WO2021223833A1 - Premier dispositif de communication et nœud d'accès au réseau pour réduire la latence dans un spectre sans licence à l'aide d'une procédure d'écoute avant de parler - Google Patents

Premier dispositif de communication et nœud d'accès au réseau pour réduire la latence dans un spectre sans licence à l'aide d'une procédure d'écoute avant de parler Download PDF

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Publication number
WO2021223833A1
WO2021223833A1 PCT/EP2020/062267 EP2020062267W WO2021223833A1 WO 2021223833 A1 WO2021223833 A1 WO 2021223833A1 EP 2020062267 W EP2020062267 W EP 2020062267W WO 2021223833 A1 WO2021223833 A1 WO 2021223833A1
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WIPO (PCT)
Prior art keywords
data packet
communication device
transmission period
network access
access node
Prior art date
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PCT/EP2020/062267
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English (en)
Inventor
Kiseon Ryu
Thorsten Schier
Bengt Lindoff
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Huawei Technologies Co., Ltd.
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Publication date
Application filed by Huawei Technologies Co., Ltd. filed Critical Huawei Technologies Co., Ltd.
Priority to PCT/EP2020/062267 priority Critical patent/WO2021223833A1/fr
Publication of WO2021223833A1 publication Critical patent/WO2021223833A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W74/00—Wireless channel access
    • H04W74/08—Non-scheduled access, e.g. ALOHA
    • H04W74/0808—Non-scheduled access, e.g. ALOHA using carrier sensing, e.g. carrier sense multiple access [CSMA]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0006—Assessment of spectral gaps suitable for allocating digitally modulated signals, e.g. for carrier allocation in cognitive radio
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H04L5/0053—Allocation of signaling, i.e. of overhead other than pilot signals
    • H04L5/0055—Physical resource allocation for ACK/NACK
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
    • H04W16/14—Spectrum sharing arrangements between different networks
    • 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
    • H04L1/1812—Hybrid protocols; Hybrid automatic repeat request [HARQ]
    • H04L1/1819—Hybrid protocols; Hybrid automatic repeat request [HARQ] with retransmission of additional or different redundancy
    • 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
    • H04L1/1829—Arrangements specially adapted for the receiver end
    • H04L1/1854—Scheduling and prioritising arrangements

Definitions

  • the invention relates to a first communication device and a network access node for reducing latency in unlicensed spectrum using a listen before talk procedure. Furthermore, the invention also relates to a corresponding method and a computer program.
  • NR-U new radio
  • NR-U NR-based access to unlicensed spectrum
  • DFS dynamic frequency selection
  • the network node searches and finds a part of the unlicensed spectrum with low load, thereby avoiding other systems if possible.
  • Another mechanism, well proven at lower-frequency bands, is listen before talk, where the transmitter ensures there are no ongoing transmissions on the carrier frequency prior to transmitting.
  • the channel access for NR-U will be based on listen before talk for fair sharing of the unlicensed spectrum and four categories has been defined for the listen before talk procedure in NR-U.
  • release 16 feature compatibility with NR-U and the listen before talk procedure still needs to be studied.
  • An objective of embodiments of the invention is to provide a solution which mitigates or solves the drawbacks and problems of conventional solutions.
  • a first communication device for a communication system, the first communication device being configured to receive data packets from a network access node in an unlicensed spectrum using a listen before talk procedure and further configured to: receive a first data packet from the network access node in a first transmission period, receive a second data packet from the network access node in a second transmission period following the first transmission period, wherein the second data packet comprises at least one part of the first data packet, transmit a first feedback associated with the first data packet to the network access node in a third transmission period, wherein a time gap between the second transmission period and the third transmission period is equal to or smaller than a threshold value.
  • An advantage of the first communication device is that the first communication device can transmit a first feedback associated with the first data packet to the network access node at the earliest possible time without performing the listen before talk procedure. Thereby, avoiding the risk of increasing the latency possibly caused by a failure of the listen before talk procedure.
  • the first data packet comprises a transport block and the second data packet comprises at least one of: the transport block, a redundancy version of the transport block, and one or more code block groups of the transport block.
  • An advantage with this implementation form is that the first communication device can decode the first data packet successfully by combining the first data packet and the second data packet even though it fails to decode the first data packet received in the first transmission period. Thereby, decreasing the latency associated with the reception of the first data packet.
  • the time gap starts when the second transmission period ends at a first time instance and stops when the third transmission period begins at a second time instance.
  • the threshold value is a first threshold value and the first communication device is configured to: transmit the first feedback without clear channel assessment, when the time gap is equal to or smaller than the first threshold value.
  • the first communication device can avoid increasing the latency for transmission of the first feedback caused by a failure of the listen before talk procedure.
  • the threshold value is a second threshold value and the first communication device is configured to: perform clear channel assessment without random back-off before transmitting the first feedback, when the time gap is equal to or smaller than the second threshold value and larger than a first threshold value, and transmit the first feedback without clear channel assessment, when the time gap is equal to or smaller than the first threshold value.
  • An advantage with this implementation form is that the first communication device can avoid increasing the latency for transmission of the first feedback due to random back-off of the listen before talk procedure.
  • the first threshold value is 16 ps and the second threshold value is 25 ps.
  • the first feedback is an acknowledgement upon successful decoding of the first data packet and the first feedback is a negative acknowledgement upon unsuccessful decoding of the first data packet.
  • the first communication device is further configured to, upon successful decoding of the first data packet: discard the second data packet, and cancel or skip transmission of a second feedback associated with the second data packet to the network access node in a fourth transmission period.
  • An advantage with this implementation form is that the first device communication can save its power by not processing the second data packet and by not transmitting a second feedback associated with the second data packet to the network.
