GB2574016A

GB2574016A - Apparatus, method and computer program

Info

Publication number: GB2574016A
Application number: GB1808385.7A
Authority: GB
Inventors: Koskinen Jussi-Pekka; Turtinen Samuli
Original assignee: Nokia Technologies Oy
Current assignee: Nokia Technologies Oy
Priority date: 2018-05-22
Filing date: 2018-05-22
Publication date: 2019-11-27
Also published as: GB201808385D0

Abstract

Receiving, at a user equipment, an indication of a resource grant for a radio resource control (RRC) request and determining, in response to an event when the user equipment is in a RRC inactive state, whether to send the RRC request to move to a RRC connected state or move to a RRC idle state in dependence on said indication. The determining may comprise determining if the size of a RRC resume request is greater than the RRC grant and, if so, moving to the RRC idle state and/or sending a RRC connection request. The event may comprise determining that data is available for transmission from the UE or selecting a new cell. The grant may be received in response to a random access preamble.

Description

Apparatus, method and computer program

Field

The present application relates to an apparatus, a method and computer program and in particular but not exclusively to radio resource control (RRC) connection procedures in a New Radio communication system.

Background

A communication system can be seen as a facility that enables communication sessions between two or more entities such as user terminals, base stations and/or other nodes byproviding carriers between the various entities involved in the communications path. A communication system can be provided for example by means of a communication network and one or more compatible communication devices. The communication sessions may comprise, for example, communication of date for carrying communications such as voice, video, electronic mail (email), text message, multimedia and/or content data and so on. Nonlimiting examples of services provided comprise two-way or multi-way calls, data communication or multimedia services and access to a data network system, such as the Internet.

In a wireless communication system at least a part of a communication session between at least two stations occurs over a wireless link. Examples of wireless systems comprise public land mobile networks (PLMN), satellite based communication systems and different wireless local networks, for example wireless local area networks (WLAN). The wireless systems can typically be divided into cells, and are therefore often referred to as cellular systems.

A user can access the communication system by means of an appropriate communication device or terminal. A communication device of a user may be referred to as user equipment (UE) or user device. A communication device is provided with an appropriate signal receiving and transmitting apparatus for enabling communications, for example enabling access to a communication network or communications directly with other users. The communication device may access a carrier provided by a station, for example a base station of a cell, and transmit and/or receive communications on the carrier.

The communication system and associated devices typically operate in accordance with a given standard or specification which sets out what the various entities associated with the system are permitted to do and how that should be achieved. Communication protocols and/or parameters which shall be used for the connection are also typically defined. One example of a communications system is UTRAN (3G radio). Other examples of communication systems are the long-term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio-access technology and so-called 5G or New Radio (NR) networks. NR is being standardized by the 3rd Generation Partnership Project (3GPP).

Summary

In a first aspect there is provided an apparatus comprising means for receiving, at a user equipment, an indication of a resource grant for a radio resource control request and determining, in response to an event when the user equipment is in a radio resource control inactive stale, whether to send the radio resource control request to move to a radio resource control connected state or move to a radio resource control idle state in dependence on the indication.

The radio resource control request may comprise a first request having a first size or a second request having a second size.

The first request may comprise a radio resource control resume request. The second request may comprise a radio resource control connection request.

Means for determining whether to send the radio resource control request to move to a radio resource control connected state or move to radio resource control idle state may comprise means for determining if the size of the first request is greater than the radio resource grant and if so, moving to the radio resource control idle state.

Means for determining whether to send the radio resource control request to move to a radio resource control connected state or move to radio resource control idle state may comprise means for determining if the size of the first request is greater than the radio resource grant and, if so, sending the second request.

The event may comprise at least one of determining that data is available for transmission from the user equipment or selecting a new cell.

The apparatus may comprise means for sending a random access preamble to a network and receiving the indication of the resource grant in response to the random access preamble in a random access response.

The indication of the resource grant may be received in system information from a network.

In a second aspect there is provided a method comprising receiving, at a user equipment, an indication of a resource grant for a radio resource control request and determining, in response to an event when the user equipment is in a radio resource control inactive state, whether to send the radio resource control request to move to a radio resource control connected state or move to a radio resource control idle state in dependence on said indication.

