WO2019214796A1 - Client device and network access node for maintaining uplink time-syncronization - Google Patents

Client device and network access node for maintaining uplink time-syncronization Download PDF

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Publication number
WO2019214796A1
WO2019214796A1 PCT/EP2018/061654 EP2018061654W WO2019214796A1 WO 2019214796 A1 WO2019214796 A1 WO 2019214796A1 EP 2018061654 W EP2018061654 W EP 2018061654W WO 2019214796 A1 WO2019214796 A1 WO 2019214796A1
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WO
WIPO (PCT)
Prior art keywords
uplink
client device
network access
access node
activity timer
Prior art date
Application number
PCT/EP2018/061654
Other languages
French (fr)
Inventor
Bengt Lindoff
Gustaf Claeson
Rama Kumar MOPIDEVI
Wenquan HU
Thorsten Schier
Original Assignee
Huawei Technologies Co., Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Huawei Technologies Co., Ltd. filed Critical Huawei Technologies Co., Ltd.
Priority to PCT/EP2018/061654 priority Critical patent/WO2019214796A1/en
Publication of WO2019214796A1 publication Critical patent/WO2019214796A1/en

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W56/00—Synchronisation arrangements
    • H04W56/004—Synchronisation arrangements compensating for timing error of reception due to propagation delay
    • H04W56/0045—Synchronisation arrangements compensating for timing error of reception due to propagation delay compensating for timing error by altering transmission time
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W74/00—Wireless channel access, e.g. scheduled or random access
    • H04W74/08—Non-scheduled or contention based access, e.g. random access, ALOHA, CSMA [Carrier Sense Multiple Access]
    • H04W74/0833—Non-scheduled or contention based access, e.g. random access, ALOHA, CSMA [Carrier Sense Multiple Access] using a random access procedure

Definitions

  • the invention relates to a client device and a network access node for maintaining uplink time- synchronization. Furthermore, the invention also relates to corresponding methods and a computer program.
  • 5G fifth-generation
  • NR new radio
  • ultra-low latency services where latency corresponds to the time required for transmitting a data packet through the network.
  • the current fourth-generation (4G) wireless cellular communication system LTE
  • LTE Long Term Evolution
  • BLER target block error rate
  • URLLC services will require the user equipment (UE) to be in-synchronization with the serving cell and in an active state, while the URLLC service is ongoing. Furthermore, a variety of URLLC services can be expected from so called chatty applications with frequent transmission of small data packets with tough latency and reliability requirements, to alarm systems where sensors may in-frequently report alarms, but once alarming, the latency need to be short and reliability need to be high. A wide range of QoS levels for different URLLC services are therefore expected. Summary
  • An objective of embodiments of the invention is to provide a solution which mitigates or solves the drawbacks and problems of conventional solutions.
  • a client device for a wireless communication system the client device being configured to
  • control message indicates a value for an uplink in-activity timer
  • the uplink in-activity timer can in this disclosure be understood to mean a timer which counts time elapsed since an event associated with an uplink transmission to the network access node has occurred.
  • the at least one uplink signal in this disclosure is an uplink signal which is not a random access signal.
  • An advantage of the client device according to the first aspect is that the client device can transmit an uplink signal before the uplink time-synchronization becomes unreliable. Thereby, uplink time-synchronization to the network access node can be maintained and QoS for low latency and/or high reliability services can be guaranteed.
  • the client device is further configured to
  • the client device transmits the uplink signal for maintaining uplink time-synchronization to the network access at a well defined time. Thereby, QoS for low latency and/or high reliability services can be guaranteed.
  • the client device is further configured to
  • An advantage with this implementation form is that the client device transmits the uplink signal before the uplink time-synchronization becomes unreliable. Thereby, uplink time- synchronization to the network access node can be maintained and QoS for low latency and/or high reliability services can be guaranteed.
  • control message indicates time-frequency resources associated with the uplink signal
  • client device is further configured to
  • An advantage with this implementation form is that the network access node can control which time-frequency resources the client device uses to transmit the uplink signal. Hence, the network access node can freely choose uplink time-frequency resources for the uplink time- synchronization signalling, and thereby an improved cell capacity can be achieved.
  • the uplink in-activity timer is a time alignment timer.
  • An advantage with this implementation form is that an already defined timer can be reused to maintain uplink time-synchronization to the network access node and thereby overhead signalling can be reduced.
  • the event is an uplink transmission to the network access node.
  • an advantage with this implementation form is that a well defined time instant for when to start the uplink in-activity timer is defined, and thereby a consistent behaviour for maintaining the uplink time-synchronization to the network access node can be achieved.
  • the event is a reception of downlink control information associated with an uplink transmission to the network access node.
  • An advantage with this implementation form is that a well defined time instant for when to start the uplink in-activity timer is defined, and thereby a consistent behaviour for maintaining the uplink time-synchronization to the network access node can be achieved.
  • the uplink signal is any of
  • the type of uplink signal used by the client device can e.g. be pre-defined e.g. in a standard, signalled by the network access node, or a combination of pre-defined and signalled.
  • An advantage with this implementation form is that the uplink signalling for maintaining uplink time-synchronization to the network access node uses signals which are defined for fast response, in comparison to e.g. using random access procedures. Hence, faster maintenance of uplink time-synchronization to the network access node can be achieved over prior art techniques, thereby improving the QoS.
  • the client device is further configured to
  • An advantage with this implementation form is that the client device adapts its uplink timing to a timing determined by the network access node and thereby the risk for generating uplink interference with other users is minimized.
  • the uplink is configured for services having at least one of a latency constraint and a reliability constraint.
  • At least one of the latency constraint and the reliability constraint is associated with at least one of: a quality of service flow identity, a network slice selection assistance information configuration, a radio resource control parameter, and a medium access control parameter.
  • An advantage with this implementation form is that well defined parameters are used to identify services requiring continuous time-synchronization. Thereby, overall overhead signalling in the cellular system can be minimized and cell capacity can be improved.
  • a network access node for a wireless communication system the network access node being configured to
  • control message indicates the value of the uplink in-activity timer.
  • An advantage of a network access node according to the second aspect is that the network access node can configure the client device with a suitable value for the uplink in-activity timer and hence control for how long uplink time-synchronization is considered to be reliable. Thereby, making it possible to optimize the trade-off between overhead signalling and QoS needed for low latency and/or high reliability services.
  • the network access node is further configured to
  • the network access node can maintain uplink time-synchronization for the client device and thereby minimizes the risk that the client device creates and is affected by interference for/to other client devices in the uplink.
  • control message indicates time-frequency resources associated with the uplink signal.
  • An advantage with this implementation form is that the network access node can determine suitable resources for the uplink time-synchronization signalling based on for instance current cell load and thereby optimize the cell capacity.
