Classifications

• • 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

• fast buffer status reporting may be relevant to third generation partnership project (3 GPP) long term evolution advanced (LTE- Advanced) technology beyond release 11 (Rel-11). More specifically, fast buffer status reporting may be application to LTE time division duplex (TDD) and may provide further enhancement for traffic adaptation and uplink-downlink (UL-DL) interference management.
• 3 GPP third generation partnership project
• LTE- Advanced long term evolution advanced
• Rel-11 release 11
• fast buffer status reporting may be application to LTE time division duplex (TDD) and may provide further enhancement for traffic adaptation and uplink-downlink (UL-DL) interference management.
• TDD time division duplex
• LTE TDD allows for asymmetric UL-DL allocations by providing seven different semi-statically configured TDD UL-DL configurations shown in Figure 1. These allocations may provide between 40% and 90% DL subframes.
• Current mechanism for adapting UL-DL allocation is based on the system information change procedure with 640ms period.
• the concrete TDD UL/DL configuration is semi-statically informed by SIB-1 signaling.
• Dynamic TDD UL/DL reconfiguration is a feature for various communication systems, which permit dynamic TDD UL/DL reconfiguration in a TDD system to match uplink and downlink traffic variation.
• TDD reconfiguration period is set to 10ms compared to fixed TDD UL/DL configurations.
• faster TDD UL/DL reconfiguration may provide better performance, especially in case of low or medium cell traffic load.
• dynamic TDD UL/DL configuration with a 10ms switching scale may outperform configurations with 200ms or 640ms switching scales.
• TDD UL/DL configuration is switched every 10ms.
• the eNB selects the most appropriate DL-UL subframe ratio based on the relative instantaneous amount of total downlink and uplink traffic waiting for the scheduling in the eNB.
• eNB is usually assumed to always ideally know this instantaneous traffic amount of DL and UL available in the cell without any delay and error.
• eNB may only ideally know the traffic amount of DL waiting for scheduling, since the DL buffer is terminated at eNB side.
• the UE may report this UL amount available to eNB in order to request enough resources to transmit this UL traffic.
• this UE behavior is called buffer status reporting. Throughout this description, buffer status reporting is used as one example of this behavior, although other types of related behavior are not excluded.
• the buffer status report conventionally may be a control element of medium access control (MAC) layer, which is used to report the amount of data available in a UE logic buffer for eNB UL scheduling.
• the BSR may conventionally be transmitted only on PUSCH and may be terminated at MAC layer, specifically in the node where PUSCH is received.
• the BSR may be transinitted either periodically or given conditions at the UE being fulfilled. Since BSR is transmitted on PUSCH, an UL grant is conventionally always needed to schedule a PUSCH for BSR transmission.
• FIG. 2 illustrates current LTE uplink scheduling procedures.
• a UE may need to request uplink resources for data transmission.
• the UE may send the scheduling request (SR) by PUCCH format 1 or physical random access channel (PRACH) for the contention-based uplink resource request, if certain conditions for the SR are fulfilled.
• the eNB may allocate some PUSCH resources for sending BSR by means of a UL grant to the UE. Then, the UE may transmit the amount of data available in a logic buffer on a scheduled PUSCH to the eNB for UL resources requesting, together with a very limited amount of UL traffic.
• SR scheduling request
• PRACH physical random access channel
• the eNB may allocate corresponding UL resources by means of an UL grant to the UE for data transmission, taking the uplink radio condition between the UE and the eNB into account. After that, the UE may transmit uplink data and may receive the corresponding ACK/NACK feedback in a physical hybrid automatic repeat request (HARQ) indicator channel (PHICH) or UL grant contained in PDCCH.
• HARQ physical hybrid automatic repeat request
• Figure 3 illustrates a PUSCH tiniing problem in the case of dynamic TDD UL/DL reconfiguration.
• TDD UL/DL configuration 1 If UE receives a UL grant for BSR transmission in DL subframe 9, it may transmit BSR on corresponding PUSCH in UL subframe 3 in the next radio frame according to currently specified LTE PUSCH transmission timing rules. However, if the current TDD UL/DL configuration is switched to TDD UL/DL configuration 2, to adapt to the traffic fluctuation, then subframe 3 in the next radio frame will be a DL subframe. Thus, the UE cannot transmit BSR in subframe 3 and may need to find another uplink subframe. Hence, further delay may be introduced for BSR reporting.
• the whole UL scheduling procedure may be complicated and lengthy, especially in DL-heavy TDD UL/DL configurations.
• the UE may not timely transmit this BSR information to the eNB, especially in case of DL-heavy TDD UL/DL configuration or UL-heavy traffic flows.
• the current BSR reporting mechanism may not adapt to the fast TDD UL/DL reconfiguration with 10ms switching scale.
• the change of TDD PUSCH timing may introduce further delay to BSR transmission. This may degrade the system performance and limit benefits from dynamic TDD UL/DL reconfiguration for traffic adaptation.
• a method includes detennining an uplink control channel resource to use for signaling a buffer status report.
