Patent ID: 12245120

DESCRIPTION OF EXAMPLE EMBODIMENTS

Embodiments of the present invention will now be described with reference to an implementation which user's a mobile radio network operating in accordance with the 3GPP Long Term Evolution (LTE) standard.FIG.1provides the example architecture of an LTE network. As shown inFIG.1and as with a conventional mobile radio network, mobile communications devices designated as user equipment (UE)1are arranged to communicate data to and from base stations2which are referred to in LTE as enhanced NodeBs (eNodeB). As shown inFIG.1each of the mobile communications devices1includes a Universal Subscriber Identity Module (USIM) which includes information and parameters which allow the mobile communications devices to access the mobile radio network and to be authenticated for services to which the users have subscribed.

The base stations or eNodeB's2are connected to a serving gateway S-GW6which is arranged to perform routing end management of mobile communications services to the communications devices1as they roam throughout the mobile radio network. In order to maintain mobility management and connectivity, a mobility management entity (MME)8manages the enhanced packet service (EPS) connections with the communications devices1using subscriber information stored in a home subscriber server (HSS)10. Other core network components include the policy charging and resource function (PCRF)12a packet data gateway (P-GW)14which connects to an internet network16and finally to an external server20. More information may be gathered for the LTE architecture from the book entitled“LTE for UMTS OFDN and SC-FDMA based radio access”, Holma H. and Toskala A. page 25 ff.

Communications with a Group of UEs

Embodiments of the present invention provide an arrangement in which a plurality of communications devices maybe associated with each other and grouped together in order to communicate data from different sources. It is envisaged that these sources of data may include data generated by machines so that the data maybe automatically generated sensor readings or events which require logging or other data which is generated by machines rather than by a human interaction. Embodiments of the present invention therefore find application with MTC communications. An example of the group of devices is illustrated inFIG.2where mobile communication devices1are associated with a group22and each is capable of communicating with the wireless access network shown in24.

Examples where it might be appropriate to group devices as shown inFIG.2are provided inFIGS.3and4.FIG.3provides an example of a car which includes a plurality of sensors A1, A2, A3, A4which are receiving stimulus from other components within the car such as within the engine, monitoring the speed of the car or the tyre pressure etc. Any data generated by the sensors A1, A2, A3, A4are fed to mobile communications devices32which may be spatially disposed throughout the car30.

Another example is shown inFIG.4which maybe a bus, for example a bus providing public transport. The bus may also include a plurality of sensors B1, B2, B3, B4and for example may also include a IPS device45which generates information automatically to represent the location of the bus40. As for the example shown inFIG.3each of the sensors B1, B2, B3, B4,45shown inFIG.4has an associated communications device46for transmitting the data generated by these sensors B1, B2, B3, B4,45to an applications program running on a server which is connected to the internet. The data is communicated to that application program via a mobile radio network.

For the examples shown inFIGS.3andFIG.4, since the plurality of communications devices are commonly located, embodiments of the present invention aim to utilise that common location to reduce an amount of signaling over head which is required to establish a communications session and to communicate data from those communications devices via the mobile radio network. Embodiments of the present invention have therefore been devised to achieve such a utilisation and improvement in efficiency.

FIG.5provides a schematic illustration of three communications devices which are adapted to form an associated group of devices which may for example be used for the example applications illustrated inFIGS.3and4. Each of the three devices50shown inFIG.5includes a transmitter and receiver which are arranged to communicate data to and from a base station of the mobile radio network52. Each of the communications devices includes a U-SIM module54and an application processor56which is arranged to run an application program for communicating data to a corresponding application server connected to the mobile radio network.

As will be appreciated in some embodiments the application processor56may be a very simple device or may not be included in the communications devices50, because the function provided by the communications device50is only required to communicate data generated by the sensors via a receiving input58.

According to embodiments of the present invention the U-SIM for each of the communications devices50contains the same identifier which identifies the communications devices to the network for the purpose of establishing a communications bearer. Thus the U-SIM may include the international mobile subscriber identity number (IMSI) or the GUTI which is common for the group of communications devices. Thus as shown in the table below the group of communications devices50shown inFIG.5can be addressed using various identifiers depending on whether it is an Access Stratum communication or a Non Access Stratum (NAS/AS) communication. For an AS communication the cellular radio network temporary identifier (CRNTI) maybe used for establishing a communications session for all members of the group. Also shown below is a table providing an indication of various ways in which the group or cluster of mobile communications devices may be addressed including how a higher layer identification maybe made using one unique URL/URI or IP address for the group or cluster.