  • the above mentioned and other objectives are achieved with a method for a client device, the method comprises
  • control message indicates a value for an uplink in-activity timer
  • an implementation form of the method comprises the feature(s) of the corresponding implementation form of the client device.
  • the above mentioned and other objectives are achieved with a method for a network access node, the method comprises
  • control message indicates the value of the uplink in-activity timer.
  • an implementation form of the method comprises the feature(s) of the corresponding implementation form of the network access node.
  • 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. Further, 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 EPROM) and hard disk drive.
  • ROM Read-Only Memory
  • PROM Programmable ROM
  • EPROM Erasable PROM
  • Flash memory Flash memory
  • EEPROM Electrically EPROM
  • - Fig. 1 shows a client device according to an embodiment of the invention
  • FIG. 2 shows a method 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 according to an embodiment of the invention
  • FIG. 5 shows a wireless communication system according to an embodiment of the invention
  • FIG. 6 shows a flow chart of a method according to an embodiment of the invention
  • - Fig. 7 shows signalling between a network access node and a client device according to an embodiment of the invention.
  • timing advance control is used to initiate and maintain uplink time-synchronization for a UE.
  • a network access node e.g. in NR a so called next generation nodeB (gNB)
  • gNB next generation nodeB
  • the random access request is further used as timing reference for uplink during e.g. radio link failure and handover.
  • the gNB Upon receiving a random access request, calculates the timing advance value and transmits the timing advance value to the UE in a timing advance command as part of a random access response.
  • the gNB continuously estimates timing advance for the UE and transmits a timing advance command to the UE if a correction of the uplink timing is required.
  • the UE adjusts the timing of its uplink transmission at subframe #n+6 for a timing advance command received in downlink subframe #n.
  • other numbers may be applicable.
  • the gNB further provides the UE with a configurable timer, a so called time alignment timer (TimeAlignmentTimer), for each timing advance group.
  • a timing advance group comprises one or more serving cells with the same uplink timing advance.
  • the TimeAlignmentTimer for a timing advance group controls how long the UE considers the serving cells belonging to the timing advance group to be uplink time aligned.
  • the TimeAlignmentTimer is normally re-started whenever the UE receives a new timing advance command from the gNB. If the TimeAlignmentTimer for the timing advance group expires, the serving cells belonging to the timing advance group are no longer considered to be uplink time aligned.
  • the UE does not perform any uplink transmission on the serving cells belonging to the timing advance group except a random access preamble transmission.
  • the random access preamble is transmitted to restore uplink time-synchronization.
  • the random access preamble is transmitted first when the UE has data to transmit or receive.
  • the latency of the random access procedure becomes a problem.
  • a client device 100 is configured to maintain uplink time-synchronization to a network access node 300 by using a new signalling procedure which prevents the client device 100 from losing its uplink time-synchronization.
  • Fig. 1 shows a client device 100 according to an embodiment of the invention.
  • the client device 100 comprises a processor 102, a transceiver 104 and a memory 106.
  • the processor 102 is coupled to the transceiver 104 and the memory 106 by communication means 108 known in the art.
  • the client device 100 further comprises an antenna or antenna array 1 10 coupled to the transceiver 104, which means that the client device 100 is configured for wireless communications in a wireless communication system. That the client device 100 is configured to perform certain actions can in this disclosure be understood to mean that the client device 100 comprises suitable means, such as e.g. the processor 102 and the transceiver 104, configured to perform said actions.
  • the client device 100 is configured to receive a control message 510 from a network access node 300.
  • the control message 510 indicates a value for an uplink in-activity timer.
  • the client device 100 is further configured to start the uplink in-activity timer based on an event associated with an uplink transmission to the network access node 300 and transmit at least one uplink signal 520 to the network access node 300 based on the uplink in-activity timer, e.g. upon expiry of the uplink in-activity timer.
  • the at least one uplink signal 520 is a signal defined for fast response as will be described below with reference to Fig. 6. Hence, the at least one uplink signal 520 is not a signal in a random access procedure (like a random access preamble).
  • Fig. 2 shows a flow chart of a corresponding method 200 which may be executed in a client device 100, such as the one shown in Fig. 1 .
  • the method 200 comprises receiving 202 a control message 510 from a network access node 300.
  • the control message 510 indicates a value for an uplink in-activity timer.
  • the method 200 further comprises starting 204 the uplink in-activity timer based on an event associated with an uplink transmission to the network access node 300 and transmitting 206 at least one uplink signal 520 to the network access node 300 based on the uplink in-activity timer.
  • 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 obtain a value for an uplink in-activity timer for a client device 100 and transmit a control message 510 indicating the value of the uplink in activity timer to the client device 100.
  • 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 obtaining 402 a value for an uplink in-activity timer for a client device 100 and transmitting 404 a control message 510 indicating the value of the uplink in-activity timer to the client device 100.
  • Fig. 5 shows a wireless communication system 500 according to an embodiment of the invention.
  • the wireless communication system 500 comprises a client device 100 and a network access node 300 configured to operate in the wireless communication system 500.
  • the wireless communication system 500 shown in Fig. 5 only comprises one client device 100 and one network access node 300.
  • the wireless communication system 500 may comprise any number of client devices 100 and network access nodes 300 without deviating from the scope of the invention.
  • a wireless connection 502 is setup between the client device 100 and the network access node 300.
  • the wireless connection 502 can be set up according to procedures defined in communication standards, such as 3GPP, and enables data transmission (downlink) from the network access node 300 to the client device 100.
  • the wireless connection 502 can also be configured for data transmission (uplink) from the client device 100 to the network access node 300.
  • the wireless connection 502 is assumed to be configured for a service which has strict latency and/or reliability constraints, e.g. a URLLC service. Hence, it becomes important for the client device 100 to maintain the uplink time-synchronization for the wireless connection 502 to the network access node 300 so as to meet the latency and/or reliability constraints.
  • the client device 100 is therefore configured by the network access node 300 with an uplink in-activity timer. Based on the uplink in-activity timer the client device 100 transmits an uplink signal 520 which can be used by the network access node 300 for timing advance control, as will now be described with reference to Fig. 6.
  • Fig. 6 shows a flow chart of a method 600 for uplink signaling based on an uplink in-activity timer according to an embodiment of the invention.
  • the method 600 may be performed in a client device, such as e.g. the client device 100 shown in Fig. 1 , which is connected to a network access node 300 over a wireless connection 502.
  • the method 600 may in embodiments be performed when the wireless connection 502 of the client device 100 is configured for a service having at least one of a latency constraint and a reliability constraint, i.e. when the uplink of the wireless connection 502 is configured for services having at least one of a latency constraint and a reliability constraint.
  • At least one of the latency constraint and the reliability constraint may be associated with at least one of: a quality of service flow identity, a network slice selection assistance information configuration, a radio resource control (RRC) parameter, and a medium access control (MAC) parameter. These parameters may be configured by the network access node 300.