Determining whether to send the radio resource control request to move to a radio resource control connected state or move to radio resource control idle state may comprise determining if the size of the first request is greater than the radio resource grant and if so, moving to the radio resource control idle state.

Determining whether to send the radio resource control request to move to a radio resource control connected state or move to radio resource control idle state may comprise determining if the size of the first request is greater than the radio resource grant and, if so, sending the second request.

The method may comprise sending a random access preamble to a network and receiving the indication of the resource grant in response to the random access preamble in the random access response.

in a third aspect there is provided an apparatus comprising at least one processor and at least one memory including a computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to receive, at a user equipment, an indication of a resource grant for a radio resource control request and determine, in response io an event when the user equipment is in a radio resource control inactive state, whether to send the radio resource control request to move to a radio resource control connected state or move to a radio resource control idle slate in dependence on said indication.

The apparatus may be configured to determine if the size of the first request is greater than the radio resource grant and if so, move to the radio resource control idle state.

The apparatus may be configured to determine if the size of the first request is greater than the radio resource grant and, if so, send the second request.

The apparatus may be configured to determine at least one of that data is available for transmission from the user equipment or selecting a new cell.

The apparatus may be configured to send a random access preamble to a network and receiving the indication of the resource grant in response to the random access preamble In a random access response.

in a fourth aspect there is provided a computer readable medium comprising program instructions for causing an apparatus to perform at least the following receive, at a user equipment, an indication of a resource grant for a radio resource control request and determine, in response to an event when the user equipment is in a radio resource control inactive state, whether to send the radio resource control request to move to a radio resource control connected state or move to a radio resource control idle state in dependence on said indication.

The apparatus may be caused to determine if the size of the first request is greater than the radio resource grant and if so, move to the radio resource control idle state.

The apparatus may be caused to determine if the size of the first request is greater than the radio resource grant and, if so, send the second request.

The apparatus may be caused to determine at least one of that data is available for transmission from the user equipment or selecting a new cell.

The apparatus may be caused to send a random access preamble to a network and receiving the indication of the resource grant in response to the random access preamble in a random access response.

In a fifth aspect there is provided a non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the following: receive, at a user equipment, an indication of a resource grant for a radio resource control request and determine, in response to an event when the user equipment is in a radio resource control inactive state, whether to send the radio resource control request to move to a radio resource control connected state or move to a radio resource control idle state in dependence on said indication.

The apparatus may be caused to determine if the size of the first request is greater than the radio resource grant and if so, move to the radio resource control idie state.

In a sixth aspect there is provided a method comprising receiving, at a user equipment, an indication of a resource grant for a radio resource control request and determining, in response to an event when the user equipment is in a radio resource control inactive state, to move to a radio resource control idle state in dependence on said indication.

Determining to move to a radio resource control idie state may comprise determining if the size of the radio resource control request is greater than the radio resource grant and if so, moving to the radio resource control idle state.

Determining to move a user equipment to a radio resource control idle state may comprises (re)selecting a new cell.

The indication of the resource grant may be received in system information from a network. The indication may comprise an absence of information about the resource grant.

In further embodiments there is provided an apparatus comprising means for performing the method of the sixth aspect, an apparatus configured to perform a method according to the sixth aspect and a computer readable medium and a non-transitory computer readable medium comprising program instructions for causing an apparatus to perform a method according to the sixth aspect.

In the above, many different embodiments have been described, it should be appreciated that further embodiments may be provided by the combination of any two or more of the embodiments described above.

Description of Figures

Embodiments wiii now be described, by way of example only, with reference to the accompanying Figures in which:

Figure 1 shows a schematic diagram of an example communication system comprising a base station and a plurality of communication devices;

Figure 2 shows a schematic diagram of an example mobile communication device:

Figure 3 shows a schematic diagram of an example control apparatus;

Figure 4 shows a schematic representation of example RRC states in a communication system;

Figure 5 shows a flow diagram of a method according to an embodiment;

Figure 6 shows an example signalling flow according to an embodiment;

Figure 7 shows an example signalling flow according to an embodiment;

Figure 8 shows an example signalling flow according to an embodiment;

Figure 9 shows an example signalling flow according to an embodiment.

Detailed description

Before explaining in detail the examples, certain general principles of a wireless communication system and mobile communication devices are briefly explained with reference to Figures 1 to 3 to assist in understanding the technology underlying the described examples.

