WO2016029938A1

WO2016029938A1 - Method, apparatus and computer program for switching from multicast - to unicast mode

Info

Publication number: WO2016029938A1
Application number: PCT/EP2014/068162
Authority: WO
Inventors: Mikko Saily; Henri Markus Koskinen
Original assignee: Nokia Solutions And Networks Oy
Priority date: 2014-08-27
Filing date: 2014-08-27
Publication date: 2016-03-03

Abstract

A method comprising: determining, at a user equipment, whether to switch from a first reception mode of operation to a second reception mode of operation; wherein the determination is made in dependence upon information; and wherein the information comprises at least one of a connection state of said user equipment and a mobility state of said user equipment.

Description

DESCRIPTION

METHOD, APPARATUS AND COMPUTER PROGRAM FOR SWITCHING

FROM MULTICAST - TO UNICAST MODE The present invention relates to methods, apparatus and computer programs for switching between communication modes.

Background A communication system can be seen as a facility that enables communication sessions between two or more entities such as fixed or mobile communication devices, base stations, servers and/or other communication nodes. A communication system and compatible communicating entities 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. For example, the standards, specifications and related protocols can define the manner how various aspects of communication shall be implemented between communicating devices. A communication can be carried on wired or wireless carriers. In a wireless communication system at least a part of communications between stations occurs over a wireless link.

Examples of wireless systems include public land mobile networks (PLMN) such as cellular networks, satellite based communication systems and different wireless local networks, for example wireless local area networks (WLAN). A wireless system can be divided into cells or other radio coverage or service areas. A radio service area is provided by a station. Radio service areas can overlap, and thus a communication device in an area can typically send signals to and receive signals from more than one station. A user can access the communication system by means of an appropriate communication device. A communication device of a user is often referred to as user equipment (UE) or terminal. A communication device is provided with an appropriate signal receiving and transmitting arrangement for enabling communications with other parties. Typically a communication device is used for enabling receiving and transmission of communications such as speech and data. In wireless systems a communication device provides a transceiver station that can communicate with another communication device such as e.g. a base station and/or another user equipment. The communication device may access a carrier provided by a station, for example a base station, and transmit and/or receive communications on the carrier.

Long Term Evolution (LTE) is a mobile telecommunication standard being developed by the 3^rd Generation Partnership Project (3GPP). LTE aims to improve system capacity and performance.

Summary According to a first aspect there is provided a method comprising: determining, at a user equipment, whether to switch from a first reception mode of operation to a second reception mode of operation; wherein the determination is made in dependence upon information; and wherein the information comprises at least one of a connection state of said user equipment and a mobility state of said user equipment.

According to some embodiments, said first reception mode of operation comprises a multicast reception mode, and said second reception mode of operation comprises a unicast reception mode.

According to some embodiments, said connection state of said user equipment comprises one of a connected state and an idle state.

According to some embodiments, said mobility state comprises a speed of movement of said user equipment.

According to some embodiments, said information comprises network measurements. According to some embodiments, said network measurements comprise at least one of reference signal received quality and block error rate. According to some embodiments, said information comprises information of the proximity of said user equipment to a cell boundary.

According to some embodiments, at least some of said information is received from a network node.

According to some embodiments, said information received from said network node comprises at least one trigger condition.

According to some embodiments, said determining whether to switch comprises determining a time to switch from said first reception mode of operation to said second reception mode of operation.

According to some embodiments, the method comprises sending a request to switch from said first reception mode of operation to said second reception mode of operation.

According to some embodiments, said user equipment is in a mission-critical group communication. According to a second aspect there is provided a computer program comprising computer executable instructions which when run on one or more processors perform the method of the first aspect.

According to a third aspect there is provided an apparatus comprising at least one processor; and at least one memory including 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: determine whether to switch from a first reception mode of operation to a second reception mode of operation; wherein the determination is made in dependence upon information; and wherein the information comprises at least one of a connection state of said apparatus and a mobility state of said apparatus. According to some embodiments, said first reception mode of operation comprises a multicast reception mode, and said second reception mode of operation comprises a unicast reception mode.

According to some embodiments, said connection state of said apparatus comprises one of a connected state and an idle state.

According to some embodiments, said mobility state comprises a speed of movement of said apparatus. According to some embodiments, said information comprises network measurements.

According to some embodiments, said network measurements comprise at least one of reference signal received quality and block error rate.

According to some embodiments, said information comprises information of the proximity of said apparatus to a cell boundary.

