WO2012034580A1

WO2012034580A1 - Reduced radio resource control connectivity

Info

Publication number: WO2012034580A1
Application number: PCT/EP2010/063384
Authority: WO
Inventors: Hannu Tapio Hakkinen; Hannu Pekka Matias Vaitovirta
Original assignee: Nokia Siemens Networks Oy
Priority date: 2010-09-13
Filing date: 2010-09-13
Publication date: 2012-03-22
Also published as: ES2605979T3; US9622286B2; EP2617261B1; EP2617261A1; US20130208699A1

Abstract

Embodiments of the present invention relate to reduction of radio connectivity of a bearer service. Upon detection of low data transfer activity within a bearer service, radio connectivity of the bearer service is reduced so as to reduce signaling overhead in an air interface. However, a core network connection of the bearer service is maintained.

Description

Reduced Radio Resource Control Connectivity Field

The invention relates to the field of cellular radio telecom^¬ munications and, particularly, to controlling radio resource connectivit .

Background

In current long-term evolution (LTE) versions of cellular telecommunication systems developed within 3GPP (3^tQ Genera^¬ tion Partnership Project) , two radio resource control connec^¬ tion states are provided: an idle state and an RRC connected state. These two states are associated with Enhanced Packet Service Connection Management Idle (ECM-IDLE) and ECM- CONNECTED states on connection management level between user equipment (UE) and Enhanced Packet Core, i.e. a core network. In current LTE implementation, an SI interface between a ra^¬ dio access network (eUTRAN) and the core network (EPC) is connected to a serving base station (enhanced Node B) only in the RRC connected state with the UE . In a handover, the SI path is switched from a source eNB to a target eNB .

Many UEs run applications that produce "keep alive" type of messages for maintaining presence information, server regis^¬ tration, and/or access through a firewall, for example . These applications may be designed for general purposes, e.g. a personal computer (PC) connected to the Internet via LAN, ADSL, LAN etc. The configuration of this type of keep alive messaging, particularly a messaging interval, may not be op^¬ timized for mobile technologies. Transporting such a small amount of data per user causes high rate of radio network control signaling, when a high number of terminals run such applications over long p>eriods. Several simultaneous applica^¬ tions per user may increase rate of messaging without justi^¬ fying the maintenance of a continuous RRC connection. Brief description

According to an aspect of the present invention, there are provided methods as specified in claims 1, 3, 10 , and 12, According to another aspect, of the present invention, there are provided apparatuses as specified in claims 18, 20, 28, 30, and 37.

According to yet another aspect of the present invention, there is provided a computer prog-ram. product embodied on a. computer readable distribution medium as specified, in claim 38.

Embodiments of the invention are defined in the dependent claims ,

List of drawings

Embodiments of the present, invention are described below, by way of example only, with reference to the accompanying- draw- ings, in which

Figure 1 illustrates a general structure of a modern cellular telecommunication system having a flat radio access network architecture ;

Figure 2 illustrates a flow diagram of a process for reducing radio connectivity of a bearer service according to an em^¬ bodiment of the invention;

Figures 3 and 4 are extensions to the flow diagram of Figure 2, illustrating radio connectivity restoration and release of the bearer service according to embodiments of the invention; Figure 5 is a signaling diagram illustrating transfer of con^¬ text parameters of the bearer service with reduced radio con^¬ nectivity according to an embodiment of the invention;

Figure 6 illustrates rerouting of a core network connection of the bearer service according to an embodiment of the in- vention; and

Figures 7 and 8 illustrate block diagrams of apparatuses ac^¬ cording to embodiments of the invention. Description of embodiments

The following embodiments are exemplary. Although the speci^¬ fication may refer to "an", "one", or "some" embodiment (s) in several locations, this does not necessarily mean that each such reference is to the same embodiment ( s ) , or that the feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments. Furthermore, words "comprising" and "including" should be understood as not limiting the described embodi^¬ ments to consist of only those features that have been men^¬ tioned and such embodiments may also contain fea^¬ tures/structures that have not been specifically mentioned. A general architecture of a cellular telecommunication system providing- voice and data transfer services to mobile termi^¬ nals is illustrated in Figure 1. The cellular telecommunica^¬ tion system of Figure 1 has elements of a UMTS LTS (Universal Mobile Telecommunication System Long-term Evolution) system standardized within 3GPP (3^rd Generation Partnership Pro- ject), but it should be noted that embodiments of the present invention may be applied to other cellular telecommunication systems as well. Referring to Figure 1, the cellular telecom^¬ munication system comprises a radio access network comprising a plurality of base stations (enhanced Node B in the UMTS LTE } 100, 102, 104. The UMTS LTE system has a flat radio ac^¬ cess network structure which means that the radio access net^¬ work comprises only base stations without a centralized con^¬ troller as a radio network controller (RNC) in a legacy UMTS W--CDMA (wideband code division multiple access) system. The base stations 100 to 104 are configured to carry out radio resource control functionalities independently, but they may communicate with other base stations over an X2 interface and with a core network 106 over an SI interface so as to imple^¬ ment a self-organizing network and flexible spectrum utiliza- tion. The core network (an evolved packet core in the UMTS LTE) comprises a mobility management entity (MME) handling signaling between terminal devices and the core network, and it controls bearers on a session level in a non-access stra- turn (NAS) protocol. The core network comprises also gateway nodes (SAE-GW) handling data routing. An interface between a base station 104 and a terminal device 110 is called Uu in^¬ terface in the UMTS LTE .

Figure 2 illustrates a flow diagram of a process for reducing radio resource control connectivity according to an embodi^¬ ment of the invention. Some of the steps of the process are carried out in the base station (eNode B) , some steps are carried out in the core network (EPC) , and some steps are carried out in the terminal device (UE, user equipment) . The process starts in step 200. In step 202, a connection (a bearer service) is provided between the EPC and the UE through an eNode B currently serving the UE . The MME of the EPC may establish an Sl-AP signaling connection and other connections needed to control the bearer service in the EPC and in the radio access network, the serving eNode 3 may es^¬ tablish a radio resource control (RRC) connection with the UE and carry out. RRC functionalities so as to schedule radio re^¬ sources to the bearer service, and the UE may carry out RRC setup procedures with the serving eNode B, as known in the art. In general, step 202 may include conventional bearer setup procedures carried out by the EPC, serving eNode B, and. UE ,

In an embodiment, the eNode B provides the UE with a paging discontinuous reception (DRX) parameter that allows the UE to synchronize to a paging period of the eNode B in an idle state and. under reduced radio connecti ity.

In step 204, the serving eNode B determines that data transfer activity of the connection is low or non-existent, This may result, from, bursty traffic common to messaging ap^¬ plications, e-mail, etc., or it may result from frequent transmission of small amounts of information, e.g. signaling messages, or it may be otherwise determined that, a full or continuous RRC connection is not efficient on a. system level. In response to the determination of the low data transfer ac^¬ tivity, the eNode B stores in step 206 context parameters of the radio connection and. releases radio resources of the ra^¬ dio connection while maintaining the core network connection. ^

In other words, the EPC still assumes that the bearer service is operational, while eNode B has reduced the radio connec^¬ tivity and suspended RRC procedures, i.e. connection over the SI interface is maintained for the bearer service.

In step 208, the eNode B transmits a command to re^¬ duce the radio connectivity to the US, and the UE receives the command from the eNode B in step 210, The command may be an RRC connection release message with an additional field that instructs the UE to release the radio connection but store its context parameters for fast restoration. In re^¬ sponse to the received command, the UE stores in step 212 context parameters of the radio connection and adopts at least some idle state procedures. Similarly, the eNode B adopts at least some the idle state procedures for the UE, e.g. handovers of the UE are omitted. In steps 206 to 212, the eNode B and the UE initiate a procedure for delayed re^¬ lease of the whole bearer service, and the final release of the bearer service may occur upon the expiry of a timer, once a determined number of cell selections have been carried out by the terminal device and/or once a determined event in mo^¬ bility of the terminal device has been observed (the number of cell selections or a determined relocation of the terminal device) . The timer and tracking the number of the cell selec^¬ tions may be started in response to the initiation of the procedure for delayed release of the whole bearer service.