In a wireless communication system 100, such as that shown in figure 1, mobile communication devices or user equipment (UE) 102, 104, 105 are provided wireless access via at least one base station or similar wireless transmitting and/or receiving node or point. Base stations are typically controlled by at least one appropriate controller apparatus, so as to enable operation thereof and management of mobile communication devices in communication with the base stations. The controller apparatus may be located in a radio 10 access network (e.g. wireless communication system 100) or in a core network (CN) (not shown) and may be implemented as one central apparatus or its functionality may be distributed over several apparatus. The controlier apparatus may be part of the base station and/or provided by a separate entity such as a Radio Network Controller, in Figure 1 control apparatus 108 and 109 are shown to control the respective macro level base stations 106 and 15 107. The control apparatus of a base station can be interconnected with other control entities.

The control apparatus is typically provided with memory capacity and at. least one data processor. The control apparatus and functions may be distributed between a plurality of control units. In some systems, the control apparatus may additionally or alternatively be provided in a radio network controller.

In Figure 1 base stations 106 and 107 are shown as connected to a wider communications network 113 via gateway 112. A further gateway function may be provided to connect to another network.

The smaller base stations 116, 118 and 120 may also be connected to the network 113, for example by a separate gateway function and/or via the controllers of the macro level stations. The base stations 116, 118 and 120 may be pico or femto level base stations or the like, in the example, stations 116 and 118 are connected via a gateway 111 whilst station 120 connects via the controlier apparatus 108. in some embodiments, the smaller stations may 30 not be provided. Smaller base stations 116, 118 and 120 may be part of a second network, for example WLAN and may be WLAN APs.

The communication devices 102, 104, 105 may access the communication system based on various access techniques, such as code division multiple access (CDMA), or wideband 35 CDMA (WCDMA). Other non-limiting examples comprise time division multiple access (TDMA), frequency division multiple access (FDMA) and various schemes thereof such as the interleaved frequency division multiple access (IFDMA), single carrier frequency division multiple access (SC-FDMA) and orthogonal frequency division multiple access (OFDMA), space division multiple access (SDMA) and so on.

An example of wireless communication systems are architectures standardized by the 3rd Generation Partnership Project (3GPP). A latest 3GPP based development is often referred to as the long term evolution (LIE) of the Universal Mobile Telecommunications System (UMTS) radio-access technology. The various development stages of the 3GPP specifications are referred to as releases. More recent developments of the LTE are often referred to as LTE Advanced (LTE-A). The LTE employs a mobile architecture known as the Evolved Universal Terrestrial Radio Access Network (E-UTRAN). Base stations of such systems are known as evolved or enhanced Node Bs (eNBs) and provide E-UTRAN features such as user plane Packet Data Convergence/Radio Link Control/Medium Access Control/Physical layer protocol (PDCP/RLC/MAC/PHY) and control plane Radio Resource Control (RRC) protocol terminations towards the communication devices. Other examples of radio access system comprise those provided by base stations of systems that are based on technologies such as wireless local area network (WLAN) and/or WiMax (Worldwide Interoperability for Microwave Access). A base station can provide coverage for an entire cell or similar radio service area.

An example of a suitable communications system is the 5G or NR concept. Network architecture in NR may be similar to that of LTE-advanced. Base stations of NR systems may be known as next generation Node Bs (gNBs). Changes to the network architecture may depend on the need to support various radio technologies and finer QoS support, and some on-demand requirements for e.g. QoS levels to support QoE of user point of view. Also network aware services and applications, and service and application aware networks may bring changes to the architecture. Those are related to information Centric Network (ICN) and User-Centric Content Delivery Network (UC-CDN) approaches. NR may use multiple input multiple output (ΜΙΜΟ) antennas, many more base stations or nodes than the LTE (a socalled small cell concept), including macro sites operating in co-operation with smaller stations and perhaps also employing a variety of radio technologies for better coverage and enhanced data rates.

