WO2013166689A1

WO2013166689A1 - Harq-ack transmissions for dynamic tdd ul/dl configuration

Info

Publication number: WO2013166689A1
Application number: PCT/CN2012/075304
Authority: WO
Inventors: Haipeng Lei; Kodo Shu; Yuanrong Lan; Chunhai Yao; Jiezhen Lin
Original assignee: Nokia Corporation; Nokia Siemens Networks Oy
Priority date: 2012-05-10
Filing date: 2012-05-10
Publication date: 2013-11-14

Abstract

Acknowledgements, negative acknowledgements and discontinuous transmission indications for a concatenation window that spans a plurality of subframes are concatenated into a compiled uplink message, which is then mapped the uplink message to a fixed subframe regardless of the uplink and downlink subframe configuration of the concatenation window. In one example each radio frame has ten subframes and the concatenation window spans subframe 9 of radio frame N-1 through subframe 8 of radio frame N, and the fixed subframe is subframe 2 of radio frame N+l. In other examples the plurality of subframes span a length less than one radio frame, or a length equal to N radio frames (N>1). In further examples the downlink assignment index is re-defined to indicate the PUCCH resource in the fixed subframe, and/or to indicate whether or not multiple PDSCHs are allocated in the concatenation window.

Description

HARQ-ACK TRANSMISSIONS FOR DYNAMIC TDD UL/DL

CONFIGURATION

TECHNICAL FIELD:

[0001] The exemplary and non-limiting embodiments of this invention relate generally to wireless communication systems, methods, devices and computer programs and, more specifically relate to signaling feedback when the uplink/downlink configuration is dynamically changeable.

BACKGROUND:

[0002] In the evolved universal terrestrial radio access network (E-UTRAN, also known as long term evolution LTE) the user terminals (generally user equipments UEs) are allocated radio resources for uplink (UL) and downlink (DL) data over a physical downlink control channel (PDCCH). This has proven to be a spectrum efficient technique and the general principle is used in other radio access technologies (RATs) such as the contention free period of wireless local area networks (WLAN, generally the IEEE 802.1 1 family of standards). [0003] In order to save on unnecessary control signaling, the feedback (acknowledgement ACK or negative acknowledgement NACK) for the scheduled data which is carried on the physical downlink shared channel PDSCH or physical uplink shared channel (PUSCH) is mapped to later subframes according to a pre-arranged mapping. So for example, in case of TDD UL/DL configuration 1 , if the PDCCH grants to a UE a PDSCH in subframe 9 (subframes indexed 0 through 9), the UE will send its ACK/NACK for that PDSCH in subframe 3 of the next radio frame and the network access node (eNB in LTE) knows to look there for the ACK/NACK without any explicit control signaling to coordinate the mapping. [0004] The radio frame configuration of DL and UL subframes in LTE is semi-statically changeable to account for different traffic needs. Currently the UL/DL configuration in LTE is signaled in system information, so is able to be changed only every 640 ms. Matching the UL/DL configuration dynamically to what the current traffic needs for UL and DL resources would improve throughput. But changing the UL/DL configuration potentially each radio frame would disrupt the above ACK/NACK mapping; in the above example subframe 3 of the next radio frame may not be a UL subframe if the UL/DL configuration for that frame has been dynamically changed.

[0005] What is needed in the art is a way to enable hybrid automatic repeat request (HARQ) signaling such as the above ACK/NACK feedback when the UL/DL configuration can change dynamically in every one or few radio frames.

SUMMARY:

[0006] According to a first exemplary aspect the invention there is a method comprising: concatenating all acknowledgements and negative acknowledgements and discontinuous transmission indications for a concatenation window into a compiled uplink message, where the concatenation window spans a plurality of subframes; and mapping the uplink message to a fixed subframe regardless of the uplink and downlink subframe configuration of the concatenation window. [0007] According to a second exemplary aspect the invention there is an apparatus comprising: at least one processor and at least one memory including computer program code. In this aspect the at least one memory and the computer program code are configured, with the at least one processor and in response to execution of the computer program code, to cause the apparatus to perform at least: concatenating all acknowledgements and negative acknowledgements and discontinuous transmission indications for a concatenation window into a compiled uplink message, where the concatenation window spans a plurality of subframes; and mapping the uplink message to a fixed subframe regardless of the uplink and downlink subframe configuration of the concatenation window.

[0008] According to a third exemplary aspect the invention there is a computer readable memory storing a program of instructions which when executed by at least one processor result in actions comprising: concatenating all acknowledgements and negative acknowledgements and discontinuous transmission indications for a concatenation window into a compiled uplink message, where the concatenation window spans a plurality of subframes; and mapping the uplink message to a fixed subframe regardless of the uplink and downlink subframe configuration of the concatenation window.

