METHOD, DEVICE AND COMPUTER READABLE MEDIUM FOR COMMUNICATIONS

Embodiments of the present disclosure relate to methods, devices and computer readable media for communications. A method for communications implemented by a terminal device comprises in response to receiving, at a terminal device from a network device, a message indicating that the terminal device is to enter an inactive state, entering the inactive state. The message comprises a resource configuration for data transmission between the terminal device and the network device. The method further comprises performing the data transmission based on the resource configuration.

TECHNICAL FIELD

Embodiments of the present disclosure generally relate to the field of telecommunication, and in particular, to methods, devices and computer readable media for data transmission in an inactive state.

BACKGROUND

Typically, a terminal device in an inactive state may still have small and infrequent data traffic to be transmitted. Until the third generation partnership project (3GPP) Release 16, the inactive state cannot support data transmission, and the terminal device has to resume the connection for any downlink and uplink data transmission. Connection setup and subsequently release to the inactive state happens for each data transmission whatever small and infrequent the data packets are. This will result in unnecessary power consumption and signaling overhead.

In this event, 3GPP Release 17 has approved the small and infrequent data traffic based on a random access channel (RACH) and pre-configured physical uplink shared channel (PUSCH) resources in the inactive state. Thus, how to perform transmission of the small and infrequent data traffic has become a hot issue.

SUMMARY

In general, embodiments of the present disclosure provide methods, devices and computer readable media for data transmission in an inactive state.

In a first aspect, there is provided a method for communications. The method comprises in response to receiving, at a terminal device from a network device, a message indicating that the terminal device is to enter an inactive state, entering the inactive state. The message comprises a resource configuration for data transmission between the terminal device and the network device. The method further comprises performing the data transmission based on the resource configuration.

In a second aspect, there is provided a method for communications. The method comprises transmitting, from a network device to a terminal device, a message indicating that the terminal device is to enter an inactive state. The message comprises a resource configuration for data transmission between the terminal device and the network device. The method further comprises performing the data transmission based on the resource configuration.

In a third aspect, there is provided a terminal device. The terminal device comprises a processor and a memory coupled to the processor. The memory stores instructions that when executed by the processor, cause the terminal device to perform the method according to the first aspect of the present disclosure.

In a fourth aspect, there is provided a network device. The network device comprises a processor and a memory coupled to the processor. The memory stores instructions that when executed by the processor, cause the network device to perform the method according to the second aspect of the present disclosure.

In a fifth aspect, there is provided a computer readable medium having instructions stored thereon. The instructions, when executed on at least one processor, cause the at least one processor to perform the method according to the first aspect of the present disclosure.

In a sixth aspect, there is provided a computer readable medium having instructions stored thereon. The instructions, when executed on at least one processor, cause the at least one processor to perform the method according to the second aspect of the present disclosure.

Other features of the present disclosure will become easily comprehensible through the following description.

DETAILED DESCRIPTION

As used herein, the term “terminal device” refers to any device having wireless or wired communication capabilities. Examples of the terminal device include, but not limited to, user equipment (UE), personal computers, desktops, mobile phones, cellular phones, smart phones, personal digital assistants (PDAs), portable computers, tablets, wearable devices, internet of things (IoT) devices, Internet of Everything (IoE) devices, machine type communication (MTC) devices, device on vehicle for V2X communication where X means pedestrian, vehicle, or infrastructure/network, or image capture devices such as digital cameras, gaming devices, music storage and playback appliances, or Internet appliances enabling wireless or wired Internet access and browsing and the like. The term “terminal device” can be used interchangeably with a UE, a mobile station, a subscriber station, a mobile terminal, a user terminal or a wireless device. In addition, the term “network device” refers to a device which is capable of providing or hosting a cell or coverage where terminal devices can communicate. Examples of a network device include, but not limited to, a Node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), a next generation NodeB (gNB), a transmission reception point (TRP), a remote radio unit (RRU), a radio head (RH), a remote radio head (RRH), a low power node such as a femto node, a pico node, and the like.

In one embodiment, the terminal device may be connected with a first network device and a second network device. One of the first network device and the second network device may be a master node and the other one may be a secondary node. The first network device and the second network device may use different RATs. In one embodiment, the first network device may be a first RAT device and the second network device may be a second RAT device. In one embodiment, the first RAT device is eNB and the second RAT device is gNB. Information related with different RATs may be transmitted to the terminal device from at least one of the first network device and the second network device. In one embodiment, first information may be transmitted to the terminal device from the first network device and second information may be transmitted to the terminal device from the second network device directly or via the first network device. In one embodiment, information related with configuration for the terminal device configured by the second network device may be transmitted from the second network device via the first network device. Information related with reconfiguration for the terminal device configured by the second network device may be transmitted to the terminal device from the second network device directly or via the first network device.

