computer software stored in the MEM10B and executable by the DP10A of the UE10and similar for the other MEM12B and DP12A of the eNB12, or by hardware, or by a combination of software and/or firmware and hardware in any or all of the devices shown.

In an exemplary but non-limiting embodiment of the invention, beamforming and relay transmission mode can be combined readily. It assumed that the DRSs are transmitted by the eNB12on antenna port5to the remote UE (RUE)10in the eNB-RUE link20, and by the relay node16to RUE10in the RN-UE link26. The eNB12and the relay node16can transmit a beamformed DRS and PDSCH to the RUE10concurrently under Mode C. A MIMO mode may be used for the eNB-local UE11(LUE) link31, and/or for the eNB-RN link36to increase data rates. It is a reasonable assumption that these links31,36benefit from a relatively high SINR (signal to interference plus noise ratio), as the LUE11does not require relay-aided transmission, and the eNB-RN fixed links36can be planned in the network (for the case where the relays in use are network-owned and/or operated).

Exemplary but non-limiting embodiments of the invention also assume that the relay-aided transmissions (link26) can operate at a significantly higher SINR. The eNB12may indicate to the relay node16the MCS scheme to be used for the concurrent eNB12and relay node16transmissions to the RUE10. The choice of MCS may be based on an outer loop link adaptation (OLLA) mechanism depending on ACK/NACK rates when relay-aided transmission is switched on via switching the relay-transmission mode. The eNB12may monitor channel quality indications/indicators CQI, which are computed by the UE from the CRS, and from monitoring ACK/NACK reports sent by the UE in order to determine the proper relay-transmission mode that switches on or off the relay mode.

As noted above, in an exemplary and non-limiting embodiment of the invention there are three relay-transmission modes from which the eNB12chooses. These modes may be published in a standard for making relay transmissions compatible with Rel.8 UEs and stored in the eNB12memory12B, and are reviewed again here and below in a bit further detail as to how they are selected.Mode A: the eNB12transmits to the UE10,11a common RS for P-BCH, PDCCH, PHICH and PDSCH. The common RS can be used for CQI computation in the LUE11and the RUE10. The eNB does not send any DRS in mode A, and the relay node16is not used for transmission to the UEs operating under this mode.Mode B: the eNB12transmits to the UE10,11a common RS for P-BCH, PDCCH and PHICH. The common RS can be used for CQI computation in the LUE11and the RUE10. The eNB12does not transmit any DRS, and does not transmit the PDSCH. Instead the relay node16transmits the DRS and the PDSCH.Mode C: this mode may be considered a variant of mode B, where the eNB12transmits to the UE10,11a common RS for P-BCH, PDCCH and PHICH. The common RS can be used for CQI computation in the LUE11and the RUE10. There is concurrent transmission of the DRS and the PDSCH by the eNB12and the relay node16to the UE10.

Relay-transmission modes A, B, and C may be switched according to the following exemplary but non-limiting procedure. Begin by assuming the eNB12transmits to the LUE11in mode A on link31, which by the above description the LUE11computes CQI using the CRS. The LUE11reports this computed CQI to the eNB12as is normal. Now, if CQI measured from the CRS and reported by the UE is below some threshold value (CQI_threshold) and remains below that threshold for some predetermined period of time (t1), then the eNB12assumes that the UE11is in a bad channel condition and relay-aided transmission is triggered (which means the UE is now considered by the eNB12to be a RUE10). The eNB12transmits on link36those packets it has for the RUE10(which in this example was originally the LUE11) to the relay node16in mode B or C, and then the relay node16transmits those received packets to the RUE10. For the case where relay-transmission mode C is used, co-operative diversity is enabled in that the eNB12transmits via link20the packets to the RUE10and the relay node16concurrently transmits via link26the same packets to the RUE10. In either mode, the RUE10measures CQI on the link26,20using the CRS or alternatively the DRS and reports that CQI back to the eNB12. If in fact it occurs that the CQI measured from the CRS or alternatively DRS and reported by the UE10is higher than the CQI_threshold, the relay-transmission mode reverts back to mode A.

The CQI_threshold and the time threshold t1are used at the eNB12to maximize coverage and throughput of the relay-aided transmission in modes B or C to the RUE10. An exact determination of these thresholds is not detailed herein but may be readily determined, or even made relatively arbitrary so to approximate where a maximized data rate might be achieved without precision determination. In certain exemplary and non-limiting embodiments the relay-transmission mode A, B or C may be selected using ACK/NACK reporting which the eNB12receives from the UE10on the PUCCH, either instead of the UE's reported CQI or in conjunction with that CQI.

