Abstract:
The invention provides for mobile radio communications device ( 10 ) for operation within a mobile radio communications network and arranged to employ one of a plurality of possible power saving modes, and arranged to send non-access stratum or access stratum signalling ( 14 ) to the network including an indication of at least one of the said plurality of possible power saving modes, and responsive to which indication the network ( 12 ) is arranged to return confirmation ( 16 ) of the power saving mode to be employed by the mobile radio communications device ( 10 ), the mobile radio communications device ( 10 ) further being arranged to receive the said confirmation ( 16 ) and to initiate operation of the confirmed power-saving mode ( 26; 38; 44 ).

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a mobile radio communications device arranged to employ a power saving mode and a mobile radio communications network device arranged to communicate with the mobile radio communications device in relation to the power saving mode, and to related network systems and methods of operation. 
       BACKGROUND ART 
       [0002]    Power consumption is an important feature for mobile terminals using a battery power supply and also for mobile terminals using external power supply. Its importance increases with the continued growth of device populations such as for example the proliferation of Machine Type Communication (MTC) devices and also the deployment of devices in ever more demanding situations and environments. For example, for Machine To Machine (M2M) use cases, such as remote sensors that run on battery-power, there are significant cost implications for on-site exchange (or re-charge) of the batteries for a large device population and the battery lifetime may even determine the device&#39;s lifetime if it is not foreseen to re-charge or replace the battery. 
         [0003]    Discussion within the 3 rd  Generation Partnership Project (3GPP) for mobile communications have resulted in numerous study and work items related to such problems. 3GPP Services and Systems Aspects (SA2) (architecture) group has discussed UE power consumption optimisation for energy saving and battery power consumption optimisation (UEPCOP) within the MTC work item, The main objective study is identified as:
       Lower UE Power Consumption as per the service requirements defined clause in clause 7.1.1 of Technical Specification TS 22.368.
 
In particular, 3GPP SA2 has already identified several proposals for UE power consumption optimization in Technical Report TR 23.887.
       
 
         [0005]    One proposal outlined in TR23.887, at section 7.1.3.3, relates to employment of a Power Saving Mode/State (PSM) to be deployed by a mobile terminal for reducing its power consumption. That mode described is similar to a power-off mode, but the mobile terminal remains registered with the network and so there is no need to re-attach or re-establish Packet Data Network (PDN) connections. A mobile terminal in PSM is not immediately reachable for Mobile Terminating (MT) services. However, such a terminal in PSM can be made available for MT services but only for the period of an Active Time after a Mobile Originated (MO) event such as data transfer or signalling, e.g. after a periodic Tracking Area Update/Routing Area Update (TAU/RAU) procedure. 
         [0006]    When the mobile terminal is use the PSM, a request is made for an Active Time value, and a request for a Periodic TAU/RAU Timer value, during Attach and TAU procedures. The mobile terminal and a network device such as a Mobile Management Entity/Serving GPRS Support Node MME/SGSN start the Active timer with the Active Time value that is allocated by the network when mobile terminal is transiting from a Connected mode to an Idle mode. When the Active timer expires, the mobile terminal deactivates its Access Stratum functions and enters PSM. In PSM, due to deactivation of the Access Stratum functions, the mobile terminal stops all idle mode procedures, but continues to run the periodic TAU/RAU timer. The mobile terminal will be arranged to resume Access Stratum functions and idle mode procedures before the periodic TAU/RAU timer expires for performing the periodic TAU/RAU procedure as applicable. Further, the mobile terminal may resume idle mode procedures and Access Stratum functions any time during PSM, for example e.g. for MO communications. 
         [0007]    When the Active Timer value expires, the MME/SGSN can determine that the mobile terminal has entered PSM and so is not available for paging. 
         [0008]    In PSM the mobile terminal is in Idle mode and the MME/SGSN will treat the mobile terminal as if registered, but not reachable. The Access Stratum functions of the mobile terminal are considered as deactivated during PSM. 