[0009] These and other aspects are detailed further below.

BRIEF DESCRIPTION OF THE DRAWINGS:

[0010] Figure 1 is a prior art table showing the seven different TDD UL/DL configurations for LTE that are subject to semi-static configuration.

[0011] Figure 2 illustrates a unified radio frame structure that follows from Figure 1 but with flexible frames F that may be configured for uplink or downlink by the network.

[0012] Figures 3A-B are examples of how unworkable is HARQ timing in conventional LTE if dynamic UL/DL subframe configurations would be implemented. [0013] Figure 4 is an illustration of a radio environment with two cells/eNBs and two UEs illustrating that power control is also unworkable in conventional LTE if dynamic UL/DL subframe configurations would be implemented.

[0014] Figure 5 is similar to Figures 3A-B but illustrating a HARQ-ACK mapping technique according to an exemplary embodiment of these teachings.

[0015] Figure 6 is a process flow diagram from the perspective of a user equipment UE that illustrates a method, and a result of execution by one or more processors of a set of computer program instructions embodied on a computer readable memory, in accordance with the exemplary embodiments of this invention,

[0016] Figure 7 is a simplified block diagram of a UE and a network access node/eNB which are exemplary electronic devices suitable for use in practicing the exemplary embodiments of the invention.

DETAILED DESCRIPTION:

[0017] To further demonstrate advantages of the teachings which are detailed more particularly below, consider the specific problem is the LTE system were to adopt dynamic UL/DL configuration as is anticipated for the LTE-Advanced system now under development (beyond Release 1 1), rather than the semi-static configuration now in practice.

[0018] Figure 1 shows the different time division duplex (TDD) asymmetric UL/DL allocations for a radio frame that are currently available for semi-static configuration in the LTE system. The current UL/DL configuration is signalled in system information block 1 (SIB-1) meaning it can be changed no more frequently than every 640 ms. Dynamically changing the TDD UL/DL configuration can also be employed in pico/micro cells for offloading traffic from a macro cell, and is further proposed for a LTE -Hi research project in China.

[0019] It has been demonstrated that the cell average packet throughput can be much improved when the TDD reconfiguration period is set to 10ms as compared to using a fixed TDD UL/DL configuration. Faster TDD UL/DL reconfiguration shows especially better performance when the traffic load is light or medium; a 10 ms switching period (the length/duration of a LTE radio frame) for dynamically changing the TDD UL/DL configuration outperforms a system with a switching period of 640ms and even 200ms. But the current LTE mechanism for changing the UL/DL configuration is not adaptable to switch more frequently than 640 ms,

[0020] Figure 2 illustrates a unified frame structure which follows from the seven fixed configurations shown at Figure 1. In the radio frame shown at Figure 2 subframe 0, 1 , 5 and 6 are always used for downlink transmission (switching subframes S can be used for downlink), and also subframe 2 is always used for uplink transmission. The other subframes, 3, 4, 7, 8 and 9 are flexible subframes which can be used for downlink or uplink. The specific transmission direction is dependent on the TDD UL/DL configuration selected by the eNB.

[0021] Figures 3 A-B illustrate radio frames that show problems with HARQ signaling if dynamic TDD UL/DL reconfiguration is directly adopted in a Pico cell, Femto cell, LTE-Hi cell even in a macro cell in the LTE system. In the Figure 3A example the TDD UL/DL configuration 1 is used in the first radio frame and is changed to configuration 2 in the next. If the UE receives a PDSCH in DL subframe 9, it is obliged by conventional LTE HARQ timing rules to transmit the corresponding ACK/NACK on PUCCH in UL subframe 3 in the next radio frame. But as shown at Figure 3A subframe 3 is a DL subframe where TDD UL/DL configuration 2 is used, so the UE cannot send its UL HARQ feedback.

[0022] Figure 3B is another example of a HARQ timing conflict if dynamic UL/DL subframe configuration were employed in conventional LTE. In this example the first radio frame is TDD UL/DL configuration 2 and is dynamically changed to configuration 1 in the next radio frame. If a UE receives a PDSCH in DL subframe 9 in the first radio frame, by the LTE HARQ timing rules it will map its ACK/NACK to subframe 7 in the next radio frame. But in the Figure 3B example that subframe 7 is where the ACK/NACK for DL subframe 0 and 1 of that same next radio frame is to map. In this example there would be a resource collision in the ACK/NACK signaling on the physical uplink control channel (PUCCH).