Future networks may utilise network functions virtualization (NFV) which is a network architecture concept that proposes virtualizing network node functions into “building blocks or entities that may be operationally connected or linked together to provide services. A virtualized network function (VNF) may comprise one or more virtual machines running computer program codes using standard or general type servers instead of customized hardware. Cloud computing or data storage may also be utilized. In radio communications this may mean node operations to be carried out, at least partly, in a server, host or node operationally coupled to a remote radio head. It is also possible that node operations will be distributed among a plurality of servers, nodes or hosts. It should also be understood that the distribution of labour between core network operations and base station operations may differ from that of the LTE or even be non-existent.

A possible mobile communication device will now be described in more detail with reference to Figure 2 showing a schematic, partially sectioned view of a communication device 200. Such a communication device is often referred to as user equipment (UE) or terminal. An appropriate mobile communication device may be provided by any device capable of sending and receiving radio signals. Non-limiting examples comprise a mobile station (MS) or mobile device such as a mobile phone or what is known as a ’smart phone’, a computer provided with a wireless interface card or other wireless interface facility (e.g., USE dongle), personal data assistant (PDA) or a tablet provided with wireless communication capabilities, or any combinations of these or the like. A mobile communication device may provide, for example, communication of data for carrying communications such as voice, electronic mail (email), text message, multimedia and so on. Users may thus be offered and provided numerous services via their communication devices. Non-limiting examples of these services comprise two-way or multi-way calls, data communication or multimedia services or simply an access to a data communications network system, such as the Internet. Users may also be provided broadcast or multicast data. Non-limiting examples of the content comprise downloads, television and radio programs, videos, advertisements, various alerts and other information.

A mobile device is typically provided with at least one data processing entity 201, at least one memory 202 and other possible components 203 for use in software and hardware aided execution of tasks ft is designed to perform, including control of access to and communications with access systems and other communication devices. The data processing, storage and other relevant control apparatus can be provided on an appropriate circuit board and/or in chipsets. This feature is denoted by reference 204. The user may control the operation of the mobile device by means of a suitable user interface such as key pad 205, voice commands, touch sensitive screen or pad, combinations thereof or the like. A display 208, a speaker and a microphone can be also provided. Furthermore, a mobile communication device may comprise appropriate connectors (either wired or wireless) to other devices and/or for connecting external accessories, for example hands-free equipment, thereto.

The mobile device 200 may receive signals over an air or radio interface 207 via appropriate apparatus for receiving and may transmit signals via appropriate apparatus for transmitting radio signals, in Figure 2 transceiver apparatus is designated schematically by block 206. The transceiver apparatus 206 may be provided for example by means of a radio part and associated antenna arrangement. The antenna arrangement may be arranged internally or externally to the mobile device.

Figure 3 shows an example of a control apparatus for a communication system, for example to be coupled to and,for for controlling a station of an access system, such as a RAN node, e.g. a base station, eNB or gNB, a relay node or a node of a core network such as an MME (or access management function (AMF)) or S-GW, or a server or host. The method may be implanted in a single control apparatus or across more than one control apparatus. The control apparatus may be integrated with or external to a node or module of a core network or RAN. in some embodiments, base stations comprise a separate control apparatus unit or module. In other embodiments, the control apparatus can be another network element such as a radio network controller or a spectrum controller. In some embodiments, each base station may have such a control apparatus as well as a control apparatus being provided in a radio network controller. The control apparatus 300 can be arranged to provide control on communications in the service area of the system. The control apparatus 300 comprises at least one memory 301, at least one data processing unit 302, 303 and an input/output interface 304. Via the interface the control apparatus can be coupled to a receiver and a transmitter of the base station. The receiver and/or the transmitter may be implemented as a radio front end or a remote radio head.

Figure 4 shows an RRC state diagram for the 3GPP NR system. An RRC state, RRC inactive, has been introduced in 5G NR in addition to RRC connected and RRC idle states. When a UE is in RRC idle state, its context is maintained and/or managed by Core Network (CN), its context is maintained and/or managed by RAN.

RRC supports the following states which can be characterised as follows:

- RRCJDLE:

- PLMN selection;

- Broadcast of system information;

- Ceil re-selection mobility;

- Paging for mobile terminated data is initiated by 5GC;

- Paging for mobile terminated data area is managed by 5GC;

DRX for CN paging configured by NAS.