  • the first communication device is further configured to, upon unsuccessful decoding of the first data packet: decode the first data packet by combining information from the received first data packet and the received second data packet, and transmit a second feedback associated with the second data packet to the network access node in a fourth transmission period.
  • An advantage with this implementation form is that the first communication device can reduce the latency to decode the first data packet successfully by starting to combine the first data packet and the second data packet before transmitting a negative feedback for the first data packet.
  • the first data packet and the second data packet are associated with an ultra-reliable and low- latency communications, URLLC, service.
  • URLLC ultra-reliable and low- latency communications
  • An advantage with this implementation form is that it can provide improved performance in respect of low data latency for an URLLC data packet transmission in unlicensed spectrum.
  • a network access node for a communication system, the network access node being configured to transmit data packets to a first communication device in an unlicensed spectrum using a listen before talk procedure and further configured to: transmit a first data packet to the first communication device in a first transmission period, transmit a second data packet to the first communication device in a second transmission period following the first transmission period, wherein the second data packet comprises at least one part of the first data packet, receive a first feedback associated with the first data packet from the first communication device in a third transmission period, wherein a time gap between the second transmission period and the third transmission period is equal to or smaller than a threshold value.
  • An advantage of the network access node according to the second aspect is that the network access node can receive the first feedback associated with the first data packet without delay due to a failure of the listen before talk procedure at the first communication device. Thereby, decreasing the latency associated with the first data packet.
  • the first data packet comprises a transport block and the second data packet comprises at least one of: the transport block, a redundancy version of the transport block, and one or more code block groups of the transport block.
  • the time gap starts when the second transmission period ends at a first time instance and stops when the third transmission period begins at a second time instance.
  • the network access node is further configured to: determine a start of the third transmission period based on at least one of a duration of the second transmission period and the threshold value.
  • An advantage with this implementation form is that the network access node can ensure that the time gap is equal to or smaller than the threshold value and hence that the first feedback from the first communication device can be received at the earliest possible time.
  • the network access node is further configured to: determine a duration of the second transmission period based on a minimum processing time of the first communication device for the first data packet in the first transmission period.
  • the duration of the second transmission period may be determined to be equal to or larger than the minimum processing time of the first communication device for the data packet in the first transmission period.
  • An advantage with this implementation form is that the network access node can receive a first feedback associated with the first data packet at the earliest possible time from the first communication device, thereby decreasing the latency.
  • the network access node is further configured to: adapt the duration of the second transmission period by adjusting at least one of: a number of transport blocks, a number of resource elements, a modulation coding scheme, and a number of code block groups.
  • the threshold value is 16 ps or 25 ps.
  • An advantage with this implementation form is that the network access node can minimize the listen before talk impact on the latency for the first feedback transmission from the first communication device.
  • the first feedback is an acknowledgement or a negative acknowledgement.
  • the network access node is further configured to: assign a fourth transmission period for transmission of a second feedback associated with the second data packet when the first feedback is a negative acknowledgement.
  • An advantage with this implementation form is that the network access node can determine whether or not to retransmit the first data packet further based on the received second feedback.
  • the network access node is further configured to: perform clear channel assessment without random back-off before at least one of the first transmission period and a subsequent transmission period associated with a re transmission of the first data packet.
  • An advantage with this implementation form is that the network access node can reduce the latency to transmit a data packet in the first transmission period and to retransmit the data packet in a subsequent transmission period.
  • the network access node is further configured to: transmit a control message to a second communication device, wherein the control message indicates a reserved transmission period for communication between the network access node and the first communication device.
  • An advantage with this implementation form is that the network access node can prevent any collision from a second communication device during the reserved transmission period for communication with the first communication device.
  • the first data packet and the second data packet are associated with an URLLC service.
  • An advantage with this implementation form is that it can provide improved performance in respect of low data latency for an URLLC data packet transmission in unlicensed spectrum.
  • the above mentioned and other objectives are achieved with a second communication device for a communication system, the second communication device being configured to communicate with a network access node in an unlicensed spectrum using a listen before talk procedure and further configured to: receive a control message from the network access node, wherein the control message indicates a reserved transmission period for communication between the network access node and a first communication device; cancel or skip transmission during the reserved transmission period.
  • An advantage of the second communication device according to the third aspect is that the second communication device can avoid collision between its transmission and other transmission.
  • the above mentioned and other objectives are achieved with a method for a first communication device, the first communication device being configured to receive data packets from a network access node in an unlicensed spectrum using a listen before talk procedure, the method comprises: receiving a first data packet from the network access node in a first transmission period, receiving a second data packet from the network access node in a second transmission period following the first transmission period, wherein the second data packet comprises at least one part of the first data packet, transmitting a first feedback associated with the first data packet to the network access node in a third transmission period, wherein a time gap between the second transmission period and the third transmission period is equal to or smaller than a threshold value.
  • the method according to the fourth aspect can be extended into implementation forms corresponding to the implementation forms of the first communication device according to the first aspect.
  • an implementation form of the method comprises the features of the corresponding implementation form of the first communication device.
  • the above mentioned and other objectives are achieved with a method for a network access node, the network access node being configured to transmit data packets to a first communication device in an unlicensed spectrum using a listen before talk procedure, the method comprises: transmitting a first data packet to the first communication device in a first transmission period, transmitting a second data packet to the first communication device in a second transmission period following the first transmission period, wherein the second data packet comprises at least one part of the first data packet, receiving a first feedback associated with the first data packet from the first communication device in a third transmission period, wherein a time gap between the second transmission period and the third transmission period is equal to or smaller than a threshold value.
  • the method according to the fifth aspect can be extended into implementation forms corresponding to the implementation forms of the network access node according to the second aspect.
  • an implementation form of the method comprises the features of the corresponding implementation form of the network access node.