Cluster IdentifiersDomainIdentityASOne C-RNTI per group/clusterNASOne IMSI/GUTI per group/clusterOne IMEI per deviceHigher LayerOne unique identifier e.g. URL/URIetc. per deviceOne IP address per group/cluster

The communications devices50shown inFIG.5may also include an uplink receiver60which is arranged to detect and recover data transmitted by other communications devices of the group on the uplink to the mobile radio network using the transceivers52.

As will be appreciated from the following explanation in other embodiments the uplink receiver60may be omitted.

As will be explained in the following paragraphs, in order to realise an efficiency gain by reducing the control plane signaling, one of the devices of the group acts as a master device and performs the transmission of signaling and information on the uplink to the mobile radio network to establish a communications session and to maintain a communication session in accordance with an enhanced packet system mobility and connection management ECM/EMM) function whereas the other devices of the group only listen to the down link communications. Thus part of the improvement its utilisation and efficiency of reducing communications and control plane information is that only one of the devices of the group is transmitting control plane information in the uplink.

FIG.6provides a system level organisation of the devices in the group. As illustrated by a box70, as far as higher layer network functions are concerned, such as the radio access layer, all of the communications devices in the group cats be regarded as a single communications device. Each of the devices in the group act as passive or “slave” device and one of the devices of the group acts as a master device. When none of the devices in the group are transmitting or receiving data then the communications devices enter an ECM idle state72. However, in respect of communicating either AS or NAS data any of the a communications devices of the group can enter an ECM connected state74,76,78in which case one of the devices is transmitting on the up-link and the other communications devices are receiving. Thus all of the communications devices of the group can enter an ECM connected state, but only one of the devices can be granted up-link resources at a time. However all of the devices in the group enter the ECM connected state in order that they can receive down-link transmissions as in effect a point to multi-point communication. Generally, the master communications device transmits all up-link messages for establishing a communications bearer, which is associated with NAS communications.

InFIG.6provides a flow diagram which illustrates a process by which the master communications device establishes a communication session for the group of associated communications devices shown inFIG.5. The flow diagram is summarised as follows:

S1: One of the communications devices of the group acts as a master communications device or UE and establishes a communications session by communicating signaling information for example via the random access channel in order to perform the necessary communication with the mobile radio network. Fox example, the roaster HE may perform a PDP context activation request, or PDN connection request for establishing communications bearer or a similar bearer request protocol. The master UE uses the IMSI/GUTI or other identifier which is common to all members of the group. The master UE maybe for example the first UE of the group which wishes to communicate data via the mobile radio network in winch case it acts as the master UP for establishing communications session. The may detect the control plane data using the uplink receiver60. Alternatively one of the group members of the communications devices of the group may be pre-designated as the master UE and programmed accordingly in which case the up link receiver60can be omitted to form a more simplified architecture.

S2: The other communications devices of the group which are associated together listen for the down link signaling information which is provided in response to the uplink transmissions form the master UE. The down link signaling information will include data required for mobility management and all Non Access Stratum (NAS) information.

S4: although not part of the communications sessions establishment process, the roaster communications device continues to perform authentication and other NAS type communications for the group of devices. Correspondingly, all the devices in the group monitor the down link communications for receiving the necessary information as if the communications device itself had performed the uplink communication.

S6: All other communications devices monitor and decode the control plane signaling to detect who the group is moved from an ECM_IDLE state to an ECM_CONNECTED state.