ConsiderFIG. 2which illustrates transmissions and relay-transmission modes for both LUE11and RUE10within the same radio frame220. DRSs are transmitted204,209by the eNB12(on antenna port5) to the RUE10over the eNB-RUE link20and also transmitted204′,209′ by the relay node16to the RUE10on the relay-UE link26in subframes4and9of the frame220. Because the transmissions from the eNB12and from the relay node16to the RUE10are done concurrently, a co-operative diversity transmission mode is effectively carried out. The CRSs (e.g., sent on antenna ports0,1,2,3) are only transmitted by the eNB12.

In the LUE11, channel estimation in subframes0and5for the eNB-LUE link31only use the common RS which is sent200,205by the eNB12in those subframes, since for the LUE11there are no transmissions from the relay node16. Hence, there is no impact from the eNB-RUE transmission204or from the relay node-RUE transmission204′ in subframe4to the eNB-LUE11transmission205in subframe5(and similarly no impact from the transmission in subframe9of the previous radio frame from the eNB12(similar to transmission209) and from the relay node16to the RUE10(similar to transmission209′) on the illustrated reception in subframe0by the LUE11of the transmission201from the eNB12), because the relay does not transmit any common RS. While transmissions200and205are shown from the eNB12to the RN16, the text within subframes0and5for the eNB indicate these transmissions are also to the LUE11.

According to exemplary but non-limiting embodiments of the invention, the common signaling (CRS, P-SCH, S-SCH, P-BCH on DL and P-RACH on UL) and shared signaling (PDCCH, PHICH, etc. on DL and PUCCH on UL) are transmitted (DL) or received (UL) by the eNB12, and the relay node16takes no part. This ensures a transparent relay operation. The relays are hence not used to enhance signaling coverage, as that function is provided solely by the eNB12in this exemplary but non-limiting embodiment. The relays16may be used to enhance PDSCH and PUSCH coverage and capacity.

In the RUE10, the channel estimator (which lies in the transceiver10D or alternatively within the processor/DSP10A) is reset when processing the DRS to estimate the channel. This helps in case there is a DL subframe with an eNB-LUE link20immediately prior to a DL subframe with an eNB-RUE link20or a relay node-RUE link26(this scenario is not explicitly shown in the example ofFIG. 2).

In certain current Rel.8 terminal implementations, this channel estimator in the UE is reset at the beginning of each subframe. The UE's channel estimator uses DRS in one physical resource block for channel estimation of PDSCH. Testing of the channel estimator implicitly requires that the channel estimator be reset.

The CRS (sent on antenna ports0&1) are only transmitted by the eNB12for two-transmission antenna SFBC, P-BCH, PDCCH, and PHICH transmissions. CRSs on antenna ports0,1,2,3are only transmitted by the eNB12for PDSCH transmissions over the eNB-LUE link31. DRSs sent from antenna port5are transmitted by the eNB12and by the relay node16for the respective eNB-RUE link20and the relay node-RUE link26.

Further atFIG. 2it can be seen that at subframe3the RUE10transmits203to the eNB12and at subframe7the RUE10transmits207′ to the relay node16. Similar holds true for the LUE11which can be seen in text at subframes3and7that it transmits to the eNB12in both of those subframes. The RUE10transmission207′ to the relay node16at subframe7is done without the RUE's knowledge of the relay node16, as the RUE10assumes it's transmitting to the eNB12. The can be done simply by the eNB12allocating PRBs for the RUE-relay node link26and indicating to the relay node16in which subframe it is scheduled to receive PUSCH packets on these PRBs from the RUE10. Likewise, the eNB12also indicates to the RUE10these subframe and PRBs to use for transmission on the PUSCH packets, but there is no need for the eNB12to inform the RUE10that it will effectively transmit to the relay node16. This mechanism allows backward-compatibility of Rel.8 terminals on the UL.