  • the above mentioned and other objectives are achieved with a method for a second communication device, the second communication device being configured to communicate with a network access node in an unlicensed spectrum using a listen before talk procedure, the method comprises: receiving a control message from the network access node, wherein the control message indicates a reserved transmission period for communication between the network access node and a first communication device; cancelling or skipping transmission during the reserved transmission period.
  • an implementation form of the method comprises the features of the corresponding implementation form of the second communication device.
  • the invention also relates to a computer program, characterized in program code, which when run by at least one processor causes said at least one processor to execute any method according to embodiments of the invention.
  • the invention also relates to a computer program product comprising a computer readable medium and said mentioned computer program, wherein said computer program is included in the computer readable medium, and comprises of one or more from the group: ROM (Read-Only Memory), PROM (Programmable ROM), EPROM (Erasable PROM), Flash memory, EEPROM (Electrically Erasable PROM) and hard disk drive.
  • FIG. 1 shows a first communication device according to an embodiment of the invention
  • FIG. 2 shows a method for a first communication device according to an embodiment of the invention
  • - Fig. 3 shows a network access node according to an embodiment of the invention
  • - Fig. 4 shows a method for a network access node according to an embodiment of the invention
  • FIG. 5 shows a communication system according to an embodiment of the invention
  • FIG. 6 shows a timeline for communication between a network access node and a first communication device according to an embodiment of the invention
  • Fig. 7 shows a timeline for communication between a network access node and a first communication device according to an embodiment of the invention
  • Fig. 8 shows a timeline for a listen before talk procedure for a network access node according to an embodiment of the invention
  • Fig. 9 shows a timeline for a listen before talk procedure for a network access node according to an embodiment of the invention.
  • Fig. 10 shows a timeline for communication between a network access node, a first communication device, and a second communication device according to an embodiment of the invention.
  • Listen before talk is a procedure used by devices to determine the presence of signals in a channel in an unlicensed spectrum before using it, to avoid collisions with other transmissions. This protocol allows many users and different technologies to use the same channel without pre-coordination.
  • the LBT procedure initializes when a device such as e.g. a nodeB (NB) or a user equipment (UE), has data or control information to transmit.
  • NB nodeB
  • UE user equipment
  • CCA clear channel assessment
  • Category 1 allows transmission without LBT, i.e. without CCA, and can be used by a device if its transmission is initiated 16 ps or less from a previous transmission.
  • a next generation nodeB (gNB) and one or more user equipments (UEs) can transmit multiple downlink and uplink transmissions without performing LBT, if each transmission gap is 16 ps or less in the same channel occupancy time (COT).
  • CO channel occupancy
  • gNB next generation nodeB
  • UEs user equipments
  • COT channel occupancy time
  • the maximum duration of the transmission from UE is limited to 584 ps.
  • Category 2 allows transmission after CCA but without random back-off and can be used by a device initiating a CO to transmit a discovery reference signal (DRS) or if a transmission within a COT is initiated more than 16 ps but less than 25 ps from a previous transmission.
  • DRS discovery reference signal
  • Category 3 allows transmission after CCA and after random back-off with fixed size of contention window.
  • a device can proceed with transmission after sensing the channel to be idle during the defer duration, e.g. 25 ps, and after additional slot durations with N times, e.g. 9*N ps, where N is randomly selected within the fixed size of contention window. The size of contention window is not changed.
  • Category 4 allows transmission after CCA and after random back-off with variable size of contention window. This is typically used when a device initiates a CO except for some DRS transmissions. A device performs a slotted random back-off procedure, in which a random number of slots is withdrawn from the contention window. The contention window increases exponentially with the occurrence of collisions, and then gets reset to the minimum value once the transmission succeeds. Given the random nature of the back-off procedure, different devices will have different back off intervals allowing for improved channel adaptation.
  • NR-U only category 1 , 2, and 4 LBT are supported, where the respective categories can be used as described above.
  • Ultra-reliable and low-latency communications is a new service category in 5G to accommodate emerging services and applications having stringent latency and reliability requirements.
  • One important factor to ensure the strict latency requirements of URLLC services is that hybrid automatic repeat request (HARQ) feedback is transmitted as fast as possible for URLLC transmissions.
  • HARQ hybrid automatic repeat request
  • the listen before talk procedure may delay the transmission of HARQ feedback and thus impact the latency of URLLC services in unlicensed spectrum in a negative way.
  • NR-U uses NR HARQ feedback mechanisms as baseline and potential HARQ enhancements have been discussed for NR-U.
  • Transmission of HARQ feedback for a data transmission in the same shared channel occupancy time (COT) as the data transmission has been identified as beneficial.
  • a gap of up to 16 ps can be allowed between the end of a downlink transmission and a transmission of HARQ feedback to a previous downlink data transmission.
  • the hardware turnaround time i.e. the UE processing time to decode the downlink data transmission
  • Such transmission may e.g.
  • CSI channel state information
  • CSI-RSs CSI reference signals
  • SRS sounding reference signals
  • PUSCH physical uplink shared channel
  • PDSCH physical downlink shared channel
  • the HARQ feedback has to be transmitted in a separate COT from the one in which the corresponding data was transmitted.
  • Techniques to handle reduced HARQ feedback transmission opportunities for a given HARQ process due to LBT failure are identified as beneficial. Potential techniques include mechanisms to provide multiple and/or supplemental time and/or frequency domain transmission opportunities.
  • NR-U considers mechanisms to support flexible triggering and multiplexing of HARQ feedback for one or more downlink HARQ processes.
  • the following possible candidate solutions can be considered:
  • gNB requests/triggers feedback for data transmission from earlier COT(s).
  • UE is configured to report HARQ feedback for data transmission from earlier COT(s) without an explicit request/trigger.
  • a timing indicator indicating the time from a data transmission to the HARQ feedback transmission is included in the downlink control information (DCI) scheduling the data transmission.