• the method also includes signaling the buffer status report on a physical uplink control channel.
• a method in certain embodiments, includes signaling a downlink transmission. The method also includes detennining a position of a buffer status report responsive to the downlink transmission.
• an apparatus includes 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 to, with the at least one processor, cause the apparatus at least to deteraiine an uplink control channel resource to use for signaling a buffer status report.
• the at least one memory and the computer program code are also configured to, with the at least one processor, cause the apparatus at least to signal the buffer status report on a physical uplink control channel.
• an apparatus includes 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 to, with the at least one processor, cause the apparatus at least to signal a downlink transmission.
• the at least one memory and the computer program code are also configured to, with the at least one processor, cause the apparatus at least to detennine a position of a buffer status report responsive to the downlink transmission.
• An apparatus includes detennining means for detenriining an uplink control channel resource to use for signaling a buffer status report.
• the apparatus also includes signaling means for signaling the buffer status report on a physical uplink control channel.
• An apparatus in certain embodiments, includes signaling means for signaling a downlink transmission.
• the apparatus also includes deterrnining means for determining a position of a buffer status report responsive to the downlink transmission.
• a non-transitory computer-readable medium is, in certain embodiments, encoded with instructions that, when executed in hardware, perform a process.
• a non-transitory computer-readable medium is, according to certain embodiments, encoded with instructions that, when executed in hardware, perform a process.
• Figure 1 illustrates a current set of seven kinds of TDD UL/DL configurations.
• Figure 2 illustrates current LTE uplink scheduling procedures.
• Figure 3 illustrates a PUSCH timing problem in the case of dynamic
• Figure 4 illustrates a buffer status report transmitted in UpPTS in case of ACK/NACK on UL subframe 2.
• Figure 5 illustrates a buffer status report transmitted in UpPTS in the case of a single OFDM symbol, according to certain embodiments.
• Figure 6 illustrates a buffer status report transmitted in UpPTS in the case of a pair of OFDM symbols, according to certain embodiments.
• Figure 7 illustrates a method according to certain embodiments.
• Figure 8 illustrates another method according to certain embodiments.
• Figure 9 illustrates a system according to certain embodiments.
• a buffer status report may be directly carried on a physical uplink control channel (PUCCH), for example in a physical uplink control channel format 3.
• PUCCH physical uplink control channel
• the particular PUCCH resource of a four high layer signaled resource to be used for this buffer status report may be configured by radio resource control (RRC) signaling or may be predefined with a fixed resource index.
• RRC radio resource control
• the PUCCH format 3 may include several information bits to indicate the amount of uplink (UL) data available in a user equipment (UE) logic buffer.
• UE user equipment
• the particular number of information bits in an implementation may depend on the requirements of granularity. For example, more bits may be used to provide a higher level of granularity, or a smaller number of bits may be used to provide coarser granularity.
• ACK/NACK acknowledgment/negative acknowledgment
• PDSCH physical downlink shared channel
• PDCCH physical downlink control channel
• SPS semi persistent scheduling
• the number of OFDM symbols of UpPTS is 1.
• BSR may be carried in the same PRB index with the PRB carrying ACK/NACK bits in another subframe.
• the demodulation reference signal (DM-RS) of the PUCCH carrying ACK/NACK bits may also be used for eNB to demodulate the modulated BSR symbols.
• DM-RS demodulation reference signal
• BSR may be transmitted in two PRBs with the following PRB index: where m depends on the format of
• the modulated BSR symbols may be divided into two parts and respectively transmitted in the two
• PRBs or repeated in two PRBs for frequency diversity gain.
• the number of OFDM symbols of UpPTS is 2.
• the BSR may be transmitted with one DM-RS for eNode B (eNB) demodulation.
• This DM-RS may be directly inserted in the time domain with the same PRB index with the BSR symbols.
• the BSR may be transmitted with the same structure as in the first case.
• the eNB may determine which UL subframe and which PUCCH resource are to be used to feedback ACK/NACK. The determination may be based on predefined DL HARQ timing. If the subframe is used for ACK/NACK feedback, then there may be no BSR reporting in this subframe. The BSR may be transmitted in the UpPTS of the nearest special subframe with the same PRB index, with the PUCCH carrying ACK/NACK. Thus, misunderstanding regarding the positions of BSR and ACK/NACK between eNB and UE may be avoided.
• the UL traffic amount information may be quickly reported to the eNB for TDD UL/DL configuration determination.
• the data in UE buffer may be transmitted more timely and efficiently.
• a scheduling request (SR) with PUCCH format 1 may be removed or omitted when dynamic TDD UL/DL reconfiguration with fast BSR reporting is used.