[0023] In addition to the above problems with extending conventional LTE HARQ timing to dynamic UL/DL configuration, such a change can may cause severe UL-DL interference in the conflicting subframes due to independent and different TDD UL/DL configurations in neighboring cells. This may be manifested in eNB-to-eNB interference and in UE-to-UE interference, shown by example at Figure 4. This type of coexistence UL-DL interference has a significant impact on UL signal to interference plus noise ratio (SINR) when the eNBs are located in line-of-sight (LOS), or located close to each other. Or there may be coexistence interference that impacts the DL SINR when the UEs are located near the cell edge as shown in Figure 4. As a result, if ACK/NACK feedback is transmitted on the conflicting subframes, this UL-DL interference may decrease the reliability of HARQ feedback which will then degrade the system performance and prevent realizing benefits of dynamic TDD UL/DL reconfiguration in the first place.

[0024] There is a further consideration for dynamic changes to the UL/DL configuration. Since the channel conditions in flexible subframes are dynamic, which is what results in the dynamically changing UL/DL configuration, then accumulated and persistent power adjustment for uplink transmission will be necessary. For example, in conventional LTE Release 10 for PUCCH format 3 transmission, only transmit power control (TPC) bits with a downlink assignment index (DAI) equal to 1 is used for uplink transmission power adjustment, while other TPC with DAI greater than 1 are used to determine the PUCCH resource. That means the current TPC cannot adapt to the dynamic UL-DL interference in flexible subframes. The conventional uplink power control is not sufficiently adapted for dynamic UL/DL configuration changes.

[0025] From the above, the inventors have determined that new timing rules when the TDD UL/DL configuration is dynamically changed is not the best path forward, especially for the case of very fast TDD UL/DL reconfiguration (for example, 10ms switching scale), While it might appear a simple solution would be to re-map the HARQ timing, the reliability of ACK/NACK is also a problem needs to be solved.

[0026] 3 GPP TS 36.213 specifies the HARQ timing for LTE Release 8 as follows:

For TDD, the UE shall upon detection of a PDSCH transmission or a PDCCH indicating downlink SPS release within subframe(s) n -k , where k e K and K is defined in Table 10.1-1 intended for the UE and for which ACK/NACK response shall be provided, transmit the ACK/NACK response in UL sub frame n. [0027] Table 10.1-1 below, reproduced from the above 3GPP reference, gives the downlink association set index

for TDD:

[0028] Currently in actual deployments all the neighboring cells use the same TDD UL/DL configuration to avoid the UL-DL interference noted above with reference to Figure 4. Otherwise, there is no interference mitigation scheme in conventional LTE to address dynamically changing the TDD UL/DL configuration such as inter-cell eNB-to-eNB and UE-to-UE interferences.

[0029] Other known interference mitigation schemes are not seen effective for the above problem. One such scheme is enhanced inter-cell interference coordination elCIC. In this technique the macro eNB for example imposes on itself an almost blank subframe ABSF, in which it transmits only minimal control information such as synchronization signals and common reference signals. Coordinating this ABSF with a pico/micro cell on the same carrier enables the pico/micro cell to transmit (or schedule UL transmissions from its own UEs) without interference from the macro cell. Since the ABSF would be unavailable for data, if the eNB selects TDD configurations with extra DL subframes to compensate for this, the DL resource loss would only shift the throughput degradation to the UL.

[0030] To solve the above problems, whether in the LTE system as demonstrated above or in other RATs that use resource scheduling of DL and UL subframes whose positions can be changed on a relatively frequent basis, below is detailed a HARQ-ACK feedback scheme for dynamic TDD UL/DL configuration of which exemplary embodiments exhibit the following characteristics: UE generates the ACK/NACK bits corresponding to each subframe from subframe x in the current radio frame (N) to subframe x-\ in the next radio frame (N+l) and concatenates them. The variable* represents a subframe number/index selected from 0-9 for this example. For individual subframes within that set which are UL, or subframes in which no DL PDCCH is received or no semi-persistent scheduling (SPS) PDSCH is received, the ACK/NACK bits for those subframes are mapped to the UE's discontinuous transmission (DTX) status. In each of those three cases the UE does not receive a PDSCH or PDCCH indicating DL SPS release, so the feedback bit (which would be a NACK/DTX indication) for those individual subframes are mapped as DTX. Thus the bits that are concatenated together with the ACK/NACK bits for other DL subframes within a given window in the order of increasing subframe index. Since typically the DTX indication is combined with a NACK, the term ACK/NACK hereafter also includes DTX unless otherwise stated. In this 10-subframes per radio frame example, this means there would be generated 10 ACK/NACK bits in the UE's single-codeword transmission mode or in its two-codeword transmission mode with spatial bundling, or there would be generated 20 ACK/NACK bits in the UE's two-codeword transmission mode without spatial bundling. These generated ACK/NACK bits are then transmitted in subframe 2 in the radio frame (N+2) by PUCCH format 3. Subframe 2 is chosen for these examples because in Figure 2 it is always a UL subframe regardless of the change of TDD UL/DL configuration, but in other implementations some other subframe that is predefined to always be UL may be selected. This choice leads to the 'next subframe' characterization above, but more generically the chosen always-UL subframe will follow the concatenation window which spans from one radio frame [subframe x to (x-1) above]; if for example subframe 7 were an always UL subframe and selected for sending the concatenated ACK/NACK it would be in the same radio frame as the latter part of the radio frame window. In the example embodiment of x=0, ACK/NACK bits from subframe 0 to subframe 9 in frame N is concatenated, and transmitted in subframe 2 in radio frame N+l . • DAI fields in the PDCCH assigned for the scheduled PDSCH or PDCCH that indicates SPS release, and which are sent from subframe x in the current radio frame to subframe x- 1 in the next radio frame, are used to indicate the PUCCH resource value from one of the four resource values configured by higher layers.

