WO2019041168A1 - Amélioration pour service à faible latence - Google Patents

Amélioration pour service à faible latence Download PDF

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Publication number
WO2019041168A1
WO2019041168A1 PCT/CN2017/099647 CN2017099647W WO2019041168A1 WO 2019041168 A1 WO2019041168 A1 WO 2019041168A1 CN 2017099647 W CN2017099647 W CN 2017099647W WO 2019041168 A1 WO2019041168 A1 WO 2019041168A1
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WIPO (PCT)
Prior art keywords
metric
antenna
harq
codes
bsr
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PCT/CN2017/099647
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English (en)
Inventor
Tom Chin
Ajith Payyappilly
Juan Zhang
Thawatt Gopal
Jiming Guo
Arnaud Meylan
Gaoshan LI
Jie Mao
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Qualcomm Incorporated
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Priority to PCT/CN2017/099647 priority Critical patent/WO2019041168A1/fr
Publication of WO2019041168A1 publication Critical patent/WO2019041168A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
    • H04L1/0033—Systems modifying transmission characteristics according to link quality, e.g. power backoff arrangements specific to the transmitter
    • H04L1/0035—Systems modifying transmission characteristics according to link quality, e.g. power backoff arrangements specific to the transmitter evaluation of received explicit signalling
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
    • H04L1/0023—Systems modifying transmission characteristics according to link quality, e.g. power backoff characterised by the signalling
    • H04L1/0026—Transmission of channel quality indication
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
    • H04L1/1822—Automatic repetition systems, e.g. Van Duuren systems involving configuration of automatic repeat request [ARQ] with parallel processes

Definitions

  • This disclosure relates generally to wireless communication, and more specifically, to enhancement for low latency service.
  • Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power) .
  • multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, and orthogonal frequency division multiple access (OFDMA) systems, (e.g., a Long Term Evolution (LTE) system, or a New Radio (NR) system) .
  • CDMA code division multiple access
  • TDMA time division multiple access
  • FDMA frequency division multiple access
  • OFDMA orthogonal frequency division multiple access
  • LTE Long Term Evolution
  • NR New Radio
  • a wireless multiple-access communications system may include a number of base stations or access network nodes, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE) .
  • UE user equipment
  • a UE may support applications, such as multiplayer gaming applications, social gaming applications, etc., whose quality depends on the latency associated with communications with a base station. In such cases, high latency may result in poor quality for certain applications and low customer satisfaction.
  • a user equipment may determine metrics that may indicate a retransmission delay and thus communication latency.
  • the UE may reduce communication latency, based at least on the determined metrics. For example, to reduce latency, the UE may switch to a better transmit antenna and speed up the antenna switching, report a lower channel quality indicator (CQI) value to receive a lower assigned modulation or coding scheme (MCS) for data transmission, or utilize additional hybrid automatic repeat request (HARQ) process for uplink transmission of same data or control information.
  • CQI channel quality indicator
  • MCS modulation or coding scheme
  • HARQ hybrid automatic repeat request
  • a method of wireless communication may include determine at least one metric indicative of a retransmission delay for a data packet, and reducing communication latency for the data packet, based at least on the determined at least one metric.
  • a UE may include a receiver, a transmitter, and a processor, in connection with the receiver and the transmitter, configured to determine at least one metric indicative of a retransmission delay for a data packet and reduce communication latency for the data packet, based at least on the determined at least one metric.
  • an apparatus of wireless communications may include means for determining at least one metric indicative of a retransmission delay for a data packet, and reducing communication latency for the data packet, based at least on the determined at least one metric.
  • a non-transitory computer-readable medium having instructions stored thereon, the instructions comprising codes executable to cause an apparatus to determine at least one metric indicative of a retransmission delay for a data packet, and reduce communication latency for the data packet, based at least on the determined at least one metric.
  • Some examples of the method, UE, apparatus, or non-transitory computer-readable medium described above may further include features of, means for, or codes for switching from a first antenna to a second antenna, if a second metric is greater than a first latency metric by a switching threshold, and increasing a speed of switching antenna by configuring one or more parameters based on the at least one metric, wherein the at least one metrics comprise the first metric for the first antenna and the second metric for the second antenna.
  • Some examples of the method, UE, apparatus, or non-transitory computer-readable medium described above may further include features of, means for, or codes for measuring a CQI, reporting a lower CQI value than the measured CQI, and receiving an uplink grant assigning a modulation and coding scheme (MCS) in response to the reported lower CQI value.
  • MCS modulation and coding scheme
  • Some examples of the method, UE, apparatus, or non-transitory computer-readable medium described above may further include features of, means for, or codes for transmitting a buffer status report (BSR) on a first hybrid automatic repeat request (HARQ) process, measuring a number of failed HARQ transmissions for the BSR on the first HARQ process, and transmitting the BSR on a second HARQ process, if the number of failed HARQ transmissions is equal to or great than a HARQ transmission threshold.