As used herein, the singular forms ‘a’, ‘an’ and ‘the’ are intended to include the plural forms as well, unless the context clearly indicates otherwise. The term ‘includes’ and its variants are to be read as open terms that mean ‘includes, but is not limited to.’ The term ‘based on’ is to be read as ‘at least in part based on.’ The term ‘one embodiment’ and ‘an embodiment’ are to be read as ‘at least one embodiment.’ The term ‘another embodiment’ is to be read as ‘at least one other embodiment.’ The terms ‘first,’ and the like may refer to different or same objects. Other definitions, explicit and implicit, may be included below.

In some examples, values, procedures, or apparatus are referred to as ‘best,’ ‘lowest,’ ‘highest,’ ‘minimum,’ ‘maximum,’ or the like. It will be appreciated that such descriptions are intended to indicate that a selection among many used functional alternatives can be made, and such selections need not be better, smaller, higher, or otherwise preferable to other selections.

FIG.1illustrates a schematic diagram of an example communication network100in which embodiments of the present disclosure can be implemented. As shown inFIG.1, the communication network100may include a network device110and a terminal device120served by the network device110. The network device110and the terminal device120may communicate with each other via a channel such as a wireless communication channel. For example, the terminal device120may transmit uplink data to the network device110, and the network device110may transmit a response to reception of the uplink data to the terminal device120.

It is to be understood that the number and type of devices inFIG.1are given for the purpose of illustration without suggesting any limitations to the present disclosure. The communication network100may include any suitable number of network devices and/or terminal devices adapted for implementing implementations of the present disclosure. Further, the communication network100may include any other devices than the network devices and the terminal devices, such as a core network element, but they are omitted here so as to avoid obscuring the present invention.

The communications in the communication network100may conform to any suitable standards including, but not limited to, Global System for Mobile Communications (GSM), Long Term Evolution (LTE), LTE-Evolution, LTE-Advanced (LTE-A), Wideband Code Division Multiple Access (WCDMA), Code Division Multiple Access (CDMA), GSM EDGE Radio Access Network (GERAN), Machine Type Communication (MTC) and the like. Furthermore, the communications may be performed according to any generation communication protocols either currently known or to be developed in the future. Examples of the communication protocols include, but not limited to, the first generation (1G), the second generation (2G), 2.5G, 2.75G, the third generation (3G), the fourth generation (4G), 4.5G, the fifth generation (5G) communication protocols.

As mentioned above, the terminal device120in an inactive state may still have small and infrequent data traffic to be transmitted. This kind of data transmission is also referred to as small data transmission (SDT) hereinafter. In some embodiments, the small and infrequent data traffic may include smartphone applications such as traffic from instant messaging (IM) services (whatsapp, QQ, wechat etc.), heart-beat/keep-alive traffic from IM/email clients and other applications, and push notifications from various applications. In some embodiments, the small and infrequent data traffic may include non-smartphone applications such as traffic from wearables (periodic positioning information etc.), sensors (Industrial Wireless Sensor Networks transmitting temperature, pressure readings periodically or in an event triggered manner etc.), and smart meters and smart meter networks sending periodic meter readings.

Currently, a RACH-based scheme and transmission on pre-configured PUSCH have been approved to perform SDT in an inactive of a terminal device. However, no further detailed solutions on general procedure for SDT are proposed. Embodiments of the present disclosure provide a solution for SDT. With the solution in accordance with embodiments of the present disclosure, SDT is achieved. Principles and implementations of the present disclosure will be described in detail below with reference to the figures.

FIG.2illustrates an example signaling chart showing an example process200for data transmission in an inactive state in accordance with some embodiments of the present disclosure. For the purpose of discussion, the process200will be described with reference toFIG.1. The process200may involve the terminal device120and the network device110as illustrated inFIG.1.

If the terminal device120receives210a message from the network device110, the terminal device120enters220the inactive state. The message indicates that the terminal device120is to enter an inactive state. The message comprises a resource configuration for data transmission between the terminal device120and the network device110.

In the inactive state, the terminal device120performs the data transmission based on the resource configuration. In some embodiments, upon entering the inactive state, the terminal device120transmits230uplink data to the network device110based on the resource configuration. In some embodiments, upon entering the inactive state, the terminal device120may receive240downlink data from the network device110based on the resource configuration.

In accordance with embodiments of the present disclosure, a general procedure for data transmission in the inactive state is provided.