^■ TPC fields in the PDCCH assigned for the scheduled PDSCH or PDCCH that indicate SPS release, and which are sent from subframe x in the current radio frame to subframe x-l in the next radio frame, are used to indicate the accumulated and persistent power adjustment for the UE's PUCCH transmission of the concatenated ACK/NACK codeword(s).

- Upon detection of PDSCH transmissions as well as PDCCH indicating DL SPS release from subframe x in the current radio frame to subframe x-l in next radio frame, whose ACK/NACK response are transmitted in subframe 2 in the next radio frame, UE shall transmit the generated A/N bits by

PUCCH format 3 on the PUCCH resource indicated by DAI.

- Upon no detection of a PDSCH transmissions or of a PDCCH that indicates DL SPS release, and which are between subframe x in the current radio frame and subframe x- 1 in the next radio frame, the UE shall not transmit its

(concatenated) ACK/NACK in subframe 2 of the next radio frame.

[0031] Figure 5 illustrates generally similar to Figures 3A-B but for the HARQ-ACK timing according to these teachings, with x=9 meaning the concatenation window 502 includes subframe x=9 and extends to subframe (9-l)=8 of the next radio frame. Each radio frame in Figure 5 is illustrated identically to the unified frame of Figure 2, and it is assumed that for Figure 5 there is a dynamic reconfiguration so at least one of the flexible F subframes change from one radio frame to the next subsequent one though even if there is no change the HARQ arrangement and timing still operates the same.

[0032] For the example of Figure 5, assume that somewhere in the concatenation window 502 the UE detects a PDSCH, or a PDCCH indicating that the DL SPS is released, with explicit timing and reliable transmission. The UE will concatenate ACK or NACK or DTX bits for all ten subframes in the window 502; there may be only one PDSCH to ACK/NACK, or only one PDCCH indicating SPS release to ACK/NACK, or more than either or both of those, or some combination of PDSCHs and PDCCH indicating SPS releases.

[0033] However many ACK/NACK bits there are, the UE concatenates them into a codeword, maps that concatenation window 502 to a fixed sub frame following the window 502 (which is the always-UL subframe #2 in this example), and sends the codeword in that mapped UL subframe #2 as PUCCH format 3 (in this case). The UE sends that PUCCH with the transmit power indicated by the TPC bits in the PDCCH that assigned for the PDSCHs or indicating the SPS release. These TPC bits are cumulative, so for example two scheduling PDCCHs have two TPC bits for this UE in two subframes which are both +1 steps to transmit power, the UE will increase its transmit power for the corresponding PUCCH by +2 steps as compared to the last PUCCH it sent.

[0034] One significant advantage here is that the UE's HARQ procedure does not require the eNB or UE to change its mapping for the PUCCH based on what if any change there is in the UL/DL configuration between radio frames. In the above example the specific change of TDD UL/DL configuration between radio frames, or even whether or not there was a change, is not relevant to the actions which the UE takes respecting its HARQ timing. In this manner the throughput advantage which is the promise of dynamic TDD reconfiguration can be achieved.