Companion to the above description of the relay-transmission modes are two alternative relay-aided HARQ procedures, detailed by way of example below. In one procedure, synchronous non-adaptive HARQ is used for concurrent transmission (e.g., in mode C), where in the relay-aided transmission the eNB12re-sends its packets in a pre-determined fashion with the relay node16. In this relay-aided HARQ approach, the eNB12and the relay node16get an ACK/NACK response that the UE10sends on the PUCCH. The relay node16forwards the ACK/NACK from the UE10to the eNB12. Using the specific example atFIG. 2, the eNB12and the relay node16receive the ACK/NACK response202′ and207′ in respective subframes2and7that is sent on the PUCCH by the UE10. The relay node16forwards203′ and208′ in respective subframes3and8the ACK/NACK that it received202′ and207′ from the UE10in respective subframes2and7to the eNB12. As the RN-RUE link26is more reliable than the eNB-RUE link20, the eNB12will always trust the ACK/NACK forwarded by the relay node16, as it is assumed to be more reliable. So if the eNB12receives the ACK/NACK from the UE10directly (in subframes2and7of theFIG. 2example) as well as the relayed ACK/NACK from the relay node16(in subframes3and8of theFIG. 2example), the case where there is a reception or decoding error is avoided because the eNB12relies on the ACK/NACK that it received from the relay node16. This method improves PUCCH coverage for relay-assisted transmission on the UL.

In the alternate relay-aided HARQ procedure, asynchronous adaptive HARQ is used for concurrent transmission (mode C), where the eNB12will coordinate with the relay node16and then send agreed resources to the UE10for transmission, before the eNB12and the relay node16do their concurrent transmissions to the UE10. In this relay-aided HARQ method, two variations are presented. First: the eNB12receives the ACK/NACK response sent on the PUCCH by the UE10to determine if the eNB12needs to re-transmit its packets to the UE10(this takes into account relay-aided PDSCH reception at the UE10). Then the relay node16does not interpret the PUCCH and thus does not forward the ACK/NACK from the UE10to the eNB12. The eNB12indicates to the relay node16that the relay node16will re-transmit the packets to the UE10, and indicate the resources to be used for that concurrent transmission. In this case, the relay node16will always follow the relay-configured control-signaling message (i.e. sent on the PDCCH) from the eNB12to the relay node16. In the second variation: the relay node16receives and interprets the PUSCH, and forwards the ACK/NACK from the UE10to the eNB12. Note that the PUSCH may carry the ACK/NACK from the UE in case UE needs to acknowledge packets sent on the PDSCH while transmitting packets on the PUSCH on the UL. Using the structure ofFIG. 2again as an example, the eNB12receives on the PUCCH in subframes3and8the ACK/NACK response203,208from the UE10, and from those received ACK/NACKs determines if it needs to re-transmit the packet. This takes into account relay-aided PDSCH reception at the UE10. The eNB12indicates to the relay node16that it will re-transmit the packet to the UE10and indicates200,205, in respective subframes0and5, the radio resources to be used for that concurrent transmission. As above, the eNB12will trust the ACK/NACK forwarded by the relay node12. In terms of the ACK/NACK information from the relay node16, the eNB12will indicate to the relay node16that it will re-transmit the packets to the UE10and the eNB12will indicate to the relay node16the resources to be used for the concurrent transmission. In this case, the resource allocation signaling from eNB12to the relay node16will always override the ACK/NACK in the relay node16.

In a variation on the above HARQ procedures, the first-described HARQ procedure can be re-used as well if the relay node16interprets the PUCCH and forwards the ACK/NACK to the eNB12.

The synchronous non-adaptive HARQ procedure outlined above for concurrent transmission requires standardization in the relay node16and in the eNB12, but is transparent to the UE10. Specifically for the example shown atFIG. 2, the eNB12needs to schedule the PUCCH for the RUE10in subframe7so the RUE10can indicate its ACK/NACK response207′ for the packets the eNB and RN sent on the PDSCH in subframe4(204and204′), and schedules the PUCCH for the RUE in subframe2so the RUE can indicate its ACK/NACK for packets sent in subframe9of the previous radio frame (similar to transmissions209and209′ in the illustrated radio frame220). The relay node16decodes and forwards the PUCCH to the eNB12in this HARQ embodiment. So for example the ACK/NACK received202′ at the RN in subframe2is relayed203′ by the RN to the eNB in subframe3, and the ACK/NACK received207′ at the RN in subframe7is relayed208′ by the RN to the eNB in subframe8. In this manner the eNB12may schedule the PUSCH in subframes2and7(first transmission), and/or subframes3and8(relay-aided re-transmission) for the RUE10. The table below summarizes the issues with PUCCH coverage in case a PUCCH decoding error results in an erroneous ACK/NACK detection. For example, assume the UE10sends an ACK response, but the eNB12detects a NACK response and the relay node16detects an ACK response. Absent the relay node16forwarding the correct ACK response to the eNB12, the eNB12would schedule re-transmission of the packet without the help of the relay node, and the re-transmission may then also fail. On the other hand, if the relay node16forwards the ACK response to the eNB12, and the eNB trusts the forwarded ACK response when there is a conflict with its own decoded ACK/NACK response for the same packet then there is no need for re-transmission, and the eNB12may schedule transmission of a new packet instead of wasting resources scheduling a re-transmission.