  • the quality of service flow identity and network slice selection assistance information configuration may be higher layer signaling (non-access stratum) indicating the current service and service requirements configured for the client device 100.
  • Each such service configuration has certain reliability and latency requirements, and a processing unit in the client device 100 may determine from the service configurations whether the client device 100 is configured for low latency and/or high reliability services.
  • the service configurations mentioned above is mirrored down to the RRC or MAC layer, and corresponds to a RRC or a MAC configuration.
  • a processing unit in the client device 100 may determine from the RRC or MAC configuration (RRC or MAC parameters) whether the client device 100 is configured for low latency and/or high reliability services.
  • the service may be a service with strict latency constraint and/or reliability constraint, such as e.g. an URLLC service requiring residual block error rate (BLER) of 10e-5 and latency of 1 ms.
  • the client device 100 may determine the latency constraint of the service e.g. based on a delay threshold for the service, where the delay may correspond to an end-to-end delay or a radio access network delay, such as packet delay budget.
  • the client device 100 may determine the reliability constraint e.g. based on an error rate threshold for the service, where the error rate may correspond to a packet error rate or a block error rate.
  • the corresponding thresholds described above may be explicitly configured by the network access node 300 or implicitly determined by client device 100 from a certain service configuration, such as the ones described above.
  • the client device 100 receives a control message 510 indicating a value for an uplink in-activity timer from a network access node 300.
  • the network access node 300 configures the client device 100 with a value for the uplink in-activity timer.
  • the uplink in-activity timer may in one case be a time alignment timer, such as a conventional time alignment timer configured for the client device 100. In this case, the client device 100 may hence reuse the configured time alignment timer for determining uplink in-activity.
  • the control message 510 may further comprise additional information associated to an uplink signal 520 which the client device 100 transmits based on the uplink in-activity timer. The additional information may e.g.
  • the additional information may instead be at least partly pre-defined in a standard.
  • the network access node 300 may signal no additional information or only signal a subset of the additional information in the control message 510.
  • the client device 100 monitors for events associated with an uplink transmission to the network access node 300.
  • the event may e.g. be an uplink transmission to the network access node 300.
  • the event may further be a reception of downlink control information associated with an uplink transmission to the network access node 300.
  • the client device 100 determines in step 606 if an event associated with an uplink transmission to the network access node 300 has been detected. If an event associated with an uplink transmission to the network access node 300 has been detected, i.e. the outcome of the determination in step 606 is YES, the client device 100 starts the uplink in-activity timer in step 608. The uplink in-activity timer is started with the value for the uplink in-activity timer which was received from the network access node 300 in step 602. On the other hand, if an event associated with an uplink transmission to the network access node 300 has not been detected in 606, i.e. the outcome of the determination in step 606 is NO, the client device 100 continuous to monitor for events associated with an uplink transmission to the network access node 300 in step 604.
  • the client device 100 transmits at least one uplink signal 520 to the network access node 300 based on the uplink in-activity timer started in step 608.
  • the client device 100 may transmit the uplink signal 520 to the network access node 300 upon expiry of the uplink in-activity timer.
  • the uplink in-activity timer may e.g. expire when it reaches zero or the value received from the network access node 300, depending on if the uplink in-activity timer is implemented to count up or count down.
  • client device 100 may instead transmit the uplink signal 520 before the uplink in-activity timer expires, e.g. a time threshold value before the uplink in-activity timer expires.
  • the client device 100 may in embodiments transmit the uplink signal 520 to the network access node 300 prior to expiry of the uplink in-activity timer with a time threshold value. If the uplink in-activity timer started in step 608 is reset and restarted, e.g. due to an uplink transmission or a reception of downlink control information indicating uplink transmission request, step 610 will not be performed, instead the client device 100 will continue to monitor for events associated with an uplink transmission to the network access node 300 in step 604.
  • the uplink signal 520 transmitted by the client device 100 in step 610 may e.g. be any of a signal associated with a physical uplink shared channel (PUSCH), a signal associated with a physical uplink control channel (PUCCH), and a sounding reference signal (SRS).
  • the uplink signal 520 is not a signal associated with a random access channel. In this way, the uplink signal 520 is a signal which is defined for fast response, in comparison to using a random access signal. Hence, a fast procedure for maintaining uplink time-synchronization to the network access node 300 is achieved.
  • the signal associated with the PUSCH or the PUCCH may e.g. be uplink control information (UCI) comprising a scheduling request (SR) or channel status information (CSI).
  • UCI uplink control information
  • SR scheduling request
  • CSI channel status information
  • the CSI may in turn be an aperiodic-CSI or low latency-CSI and e.g. comprise a channel quality indicator (CQI) report.
  • the signal associated with the PUSCH may further e.g. be a layer 3 measurement report.
  • the signal associated with the PUCCH may further e.g. be a scheduling request (SR).
  • the type of uplink signal transmitted by the client device 100 in step 610 may e.g. be pre-defined by a standard, signalled by the network access node 300, or a combination of pre-defined and signalled. In case the network access node 300 signals information specifying the type of uplink signal to be used by the client device 100, this information may e.g. be comprised in the control message 510, as described above with reference to step 602.
  • the client device 100 may transmit the uplink signal 520 in a time-frequency resources indicated by the network access node 300.
  • the time-frequency resources associated with the uplink signal 520 may in this case be indicated in the control message 520 received from the network access node 300, as described above with reference to step 602.
  • the network access node 300 may perform timing advance control based on the received uplink signal 520, as will now be described with reference to Fig. 7.
  • Fig. 7 shows signaling between the network access node 300 and the client device 100 according to an embodiment.
  • the network access node 300 obtains a value for an uplink in-activity timer for a client device 100.
  • the network access node 300 may obtain the value for the uplink in-activity timer based on one or more factors associated with e.g. radio environment, services configured for the client device 100, and load in the network and/or in the network access node 300.
  • the network access node 300 may in embodiments obtain the uplink in-activity timer based on radio environment factors such as e.g. cell layout, i.e. based on how large movements the client device 100 can be expected to perform within a cell.
  • a lower value may be configured for the uplink in-activity timer compared to in a small (pico) cell.
  • the network access node 300 may further obtain the value for the uplink in-activity timer based on services configured for the client device 100.
  • a lower value e.g. 500 ms
  • eMBB enhanced mobile broadband
  • a higher value e.g. 2 s
  • the network access node 300 transmits a control message 510 indicating the obtained value of the uplink in-activity timer to the client device 100, as shown in step II in Fig. 7.
  • the control message 510 may further comprise additional information, such as e.g. information indicating time-frequency resources associated with an uplink signal 520.
  • the network access node 300 may receive at least one uplink signal 520 from the client device 100.
  • the client device 100 transmits one uplink signal 520, as shown in step III in Fig. 7.