  • BSR buffer status report
  • HARQ hybrid automatic repeat request
  • FIG. 1 illustrates an example of a wireless communications system 100 that supports enhancement for low latency service in accordance with various aspects of the present disclosure.
  • FIGs. 2-4 illustrate various examples of process flows that support enhancement for low latency service in accordance with various aspects of the present disclosure.
  • FIGs. 5-8 illustrate various examples of methods that support enhancement for low latency service in accordance with various aspects of the present disclosure.
  • FIG. 9 illustrates an example diagram of a wireless device that supports enhancement for low latency in accordance with various aspects of the present disclosure.
  • FIG. 10 illustrates an example of a system including a device that supports enhancement for low latency service in accordance with various aspects of the present disclosure .
  • a UE When a UE is equipped with multiple uplink transmit antennas, it may switch from one antenna to another for uplink transmission when a current antenna is in worse conditions by some threshold based on downlink measurements, e.g., Reference Signal Received Quality (RSRQ) .
  • RSRQ Reference Signal Received Quality
  • the UE may speed up antenna switching to reduce transmission error rate, retransmission delay, and communication latency.
  • a UE may report a Channel Quality Indicator (CQI) based on which a base station may assign a Modulation and Coding Scheme (MCS) for the UE in uplink data transmission.
  • CQI Channel Quality Indicator
  • MCS Modulation and Coding Scheme
  • the UE may report a lower CQI value than the actual measurement and consequently may receive a lower MCS assignment under which the UE may lower error rate and reduce likelihood of retransmission.
  • a UE may send a Buffer Status Report (BSR) for a base station to determine bandwidth allocation for UE uplink data transmission.
  • BSR Buffer Status Report
  • the UE may start BSR transmission on another process of hybrid automatic repeat request (HARQ) in conjunction with a current HARQ process to shorten communication latency due to the delay in the base station receiving the BSR and allocating an uplink grant.
  • HARQ hybrid automatic repeat request
  • FIG. 1 illustrates an example of a wireless communications system 100 that supports enhancement for low latency service in accordance with various aspects of the present disclosure.
  • the wireless communications system 100 includes base stations 105, UEs 115, and a core network 130.
  • the wireless communications system 100 may be a Long Term Evolution (LTE) network, an LTE-Advanced (LTE-A) network, or a New Radio (NR) network.
  • LTE Long Term Evolution
  • LTE-A LTE-Advanced
  • NR New Radio
  • wireless communications system 100 may support enhanced broadband communications, ultra-reliable (e.g., mission critical) communications, low latency communications, or communications with low-cost and low-complexity devices.
  • ultra-reliable e.g., mission critical
  • Base stations 105 may wirelessly communicate with UEs 115 via one or more base station antennas.
  • Base stations 105 described herein may include or may be referred to by those skilled in the art as a base transceiver station, a radio base station, an access point, a radio transceiver, a NodeB, an eNodeB (eNB) , a next-generation Node B or giga-nodeB (either of which may be referred to as a gNB) , a Home NodeB, a Home eNodeB, or some other suitable terminology.
  • Wireless communications system 100 may include base stations 105 of different types (e.g., macro or small cell base stations) .
  • the UEs 115 described herein may be able to communicate with various types of base stations 105 and network equipment including macro eNBs, small cell eNBs, gNBs, relay base stations, and the like.
  • Each base station 105 may be associated with a particular geographic coverage area 110 in which communications with various UEs 115 is supported. Each base station 105 may provide communication coverage for a respective geographic coverage area 110 via communication links 125, and communication links 125 between a base station 105 and a UE 115 may utilize one or more carriers. Communication links 125 shown in wireless communications system 100 may include uplink (UL) transmissions from a UE 115 to a base station 105, or downlink (DL) transmissions, from a base station 105 to a UE 115. Downlink transmissions may also be called forward link transmissions while uplink transmissions may also be called reverse link transmissions.
  • UL uplink
  • DL downlink
  • UEs 115 may be dispersed throughout the wireless communications system 100, and each UE 115 may be stationary or mobile.
  • a UE 115 may also be referred to as a mobile device, a wireless device, a remote device, a handheld device, or a subscriber device, or some other suitable terminology, where the “device” may also be referred to as a unit, a station, a terminal, or a client.
  • a UE 115 may also be a personal electronic device such as a cellular phone, a personal digital assistant (PDA) , a tablet computer, a laptop computer, or a personal computer.
  • PDA personal digital assistant
  • a UE 115 may also refer to a wireless local loop (WLL) station, an Internet of Things (IoT) device, an Internet of Everything (IoE) device, or an MTC device, or the like, which may be implemented in various articles such as appliances, vehicles, meters, or the like.
  • WLL wireless local loop
  • IoT Internet of Things
  • IoE Internet of Everything
  • MTC massive machine type communications
  • Base stations 105 may communicate with the core network 130 and with one another. For example, base stations 105 may interface with the core network 130 through backhaul links 132 (e.g., via an S1 or other interface) . Base stations 105 may communicate with one another over backhaul links 134 (e.g., via an X2 or other interface) either directly (e.g., directly between base stations 105) or indirectly (e.g., via core network 130) .