According to some embodiments, the apparatus is configured to receive at least some of said information from a network node.

According to some embodiments, said information received from said network node comprises at least one trigger condition. According to some embodiments, said determining whether to switch comprises determining a time to switch from said first reception mode of operation to said second reception mode of operation. According to some embodiments, the apparatus is configured to send a request to switch from said first reception mode of operation to said second reception mode of operation. According to some embodiments, said apparatus is in a mission-critical group communication.

According to some embodiments, said apparatus comprises a user equipment. In a fourth aspect there is provided an apparatus comprising means for determining whether to switch from a first reception mode of operation to a second reception mode of operation; wherein the determination is made in dependence upon information; and wherein the information comprises at least one of a connection state of said apparatus and a mobility state of said apparatus.

According to some embodiments, said first reception mode of operation comprises a multicast reception mode, and said second reception mode of operation comprises a unicast reception mode. According to some embodiments, said connection state of said apparatus comprises one of a connected state and an idle state.

According to some embodiments, said mobility state comprises a speed of movement of said apparatus.

According to some embodiments, said information comprises network measurements.

According to some embodiments, said information comprises information of the proximity of said apparatus to a cell boundary. According to some embodiments, said apparatus comprises means for receiving at least some of said information from a network node. According to some embodiments, said information received from said network node comprises at least one trigger condition.

According to some embodiments, the apparatus comprises means for sending a request to switch from said first reception mode of operation to said second reception mode of operation.

According to some embodiments, said apparatus is in a mission-critical group communication.

According to some embodiments, said apparatus comprises a user equipment.

According to a fifth aspect there is provided a method comprising: transmitting information, said information comprising criteria for use by a user equipment in determining whether to switch from a first reception mode of operation to a second reception mode of operation; and wherein said criteria is configured to be dependent upon at least one of a connection state and a mobility state of said user equipment.

According to some embodiments, said criteria comprises at least one of: reference signal received quality; block error rate; mobility information of said user equipment; proximity to a cell boundary. According to some embodiments, said information comprises threshold values for said criteria. According to some embodiments, the method comprises receiving a request from said user equipment to switch from said first reception mode of operation to said second reception mode of operation.

According to some embodiments the method comprises sending information comprising switching criteria to a plurality of user equipment.

According to some embodiments the method comprises sending different switching criteria to at least some of said plurality of user equipment. According to some embodiments said criteria comprises at least one trigger condition.

In a sixth aspect there is provided a computer program comprising computer executable instructions which when run on one or more processors perform the method of the fifth aspect.

In a seventh aspect there is provided an apparatus comprising: at least one processor;

and at least one memory including 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: transmit information, said information comprising criteria for use by a user equipment in determining whether to switch from a first reception mode of operation to a second reception mode of operation; and wherein said criteria is configured to be dependent upon at least one of a connection state and a mobility state of said user equipment. According to some embodiments, said first reception mode of operation comprises a multicast reception mode, and said second reception mode of operation comprises a unicast reception mode. According to some embodiments, said criteria comprises at least one of: reference signal received quality; block error rate; mobility information of said user equipment; proximity to a cell boundary.

According to some embodiments, said information comprises threshold values for said criteria.

According to some embodiments, the apparatus is configured to receive a request from said user equipment to switch from said first reception mode of operation to said second reception mode of operation.

According to some embodiments the apparatus is configured to send information comprising switching criteria to a plurality of user equipment.

According to some embodiments the apparatus is configured to send different switching criteria to at least some of said plurality of user equipment.

According to some embodiments said criteria comprises at least one trigger condition. According to an eighth aspect there is provided an apparatus comprising means for transmitting information, said information comprising criteria for use by a user equipment in determining whether to switch from a first reception mode of operation to a second reception mode of operation; and wherein said criteria is configured to be dependent upon at least one of a connection state and a mobility state of said user equipment. According to some embodiments, said first reception mode of operation comprises a multicast reception mode, and said second reception mode of operation comprises a unicast reception mode. According to some embodiments, said criteria comprises at least one of: reference signal received quality; block error rate; mobility information of said user equipment; proximity to a cell boundary.

According to some embodiments, the apparatus comprises means for receiving a request from said user equipment to switch from said first reception mode of operation to said second reception mode of operation.

According to some embodiments the apparatus comprises means for sending information comprising switching criteria to a plurality of user equipment.

According to some embodiments the apparatus comprises means for sending different switching criteria to at least some of said plurality of user equipment.

