Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W28/00—Network traffic management; Network resource management
  • H04W28/02—Traffic management, e.g. flow control or congestion control
  • H04W28/06—Optimizing the usage of the radio link, e.g. header compression, information sizing, discarding information
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W72/00—Local resource management
  • H04W72/20—Control channels or signalling for resource management
  • H04W72/21—Control channels or signalling for resource management in the uplink direction of a wireless link, i.e. towards the network

Definitions

• 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.
• E-UTRAN also known as long term evolution LTE
• UEs user terminals
• UL uplink
• DL downlink
• PDCCH physical downlink control channel
• 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.
• 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.
• the network access node eNB in LTE
• the radio frame configuration of DL and UL subframes in LTE is semi-statically changeable to account for different traffic needs.
• 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.
• 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.
• 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.
• an apparatus comprising: at least one processor and at least one memory including computer program code.
• 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.
• 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.
• Figure 1 is a prior art table showing the seven different TDD UL/DL configurations for LTE that are subject to semi-static configuration.
• 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.
• Figures 3A-B are examples of how unworkable is HARQ timing in conventional LTE if dynamic UL/DL subframe configurations would be implemented.
• 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.
• Figure 5 is similar to Figures 3A-B but illustrating a HARQ-ACK mapping technique according to an exemplary embodiment of these teachings.
• FIG. 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,
• 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.
• FIG. 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.
• SIB-1 system information block 1
• 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.
• 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.
• the current LTE mechanism for changing the UL/DL configuration is not adaptable to switch more frequently than 640 ms,
• Figure 2 illustrates a unified frame structure which follows from the seven fixed configurations shown at Figure 1.
• 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.
• FIGs 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.
• 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.
• Figure 3B is another example of a HARQ timing conflict if dynamic UL/DL subframe configuration were employed in conventional LTE.
• 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).
• PUCCH physical uplink control channel
• 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.
• TPC transmit power control
• DAI downlink assignment index
• 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.
• Table 10.1-1 below reproduced from the above 3GPP reference, gives the downlink association set index for TDD:
• inter-cell interference coordination elCIC enhanced inter-cell interference coordination
• 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.
• 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.
• the ACK/NACK bits for those subframes are mapped to the UE's discontinuous transmission (DTX) status.
• DTX discontinuous transmission
• 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.
• ACK/NACK 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.
• 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).
• UE 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
• the UE 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
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• the throughput advantage which is the promise of dynamic TDD reconfiguration can be achieved.
• ACK/NACK bits for those subframes are mapped to DTX.
• 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).
• the exact position of the concatenation window can be different from those shown at Figure 5.
• 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.
• 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.
• 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,
• 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.
• Figure 5 illustrates the concatenation window spanning a plurality of subframes whose length exactly equals one radio frame (ten subframes in this case)
• 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.
• a first concatenation window might span subframes 4-8 of frame N and map to fixed UL subframe 2 of frame N+1
• 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.
• the concatenation window can also span the length of some multiple of one radio frame, such as 20 subframes.
• 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.
• the concatenation window spans a plurality of subframes whose length is equal to 7 radio frames, where 7 is an integer greater than one.
• 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.
• the UE 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.
• 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.
• one DL grant may schedule multiple DL subframes (PDSCH).
• some DAIs sent from subframe 9 to subframe 8 may be used to indicate whether multiple DL subframes are scheduled together or not.
• 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.
• 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.
• the UE shall not transmit any ACK/NACK in subframe 2
• 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.
• 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).
• 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).
• 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).
• CRS downlink common reference signal
• 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.
• the UE may convert the ACK/NACK bits into one or more codewords as detailed more particularly above.
• the UE maps the uplink message to a fixed subframe regardless of the uplink and downlink subframe configuration of the concatenation window.
• 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).
• the plurality of subframes span a length less than one radio frame, or a length that is some integer multiple Y of radio frames.
• 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.
• 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.
• a power adjustment command e.g., TPC bit or bits
• the UE 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.
• Figure 7 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.
• 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.
• 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.
• 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.
• 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.
• 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).
• 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.
• 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.
• 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.
• PDAs personal digital assistants
• 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.
• 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.
• the various exemplary embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof.
• 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.
• 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,

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Cited By (10)

Citations (6)

• 2012
  • 2012-05-10 WO PCT/CN2012/075304 patent/WO2013166689A1/fr not_active Ceased

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