The UE may carry out the counting of the number of cell selections during the procedure for the delayed release of the bearer service.

In the embodiment of Figure 2, the RRC connectivity of the bearer service is reduced while the core network con^¬ nection of the bearer service is maintained. In other words, the EPC assumes an EC (Enhanced Packet Service Connection Management) Connected state. The non-access stratum layer of the UE may also assume the ECM Connected state, i.e. the con- nectivity is reduced only in the lower protocol layers. The context parameters of the RRC connection are also stored in the both the UE and eNode B for quick recovery upon reestab- lishment of the RRC connection. Thus, the connection is actu- _r

Ό

ally maintained but the signaling in the radio (Uu) interface is reduced, as the radio connection is practicall released and as the UE adopts at least some idle state procedures. The reduction of the Uu interface signaling also reduces power consumption of the UE . The idle state procedures the UE adopts may include idle state cell (re) selection caused by the mobility of the US , The cell selection includes selection of a cell (of a given eNode B) where the UE chooses to camp and receive a broadcast control channel. The cell may be se- lected on the basis of radio measureme ts carried out. by the US. The ceil selection may also include a location registra^¬ tion update so that the network knows the area where the UE is located. The stored RRC context parameters may include ra^¬ dio link control (RLC) , medium access control (MAC) , and packet data convergence protocol (PDCP) parameters, e.g. quality-of-service (QoS) parameters, identifiers of the UE and the connection (both radio bearer service and the SI in^¬ terface bearer service}, bearer service parameters, measure^¬ ment setup parameters, security parameters including various encryption keys, and any valid counters.

As mentioned above, the context parameters of the ra^¬ dio connection are stored in both the UE and. eNode B for quick recovery when the reestablishment of the radio connec^¬ tion is triggered. A triggering event may be the detection of downlink data traffic in the bearer service from the EPC, a connection reestablishment request, made by the UE or, in gen^¬ eral, detection of increased traffic activity in the bearer service. Figure 3 illustrates an extension to the process of Figure 2. Referring to Figure 3, step 300 is carried out af- ter step 212 of Figure 2. In step 300, the eNode B detects said increased data transfer activity in the bearer service established in step 202. The detection of increased data transfer activity triggers the reestablishment of the RRC connection, and. both the eNode B and. the UE restore the RRC connection by using the context parameters stored in steps 206 and 212. As the RRC connection reestablishment uses the stored context parameters, the reestablishment is fast and signaling in the Uu interface is reduced. In an embodiment, the reduced radio connectivity is implemented by a. gradual release of the RRC context. This transition mechanism may be called Delayed RRC Connection Release, for example. In a first phase, the RRC context parame^¬ ters are stored and the radio connection is released (steps 206, 212 } and., i a second ha se , the context para.meters are discarded and the core network connection in the SI interface is released.

The command to reduce the radio connectivity trans^¬ mitted in step 208 and received i step 210 may be a conven^¬ tional RRC Connection Release message with additional fields as presented in Table 1.

(Table 1}

The timer defines a time period for the reduced RR.C connectivity before the bearer service is released. In other- words, the fast restoration of the full RRC connectivity is possible until the timer expires. The time duration counted by the timer may be defined by an index selected by the serv^¬ ing eNode B, and the number of available durations defines the number of bits needed to index the duration to be used. The duration of the timer may be a few seconds, and different options may include, for example, the following durations: 10s, 30s, Imin, 2min and Srainlf the system supports only a single timer, the duration of the timer is explicit to the UE without a separate field in the RRC Connection Release mes^¬ sage ,

A cell selection threshold defines the number of cell selections the UE may make in the reduced connectivity before the context relocation is triggered. In an embodiment, the cell selection threshold is two or higher. The cell selection threshold may be determined by the serving eNode B on the ba^¬ sis of a paging strategy and/or the mobility of the UE . A high cell selection threshold prevents unnecessary context relocations and may reduce signaling in an X2 interface (s) . On the other hand, a low cell selection threshold prevents the retrieval of the context over numerous X2 legs. In case of high mobility, multiple context relocations may be carried out. i the reduced connectivity state. The context relocation comprises transfer of the context parameters from the eNode B that stored the context parameters in step 206 to an eNode B in whose ceil the UE currently camps. The transfer of the context parameters may be carried out over the X2 inter^¬ face (s). The core network connection may still be maintained with the eNode B that initiated the reduced connectivity state .

A cell selection validity parameter defines whether inter-frequency cell selections and/or cell selections to other closed subscriber groups (CSG) are allowed. The value of the parameter may depend on the X2 interface connectivity of the serving eNode B, i.e. cell selections are only allowed to those eNode Bs that have X2 connectivity to the eNode B that stored the RRC context. One or two bits may be needed for this parameter depending on implementation, i.e. the number of different options supported, but the information ele^¬ ment may comprise a higher number of bits . With respect to the cell selection validity, the eNode B may provide the UE with a list of neighbour ceils to which the cell selection is allowed. The list may be unique for each cell and/or for each eNode B. The list may be broadcasted by the eNode B, or the eNode B may include the list in an additional field in the RRC Connection Release message. The UE may use the list in addition to or instead of the cell selection threshold to de- „

"'3

termine whether or not to select a given cell and whether or not to request the context tran s fer .

In general, the number of bits in each information element in Table 1 is selected according to the implementa- tion and specifications of the telecommunication system. The RRC messages may be efficiently coded such that a range of each information element needs not be an integer power of 2.

The release of the bearer service may be gradual and timer-based, as described above. Figure 4 illustrates a flow diagram of the gradual release of the bearer service. The process may be carried out in the eNode B and/or in the US , In response to step 206 or 212 of Figure 2, a timer is started in step 400. With respect to the UE, the time counted by the timer may be determined from the command received from the eNode B in step 210. The timer used by the eNode may be the same used by the UE, or it may be longer to take into ac^¬ count the communication of the command in steps 208 and 210. In step 402, it is determined whether the timer has expired before the context restoration has been triggered. If the context restoration is triggered before the expiry of the timer, step 302 is carried out, i.e. the RRC connection is reestablished by using the stored, context parameters. On the other hand, if the timer has expired without context restora^¬ tion, the process proceeds to step 406 where the stored con- text parameters are discarded and where the UE adopts the idle mode. Using a timer in both the UE and the eNode B re^¬ duces signaling in the Uu interface, as no separate release commands are necessary.

In an alternative embodiment, the reduced connec- tivity in the radio interface is implemented by providing a new RRC state in addition to the RRC connected and RRC idle states. The new state may be called RRC Context state, for example, wherein the core network connection is maintained but the RRC connection is virtually released.

With respect to the context relocation mentioned above in re^¬ lation to Table 1, the context relocation in the radio access network, may depend on the numbe of cell (re) selections the US has made in the reduced, radio connectivity state, i.e. in , _Q

the state where the US has adopted at least some idle mode procedures (including cell selection) but. is not yet in the idle state. Figure 5 is a signaling- diagram illustrating the context relocation as a result of the mobility of the UE in the reduced connectivity. Referring to Figure 5, the UE and the currently serving eNode B (ENB#1 in Figure 5} adopt, the Delayed RRC Connection Release mode for reduced connectivity in step SI in Figure 5. The UE reads the cell selection threshold and monitors the number of cell selections made af- ter the reception of the RRC Connection Release message of