  • backhaul links 132 e.g., via an S1 or other interface
  • backhaul links 134 e.g., via an X2 or other interface
  • wireless communications system 100 may be a packet-based network that operate according to a layered protocol stack.
  • PDCP Packet Data Convergence Protocol
  • a Radio Link Control (RLC) layer may in some cases perform packet segmentation and reassembly to communicate over logical channels.
  • RLC Radio Link Control
  • a Medium Access Control (MAC) layer may perform priority handling and multiplexing of logical channels into transport channels.
  • the MAC layer may also use hybrid automatic repeat request (HARQ) to provide retransmission at the MAC layer to improve link efficiency.
  • HARQ hybrid automatic repeat request
  • the Radio Resource Control (RRC) protocol layer may provide establishment, configuration, and maintenance of an RRC connection between a UE 115 and a base station 105 or core network 130 supporting radio bearers for user plane data.
  • RRC Radio Resource Control
  • PHY Physical
  • UEs 115 and base stations 105 may support retransmissions of data to increase the likelihood that data is received successfully.
  • HARQ feedback is one technique of increasing the likelihood that data is received correctly over a communication link 125.
  • HARQ may include a combination of error detection (e.g., using a cyclic redundancy check (CRC)) , forward error correction (FEC) , and retransmission (e.g., automatic repeat request (ARQ) ) .
  • FEC forward error correction
  • ARQ automatic repeat request
  • HARQ may improve throughput at the MAC layer in poor radio conditions (e.g., signal-to-noise conditions) .
  • a wireless device may support same-slot HARQ feedback, where the device may provide HARQ feedback in a specific slot for data received in a previous symbol in the slot. In other cases, the device may provide HARQ feedback in a subsequent slot, or according to some other time interval.
  • a transmission time interval may be defined as the smallest unit of time (e.g., a slot or sub-frame) in which a base station 105 may schedule a UE 115 for uplink or downlink transmissions.
  • a base station 105 may allocate one or more TTIs for downlink communication with a UE 115.
  • the UE 115 may then monitor the one or more TTIs to receive downlink signals from the base station 105.
  • a subframe may be the basic unit of scheduling or TTI.
  • Wireless communications system 100 may employ various TTI durations, including those that facilitate ultra-reliable low latency communications (URLLC) and mobile broadband (MBB) communications, in addition to other types of communication associated with LTE and NR.
  • URLLC ultra-reliable low latency communications
  • MBB mobile broadband
  • a UE 115 may experience worsening channel condition or signal quality under which a successful transmission may incur multiple retransmissions of a previously failed transmission due to degradation in error rate performance.
  • the increased retransmission delay can increase the total communication latency despite the short TTI for each transmission or retransmission instance.
  • Further enhancement for low latency service is desired to cope with potentially poor channel condition or signal quality and its varying nature.
  • UE 115 may determine a metric that is indicative of a retransmission delay.
  • such a metric may be based on downlink measurements such as RSRQ on each antenna, a CQI based on reference signal and interference measurement, or a number of transmissions (including retransmissions) on a HARQ process, or some combination thereof.
  • the metric may be a direct measurement of channel or signal quality (e.g., RSRQ or CQI) , or an indirect indicator of error rate or retransmission probability (e.g., a number of failed HARQ transmissions) .
  • UE 115 may reduce latency based on the determined metric by adjusting communication protocols or parameters. For example, it may reduce measurement time constants or thresholds to speed up switching to a better transmit antenna, or report lower than actual CQI values, or employ additional HARQ processes for retransmission.
  • FIG. 2 illustrates an example of a process flow 200 that supports enhancement for low latency service in accordance with various aspects of the present disclosure.
  • UE 115 includes multiple transmit antennas, e.g., antenna 210 and antenna 215.
  • UE 115 may determine at least one metrics for corresponding antennas based on downlink measurements, such as Reference Signal Received Quality (RSRQ) , Reference Signal Received Power (RSRP) , Signal to Noise Ratio (SNR) , Received Signal Strength Indicator (RSSI) , and other measurements, which may measure channel quality.
  • RSRQ Reference Signal Received Quality
  • RSRP Reference Signal Received Power
  • SNR Signal to Noise Ratio
  • RSSI Received Signal Strength Indicator
  • a RSRQ may indicate signal-over-noise quality of downlink reference signal and may be computed as a ratio of average receive power of a downlink reference signal over total receive power on an OFDM symbol that contains the reference signal.
  • downlink measurements on a downlink receive antenna may qualitatively indicate channel quality of a corresponding uplink transmit antenna.
  • relative strength or ranking among downlink receive antennas may indicate a similar or same relative strength or ranking among corresponding uplink transmit antennas.
  • a lower measurement metric may indicate larger retransmission delay and hence larger latency for transmission of a data packet due to larger error rate at a corresponding transmit antenna.