[0035] Refer again to Figure 5. For the subframes within the window which are UL subframes, or in which no DL PDCCH is received or no SPS PDSCH is received, ACK/NACK bits for those subframes are mapped to DTX. In this way, 10 ACK/NACK bits are generated in the UE's single-codeword transmission mode (i.e., TM 1 , 2, 5, 6 or 7 in the LTE system) or two -codeword transmission mode after spatial bundling or 20 ACK/NACK bits in the two-codeword transmission mode (i.e., TM 3, 4, 8 or 9). [0036] As noted above, the exact position of the concatenation window can be different from those shown at Figure 5. For example, ACK/NACK bits corresponding to subframe 8 in frame N-l to subframe 7 in frame N can also be concatenated in that order and then the feedback is sent in subframe 2 in frame N+1. As another example of a different window position, ACK/NACK bits corresponding to subframe 7 in frame N-l to subframe 6 in frame N can also be concatenated in order and then the HARQ feedback is signaled in subframe 2 in frame N+1. As a further example, ACK/NACK bits corresponding to subframe 0 to subframe 9 in frame N can be sent in UL subframe 2 in frame N+1 by PUCCH format 3, In other embodiments which do not follow the unified frame structure shown at Figure 2 the HARQ feedback can be in some subframe other than subframe #2, but preferably the HARQ feedback subframe is fixed, meaning it is a UL subframe for all of the possible UL/DL configurations (an always-UL subframe). If 3ms processing delay is allowed, another example of a different window position, ACK/NACK bits corresponding to subframe 0 in frame N to subframe 9 in frame N can also be concatenated in order and then the HARQ feedback is signaled in subframe 2 in frame N+1. In the Figure 5 example the concatenation from subframe 9 to subframe 8 is chosen due to the minimum HARQ feedback delay; any smaller would not allow sufficient processing time (under current assumptions) for the UE to generate the codewords and compile the PUCCH it needs to send.

[0037] While Figure 5 illustrates the concatenation window spanning a plurality of subframes whose length exactly equals one radio frame (ten subframes in this case), in other embodiments the size of the concatenation window can be different. If for example the only UL/DL configurations were #s 0, 1, 2 and 6 shown at Figure 1 A, then there would be two always-UL subframes, namely subframe #2 and subframe #7. In this instance an embodiment of these teachings can utilize two different concatenation windows per every ten consecutive subframes. If we assume again a 3ms processing delay for the UE to compile its uplink message before sending its PUCCH, a first concatenation window might span subframes 4-8 of frame N and map to fixed UL subframe 2 of frame N+1 , while simultaneously a second concatenation window might span subframe 9 of frame N to subframe 3 of frame N+1 and map to fixed UL subframe 7 of frame N+1. [0038] As another example, the concatenation window can also span the length of some multiple of one radio frame, such as 20 subframes. As a specific example of this, the PUCCH which the UE sends in fixed subframe #2 of frame N+l has concatenated ACKs/NACKs for subframe 9 of frame N-2 to subframe 8 of subframe N. This can be stated more generally as the concatenation window spans a plurality of subframes whose length is equal to 7 radio frames, where 7 is an integer greater than one.

[0039] In the Figure 5 example it was also assumed the HARQ feedback would be in PUCCH format 3. Since PUCCH format 3 needs an explicit and reliable resource indication, the DAI fields in the PDCCH that schedules the PDSCH(s) or in the PDCCH that indicates the SPS release (within the window from subframe 9 in frame N-1 to subframe 8 in frame N) are reused to indicate the PUCCH resource value from one of the four resource values which are configured by higher layers. After decoding the PDCCH, the UE shall know the resource for the PUCCH format 3 transmission. But if there is only one PUSCH scheduled in the mapped subframe the PUSCH can carry the concatenated ACK/NACK bits in order to preserve the single carrier property. Combining those two means that the feedback is carried by PUCCH format 3 or by PUSCH if there is only one PUSCH in the subframe. [0040] If more than one PDCCH schedules within the same concatenation window, the same DAI for indicating the PUCCH resource may be transmitted on all PDCCHs that schedule PDSCH(s) or that indicate SPS release between subframe 9 and subframe 8 in the next radio frame. In order to allow for a high correlation in the time domain in a local area network due to low mobility by the UE, one DL grant (PDCCH) may schedule multiple DL subframes (PDSCH). In that example scenario, some DAIs sent from subframe 9 to subframe 8 may be used to indicate whether multiple DL subframes are scheduled together or not.

[0041] Power Control: Since channel conditions in flexible subframes are assumed to be dynamic due to the dynamic change of the TDD UL/DL configuration, accumulated and persistent power adjustment for uplink transmission are warranted. In conventional LTE Release 10 for PUCCH format 3 transmission, only TPC with DAI=1 is used for uplink transmission power adjustment while other TPC with DAI>1 are used to determine the PUCCH resource. This conventional power control is not adaptable to the dynamic UL-DL interference in flexible subframes. Furthermore, if a PDCCH with DAI=1 is missed by the UE, then the UE will not obtain the closed-loop uplink transmission power adjustment command from the eNB, which would likely results in the severe interference to the UE or eNB in neighboring cells as shown in Figure 4.

[0042] According to these teachings in the LTE context, all TPC fields in the PDCCH that are used for scheduling a PDSCH for a UE or for indicating SPS release to a UE that are sent from subframe 9 to subframe 8 in the next radio frame are used to indicate the accumulated and persistent power adjustment for PUCCH transmission. This power adjustment can persistently adjust the UE's transmission power to adapt to some extent to the dynamic interference variation in flexible subframes. And so as noted above the generated ACK/NACK bits shall then be transmitted in subframe 2 by PUCCH format 3 on the indicated resource in the uplink with the persistent transmit power adjustment.