RRCJNACTIVE:

- PLMN selection;

- Broadcast of system information;

- Cell re-selection mobility;

- Paging is initiated by NG-RAN (RAN paging);

- RAN-based notification area (RNA) is managed by NG- RAN;

- DRX for RAN paging configured by NG-RAN;

- 5GC - NG-RAN connection (both C/U-pianes) is established for UE;

- The UE AS context is stored in NG-RAN and the UE;

- NG-RAN knows the RNA which the UE belongs to.

- RRC_CONNECTED:

- 5GC - NG-RAN connection (both C/U-pianes) is established for UE;

- The UE AS context is stored in NG-RAN and the UE;

- NG-RAN knows the cell which the UE belongs to;

- Transfer of unicast data to/from the UE;

- Network controlled mobility including measurements.

The three RRC states in NR may be referred to as NR-RRC CONNECTED, NR-RRC INACTIVE and NR-RRC IDLE.

When a UE is powered up it goes to idle mode after the UE has completed the cell selection process and has chosen a cell. A UE may move to the RRC connected state with connection establishment, re-establishment or resume procedure.

if there is no activity from the UE for a given time, the network may suspend (or inactive) the UE’s session by moving the UE to the RRC inactive state. The UE may resume a suspended session to move to RRC connected state.

A UE may also move to RRC idle state from RRC connected or RRC inactive state due to a connection failure or RRC release procedure or upon inactivity timer expiry.

When a UE is in the RRC inactive state, it utilizes a RRC Resume Request message to resume its RRC connection. When the UE is in the RRC idle state, it utilizes a RRC Request message to establish RRC connection. When the UE is in RRC connected state and declares Radio

Link Failure (RLF) or connection failure, it utilizes a RRC Re-establishment message to reestablish RRC connection.

The following is described with reference to a random access procedure for a user equipment (or terminal). A random access procedure maybe characterised by the following messages MSG1: random access preamble

MSG2: preamble response/random access response

MSG3: terminal identity etc./connection request sent to network

MSG4: contention resolution message sent to terminal

MSG3 messages are sent by a UE as part of a RACH procedure. Different MSG3 message sizes may be sent by the UE depending on which RRC message is included. At least three different RRC messages and message sizes for MSG3 are considered; RRC Reestablishment Request, RRC Resume Request, RRC Request. Each of these messages may be different in size. For example, a RRC Re-establishment Request may be 56/64 bits, a RRC Resume Request may be 72/80 bits and a RRC Request may be 56 bits. These sizes may be inclusive of MAC subheader used to identify the CCCH (Common Control Channel) logical channel where these RRC messages are transmitted.

Example sizes of these messages are provided in the below tables 1, 2 and 3 which illustrate a RRC connection request, a RRC connection resume request and a RRC connection reestablishment request, respectively. The sizes in the tables below have not been octet aligned.

Table 1: RRC Connection Request

\| RRCConnectionRequest
He	Size (bits)
; RRC Message I Structure	4
I ue-Identity	40
establishmentcause	4
i MAC Header L..................................................	8
i Spare	4
I Total	60

RRC connection resume request

IE	Size (bits)
.Message Structure	4

ue-identity	40
resumeCause	4
shortMac-l	16
Spare	4
MAC Header	8
Total	76

Table 2: RRC Connection Resume Request

RRC connection re-establishment request
IE	Size (bits)
Message Structure	4
ue-ldentiiy	25
reestablishmentCause	2
short Mac-!	16
MAC Header	8
Tota!	5S

Table 3: RRC Connection Re-establishment Request

A base station of a network provides a UE with a UL grant for MSG3. The grant should be large enough to accommodate the size of MSG3. However, a base station may not be aware of the type of message the UE is going to transmit in MSG3. A base station may not want to allocate large grants unnecessarily, e.g., in the case that resume procedure is (temporarily) not supported. For instance, a base station may be implemented without the RRC inactive mode functionality or a network operator may not intend to use the RRC inactive mode and resume procedure feature in a given area.

In LTE, the eNB allocates UL grant with size of 56 bits which is able to accommodate all different MSG3 types. The minimum grant size for MSG3 is given in the 3GPP TS 36.321.

In LTE, usage of a random access preamble group indicates whether the UE has large MSG3 available for transmission. An indicator, such as useFullResumelD, in system information maybe used to indicate if the UE shall indicate full resume ID of 40 bits in RRCConnectionResumeRequest which impacts the size of MSG3.