Table 1. In S2, the UE carries out idle state cell selection when having the reduced connectivity in S2, wherein the UE selects ENB#2 as the new cell where to camp, and increments a counter counting the number of cell selections. In order to exclude "ping- pong" cell reselections from the counting, the UE may store a list of a number of previously selected cells, e.g. two, and exclude those cells from the counting in case they are reselected. The UE may also store the list of previ^¬ ously visited cells so as to avoid, continuous reselection. be- tween two cells. In addition to reselection in idle state the UE may also consider previously visited cells due to handover during previous full RRC connectivity. In such a counting al^¬ gorithm the UE may omit counting multiple intermediate cell selections when reselecting a previously selected or con- nected cell after a sequence of cell selections of other cells between the selection and. the reselection of the cell. In other words, when the UE reselects a cell, a number corre^¬ sponding to the cells selected between the selection and the reselection of the cell are reduced in the counting algo- rithm. In S3, the UE has made a determined number of cell se^¬ lections defined, by the cell selection threshold, (in this em^¬ bodiment, the value is exemplary two) , and the UE sends to a currently selected eNode 3 (ENB#3) an RRC Context Relocation Request message in S4, thereby requesting the ENB#3 to re- trieve the stored RRC context. The UE may include its unique identifier in the RRC Context Relocation Request message. The identifier may be an identifier that is locally unique over frequencies supported by the system. The identifier may in- , _j

elude a cellular radio network temporary identifier (C-RNTI) previously assigned to the UE and, optionally, a short MAC identifier (ShortMAC-I) . In another embodiment, the identi^¬ fier may be a globally unique identifier, e.g. a cellular global identifier (CGI) . In another embodiment, the identi^¬ fier comprises a physical cell identifier (PCI) with a car^¬ rier index. When inter-frequency cell selection is allowed by the cell selection validity parameter and when the UE carries out the inter-frequency cell selection, a new RRC connection setup may be needed to communicate the RRC Context Relocation Request message. In an embodime t, the inter-frequency cell selection automatically triggers the context relocation regardless of the counted number of cell selections. The UE may also provide an identifier of the eNode B that currently stores the context to facilitate the transfer of the context. The reception of the RRC Context Relocation Request message in the ENB#3 triggers the E B#3 to communicate with the ENB# 1 over the X2 interface in S5 so as to transfer the RRC context of the UE from the ENB# 1 to the E B#3. It is possible that there is no direct X2 connection between the ENB#1 and ENB#3 and, then, the RRC context may be relayed through one or more intermediate eNode Bs, e.g. ENB#2. Upon successful retrieval of the RRC context, the currently selected ENB#3 stores the RRC context, and it may also transmit to the UE an RRC Con- text Relocation Response message in ,36 so that the UE may up^¬ date the eNode 3 that, currently stores the context parame^¬ ters. The RRC Context Relocation Response may be ciphered and integrity-protected, and it may be transmitted by using a common or dedicated signaling radio bearer (SRB0 or SRB1, re- spectively) . The currently selected eNode B may also assign a new C-RNTI to the UE .

The UE may be configured to use contention-based random ac^¬ cess in order to enable the above-mentioned context reloca^¬ tion procedure. In the context relocation procedure, the eNode B may be configured to reconfigure at least one of the following parameters of the RRC context: C-RNTI, dedicated physical resources and a security context, to update the stored RRC context parameters accordingly, and to transmit an appropriate signaling message providing the reconfigurations to the UE . The UE may be configured to update the context, pa^¬ rameters according to the received parameters but not to re^¬ spond to such a message or, in general, to any received RRC Context Relocation Response message so as to avoid unneces^¬ sary signaling. The e ode B can verify the message reception, and thus the new C-RNTI allocation, based on Radio Link Con^¬ trol (RLC) Acknowledgement.

In an embodiment, the eNode B sends both the optional recon- figuration information and context relocation i formation as combined into the same message of the random access proce^¬ dure, thereby reducing the number of signaling messages. The physical resource configuration for this message is still de^¬ fault for the cell, and applied keys for ciphering and integ- rity protection are derived based on the security context from the previous cell. An indication of at least some of the keys to be applied may also be included in the same message. The reconfiguration message may be transmitted as ciphered and/ or as integrity protected before the contention is re- solved within said random access procedure. Accordingly, the message is transmitted under contention and may fail, for ex^¬ ample due to a preamble collision with another UE accessing at the same time. Upon reception of no proper RRC Context Re^¬ location Response message from the currently selected eNode B, the UE may be configured to repeat random access conten^¬ tion and to retry the context, relocation request in order to receive the new C-RNTI . In general, the US may be configured to carry out contention-based random access whenever it needs to transmit information (control or data) to the eNode B hav- ing the UE camping in its cell. In this case, at least the dedicated physical resources need to be reconfigured for the purpose of further communication in the selected cell.

In another embodiment, the eNode 3 receiving the RRC Context Relocation Request, message may first determine whether or not the context transfer is necessary, i.e. the decision about the transfer of the context is made by the radio access net^¬ work and not necessarily only on the basis of the number of cell selections. The eNode 3 making- the decision may deter- ,„

mine the number of X2 legs between itself and the eNode B currently storing the context. If the context, is stored in an eNode B only one X2 leg^' (or a number of X2 legs below a threshold) away from the eNode B making the decision, the eNode B receiving the request may decide not to transfer the context, and it. transmits a RRC Context. Relocation Rejected message to the UE . Upon reception of such a message, the UE may be configured to request the relocation of the context after every cell selection until the context is transferred, or the UE may be configured to reset the counter counting the cell selection, and carry out the new context tra sfer request when a sufficient number of new cell selections has been made .

In a further alternative embodiment, context, relocation is not supported but, instead, the RRC connection is immediately re^¬ leased if an UE has carried out cell reselection a number of times exceeding a threshold without communication of signal^¬ ing or data between the radio access network and the UE . The UE may send a High Mobility Indication message, for example, so as to initiate synchronized state transition into the idle state in the radio access network and in the core network (EPC) .

When counting- the number of cell selections during the proce^¬ dure for the delayed release of the bearer service in any em- bodiment, e.g. when determining context release and/or con^¬ text relocation, the UE may exclude from, the counting of the number of cell selections a reselection of a cell that has been previously selected during the procedure for the delayed release of the bearer service. In other words, a cell rese- lection does not increment the counter. On the other hand, the cell reselection may increment the counter once a deter^¬ mined number of cell selections of other cells ave been made between the initial selection and the reselection of the cell .

The core network connection of the bearer service may be left intact, i.e. it may still be connected to the original eNode B so as to avoid un ecessary rerouting of the core network connection in case the bearer service is to be released (step 406} . With respect to Figure 5, ENBf1 may store an identifier of the ENB#3 so that it knows to which eNode B the context was transferred so that the context and the core network con^¬ nection may be relinked quickly in the reestablishment .

With respect to the restoration of the bearer service and the RRC context, (step 302) , the restoration of the context may be initiated by the eNode B that has the core network (SI) con^¬ nection of the bearer service upon detection of downlink data in the core network connection. The eNode B may then forward the downlink data to the eNode 3 that, currently stores the UE context. The identifier of the eNode 3 storing the co text may be stored in the eNode B having the core network connec^¬ tion of the bearer service, as described above. Upon recep^¬ tion of the downlink data, the eNode 3 storing the UE context may be configured to transmit a paging request, to neighboring eNode Bs to which an X2 connection is provided so as to page the UE , The eNode Bs receiving the paging request may attempt paging the UE over the Uu interface and, optionally further spread the paging to other eNode Bs through respective X2 connections. Paging over two (or more) X2 legs may be used as a backup if the UE does not respond to the paging request transmitted by the eNode 3s within one X2 leg from, the eNode B that stores the US context. When the mobility of the UE has been determined to be low or non-existent, the eNode B stor- ing the UE context may be configured to page the UE only in the Uu interface, i.e. paging- over the X2 connections is used as the backup. A paging- message transmitted to the Uu inter^¬ face by any eNode B may comprise a CGI and a C-RNTI of the UE, and the paging may be carried out according to the paging DRX parameter provided to the UE ,

In an optimum case, the bearer service of the US is restored in the same cell that was previously configured for full ser^¬ vice for the UE . Then, both the UE and the serving eNode B may apply conventional MAC recovery procedures. When the bearer service is restored in another cell, context retrieval over the X2 interface and reconfiguration of at least some context parameters may be necessary. A need for dow link sig^¬ naling or data traffic may trigger either paging or a physi- cal dedicated control channel (PDCCH) command, which initi^¬ ates the restoration of the bearer service. The full RRC con^¬ nection may be restored by random access procedure typically without any reconfiguration. In a generic case where the UE initiates the RRC connection restoration as response to a paging message or upon detection of a need to transmit uplink data over the bearer service, the US may be configured to transmit to a currently selected cell a RRC Connection Resume Request message through random access contention. The RRC Connection Resume Request, message may comprise the identi^¬ fier (s) of the UE, and the identifier (s) may be the same as used in the RRC Context Relocation Request message. Upon re^¬ ception of the RRC Connection Resume Request message from the US, the eNode B initiates the RRC connection restoration by retrieving the context parameters of the bearer service and restoring the RRC connection by using at least some of the stored context parameters, preferably all the stored RRC con^¬ text parameters are default for the reconfiguration. Upon re^¬ trieval of the context parameters, the eNode B may respond to the US by transmitting a secured RRC Connection Reconfigura^¬ tion Message. Similar alternative embodiments are applicable as described above with context, relocation.