The asynchronous adaptive HARQ procedure outlined above for concurrent transmission requires standardization in the relay node16and in the eNB12, but is transparent to the UE10also. The eNB12needs to schedule the PUCCH for the RUE10in subframes3and8to indicate its ACK/NACK response203,208for packets sent204to that UE on the PDSCH in subframe4and in subframe9of the previous radio frame. In one embodiment for this asynchronous adaptive HARQ approach, the relay node16does not decode the PUCCH and does not forward the ACK/NACK it didn't decode to the eNB12. The eNB12may schedule the PUSCH in subframes2and7(first transmission), and/or subframes3and8(relay-aided re-transmission) for the RUE10. In another embodiment for this asynchronous adaptive HARQ approach, the procedure can be the same as the non-adaptive HARQ case detailed above if the relay node16will interpret the PUCCH and forward the ACK/NACK it receives to the eNB12.

The table below summarizes the above HARQ processes.

ProblemUEeNBRNif RN doesn't forwardstatusstatusstatusACK/NACKAction in eNB & RNACKACKACKNoRN sends ACK to eNB.NACKACKRN won't do retransmission-->E-NB will stopthe weak signal from eNBretransmission andcan not securestart new transmission.retransmission. Theretransmission performancecannot be guaranteedNACKNACKExtra retransmissionsRN sends NACK toACKNACKRN will do retransmission buteNB.eNB will re-allocate thisRN and eNB will followresource to other user-->NACK and doserious resource collisionconcurrentmay take place --> the QoStransmission.of two users can not beguaranteedNACKACKACKNo retransmissionsRN sends ACK to eNB.NACKACKRN won't do retransmission.E-NB will stopThe weak signal from eNBretransmission andcan not secure furtherstart new transmission.retransmission.NACKNACKNoRN sends NACK toACKNACKRN will do retransmission buteNB.eNB will re-allocate thisRN and eNB will followresource to other user-->NACK and doserious resource collisionconcurrentmay take place--> the QoS oftransmission.two users can not beguaranteed

In one particular embodiment of the invention, the relay node16may also be used in the first transmission (prior to any ACK/NACK from the UE10). This implies that the relay node16knows which resource to use to send data to the UE10and has received the packet to forward to the RUE on the PDSCH from the eNB. The eNB12sends the PDCCH to the UE10and both the eNB12and the relay node16sends the PDSCH to the UE12concurrently. At the same time, the eNB12sends a relay-configured control-signaling message to the relay node16indicating the resources to be used for the next concurrent transmission of a packet.

Now are detailed examples of the relay-transmission modes without beamforming. In this example the relay-transmission modes are the same as modes A, B and C noted above, but mode C is used for cooperative diversity. In the UE10, channel estimation is done on the DRS, so under mode C the UE estimates the combined channel for the eNB-UE link20and the relay-UE link26(like two main paths) and in mode B the UE10estimates only the channel for the relay node—UE link26. In both cases the channel estimation is done using the DRS the UE10receives. In mode A, the CRSs are used to estimate the channel for the eNB-UE link20. These channel estimates in the various modes are then used to demodulate and decode the PDSCH, which is transmitted to the RUE10by the eNB12and/or by the relay node16. In all modes the relay is transparent to the RUE10. The RUE10is only required to know that it has to use DRS or CRS to estimate the channel for PDSCH demodulation and decoding.

CQI computation is a bit different and presented herein are two options to compute CQI. In a first option, any UE10,11may use the DRS for channel estimation over the whole band and compute CQI for its own relay node-UE link26accordingly. The DRS is not beamformed by UE-specific beamforming weights, and hence can effectively be used by any and all of the UEs in the cell that receive it for wideband CQI computation. It is assumed for this first option that the same DRS sequence is used for all UEs by the network/cell. This relay CQI mode will need specification, as it is not specified in LTE Rel. 8.