• TDD UL/DL configuration may be dynamically changed within a variety of configurations, for example, to match the instantaneous traffic variation in uplink and downlink as well as possible. Therefore, according to the seven configurations approach described above, only subframes 0, 1, 5, 6 are definitely used for downlink transmission and subframe 2 is definitely used for uplink transmission. The other subframes, 3, 4, 7, 8 and 9, are flexible subframes which maybe used for downlink or uplink. The actual transmission direction may be dependent on the TDD UL/DL configuration selected by eNB.
• the UE may send a scheduling request first and then wait for the UL grant.
• the UE cannot send a buffer status report until it receives the UL grant for buffer status report transmission.
• the whole BSR transmission procedure may require a minimum of 8ms after SR transmission. If the delay of SR transmission is considered, the whole procedure may be lengthy, especially in DL-heavy TDD UL/DL configurations due to very limited opportunity for UL transmission. Therefore, the current BSR reporting mechanism may not adapt to the fast TDD UL/DL reconfiguration with 10ms switching scale.
• the change of TDD PUSCH timing may introduce further delay to BSR transmission. This may degrade system performance and limit benefits from dynamic TDD UL/DL reconfiguration for traffic adaptation.
• the UE may transmit BSR on
• PUCCH format 3 if no ACK/NACK is feedback in the same subframe, or otherwise on UpPTS. Such an approach may improve the system performance.
• the UE may transmit the BSR to indicate the amount of UL data waiting for scheduling in the buffer.
• the number of infomiation bits of BSR may be, for example, 6 or 8 which depends on the requirements of granularity.
• ARI ACK/NACK resource mdicator
• BSR reporting may be moved to the UpPTS in the nearest special subframe to maintain the property of single-carrier in uplink.
• the UE may want to transmit BSR in uplink subframe 2 and may find out the UE also needs to transmit ACK/NACK feedback corresponding to scheduled DL subframe from 9 to 8 in uplink subframe 2. If the UE moves the BSR transmission to subframe 2 in the next radio frame, the BSR reports would be delayed 10ms. Moreover, if there are also ACK/NACK feedback in this subframe, UE may have to further delay BSR transmission. [0045] BSR transmission is moved to the UpPTS in special subframe 1, as shown in Figure 4 as an example. This approach may help to maintain single-carrier property in uplink and speed up BSR reporting. Thus, Figure 4 illustrates a buffer status report transmitted in UpPTS in case of ACK/NACK on UL subframe 2.
• the BSR may be earned in the same PRB index, with the PRB carrying ACK/NACK bits in another subframe, in order to reuse the DM-RS of the PUCCH carrying ACK/NACK bits for eNB to demodulate the BSR symbols.
• This approach may be used because there is no room for DM-RS due to the direct inserting of DM-RS in time domain based on the modulation structure of SC-FDMA in uplink.
• Figure 5 therefore, illustrates a buffer status report transmitted in UpPTS in the case of a single OFDM symbol, according to certain embodiments.
• the BSR may be transmitted in two PRBs with the following PRB index: where m depends on the format of
• BSR information bits one example is to use 8 bits for indicating the amount of data in UE buffer. These 8 bits may be modulated to 4 symbols by QPSK, d0, dl, d2 and d3, and then divided into two parts.
• dO dl may be carried on the PRB with index of « PRB 0 and d2 d3 on the PRB with index of "PRB, I ⁇ Allowing for the case that several UEs' PUCCH may be configured in one PRB, BSR transmission in UpPTS may employ multiplexing among different UEs.
• the channel may be configured to support up to five UEs on one PRB by orthogonal cover code (OCC).
• OOCC orthogonal cover code
• the typical user number multiplexing on one PRB may be tliree, in order to lower the mutual interference. Therefore, a PRB carrying a BSR may support up to three users' BSR transmissions.
• FDM frequency division multiplexing
• CDM code division multiplexing
• all four symbols may be carried on one PRB.
• different UEs' BSR transmissions may be assigned to different PRBs in order to simplify the multiplexing issue.
• the BSR may be transmitted with one DM-RS for eNB demodulation.
• This DM-RS may be directly inserted in time domain with the same PRB index with the BSR symbols.
• Figure 6 illustrates a buffer status report transmitted in UpPTS in the case of a pair of OFDM symbols, according to certain embodiments.
• the BSR may be transmitted with the same structure as shown in Figure 5.
• UpPTS since UpPTS may always be used for uplink transmission, the BSR may always be transmitted only in UpPTS. In this case, the number of OFDM symbols of UpPTS may be required to be two, so that one DM-RS may be inserted, as shown in Figure 6.
• eNB may know which UL subframe and which PUCCH resource are to be used to feedback ACK/NACK. If the subframe is used for ACK/NACK feedback, then there is no BSR reporting in this subframe. Thus the BSR may be transmitted in the UpPTS of the nearest special subframe with the same PRB index with the PUCCH carrying ACK/NACK. Accordingly, there may be no misunderstanding on the positions of BSR and ACK/NACK between eNB and UE.
• RACH short random access channel
• DM-RS of PUCCH format may also be used for demodulating BSR.
• Certain embodiments may benefit from dynamic TDD UL/DL reconfiguration. Moreover, certain embodiments may provide for fast BSR reporting for eNB to determine TDD UL/DL configuration, and may provide further improved system performance.