In some embodiments, before receiving the message, the terminal device120is in a connected state. In such embodiments, upon receiving the message, the terminal device120transitions from the connected state to the inactive state.

In some embodiments, the message may comprise a Radio Resource Control (RRC) Release message. Of course, other messages than the RRC Release message may be applied. The scope of the present disclosure is not limited thereto.

In some embodiments, the message may further comprise a suspend configuration for the inactive state.

In some embodiments, the suspend configuration may comprise at least one of the following: a full Inactive-Radio Network Temporary Identifier (I-RNTI) of the terminal device120, a short I-RNTI of the terminal device120, a Paging Cycle, RAN-Notification Area Information, a Periodic RNAU-Timer Value, or a Next Hop Chaining Count.

Conventionally, upon receiving the message with the suspend configuration, UE performs the following actions: applying the received suspend configuration; removing all the entries within VarConditionalConfig (if any); resetting medium access control (MAC) and releasing the default MAC Cell Group configuration (if any); re-establishing radio link control (RLC) entities for signalling radio bearer 1 (SRB1); suspending all SRB(s) and data radio bearer(s) (DRB(s)), except SRB0; indicating packet data convergence protocol (PDCP) suspend to lower layers of all DRBs; indicating the suspension of the RRC connection to upper layers; entering RRC_INACTIVE and perform cell selection as specified in TS 38.304.

However, when receiving the RRC Release message with the suspend configuration, the reset of MAC will lead to timing advance (TA) invalid, which lead to subsequent SDT is not able to be performed. Thus, if the RRC Release message with the suspend configuration includes the resource configuration for the data transmission, the procedure should be different from conventional one.

In this regard, in some embodiments, upon receiving the message comprising the suspend configuration and the resource configuration for the data transmission, the terminal device120maintains a state of a MAC entity at the terminal device120. In other words, the terminal device120does not reset the MAC entity.

In some embodiments, upon receiving the message comprising the suspend configuration and the resource configuration for the data transmission, the terminal device120maintains DRBs for the data transmission. In other words, the terminal device120does not suspend the DRBs for the data transmission.

In some embodiments, upon receiving the message comprising the suspend configuration and the resource configuration for the data transmission, the terminal device120maintains a state of a PDCP entity at the terminal device120. In other words, the terminal device120does not suspend the PDCP entity.

In some embodiments, upon receiving the message comprising the suspend configuration and the resource configuration for the data transmission, the terminal device120suspends all SRB(s), except SRB0.

In some embodiments, the message from the network device110further comprises a configuration for an active bandwidth part (BWP) other than an initial BWP for the terminal device120. In such embodiments, the terminal device120may perform the data transmission on the active BWP other than the initial BWP.

FIG.3illustrates an example signaling chart showing an example process300for data transmission in an inactive state in accordance with other embodiments of the present disclosure. For the purpose of discussion, the process300will be described with reference toFIG.1. The process300may involve the terminal device120and the network device110as illustrated inFIG.1. The process300may relate to SDT based on RACH scheme and subsequent SDT.

The terminal device120in the inactive state transmits310a random access preamble to the network device110. Upon receiving the random access preamble, the network device110transmits320a random access response to the terminal device120.

The terminal device120transmits330a request for maintaining in the inactive state to the network device110. In some embodiments, the terminal device120transmits the request and uplink data together to the network device110.

In some embodiments, the request may comprise an RRC Resume Request or RRC Resume Request 1.

The network device110transmits340a message to the terminal device120. The message indicates that the terminal device120is to enter an inactive state. The message comprises a resource configuration for data transmission. Different from the message transmitted at210in the process200, the message transmitted at340may be transmitted with downlink data.

Similar to the process200, if the terminal device120receives the message, the terminal device120enters220the inactive state. In the inactive state, the terminal device120transmits230uplink data to the network device110based on the resource configuration. In some embodiments, upon entering the inactive state, the terminal device120receives240downlink data from the network device110based on the resource configuration.

It should be understood that although the process300has been described by taking four-step random access procedure, the process300is also applied to two-step random access procedure.

Conventionally, radio link monitoring and radio link failure (RLF) detection are only supported for a terminal device in a connected state.

In the connected state, the terminal device performs Radio Link Monitoring (RLM) in the active BWP based on reference signals and signal quality thresholds configured by the network device. The reference signals may comprise at least one of Synchronization Signal Block (SSB) or channel state information reference signal (CSI-RS). SSB-based RLM is based on the SSB associated to the initial DL BWP and can only be configured for the initial DL BWP and for DL BWPs containing the SSB associated to the initial DL BWP.

For other DL BWPs, RLM can only be performed based on CSI-RS. In case of DAPS handover, the terminal device continues the RLM at the source cell until the successful completion of the random access procedure to the target cell.