According to some embodiments said criteria comprises at least one trigger condition. Brief description of drawings

Some embodiments will now be explained with reference to the appended Figures in which: Figure 1 shows a schematic diagram of a network according to some embodiments;

Figure 2 shows a schematic diagram of a mobile communication device according to some embodiments; Figure 3 shows a schematic diagram of a control apparatus according to some embodiments;

Figure 4 is a flow chart according to an embodiment;

Figure 5 is a signalling diagram according to an embodiment.

Description of some embodiments

In the following certain exemplifying embodiments are explained with reference to a wireless or mobile communication system serving mobile communication devices. Before explaining in detail the exemplifying embodiments, 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 mobile communication devices or user equipments (UE) 1 02, 103, 105 are provided wireless access via at least one base station or similar wireless transmitting and/or receiving node or point. In the Figure 1 example two overlapping access systems or radio service areas of a cellular system 100 and 1 10 and three smaller radio service areas 1 15, 1 17 and 1 1 9 provided by base stations 106, 107, 1 16, 1 18 and 1 20 are shown. Each mobile communication device and station may have one or more radio channels open at the same time and may send signals to and/or receive signals from more than one source. It is noted that the radio service area borders or edges are schematically shown for illustration purposes only in Figure 1 . It shall also be understood that the sizes and shapes of radio service areas may vary considerably from the shapes of Figure 1 . A base station site can provide one or more cells. A base station can also provide a plurality of sectors, for example three radio sectors, each sector providing a cell or a subarea of a cell. All sectors within a cell can be served by the same base station. 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. In Figure 1 control apparatus 108 and 109 is shown to control the respective macro level base stations 106 and 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. The control apparatus 108 may be part of the base station or it may be physically separate from the base station. The control apparatus 1 08 may serve a plurality of macro and/or pico cells. The control apparatus may for example be a radio network controller (RNC).

In Figure 1 stations 106 and 107 are shown as connected to a wider communications network 1 1 3 via gateway 1 12. Gateway 1 12 may for example be a Gateway General Packet Radio Service Support Node (GGSN). A further gateway function may be provided to connect to another network. The smaller stations 1 16, 1 18 and 120 can also be connected to the network 1 1 3, for example by a separate gateway function and/or via the controllers of the macro level stations. In the example, stations 1 1 6 and 1 18 are connected via a gateway 1 1 1 whilst station 1 20 connects via the controller apparatus 108. Gateway 1 1 1 may for example be a Serving General Packet Radio Service Support Node (SGSN).

A possible mobile communication device for transmitting and retransmitting information blocks towards the stations of the system will now be described in more detail in 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 include a mobile station (MS) 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, personal data assistant (PDA) 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 include 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 include downloads, television and radio programs, videos, advertisements, various alerts and other information. The mobile device 200 may receive signals over an air 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. The apparatus 200 comprises a radio frequency (RF) unit for wireless communication. The RF unit may comprise, for example, the transceiver apparatus 206 and an appropriate power amplifier (PA).

A wireless communication device can be provided with a Multiple Input / Multiple Output (MIMO) antenna system. MIMO arrangements as such are known. MIMO systems use multiple antennas at the transmitter and receiver along with advanced digital signal processing to improve link quality and capacity. Although not shown in Figures 1 and 2, multiple antennas can be provided, for example at base stations and mobile stations, and the transceiver apparatus 206 of Figure 2 can provide a plurality of antenna ports. More data can be received and/or sent where there are more antenna elements. A station may comprise an array of multiple antennas. Signalling and muting patterns can be associated with Tx antenna numbers or port numbers of MIMO arrangements. A mobile device is also 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 it 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.

Figure 3 shows an example of a control apparatus for a communication system, for example to be coupled to and/or for controlling a station of an access system, such as a base station. In some embodiments base stations comprise a separate control apparatus. In other embodiments the control apparatus can be another network element. The control apparatus 300 can be arranged to provide control on communications in the service area of the system. The control apparatus 300 can be configured to provide control functions in association with generation and communication of request and instructions in view of reception of information blocks, retransmissions and other related information by means of the data processing facility in accordance with certain embodiments described below. For this purpose 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 control apparatus 300 can be configured to execute an appropriate software code to provide the control functions. It shall be appreciated that similar components can be provided in a control apparatus provided elsewhere in the system for controlling reception of sufficient information for decoding of received information blocks. The communication devices 1 02, 103, 105 can access the communication system based on various access techniques, such as code division multiple access (CDMA), or wideband CDMA (WCDMA). Other examples include 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.