  • the client device 100 may transmit more than one uplink signal 520.
  • the control message 510 may order the client device 100 to transmit a data packet, e.g. a measurement report.
  • the client device 100 may need to first transmit an uplink signal 520 comprising a buffer status report, and then transmit the actual data packet, i.e. another uplink signal 520, when the network access node 300 has allocated resources for the data packet.
  • multiple uplink signals 520 are transmitted in this case.
  • the client device 100 uses the uplink in-activity timer received in the control message 510 in step II in Fig. 7 as described above with reference to Fig. 6.
  • the uplink signal 520 in step III in Fig. 7 may e.g. be transmitted by the client device 100 upon expiry of the uplink in activity timer.
  • the client device 100 transmits the uplink signal 520 with the current timing advance, i.e. based on the latest timing advance value received from the network access node 300.
  • the network access node 300 determines in step IV in Fig. 7 a timing advance based on the received uplink signal 520 and a timing advance value 530 based on the determined timing advance. In step V in Fig. 7, the network access node 300 transmits the determined timing advance value 530 to the client device 100.
  • the timing advance and the timing advance value 530 may be determined based on conventional methods. Furthermore, the timing advance value 530 may e.g. be transmitted in a timing advance command known in the art.
  • the client device 100 receives the timing advance value 530 from the network access node 300.
  • the timing advance value 530 is received in response to the transmission of the uplink signal 520 to the network access node 300. Based on the received timing advance value 530, the client device 100 time adjust uplink transmissions to the network access node 300. Thus, the next time the client device 100 has an uplink transmission to the network access node 300, the uplink transmission will be transmitted based on the timing advance value 530 (not shown in Fig. 7) received from the network access node 300 which means that the uplink time- synchronization is adapted to the timing advance value 530.
  • the client device 100 herein, may be denoted as a user device, a User Equipment (UE), a mobile station, an internet of things (loT) device, a sensor device, a wireless terminal and/or a mobile terminal, is enabled to communicate wirelessly in a wireless communication system, sometimes also referred to as a cellular radio system.
  • the UEs may further be referred to as mobile telephones, cellular telephones, computer tablets or laptops with wireless capability.
  • the UEs in this context may be, for example, portable, pocket-storable, hand-held, computer- comprised, or vehicle-mounted mobile devices, 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 802.1 1 -conformant Media Access Control (MAC) and Physical Layer (PHY) interface to the Wireless Medium (WM).
  • STA Station
  • MAC Media Access Control
  • PHY Physical Layer
  • 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 New Radio.
  • the network access node 300 herein may also be denoted as a radio client device, an access client device, an access point, or a base station, e.g. a Radio Base Station (RBS), 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.
  • RBS Radio Base Station
  • the radio client devices 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 client device can be a Station (STA), which is any device that contains an IEEE 802.1 1 -conformant Media Access Control (MAC) and Physical Layer (PHY) interface to the Wireless Medium (WM).
  • STA Station
  • the radio client device may also be a base station corresponding to the fifth generation (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.
  • ROM Read-Only Memory
  • PROM PROM
  • EPROM Erasable PROM
  • Flash memory an EEPROM (Electrically Erasable PROM), or a hard disk drive.
  • embodiments of the client device 100 and the network access node 300 comprises the necessary communication capabilities in the form of e.g., functions, means, units, elements, etc., for performing the solution.
  • 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 client device 100 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.
  • 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.

Abstract

The invention relates to maintaining uplink time-synchronization for a client device (100) to a network access node (300). Based on an uplink in-activity timer received from the network access node (300), the client device (100) transmits an uplink signal (520) to the network access node (300). The client device (100) may e.g. start the uplink in-activity timer upon an uplink transmission to the network access node (300) and transmit the uplink signal (520) to the network access node (300) when the uplink in-activity timer expires. The uplink signal (520) can be used by the network access node (300) to determine the timing advance for the client device (100) and if necessary adjust the timing advance. Thereby, uplink time-synchronization can be maintained for the client device (100), resulting in reduced delays for uplink and downlink transmission.

Description

CLIENT DEVICE AND NETWORK ACCESS NODE FOR MAINTAINING UPLINK TIME- SYNCRONIZATION
Technical Field
The invention relates to a client device and a network access node for maintaining uplink time- synchronization. Furthermore, the invention also relates to corresponding methods and a computer program.
Background
The growth of wireless data traffic over the past three decades has been relentless. The upcoming fifth-generation (5G) wireless cellular communication system, new radio (NR), is expected to carry 1000 times more traffic while maintaining high reliability. Another critical requirement of 5G is support for ultra-low latency services, where latency corresponds to the time required for transmitting a data packet through the network.
The current fourth-generation (4G) wireless cellular communication system, LTE, have a nominal latency of about 50ms. However, this is currently unpredictable and can go up to several seconds. Moreover, it is mainly optimized for mobile broadband traffic with target block error rate (BLER) of 10e-1 before re-transmission.
There is a consensus that the future for many services, e.g. industrial control, traffic safety, medical, and internet services, depends on wireless connectivity with guaranteed consistent latencies of 0.5ms or less, as well as exceedingly stringent reliability of residual BLER below 10e-5. The projected enormous capacity growth is achievable through conventional methods of moving to higher parts of the radio spectrum and network densifications. However, significant reductions in latency, while guaranteeing ultra reliability and low latency communication (URLLC) services, will put several challenges on the design of the 5G wireless communication system.
URLLC services will require the user equipment (UE) to be in-synchronization with the serving cell and in an active state, while the URLLC service is ongoing. Furthermore, a variety of URLLC services can be expected from so called chatty applications with frequent transmission of small data packets with tough latency and reliability requirements, to alarm systems where sensors may in-frequently report alarms, but once alarming, the latency need to be short and reliability need to be high. A wide range of QoS levels for different URLLC services are therefore expected. Summary
An objective of embodiments of the invention is to provide a solution which mitigates or solves the drawbacks and problems of conventional solutions.
The above and further objectives are solved by the subject matter of the independent claims. Further advantageous embodiments of the invention can be found in the dependent claims.
According to a first aspect of the invention, the above mentioned and other objectives are achieved with a client device for a wireless communication system, the client device being configured to
receive a control message from a network access node, wherein the control message indicates a value for an uplink in-activity timer;
start the uplink in-activity timer based on an event associated with an uplink transmission to the network access node;
transmit at least one uplink signal to the network access node based on the uplink in activity timer.
The uplink in-activity timer can in this disclosure be understood to mean a timer which counts time elapsed since an event associated with an uplink transmission to the network access node has occurred.
The at least one uplink signal in this disclosure is an uplink signal which is not a random access signal.
An advantage of the client device according to the first aspect is that the client device can transmit an uplink signal before the uplink time-synchronization becomes unreliable. Thereby, uplink time-synchronization to the network access node can be maintained and QoS for low latency and/or high reliability services can be guaranteed.