  • DCI downlink control information
  • a gNB and a UE should perform LBT before transmitting downlink/uplink packets.
  • the inventors have identified at least three ways which LBT can impact the latency of URLLC services in unlicensed spectrum:
  • HARQ feedback for a URLLC packet may not be sent at the earliest possible time, due to LBT failure at the receiver. If the time gap between the transmission of a URLLC packet to a UE and the HARQ feedback for the URLLC packet from the UE is larger than 25 ps and no signal is transmitted during the time gap, the UE have to perform category 4 LBT. Interference from other devices may occur during the LBT and the HARQ feedback may not be sent due to LBT failure, thereby increasing the latency of the URLLC packet transmission. Another issue may be delayed initial transmission of URLLC packet due to the random backoff associated with category 4 LBT.
  • the gNB When a gNB initiates a CO to transmit a transmission including a URLLC packet, the gNB should perform the category 4 LBT, i.e. LBT with random back-off with variable size of contention window. Due to LBT with random back-off, the URLLC packet transmission from the gNB may be delayed if the channel is occupied.
  • LBT category 4 LBT
  • the URLLC packet transmission from the gNB may be delayed if the channel is occupied.
  • Yet another issue may be delayed retransmission of URLLC packet due to no HARQ feedback and the random back-off associated with category 4 LBT.
  • the gNB When the gNB does not receive a HARQ feedback for a transmitted URLLC packet from the intended receiver UE, it should perform the category 4 LBT with the exponential random back-off, i.e. channel access with a larger contention window, to retransmit the URLLC packet to the UE. This can cause large delays for URLLC packet retransmission.
  • An objective of the invention is therefore to minimize the latency, i.e. reduce the risk of delay, when a network access node and a first communication device are communicating with each other in an unlicensed spectrum using a listen before talk procedure.
  • Fig. 1 shows a first communication device 100 according to an embodiment of the invention.
  • the first communication device 100 comprises a processor 102, a transceiver 104 and a memory 106.
  • the processor 102 may be coupled to the transceiver 104 and the memory 106 by communication means 108 known in the art.
  • the first communication device 100 may further comprise an antenna or antenna array 110 coupled to the transceiver 104, which means that the first communication device 100 may be configured for communications in a communication system.
  • first communication device 100 may be configured to perform certain actions can in this disclosure be understood to mean that the first communication device 100 comprises suitable means, such as e.g. the processor 102 and the transceiver 104, configured to perform said actions.
  • the first communication device 100 is configured to receive data packets from a network access node 300 in an unlicensed spectrum using a listen before talk procedure.
  • the first communication device 100 is further configured to receive a first data packet DP1 from the network access node 300 in a first transmission period T 1 and receive a second data packet DP2 from the network access node 300 in a second transmission period T2 following the first transmission period T1 , wherein the second data packet DP2 comprises at least one part of the first data packet DP1.
  • the first communication device 100 is further configured to transmit a first feedback F1 associated with the first data packet DP1 to the network access node 300 in a third transmission period T3, wherein a time gap TG between the second transmission period T2 and the third transmission period T3 is equal to or smaller than a threshold value Th1 ; Th2.
  • Fig. 2 shows a flow chart of a corresponding method 200 which may be executed in a first communication device 100, such as the one shown in Fig. 1.
  • the first communication device 100 is configured to receive data packets from a network access node 300 in an unlicensed spectrum using a listen before talk procedure.
  • the method 200 comprises receiving 202 a first data packet DP1 from the network access node 300 in a first transmission period T 1 and receiving 204 a second data packet DP2 from the network access node 300 in a second transmission period T2 following the first transmission period T1 , wherein the second data packet DP2 comprises at least one part of the first data packet DP1.
  • the method 200 further comprises transmitting 206 a first feedback F1 associated with the first data packet DP1 to the network access node 300 in a third transmission period T3, wherein a time gap TG between the second transmission period T2 and the third transmission period T3 is equal to or smaller than a threshold value Th1 ; Th2.
  • Fig. 3 shows a network access node 300 according to an embodiment of the invention.
  • the network access node 300 comprises a processor 302, a transceiver 304 and a memory 306.
  • the processor 302 is coupled to the transceiver 304 and the memory 306 by communication means 308 known in the art.
  • the network access node 300 may be configured for both wireless and wired communications in wireless and wired communication systems, respectively.
  • the wireless communication capability is provided with an antenna or antenna array 310 coupled to the transceiver 304, while the wired communication capability is provided with a wired communication interface 312 coupled to the transceiver 304.
  • the network access node 300 is configured to perform certain actions can in this disclosure be understood to mean that the network access node 300 comprises suitable means, such as e.g. the processor 302 and the transceiver 304, configured to perform said actions.
  • the network access node 300 is configured to transmit data packets to a first communication device 100 in an unlicensed spectrum using a listen before talk procedure.
  • the network access node 300 is further configured to transmit a first data packet DP1 to the first communication device 100 in a first transmission period T1 and transmit a second data packet DP2 to the first communication device 100 in a second transmission period T2 following the first transmission period T1 , wherein the second data packet DP2 comprises at least one part of the first data packet DP1.
  • the network access node 300 is further configured to receive a first feedback F1 associated with the first data packet DP1 from the first communication device 100 in a third transmission period T3, wherein a time gap TG between the second transmission period T2 and the third transmission period T3 is equal to or smaller than a threshold value Th1 ; Th2.
  • Fig. 4 shows a flow chart of a corresponding method 400 which may be executed in a network access node 300, such as the one shown in Fig. 3.
  • the method 400 comprises transmitting 402 a first data packet DP1 to the first communication device 100 in a first transmission period T 1 and transmitting 404 a second data packet DP2 to the first communication device 100 in a second transmission period T2 following the first transmission period T1 , wherein the second data packet DP2 comprises at least one part of the first data packet DP1.