As discussed above, LTE is a wireless communication standard. There is on-going work in making LTE usable for "mission-critical" group communication for public- safety officials, such as the police. Group communication is a technical feature of public safety, wherein Communication from Transmitter Group Members is sent to Receiver Group Members.

One aspect considered herein is maintaining service continuity, for example where a UE transfers from a point-to-multipoint (p-t-m) communication to a unicast communication. More particularly, a standardized trigger is considered, for example based upon radio measurements, so that a UE (in idle and/or connected modes) can initiate a unicast bearer for downlink media reception prior to losing connection from a Multicast Broadcast Multimedia Service (MBMS) p-t-m transmission.

The trigger for sending the unicast request to the Group Communication System Enablers (GCSE) could be UE implementation specific, or be defined as part of the GCSE application in the UE. GCSE is a 3GPP feature enabling an application layer functionality to provide Group Communication over E-UTRAN. The trigger could be, for example, Reference Signal Received Quality (RSRQ), or Block Error Rate (BLER), or another indication such as a border indication indicating to a UE that it is approaching a cell border. These triggers could be used to assist a UE in transitioning to unicast communication at an appropriate point in time.

One proposal is to switch from MBMS to unicast based on the UE detection of degrading MBMS quality. The UE may request to receive the service over unicast when MBMS quality degrades below a threshold. The UE may identify the degrading MBMS quality based on e.g. RSRQ, BLER of the Packet Mode Channel Handler (PMCH). This may be a UE implementation specific threshold, or the Radio Access Network (RAN) could provide trigger criteria to the UE to assist the UE in requesting the unicast bearer for the service at an appropriate point in time. Furthermore, the network may assist the UE in establishing the unicast bearer for the service by providing indications of MBSFN area boundary or defined as part of the GCSE application in the UE.

To be appropriate for service continuity, the trigger needs to be fast enough to ensure that the unicast reception can be established before the broadcast reception eventually fails. A speed that is deemed fast enough can depend on the state of the UE; for example, a fast-moving UE will run out of the broadcast coverage range more quickly than a slow moving UE.

On the other hand, a too light or too fast trigger may lead to unnecessary switching away from broadcast reception, and therefore inefficient radio-resource usage, for example unnecessary signalling over the radio interface. Difficulties may also arise where there are no means available for adapting the trigger to UE RRC state and/or mobility.

According to some embodiments the RRC state of the UE is used as an attribute for determining how fast the trigger should be. The RRC state provides a suitable attribute for this functionality because it has been realised that the time it takes to request and establish unicast reception of the service takes less time if the UE is already in RRC_Connected state to begin with, compared with if the UE was receiving the MBMS broadcast in RRCJdle state.

In some embodiments, the responsiveness of the trigger to the UE mobility is additionally or alternatively taken into account. For example, the trigger event for requesting unicast reception may need to be faster when UE velocity increases, for example when the UE is in a moving vehicle. This is because the signal coverage of the MBSFN network area may degrade faster when UE velocity increases, thus mandating a faster trigger.

According to some embodiments the trigger conditions are signalled by the RAN (for example a Radio Network Controller (RNC) or base station) to a terminal device such as a UE which is requesting unicast delivery of a service that is being broadcast.

The trigger condition for the UE to apply may be determined by the RAN. In some embodiments the trigger condition for the UE to apply depends on whether the UE is in [RRCJIdle state or [RRC JConnected state. The RAN can obtain and use the UE state information to make the determination of which trigger condition to apply, and may then signal the trigger condition to the UE.

In some embodiments the trigger condition additionally or alternatively depends on mobility of the terminal, which information may be estimated/maintained by the terminal or the network. The RAN can obtain and use the mobility information to make the determination of which trigger condition to apply, and then signal the trigger condition to the UE.

In some embodiments, the signalling of the unicast delivery request triggers are comprised in the MBMS control information. According to some embodiments the MBMS control information is broadcast on a logical channel specific for MBMS common control information (MCCH). E-UTRA employs one MCCH logical channel per MBSFN area, and one MBSFN (Multi-Media Broadcast over a Single Frequency Network) area can transmit several multicast channel (MCH) channels, each using a different modulation and coding scheme (MCS), whose configurations are given in the MCCH message. The MTCH broadcasts traffic information for MBMS Traffic Channel. Several MTCH and one MCCH are multiplexed onto MCH by MAC layer. Accordingly, in some embodiments the unicast delivery request triggers can be configured per MCH, for each possible multiple MBSFN area that a given cell belongs to and/or transmits to. The content of the MCCH, being part of the MBSFN transmission, may be identical in all cells of an MBSFN area.