In an implementation form of a client device according to the first aspect, the client device is further configured to
transmit the uplink signal to the network access node upon expiry of the uplink in-activity timer.
An advantage with this implementation form is that the client device transmits the uplink signal for maintaining uplink time-synchronization to the network access at a well defined time. Thereby, QoS for low latency and/or high reliability services can be guaranteed. In an implementation form of a client device according to the first aspect, the client device is further configured to
transmit the uplink signal to the network access node prior to expiry of the uplink in activity timer with a time threshold value.
An advantage with this implementation form is that the client device transmits the uplink signal before the uplink time-synchronization becomes unreliable. Thereby, uplink time- synchronization to the network access node can be maintained and QoS for low latency and/or high reliability services can be guaranteed.
In an implementation form of a client device according to the first aspect, the control message indicates time-frequency resources associated with the uplink signal, and the client device is further configured to
transmit the uplink signal in the indicated time-frequency resources to the network access node.
An advantage with this implementation form is that the network access node can control which time-frequency resources the client device uses to transmit the uplink signal. Hence, the network access node can freely choose uplink time-frequency resources for the uplink time- synchronization signalling, and thereby an improved cell capacity can be achieved.
In an implementation form of a client device according to the first aspect, the uplink in-activity timer is a time alignment timer.
An advantage with this implementation form is that an already defined timer can be reused to maintain uplink time-synchronization to the network access node and thereby overhead signalling can be reduced.
In an implementation form of a client device according to the first aspect, the event is an uplink transmission to the network access node.
An advantage with this implementation form is that a well defined time instant for when to start the uplink in-activity timer is defined, and thereby a consistent behaviour for maintaining the uplink time-synchronization to the network access node can be achieved. In an implementation form of a client device according to the first aspect, the event is a reception of downlink control information associated with an uplink transmission to the network access node.
An advantage with this implementation form is that a well defined time instant for when to start the uplink in-activity timer is defined, and thereby a consistent behaviour for maintaining the uplink time-synchronization to the network access node can be achieved.
In an implementation form of a client device according to the first aspect, the uplink signal is any of
a signal associated with a physical uplink shared channel,
a signal associated with a physical uplink control channel, and
a sounding reference signal.
The type of uplink signal used by the client device can e.g. be pre-defined e.g. in a standard, signalled by the network access node, or a combination of pre-defined and signalled.
An advantage with this implementation form is that the uplink signalling for maintaining uplink time-synchronization to the network access node uses signals which are defined for fast response, in comparison to e.g. using random access procedures. Hence, faster maintenance of uplink time-synchronization to the network access node can be achieved over prior art techniques, thereby improving the QoS.
In an implementation form of a client device according to the first aspect, the client device is further configured to
receive a timing advance value from the network access node in response to the transmission of the uplink signal to the network access node;
time adjust uplink transmissions to the network access node based on the received timing advance value.
An advantage with this implementation form is that the client device adapts its uplink timing to a timing determined by the network access node and thereby the risk for generating uplink interference with other users is minimized.
In an implementation form of a client device according to the first aspect, the uplink is configured for services having at least one of a latency constraint and a reliability constraint. An advantage with this implementation form is that the uplink signalling procedure according to the invention is used for services requiring continuous time-synchronization. Thereby, overall overhead signalling in the cellular system can be minimized and cell capacity can be improved.
In an implementation form of a client device according to the first aspect, at least one of the latency constraint and the reliability constraint is associated with at least one of: a quality of service flow identity, a network slice selection assistance information configuration, a radio resource control parameter, and a medium access control parameter.
An advantage with this implementation form is that well defined parameters are used to identify services requiring continuous time-synchronization. Thereby, overall overhead signalling in the cellular system can be minimized and cell capacity can be improved.
According to a second aspect of the invention, the above mentioned and other objectives are achieved with a network access node for a wireless communication system, the network access node being configured to
obtain a value for an uplink in-activity timer for a client device;
transmit a control message to the client device, wherein the control message indicates the value of the uplink in-activity timer.
An advantage of a network access node according to the second aspect is that the network access node can configure the client device with a suitable value for the uplink in-activity timer and hence control for how long uplink time-synchronization is considered to be reliable. Thereby, making it possible to optimize the trade-off between overhead signalling and QoS needed for low latency and/or high reliability services.
In an implementation form of a network access node according to the first aspect, the network access node is further configured to
receive at least one uplink signal from the client device in response to the transmission of the control message to the client device;
determine a timing advance based on the received uplink signal;
determine a timing advance value based on the determined timing advance;
transmit the timing advance value to the client device. An advantage with this implementation form is that the network access node can maintain uplink time-synchronization for the client device and thereby minimizes the risk that the client device creates and is affected by interference for/to other client devices in the uplink.
In an implementation form of a network access node according to the first aspect, the control message indicates time-frequency resources associated with the uplink signal.
An advantage with this implementation form is that the network access node can determine suitable resources for the uplink time-synchronization signalling based on for instance current cell load and thereby optimize the cell capacity.
According to a third aspect of the invention, the above mentioned and other objectives are achieved with a method for a client device, the method comprises
receiving a control message from a network access node, wherein the control message indicates a value for an uplink in-activity timer;
starting the uplink in-activity timer based on an event associated with an uplink transmission to the network access node;
transmitting at least one uplink signal to the network access node based on the uplink in-activity timer.
The method according to the third aspect can be extended into implementation forms corresponding to the implementation forms of the client device according to the first aspect. Hence, an implementation form of the method comprises the feature(s) of the corresponding implementation form of the client device.
The advantages of the methods according to the third aspect are the same as those for the corresponding implementation forms of the client device according to the first aspect.
According to a fourth aspect of the invention, the above mentioned and other objectives are achieved with a method for a network access node, the method comprises
obtaining a value for an uplink in-activity timer for a client device;
transmitting a control message to the client device, wherein the control message indicates the value of the uplink in-activity timer.
The method according to the fourth aspect can be extended into implementation forms corresponding to the implementation forms of the network access node according to the second aspect. Hence, an implementation form of the method comprises the feature(s) of the corresponding implementation form of the network access node.
The advantages of the methods according to the fourth aspect are the same as those for the corresponding implementation forms of the network access node according to the second aspect.
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. Further, 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 EPROM) and hard disk drive.
Further applications and advantages of the embodiments of the invention will be apparent from the following detailed description.
Brief Description of the Drawings
The appended drawings are intended to clarify and explain different embodiments of the invention, in which:
- Fig. 1 shows a client device according to an embodiment of the invention;
- Fig. 2 shows a method 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 according to an embodiment of the invention;
- Fig. 5 shows a wireless communication system according to an embodiment of the invention;
- Fig. 6 shows a flow chart of a method according to an embodiment of the invention;
- Fig. 7 shows signalling between a network access node and a client device according to an embodiment of the invention.