According to embodiments of the present invention, the following adaptations are applied to a group of communications devices to function as a group so that improvements in the efficiency in control plane/NAS communications can be achieved:The group/cluster is identified by a unique C-RNTI and GUTI/IMSI common to communications devices of the group.Communications from the mobile radio network to the group on the downlink appear as broadcast transmission with no adaptive modulation and coding.For downlink communications to the group of devices paging is supported.For uplink communications, a communications device must reserve uplink resources for a uni-cast transmission.Only the master communications device can be re-authenticated and performs other NAS procedures.Slave devices can implement a subset of procedures which are mandatory fee the master group device.
Identification of the Associated Communications Devices of the Group

In some embodiments devices forming a group/cluster are indexed or identifiable separately from each other. As indicated above for the explanation ofFIG.6, this can be realised during the attachment procedure when the explicit authentication procedure is invoked (requesting IMEI) or implicitly when this information is managed by subscription information (USIM data). In the former case a standard procedure is used and C-RNTI device is allocated during transition to the ECM_CONNECTED state (reserved pre-ambles are used in the random access (RA) procedure). After transition to ECM-IDLE, the following applies:1. Devices forming a group/cluster must be indexed. This can be realised during attachment when the explicit authentication procedure is invoked by the network, (the network requests IMEI which uniquely identifies the device in the cluster and the index can be then allocated) or implicitly when this information is managed by subscription information (the USIM data). In the latter case, master device attaches to the network. In the former ease a standard attach procedure is used by all devices in the cluster and one of them becomes the master device. After the attach procedure is completed all devices make transition to the ECM-IDLE state then the following applies.2. After having all devices in the group registered the system can page the whole group (devices are in ECM_IDLE/EMM_REGISTERED).3. One device in the group is marked as a master device (e.g. the device which was first attached or has special capabilities in the case when slave devices are simplified). This device responds to the paging message and is also the anchor device for NAS procedures i.e. re-authentication, the TAU procedure etc.4. The device which wants to initiate the uplink transmission uses its unique preamble to invoke the RA procedure (the message1). Once its preamble is echoed in the message2and possible contention is resolved in the message4the temporary-RNTI is promoted as the group C-RNTI.5. Other devices passively listen to the RA procedure messages in order to obtain parameters such as the group C-RNTI. This is accomplished by searching for the group NAS identity (in the message4) and optionally group pre-ambles (in the message2) The timing advance parameter might also be used however it might not be accurate for dispersed devices. The TA correction will be obtained later when the MTC device invokes the RA procedure)6. To save power the MTC device in ECM_IDLE are allowed invoke the RA procedure at predefined time slots according to a function e.g. f(device number/index, IMSI)=hyper/radio frame number/sub frame/TTI etc. This is required to prevent slave devices from constant monitoring of the PDCCH to obtain C-RNTI (Conventional LTE devices con trigger the RA procedure at any time other devices in the cluster must detect this in order to obtain the group C-RNTI. This would be inefficient from a power saving point of view to require all devices to monitor the PDCCH constantly. This principle is similar to listening to the paging occasions. As an alternative predefined rules can be used for selecting the PRACH resources to be accessed by the group and this information enabled the MTC devices to choose timing occasions when the PDCCH needs to be monitored)7. After the master device is triggered by the paging message, other sieve devices passively decode any DL transmission constantly monitoring the PDCCH.8. A sudo random function is defined: f_rand(hyper frame number, device number/index, preamble group)=preamble index. The function is used to make sure that all devices in the group use a different preamble when the contention based RA procedure is invoked. As the RA response message can be delayed, the function can not assign the same preamble indexes for X frames/TTIs. This is necessary to distinguish between two RA attempts from devices belonging to the same group/cluster (a contention resolution will not work for these devices as they have the same NAS identifier). Please note that devices can clash in the group and this is resolved by the use of unique preambles. Any contention with UEs which do not belong to the group is resolved by means of NAS identifiers.9. Once the MTC device has been granted the resources, the message Annex 1). After any contention has been resolved (with devices which to the group/cluster) the cluster device starts transmitting UL data.10. Other devices in the group/cluster do not attempt the UL transmission until there are not any allocations on the PDCCH for the group C-RNTI (an inactivity timer must also expire) or the transmitting device and cluster are moved to ECM_IDLE. The former requires the L2 protocols to be kept in sync (e.g. sequence numbers etc.), the latter requires passive decoding of AS signaling to detect when the RRC connection release message is sent. This approach blocks other devices as long as the transmitting device has data to send. Alternatively the transmitting device stops after e.g. Y TTIs/ms so that the transmitting device is moved to ECM_IDLE allowing other devices to request UL resources (via the RA access) and start transmitting. This is effectively implicit (without signaling) UL, transmission brokering between cluster devices.11. L2 synchronisation may be achieved explicitly monitoring by resetting the L2 protocols to a default state after there are not any allocations on the PDCCH for some predefined time (i.e. the inactivity timer expires).12. MTC devices can also be restricted in that how much data they are allowed to transmit once they become the transmitting device regardless if the L2 synchronisation or transition to the ECM-IDLE state are used to indicate to other devices that they are permitted to initiate the UL transmission.13. Only master device can be re-authenticated and performs other NAS procedures.14. Slave devices can implement a subset of procedures which are mandatory for the master group device.15. Devices which join the group later may need to initiate the attach procedure which will be handled by the MME differently to the first attach i.e. the IMEI is always requested from the MTC device, the device is authenticated and security functions are triggered (new security credentials are passed for the whole group). No new PDP context is established just the existing PDP context information is passed.16. The UL virtual multiplexing concept which uses random access procedure (preamble and NAS contention resolutions) used for data transfer to terminals belonging to the group is illustrated inFIG.6.
Up-Link Communication by Communications Device in the Group