According to some embodiments cell-specific mobility triggers can be used. In such embodiments the implementation may be by modification of SystemlnformationBlockType 13, where the network can broadcast control information regarding the configuration of the trigger for requesting unicast delivery. Alternatively, SystemlnformationBlockType15 can be used, which contains the MBMS Service Area Identities of the current and/ or neighboring carrier frequencies. According to some embodiments a generic trigger event for unicast delivery request can be used. The trigger may comprise an event validity time (e.g. similar to TimeToTrigger (TTT)). The trigger may also comprise a threshold indicating e.g. packet error rate, or signal quality or power, which could be measured as MBMS BLER, MBMS RSRP, MBMS RSRQ or MBMS RSSI. However it will be understood that the unicast delivery request trigger is not limited to these examples.

According to embodiments the unicast delivery request trigger factors can also be scaled using signalled parameters based on at least one of following options:

a) UE RRC state

b) Mobility state or status

For example where a UE using is UE RRC state (option (a) above) to adjust the unicast delivery request trigger, the UE can select and adjust the unicast delivery trigger event parameters based on a set of signalled values indicating which thresholds and/or validity times are used for RRC_Connected and RRCJdle state. Both RRC_Connected and RRCJdle state typically have their own mobility parameters as specified in 3GPP TS 36.331 and TS 36.304. In embodiments the values or set of values indicating the trigger thresholds can be adapted to radio conditions and network deployments.

In the case of a UE using Mobility State (option (b) above) to adjust the unicast delivery request trigger, in some embodiments the UE can adjust the unicast delivery trigger event parameters with scaling factors depending on the UE speed, e.g. mobility status or Mobility State. One possibility is to use the SpeedStateScale Factors, (e.g. [0.25, 0.50, 0.75, 1 .00]), which could in embodiments be also introduced as dedicated parameters to MBMS. In a similar manner to that used in 3GPP 36.331 , the UE may apply three different levels of mobility state and scale the unicast delivery request trigger for example with the following procedure:

1 > perform mobility state detection using the mobility state detection as specified in 3GPP TS 36.304 and TS 36.331 as follows: 2> counting handovers in RRC_Connected or cell reselections in RRCJdle state; 2> applying the parameter applicable for each RRC state as included in signalled MBMS control information;

1 > if high mobility state is detected:

2> use the trigger event value or factor for requesting unicast delivery modified by a value indicating high mobility;

1 > else if medium mobility state is detected:

2> use the trigger event value or factor for requesting unicast delivery modified by a value indicating medium mobility;

1 > else:

2> no scaling is applied;

It will of course be understood that in other embodiments fewer or more than three different mobility states may be provided.

In the case of a UE using both a RRC state and a Mobility state (options (a) and (b) above) to adjust the unicast delivery request trigger, in some embodiments the UE can select the signalled unicast delivery request factor for the given RRC state and then apply the scaling step based on the Mobility State.

It will be understood that other combinations of rules and reasoning of unicast delivery request can be used.

Figure 4 broadly describes a method according to some embodiments.

At step S1 a UE is operating in a point to multipoint p-t-m communication mode.

At step S2 a determination is made as to whether a trigger event has occurred that would cause the UE to transition to a unicast mode. In some embodiments the determination to change from a multicast mode to a unicast mode is made by the UE. If the determination is "no", then the UE continues to operate in p-t-m mode. If, on the other hand, the determination is "yes" then the method continues to step S3 where the UE transitions to unicast mode.

Figure 5 shows in more detail signalling between a UE 502 and a RAN node 504, according to an embodiment. The RAN node may, for example, be a RNC. Alternatively the RAN node may be a base station such as an eNB. Alternatively there may be a base station between the RAN node 504 and the UE 502, with the base station acting as an intermediary between the two.

At step S1 the UE is listening to an MBMS broadcast. The MBMS broadcast may be a mission-critical group call. At step S2 the RAN node 504 sends information to the UE 502. The information comprises criteria that the UE can use to determine whether and/or when to transition from an MBMS mode to a unicast mode. The criteria may comprise, for example, Reference Signal Received Quality (RSRQ), and/or Block Error Rate (BLER), or other indications such as a "border indication" comprising information regarding the proximity to a cell border. Other criteria may also be provided. In other embodiments step S2 may occur before step S1 . Also, in some embodiments the UE is pre-configured with such criteria, in which case step S2 may not be necessary.