Detailed Description
In LTE and for e.g. NR mobile broadband services, timing advance control is used to initiate and maintain uplink time-synchronization for a UE. A network access node, e.g. in NR a so called next generation nodeB (gNB), estimates the initial timing advance from a random access request sent by the UE during initial access. The random access request is further used as timing reference for uplink during e.g. radio link failure and handover. Upon receiving a random access request, the gNB calculates the timing advance value and transmits the timing advance value to the UE in a timing advance command as part of a random access response. Once the UE is in connected mode, the gNB continuously estimates timing advance for the UE and transmits a timing advance command to the UE if a correction of the uplink timing is required. In LTE, the UE adjusts the timing of its uplink transmission at subframe #n+6 for a timing advance command received in downlink subframe #n. In NR, other numbers may be applicable.
The gNB further provides the UE with a configurable timer, a so called time alignment timer (TimeAlignmentTimer), for each timing advance group. A timing advance group comprises one or more serving cells with the same uplink timing advance. The TimeAlignmentTimer for a timing advance group controls how long the UE considers the serving cells belonging to the timing advance group to be uplink time aligned. The TimeAlignmentTimer is normally re-started whenever the UE receives a new timing advance command from the gNB. If the TimeAlignmentTimer for the timing advance group expires, the serving cells belonging to the timing advance group are no longer considered to be uplink time aligned. In this case, the UE does not perform any uplink transmission on the serving cells belonging to the timing advance group except a random access preamble transmission. The random access preamble is transmitted to restore uplink time-synchronization. However, in conventional systems the random access preamble is transmitted first when the UE has data to transmit or receive. For service with strict latency and/or reliability constraints, such as e.g. ultra reliability and low latency communication (URLLC) services, the latency of the random access procedure becomes a problem.
This puts requirement on for instance uplink time-synchronization procedures defined in the NR standard for such services. Consequently, the inventors have identified a need to improve uplink time-synchronization procedures for low latency services such as e.g. URLLC services. Therefore, according to embodiments of the invention a client device 100 is configured to maintain uplink time-synchronization to a network access node 300 by using a new signalling procedure which prevents the client device 100 from losing its uplink time-synchronization.
Fig. 1 shows a client device 100 according to an embodiment of the invention. In the embodiment shown in Fig. 1 , the client device 100 comprises a processor 102, a transceiver 104 and a memory 106. The processor 102 is coupled to the transceiver 104 and the memory 106 by communication means 108 known in the art. The client device 100 further comprises an antenna or antenna array 1 10 coupled to the transceiver 104, which means that the client device 100 is configured for wireless communications in a wireless communication system. That the client device 100 is configured to perform certain actions can in this disclosure be understood to mean that the client device 100 comprises suitable means, such as e.g. the processor 102 and the transceiver 104, configured to perform said actions.
According to embodiments of the invention the client device 100 is configured to receive a control message 510 from a network access node 300. The control message 510 indicates a value for an uplink in-activity timer. The client device 100 is further configured to start the uplink in-activity timer based on an event associated with an uplink transmission to the network access node 300 and transmit at least one uplink signal 520 to the network access node 300 based on the uplink in-activity timer, e.g. upon expiry of the uplink in-activity timer. The at least one uplink signal 520 is a signal defined for fast response as will be described below with reference to Fig. 6. Hence, the at least one uplink signal 520 is not a signal in a random access procedure (like a random access preamble).
Fig. 2 shows a flow chart of a corresponding method 200 which may be executed in a client device 100, such as the one shown in Fig. 1 . The method 200 comprises receiving 202 a control message 510 from a network access node 300. The control message 510 indicates a value for an uplink in-activity timer. The method 200 further comprises starting 204 the uplink in-activity timer based on an event associated with an uplink transmission to the network access node 300 and transmitting 206 at least one uplink signal 520 to the network access node 300 based on the uplink in-activity timer.
Fig. 3 shows a network access node 300 according to an embodiment of the invention. In the embodiment shown in Fig. 3, 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.
That 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 obtain a value for an uplink in-activity timer for a client device 100 and transmit a control message 510 indicating the value of the uplink in activity timer to the client device 100.
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 obtaining 402 a value for an uplink in-activity timer for a client device 100 and transmitting 404 a control message 510 indicating the value of the uplink in-activity timer to the client device 100.
Fig. 5 shows a wireless communication system 500 according to an embodiment of the invention. The wireless communication system 500 comprises a client device 100 and a network access node 300 configured to operate in the wireless communication system 500. For simplicity, the wireless communication system 500 shown in Fig. 5 only comprises one client device 100 and one network access node 300. However, the wireless communication system 500 may comprise any number of client devices 100 and network access nodes 300 without deviating from the scope of the invention.
In the embodiment shown in Fig. 5, a wireless connection 502 is setup between the client device 100 and the network access node 300. The wireless connection 502 can be set up according to procedures defined in communication standards, such as 3GPP, and enables data transmission (downlink) from the network access node 300 to the client device 100. However, the wireless connection 502 can also be configured for data transmission (uplink) from the client device 100 to the network access node 300. Further, the wireless connection 502 is assumed to be configured for a service which has strict latency and/or reliability constraints, e.g. a URLLC service. Hence, it becomes important for the client device 100 to maintain the uplink time-synchronization for the wireless connection 502 to the network access node 300 so as to meet the latency and/or reliability constraints. According to embodiments of the invention the client device 100 is therefore configured by the network access node 300 with an uplink in-activity timer. Based on the uplink in-activity timer the client device 100 transmits an uplink signal 520 which can be used by the network access node 300 for timing advance control, as will now be described with reference to Fig. 6.
Fig. 6 shows a flow chart of a method 600 for uplink signaling based on an uplink in-activity timer according to an embodiment of the invention. The method 600 may be performed in a client device, such as e.g. the client device 100 shown in Fig. 1 , which is connected to a network access node 300 over a wireless connection 502. Furthermore, the method 600 may in embodiments be performed when the wireless connection 502 of the client device 100 is configured for a service having at least one of a latency constraint and a reliability constraint, i.e. when the uplink of the wireless connection 502 is configured for services having at least one of a latency constraint and a reliability constraint. At least one of the latency constraint and the reliability constraint may be associated with at least one of: a quality of service flow identity, a network slice selection assistance information configuration, a radio resource control (RRC) parameter, and a medium access control (MAC) parameter. These parameters may be configured by the network access node 300. For example, the quality of service flow identity and network slice selection assistance information configuration may be higher layer signaling (non-access stratum) indicating the current service and service requirements configured for the client device 100. Each such service configuration has certain reliability and latency requirements, and a processing unit in the client device 100 may determine from the service configurations whether the client device 100 is configured for low latency and/or high reliability services. In some embodiments, the service configurations mentioned above is mirrored down to the RRC or MAC layer, and corresponds to a RRC or a MAC configuration. In this case, a processing unit in the client device 100 may determine from the RRC or MAC configuration (RRC or MAC parameters) whether the client device 100 is configured for low latency and/or high reliability services.