  • the method 400 further comprises receiving 406 a first feedback F1 associated with the first data packet DP1 from the first communication device 100 in a third transmission period T3, wherein a time gap TG between the second transmission period T2 and the third transmission period T3 is equal to or smaller than a threshold value Th1 ; Th2.
  • Fig. 5 show a communication system 500 according to an embodiment of the invention.
  • the communication system 500 comprises a network access node 300, a first communication device 100, and a second communication device 120, all configured to operate in the communication system 500.
  • the first communication device 100 and the network access node 300 are configured to communicate with each other in an unlicensed spectrum using a listen before talk procedure.
  • the communication system 500 can in embodiments be based on NR or LTE radio access technology (RAT) in which case the first communication device 100 and the network access node 300 may e.g. use NR access to unlicensed spectrum, i.e. NR-U.
  • RAT radio access technology
  • the invention is not limited thereto.
  • the network access node 300 may be configured to transmit data packets DPs to the first communication device 100 over the unlicensed spectrum, as indicated in Fig. 5.
  • the data packets DPs may be associated with an ultra-reliable and low-latency communications (URLLC) service.
  • URLLC ultra-reliable and low-latency communications
  • the network access node 300 therefore extends its transmission to the first communication device 100 so that a gap between the transmission from the network access node 300 and the feedback transmission from the first communication device 100 is smaller than a threshold value.
  • the threshold value may be selected such that the first communication device 100 does not have to perform listen before talk before transmitting its feedback or only perform CCA without random back-off. In this way, the risk that the transmission of the feedback from the first communication device 100 is delay due to a listen before talk failure can be avoided or minimized.
  • the network access node 300 may transmit a control message 502 to the second communication device 120, as shown in Fig. 5.
  • the control message 502 may indicate a transmission period during which the first communication device 100 and the network access node 300 communicates such that the second communication device 120 may cancel or skip transmitting during this transmission period.
  • Fig. 6 shows a timeline for communication between the network access node 300 and the first communication device 100 in a first channel occupancy time COT1 according to an embodiment of the invention.
  • the network access node 300 has a first data packet DP1 to transmit to the first communication device 100 in the unlicensed spectrum.
  • the first data packet DP1 may in embodiments be associated with a URLLC service.
  • the network access node 300 performs listen before talk LBT to sense the channel before transmitting the first data packet DP1 to the first communication device 100.
  • the network access node 300 may e.g. perform clear channel assessment with or without random back-off, as will be further described below with reference to Figs. 8-9.
  • the network access node 300 transmits the first data packet DP1 to the first communication device 100 in a first transmission period T1 , i.e. initiates the first channel occupancy time COT1.
  • the transmission of the first data packet DP1 in the first transmission period T 1 may in a conventional way comprise transmission of control information in a PDCCH followed by the transmission of data in a PDSCH.
  • the network access node 300 further transmit a second data packet DP2 to the first communication device 100 in a second transmission period T2 following the first transmission period T1.
  • the second transmission period T2 may follow directly upon the first transmission period T 1 , i.e. start when the first transmission period T 1 ends, as shown in Fig. 6.
  • the second transmission period T2 may further start shortly after the first transmission period T1 ends, where shortly means that a possible gap between the second transmission period T2 and the first transmission period T1 is so small that network access node 300 keeps the channel occupancy and does not have to perform the listen before talk procedure before the second transmission period T2.
  • the second data packet DP2 comprises at least one part of the first data packet DP1.
  • the transmission in the second transmission period T2 may hence correspond to a transmission of a part of the first data packet DP1 or the first data packet DP1 , as well as multiples of the part or the whole first data packet DP1.
  • the first data packet DP1 comprises a transport block TB and the second data packet DP2 comprises at least one of: the transport block TB, a redundancy version of the transport block TB ' , and one or more code block groups CBGs of the transport block TB.
  • the second data packet DP2 may comprise the transport block TB and a redundancy version of the transport block TB ' , or two times the transport block TB.
  • the second data packet DP2 may comprise one or more of the code block groups CBGs of the transport block TB.
  • the first communication device 100 receives the same transport block TB twice, both in the first transmission period T1 and the second transmission period T2. In this case, the first communication device 100 may use the two transport blocks TBs for HARQ chase combining. A part of the transport block TB, e.g. one code block group CBG, received twice may also be used for HARQ chase combining.
  • the first communication device 100 may use the transport block TB received in the first transmission period T1 and the redundancy version of the transport block TB ' received in the second transmission period T2 for HARQ incremental redundancy.
  • the first communication device 100 transmit a first feedback F1 associated with the first data packet DP1 to the network access node 300 in a third transmission period T3.
  • the first feedback F1 may be triggered by the reception of the first data packet DP1 from the network access node 300 in the first transmission period T 1 and may depend on whether the first data packet DP1 can be decoded successfully or not by the first communication device 100.
  • the first feedback F1 may be an acknowledgement upon successful decoding of the first data packet DP1 and the first feedback F1 may be a negative acknowledgement upon unsuccessful decoding of the first data packet DP1 .
  • the first feedback F1 may be a HARQ feedback.
  • the third transmission period T3 may be indicated in the control information associated with the first data packet D1 in the first transmission period T 1.
  • time gap TG between the second transmission period T2 and the third transmission period T3.
  • the time gap TG starts when the second transmission period T2 ends and stops when the third transmission period T3 begins.
  • the second transmission period T2 may end at a first time instance t1 and the third transmission period T3 may begin at a second time instance t2.
  • time gap TG may start at the first time instance t1 and stop at the second time instance t2.
  • the time gap TG is equal to or smaller than a threshold value Th1 ; Th2.