The information sent from the RAN node may provide an indication to the UE of how the UE should behave in dependence on its connection state (e.g. CONNECTED or IDLE). For example the indication may provide information to the UE which causes the UE to behave differently depending on whether the UE is in an RRC_CONNECTED mode or an RRCJDLE mode. The connection state may be used by the UE in conjunction with measured cell conditions (e.g. RSRQ, BLER, distance from cell boundary etc.), to determine when to switch.

For example, the RAN may send an instruction along the lines of "when in RRC_CONNECTED state, switch from multicast to unicast when the RSRQ drops below value X", and/or "when in RRCJDLE state, switch from multicast to unicast when RSRQ drops below value Y", where X and Y are variables. According to this example, the value X may be less than the value Y. Although the example of RSRQ is given here, the same can be true of any other variable e.g. BLER, distance from cell boundary etc.

The information sent from the RAN node may also provide an indication to the UE of how the UE should behave in dependence on the mobility of the UE. For example the indication may provide information to the UE which causes the UE to behave differently depending on whether the UE is stationary or moving. This information may be used by the UE in conjunction with knowledge of its connection state (e.g. CONNECTED or IDLE).

For example, the RAN node may send an instruction along the lines of "when in RRC_CONNECTED state, switch from multicast to unicast when the speed of the UE goes above value X", and/or "when in RRCJDLE state, switch from multicast to unicast when the speed goes above value Y", where X and Y are variables. According to this example, the value X may be higher than the value Y. It will of course be appreciated that the UE can, in some examples, use knowledge of both the cell conditions and mobility state, and the trigger conditions indicated by the RAN node for both those aspects, in determining when to switch.

The information sent by the RAN node to the UE may also apply a weighting to one or more of the criteria e.g. the UE may be instructed to weigh cell conditions (e.g. RSRQ, BLER etc), and the trigger conditions associated with that aspect, more heavily than mobility state (e.g. speed of movement of UE), and the trigger conditions associated with that aspect, and vice versa. The information sent to the UE may have been determined by the RAN node. Alternatively the RAN node may receive the criteria from another network node before passing it on to the UE. The information (e.g. switching thresholds) sent by the RAN node may be sent as part of system information broadcasts (SIBs). The UE may receive the information on the SIBs when the UE is in the RRCJDLE state. When the UE is in the RRC_CONNECTED state, the UE may receive the information on dedicated signalling. Also, in another step (not shown), a request may be sent from the UE 502 to the RAN node 504 for the information. This may happen in response to a handover or changing network conditions, for example. Also, the UE 502 may send the RAN node 504 information regarding radio network conditions, which information the RAN node 504 can use when determining the criteria to be sent to the UE. For example, when a UE is in an RRC_CONNECTED state the UE may send broadcast related measurements to the network, which may indicate to the network that unicast delivery is needed/requested. This may be based on configuration(s) signalled by the network. When in RRCJDLE state the UE may not know if the UE is receiving broadcast services. Accordingly in the RRCJDLE state the UE may need to go through the initial RRC configuration. During both the CONNECTED and IDLE states the UE may scale (e.g. alter) the switching thresholds to faster trigger the request of the unicast service.

At step S3 the UE 502 stores the information sent by the RAN node to a memory of the UE. The RAN node 504 may also store the information sent to the UE (or to be subsequently sent to the UE), in a memory of the RAN node. The RAN node 504 may do this for each UE it is controlling.

At step S4 the UE is monitoring the radio conditions. At step S4 the UE 502 is also monitoring and is therefore aware of its connection state and/or its mobility. The UE may also be monitoring other information, such as radio network conditions and/or its proximity to a cell boundary. The UE can compare the "current" conditions to the information stored at step S3. At step S5 the UE makes a determination of whether to transition to the unicast mode from the MBMS mode, in dependence on a comparison between the criteria (e.g. trigger conditions as signalled by the RAN node) in the stored information and the current conditions. For example, the stored information may include information that the UE should switch from the multicast mode to the unicast mode when one or more of RSRQ, BLER, distance from cell boundary, speed of UE etc reach certain threshold values, as explained above. In this embodiment, at step S6 one or more of the trigger conditions is met and the UE 502 transitions to the unicast mode. The transition may in some embodiments comprise a request (not shown) which is sent to the RAN node requesting the unicast service. At step S7 the UE 502 sends to the RAN node 504 a message informing the RAN node of the transition to the unicast mode. The RAN node 504 may update its memory with this information.