[0043] For the case in which the UE does not detect, from subframe 9 to subframe 8 in the next radio frame, any PDSCH transmissions or any PDCCH indicating DL SPS release, the UE shall not transmit any ACK/NACK in subframe 2,

[0044] In the above examples it was detailed that the UE will generate 10 or 20 ACK/NACK bits for its PUCCH codeword. These are only non-limiting examples; in another LTE deployment the UE can instead generate 9 or 18 ACK/NACK bits for single-codeword or two-codeword transmission mode by excluding the unnecessary ACK/NACK feedback for uplink subframe 2 that lies within its concatenation window, since in these examples subframe 2 is always uplink and thus would never have an associated ACK/NACK bit for the UE to transmit. [0045] Among the technical effects of these teachings, they solve the HARQ timing problem detailed above for LTE due to dynamic TDD UL/DL configuration, since all the ACK/NACK bits for all subframes spanning the duration of a frame are transmitted in one fixed subframe (subframe 2) which is always the uplink transmission direction. Another technical effect is. that since subframe 2 in the above examples is always used for uplink, there is no UL-DL interference in this subframe which means the ACK/NACK transmitted in subframe 2 can guarantee the reliability of ACK/NACK feedback. Additionally, since PUCCH format 3 adopts an explicit resource indication, there is no PUCCH resource collision issue in the above examples, an important issue for enabling dynamic TDD UL/DL reconfiguration in a practical system. Reusing the DAI in all PDCCH as the PUCCH resource indication can guarantee the reliability of resource indication. [0046] A further technical effect of the HARQ feedback scheme detailed by example above is that it enables the eNB to change the TDD UL/DL configuration to match the instantaneous traffic variation in UL and DL for traffic adaptation, while also avoiding frequent indications of the change of TDD UL/DL configuration to the UE. The UE can then decode the indication that the TDD UL/DL configuration has changed, and thereby avoid a problem of a false alarm (the UE thinks the configuration has changed but the eNB has not changed it or vice versa). From the UE implementation point of view, UE complexity can be reduced which is a common concern since the UE has lesser processing capacity and limited battery power as compared to the eNB. These teachings therefore enable a much shorter period for switching the UL/DL configuration than is currently possible in conventional LTE, and for example support a switching period of as short as one radio frame (10 ms in LTE).

[0047] In a practical deployment of these teachings in an LTE network there may be some legacy UEs coexisting with UEs that are not able to switch the UL/DL configuration more often than 640 ms. In this case there might be an issue with the legacy UEs. For example, if a UE is configured as TDD UL/DL configuration 2 it may be scheduled for DL transmission on subframe 3, 4, 7, 8 or 9. A legacy UE may regard that other UE's UL signals as a downlink common reference signal (CRS). This can be resolved by restricting the measurement by the legacy UE of its reference signal received power (RSRP) on the flexible subframes, or alternatively the eNB can indicate to the legacy UE that the flexible subframes are configured as ABSFs to prevent it from measuring its RSRP there. [0048] Some of the above principles of these teachings are summarized with reference to the process flow diagram of Figure 6, which shows internal processes of the UE 10. The various steps and messages summarized in Figure 6 may be viewed as method steps, and/or as operations that result from operation of computer program code embodied on a memory and executed by a processor, and/or as a plurality of coupled logic circuit elements constructed to carry out the associated function(s).

[0049] At block 602 of Figure 6 the UE concatenates all acknowledgements and negative acknowledgements and discontinuous transmission indications for a concatenation window into a compiled uplink message. The concatenation window spans a plurality of subframes. In compiling the uplink message the UE may convert the ACK/NACK bits into one or more codewords as detailed more particularly above. Then at block 604 the UE maps the uplink message to a fixed subframe regardless of the uplink and downlink subframe configuration of the concatenation window.

[0050] Further portions of Figure 6 summarize some of the more particular aspects of the above examples and are not limiting to the broader teachings herein. Block 606 tells that the plurality of subframes that define the concatenation window span a length equal to exactly one radio frame, which follows from the example at Figure 5 in which it spanned subframe 9 of radio frame N-l through subframe 8 of radio frame N, and the fixed subframe is subframe 2 of radio frame N+l (where N is an integer and each radio frame has ten subframes indexed from 0 through 9). In other examples the plurality of subframes span a length less than one radio frame, or a length that is some integer multiple Y of radio frames.

[0051] Block 608 summarizes the mapping of block 604 further includes mapping to a physical uplink resource of the fixed subframe which is identified by a downlink assignment index DAI in a PDCCH that allocates either a physical downlink shared channel or a release of a semi persistent resource allocation.