As will be appreciated from the explanation vided above only the master communications devices is arranged to transmit signaling information to establish communications session. However any of the devices of the group may at some time transmit data in the up-link and therefore will require up-link resources. Conventionally this is arranged by the mobile communications device transmitting a random access signal in a random access channel such as, for example, the PRACH of the LTE system. The base station receiving the random access signal includes an arrangement to resolve contention between two mobile communications device transmitting a random access signal in the same up-link PRACH. However according, to the present technique the group of communications devices are arranged to reduce a likelihood of contention by dividing the communications devices of the group into sub-groups of devices and pre-allocating a time when the communications devices of the sub group can access the PRACH. As explained above, each of the devices in the group or at least the sub-group is provided with a unique data sequence to use as a pre-amble, mid-amble or post-amble, which can be used to resolve contention.

As explained above in some embodiments predefined sequences are allocated to the group of associated communications devices, which are unique to each of the communications devices in that group or at least within a sub-group which are allocated be same times for allocating the up-link random access channel. Accordingly, in the event of a contentious access of the random access communications channel the mobile radio network can respond by identifying if possible which of the communications devices successfully accessed the random access communications channel. This arrangement is illustrated inFIGS.8,9and10.

FIG.8provides an illustrative representation of the SC-FDMA uplink transmission scheme for the physical layer which includes a plurality of time slots which are divided from a 10 millisecond frame into slots of 0.5 milliseconds. More detail is provided according to the LTE standard as explained in chapter 5 of “LTE for UMTS OFDMA and SC-FDMA based radio access “by Holma H and Toskala A at page 83 ff”. In addition, the frequency band is divided so that a matrix arrangement provides the UE's a plurality of communications physical channels which are allocated by the mobile radio network to the UE's on request. The request for an allocation of uplink resources is provided by transmitting a signal in a physical random access channel (PRACH). A logical arrangement of the access to the random access channel PRACH is shown inFIG.9.

According to the present technique in order to avoid contention between the communications devices of the group each device is allocated a time when if it needs to, access the PRACH according to a function (f_rand) of the hyper frame number, the radio frame number, the device number or its index (the cell phone number being the same for all of the communications devices of the group) and the TTI, which has been explained above. Thus each of the communications devices within the group is provided with a predefined time slot in order to access the PRACH. As shown inFIG.9each of two communications devices, UE1, UE3is allocated the same time100in a first sub-frame102when it can transmit, if it needs to, a random access signal in a PRACH channel. A second sub-group of device UE2, UE4is allocated a second time104in a subsequent frame106when either device can transmit a random access signal. By sub-dividing the devices of the group into sub groups a likelihood of contention between the communications devices of the group is reduced.