         [0009]    An alternative Power Saving scenario is discussed at section 7.1.3.4 of TR23.887 and based on Attach/Detach procedures. 
         [0010]    This proposal is based on the functionality that the mobile terminal attaches to the network to communicate and, after the communication session, the mobile terminal detaches from the network and switches off its 3GPP modem (MT) during a period to save mobile terminal power. However, the mobile terminal will periodically perform the Attach and Detach procedures. 
         [0011]    Two particular examples are discussed and the first comprises Network Assisted Power Saving (NAPS) and is outlined at section 7.1.3.4.3.2 of TR23.887. 
         [0012]    To summarise, many mobile terminals (e.g. MTC devices for vendor machines, electricity metering, weather sensors, etc) exhibit expected/scheduled communication patterns in which the device and Application server communicate at regular intervals only (e.g. once a day or once a week etc). There is therefore a possibility to save energy if the mobile terminal detaches in between these occasions, and in addition to the reduction in the usage of network resources. As a service, the operator may offer the Machine-to-Machine (M2M) service provider the possibility of to simplifying such regular communication. Based on agreement as to how often the communication needs to occur, the operator can pre-configure information in the network, and optionally the mobile terminal, for assisting regular attach/detach of the mobile terminal. The NAPS proposal provides a mechanism to enhance the existing Network Initiated Detach procedure for such scenarios. Also, this function allows the mobile terminal to propose a time for remaining attached (identified as User Equipment (UE) power saving active timer) and this allows the network to provide the mobile terminal with a new timer (UE power saving wakeup timer). The mobile terminal can then re-attach to the network when the timer has expired. As the mobile terminal detachment and re-attachment is performed by way of network-control, it is possible for mobile terminal to look to achieve both batter-power saving, and network signalling optimization, while retaining network control of when the mobile terminal should look to perform re-attachment. 
         [0013]    The second example, referred to at section 7.1.3.4.3.3 of TR23.887 as Implicit Detach, is based on the coordinated (i.e. synchronized) transition from an attached state to a detached state in both the network and the mobile terminal but without explicit signalling. The Implicit Detach is performed soon after communication is completed in order to avoid long idle state periods as commonly arising, for example the periodic TAU/RAU period at UE, the reachable tinier+detach timer at the network, which can be in order of hours. 
         [0014]    Generally, to ensure the coordinated implicit transition to a detached state, the configuration of two main parameters in the network and in the mobile terminal is required first a certain “implicit detach time” is identified and secondly an “event/point” when this implicit detach timer starts. The term “implicit detach time” refers to the time duration from a certain event (start point) until the mobile terminal and network implicitly transfer to detached state. 
         [0015]    For implicit detach coordination with the network, and when a mobile terminal is configured for Implicit Detach, either the mobile terminal needs to indicate its Implicit Detach capability configuration to the network (in NAS signalling for example); or the MME can get the mobile terminal&#39;s Implicit Detach capability configuration from its subscription information (e.g. provisioned by the M2M service capability layer from the Service Capability Server (SCS). 
         [0016]    In such configuration, the implicit detach time is either exchanged between the network and the mobile terminal, takes the value of the “grant time interval” or the “communication window” if time-controlled communication, or takes the value of the Periodic TAU timer. 
         [0017]    In the latter case the network allocates the Periodic TAU timer by taking into account the subscription information or configuration. 
         [0018]    Thus various solutions for mobile terminal power saving and optimization are proposed in TR23.887 and each solution has its specific characteristics and suits specific operating scenarios. 
         [0019]    For example, the Power Saving Mode/State of section 7.1.3.3 permits long battery lifetime for stationary and moving UEs with infrequent communications needs. Although the UE is kept attached, the UE is not reachable alter active timer expiry until the next periodic TA/RA update. However, the UE can still be reached via SMS messages, which can be delivered when the UE wakes up as it remains active for the active time after contacting the network. 