  • a retransmission delay as described herein may refer to or depend on a likelihood of retransmission or a number of retransmissions or their combined effects.
  • UE 115 may compare metrics among different antennas and may switch to another antenna if another antenna’s metric is greater than the current antenna’s latency metric by some switching threshold.
  • UE 115 may switch the antenna if the metric (e.g., RSRQ) of another antenna is more than 6 dB greater than the metric of the current antenna (aswitching threshold of 6dB) .
  • the switching threshold e.g., the 6dB value in the preceding example
  • UE 115 may set a smaller threshold value (e.g., 2dB instead of 6dB) to switch to a better antenna more quickly and thus help reduce retransmission delay and latency.
  • UE 115 may average or filter measurements over multiple time instances, for example, by using a finite impulse response (FIR) or infinite impulse response (IIR) filter.
  • the averaging or filtering operation may have one or more time constants, which may characterize a convergent speed of averaging or filtering.
  • the averaged metric may be updated by linearly combining the current averaged metric with a latest measurement, wherein the time constant of the averaging operation may be a function of one or more coefficients in the linear combination.
  • time constants used in the averaging or filtering operation correspond to faster convergence of an averaged metric to a latest measurement, in which case the averaged metric may adapt faster to changing channel or signal conditions.
  • UE 115 may measure metrics more frequently; higher measurement frequency can enable UE 115 to adapt faster to changing channel or signal conditions.
  • UE 115 may decrease measurement time constants and/or increase measurement frequency, such that UE 115 may respond to changing channel conditions more quickly.
  • UE 115 may adjust the speed of switching based on the determined metric from downlink measurements. For example, if the metric indicates a potentially large latency increase (such as when a recently measured RSRQ has a low value) , UE 115 may reduce switching threshold in large step sizes to cope with potentially worsening channel conditions. Additionally UE 115 may configure the switching parameters (e.g., time constants, switching thresholds) depending on application scenarios or latency requirements. For example, UE 115 may configure faster antenna switching when an application demands more stringent latency requirements.
  • the switching parameters e.g., time constants, switching thresholds
  • Process flow 200 illustrates, as an example, operations of latency reduction in connection with antenna switching.
  • UE 115 uses antenna 210 for uplink transmission (UL TX) and thereafter may continue to measure and evaluate latency metrics (e.g., RSRQ) indicative of retransmission delay for each antenna.
  • Antenna 210 is the current transmit antenna in use (until UE 115 switches to another antenna) .
  • antenna switching is triggered in response to antenna 210’s latency metric being worse than antenna 215’s latency metric by a switching threshold. After the switching, antenna 215 replaces antenna 210 as the current transmit antenna.
  • UE 115 uses antenna 215 to transmit a UL transmission. The switching at 225 may occur before or simultaneously with the transmission at 230.
  • UE 115 may continue to measure and evaluate latency metrics after it has switched antenna. Subsequent switching may not be triggered and antenna 215 may remain as the current transmit antenna. For instance, at 240, antenna 215 is used for another uplink transmission.
  • antenna 210 At 245, however, antenna 210’s latency metric exceeds that of antenna 115 by the switching threshold; UE 115 therefore switches transmit antenna once again from antenna 215 back to antenna 210.
  • antenna 210 is used for uplink transmission.
  • FIG. 3 illustrates an example of a process flow 300 that supports enhancement for low latency service in accordance with various aspects of the present disclosure.
  • UE 115 may measure or evaluate a latency metric, for example, based on quality of communication channels as measured by Channel Quality Indicator (CQI) .
  • CQI Channel Quality Indicator
  • a higher CQI value generally corresponds to better channel quality, lower error rates, and smaller retransmission delay.
  • qualities of downlink and uplink channels are qualitatively similar, for example, when both UL and DL channels exhibit reciprocity in physical channel coefficients or experience similar wireless propagation environments.
  • reducing DL transmission delay may help reduce UL transmission delay and thus overall latency experienced by an end-user. For example, when UE 115 is waiting for some downlink link layer acknowledgment (e.g., an RLC ACK from eNB 105) before sending a next UL data packet, smaller DL transmission delay would help reduce latency in UL data transmission.
  • some downlink link layer acknowledgment e.
  • UE 115 may report a lower CQI value than actually measured CQI so that eNB 105 may assign a lower MCS based on the reported CQI (which has a lower value) .
  • the lower MCS assigned may refer to lower modulation order and/or lower coding rate, which may make transmission more resilient to errors and reduce latency due to retransmission.
  • UE 115, by reporting lower CQI, may trade-off higher communication throughput for better latency performance. The ability to reduce delay may prove very beneficial for low latency service, especially when an application is expected to send data packets of a small size but with a tight delay requirement.
  • Process flow 300 illustrates, as an example, operations of latency reduction in connection with CQI reporting.
  • UE 115 receives from eNB 105 downlink reference signals based on which UE may measure CQI.
  • the reference signals may be Cell-Specific Reference Signals (CRS) , Channel State Information-Reference Signals (CSI-RS) , or some combination thereof.