In order to balance a likelihood of their being contention on the PRACH and a time that each of the communications devices has to wait before they can request. Up-link resources, more than one communications device may be allocated to the same PRACH. That is it to say that the group of devices are divided into sub-groups and each of these groups is allocated the seine PRACH, within a scheduled time sharing of access to the PRACH. Therefore there is no limit on the size of the group with respect to a minimum time for access a PRACH or a capacity of the PRACH. However, as a result contention access will occur. Accordingly contention resolution is required. To this end, each of the communications devices of the group is provided with a unique data sequence which it uses as a preamble for transmitting in the PRACH.FIG.10illustrates a burst of information which maybe transmitted in the PRACH and includes a preamble field90and a Non Access Stratum (AS) identifier92. Each of the communications devices is provided with a unique, data sequence from one of 64 possible data sequences for use as a preamble. As illustrated inFIG.10each of the devices of the group is provided with a unique preamble whereas other devices within the cell attached to the base station are provided with a different set of preamble sequences or another group of communications devices is provided with a different set of preamble sequences from the 64 available preambles.

Since each of the devices within the group is provided with a unique preamble, when one of the communications devices transmits a burst in the PRACH then the mobile radio network is able to identify that the uplink resources are required by the particular communications device. Accordingly when granting uplink resources, the mobile radio network and more particularly the base station/NodeB perhaps in combination with the S-GW or the MME responds with that communication device's unique preamble so that when listening to the grant of uplink resources, that communications device is able to identify that communications resources for the uplink have been granted to it.

A representation of the contentious access foe uplink communications resources for the group of communications devices is provided by the message flow shown inFIG.11, is reproduced from TS 36.300 and presented here is assist in understanding the embodiments of the present technique. The message exchange illustrated inFIG.11provides four messages, which are explained as follows:

1) Random Access Preamble RACH in uplink:

A communications device of the group of communications devices uses a preamble which has been derived from the f_rand function. The preamble uniquely identifies the communications device within the group. Contention may still exist for access to the random access channel. If another communications device from the same sub-group also transmits contemporaneously in the random access channel then path loss may be used to determine which group a preamble is selected from. The group to which a preamble belongs provides indication of the size of the message3and the radio conditions at the UE. The preamble group information along with the necessary thresholds are broadcast on system information.

2) Random Access Response generated by the Media Access Layer (MAC) on the downlink shared channel (DL-SCH):

The communications devices identifies that the grant of uplink resources is for it using the unique random access preamble identifier.

This communication is semi-synchronous with message1, because it is within flexible window of which the size is one or more transmission time interval (TTI). There is no HARQ, the message is addressed to the RA-RNTI on the PDCCH. This message conveys at least the random access preamble identifier, Timing Alignment information, initial uplink grant and assignment of Temporary C-RNTI, which may or may not be made permanent upon Contention Resolution. This is intended for a variable number of UEs in one DL-SCH message.

3) First scheduled uplink transmission on the uplink shared channel:

This message is sent by the communications device which recognised its unique preamble in message2. The message has the following characteristics:This message uses Hybrid Automatic Repeat Request (H-ARQ);The size of the transport: blocks depends an the uplink grant conveyed in step 2 and at least 80 bits.This message convoys the radio resource connection (RRC) Connection Request generated by the RRC layer and transmitted via CCCH;This message conveys at least an NAS UE identifier but no NAS message;RLC TM: no segmentation;For RRC Connection Re-establishment procedure (only by the master communications device);This message conveys the RRC Connection Re-establishment Request generated by the RRC layer and transmitted via Common Control Channel (CCCH);RLC TM: no segmentation;This message does not contain any NAS message.This message is communicated after handover, from the base station in the target cell, but only from the master communications device;This message conveys the ciphered and integrity protected RRC Handover Confirm generated by the RRC layer and transmitted via DCCH;This message conveys the C-RNTI of the UE sending it as established when requesting uplink resources or following a Handover Command;Includes an uplink Buffer Status Report when possible.For other events this message is sent by the communications device which recognised its random access preamble in the message2.
4) Contention Resolution on the downlink:

All of the communications devices in the group listen to the message4including e communications device which recognised its random access preamble identifier communicated in message2. This message is characterised by the following attributes;Early contention resolution is used in that the eNodeB does not wait for an NAS reply before resolving contention;This message is not synchronised with message3;This message uses Hybrid Automatic Repeat Request (H-ARQ);This message is addressed to the Temporary C-RNTI on the PDCCH for initial access and after radio link failure to the C-RNTI on PDCCH for UE RRC_CONNECTED;H-ARQ feedback is transmitted only by the UE which detects its own UE preamble identifier, as provided in message3, which is provided in response to the Contention Resolution message;For initial access and RRC Connection Re-establishment procedure, no segmentation is used (RLC-TM);The Temporary C-RNTI is promoted to C-RNTI for a UE which detects random access success and does not already have a C-RNTI; it is dropped by others. A UE which detects random access success and already has a C-RNTI resumes using its C-RNTI.