Therefore, in addition to cell conditions, in embodiments the UE also takes in to account its connection state (e.g. CONNECTED or IDLE) and mobility state (e.g. stationary or moving), when determining if and/or when to transition from the multicast mode to the unicast mode. The UE may use this information in conjunction with the cell conditions when determining if and/or when to transition from the multicast mode to the unicast mode.

For example, the UE may change the speed and/or sensitivity of transition from multicast to unicast based on its connection state. The UE may determine that when in an IDLE state, it needs to initiate the transition more quickly than when in a CONNECTED state. This is because the transition from multicast to unicast may only be possible when the UE is in a CONNECTED state. Therefore the UE takes in to account the delay of moving from IDLE to CONNECTED state prior to the transition to unicast from multicast. If the UE is already in a CONNECTED state then the UE may determine that the speed and/or sensitivity to switching can be lessened somewhat, since the delay of moving from the IDLE to CONNECTED state does not have to be accounted for.

The UE may change the speed and/or sensitivity of transition from multicast to unicast based on its mobility state. The UE may determine that when moving (or moving quickly, or moving above a certain threshold speed), that it needs to initiate the transition to unicast mode more quickly than when stationary or moving slowly. This is because when moving quickly there may be a higher likelihood that the connection to the MBMS broadcast will be lost before the UE had a chance to switch to the unicast mode, for example because the UE has moved out of range or because the connection was lost during a cell handover. The UE may determine that when stationary (or moving slowly, or moving below a certain threshold speed), that the initiation of the transition to unicast mode can be made more slowly than if the UE is moving or moving quickly. This is because when stationary or moving slowly there may be a lower likelihood that the connection to the MBMS broadcast may be lost before the UE had a chance to switch to the unicast mode.

As explained above, these thresholds or trigger conditions can be signalled by the RAN node to the UE.

Accordingly some embodiments may provide trigger criteria for a UE to request unicast delivery of a service that is at the time being received over MBMS broadcasting, when leaving the coverage of the broadcast (or when it is predicted that coverage of the broadcast is going to be lost).

It will of course be understood that, although communication between a RAN node and a single UE has been described with respect to Figure 5 for the purposes of explanation, in other embodiments the RAN node may send information to more than one UE. In embodiments the RAN node can send different information (and therefore different switching criteria) to different UEs. Accordingly, in embodiments transition criteria (e.g. trigger conditions) can be tailored on a UE by UE basis, as opposed to all UEs operating according to the same criteria. Therefore some embodiments may assist in overcoming a situation where a single switching threshold cannot serve all users.

Some embodiments may minimise service interruption time when switching between a unicast state and a multicast state. Some embodiments may also avoid unnecessary signalling. For example the amount of signalling required may be relatively low due to the efficient transition mechanism. Some embodiments may also minimise a delay in switching from a multicast bearer to a unicast bearer.

Some embodiments may also improve support for various user profile requirements; for example the different requirements of stationary and moving cars.

Some embodiments may also mitigate or avoid premature or even unnecessary switching from broadcast reception to unicast reception, where radio resources may be unnecessarily spent on unicast delivery. Although the description has primarily discussed the switching of a user equipment from a muticast mode to a unicast mode, it will be understood that embodiments may also be applied to the reverse situation where a user equipment switches from a unicast mode to a multicast mode. It will also be appreciated that the embodiments may find utility with regard to mission-critical communication, for example the police or other emergency services, to ensure continuation of service where a broadcast service is to be dropped.

It should also be noted that whilst some embodiments may follow the Mobility State Estimation functionality described in 3GPP 36.304 and 36.331 , for RRCJdle and RRC_Connected states respectively, the embodiments are not limited to that.