  • UE 115 may average or filter reference signal measurements in computing CQI values.
  • UE 115 reports a lower CQI value than the actually measured CQI.
  • UE 115 may apply a back-off factor on the measured CQI, that is, the reported CQI would be lower than the measured CQI by certain amount or percentage.
  • the back-off factor may vary according to the measured CQI. For example, UE 115 may apply larger back-off to the measured CQI value to more aggressively cope with worse channel conditions.
  • eNB 105 transmits an UL grant with a lower MCS value in response to receiving a lower reported CQI value from UE 115.
  • the lower MCS may reduce transmission error rate and retransmission delay and hence communication latency.
  • UE 115 transmits uplink data using the lower assigned MCS signaled in the UL grant.
  • the transmission may have lower bit error rate (BER) , which generally reduces likelihood of retransmissions and improves communication latency.
  • eNB 105 may use a lower MCS, corresponding to the lower reported CQI, in downlink data transmission to reduce latency.
  • FIG. 4 illustrates an example of a process flow 400 that supports enhancement for low latency service in accordance with various aspects of the present disclosure.
  • eNB 105 may rely on a Buffer Status Report (BSR) transmitted from UE 115 to determine a bandwidth allocation used for uplink transmission.
  • BSR Buffer Status Report
  • a BSR may contain various information regarding the amount of data waiting to be transmitted by UE 115.
  • a delay in eNB 105’s successful receiving a BSR may delay uplink grants for uplink transmission and thus increase communication latency.
  • a HARQ process may represent a series of time instances (e.g., TTI or subframe indices) during which initial transmissions or subsequent retransmissions may take place.
  • multiple HARQ processes may be interlaced in time, for example, a transmission instance for HARQ process 1 may be followed by one for HARQ process 2, which may be followed by one for HARQ process 3, and so on.
  • multiple HARQ retransmissions may increase communication latency.
  • UE 115 may measure the number of failed HARQ transmissions (including initial transmissions and subsequent retransmissions) , which indicate a retransmission delay (for the HARQ packet being transmitted) . If the number of failed HARQ transmissions of a BSR becomes equal to or greater than a HARQ transmission threshold (which has a minimal value of one, for example) , UE 115 may utilize one or more additional HARQ processes, in conjunction with the existing HARQ process, to transmit the BSR in parallel. The additional HARQ processes may shorten the time gap between successive transmissions and thus may reduce turn-around delay in packet processing. Furthermore, the parallel HARQ processes may also provide repetition gain for eNB 105 to reduce error rate. For example, eNB 105 may combine received packets across different HARQ processes to boost decoding performance.
  • the HARQ transmission threshold may be configured based on other indicators of latency (e.g., a RSRQ or CQI value, as described in FIGs 2-3) . Generally the worse the channel conditions, the smaller the HARQ transmission threshold. Furthermore, the HARQ transmission threshold may also depend on application scenarios or latency requirements. For example, for an application that sends “heart beat” messages, the HARQ transmission threshold can be set to a value of one, such that additional HARQ processes would be used should a BSR packet fails one initial transmission.
  • Process flow 400 illustrates, as an example, operations of latency reduction in connection with additional HARQ processes.
  • UE 115 transmits a BSR to eNB 105 on HARQ process 1.
  • eNB 105 does not successfully receive or decode the BSR packet, and at 420, transmits to UE 115 a HARQ Negative Acknowledgment (NACK) signaling failed HARQ transmission.
  • NACK HARQ Negative Acknowledgment
  • UE 115 retransmits the BSR on the same HARQ process 1, which fails again as eNB sends another HARQ NACK at 440.
  • the HAQR transmission threshold (as denoted by K) is set to 2 and the number of failed BSR transmissions is equal to the threshold. Consequently, at 450, UE 115 starts a BSR transmission on an additional HARQ process 2.
  • a MAC Control Element may contain protocol control information for operating additional HARQ processes.
  • HARQ process 1 may continue to operate in parallel, and at 460, UE 115 retransmits a BSR packet on HARQ process 1.
  • eNB 105 may process each HARQ process separately (such that packets are not combined across different HARQ processes) , or may combine packets across HARQ processes.
  • the increased frequency in HARQ transmission may allow eNB 105 to successfully receive BSR quicker or more reliably.
  • eNB 105 may be aware that the same MAC protocol data unit (PDU) carrying BSR is being transmitted over multiple HARQ processes and may combine soft buffers of received BSR retransmission packets across different HARQ processes.
  • PDU MAC protocol data unit
  • eNB 105 correctly decodes the BSR, either from HARQ process 1 or HARQ process 2 or their combination, and responds with a HARQ ACK acknowledging successful reception of the BSR, and at 480, sends an uplink grant for UE 115 to start uplink data transmission.
  • process flows 200, 300, and 400 may be combined in some implementations and used in the same UE 115.
  • UE 115 may speed up antenna switching in conjunction with reporting lower CQI value and/or transmitting a BSR on additional HARQ processes.