The service may be a service with strict latency constraint and/or reliability constraint, such as e.g. an URLLC service requiring residual block error rate (BLER) of 10e-5 and latency of 1 ms. The client device 100 may determine the latency constraint of the service e.g. based on a delay threshold for the service, where the delay may correspond to an end-to-end delay or a radio access network delay, such as packet delay budget. Furthermore, the client device 100 may determine the reliability constraint e.g. based on an error rate threshold for the service, where the error rate may correspond to a packet error rate or a block error rate. The corresponding thresholds described above may be explicitly configured by the network access node 300 or implicitly determined by client device 100 from a certain service configuration, such as the ones described above.
In step 602, the client device 100 receives a control message 510 indicating a value for an uplink in-activity timer from a network access node 300. In other words, the network access node 300 configures the client device 100 with a value for the uplink in-activity timer. The uplink in-activity timer may in one case be a time alignment timer, such as a conventional time alignment timer configured for the client device 100. In this case, the client device 100 may hence reuse the configured time alignment timer for determining uplink in-activity. The control message 510 may further comprise additional information associated to an uplink signal 520 which the client device 100 transmits based on the uplink in-activity timer. The additional information may e.g. indicate the type of uplink signal to transmit, time-frequency resources associated with the uplink signal, specific transmission signatures, and signal procedures to use. However, in embodiments of the invention the additional information may instead be at least partly pre-defined in a standard. In this case, the network access node 300 may signal no additional information or only signal a subset of the additional information in the control message 510.
In step 604, the client device 100 monitors for events associated with an uplink transmission to the network access node 300. The event may e.g. be an uplink transmission to the network access node 300. The event may further be a reception of downlink control information associated with an uplink transmission to the network access node 300.
Based on the monitoring in step 604, the client device 100 determines in step 606 if an event associated with an uplink transmission to the network access node 300 has been detected. If an event associated with an uplink transmission to the network access node 300 has been detected, i.e. the outcome of the determination in step 606 is YES, the client device 100 starts the uplink in-activity timer in step 608. The uplink in-activity timer is started with the value for the uplink in-activity timer which was received from the network access node 300 in step 602. On the other hand, if an event associated with an uplink transmission to the network access node 300 has not been detected in 606, i.e. the outcome of the determination in step 606 is NO, the client device 100 continuous to monitor for events associated with an uplink transmission to the network access node 300 in step 604.
In step 610, the client device 100 transmits at least one uplink signal 520 to the network access node 300 based on the uplink in-activity timer started in step 608. According to embodiments of the invention the client device 100 may transmit the uplink signal 520 to the network access node 300 upon expiry of the uplink in-activity timer. The uplink in-activity timer may e.g. expire when it reaches zero or the value received from the network access node 300, depending on if the uplink in-activity timer is implemented to count up or count down. However, client device 100 may instead transmit the uplink signal 520 before the uplink in-activity timer expires, e.g. a time threshold value before the uplink in-activity timer expires. Thus, the client device 100 may in embodiments transmit the uplink signal 520 to the network access node 300 prior to expiry of the uplink in-activity timer with a time threshold value. If the uplink in-activity timer started in step 608 is reset and restarted, e.g. due to an uplink transmission or a reception of downlink control information indicating uplink transmission request, step 610 will not be performed, instead the client device 100 will continue to monitor for events associated with an uplink transmission to the network access node 300 in step 604.
The uplink signal 520 transmitted by the client device 100 in step 610 may e.g. be any of a signal associated with a physical uplink shared channel (PUSCH), a signal associated with a physical uplink control channel (PUCCH), and a sounding reference signal (SRS). The uplink signal 520 is not a signal associated with a random access channel. In this way, the uplink signal 520 is a signal which is defined for fast response, in comparison to using a random access signal. Hence, a fast procedure for maintaining uplink time-synchronization to the network access node 300 is achieved. The signal associated with the PUSCH or the PUCCH may e.g. be uplink control information (UCI) comprising a scheduling request (SR) or channel status information (CSI). The CSI may in turn be an aperiodic-CSI or low latency-CSI and e.g. comprise a channel quality indicator (CQI) report. The signal associated with the PUSCH may further e.g. be a layer 3 measurement report. The signal associated with the PUCCH may further e.g. be a scheduling request (SR). The type of uplink signal transmitted by the client device 100 in step 610 may e.g. be pre-defined by a standard, signalled by the network access node 300, or a combination of pre-defined and signalled. In case the network access node 300 signals information specifying the type of uplink signal to be used by the client device 100, this information may e.g. be comprised in the control message 510, as described above with reference to step 602.
Furthermore, the client device 100 may transmit the uplink signal 520 in a time-frequency resources indicated by the network access node 300. The time-frequency resources associated with the uplink signal 520 may in this case be indicated in the control message 520 received from the network access node 300, as described above with reference to step 602.
When the network access node 300 receives the uplink signal 520, the network access node 300 may perform timing advance control based on the received uplink signal 520, as will now be described with reference to Fig. 7.
Fig. 7 shows signaling between the network access node 300 and the client device 100 according to an embodiment. In step I in Fig. 7, the network access node 300 obtains a value for an uplink in-activity timer for a client device 100. The network access node 300 may obtain the value for the uplink in-activity timer based on one or more factors associated with e.g. radio environment, services configured for the client device 100, and load in the network and/or in the network access node 300. Thus, the network access node 300 may in embodiments obtain the uplink in-activity timer based on radio environment factors such as e.g. cell layout, i.e. based on how large movements the client device 100 can be expected to perform within a cell. For example, in a large (macro) cell a lower value may be configured for the uplink in-activity timer compared to in a small (pico) cell. The network access node 300 may further obtain the value for the uplink in-activity timer based on services configured for the client device 100. For example, in an URLLC scenario a lower value (e.g. 500 ms) may be configured for the uplink in-activity timer compared to in an enhanced mobile broadband (eMBB) scenario where a higher value (e.g. 2 s) may be configured for the uplink in-activity timer.
The network access node 300 transmits a control message 510 indicating the obtained value of the uplink in-activity timer to the client device 100, as shown in step II in Fig. 7. As previously described with reference to step 602 in Fig. 6, the control message 510 may further comprise additional information, such as e.g. information indicating time-frequency resources associated with an uplink signal 520.