         [0020]    However, the Power Saving Mode/State can add signalling load due to the polling of the network with the periodic updates even when there is no uplink or downlink data to exchange. This makes the Power Save State/Mode not suitable for scenarios where the mobile terminal needs to transmit very rarely, such as for example, once a day or even more infrequently (i.e. utility meters, some e-health devises etc). 
         [0021]    The Attach/Detach solutions of section 7.1.3.4 involve detachment of the mobile terminal detached and so does not generate signaling load onto the system (e.g. RAU/TAU). Also, the SGSN/MME does not need to retain the mobile terminal&#39;s context and this can serve to free-up many network-side resources. Also, with the implicit detach approach a further saving in the signaling can be achieved as there is no need for explicit detach signaling. The mobile terminal and the network can then perform a coordinated implicit detach. 
         [0022]    It is clear that the attach/detach approach would suit MTC scenarios where the mobile terminal communicates very infrequently and it is tolerant to paging (such as for example utility meters etc.). Indeed, this is recognized in Technical Specification TS22.368, at section 7.1.1 where it is noted that “MTC Devices may or may not be kept attached to the network when not communicating, depending on operator policies and MTC Application requirements.” 
       CITATION LIST 
     Non Patent Literature 
       [0023]    NPL 1: 3rd Generation Partnership Project Technical Specification TS 22.368 
         [0024]    NPL 2: 3rd Generation Partnership Project Services and Systems Aspects Technical Report TR 23.887 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0025]    Power saving procedures therefor offer various advantages, and exhibit various characteristics but which themselves cause potential problems and operational limitations. The invention seeks to provide for mobile and network terminal devices and related network systems and methods of operation having advantages over known devices, systems and methods. 
       Solution to Problem 
       [0026]    According to one aspect of the present invention there is provided a mobile radio communications device for operation within a mobile radio communications network and arranged to employ one of a plurality of possible power saving modes, and arranged to send non-access stratum or access stratum signalling to the network including an indication of at least one of the said plurality of possible power saving modes, and responsive to which indication the network is arranged to return confirmation of the power saving mode to be employed by the mobile radio communications device, the mobile radio communications device further being arranged to receive the said confirmation and to initiate operation of the confirmed power-saving mode. 
         [0027]    Known mobile terminal power saving solutions such as those outlined above are beneficial and they are more or less applicable for specific use cases. However, in order to allow the mobile terminal to take full advantage of such power-saving solutions the invention advantageously allows for mobile terminal power-saving mode control advantageously based on the mobile terminal preference and the network considerations (i.e. subscription, resources, capability). 
         [0028]    The invention proves advantageous insofar as the mobile radio communications device can be arranged to employ a power-saving mode best suited to its own characteristics and/or new network considerations. 
         [0029]    In particular, the invention is arranged such that the said indication comprises an indication of preferred power saving mode. 
         [0030]    Advantageously, non-access stratum signalling is employed and comprises any one or more of an Attach Request, a Tracking Area Update request or a Routing Area Update request. 
         [0031]    Advantageously, the non-access stratum signalling can also include the Periodic Update Timer and/or an Active Timer value. 
         [0032]    Further, the mobile radio communications device can be arranged to receive the said confirmation by way of non-access stratum signalling. 
         [0033]    Again, the said non-access stratum signalling as received by the mobile radio communications device can comprise any one or more of an Attach Accept message, a Routing Area Update accept message or a Tracking Area Update accept message. 
         [0034]    Again, confirmation of the Periodic Update Timer and/or Active Timer values can also be included within the non-access stratum signalling received from the network and containing confirmed power-save mode. 
         [0035]    Preferably, and after receipt of the confirmed power-saving mode from the network, the mobile radio communications device can be arranged to enter idle mode. 
         [0036]    Preferably, the mobile radio communications device can be arranged to initiate an active timer value confirming active time prior to entry into a power saving state. 
         [0037]    Further, this mobile radio communications device can be arranged to activate a Periodic Update Timer value serving to determine when the mobile radio communications network is to exit a power-saving state. 