  • FIG. 5 illustrates an example of a method 500 that supports enhancement for low latency service in accordance with various aspects of the present disclosure.
  • the method 500 may encompass various aspects of the example process flow 200, 300, 400 described with reference to FIGs. 2-4.
  • the method 500 may be implemented by a UE 115 or its components as described herein.
  • UE 115 may determine at least one metric indicative of a retransmission delay for a data packet.
  • the at least one metric may be based on measurements (e.g., RSRQ, RSRP, RSSI, SNR) for one or more antennas, a measured CQI on a channel, or a number of failed HARQ transmissions (including retransmissions) .
  • UE 115 may reduce communication latency of the data packet, based at least on the determined at least one metrics. For example, it may switch to a better transmit antenna and speed up the antenna switching, report a lower CQI value to receive a lower assigned MCS for data transmission, and/or utilize additional HARQ processes for uplink transmission of same data or control information.
  • UE 115 may configure, adjust, or optimize latency reduction depending on a latency requirement of a user application or device operation. In one aspect, if a measured latency metric indicates potential large delay, UE 115 may evaluate whether the potential delay could meet the latency requirement and may configure latency reduction more aggressively to support low latency service, for example, by applying a larger reduction in one or more parameters affecting latency delay.
  • FIG. 6 illustrates an example of a method 600 that supports enhancement for low latency service in accordance with various aspects of the present disclosure.
  • the method 600 may further illustrate various aspects of the method 500 described with reference to FIG. 5 and may encompass various aspects of the process flow 200 described with reference to FIG. 2.
  • UE 115 measures a first metric for a first antenna and a second metric for a second antenna, which may be an example of block 510 in FIG. 5.
  • the metrics may be based on RSRQ, RSRP, RSSI, SNR, or other downlink measurements, which indicate a retransmission delay or latency for a transmit antenna. In some cases, the metrics may be averaged or filtered over measurements at various time instances.
  • UE 115 may switch transmit antenna from the first antenna to the second antenna, if the second latency metric is greater than the second metric by a switching threshold.
  • UE 115 may monitor the first and second metric on a continuing or regular basis.
  • UE 115 may compute the difference between the metrics for both antennas and compare it with the switching threshold to determine whether the second metric is greater than the first metric by the switching threshold (that is, the switching condition is met or triggered) .
  • UE 115 may increase a speed of switching antenna by configuring one or more parameters based on the at least one metric.
  • the one or more parameters may be the switching threshold, a measurement time constant, or a measurement frequency, or some combination thereof.
  • UE 115 may reduce the switching threshold, reduce a time constant (e.g., as used in averaging or filtering measurements) , or increase measurement frequency to speed up switching antenna, for example, as described in process flow 200 with reference to FIG. 2.
  • FIG. 7 illustrates an example of a method 700 that supports enhancement for low latency service in accordance with various aspects of the present disclosure.
  • the method 700 may further illustrate various aspects of the method 500 described with reference to FIG. 5 and may encompass various aspects of the process flow 300 described with reference to FIG 3.
  • UE 115 may measure a CQI, which may indicate a retransmission delay and latency.
  • the measured CQI may be derived from channel and interference estimation based on downlink reference signals, such as CRS or CSI-RS.
  • UE 115 may report a lower CQI value than the measured CQI.
  • UE 115 may apply a back-off factor on the measured CQI; for example, a 3dB back-off may be subtracted from the measured CQI value.
  • the lower reported CQI value may bias a base station 105 in regarding its communication link with UE 115 as having lower quality. Consequently the base station 105 may assign lower MCS for data transmission in response.
  • UE 115 may determine the reported lower CQI value based on a latency requirement of a user application or device operation. For example, UE 115 may apply large back-off when the latency requirement is high. The reported lower CQI value may also depend on the measured CQI. For example, smaller back-off may be used for higher measured CQI corresponding to better channel quality with less likelihood of failed transmission.
  • UE 115 may receive an uplink grant assigning a MCS in response to the reported lower CQI value. In some cases, UE 115 may assess whether the assigned MCS is adequate to meet latency requirement. UE 115 may further reduce the reported CQI value in order to obtain an even lower assigned MCS, when the currently assigned MCS may be inadequate.
  • UE 115 may transmit uplink data using the assigned MCS, which may be lower than would otherwise be if the higher measured CQI value is reported.
  • base station 105 may use a lower MCS, in response to receiving lower reported CQI, on downlink data transmission.
  • FIG. 8 illustrates an example of a method 800 that supports enhancement for low latency service in accordance with various aspects of the present disclosure.
  • the method 800 may further illustrate various aspects of the method 500 described with reference to FIG. 5 and may encompass various aspects of the process flow 400 described with reference to FIG 4.
  • UE 115 may transmit a BSR on a first HARQ process, including an initial transmission and subsequent retransmissions if the previous HARQ transmissions (including retransmissions) have failed (e.g., when UE 115 fails to receive a HARQ ACK from base station 105) .