In some embodiments other means of estimating UE mobility and applying this for configuration of the unicast request trigger can be used. For example GPS based measurement or network based UE mobility using S1 /X2 information element UE History Information IE can be used, when the UE is in RRC_Connected state. Additionally 3GPP Release 12 has specified 3GPP 36.304 CR in R2-141 019 and 36.331 CR in R2-141018, which introduce UE mobility history reporting for RRCJdle and RRC_Connected states respectively. In these cases the network can collect history information about mobility per UE and this information will be signalled between neighbouring eNBs as part of the S1 /X2 signalling. Therefore the network is able to configure the unicast delivery request trigger per UE in RRC Connected state. It will be appreciated that some embodiments may incorporate this functionality. An appropriately adapted computer program code product or products may be used for implementing the embodiments, when loaded on an appropriate data processing apparatus, for example for determining geographical boundary based operations and/or other control operations. The program code product for providing the operation may be stored on, provided and embodied by means of an appropriate carrier medium. An appropriate computer program can be embodied on a computer readable record medium. A possibility is to download the program code product via a data network. In general, the various embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Embodiments of the inventions may thus be practiced in various components such as integrated circuit modules. The design of integrated circuits is by and large a highly automated process. 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. It is also noted herein that while the above describes exemplifying embodiments of the invention, there are several variations and modifications which may be made to the disclosed solution without departing from the scope of the present invention.

Claims

1 . A method comprising:

determining, at a user equipment, whether to switch from a first reception mode of operation to a second reception mode of operation;

wherein the determination is made in dependence upon information; and wherein the information comprises at least one of a connection state of said user equipment and a mobility state of said user equipment.

2. A method as set forth in claim 1 , wherein said first reception mode of operation comprises a multicast reception mode, and said second reception mode of operation comprises a unicast reception mode.

3. A method as set forth in claim 1 or claim 2, wherein said connection state of said user equipment comprises one of a connected state and an idle state.

4. A method as set forth in any preceding claim, wherein said mobility state comprises a speed of movement of said user equipment.

5. A method as set forth in any preceding claim, wherein said information comprises network measurements.

6. A method as set forth in any preceding claim, wherein at least some of said information is received from a network node.

7. A method as set forth in claim 6, wherein said information received from said network node comprises at least one trigger condition.

8. An apparatus comprising

at least one processor;

and at least one memory including 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: determine whether to switch from a first reception mode of operation to a second reception mode of operation;

wherein the determination is made in dependence upon information; and wherein the information comprises at least one of a connection state of said apparatus and a mobility state of said apparatus.

9. An apparatus as set forth in claim 8, wherein said first reception mode of operation comprises a multicast reception mode, and said second reception mode of operation comprises a unicast reception mode.

10. An apparatus as set forth in claim 8 or claim 9, wherein said connection state of said apparatus comprises one of a connected state and an idle state.

1 1 . An apparatus as set forth in any of claims 8 to1 0, wherein said mobility state comprises a speed of movement of said apparatus.

12. An apparatus as set forth in any of claims 8 to 1 1 , wherein said information comprises network measurements.

13. An apparatus as set forth in any of claims 8 to 12, wherein the apparatus is configured to receive at least some of said information from a network node.

14. An apparatus as set forth in claim 13, wherein said information received from said network node comprises at least one trigger condition.

15. A method comprising:

transmitting information, said information comprising criteria for use by a user equipment in determining whether to switch from a first reception mode of operation to a second reception mode of operation; and

wherein said criteria is configured to be dependent upon at least one of a connection state and a mobility state of said user equipment.

16. A method as set forth in claim 1 5, wherein said first reception mode of operation comprises a multicast reception mode, and said second reception mode of operation comprises a unicast reception mode.

17. A method as set forth in claim 15 or claim 16, wherein said criteria comprises at least one of: reference signal received quality; block error rate; mobility information of said user equipment; proximity to a cell boundary.

18. A method as set forth in any of claims 15 to 17, wherein said information comprises threshold values for said criteria.

19. A method as set forth in any of claims 15 to 18, comprising receiving a request from said user equipment to switch from said first reception mode of operation to said second reception mode of operation.

20. An apparatus comprising:

at least one processor;

and at least one memory including 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:

transmit information, said information comprising criteria for use by a user equipment in determining whether to switch from a first reception mode of operation to a second reception mode of operation; and

21 . An apparatus as set forth in claim 20, wherein said first reception mode of operation comprises a multicast reception mode, and said second reception mode of operation comprises a unicast reception mode.

22. An apparatus as set forth in claim 20 or claim 21 , wherein said criteria comprises at least one of: reference signal received quality; block error rate; mobility information of said user equipment; proximity to a cell boundary.

23. An apparatus as set forth in any of claims 20 to 22, wherein said information comprises threshold values for said criteria.

24. An apparatus as set forth in any of claims 20 to 23, wherein the apparatus is configured to receive a request from said user equipment to switch from said first reception mode of operation to said second reception mode of operation.

25. A computer program comprising computer executable instructions which when run on one or more processors perform the method of any of claims 1 to 7 or 20 to 24.