The terminal device declares Radio Link Failure (RLF) when one of the following criteria are met: expiry of a radio problem timer started after indication of radio problems from the physical layer (if radio problems are recovered before the timer is expired, the terminal device stops the timer); or expiry of a timer started upon triggering a measurement report for a measurement identity for which the timer has been configured while another radio problem timer is running; or Random access procedure failure; or RLC failure; or Random access procedure failure; or after detection of consistent uplink listen before talk (LBT) failures for operation with shared spectrum channel access.

Conventionally, after RLF is declared, the terminal device may perform at least one of the following: staying in the connected state; selecting a suitable cell and then initiating RRC re-establishment; entering an idle state if a suitable cell was not found within a certain time after RLF was declared.

During the SDT in the inactive state, there may be gap between coverage for cell reselection and coverage for data transmission, which means the radio signal has become too weak to transmit data successfully, but cell reselection still does not happen yet. If the terminal device still keeps SDT, significant delay would be introduced. Thus,

In order to solve the above problem, RLF related handling for the terminal device performing SDT in the inactive state is proposed.

In some embodiments, the terminal device120detects an RLF during the data transmission in the inactive state.

In some embodiments, the terminal device120detects the RLF and declares the RLF when one of the following criteria are met: expiry of a radio problem timer started after indication of radio problems from the physical layer (upon T310 expiry in PSCell); or RLC failure (i.e., the maximum number of retransmissions has been reached); or Random access procedure failure; or consistent LBT failure.

In some embodiments, the terminal device120detects the radio problems by performing RLM in the active BWP based on reference signals (such as SSB or CSI-RS) and signal quality thresholds configured by the network device110.

In some embodiments, upon detecting the RLF, the terminal device120mitigates the RLF by initiating a connection resumption procedure to the network device110.

In some embodiments, in order to initiate the connection resumption procedure, the terminal device120transmits to the network device110a request for resuming a first RRC connection between the terminal device120and the network device110. In some embodiments, the terminal device120transmits to the network device110the request without uplink data.

In some embodiments, upon detecting the RLF, the terminal device120mitigates the RLF by resetting MAC entity.

In some embodiments, upon detecting the RLF, the terminal device120mitigates the RLF by suspending all DRBs.

In some embodiments, upon detecting the RLF, the terminal device120mitigates the RLF by entering an idle state.

In some embodiments, the terminal device120enters the idle state by releasing the resource configuration received from the network device110.

In accordance with some embodiments of the present disclosure, with radio link monitoring and RLF detection during the data transmission, the radio link problem can be detected when performing SDT in the inactive state, the terminal device can perform procedure to avoid service interruption.

Currently, when a terminal device going to an RRC idle state, three types of release causes can be provided to the upper layer, i.e. “other”, “RRC Connection failure” and “RRC Resume failure”. However, all these three release causes are not suitable for SDT failure.

In some embodiments, upon entering the idle state, the terminal device120provides an indication to a non-access stratum (NAS). The indication indicates a failure of the data transmission in the inactive state. Hereinafter, the indication is also referred to as a release cause. The failure of the data transmission is also referred to as SDT failure.

In some embodiments, if a timer T319 expires or upon receiving Integrity check failure indication from lower layers while the timer T319 is running, and if the RRC Resume procedure is initiated for SDT, the terminal device120performs the actions upon entering the idle state, with release cause which indicates “SDT failure”.

Table 1 shows details about the timer T319.

In some embodiments, if cell reselection occurs while the timer T319 or a timer T302 is running, and if the RRC Resume procedure is initiated for SDT, the terminal device120performs the actions upon entering the idle state, with release cause which indicates “SDT failure”.

Table 2 shows details about the timer T302.

In some embodiments, upon detecting the RLF during subsequent SDT or configured grant SDT, the terminal device120performs the actions upon entering the idle state, with release cause which indicates “SDT failure”.

In accordance with some embodiments of the present disclosure, with the release cause which indicates “SDT failure” being provided to the NAS, the NAS layer can transfer form Connection Management (CM)-Connectedstate to CM-Idle state, with the reason of the state transition.

FIG.4illustrates an example method400for communications implemented at a terminal device in accordance with some embodiments of the present disclosure. For example, the method400may be performed at the terminal device120as shown inFIG.1. For the purpose of discussion, in the following, the method400will be described with reference toFIG.1. It is to be understood that the method400may include additional blocks not shown and/or may omit some blocks as shown, and the scope of the present disclosure is not limited in this regard.