In a second option, the UE10,11may use the CRS transmitted by the eNB12to compute the wideband CQI. An OLLA mechanism may be used to compensate for the relay gain, as relay-aided transmission to the RUE10will typically experience significantly better SINR levels at the RUE10. The OLLA mechanism simply adds or subtracts a CQI offset based on ACK/NACK rates. This second option is preferred by the inventors at the present time because it does not require standardization; the CQI mechanism specified in LTE Rel. 8 may be used. To switch to or from the relay-transmission modes (B or C) that employ the relay node16, the eNB12may (monitor CQI reported by the UEs10,11which they computed from the CRS they received from the eNB12(in modes B or C) to see if the eNB-RUE link20has sufficiently improved so as to allow a switch to mode A; and/or the eNB12can monitor ACK/NACK reports from the UEs in mode A to see if relay-aided modes B or C need to be switched on.

If a multiple antenna configuration is used in the eNB12and/or in the relay node16, then in an embodiment a simple single-stream transmit-diversity transmission mode can be in use—e.g. a Cyclic Delay diversity technique in which there is a cyclic delay offset (within a cyclic prefix resolution) between each transmit antenna of the same node12,16. Note that the number of transmit antennas12E in the eNB12and in the relay node16may be different.

Synchronization requirements are fairly tight because signals from the eNB12or from the relay node16must arrive at the UE10,11at the right time (e.g., within a cyclic prefix CP resolution). This is a normal signaling consideration and its resolution is well known in the art.

Note that in relay-transmission modes B and C the relay node16transmits the PDSCH, which it receives from the eNB12. In an embodiment the PDSCH is demodulated and decoded in the relay node16before being encoded and modulated with typically a higher data rate (e.g., MCS with higher-order modulation and weaker coding) prior to transmission to the RUE10. This effectively defines a L2-type relay (decode and forward). Another embodiment for the relay node16is as a L1-type relay (amplify and forward), where the PDSCH is simply amplified and forwarded. Such an amplify and forward embodiment is more adapted to the relay node being embodied as a mobile station (though not limited in that regard). Though simpler, the amplify and forward type relay does not remove noise at the relay node and does not take advantage of the better conditions on the RN-RUE link26as compared to the eNB-Rue link20. It is assumed that the relay-aided transmissions in modes B and C can operate at a significantly higher SINR. The eNB12may indicate to the relay node16the MCS scheme to be used for the concurrent eNB12and relay node16transmissions to the RUE10(mode C). The eNB12may base its choice of MCS on the OLLA mechanism, depending on ACK/NACK rates in relay-transmission modes B or C.

Now consider a variation to the above three relay-transmission modes, the differences from those detailed above as follows. The different modes for transmission may be selected in an embodiment based on channel and interference conditions.Mode A′: the eNB12sends the same data to the relay node16and to the UE10.Mode B′: the eNB12and the relay node16each transmit the same data to the UE10.Mode C: the eNB12and the relay node16send the same data to the UE10, and at the same time the eNB12send a next packet (or set of packets) to the relay node16which stores them for later transmission to the UE10.

The above description as to control channels and shared channel and reference signals still applies, but the actual data that is sent on the PDSCH differs in the primed modes A′, B′, and C′ immediately above as compared to those unprimed modes A, B and C originally described. One difference though is that in mode B′ both the eNB12and the relay node16transmit the PSDSCH which carries the data, as opposed to only the relay node16in the originally described unprimed mode B.

According to this embodiment of the invention, detailed with respect toFIG. 3, the different relay-transmission modes are selected in an exemplary embodiment as follows. First, DL transmissions to the UE10are according to transmission modes A and B as shown at block302, based on ACK/NACK from UE. For example, if an ACK is received from the UE10, then the next transmission will be according to relay-transmission mode A′. If instead a NACK is received from the UE10, then the next transmission to it will be according to relay-transmission mode B′. Note that in both modes A′ and B′ the eNB12sends the data to the relay node16, but the relay node16only sends that data over the air interface under relay-transmission mode B′. The mode A′ transfer of the data to the relay node16is not considered a waste of radio resources since DL HARQ mechanism implies re-transmission of the packet using in-band spectrum resources and relay-assisted re-transmission may result in fewer re-transmissions required overall. Consider this individual ACK/NACK decision criteria at block302as a short-term measure of channel quality.