[0052] And finally block 610 summarizes the above power control examples, where transmit power is determined for the uplink message based at least in part on a power adjustment command (e.g., TPC bit or bits) received in the PDCCH mentioned in block 608.

[0053] For any subframes of the concatenation window that are characterized as a) an uplink subframe or b) a downlink subframe for which there is no downlink resources allocated to the user equipment or no PDCCH indicating the release of a semi-persistent resource allocation, the UE generates a DTX bit (or bits) for the relevant subframe for the UE's concatenating shown at block 602. [0054] Reference is made to Figure 7 for illustrating a simplified block diagram of various electronic devices and apparatus that are suitable for use in practicing the exemplary embodiments of this invention. In Figure 7 a wireless network is adapted for communication over a wireless link 15 with an apparatus, such as a mobile communication device which above is referred to as a UE 10, via a network access node such as a Node B (base station), and more specifically an eNB 20. The network may include a network control element (NCE) 22 that may include mobility management entity/serving gateway MME/S-GW functionality that is specified for LTE/LTE- Advanced. The NCE 22 also provides connectivity with a different network, such as a publicly switched telephone network and/or a data communications network (e.g., the Internet). While only one wireless link 15 is shown in an embodiment it represents multiple logical and physical channels.

[0055] The UE 10 includes a controller, such as a computer or a data processor (DP) 10A, a computer-readable memory medium embodied as a memory (MEM) 10B that stores a program of computer instructions (PROG) IOC, and a suitable radio frequency (RF) transmitter and receiver 10D for bidirectional wireless communications with the eNB 20 via one or more antennas (two shown). The UE 10 may have one or more than one radios 10D for communicating with the eNB 20. While only one eNB is shown the UE 10 may also be in communication with a micro/pico eNB, or the illustrated eNB may be a pico/micro eNB or a macro eNB as is known in the LTE/LTE- Advanced systems.

[0056] The eNB 20 also includes a controller, such as a computer or a data processor (DP) 20A, a computer-readable memory medium embodied as a memory (MEM) 20B that stores a program of computer instructions (PROG) 20C, and suitable RF transmitters and receivers (two shown as 20D) for communication with the UE 10 via one or more antennas (also two shown). The eNB 20 is coupled via a data / control path 30 to the NCE 22. The path 30 may be implemented as the SI interface known in the E-UTRAN system. If embodied as a macro eNB, the eNB 20 may also be coupled to a micro/pico eNB and/or another macro eNB in a different cell via another data / control path which may be implemented as the X2 interface known in the E-UTRAN system. [0057] At least one of the PROGs IOC and 20C is assumed to include program instructions that, when executed by the associated DP, enable the device to operate in accordance with the exemplary embodiments of this invention, as detailed above. That is, the exemplary embodiments of this invention may be implemented at least in part by computer software executable by the DP 1 OA of the UE 10 and/or by the DP 20A of the eNB 20, or by hardware, or by a combination of software and hardware (and firmware).

[0058] For the purposes of describing the exemplary embodiments of this invention the eNB 20 may be assumed to also include a program or algorithm to cause the eNB 20 to detect from received uplink signaling a concatenated ACK/NACK for subframes in a concatenation window and to map the concatenated ACKs/NACKs to subframes of that concatenation window to determine whether or not re-transmissions are needed to the UE, as shown at as shown at the PROG 20G. Further the UE 10 includes a program or algorithm to cause the UE 10 to concatenate all the ACKs/NACKs for subframes in a concatenation window and compile them into an uplink message, which the UE then maps to the PUCCH for signaling uplink to the eNB as shown at PROG 10G according to the non-limiting examples presented above.

[0059] In general, the various embodiments of the UE 10 can include, but are not limited to, cellular telephones, personal digital assistants (PDAs) having wireless communication capabilities, portable computers having wireless communication capabilities, image capture devices such as digital cameras having wireless communication capabilities, gaming devices having wireless communication capabilities, music storage and playback appliances having wireless communication capabilities, Internet appliances permitting wireless Internet access and browsing, as well as portable units or terminals that incorporate combinations of such functions.

[00601 The computer readable MEMs 10B and 20B 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, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The DPs 10A and 20 A 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) and processors based on a multicore processor architecture, as non-limiting examples.

[0061] In general, the various exemplary embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in embodied firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto. While various aspects of the exemplary embodiments of this invention may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, embodied software and/or firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof, where general purpose elements may be made special purpose by embodied executable software.