In summary inure provides a flow diagram n the operation of the group of communications devices when gaining access to the uplink resources. The steps illustrated inFIG.12are summarised as follows:

S20: The communications device waits for its turn to transmit in the uplink PRACH in accordance with prearranged time division of the available PRACH timeslots to the other communications devices. The communications device uses its unique random access preamble to transmit a request to have uplink resources to the mobile radio network by transmitting a burst of signals using the preamble in the PRACH. However this may be contemporaneous with another communications device from the same sub-group or indeed another communications device not within the group of associated communications devices. This is because the random access procedure is used by the devices which belong to the sub-group as well as devices which do not belong to the group. There are two levels of contention, which are resolved by either using the preambles allocated by the device of the group and final resolution by an NAS identifier. The devices in the sub-group use preambles which are unique within the sub-group. The first contention resolution is used to discriminate between devices in the sub-group, if they are not in the sub-group, but belong to the group of devices, then contention should not occur because each sub-group is allocated a different time slot in order to avoid contention in the first place. However in both eases it is possible that devices which do not belong to the group of devices will attempt the up-link access and this is the case when the second contention is resolved with the help of NAS identifiers.

S22: if an eNodeB can resolve one of the random access transmission in the PRACH, the eNodeB can respond by providing a response from the MAC or downlink shared channel from the eNodeB and uses the random access preamble identifier of the communications device which transmitted in the PRACH. Thus the eNodeB is able to uniquely identify communications device from within the sub-group of to which it is granting the uplink resources using the preamble assigned to that communications device. Obviously if the random access transmission was by a communications device which is outside the then contention is resolved in the usual way as mentioned above.

S24: Having received a response from the eNodeB the communications device schedules its transmissions on the uplink in accordance with the allocated uplink resources provided there was no contention for the uplink PRACH when it transmitted its burst.

S26: If there was contention when the communications device transmitted the random access transmission in step S20on the PRACH, because another communications device in the sub-group or a device outside the group of devices transmitted a random access transmission in the PRACH and the eNodeB cannot resolve the transmissions then the eNodeB will respond immediately to indicate that there was contention on the random access channel. Thus the base station indicates that the request transmission of the random access communication in the PRACH was unsuccessful. Accordingly the communications device identifies that its attempt to gain uplink resources was unsuccessful and therefore retransmits a random access burst in the PRACH when its scheduled turn comes round again.

Non-Contention Access of Uplink Resources Used By Master UE

A non-contention based random access procedure is only used by the transmitting communications device during handover or by the master device when positioning data is requested. As with the other communications devices of the group, the master communications device is provided with a preamble winch is unique to that device. Furthermore random access is not contentious because the master communications device of the communications device responsible for effecting handover is allocated a time to access the PRACH which is not shared with other communications devices. Accordingly there is no contention access resolution required for the master communications devices, and so the request for uplink resources explained above is modified for the master communications device as explained below:

The three steps of the non-contention based random access procedure are represented by the message flow diagram ofFIG.13and summarised as follows:

0) Random Access Preamble assignment via dedicated signaling in DL:

The eNodeB assigns to UE a non-contention Random Access Preamble. This is a Random Access Preamble which is not within the set of pre-ambles which is sent to the other UEs from within the group for use in broadcast signaling. This non-contention Random Access Preamble is signaled to the roaster UE using either;A Handover command generated by target eNodeB and sent from the source eNodeB for handover, which is handles by the roaster UE; orUsing the PDCCH in the case of downlink data arrival or positioning, which is again being handled by the master UE in the group although other devices in the group also detect the message;
1) Random Access Preamble on the RACH in uplink, which is transmitted by the master communications device of the group. This message is transmitted by e master UR using the non-contention Random Access Preamble.
2) Random Access Response on the downlink shared channel (DL-SCH):
This message is transmitted in a semi-synchronous manner to message1within a flexible window of which the size is two or more TTIs. The message has the following attributes;This message does not use Hybrid Automatic Repeat Request (H-ARQ);The message is addresses to RA-RNTI on PDCCH;This message conveys at least timing alignment information and initial unlink grant for handover, timing alignment information for downlink data arrival; the random access-preamble identifier.This message is intended for one or multiple UEs in one downlink shared (DL-SCH) message.