         [0038]    Preferably, and subsequent to the mobile radio communications device leaving the power saving state, the mobile radio communications device can be arranged to issue a Routing Area Update request or Tracking Area Update request. 
         [0039]    Also, the further Routing Area Update request or Tracking Area Update request can include an indication of at least one of the plurality of possible power-saving modes for later selection by the network. 
         [0040]    According to another arrangement, the said at least one of a plurality of possible power saving modes comprises a detach procedure and, preferably, an implicit detach procedure. 
         [0041]    Advantageously, the mobile radio communications device can be arranged to initiate an active timer period prior to the implicit detach from the network. 
         [0042]    As a further option, the detach procedure can comprise an explicit detach procedure in which the mobile radio communications device is arranged to initiate an active tinier period prior to sending a detach request to the network. 
         [0043]    In particular, the said indication of possible power save mode can comprise an indication of a plurality of power save modes and also a preference indicator to identify at least one preferred power-save mode. 
         [0044]    According to another aspect of the present invention there is provided a mobile radio communications network device for communicating with a mobile radio communications device within a mobile radio communication network environment, and arranged to determine which of the plurality of possible power saving modes is employed by the mobile radio communications device, the mobile radio communications network device being arranged to receive non-access stratum or access stratum signalling from the mobile radio communications device and including an indication of at least one of the said plurality of possible power saving modes and, responsive to the said indication, the mobile radio communications network device being arranged to return confirmation of the power saving mode to be employed by the mobile radio communications device. 
         [0045]    The invention proves advantageous insofar as the mobile radio communications network device can be arranged to control use of a power-saving mode best suited to characteristics of the mobile radio communications device and/or new network considerations. 
         [0046]    In particular, the invention is arranged for the provision of the said indication in the form of an indication of preferred power saving mode. 
         [0047]    Advantageously the said non-access stratum signalling from the mobile radio communications device can comprise any one or more of an Attach Request, a Tracking Area Update request or a Routing Area Update request. 
         [0048]    Advantageously, the non-access stratum signalling can also include a Periodic Update Tinier and/or an Active Timer value. 
         [0049]    Further, the said confirmation returned by the mobile radio communications network device can comprise non-access stratum signalling. 
         [0050]    Again, the said non-access stratum signalling comprising the said confirmation can comprise any one or more of an Attach Accept message, a Routing Area Update accept message or a Tracking Area Update accept message. 
         [0051]    Again, confirmation of the Periodic Update Timer and/or Active Timer values can also be included within the non-access stratum signalling received at, and sent from, the mobile radio communications network device. 
         [0052]    Preferably, and subsequent to the mobile radio communications device leaving the power saving state, the mobile radio communications network device is arranged to issue a Routing Area Update request or Tracking Area Update request. 
         [0053]    Preferably, the further Routing Area Update request or Tracking Area Update request can include an indication of at least one of the plurality of possible power saving modes for later selection by the network. 
         [0054]    According to another arrangement, the said at least one of a plurality of possible power saving modes can comprise a detach procedure and, preferably, an implicit detach procedure. 
         [0055]    According to yet another aspect of the present invention there is provided a mobile radio communications system employing a mobile radio communications device and mobile radio communications network device as outlined above. 
         [0056]    According to a further aspect of the present invention, there is provided a method of controlling a mobile radio communication device for operation within a mobile radio communications network environment and arranged to employ one of a plurality of possible power saving modes, including the step of sending a non-access stratum signal or access stratum signal to the network including an indication of at least one of the said plurality of possible power saving modes and, responsive to which indication, the network returns confirmation of the power-saving mode to be employed by the mobile radio communications device, and further including the step of receiving the said confirmation from the network and initiating the confirmed power-saving mode in the mobile radio communications device. 
         [0057]    As above, the invention can prove advantageous insofar as the mobile radio communications device can be arranged to employ a power saving mode best suited to its own characteristics and/or new network considerations. 