[0062] It should thus be appreciated that at least some aspects of the exemplary embodiments of the inventions may be practiced in various components such as integrated circuit chips and modules, and that the exemplary embodiments of this invention may be realized in an apparatus that is embodied as an integrated circuit. The integrated circuit, or circuits, may comprise circuitry (as well as possibly firmware) for embodying at least one or more of a data processor or data processors, a digital signal processor or processors, baseband circuitry and radio frequency circuitry that are configurable so as to operate in accordance with the exemplary embodiments of this invention,

[0063] While the exemplary embodiments have been described above in the context of the E-UTRAN system, it should be appreciated that the exemplary embodiments of this invention are not limited for use with only this one particular type of wireless communication system that uses resource allocations for scheduling data.

[0064] Furthermore, some of the features of the various non-limiting and exemplary embodiments of this invention may be used to advantage without the corresponding use of other features. As such, the foregoing description should be considered as merely illustrative of the principles, teachings and exemplary embodiments of this invention, and not in limitation thereof.

Claims

WHAT IS CLAIMED IS:

1. A method comprising:

concatenating all acknowledgements and negative acknowledgements and discontinuous transmission indications for a concatenation window into a compiled uplink message, where the concatenation window spans a plurality of subframes; and mapping the uplink message to a fixed subframe regardless of the uplink and downlink subframe configuration of the concatenation window.

2. The method according to claim 1 , in which the plurality of subframes span a length equal to exactly one radio frame.

3. The method according to claim 2, in which the concatenation window spans subframe 9 of radio frame N-l through subframe 8 of radio frame N, and the fixed subfram e is subframe 2 of radio frame N+ 1 , where N is an integer and each radio frame has ten subframes indexed from 0 through 9.

4. The method according to claim 1, in which the plurality of subframes span a length less than one radio frame.

5. The method according to claim 1, in which the plurality of subframes span a length equal to Y radio frames, where 7 is an integer greater than one.

6. The method according to any one of claims 1 through 5, in which the mapping further comprises mapping to a physical uplink resource of the fixed subframe which is identified by a downlink assignment index in a physical downlink control channel that allocates either:

a physical downlink shared channel; or

a release of a semi persistent resource allocation,

7. The method according to claim 6, further comprising:

determining transmit power for the uplink message based at least in part on an power adjustment command received in the physical downlink control channel.

8. The method according to any one of claims 1 through 7, in which the concatenating comprises:

generating a discontinuous transmission indication for each subframe of the concatenation window which is an uplink subframe or a downlink subframe for which no downlink resource is allocated to a user equipment executing the method nor an indication of semi-persistent scheduling release.

9. The method according to any one of claims 1 through 8, in which the method is performed by a user equipment operating in an E-UTRAN system.

10. The method according to claim 9, further comprising:

determining from a downlink assignment index received in a physical downlink control channel whether or not multiple downlink subframes in the concatenation window are allocated together to the user equipment.

1 1. An apparatus comprising:

at least one processor; and

at least one memory including computer program code,

in which the at least one memory and the computer program code are configured, with the at least one processor and in response to execution of the computer program code, to cause the apparatus to perform at least:

12. The apparatus according to claim 11 , in which the plurality of subframes span a length equal to exactly one radio frame.

13. The apparatus according to claim 12, in which the concatenation window spans subframe 9 of radio frame N-1 through subframe 8 of radio frame N, and the fixed subframe is subframe 2 of radio frame N+1 , where N is an integer and each radio frame has ten subframes indexed from 0 through 9.

14, The apparatus according to claim 1 1 , in which the plurality of subframes span a length less than one radio frame.

15. The apparatus according to claim 1 1 , in which the plurality of subframes span a length equal to Y radio frames, where Fis an integer greater than one.

16. The apparatus according to any one of claims 1 1 through 15, in which the mapping further comprises mapping to a physical uplink resource of the fixed subframe which is identified by a downlink assignment index in a physical downlink control channel that allocates either:

a physical downlink shared channel; or

a release of a semi persistent resource allocation.

17. The apparatus according to claim 16 in which the at least one memory and the computer program code are configured with the at least one processor to cause the apparatus to further perform:

determining transmit power for the uplink message based at least in part on an power indication received in the physical downlink control channel.

18. The apparatus according to any one of claims 11 through 17, in which the concatenating comprises;

19. The apparatus according to any one of claims 11 through 18, in which the apparatus comprises a user equipment operating in an E-UTRAN system, or one or more components of said user equipment.

20. The apparatus according to claim 19, in which the at least one memory and the computer program code are configured with the at least one processor to cause the user equipment to further perform:

21. A computer readable memory storing a program of instructions which when executed by at least one processor result in actions comprising:

22. The computer readable memory according to claim 21 , in which the plurality of subframes span a length equal to exactly one radio frame.

23. The computer readable memory according to claim 22, in which the concatenation window spans subframe 9 of radio frame N-1 through subframe 8 of radio frame N, and the fixed subframe is subframe 2 of radio frame N+l, where N is an integer and each radio frame has ten subframes indexed from 0 through 9.