When the RRC connection is reestablished, the eNode B cur^¬ rently serving the UE or the eNode B currently having the core network connection of the bearer service may determine whether or not to reroute the core network connection to the eNode B currently serving the US, or they may make the deci^¬ sion in cooperation. The amount of uplink and/or downlink data to be transferred and/or the number of X2 legs between the eNode Bs may be used as a basis for the decision. If only a small amount (below a given threshold) of data is to be transferred over the reestablished RRC connection and/or if the number of X2 legs is low, the current core network con^¬ nection may be maintained. On the other hand, if the amount of data to be transferred is high (above the threshold) and/or if the number of X2 legs is high_f the transfer of the core network connection may be carried out as illustrated in Figure 6, Accordingly, the core network connection is routed , -

1

from the core network directly to the e ode B restoring the RRC connection (through an SI interface) instead of relaying the core network connection over X2 interfaces. The rerouting of the core network connection reduces the amount of data transferred over the X2 legs. On the other hand, maintaining the current, core network connection and relaying the data over X2 connections reduces signaling between the core net^¬ work and the radio access network and the US, Additionally, there would be no need to reconfigure some of the parameters of the bearer service. In another embodiment, the rerouting of the core network connection is triggered by the context relocation, i.e. the core network connection is rerouted to the eNode B to which the context is transferred, or the rerouting of the core network connection is triggered upon a determined number of context relocations (higher th.an one) ,

The rerouting of the core network (SI) connection may be carried out by using procedures similar to those disclosed in a co-pending PCT application having a filing number

PCT/EP2010/062546.

Next, access stratum (AS) security key management is dis^¬ cussed in connection with the reduced connectivity state. When the UE needs to communicate in a new cell because of mo^¬ bility and the cell selection in the reduced connectivity state, horizontal key derivation may be used to derive key (s) for the RRC context relocation request and RRC connection re^¬ configuration messages. An old next hop chaining counter (NCC, defines whether the next key is based on the current one or should the next hop be updated) may be used by de^¬ fault , but a new physical cell identifier and EARFCN-DL (En- hanced UMTS Terrestrial Radio Access Network Absolute Radio Frequency Channel. Number for downlink) may be applied when the UE has selected a new cell in the reduced connectivity state. When the core network connection is rerouted, the MME may be configured to provide a new pair of Next Hop key (NH) and NCC ({NH, NCC}) according to a vertical key derivation process, and the eNode B may include the new keys (NH, NCC) in the RRC connection reconfiguration message transmitted to the US so that they may be used in deriving- appropriate keys , _^

in the eNode B and in the US . When the core network connec^¬ tion has not been rerouted and when the RRC connection is re^¬ established in the same eNode B that initiated the reduced connectivity state, all the keys used before the reduced con- nectivity may be restored. When rerouting of the core network connection is not used and when the context, is transferred and reconfigured in a new eNode B , horizontal key derivation may be used to derive the necessary keys. In this manner, the number of messages is reduced, specially from MME point of view.

If the RRC connection reestablishment fails, the UE and/or the eNode B may be configured to carry out a conventional RRC connection setup procedure. Then, the stored context parame^¬ ters may be discarded, as they are not valid anymore, and the core network connection (and SI context of the bearer service) may also be released and a new one established.

With respect to the paging determined by the eNode B on the basis of downlink data traffic, the MME may provide a System Architecture Evolution Temporary Mobile Subscriber Identifier (S-TMSI) to the radio access network through the core network connection, and the S-TMSI may be stored as part of the stored context parameters. Accordingly, the eNode B having access to the context parameters are able to initiate the paging without first communicating with the MME to obtain the S-TMSI. Accordingly, the paging process is simplified and the signaling over the SI interface is reduced. In another em^¬ bodiment, the eNode B triggering the paging- may request the MME to carry out the paging, and the paging may be carried out in a conventional manner from there on. In such a case, the MME may be configured to be aware that the existing core network connection of the bearer service is associated with the paging (eNode B may transmit an identifier of the core network connection or the bearer service related to the pag^¬ ing) and to use the core network connection in the paging procedure. In yet another embodiment, both paging options are available for use, and the UE may be configured to listen to both types of paging, i.e. one triggered by the eNode B and. another triggered by the MME, In an embodiment, the S-TMSI. , _g

may be applied to calculating a paging occasion (PO) for both types of paging, as triggered either by the eNode B or MME . An advantage is that the UE needs to listen to only one PO sequence, while the eNode B may still use radio-based identi- tiers in the paging, without a need to update S-TMSI due to the intimacy of the subscriber.

Figure 7 illustrates an embodiment of an apparatus for con^¬ trolling a bearer service between the core network and the terminal device in the above-described manner. The apparatus may be the base station of a radio access network, e.g. the eNode B, or the apparatus may form part of the base station, and the apparatus may implement the above-described struc^¬ tures and f nctionalities of the eNode in connection with the reduced connectivity state of the bearer service. The appara- tus comprises input/output (I/O) interface components 610 to establish the above-mentioned signaling connections with the core network, other base stations, and the UEs, The I/O in^¬ terface components 610 may comprise radio interface compo^¬ nents 612 configured to establish radio connections with the UEs, and wired interface components 614 configured to imple^¬ ment IP (Internet Protocol) and/or other types of connections towards the core network (SI interface) . The apparatus may use radio and/or wired interface components 612, 614 to im^¬ plement the connections with other base stations (X2 inter- face) . The radio interface components 612 may comprise stan^¬ dard well-known radio transceiver components such as ampli^¬ fier, filter, frequency-converter, (de) modulator, and encoder/decoder circuitries and one or more antennas.

The apparatus may further comprise a memory 608 that stores computer programs configuring the apparatus to perform, the above-described functionalities of the eNode B, The memory 608 may also store a database storing RRC context parameters for one or more bearer services associated with one or more UEs that nave been communicating with the eNode B. The appa- ratus further comprises a timer 606 to count the time allowed for the reduced radio connectivity state before the bearer service is released. , _n

ii

The apparatus further comprises a communication controller circuitry 600 operationally connected to the memory 608 and. the I/O interface components 610 to control the communication connections of the base station. The communication controller circuitry 600 may comprise a RRC circuitry 602 controlling the radio resources of the terminals devices served by the base station comprising the apparatus. The communication con^¬ troller circuitry 600 may further comprise an X2/S1 interface controller circuitry 604 handling connections to the other base stations (X2) and to the core network (SI) . The communi^¬ cation controller circuitry may establish the bearer service between a given terminal device and the core network by con^¬ trolling the RRC circuitry to carry out RRC connection establishment and other RRC functionalities with the terminal de- vice, and by communicating with the core network through the X2/S1 controller circuitry 604 so as to establish the core network connection of the bearer service. The communication controller circuitry may also monitor the bearer service and determine whether or not to reduce the radio connectivity, as described above. Upon determining to reduce the radio connec^¬ tivity as a result of low data transfer activity in the bearer service, the communication controller circuitry 600 may configure the RRC circuitry to transmit the RRC Connection Release message of Table 1 to the terminal device and to store context parameters of the RRC connection in the memory 608. The communication controller circuitry 600 may, however, be configured to maintain the core network connection, i.e. it may control the X2/S1 controller circuitry 604 to maintain the core network connection. Upon RRC context transfer, the communication controller circuitry 600 may configure the