Figure 5 shews a flowchart of an example method according to an embodiment, in a first step, S1, the method comprises receiving, at a user equipment, an indication of a resource grant for a radio resource control request.

in a third step, S3, the method comprises determining, in response to an event when the user equipment is in a radio resource control inactive state whether to send the radio resource control request to move to a radio resource control connected state or move to a radio resource control idle state in dependence on said indication.

In an alternative embodiment, the third step may comprise, in response to an event, e.g. cell reselection, when the user equipment is in a radio resource control inactive state, determining to move to a radio resource control idle state in dependence on the indication.

The first request may be a radio resource control resume request, i.e., a request from a UE in an inactive state to resume RRC connection. The second request may be a radio resource control connection request, i.e . a request from a UEfor RRC connection (which may be known as RRC Request). The UE may move into the idle state before it sends the request for RRC connection or it may send the RRC connection request in the inactive state.

The indication of the resource grant may be received in a random access response in response to a random access preamble sent by the user equipment to a network.

The event may comprise determining that data is available for transmission from the user equipment and/or selecting a new cell and/or selecting a new RAN area ID which is not included in the current RAN tracking/notification area of the UE.

In one example, determining whether to send the radio resource control request to move to an RRC connected state or move to radio resource control idle state comprises determining if the size of the first request is greater than the radio resource grant and if so, moving to the radio resource control idle state. If not. the first request is sent to the network.

Figure 6 shows a signalling flow for a first embodiment in which a UE goes to IDLE from INACTIVE if the MSG3 UL grant provided in MSG2 is too small to accommodate the size of RRC Resume Request message.

The UE of Figure 6 is in inactive mode. UL data becomes available for transmission. The UE prepares a RRC Resume Request of 80 bits for transmission to the gNB. The UE sends a random access preamble to the gNB and receives a random access response from the gNB. The response comprises an UL grant of 56 bits. Since the UL grant is smaller than the RRC Resume Request, the UE goes to IDLE mode.

That is, if the common control channel (CCCH) service data unit (SDU) size in MAC cannot fit to the available MSG3 grant, the MAC indicates this event to RRC. Based on the indication, RRC may trigger the procedure for going to IDLE.

in one example, the method may comprise determining if the size of the first request is greater than the radio resource grant and, if so, sending the second request, e.g. a RRC connection request (RRC Request), to the network, if not, the first request, e.g. a RRC resume request is sent to the network.

Figure 7 shows a signalling flow for a second embodiment in which the UE sends a RRC Request instead of a RRC Resume Request if the UL grant is too small to accommodate the size of RRC Resume Request message.

The UE of Figure 7 is in inactive mode. UL data becomes available for transmission. The UE prepares a RRC Resume Request of 80 bits for transmission to the gNB. The UE sends a random access preamble to the gNB and receives a random access response from the gNB. The response comprises an UL grant of 56 bits. UL grant according to 2nd embodiment, is received in MSG2. The UE then sends a RRC Request message to the gNB and undergoes an RRC setup procedure. The UE is then in connected mode.

Figure 8 shows a signalling flow for a third embodiment in which the UE prepares more than one RRC message (e.g. RRC Request, RRC Resume Request, RRC Re-estab!ishment Request) for transmission. The UE transmits the RRC message based on the MSG3 UL grant provided in MSG2.

For example, RRC Resume Request is transmitted if UL grant is large enough i.e. able to accommodate the whole message, otherwise RRC Request may be transmitted.

The first request and second request may both be RRC resume request messages. In one option, two RRC Resume Request messages of different sizes may be prepared for which the other one equals with the RRC Request in terms of message size. In this case, the bigger RRC Resume Request is always prioritized but if the MSG3 UL grant size cannot accommodate it, UE multiplexes the smaller one. In this case, some information in the smaller RRC resume request message may be compromised compared to bigger RRC resume request, for instance, the UE ID used in the indication could be truncated. If the UE uses truncated UE ID, network node may need to request the UE context from multiple other network nodes, however, this is a choice for the network.

The indication of the resource grant may be received in system information from a network. For example, the indication may comprise of the maximum or minimum size of MSG3 the UE shall use. For another example, there may be separate indication for each supported MSG3 size the UE can use. In one implementation, if the UE does not receive the indication of the resource grant in system information for the bigger MSG3 size, it assumes that only the smaller MSG3 size is supported.