  • the threshold value Th1 ; Th2 may be associated with the listen before talk procedure and when the time gap TG is equal to or smaller than the threshold value Th1 ; Th2, the first communication device 100 can transmit the first feedback F 1 in the third transmission period T3 without performing listen before talk. Listen before talk failure preventing the transmission of the first feedback F1 can thereby be prevented.
  • the network access node 300 may determine a start of the third transmission period T3 and/or a duration of the second transmission period T2 such that the time gap TG is equal to or smaller than the threshold value Th1 ; Th2.
  • the network access node 300 may adjust the time gap TG to be equal to or smaller than the threshold value Th1 ; Th2.
  • the network access node 300 may determine the start of the third transmission period T3 based on at least one of a duration of the second transmission period T2 and the threshold value Th1 ; Th2. The network access node 300 may in turn determine the duration of the second transmission period T2 based on a minimum processing time N1 of the first communication device 100 for the first data packet DP1 in the first transmission period T 1.
  • the minimum processing time N1 of the first communication device 100 may be determined by the processing capability of the first communication device 100, i.e. how fast the first communication device 100 can decode the first data packet DP1.
  • the minimum processing time N1 of the first communication device 100 may correspond to the time from the end of the transmission of the first data packet DP1 to the start of the transmission of the first feedback F1 associated with the first data packet DP1.
  • the minimum processing time N1 of the first communication device 100 may be referred to as the hardware turnaround time and may expressed as a symbol interval.
  • the duration of the second transmission period T2 may e.g. be determined to be equal to or larger than the minimum processing time N1 of the first communication device 100 for the first data packet DP1 in the first transmission period T1. In this way, the second transmission period T2 will end at a time instance at which the first communication device 100 is capable of transmit the first feedback F1 for the first data packet DP1 , i.e. have had time to process the first data packet DP1.
  • the network access node 300 may adapt the duration of the second transmission period T2 by adjusting at least one of a number of transport blocks, a number of resource elements, a modulation coding scheme, and a number of code block groups comprised in the second data packet DP2.
  • the network access node 300 may determine the content of the second data packet DP2 and the transmission parameters for the transmission of the second data packet DP2 to achieve a desired duration of the second transmission period T2.
  • the first data packet DP1 and the second data packet DP2 may or may not comprise the same number of e.g. resources elements.
  • the modulation coding scheme used for the transmission of the second data packet DP2 be may be implicitly derived from the modulation coding scheme used for the transmission of the first data packet DP1 and the number of resources and/or power settings used in the transmissions.
  • the threshold value may in embodiments be a first threshold value Th1.
  • the first communication device 100 may be configured to transmit the first feedback F1 without clear channel assessment, when the time gap TG is equal to or smaller than the first threshold value Th1.
  • the threshold value may further be a second threshold value Th2 larger than the first threshold value Th1.
  • the first communication device 100 may be configured to perform clear channel assessment without random back-off before transmitting the first feedback F1 , when the time gap TG is equal to or smaller than the second threshold value Th2 and larger than the first threshold value Th1 , and transmit the first feedback F1 without clear channel assessment, when the time gap TG is equal to or smaller than the first threshold value Th1.
  • the threshold value Th1 ; Th2 may be adapted to the time intervals use in the listen before talk procedure according to the 3GPP standard and may hence in embodiments be 16 ps or 25 ps.
  • the first threshold value Th1 may be 16 ps and the second threshold value Th2 may be 25 ps.
  • the first communication device 100 may discard the second data packet DP2.
  • the first communication device 100 may further cancel or skip transmission of a second feedback F2 associated with the second data packet DP2 to the network access node 300 in a fourth transmission period T4.
  • the first communication device 100 successful decodes the first data packet DP1
  • the first communication device 100 does not have to decode the second data packet DP2 which comprises a repeat of at least a part of the first data packet DP1.
  • the second data packet DP2 can hence be discarded. If a fourth transmission period T4 has been assigned for the transmission of the second feedback F2 associated with the second data packet DP2, the transmission of the second feedback F2 in the fourth transmission period T4 may be cancelled or skipped.
  • Fig. 7 shows a timeline for communication between the network access node 300 and the first communication device 100 according to an embodiment of the invention where the decoding of the first data packet DP1 received in the first transmission period T 1 is unsuccessful.
  • the first communication device 100 cannot decode the first data packet DP1 received in the first transmission period T1 and hence transmits a negative acknowledgement NACK in the third transmission period T3, i.e. the first feedback F1 is a negative acknowledgement NACK.
  • the first communication device 100 may further attempt to decode the first data packet DP1 using also the second data packet DP2 received in the second transmission period T2. Thus, upon unsuccessful decoding of the first data packet DP1 received in the first transmission period T1 , the first communication device 100 may decode the first data packet DP1 by combining information from the received first data packet DP1 and the received second data packet DP2. The first communication device 100 may hence combine information received in the first transmission period T1 with information received in the second transmission period T2 and then decode the combined information to retrieve the first data packet DP1. The first communication device 100 may further transmit a second feedback F2 associated with the second data packet DP2 to the network access node 300 in a fourth transmission period T4.
  • the second feedback F2 may be an acknowledgement upon successful decoding of the combined information and the second feedback F2 may be a negative acknowledgement upon unsuccessful decoding of the combined information.
  • the fourth transmission period T4 may be outside the first channel occupancy time COT1 in a second channel occupancy time COT2, where the second channel occupancy time COT2 may be initiated by the network access node 300 for a data transmission DT not associated with the first data packet DP1.
  • the network access node 300 may assign the fourth transmission period T4 to the first communication device 100 when transmitting the second data packet DP2 to the communication device 100.
  • the network access node 300 may assign the fourth transmission period T4 for transmission of the second feedback F2 associated with the second data packet DP2 when the first feedback F1 is a negative acknowledgement.
  • the first communication device 100 may further transmit the second feedback F2 without an explicit request and/or trigger from the network access node 300.