X2/S1 controller circuitry 604 to negotiate with neighboring base stations so as to transfer the RRC context parameters from the memory 608. In case of rerouting the core network connection, the commu ication controller circuitry may con- figure the X2/S1 controller circuitry 604 to negotiate the release of the core network connection of the bearer service. The circuitries 602, 604 of the commu ication controller circuitry 600 may be carried out by the one or more physical _{2 Q}

circuitries or processors. In practice, the different cir^¬ cuitries may be realized by different, computer program mod^¬ ules ,

In an embodiment, the apparatus carrying out the era- bodiments of the invention in the base station comprises at least one processor 600, 602, 604 and at least one memory 608 including- a computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to carry out the steps of the process of Figure 2 that are carried out in the eNode 3, In further embodiments, the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to carry out any one of the embodiments relaxed to the reduced connectivity state in the base station, as described above in connection with Figures 2 to 6. Accordingly, the at least one processor, the memory, and the computer program code form processing means to carry out embodiments of the present invention in the base station,

Figure 8 illustrates an embodiment of an apparatus applicable to a terminal device. In an embodiment, the apparatus of Figure 8 is the terminal device. The apparatus may comprise a communication controller circuitry 700 configured to control cellular radio connections in the terminal device. The commu- nication controller circuitry 700 may comprise a control part 702 handling all the control signaling communication with the radio access network and the core network. The co trol part 702 communicates with the RRC circuitry 602 of the base sta^¬ tion so as to control the radio connections of the bearer services . The communication controller circuitry 700 further comprises a data part 704 that handles transmission and re^¬ ception of payload data. The control part 702 may be config^¬ ured to process the RRC messages received from the base sta^¬ tion and transmitted to the base station. The control part may also control the reduced RRC connectivity state for a given bearer service, as instructed by the serving base sta- t. ion. In the reduced radio connectivity state, the contro1 part may monitor data in a buffer of the data part. If the buffer contains a sufficient amount of data of the bearer service that has the reduced radio connectivity state, the control part may trigger a random access procedure so as to request reestablishment of the radio connectivity for the bearer service. The control part may also control the cell selections according to an idle state cell selection procedure in the reduced radio connectivity state and count the number of cell selections that have been made. Upon a suffi^¬ cient number of cell selections, the control part 702 may trigger the transmission of the RRC Context Relocation Re^¬ quest message, as described above. The circuitries 702, 704 of the communication controller circuitry 600 may be carried out by the one or more physical circuitries or processors. In practice, the different, circuitries may be realized by dif^¬ ferent computer program modules.

The apparatus may further comprise a memory 708 that stores computer programs configuring the apparatus to perform the above-described functionalities of the terminal device. The memory 708 may also store communication parameters and other information needed for the cellular connections. The memory 708 may also store a database storing RRC context parameters for one or more bearer services that are operational or in reduced radio connectivity state, as described above . The ap^¬ paratus further comprises a timer 710 to count the time al^¬ lowed for the reduced radio connectivity state before the bearer service is released. The apparatus may further com^¬ prise radio interface components 706 providing the apparatus with radio communication capabilities with the radio access network. The radio interface components 706 may comprise standard well-known components such as amplifier, filter, frequency-converter, (de) modulator, and encoder/decoder circuitries and one or more antennas.

In an embodiment, the apparatus carrying out the em^¬ bodiments of the invention in the terminal device comprises at least one processor 700, 702, 704 and at least one memory 708 including a computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to carry out the steps of the process of Figure 2 that are carried out in the terminal device. In further embodiments, the at least, one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to carry out any one of the embodiments related to the reduced connec^¬ tivity state in the terminal device, as described above in connection with Figures 2 to 6, Accordingly, the at least one processor, the memory, and the computer program code form processing means to carry out embodiments of the present in- vention in the terminal device .

As used in this application, the term Circuitry' refers to all of the following: (a) hardware-only circuit implementations, such as implementations in only analog and/or digital circuitry, and (b) to combinations of circuits and software (and/or firmware), such as (as applicable}: (i) a combination of processor (s) or (ii) portions of processor (s) /software in^¬ cluding digital signal processor (s) , software, and mem^¬ ory (ies) that, work together to cause an apparatus to perform various functions, and (c) to circuits, such as a microproc- essor(s) or a portion of a microprocessor ( s ) , that require software or firmware for operation, even if the software or firmware is not. physically present. This definition of

^circuitr ' applies to all uses of this term in this applica^¬ tion. As a further example, as used in this application, the term "circuitry" would also cover an implementation of merely a processor (or multiple processors) or portion of a proces^¬ sor and its (or their) accompanying- software and/or firmware. The term "circuitry" would also cover, for example and if ap^¬ plicable to the particular element, a baseband integrated circuit, or applications processor integrated circuit for a mobile phone or a similar integrated circuit in a server, cellular network device, or other network device.

The processes or methods described in Figures 2 to 6 may also be carried out in the form of a computer process defined by a computer program. The computer program may be in source code form, object code form, or in some intermediate form, and it may be stored in some sort of carrier, which may be any en^¬ tity or device capable of carrying the program. Such carriers .„

include a record medium, computer memory, read-only memory, electrical carrier signal, telecommunications signal, and software distribution package , for example. Depending on the processing power needed, the computer program may be executed in a single electronic digital processing unit or it may be distributed amongst a number of processing units.

An embodiment of the invention is a method comprising- : pro^¬ viding, in a base station apparatus of a radio access network of a cellular telecommunication system, a bearer service be- tween a terminal device and a core network through the base station, wherein the bearer service comprises a radio connec^¬ tion between the base station and the terminal device and a core network connection between the base station and the core network. The method further comprises determining that data transfer activity of the bearer service is low and, in re^¬ sponse to the determination of low data transfer activity, storing context parameters of the radio connection, releasing radio resources of the radio connection while maintaining the core network connection, and initializing a procedure for de- laved release of the whole bearer service. The procedure for the delayed release comprises: starting a timer in response to the release of the radio resources of the radio connection and, in response to expiry of the timer, releasing the radio connection and the core network connection.

In an embodiment, the release in response to the ex^¬ piry of the timer is carried out without any control signal^¬ ing- with the terminal device.

An embodiment of the invention is a method comprising: pro^¬ viding, in a base station apparatus of a radio access network of a cellular telecommunication system., a bearer service between a terminal device and a core network through the base station, wherein the bearer service comprises a radio connec^¬ tion between the base station and the terminal device and a core network connection between the base station and the core network. The method further comprises: determining that data transfer activity of the bearer service is low and, in re^¬ sponse to the determi ation of low data transfer activity, storing- context parameters of the radio connection, releasing radio resources of the radio connection while maintaining the core network connection, and initializing a procedure for delayed release of the whole bearer service. The procedure for the delayed release comprises: utilizing at least some of the same mobility procedures as in an idle state for the terminal device associated with said bearer service, and transferring the stored context parameters to another base station accord^¬ ing to the mobility of the terminal device in terms of rela^¬ tive distance with respect to the cell during the procedure for delayed release of the whole bearer service.

In an embodiment, the method (s) further comprise upon detection of increased data transfer activity in the bearer service, restoring the radio connection by using the stored context, parameters of the radio connection. In response to the restoration of the radio connection, the embodiment may further comprise determining whether or not to reroute the core network connection on the basis of at least one of: mo^¬ bility of the terminal device, and a degree of the detected data transfer activity, and rerouting the core network con- nection upon determining high data transfer activity and/or high mobility of the terminal device after the radio re^¬ sources of the radio connection were released.

I an embodiment, the method further comprises receiving con^¬ text parameters of another terminal device during said proce- dure for the delayed release of the bearer service of said other terminal device and, in connection with the transfer of the context parameters bearer service, reco figuring at least some of the context parameters and causing transmission of at least some of the reconfigured context parameters to said other terminal device associated with the transferred context parameters in a single reconfiguration message. The transfer of the context parameters may be triggered through a random access procedure between said base station and said other terminal device, and the reconfiguration message may be transmitted as ciphered and/or as integrity protected before a contention is resolved within said random access procedure. I an embodiment, the method further comprises during the procedure for the delayed release and upon detection of in- . _c

Z 5

creased downlink data transfer activity in the bearer service: paging the terminal device in a cell controlled by said base station, and transmitting a paging- request related to said terminal device at least to the other base station.