In one alternative, the indication of the resource grant may be received in system information from a network only when the bigger MSG3 sizes are supported. If the UE does not receive the indication of the resource grant in system information from a network, it goes to idle mode.

Figure 9 shows a signalling flow for a further embodiment, in which a UE goes to IDLE from INACTIVE if the network indicates that UL grant for MSG3 is smaller than the Resume Request size. The indication may be via dedicated and/or broadcast, signalling. If the UL grant is larger (or equal to) the Resune Request size, the UL may stay in RRC inactive state.

in Figure 9, the UE is in inactive mode. The UE selects a new cell and receives system information comprising an indication that the grant size for MSG3 is 60 bits. The UE goes to idle mode, in this example, the UE goes to the RRC idle state before attempting a connection procedure. That is the UE goes to idle immediately when reselecting to such a cell.

Embodiments as described above address how to establish connection with different RRC messages in MSG3. Embodiments may provide a clear procedure for how to handle different RRC message sending in MSG3.

The UE behavior is deterministic, in the embodiments described with respect to Figures 5 to 9, there is no need to broadcast grant size for MSG3.

The random access (and hence ceil) coverage may be increased at the expense of slightly more signaling exposed in connection establishment since the MSG3 grant size can be smaller, i.e., to accommodate only RRC messages of the smallest size.

All the NW nodes do not need to be prepared to handle RRC Resume Request messages/lnactive UEs. if a UL grant smaller than the RRC Resume Request is provided, a UE falls back to the RRC IDLE and RRC Connection establishment procedure. This scenario is valid, e.g., in the RAN tracking area borders where the UE attempts to update its RAN area location via RRC resume procedure. This updating is done after crossing the border of a RAN tracking area in which case the target network node/cel! may not be prepared to handle RRC Resume Request messages/inactive UEs. Or, for instance, in RAN sharing scenarios where multiple operators operate in the same node/cell, the UE ID used for the resume procedure may not be known to ail the operators.

In this case, if an RRC inactive UE receives a small UL grant in MSG2, the UE knows that it cannot send RRC Resume in MSG3. The UE may either fallback to RRC idle or send RRC Request in MSG3. Previously, when the largest UL grant was always allocated, the UE would send RRC Resume in MSG3 and get RRC Release (or similar) in MSG4. Embodiments may mitigate the need for MSG3 and MSG4 in moving the UE to IDLE mode. Embodiments may prevent avoidable RRC release.

The apparatus may comprise a control apparatus as described with reference to Figure 3. Control functions may comprise receiving, at a user equipment, an indication of a resource grant for a radio resource control request and determining, in response to an event when the user equipment is in a radio resource control inactive state, whether to send the radio resource control request to move to a radio resource control connected state or move to a radio resource control idle state in dependence on said indication.

it should be understood that the apparatuses may comprise or be coupled to other units or modules etc., such as radio parts or radio heads, used in or for transmission and/or reception. Although the apparatuses have been described as one entity, different modules and memory may be implemented in one or more physical or logical entities.

It is noted that whilst embodiments have been described in relation to RRC states in NR, similar principles can be applied in relation to other networks and communication systems where a UE moves between states. Therefore, although certain embodiments were described above by way of example with reference to certain example architectures for wireless networks, technologies and standards, embodiments may be applied to any other suitable forms of communication systems than those illustrated and described herein.

It is also noted herein that while the above describes example embodiments, there are several variations and modifications which may be made to the disclosed solution without departing from the scope of the present invention.

In general, the various embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects of the invention may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto. While various aspects of the invention may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

The embodiments of this invention may be implemented by computer software executable by a data processor of the mobile device, such as in the processor entity, or by hardware, or by a combination of software and hardware. Computer software or program, also called program product, including software routines, applets and/or macros, may be stored in any apparatusreadable data storage medium and they comprise program instructions to perform particular tasks. A computer program product may comprise one or more computer-executable components which, when the program is run, are configured to carry out embodiments. The one or more computer- executable components may be at least one software code or portions of it.