• Figure 7 illustrates a method according to certain embodiments.
• the method of Figure 7 maybe performed by, for example, a user equipment.
• the method may include, at 710, detennining an uplink control channel resource to use for signaling a buffer status report.
• the method may also include, at 720, signaling the buffer status report on a physical uplink control channel, for example in a PUCCH format 3.
• the detennining may include at least one of, at 712, receiving radio resource control signaling or, at 714, referring to a predefined fixed resource index.
• the method may include, at 730, reporting the buffer status report in an uplink pilot time slot of a nearest special subframe.
• the acknowledgment or negative acknowledgment bits may correspond to a physical downlink shared channel or correspond to a physical downlink control channel indicating downlink semi persistent scheduling release.
• modulated buffer status report symbols may be divided, at 740, into two physical resource blocks or may be repeated, at 745, into two physical resource blocks.
• the buffer status report may be signaled, at 750, with one demodulation reference signal.
• Figure 8 illustrates another method according to certain embodiments.
• the method of Figure 8 may be performed by, for example, a base station or eNode B.
• the method may include, at 810, signaling a downlink transmission.
• the downlink transmission may be a physical downlink shared channel or a physical downlink control channel indicating downlink semi persistent scheduling release.
• the method may also include, at 820, determining a position of a buffer status report responsive to the downlink transmission. The determining may be based on a predefined downlink hybrid automatic repeat request timing.
• Figure 9 illustrates a system according to certain embodiments of the invention.
• a system may include several devices, such as, for example, access point 910, which may be an eNode B, and UE 920.
• the system may include more than one UE 920 and more than one access point 910, although only one of each is shown for the purposes of illustration.
• the system may also involve only at least two UEs 920 or only at least two access points 910.
• Each of these devices may include at least one processor, respectively indicated as 914 and 924.
• At least one memory may be provided in each device, and indicated as 915 and 925, respectively.
• the memory may include computer program instructions or computer code contained therein.
• Each device may also include an antenna, respectively illustrated as 917 and 927. Although only one antenna each is shown, many antennas and multiple antenna elements may be provided to each of the devices. Other configurations of these devices, for example, may be provided.
• access point 910 and UE 920 may be additionally configured for wired communication, in addition to wireless communication, and in such a case antennas 917 and 927 may illustrate any form of communication hardware, without being limited to merely an antenna.
• Transceivers 916 and 926 may each, independently, be a transmitter, a receiver, or both a transmitter and a receiver, or a unit or device that may be configured both for transmission and reception.
• Processors 914 and 924 may be embodied by any computational or data processing device, such as a central processing unit (CPU), application specific integrated circuit (ASIC), or comparable device.
• the processors may be implemented as a single controller, or a plurality of controllers or processors.
• Memories 915 and 925 may independently be any suitable storage device, such as a non-transitory computer-readable medium.
• a hard disk drive (HDD), random access memory (RAM), flash memory, or other suitable memory maybe used.
• the memories may be combined on a single integrated circuit as the processor, or may be separate therefrom.
• the computer program instructions may be stored in the memory and which may be processed by the processors may be any suitable form of computer program code, for example, a compiled or interpreted computer program written in any suitable programming language.
• the memory and the computer program instructions may be configured, with the processor for the particular device, to cause a hardware apparatus such as access point 910 and UE 920, to perform any of the processes described above (see, for example, Figures 4-8). Therefore, in certain embodiments, a non-transitory computer-readable medium may be encoded with computer instructions that, when executed in hardware, may perform a process such as one of the processes described herein. Alternatively, certain embodiments of the invention may be perfonned entirely in hardware.
• Figure 9 illustrates a system including an access point 910 and a UE 920
• embodiments of the invention may be applicable to other configurations, and configurations involving additional elements, as illustrated and discussed herein.
• multiple user equipment devices and multiple access points may be present as shown in Figure 1, or other nodes providing similar functionality, such as relays which may receive data from an access point and forward the data to a UE and may implement both functionality of the UE and functionality of the access point.
• PUCCH Physical uplink control channel [0083] PUSCH Physical uplink shared channel

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Cited By (5)

Citations (3)

• 2012
  • 2012-08-01 WO PCT/CN2012/079484 patent/WO2014019161A1/fr not_active Ceased

Patent Citations (3)

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