  • UE 115 may measure a number of failed HARQ transmissions for the BSR on the first HARQ process.
  • a numerical counter may be used that increases for each failed HARQ transmission or retransmission.
  • UE 115 may transmit the BSR on a second HARQ process, if the number of failed HARQ transmissions is equal to or greater than a HARQ transmission threshold.
  • a MAC entity may be triggered to start the second HARQ process.
  • the second HARQ process may be interleaved in time with the first HARQ process.
  • both the first and second HARQ process may be operated in parallel.
  • the presence of additional HARQ process may be transparent to base station 105.
  • UE 115 may notify base station 105 of, or base station 105 may be otherwise aware of, the parallel operation of both HARQ processes for BSR transmission. Consequently base station 105 may combine receive BSR packets across different HARQ processes to increase decoding performance, for example, as described in process flow 400 with reference to FIG. 4.
  • FIG. 9 illustrates an example diagram 900 of a wireless device 905 that supports enhancement for low latency in accordance with various aspects of the present disclosure.
  • Wireless device 905 may be an example of a UE 115 described with reference to FIG. 1.
  • Wireless device 905 may perform various aspects of the example process flows 200-400, and the example methods 500-800, described with reference to FIGs 2-8.
  • Wireless device 905 may include receiver 910, communications manager 915, and transmitter 920.
  • Wireless device 905 may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses) .
  • Receiver 910 may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to enhancement for low latency service, etc. ) . Information may be passed on to other components of the device.
  • the receiver 910 may be an example of aspects of the transceiver 1035 described with reference to FIG. 10.
  • the receiver 910 may utilize a single antenna or a set of multiple antennas.
  • receiver 910 may receive downlink reference signals (e.g., CRS, CSI-RS), and downlink control signal or channel transmission from a base station 105 (e.g., an uplink grant, HARQ ACK or NACK) , and downlink data transmissions, in connection with various aspects of process flows 200-400 and methods 500-800 as described above.
  • downlink reference signals e.g., CRS, CSI-RS
  • downlink control signal or channel transmission from a base station 105 e.g., an uplink grant, HARQ ACK or NACK
  • Transmitter 920 may transmit signals generated by other components of the device.
  • the transmitter 920 may be collocated with a receiver 910 in a transceiver module.
  • the transmitter 920 may be an example of the transceiver 1035 described with reference to FIG. 10.
  • the transmitter 920 may utilize a single antenna or a set of multiple antennas.
  • transmitter 920 may transmit uplink data transmission, report CQI on an uplink control channel, or transmit a BSR on an uplink data channel, in connection with various aspects of process flows 200-400 and methods 500-800 as described above.
  • Communications manager 915 may be an example of the communications manager 1015 described with reference to FIG. 10.
  • Communications manager 915 may be a baseband modem or an application processor or may illustrate aspects of a baseband or application processor.
  • Communications manager 915 or at least some of its various sub-components may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions of the communications manager 915 or at least some of its various sub-components may be executed by a general-purpose processor, a DSP, an application-specific integrated circuit (ASIC) , a field-programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described in the present disclosure.
  • Software may comprise codes or instructions stored in a memory or like medium that is connected or in communication with the process described above. The codes or instructions may cause the processor, wireless device 905, or one or more components thereof to perform various functions described herein.
  • the communications manager 915 or at least some of its various sub-components may be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations by one or more physical devices.
  • communications manager 915 or at least some of its various sub-components may be a separate and distinct component in accordance with various aspects of the present disclosure.
  • communications manager 915 or at least some of its various sub-components may be combined with one or more other hardware components, including but not limited to an I/O component, a transceiver, a network server, another computing device, one or more other components described in the present disclosure, or a combination thereof in accordance with various aspects of the present disclosure.
  • Communications manager 915 may include latency metric measurement manager 925 and latency reduction manager 930.
  • Latency metric measurement manager 925 may determine at least one metric indicative of a retransmission delay for a data packet.
  • the at least one metric may be based on measurements (e.g., RSRQ, RSRP, RSSI, SNR) for one or more antennas, a measured CQI on a channel, or a number of failed HARQ transmissions (including retransmissions) .
  • Latency reduction manager 930 may reduce communication latency of the data packet, based at least on the determined at least one metric. For example, it may switch to a better transmit antenna and speed up the antenna switching, report a lower CQI value to receive a lower assigned MCS for data transmission, or utilize additional HARQ process for uplink transmission of the same packet. Furthermore, latency reduction manager 930 may configure, adjust, or optimize latency reduction depending on a latency requirement of a user application or device operation. In one aspect, if a measured latency metric indicates potential large delay, latency reduction manager 930 may evaluate whether the potential delay could meet the latency requirement and may configure latency reduction more aggressively to support low latency service, for example, by applying a larger reduction in one or more parameters affecting latency delay.