In response to the transmission of the control message 510 to the client device 100, the network access node 300 may receive at least one uplink signal 520 from the client device 100. In the embodiment shown in Fig. 7, the client device 100 transmits one uplink signal 520, as shown in step III in Fig. 7. However, in embodiments the client device 100 may transmit more than one uplink signal 520. For example, the control message 510 may order the client device 100 to transmit a data packet, e.g. a measurement report. In this case, the client device 100 may need to first transmit an uplink signal 520 comprising a buffer status report, and then transmit the actual data packet, i.e. another uplink signal 520, when the network access node 300 has allocated resources for the data packet. Hence, multiple uplink signals 520 are transmitted in this case.
The client device 100 uses the uplink in-activity timer received in the control message 510 in step II in Fig. 7 as described above with reference to Fig. 6. Hence, the uplink signal 520 in step III in Fig. 7 may e.g. be transmitted by the client device 100 upon expiry of the uplink in activity timer. The client device 100 transmits the uplink signal 520 with the current timing advance, i.e. based on the latest timing advance value received from the network access node 300.
When the network access node 300 receives uplink signal 520 from the client device 100, the network access node 300 determines in step IV in Fig. 7 a timing advance based on the received uplink signal 520 and a timing advance value 530 based on the determined timing advance. In step V in Fig. 7, the network access node 300 transmits the determined timing advance value 530 to the client device 100. The timing advance and the timing advance value 530 may be determined based on conventional methods. Furthermore, the timing advance value 530 may e.g. be transmitted in a timing advance command known in the art.
The client device 100 receives the timing advance value 530 from the network access node 300. The timing advance value 530 is received in response to the transmission of the uplink signal 520 to the network access node 300. Based on the received timing advance value 530, the client device 100 time adjust uplink transmissions to the network access node 300. Thus, the next time the client device 100 has an uplink transmission to the network access node 300, the uplink transmission will be transmitted based on the timing advance value 530 (not shown in Fig. 7) received from the network access node 300 which means that the uplink time- synchronization is adapted to the timing advance value 530.
The client device 100 herein, may be denoted as a user device, a User Equipment (UE), a mobile station, an internet of things (loT) device, a sensor device, a wireless terminal and/or a mobile terminal, is enabled to communicate wirelessly in a wireless communication system, sometimes also referred to as a cellular radio system. The UEs may further be referred to as mobile telephones, cellular telephones, computer tablets or laptops with wireless capability. The UEs in this context may be, for example, portable, pocket-storable, hand-held, computer- comprised, or vehicle-mounted mobile devices, 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 802.1 1 -conformant Media Access Control (MAC) and Physical Layer (PHY) interface to the Wireless Medium (WM). 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 New Radio.
The network access node 300 herein may also be denoted as a radio client device, an access client device, an access point, or a base station, e.g. a Radio Base Station (RBS), 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 client devices 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 client device can be a Station (STA), which is any device that contains an IEEE 802.1 1 -conformant Media Access Control (MAC) and Physical Layer (PHY) interface to the Wireless Medium (WM). The radio client device may also be a base station corresponding to the fifth generation (5G) wireless systems. Furthermore, 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.
Moreover, it is realized by the skilled person that embodiments of the client device 100 and the network access node 300 comprises the necessary communication capabilities in the form of e.g., functions, means, units, elements, etc., for performing the solution. 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.
Especially, the processor(s) of the client device 100 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. 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.
Finally, it should be understood that the invention is not limited to the embodiments described above, but also relates to and incorporates all embodiments within the scope of the appended independent claims.

Claims

1 . A client device (100) for a wireless communication system (500), the client device (100) being configured to
receive a control message (510) from a network access node (300), wherein the control message (510) indicates a value for an uplink in-activity timer;
start the uplink in-activity timer based on an event associated with an uplink transmission to the network access node (300);
transmit at least one uplink signal (520) to the network access node (300) based on the uplink in-activity timer.
2. The client device (100) according to claim 1 , configured to
transmit the uplink signal (520) to the network access node (300) upon expiry of the uplink in-activity timer.
3. The client device (100) according to claim 2, configured to
transmit the uplink signal (520) to the network access node (300) prior to expiry of the uplink in-activity timer with a time threshold value.
4. The client device (100) according to any of the preceding claims, wherein the control message (510) indicates time-frequency resources associated with the uplink signal (520), and configured to
transmit the uplink signal (520) in the indicated time-frequency resources to the network access node (300).
5. The client device (100) according to any of the preceding claims, wherein the uplink in activity timer is a time alignment timer.
6. The client device (100) according to any of the preceding claims, wherein the event is an uplink transmission to the network access node (300).
7. The client device (100) according to any of the preceding claims, wherein the event is a reception of downlink control information associated with an uplink transmission to the network access node (300).
8. The client device (100) according to any of the preceding claims, wherein the uplink signal (520) is any of a signal associated with a physical uplink shared channel,
a signal associated with a physical uplink control channel, and
a sounding reference signal.
9. The client device (100) according to any of the preceding claims, configured to
receive a timing advance value from the network access node (300) in response to the transmission of the uplink signal (520) to the network access node (300);
time adjust uplink transmissions to the network access node (300) based on the received timing advance value.
10. The client device (100) according to any of the preceding claims, wherein the uplink is configured for services having at least one of a latency constraint and a reliability constraint.
1 1 . The client device (100) according to claim 10, wherein at least one of the latency constraint and the reliability constraint is associated with at least one of: a quality of service flow identity, a network slice selection assistance information configuration, a radio resource control parameter, and a medium access control parameter.
12. A network access node (300) for a wireless communication system (500), the network access node (300) being configured to
obtain a value for an uplink in-activity timer for a client device (100);
transmit a control message (510) to the client device (100), wherein the control message (510) indicates the value of the uplink in-activity timer.
13. The network access node (300) according to claim 12, configured to
receive at least one uplink signal (520) from the client device (100) in response to the transmission of the control message (510) to the client device (100);
determine a timing advance based on the received uplink signal (520);
determine a timing advance value (530) based on the determined timing advance; transmit the timing advance value (530) to the client device (100).
14. The network access node (300) according to claim 12 or 13, wherein the control message (510) indicates time-frequency resources associated with the uplink signal (520).
15. A method (200) for a client device (100), the method (200) comprises
receiving (202) a control message (510) from a network access node (300), wherein the control message (510) indicates a value for an uplink in-activity timer; starting (204) the uplink in-activity timer based on an event associated with an uplink transmission to the network access node (300);
transmitting (206) at least one uplink signal (520) to the network access node (300) based on the uplink in-activity timer.
16. A method (400) for a network access node (300), the method (400) comprises
obtaining (402) a value for an uplink in-activity timer for a client device (100);
transmitting (404) a control message (510) to the client device (100), wherein the control message (510) indicates the value of the uplink in-activity timer.
17. A computer program with a program code for performing a method according to claim 15 or 16 when the computer program runs on a computer.
PCT/EP2018/061654 2018-05-07 2018-05-07 Client device and network access node for maintaining uplink time-syncronization WO2019214796A1 (en)

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