  • the fourth transmission period T4 may be initiated by the first communication device 100.
  • the network access node 300 may discard the first data packet DP1 in the transmit buffer.
  • the second data packet DP2 comprises at least one part of the first data packet DP1.
  • the second data packet DP2 may in an alternative embodiment instead comprise a dummy signal (not shown in Figs.).
  • the transmission in the second transmission period T2 may in this case comprise control information in the PDCCH which indicates a dummy signal transmission followed by the dummy signal transmission in the PDSCH.
  • the dummy signal transmission may be indicated in a downlink control information (DCI).
  • DCI downlink control information
  • the same DCI indicating the transmission in the first transmission period T1 may be used for the DCI indicating the dummy signal transmission.
  • the first communication device 100 may skip decoding any further data transmissions during the channel occupancy time COT1 and may not respond with a second feedback F2 for the second data packet DP2.
  • the first communication device 100 may report the misdetection to the network access node 300. Thereby, allowing the network access node 300 to transmit a new initial transmission instead of sending another redundancy version of the first data packet DP1.
  • the network access node 300 performs listen before talk LBT before initiating the first channel occupancy time COT1 and the second channel occupancy time COT2.
  • the listen before talk procedure before initiating a channel occupancy is a category 4 LBT, i.e. clear channel assessment with random back-off with variable size of contention window.
  • the invention provides specific channel access in certain scenarios, e.g. when the data packet to be transmitted is associated with a URLLC service.
  • the network access node 300 may hence perform clear channel assessment without random back-off before at least one of the first transmission period T1 and a subsequent transmission period associated with a re-transmission of the first data packet DP1.
  • Fig. 8 shows a timeline of an embodiment where the network access node 300 performs clear channel assessment CCA without random back-off before both the first transmission period T1 and the subsequent transmission period TS. As shown in Fig. 8, the network access node 300 performs clear channel assessment CCA without random back-off to initiate a channel occupancy for transmitting the first data packet DP1 , i.e. before the first transmission period T 1.
  • the network access node 300 If the network access node 300 does not receive an acknowledgement for the first data packet DP1 , the network access node 300 performs clear channel assessment CCA without random back-off to initiate another channel occupancy for re-transmitting the first data packet DP1 in the subsequent transmission period TS.
  • Fig. 9 shows a timeline of an embodiment where the network access node 300 performs clear channel assessment CCA without random back-off only before the first transmission period T1.
  • the network access node 300 may perform clear channel assessment CCA with random back-off RB with a fixed size of contention window to initiate the other channel occupancy for re-transmitting the first data packet DP1 in the subsequent transmission period TS, as shown in Fig. 9.
  • This may be beneficial to avoid intra-cell collision of the re-transmission of the first data packet DP1 with radio resource control (RRC)-configured uplink transmissions from other communication devices in the cell.
  • RRC radio resource control
  • the network access node 300 may thus in embodiments use category 2 LBT before certain types of transmissions where category 4 LBT would have been used conventionally.
  • the network access node 300 may e.g. use category 2 LBT to initiate a channel occupancy in a controlled environment, i.e. an environment which contains only devices operating in an unlicensed spectrum installed by a facility owner and where unexpected interference from other systems and/or radio access technologies only happens sporadically.
  • a controlled environment data packet transmission from the network access node 300 by performing category 2 LBT rarely collide with intra-cell interference since the network access node 300 can control the channel access for communication devices in a cell.
  • all the communication devices in the cell should perform category 4 LBT, i.e.
  • LBT with random back- off with variable size of contention window, to initiate a channel occupancy for a dynamically scheduled transmission or a radio resource control (RRC)-configured transmission.
  • RRC radio resource control
  • different frequency band/channel can be assigned to each unlicensed cell.
  • Unexpected interference from other RATs e.g. probing from Wi-Fi device, may occur.
  • other RATs usually require a longer sensing duration, e.g. 34 ps, than the category 2 LBT sensing duration, i.e. 25 ps.
  • Transmission with category 2 LBT may have a higher priority than unexpected interference, so that unexpected interference would not usually collide with a data transmission with category 2 LBT.
  • the network access node 300 may provide information to a second communication device 120 about an ongoing communication with the first communication device 100, e.g. if the communication with the first communication device 100 is associated with a URLLC service and/or have higher priority than other communication in a cell.
  • the network access node 300 may provide the information by transmitting a control message 502 to the second communication device 120, as shown in Fig. 5.
  • the control message 502 indicates a reserved transmission period T5 for communication between the network access node 300 and the first communication device 100.
  • the control message may e.g. be a new DCI and may be transmitted by the network access node 300 before or upon starting the communication with the first communication device 100.
  • the second communication device 120 may be configured to communicate with the network access node 300 in the unlicensed spectrum using the listen before talk procedure and further configured to receive the control message 502 from the network access node 300, where the control message 502 indicates the reserved transmission period T5 for communication between the network access node 300 and the first communication device 100. Based on the received control message 502, the second communication device 120 may cancel or skip transmission during the reserved transmission period T5.
  • the transmission(s) cancelled or skipped may e.g. be dynamically granted uplink data/control transmission(s) with grant received in a previous channel occupancy or RRC configured uplink transmission(s) such as e.g. configured grant uplink, sounding reference signal (SRS), physical uplink control channel (PUCCH), random access channel (RACH).
  • SRS sounding reference signal
  • PUCCH physical uplink control channel
  • RACH random access channel
  • Fig. 10 shows a timeline for an embodiment where the second communication device 120 cancels or skips transmission during a reserved transmission period T5 after receiving a control message 502 from the network access node 300.
  • the second communication device 120 is configured with periodic uplink transmission occasions of which four are shown in Fig. 10.