In an embodiment, the base station receives from a mobility management entity of said core network a paging identifier of the terminal device and initiates a paging procedure without involving the mobility management entity in the paging proce^¬ dure .

An embodiment, provides a method comprising: providing, in a terminal device, a bearer service comprising a radio connec^¬ tion and a radio resource control connection with a serving base station of a radio access network of a cellular telecommunication system and a core network connection with a core network of the cellular telecommunication system. The method further comprises: receiving a command to reduce radio con^¬ nectivity of the bearer service from the serving base station and, in response to the received command, storing context, pa^¬ rameters of the radio connection in a memory, adopting at least some idle state procedures without releasing the whole bearer service, and initializing a procedure for delayed re^¬ lease of the whole bearer service. The procedure for the de^¬ layed release comprises: starting a timer in response to the release of the radio resources of the radio connection, and in response to expiry of the timer, releasing the whole bearer service and entering an idle state.

I an embodiment, the release of the bearer service i re^¬ sponse to the reception of the command to release the radio resources is carried out without any control signaling with the base station.

An embodiment, provides a method comprising: providing-, in a terminal device, a bearer service comprising a radio connec^¬ tion and a radio resource control connection with a serving base station of a radio access network of a cellular telecom- munication system and a core network connection with a core network of the cellular telecommunication system. The method further comprises receiving a comma d to reduce radio connec^¬ tivity of the bearer service from the serving base station . -

Δ b

and, in response to the received command, storing context pa^¬ rameters of the radio connection in a memory, adopting at. least some idle state procedures without releasing the whole bearer service, and initializing a procedure for delayed re- lease of the whole bearer service. The procedure for the de^¬ layed release comprises: tracking, by the terminal device, mobility of the terminal device with respect to a cell where the terminal device previously was registered in the radio access network during the procedure for delayed release of the whole bearer service, and requesting transfer of the stored context parameters to another base station upon detecting sufficient mobility in terms of relative distance with respect to the cell where the terminal device previously was registered in the radio access network during the proce- dure for delayed release of the whole bearer service.

In an embodiment, the method further comprises re^¬ storing the radio connection by using the stored context pa^¬ rameters of the radio connection.

In an embodiment, the at least some idle state procedures comprise idle state cell selection.

In an embodiment, the method further comprises : after a de^¬ termined number of cell selections caused by the mobility of the terminal device during the procedure for the delayed re^¬ lease of the bearer service, transmitting a context reloca- tion message to the radio access network, thereby requesting transfer of the context parameters of the radio connection to the currently selected base station.

In an embodiment, the method further comprises : tracking the number of cell selections that the terminal device has made without communicating with the radio access network during the procedure for the delayed release of the bearer service and, in response to the determined number of cell selection without communication with the radio access network, releas^¬ ing the whole bearer service.

When counting the number of said cell selections, an embodi^¬ ment excludes from the counting of the number of cell selec^¬ tions at least one cell selection during the procedure for delayed release of the bearer service in response to reselec- tion, during the procedure for the delayed release of the bearer service, of a cell that has been previously selected, or connected to by the terminal device. In other words, the previous selection may be carried out during the procedure for the delayed release of the bearer service or before ini^¬ tiating the procedure, and the rese lection is car ied out during the procedure for the delayed release of the bearer service .

An embodiment provides an apparatus comprising at least one processor and at least one memory including a computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to: cause a base station of a radio access network of a cellular telecommunication system to provide a bearer service between a terminal device and a core network through the base station, wherein the bearer service comprises a radio connection between the base station and the terminal device and a core network connection between the base station and the core network; determine that data trans^¬ fer activity of the bearer service is low, and, in response to the determination of low data transfer activity, to store context, parameters of the radio connection, cause the base station to release radio resources of the radio connection while maintaining the core network connection, and to initialize a procedure for delayed release of the whole bearer service, wherein the apparatus is in the procedure for the delayed release configured to start a timer in response to the release of the radio resources of the radio connection and, in response to expiry of the timer, to release the radio connection and. the core net.work connection,

Tn an embodiment, the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to release the radio con^¬ nection and the core network connection without any control signaling with the terminal device in response to the expiry of the timer.

An embodiment, provides an apparatus comprising at. least one processor and at. least one memory including- a computer pro- _{2 g}

gram code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to: cause a base station of a radio access network of a cellular telecommunication system to pro- vide a bearer service between a terminal device and a core network through the base station, wherein the bearer service comprises a radio connection between the base station and the terminal device and a core network connection between the base station and the core network; determine that data trans- fer activity of the bearer service is low, and, in response to the determination of low data transfer activity, to store context parameters of the radio connection, cause the base station to release radio resources of the radio connection while maintaining the core network connection, and to ini- tialize a procedure for delayed release of the whole bearer service, wherein the apparatus is in the procedure for the delayed release configured to utilize at least some of the same mobility procedures as in an idle state for the terminal, device associated with said bearer service, and to transfer the stored context parameters to another base station accord^¬ ing to the mobility of the terminal device in terms of rela^¬ tive distance with respect to the cell during the procedure for delayed release of the whole bearer service.

In an embodiment, the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to restore the radio con^¬ nection by using the stored context parameters of the radio connection upon detection of increased data transfer activity in the bearer service. In an embodiment, the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to determine, in response to the restoration of the radio connection, whether or not to reroute the core network connection on the basis of at least one of: mobility of the terminal device and a degree of the detected data transfer activity, and to cause rerouting of the core network connection upon determining of high data transfer activity and/or high mobility of the ter- mirial device after the radio resources of the radio connec^¬ tion were released.

In an embodiment, the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to: receive context parameters of an^¬ other terminal device during said procedure for the delayed release of the bearer service of said other terminal device and, in connection with the transfer of the context parame^¬ ters, reconfigure at least some of the context parameters and cause transmission of at least some of the reconfigured con^¬ text parameters to said other terminal device associated with the transferred context parameters in a single reconfiguration message. Said transfer of the context parameters may be triggered through a random, access procedure between said base station and said other terminal device, and the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to transmit the reconfiguration message as ciphered and/or as integrity protected before a contention is resolved within said random access procedure .

In an embodiment, during the procedure for the delayed re^¬ lease and upon detection of increased downlink data transfer activity in the bearer service, the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to: page the terminal device in a cell co trolled by said base station; and cause transmission of a paging request related to said terminal de^¬ vice at least to the other base station.

In an embodiment, the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to receive from a mobility management entity of said core network a paging identif1ΘΓ Of the termi^¬ nal device; and initiate a paging procedure in the base sta^¬ tion without involving the mobility management entity in the paging procedure.

An embodiment provides an apparatus comprising at least, one processor and at least one memory including a com^¬ puter program code, wherein the at least one memory and the _Q

computer program code are configured, with the at least one processor, to cause the apparatus to: cause a terminal device to provide a bearer service comprising radio connection and a radio resource control connection with a serving base station of a radio access network of a cellular telecommunication system, and a core network, connection with a core network of the cellular telecommunication system; receive a command to reduce radio connectivity of the bearer service from the serving base station; and in response to the received com- mand, store context parameters of the radio connection in a memory,, adopt at least some of idle state procedures without releasing the whole bearer service, and initialize a proce^¬ dure for delayed release of the whole bearer service, wherein the apparatus is in the procedure for the delayed release configured to start a timer in response to the received com^¬ mand and, in response to expiry of the timer, to release the bearer service and to enter an idle state.

In an embodiment, the at least, one memory and the computer program code are configured, with the at least, one processor, to cause the apparatus to release, in response to the expiry of the timer, the bearer service without any con^¬ t ol signaling with the base station.