  • latency metric measurement manager 925 may measure a first metric for a first antenna and a second metric for a second antenna
  • latency reduction manager 930 may switch transmit antenna from a first antenna to a second antenna, if the second latency metric is greater than the first metric, and may increase a speed of switching antenna by configuring one or more parameters, based on the at least one metric, for example, as in process flow 200 or method 600 described with reference to FIGs. 2 and 6.
  • latency metric measurement manager 925 may measure a CQI
  • latency reduction manager 930 may report a lower CQI value than the measured CQI and receive an uplink grant assigning a MCS in response to the reported lower CQI value, for example, as in process flow 300 or method 700 described with reference to FIGs. 3 and 7.
  • latency metric measurement manager 925 may measure a number of failed HARQ transmissions (including retransmissions) for a BSR on a first HARQ process, and latency reduction manager 930 may transmit the BSR on a second HARQ process, if the number of failed HARQ transmissions is equal to or greater than a HARQ transmission threshold, for example, as in process flow 400 or method 800 described with reference to FIGs. 4 and 8.
  • FIG. 10 illustrates an example of a system 1000 including a device 1005 that supports enhancement for low latency service in accordance with various aspects of the present disclosure.
  • Device 1005 may be an example of or include the components of UE 115 or wireless device 905 described above with reference to FIGs. 1 and 9.
  • Device 1005 may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including communications manager 1015, processor (s) 1020, memory 1025, software 1030, transceiver 1035, antenna 1040, and I/O controller 1045. These components may be in electronic communication via one or more buses (e.g., bus 1010) .
  • Device 1005 may communicate wirelessly with one or more base stations 105.
  • Processor (s) 1020 may include an intelligent hardware device, (e.g., a general-purpose processor, a DSP, a central processing unit (CPU) , a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof) .
  • processor 1020 may be configured to operate a memory array using a memory controller.
  • a memory controller may be integrated into processor (s) 1020.
  • Processor (s) 1020 may be configured to execute computer-readable instructions stored in a memory to perform various functions (e.g., functions or tasks supporting enhancement for low latency service) .
  • Processor (s) 1020 may represent or include an application processor or a modem processor, or both.
  • Memory 1025 may include random access memory (RAM) and read only memory (ROM) .
  • the memory 1025 may store computer-readable, computer-executable software 1030 including instructions that, when executed, cause the processor to perform various functions described herein.
  • the memory 1025 may contain, among other things, a basic input/output system (BIOS) which may control basic hardware or software operation such as the interaction with peripheral components or devices.
  • BIOS basic input/output system
  • Software 1030 may include code to implement aspects of the present disclosure, including code to support enhancement for low latency service.
  • Software 1030 may be stored in a non-transitory computer-readable medium such as system memory or other memory. In some cases, the software 1030 may not be directly executable by the processor but may cause a computer (e.g., when compiled and executed) to perform functions described herein.
  • Transceiver 1035 may communicate bi-directionally, via one or more antennas, wired, or wireless links as described above.
  • the transceiver 1035 may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver.
  • the transceiver 1035 may also include a modem to modulate the packets and provide the modulated packets to the antennas for transmission, and to demodulate packets received from the antennas.
  • the wireless device may include a single antenna 1040. However, in some cases the device may have more than one antenna 1040, which may be capable of concurrently transmitting or receiving multiple wireless transmissions.
  • I/O controller 1045 may manage input and output signals for device 1005. I/O controller 1045 may also manage peripherals not integrated into device 1005. In some cases, I/O controller 1045 may represent a physical connection or port to an external peripheral. In some cases, I/O controller 1045 may utilize an operating system such as or another known operating system. In other cases, I/O controller 1045 may represent or interact with a modem, a keyboard, a mouse, a touchscreen, or a similar device. In some cases, I/O controller 1045 may be implemented as part of a processor. In some cases, a user may interact with device 1005 via I/O controller 1045 or via hardware components controlled by I/O controller 1045.
  • the functions described herein may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium.
  • Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another.
  • a storage media may be any available media that can be accessed by a general purpose or special purpose computer.
  • such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor.

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  • Computer Networks & Wireless Communication (AREA)
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  • Mobile Radio Communication Systems (AREA)

Abstract

La présente invention concerne des procédés, des systèmes, des dispositifs et des technologies destinés à améliorer un service à faible latence dans un réseau de communication sans fil. Un équipement utilisateur (UE) peut déterminer des métriques qui peuvent indiquer un retard de retransmission et ainsi une latence de communication. L'UE peut réduire la latence de communication, sur la base d'au moins une des métriques déterminées. Par exemple, pour réduire la latence, l'UE peut commuter vers une meilleure antenne d'émission et accélérer la commutation d'antenne, rapporter un indicateur de qualité de canal (CQI) inférieur pour recevoir un schéma de modulation ou de codage (MCS) attribué inférieur pour la transmission de données, ou utiliser des processus de demande de répétition automatique hybride (HARQ) supplémentaires pour la transmission en liaison montante des mêmes données ou d'informations de commande.
PCT/CN2017/099647 2017-08-30 2017-08-30 Amélioration pour service à faible latence WO2019041168A1 (fr)

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