In this embodiment there is also a long term measure of channel quality in that the number of NACKs are accumulated and added. If in a fixed time duration T as shown at block304more than M NACKs are received from the UE10(M being an integer greater than one), then the eNB12will assume the UE10is in a bad channel condition and the relay node16has become necessary. The ‘yes’ option from block304then leads to block306where relay-transmission modes B′ and C′ are used by the eNB12and the relay node16for transmissions to the UE10. Like block302, the changes within block306between relay-transmission modes B′ and C′ are based on the individual ACK/NACK of the last transmission sent to the UE10. Specifically, if an ACK is received from the UE10, then the next transmission will be according to relay-transmission mode B′. If instead a NACK is received from the UE10, then the next transmission to it will be according to relay-transmission mode C′. But the shift between block302which alternates between relay-transmission modes A′ and B′, and block304which alternates between relay-transmission modes B′ and C′, is based on the longer term measure of channel quality that is checked at block304whether there have been at least M NACKs accumulated within the time duration T. In order to account for improved channel conditions, at block308there is a timer with threshold/elapsed time t1which runs once block306is entered. After that elapsed time t1, the signaling returns to block302and the eNB12will try transmission modes A ‘and B’ again, shifting as before based on the short term measure of individual ACK/NACK from UE10. If instead the channel is still degraded, then the NACKs will accumulate and block304will assure the process continues.

Note that in block302, the relay node16is used only for re-transmissions since there mode B′ is only used in response to a NACK. But in block306the relay node16is used directly for first transmissions (not re-transmissions of the same data that was NACK'd) and delay is avoided by allowing transmission mode C′ where the e NB12sends the new data/next packet or set of packets to the relay node16in advance of the time it might be needed. This is so that in each transmission time slot/subframe, relay-aided transmissions can be performed.

The embodiment shown by example atFIG. 3may be used with beamforming, similar to that detailed earlier above except that in this embodiment beamforming is applied at the eNB12to the DRS and PDSCH in mode B′ or C′. With reference also to the subframe examples shown atFIG. 2, the eNB12and the relay node16can transmit the beamformed DRS and PDSCH to the RUE10in sub-frames4and9. The UE10can estimate a combined effective channel based on the DRS it receives. When there is a different antenna configuration at the eNB12as compared to the relay node16, the beamforming matrix size will be different for the eNB12and the relay node16, but seen from the UE10perspective it is simply a combined n-stream transmission. For example, consider the combined signal received at the UE as Y=(H1.P1+H2.P2).X+N, where X is the transmitted signal and N is Gaussian noise. H1is the channel from the eNB12to the UE10(e.g., 2*4 matrix size from 4 transmit antennas) and P1is a 4*1 matrix size, while H2is the channel from the relay node16to the UE10(e.g., 2*2 matrix size from 2 transmit antennas) and P2is a 2*1 matrix size. From the perspective of the UE10, there is only a combined 2*1 channel: He=(H1.P1+H2.P2).

With the DRS, the UE10need not know the antenna configuration of the eNB12or the relay node16, it need only to know the number of streams. In the example, there is only one stream, and it is beamformed.

Again with reference toFIG. 2, multiple input-multiple output MIMO mode may be used for the eNB-LUE link31or for the eNB-relay node link36in subframes0and5to increase data rates. It can be assumed that these links benefit from a relatively high SINR, as the LUE11does not require relay-aided transmission, and the eNB-relay node links36can be planned in the network where they are fixed (wired) links.

In summary, the various embodiments presented by example above enable transparent relays in a backward-compatible way with LTE TDD Rel.8 terminals. Synchronization and mobility procedures specified in Rel.8 may be used by the UE10with the proposed TDD relay frame structure and mapping of common and shared signaling. The exemplary mechanisms detailed above for switching on or off relay-aided transmission (e.g., switching among the relay-transmission modes) enables enhancements to PDSCH coverage and capacity.

So according to an embodiment of the invention and as shown atFIG. 4there is an apparatus (e.g., the eNB or a component thereof), a memory embodying a program of computer readable instructions directed to switching relay-transmission modes that when executed by a processor perform actions, and a method that includes at block402ofFIG. 4transmitting to a user equipment, in a first subframe of a radio frame, a common reference signal on a downlink shared channel with no dedicated reference signal according to a first relay-transmission mode (e.g., mode A or A′), at block404switching to a second relay-transmission mode (e.g., mode C or C′) within the radio frame based on a channel quality (e.g., CQI received from the UE which is based on the CRS, ACK/NACK received from the UE or M ACK/NACKs received from the UE within a time period T) of the downlink shared channel, and after switching, at block406transmitting to the user equipment, in a subsequent subframe of the same radio frame, a dedicated reference signal on the downlink shared channel according to the second relay-transmission mode.