An embodiment provides an apparatus comprising at least one processor; and at least one memory including a com- puter program code, wherein the at least one memory and the computer program code are configured, with the at. least one processor, to cause the apparatus to: cause a terminal device to provide a bearer service comprising radio connection and a radio resource control connection with a serving base station of a. radio access network of a cellular telecommu ication system and a core network connection with a core network of the cellular telecommunication system; receive a command to reduce radio connectivity of the bearer service from the serving base station; and in response to the received com- mand, store context parameters of the radio connection in a memory, adopt at least some of idle state procedures without releasing the whole bearer service, and initialize a proce^¬ dure for delayed release of the whole bearer service, wherein the apparatus is in the procedure for the delayed release configured to: track mobility of the terminal device with re^¬ spect to a cell where the terminal device previously was reg^¬ istered in the radio access network during the procedure for delayed release of the whole bearer service; and request transfer of the stored context parameters to another base station upon detecting sufficient mobility in terms of rela^¬ tive distance with respect to the cell where the terminal de^¬ vice previously was registered in the radio access network during the procedure for delayed release of the whole bearer service .

In an embodiment, the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to restore the radio con^¬ nection by using- the stored context parameters of the radio connection .

In an embodiment, the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to transmit, after a deter^¬ mined number of cell selections caused by the mobility of the terminal device during the procedure for the delayed release of the bearer service, a context relocation message to the radio access network, thereby requesting transfer of the context parameters of the radio connection to the currently se^¬ lected base station.

In an embodiment, the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to track the number of cell selections that the terminal device has made without communi^¬ cating with the radio access network during the procedure for the delayed release of the bearer service and, in response to the determined number of cell selections without communica^¬ tion with the radio access network, to release the whole bearer service.

When counting the cell selections, the at least, one memory and the computer program code are configured, with the ^

at least one processor, to cause the apparatus to exclude from the counting of the number of cell selections at least, one cell selection during the procedure for delayed release of the bearer service in response to reselection, during the procedure for the delayed release of the bearer service, of a cell that has been previously selected or connected to by the terminal device .

An embodiment provides an apparatus, comprising means for carrying out any one of the above -'described methods, proc- esses, or functionalities for reducing radio connectivity in the radio access network. An embodiment of such means is a processor (or a combination of processors) configured by one or more computer program modules.

An embodiment provides computer program product, embodied on a distribution medium readable by a computer and comprising program instructions which, when loaded into an apparatus, execute any one of the above-described methods, processes, or functionalities for reducing radio connectivity in the radio access network.

The present invention is applicable to the cellular or mobile telecommunication systems defined above but also to other suitable telecommunication systems. The protocols used, the specifications of mobile telecommunication systems, their network elements and subscriber terminals, develop rapidly. Such development may require extra changes to the described embodiments. Therefore, all words and expressions should be interpreted broadly and they are intended to illustrate, not to restrict, the embodiment. It will be obvious to a person skilled in the art that, as technology advances, the inven- five concept can be implemented in various ways. The inven^¬ tion and its embodiments are not limited to the examples de^¬ scribed above but may vary within the scope of the claims.

Claims

Patent claims

1. A method, comprising:

providing, in a base station apparatus of a radio access network of a cellular telecommunication system, a bearer service between a terminal device and a core network, through the base station, wherein the bearer service comprises a radio connection between the base station and the terminal device and a core network connection between the base station and the core network;

determining that data transfer activity of the bearer service is low; and

in response to the determination of low data transfer activity, storing context parameters of the radio con ection, releasing- radio resources of the radio connection while main^¬ taining the core network connection, and initializing a procedure for delayed release of the whole bearer service , the procedure for the delayed release comprising:

starting a timer in response to the release of the radio resources of the radio connection; and

in response to expiry of the timer, releasing the radio connection and. the core net.work connection.

2. The method of claim 1, wherein the release in re^¬ sponse to the expir of the timer is carried out without any control signaling with the terminal device,

3. A method, comprising:

providing, in a base station apparatus of a radio access network of a cellular telecommunication system, a bearer ser- vice between a terminal device and a core network, through the base station, wherein the bearer service comprises a radio connection between the base station and the terminal device and a core network connection between the base station and the core network;

determining that data transfer activity of the bearer service is low; and

in response to the determination of low data transfer activity, storing context parameters of the radio connection, releasing radio resources of the radio connection while main^¬ tai ing the core network connection, and initializing a procedure for delayed release of the whole bearer service, the procedure for the delayed release comprising:

utilizing at least some of the same mobility procedures as in an idle state for the terminal device associated with said bearer service; and

transferring the stored context parameters to another base station according to the mobility of the terminal device in terms of relative distance with respect to the cell during the procedure for delayed release of the whole bearer ser^¬ vice .

4. The methoo' of any preceding claim 1 to 3, further comprising: upon detection of increased data transfer activ- ity in the bearer service, restoring the radio connection by using the stored context parameters of the radio connection.

5. The method of claim 4, further comprising:

in response to the restoration of the radio connection, determining- whether or not to reroute the core network con- nection on the basis of at least one of: mobility of the terminal device, and a degree of the detected data transfer act. ivit.y; and

rerouting the core network connection upon determining- high data transfer activity and/or high mobility of the ter- minal device after the radio resources of the radio connec^¬ tion we e released.

6. The method of any preceding claim 3 to 5, further comprising :

receiving context parameters of another terminal device during said procedure for the delayed release of the bearer service of said other terminal device; and

in connection with the transfer of the context parameters bearer service _f reconfiguring at least some of the con^¬ text parameters and causing transmission of at least some of the reconfigured context parameters to said other terminal device associated with the transferred context parameters in a single reconfiguration message

7. The method of claim 6, wherein said transfer of the context parameters is triggered through a random, access pro^¬ cedure between said base station and said other terminal de^¬ vice, and wherein the reconfiguration message is transmitted as ciphered and/or as integrity protected before a contention is resolved within said random, access procedure.

8. The method of any preceding claim, further comprising during the procedure for the delayed release and upon de^¬ tection of increased downlink data transfer activity in the bearer service :

paging the terminal device in a cell controlled by said base station; and

transmitting a paging request related to said terminal device at least, to the other base station.

9. The method of any preceding claim, further comprising :

receiving from a mobility management entity of said core network, a paging identifier of the terminal device; and

initiating a paging procedure in the base station with- out involving the mobility management entity in the paging procedure .

10. A method, comprising:

providing, in a terminal device, a bearer service com^¬ prising a radio connection and a radio resource control con- nection with a serving base station of a radio access network of a cellular telecommunication system, and a core netwo k connection with a. core network of the cellular telecommunication system;

receiving a command to reduce radio connectivity of the bearer service from the serving base station; and

i response to the received command, stori g- context pa^¬ rameters of the radio connection in a memory, adopting at least some idle state procedures without releasing the whole bearer service, and initializing a procedure for delayed re- lease of the whole bearer service, the procedure for the de^¬ layed release comprising:

starting a ti er in response to the release of the radio resources of the radio connection; and. in response to expiry of the timer, releasing the whole bearer service and entering an idle state.

11. The method of claim 10, wherein the release of the bearer service in response to the reception of the command to release the radio resources is carried out without any con^¬ trol signaling with the base station,

12. A method, comprising:

providing, in a terminal device, a bearer service com^¬ prising a radio connection and a radio resource control con- nection with a serving base station of a radio access network of a cellular telecommunication system and a core network connection with a core network of the cellular telecommunication system;

receiving a command to reduce radio con ectivity of the bearer service from the serving base station; and

in response to the received command, storing context pa^¬ rameters of the radio CΟΠΠΘction in a memory, adopting at least, some idle state procedures without releasing the whole bearer service, and initializing a procedure for delayed re- lease of the whole bearer service, the procedure for the de^¬ layed release comprising:

tracking, by the terminal device, mobility of the termi^¬ nal device with respect to a cell where the terminal device previously was registered in the radio access network during the procedure for delayed release of the whole bearer ser^¬ vice; and

requesting transfer of the stored context parameters to another base station upon detecting sufficient mobility in terms of relative distance with respect to the cell where the terminal device previously was registered in the radio access network during the procedure for delayed release of the whole bearer service.