At block410, if the terminal device120receives from the network device110a message indicating that the terminal device120is to enter an inactive state, the terminal device120enters the inactive state. The message comprises a resource configuration for data transmission between the terminal device and the network device.

At block420, the terminal device120performs the data transmission based on the resource configuration.

In some embodiments, the terminal device120is in a connected state before receiving the message, and entering the inactive state comprises transitioning from the connected state to the inactive state.

In some embodiments, a state of a medium access control entity at the terminal device is maintained.

In some embodiments, data radio bearers for the data transmission are maintained.

In some embodiments, a state of a packet data convergence protocol entity at the terminal device is maintained.

In some embodiments, the message further comprises a configuration for an active bandwidth part other than an initial bandwidth part for the terminal device; and performing the data transmission comprises performing the data transmission on the active bandwidth part.

In some embodiments, the method400further comprises detecting a radio link failure during the data transmission in the inactive state.

In some embodiments, the method400further comprises in response to detecting the radio link failure, mitigating the radio link failure by initiating a connection resumption procedure to the network device.

In some embodiments, initiating the connection resumption procedure comprises: transmitting to the network device a request for resuming a first radio resource control connection between the terminal device and the network device.

In some embodiments, transmitting the request comprises transmitting the request without the uplink data.

In some embodiments, the method400further comprises in response to detecting the radio link failure, mitigating the radio link failure by entering an idle state.

In some embodiments, the method400further comprises entering an idle state in response to at least one of the following: an expiry of a timer T319, receiving an integrity check failure indication from lower layers while the timer T319 is running, or cell reselection occurring while the timer T319 or a timer T302 is running.

In some embodiments, entering the idle state comprises releasing the resource configuration.

In some embodiments, the method400further comprises providing to a non-access stratum an indication indicating a failure of the data transmission in the inactive state.

FIG.5illustrates an example method500for communications implemented at a network device in accordance with some embodiments of the present disclosure. For example, the method500may be performed at the network device110as shown inFIG.1. For the purpose of discussion, in the following, the method500will be described with reference toFIG.1. It is to be understood that the method500may include additional blocks not shown and/or may omit some blocks as shown, and the scope of the present disclosure is not limited in this regard.

At block510, the network device110transmits to the terminal device120a message indicating that the terminal device is to enter an inactive state. The message comprises a resource configuration for data transmission between the terminal device and the network device.

At block520, the network device110performs the data transmission based on the resource configuration.

In some embodiments, the message further comprises a configuration for an active bandwidth part other than an initial bandwidth part for the terminal device; and performing the data transmission comprises performing the data transmission on the active bandwidth part.

In some embodiments, the method500further comprises: in response to a radio link failure during the data transmission in the inactive state, receiving, from the terminal device, a request for resuming a first radio resource control connection between the terminal device and the network device.

In some embodiments, receiving the request comprises receiving the request without uplink data.

FIG.6is a simplified block diagram of a device600that is suitable for implementing embodiments of the present disclosure. The device600can be considered as a further example implementation of the network device110or the terminal device120as shown inFIG.1. Accordingly, the device600can be implemented at or as at least a part of the network device110or the terminal device120.

As shown, the device600includes a processor610, a memory620coupled to the processor610, a suitable transmitter (TX) and receiver (RX)640coupled to the processor610, and a communication interface coupled to the TX/RX640. The memory620stores at least a part of a program630. The TX/RX640is for bidirectional communications. The TX/RX640has at least one antenna to facilitate communication, though in practice an Access Node mentioned in this application may have several ones. The communication interface may represent any interface that is necessary for communication with other network elements, such as X2/Xn interface for bidirectional communications between eNBs/gNBs, S1/NG interface for communication between a Mobility Management Entity (MME)/Access and Mobility Management Function (AMF)/SGW/UPF and the eNB/gNB, Un interface for communication between the eNB/gNB and a relay node (RN), or Uu interface for communication between the eNB/gNB and a terminal device.

The program630is assumed to include program instructions that, when executed by the associated processor610, enable the device600to operate in accordance with the embodiments of the present disclosure, as discussed herein with reference toFIGS.1to5. The embodiments herein may be implemented by computer software executable by the processor610of the device600, or by hardware, or by a combination of software and hardware. The processor610may be configured to implement various embodiments of the present disclosure. Furthermore, a combination of the processor610and memory620may form processing means650adapted to implement various embodiments of the present disclosure.

The memory620may be of any type suitable to the local technical network and may be implemented using any suitable data storage technology, such as a non-transitory computer readable storage medium, semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory, as non-limiting examples. While only one memory620is shown in the device600, there may be several physically distinct memory modules in the device600. The processor610may be of any type suitable to the local technical network, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device600may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.