Individual ones or combinations of the below aspects may be employed with the above apparatus, memory and method according to further embodiments and variations as detailed above. In one aspect, for both modes A and B the eNB transmits control channels (P-BCH, PDCCH and PHICH) with a CRS and also transmits the shared channel (PDSCH) with a CRS in mode A but transmits the shared channel (PDSCH) with a DRS in mode C. In mode A the relay node does not transmit to the UE and in mode C the relay node transmits the DRS with the PDSCH to the UE.

In another aspect, there is a third mode B in which the eNB transmits the control channels with the CRS and does not transmit any DRS or the PDSCH; the relay node transmits the PDSCH with a DRS to the UE.

In another aspect is a method, memory storing a program and an apparatus that is configured to transmit to a user equipment, in a first subframe of a radio frame, a common reference signal on a downlink shared channel (with or without the DRS) according to a first relay-transmission mode (e.g., mode A or A′), to switch to a second relay-transmission mode (e.g., mode C or C′) within the radio frame based on a channel quality of the downlink shared channel, and after switching, to transmit to the user equipment, in a subsequent subframe of the same radio frame, a dedicated reference signal on the downlink shared channel according to the second relay-transmission mode, but wherein in mode C the eNB and relay node can transmit beamformed DRS and PDSCH to the RUE10concurrently. In another aspect they are not beamformed but simply transmitted concurrently in mode C. In all cases of the relay node transmitting the PDSCH and DRS, the eNB schedules the relay node for that transmitting since in some cases it is concurrent and/or beamformed using UE-specific beamforming weights.

In another aspect the eNB transmits the DRS via antenna port5, transmits the CRS on the control channels via antenna ports0and1, and transmits the DRS via antenna ports0,1,2and3.

In another aspect the eNB transmits in mode A in a MIMO mode and in mode C in a non-MIMO mode.

In another aspect is a method, a memory storing a program and an apparatus that is configured to transmit to a user equipment, in a first subframe of a radio frame, a downlink shared channel (with or without the DRS) according to a first relay-transmission mode (e.g., mode A or A′), to switch to a second relay-transmission mode (e.g., mode C or C′) within the radio frame based on a channel quality of the downlink shared channel, and after switching, to transmit to the user equipment, in a subsequent subframe of the same radio frame, the downlink shared channel according to the second relay-transmission mode, but wherein in mode C the eNB indicates to the relay node which modulation and coding scheme the relay node is to use for its transmissions to the UE (which can also occur in mode B). The eNB may select the MCS based on outer loop link adaptation based on ACK/NACK rates. The CRS/DRS distinction may or may not be present in embodiments according to this aspect of the invention.

In another aspect the channel quality on which the switching between first and second (and third, mode B) relay-transmission modes is based comprises the UE's ACK/NACK reports sent on the PUCCH, which may be received from the UE directly or relayed from the relay node. The basis may be a longer term decision criteria such as M NACKs received within a time duration T, and a shorter term criteria (each individual ACK/NACK) may be used to switch among mode pairs A′ and B′ and to switch among mode pairs B′ and C′ while the longer term criteria is used to switch between mode pairs.

In another aspect is a method, a memory storing a program and an apparatus that is configured to transmit to a user equipment, in a first subframe of a radio frame, a downlink shared channel (with or without the DRS) according to a first relay-transmission mode (e.g., mode A or A′), to switch to a second relay-transmission mode (e.g., mode C or C′) within the radio frame based on a channel quality of the downlink shared channel, and after switching, to transmit to the user equipment, in a subsequent subframe of the same radio frame, the downlink shared channel according to the second relay-transmission mode, but in this embodiment the channel quality on which the switching between first and second (and third, mode B) relay-transmission modes is based comprises the UE's CQI reports, which like the ACK/NACK implementation above may be received directly from the UE or received from the relay node which relays the CQI reports to the eNB. It is noted that in mode A the CQI reports will be based on the CRS sent with the PDSCH whereas in mode C the CQI reports will be based on the DRS sent with the PDSCH. Switching from mode A to mode B or C may be based on the reported CQI value remaining below a threshold CQI value for a time duration t1, and switching back may be based on the may be based on the reported CQI value exceeding a threshold CQI value for a time duration (the thresholds and time durations may be identical but may also differ from one another).