As illustrated inFIG.14the following steps are taken for the master device to secure uplink resources:

S30: The master device receives a random access preamble for use in requesting uplink resources from this serving base station.

S32: The master communications device transmits a request for uplink resources using the non contentious random access preamble.

S34: The serving base station responds with the grant of uplink resources on the down link shared channel.

As will be appreciated from the example embodiments described above, some or all of the embodiments can provide the following advantages:A cluster of communications devices can be addressed by one C-RNTI/IMSI. A cluster of communications devices can receive data simultaneously via the downlink. Broadcast transmission techniques are applied in a cell for localised delivery to a cluster of communications devices The uni-cast paging procedure is used to activate downlink reception in a cluster of devices.In known systems the UE selects a preamble identifier at random. According to some embodiments random access preambles are used to discriminate between communications devices in a cluster.Any device in the cluster can request uplink resources to send data despite having the same NAS identifier (also C-RNTI). This is enabled by defining an implicit brokering function which prevents other devices to interfere, by uncoordinated uplink transmission. The E-UTRAN is not able to distinguish which cluster device is transmitting.A power saving means is defined for other communications devices in the cluster of devices to limit PDCCH monitoring in ECM_IDLE.
Operation of the Associated Communications Devices

As may be understood from the explanation of the example embodiments presented above, the following advantages are provided:Authorisation and charging can be established for a group/cluster of communications devices rather than for each device individually;NAS communications and procedures per group/cluster are handled by a nominated master device providing a reduction in signaling communications;Implementation of the communications devices of the group apart from the master device can be simplified (light weight slave devices);The group of communications devices can use ono C-RNTI/IMSI;Uplink data communications from the group of devices will be aggregated across the group making communications for the session more efficient.

In order to achieve these advantages it will be necessary for all of the communications devices of the group to monitor and decode control plane signaling, and hence the communications devices may include an up-fink receiver60. For example the communications devices of the group are arranged in one embodiment to detect when the group is moved to EMC_IDLE (no need for keeping Layer 2 in sync as the L2, is re-instantiated on re-transition to ECM_CONNECTED) and/or Layer 2 needs to be synchronised in order to be able to initiate uplink transmission cluster devices while in ECM_CONNECTED. This requires transmission monitoring for the group C-RNTI. Furthermore adaptive modulation and coding cannot be used for downlink communications, all devices in the group/cluster must have the same hardware capabilities including security functions etc. In addition, in some embodiments, the following modifications are made to the mobile radio network infrastructure:A scheduling function at the eNodeB is modified in enable “broadcast like” transmission for selected C-RNTIs;The eNodeB must be pre-provisioned with information that a group of communications devices form a cluster. The eNodeB marks the allocated C-RNTI as the one used for group communication with the cluster.If the attach procedure is used by slave devices, the MME is provided with an identification that subsequent attachments are triggered by devices forming a group/cluster.If connection oriented protocols at higher layers are used, some restrictions and limitations might apply in the scenario when one IP address is allocated to a cluster.

Various modifications can be made to the embodiments described above without departing from the scope of the present invention as defined in the appended claims. In particular although embodiments of the invention have been described with reference to an LTE mobile radio network, it will be appreciated that the present invention can be applied to other forms of network such as 3G, GSM, UMTS, CDMA2000 etc. The term communications device as used herein can be replaced with user equipment (UE), mobile communications device, mobile terminal etc. Furthermore, although the term base station has been used interchangeably with eNodeB it should be understood that there is no difference in functionality between these network entities and that in other architectures the base station will combine with radio network controller to perform some of the functions which have been performed by the eNodeB/Base Station in the above description and therefore corresponding changes could be made when applying the above invention to GPRS, 3G or other architectures.