Further in this regard it should be noted that any blocks of the logic flow as in the Figures may represent program steps, or interconnected logic circuits, blocks and functions, or a combination of program steps and logic circuits, blocks and functions. The software may be stored on such physical media as memory chips, or memory blocks implemented within the processor, magnetic media such as hard disk or floppy disks, and optical media such as tor example DVD and the data variants thereof, CD. The physical media is a non-transitory media.

The memory may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The data processors may be of any type suitable to the local technical environment, and may comprise one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), 10 application specific integrated circuits (ASIC), FPGA, gate level circuits and processors based on multi core processor architecture, as non-limiting examples.

Embodiments of the inventions may be practiced in various components such as integrated circuit modules. The design of integrated circuits is by and large a highly automated process. 15 Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate.

The foregoing description has provided by way of non-limiting examples a full and informative description of the exemplary embodiment of this invention. However, various modifications 20 and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings and the appended claims. However, ail such and similar modifications of the teachings of this invention will still fall within the scope of this invention as denned in the appended claims, indeed there is a further embodiment comprising a combination of one or more embodiments 25 with any of the other embodiments previously discussed.

Claims

1. An apparatus comprising means for:

receiving, at a user equipment, an indication of a resource grant for a radio resource control request; and determining, in response to an event when the user equipment is in a radio resource control inactive state, whether to send the radio resource control request to move to a radio resource control connected state or move to a radio resource control idle state in dependence on said indication.

2. An apparatus according to claim 1, wherein the radio resource control request comprises a first request having a first size or a second request having a second size.

3. An apparatus according to claim 2, wherein the first request comprises a radio resource control resume request and the second request comprises a radio resource control connection request.

4. An apparatus according to claim 2 or claim 3, wherein means for determining whether to send the radio resource control request to move to a radio resource control connected state or move to radio resource control idle state comprises means for determining if the size of the first request is greater than the radio resource grant and if so, moving to the radio resource control idle state.

5. An apparatus according to claim 2 or claim 3, wherein means for determining whether to send the radio resource control request to move to a radio resource control connected state or move to radio resource control idle state comprises means for determining if the size of the first request is greater than the radio resource grant and, if so, sending the second request.

6. An apparatus according to any of claims 1 to 5, wherein the event comprises at least one of determining that data is available for transmission from the user equipment or selecting a new cell.

2^

7. An apparatus according to any of claims 1 to 6, comprising means for sending a random access preamble to a network and receiving the indication of the resource grant in response to the random access preamble in a random access response.

8. An apparatus according to any of claims 1 to 6, wherein the indication of the resource grant is received in system information from a network.

9. A method comprising:

10. A method according to claim 9, wherein the radio resource control request comprises a first request having a first size or a second request having a second size.

11. A method according to claim 10, wherein the first request comprises a radio resource control resume request and the second request comprises a radio resource control connection request.

12. A method according to claim 10 or claim 11, wherein determining whether to send the radio resource control request to move to a radio resource control connected state or move to radio resource control idle state comprises determining if the size of the first request is greater than the radio resource grant and if so, moving to the radio resource control idle state.

13. A method according to claim 10 or claim 11, wherein determining whether to send the radio resource control request to move to a radio resource control connected state or move to radio resource control idle state comprises determining if the size of the first request is greater than the radio resource grant and, if so, sending the second request.

14. A method according to any of claims 9 to 13, wherein the first event comprises at least one of determining that data is avertable for transmission from the user equipment or selecting a new cell.

15. A. method according to any of claims 9 to 14, comprising sending a random access preamble to a network and receiving the indication of the resource grant in response to the random access preamble in a random access response.

16. A method according to any of claims 9 to 14, wherein the indication of the resource grant is received in system information from a network.

17. An apparatus comprising:

at least one processor and at least one memory including a computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to:

receive, at a user equipment, an indication of a resource grant for a radio resource control request; and determine, in response to an event ’when the user equipment is in a radio resource control inactive state whether to send the radio resource control request to move to a radio resource control connected state or move to a radio resource control idle state in dependence on said indication.

18. .A computer readable medium comprising program instructions for causing an apparatus to perform at least the following:

receive, at a user equipment, an indication of a resource grant for a radio resource control request: and determine, in response to an event when the user equipment is in a radio resource control inactive state, whether to send the radio resource control request to move to a radio resource control connected state or move to a radio resource control idle state in dependence on said indication.