In another aspect is a method, a memory storing a program and an apparatus that is configured to transmit to a user equipment, in a first subframe of a radio frame, a common reference signal on a downlink shared channel (with or without the DRS) according to a first relay-transmission mode (e.g., mode A or A′), to switch to a second relay-transmission mode (e.g., mode C or C′) within the radio frame based on a channel quality of the downlink shared channel, and after switching, to transmit to the user equipment, in a subsequent subframe of the same radio frame, a dedicated reference signal in the downlink shared channel according to the second relay-transmission mode, but unlike certain variations above in this case beamformed transmission of the DRS is not needed. The UE's reported CQI is wideband and the same DRS is used for all UEs in the cell. For the case that the UE's CQI report is based on the CRS (e.g., mode A), the UE's CQI report will also be wideband so long as the relay gain in mode B is compensated, such as by an OLLA mechanism.

In another aspect a combination of the UE's ACK/NACK reports and the UE's CQI reports are used as the channel quality on which the switching between relay-transmission modes is based.

In an embodiment is a method, a memory storing a program and an apparatus that is configured to transmit to a user equipment in a first subframe of a radio frame a downlink shared channel according to a first relay-transmission mode (e.g., mode A or A′), to switch to a second relay-transmission mode (e.g., mode C or C′) within the radio frame based on a channel quality of the downlink shared channel, and after switching, to transmit to the user equipment, in a subsequent subframe of the same radio frame, the downlink shared channel according to the second relay-transmission mode. In this embodiment the HARQ process is synchronous and non-adaptive for mode C, in which the eNB re-transmits packets to the UE in a predetermined fashion so as to be concurrent with transmission of those same packets from the relay, as scheduled by the eNB. In this embodiment the eNB receives the UE's NACK for the data that is to be re-transmitted via relay through the relay node.

In another embodiment, is a method, a memory storing a program and an apparatus that is configured to transmit to a user equipment in a first subframe of a radio frame a downlink shared channel according to a first relay-transmission mode (e.g., mode A or A′), to switch to a second relay-transmission mode (e.g., mode C or C′) within the radio frame based on a channel quality of the downlink shared channel, and after switching, to transmit to the user equipment, in a subsequent subframe of the same radio frame, the downlink shared channel according to the second relay-transmission mode. In this embodiment the HARQ process is asynchronous and adaptive for mode C, and the eNB receives the UE's NACK directly from the UE. The eNB indicates to the relay node that there is to be a packet re-transmission and radio resources (e.g., subframe) on which it is to occur such as on the PDCCH, and the eNB and the relay node concurrently transmit the NACK'd packet to the UE. Or in another variation the UE's NACK is relayed to the eNB from the relay node which receives it on the PUCCH. Or in another variation the UE's NACK is relayed to the eNB from the relay node which receives it on the PUSCH if the UE is transmitting on the UL. In all instances of these HARQ variations the eNB schedules the PUCCH or PUSCH on which the UE sends its ACK/NACK to the packets that the eNB and/or relay node sent in the PDSCH, which of course the eNB schedules the PDSCH in the first place. The CRS/DRS distinction may or may not be present in embodiments according to this aspect of the invention.

In another aspect, in mode A′ the eNB sends the same data to the UE and to the relay node but the relay node only sends it to the UE if there is a NACK from the UE; and in mode C′ the eNB and the relay node send the same data to the UE and the eNB additionally sends to the relay node further data for the UE, which the relay node stores for later transmission to the UE if a NACK is received from the UE. There is also a third mode B′ in which the eNB and the relay node both transmit the same data to the UE, but this mode is reserved for the instances above where the UE's NACK is received and the data sent represents a retransmission of data sent earlier by the eNB to the UE.

For the aspects of this invention related to eNB12, embodiments of this invention may be implemented by computer software executable by a data processor of the eNB12, such as the processor12A shown, or by hardware, or by a combination of software and hardware.

For the aspects of this invention related to the relay node16, embodiments of this invention may be implemented by computer software executable by a data processor of the relay node16, such as the processor shown for it atFIG. 1B, or by hardware, or by a combination of software and hardware. Further in this regard it should be noted that the various logical step descriptions above may represent program steps, or interconnected logic circuits, blocks and functions, or a combination of program steps and logic circuits, blocks and functions.

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. However, any and all modifications of the teachings of this invention will still fall within the scope of the non-limiting embodiments of this invention.

Although described in the context of particular embodiments, it will be apparent to those skilled in the art that a number of modifications and various changes to these teachings may occur. Thus, while the invention has been particularly shown and described with respect to one or more embodiments thereof, it will be understood by those skilled in the art that certain modifications or changes may be made therein without departing from the scope of the invention as set forth above, or from the scope of the ensuing claims.