13. The method of any preceding claim 10 to 12, further comprising restoring the radio connection by using the stored context parameters of the radio connection.

14. The method of claim 12 or 13, wherein the at least some idle state procedures comprise idle state cell selec^¬ tion ,

15. The method of any preceding claim 10 to 14, further comprising :

after a determined number of cell selections caused by the mobility of the terminal device during the procedure for the delayed release of the bearer service, transmitting a context, relocation message to the radio access network, thereby requesting transfer of the context parameters of the radio connection to the currently selected base station.

16. The method of any preceding claim 10 to 15, further comprising :

tracking the number of cell selections that the terminal device has made without communicating with the radio access network during the procedure for the delayed release of the bearer service ; and

in response to the determined number of ceil selection without communication with the radio access network, releas^¬ ing the whole bearer service.

17. The method of claim 15 or 16, further comprising: when counting the number of said cell selections, excluding from the counting of the number of cell selections at least one cell selection during the procedure for delayed release of the bearer service in response to reselection, during the procedure for the delayed release of the bearer service, of a cell that has been previously selected or connected to by the terminal device.

18 , An apparatus compris ing :

at least one processor; and

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

cause a base station of a radio access network of a cel^¬ lular telecommunication system to provide a bearer service between a terminal device and a core network through the base station, wherein the bearer service comprises a radio connec^¬ tion between the base station and the terminal device and a core network connection between the base station and the core network; determine that data transfer activity of the bearer ser^¬ vice is low; and

in response to the determination of low data transfer activity, to store context parameters of the radio connec- tion, cause the base station to release radio resources of the radio connection while maintaining the core network connection, and to initialize a procedure for delayed release of the whole bearer service, wherein the apparatus is in the procedure for the delayed release configured to start a timer i response to the relea.se of the radio resources of the ra^¬ dio connection and, in response to expiry of the timer, to release the radio connection and the core network connection.

19, The apparatus of claim 18, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to release the radio connection and the core network connection without any control signaling with the terminal device in response to the expiry of the timer.

20, An apparatus comprising:

at least one processor; and

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

cause a base station of a radio access network of a cel^¬ lular telecommunication system to provide a. bearer service between a terminal device and a core network through the base station, wherein the bearer service comprises a radio connec^¬ tion between the base station and the terminal device and a core network connection between the base station and the core network;

determine that data transfer activity of the bearer ser^¬ vice is low; and

in response to the determination of low data transfer activity, to store context parameters of the radio connec^¬ tion, cause the base station to release radio resources of the radio connection while maintaining the core network, connection, and to initialize a procedure for delayed, release of the whole bearer service, wherein the apparatus is in the procedure for the delayed release configured to utilize at least some of the same mobility procedures as in an idle state for the terminal device associated with said bearer service, and to transfer the stored context parameters to an^¬ other base station according to the mobility of the terminal device in terms of relative distance with respect to the cell during the procedure for delayed release of the whole bearer service .

21. The apparatus of any preceding claim 18 to 20, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to restore the radio connection by using the stored context, parameters of the radio connection upon detection of increased data transfer activity in the bearer service.

22. The apparatus of claim 21, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to determine, in response to the restoration of the radio connection, whether or not to reroute the core network connection on the basis of at least one of: mobility of the terminal device and a degree of the detected data transfer activity, and to cause rerouting of the core network connection upon determining of high data transfer activity and/or high mobility of the ter^¬ minal device after the radio resources of the radio connec^¬ tion were released.

23. The apparatus of any preceding claim 20 to 22, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to:

receive context parameters of another terminal device during said procedure for the delayed release of the bearer service of said other terminal device; and

in connection with the transfer of the context parame^¬ ters, reconfigure at least some of the context parameters and cause transmission of at least some of the reconfigured con^¬ text parameters to said other terminal device associated with the transferred context parameters in a single reconfigura^¬ tion message,

24, The apparatus of claim 23, wherein said transfer of the context parameters is triggered through a random access procedure between said base station and said other terminal device, and wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to transmit the reconfiguration mes^¬ sage as ciphered and/or as integrity protected before a con^¬ tention is resolved within said random access procedure.

25, The apparatus of any preceding claim 18 to 24, wherein, during the procedure for the delayed release and upon detection of increased downlink data transfer activity in the bearer service, the at least, one memory and the com^¬ puter program code are configured, with the at least one processor, to cause the apparatus to:

page the terminal device in a cell controlled by said base stat ion ; and

cause transmission of a paging request related to said terminal device at least to the other base station,

26, The apparatus of any preceding claim 18 to 25, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to:

receive from a mobility management entity of said core network, a paging identifier of the terminal device; and

initiate a paging- procedure in the base station without involving the mobility management entity in the paging proce^¬ dure ,

27, The apparatus of any preceding claim 18 to 26, wherein the apparatus comprises said base station.

28, An apparatus comprising:

at least one processor; and

at least one memory including a computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to: H 1

cause a terminal device to provide a bearer service com^¬ prising radio connection and a radio resource control connec^¬ tion with a serving- base station of a radio access network of a cellular telecommunica ion system and a core network con- nection with a core network of the cellular telecommunication system;

receive a command to reduce radio connectivity of the bearer service from the serving base station; and

in response to the received command, store context pa- rameters of the radio connection in a memory, adopt at least, some of idle state procedures without releasing the whole bearer service, and initialize a procedure for delayed re^¬ lease of the whole bearer service, wherein the apparatus is in the procedure for the delayed release configured to start a timer in response to the received command and, in response to expiry of the timer, to release the bearer service and to enter an idle state.

29, The apparatus of claim 28, wherein the at least, one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to release, in response to the expiry of the timer, the bearer service with^¬ out, a y control signaling with the base station.

30. An apparatus comprising:

at least one processor; and

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

cause a terminal device to provide a bearer service com- prising radio con ection and a radio resource control con ec^¬ tion with a serving base station of a radio access network of a cellular telecommunication system and a core network con^¬ nection with a core network of the cellular telecommunication system;

in response to the received command, store context pa^¬ rameters of the radio connection in a memory, adopt at least some of idle state procedures without releasing the whole bearer service, and initialize a procedure for delayed re^¬ lease of the whole bearer service, wherein the apparatus is in the procedure for the delayed release configured to:

track mobility of the terminal device with respect to a cell where the terminal device previously was registered, in the radio access network during the procedure for delayed re^¬ lease of the whole bearer service; and

request transfer of the stored context parameters to an^¬ other base station upon detecting sufficient mobility in terms of relative distance with respect to the cell where the terminal device previously was registered in the radio access network during the procedure for delayed release of the whole bearer service,

31. The apparatus of any preceding claim 28 to 30, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to restore the radio connection by using the stored context parameters of the radio connection.

32. The apparatus of claim 30 or 31, wherein the at least some idle state procedures comprise idle state cell se^¬ lection .

33. The apparatus of any preceding claim 28 to 32, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to transmit, after a determined number of cell se^¬ lections caused by the mobility of the terminal device during the procedure for the delayed release of the bearer service, a context relocation message to the radio access network, thereby requesting transfer of the context parameters of the radio connection to the currently selected base station.

34. The apparatus of any preceding claim 28 to 33, wherein the at least one memory and the computer program code are configured, ith the at least one processor, to cause the apparatus to track the number of cell selections that the terminal device has made without communicating with the radio access network during the procedure for the delayed release of the bearer service and, in response to the determined num- ber of cell selections without communication with the radio access network, to release the whole bearer service.

35. The apparatus of claim 33 or 34, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to exclude from the counting of the number of cell selections at least one cell selection during the procedure for delayed release of the bearer service in response to reselection, during the procedure for the delayed release of the bearer service, of a cell that has been previously selected or con^¬ nected to by the terminal device,

36. The apparatus of any preceding claim 28 to 35, wherein the apparatus comprises said terminal device,

37, An apparatus, comprising means for carrying out the method according to any preceding- claim 1 to 17.

38, A computer program product embodied on a distribu^¬ tion medium readable by a computer and comprising program instructions which, when loaded into an apparatus, execute the method according to any preceding claim 1 to 17.