  • the second communication device 120 Upon receiving the control message 502 indicating the reserved transmission period T5, the second communication device 120 cancels or skips transmission in the two uplink transmission occasions occurring during the reserved transmission period T5, shown as dashed boxes in Fig. 10.
  • the second communication device 120 hence transmits uplink data UL in the uplink transmission occasions before and after the reserved transmission period T5 but not during the reserved transmission period T5. In this way, intra-cell interference can be avoided and the latency of the communication between the network access node 300 and the first communication device 100 can be minimized.
  • the first communication device 100 and the second communication device 120 in this disclosure includes but is not limited to: a UE such as a smart phone, a cellular phone, a cordless phone, a session initiation protocol (SIP) phone, a wireless local loop (WLL) station, a personal digital assistant (PDA), a handheld device having a communication function, a computing device or another processing device connected to a wireless modem, an in-vehicle device, a wearable device, an integrated access and backhaul node (IAB) such as mobile car or equipment installed in a car, a drone, a device-to-device (D2D) device, a wireless camera, a mobile station, an access terminal, an user unit, a communication device, a station of wireless local access network (WLAN), a wireless enabled tablet computer, a laptop- embedded equipment, an universal serial bus (USB) dongle, a wireless customer-premises equipment (CPE), and/or a chipset.
  • IOT Internet of things
  • the UE may further be referred to as a mobile telephone, a cellular telephone, a computer tablet or laptop with wireless capability.
  • the UE in this context may e.g. be portable, pocket- storable, hand-held, computer-comprised, or vehicle-mounted mobile device, enabled to communicate voice and/or data, via the radio access network, with another entity, such as another receiver or a server.
  • the UE can be a station (STA), which is any device that contains an IEEE 802.11 -conformant media access control (MAC) and physical layer (PHY) interface to the wireless medium (WM).
  • STA station
  • the UE may also be configured for communication in 3GPP related LTE and LTE-Advanced, in WiMAX and its evolution, and in fifth generation wireless technologies, such as NR.
  • the network access node 300 in this disclosure includes but is not limited to: a NodeB in wideband code division multiple access (WCDMA) system, an evolutional Node B (eNB) or an evolved NodeB (eNodeB) in LTE systems, or a relay node or an access port, or an in-vehicle device, a wearable device, or a gNB in the fifth generation (5G) networks.
  • WCDMA wideband code division multiple access
  • eNB evolutional Node B
  • eNodeB evolved NodeB
  • gNB fifth generation
  • the network access node 300 herein may be denoted as a radio network access node, an access network access node, an access port, or a base station, e.g.
  • radio base station which in some networks may be referred to as transmitter, “gNB”, “gNodeB”, “eNB”, “eNodeB”, “NodeB” or “B node”, depending on the technology and terminology used.
  • the radio network access nodes may be of different classes such as e.g. macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size.
  • the radio network access node can be a station (ST A), which is any device that contains an IEEE 802.11 -conformant MAC and PHY interface to the wireless medium.
  • the radio network access node may also be a base station corresponding to the 5G wireless systems.
  • any method according to embodiments of the invention may be implemented in a computer program, having code means, which when run by processing means causes the processing means to execute the steps of the method.
  • the computer program is included in a computer readable medium of a computer program product.
  • the computer readable medium may comprise essentially any memory, such as a ROM (Read-Only Memory), a PROM (Programmable Read-Only Memory), an EPROM (Erasable PROM), a Flash memory, an EEPROM (Electrically Erasable PROM), or a hard disk drive.
  • Examples of other such means, units, elements and functions are: processors, memory, buffers, control logic, encoders, decoders, rate matchers, de-rate matchers, mapping units, multipliers, decision units, selecting units, switches, interleavers, de-interleavers, modulators, demodulators, inputs, outputs, antennas, amplifiers, receiver units, transmitter units, DSPs, MSDs, TCM encoder, TCM decoder, power supply units, power feeders, communication interfaces, communication protocols, etc. which are suitably arranged together for performing the solution.
  • the processor(s) of the first communication device 100, the second communication device 120, and the network access node 300 may comprise, e.g., one or more instances of a Central Processing Unit (CPU), a processing unit, a processing circuit, a processor, an Application Specific Integrated Circuit (ASIC), a microprocessor, or other processing logic that may interpret and execute instructions.
  • CPU Central Processing Unit
  • ASIC Application Specific Integrated Circuit
  • the expression “processor” may thus represent a processing circuitry comprising a plurality of processing circuits, such as, e.g., any, some or all of the ones mentioned above.
  • the processing circuitry may further perform data processing functions for inputting, outputting, and processing of data comprising data buffering and device control functions, such as call processing control, user interface control, or the like.

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

L'invention concerne la réduction de la latence lorsqu'un premier dispositif de communication et un nœud d'accès au réseau communiquent l'un avec l'autre dans un spectre sans licence à l'aide d'une procédure d'écoute avant de parler. Le nœud d'accès au réseau transmet un premier paquet de données et un second paquet de données suivant le premier paquet de données vers le premier dispositif de communication. Le premier dispositif de communication transmet une première rétroaction associée au premier paquet de données au nœud d'accès au réseau. Le second paquet de données comprend au moins une partie du premier paquet de données et est transmis pour maintenir un intervalle de temps entre la fin de la transmission du second paquet de données et le début de la transmission de la première rétroaction inférieure à une valeur seuil. Ainsi, le premier dispositif de communication 100 est autorisé à transmettre la première rétroaction sans réaliser d'écoute avant de parler et, par conséquent, évite une défaillance d'écoute avant de parler.
PCT/EP2020/062267 2020-05-04 2020-05-04 Premier dispositif de communication et nœud d'accès au réseau pour réduire la latence dans un spectre sans licence à l'aide d'une procédure d'écoute avant de parler WO2021223833A1 (fr)

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