         [0058]    In particular, the method of the invention is arranged such that the said indication comprises an indication of preferred power saving mode. 
         [0059]    Advantageously, the method can employ non-access stratum signalling which can include any one or more of an Attach Request, a Tracking Area Update request or a Routing Area Update Request. 
         [0060]    Advantageously, a Periodic Update Timer and/or an Active Timer value can be included in the non-access stratum signalling. 
         [0061]    Further, the method can include the step of mobile radio communications device receiving the said confirmation by way of non-access stratum signalling. 
         [0062]    Again, the said non-access stratum signalling can comprise any one or more of an Attach Accept message, a Routing Area Update accept message or a Tracking Area Update accept message. 
         [0063]    The method can include confirmation of the Periodic Update Timer and/or Active Timer values within the non-access stratum signalling received from the network and containing the confirmed power-save mode. 
         [0064]    After receipt of the confirmed power saving mode from the network, the method can include the mobile radio communications device entering idle mode. 
         [0065]    The method can include the step of the mobile radio communications device initiating an Active Timer value confirming active time prior to entry into a power-saving state. 
         [0066]    Further, a Periodic Update Timer value can be activated and serving to determine when the mobile radio communications network is to leave the power-saving state. 
         [0067]    Preferably, and subsequent to the mobile radio communications device leaving the power-saving state, the method can include the step of the mobile radio communications device issuing a Routing Area Update request or Tracking Area Update request. In particular, the further routing error update request, or tracking area update request, can include an indication of at least one of the plurality of possible power-saving modes for later selection by the network. 
         [0068]    Yet further, the method can include the step of initiating an active timer period prior to the implicit detach from the network. 
         [0069]    As a further option, the detach procedure can comprise an explicit detach procedure, and the method can include the step of the mobile radio communications device initiating an active timer period prior to sending a detach request to the network. 
         [0070]    According to still a further aspect of the present invention, there is provided a method of controlling communication with a mobile radio communications device operating within a mobile communications network environment including a mobile radio communications network device, the method including the step of determining which of the plurality of possible power saving modes is to be employed by the mobile radio communications device and including the step of receiving non-access stratum or access stratum signalling from the mobile radio communication device including an indication of at least one of the said plurality of possible power saving modes and, responsive to the said indication, the network confirming to the mobile radio communications device the power-saving mode to be employed. 
         [0071]    In particular, the method of the invention is arranged such that the said indication comprises an indication of preferred power saving mode. 
         [0072]    In this method, the said non-access stratum signalling can comprise any one or more of an Attach Request, a Tracking Area Update request or a Routing Area Update request. 
         [0073]    Advantageously, the non-access stratum signalling can also include a Periodic Update Timer and/or an Active Timer value. 
         [0074]    Further, the confirmation returned from the network can comprise non-access stratum signalling. 
         [0075]    The said non-access stratum signalling comprising the confirmation can comprise any one or more of an Attach Accept message, a Routing Area Update accept message or a Tracking Area Update accept message. 
         [0076]    Further, the Periodic Update Timer and/or Active Timer values can also be included within the non-access stratum signalling received at, and sent from, the mobile radio communications network device. 
         [0077]    Subsequent to the mobile radio communications device leaving the power saving state, the method can include the network issuing a Routing Area Update request or Tracking Area Update request. Preferably, within the method, the further Routing Area Update request or Tracking Area Update request can include an indication of at least one of the plurality of possible power saving modes for later selection by the network. 
         [0078]    The method can further control the employment of a detach procedure and, preferably an implicit detach procedure. 
         [0079]    As a further option, the detach procedure controlled can comprise an explicit detach procedure in which the mobile radio communications device is arranged to initiate an active timer period prior to sending a detach request for receipt by the network. 
         [0080]    As will be appreciated, the present invention can also provide for a method of controlling signalling within a mobile radio communications network and including control of a mobile radio communications device and mobile radio network device as outline above. 
         [0081]    As will therefore be appreciated, the invention can provide for a mechanism to control the power save mode in the mobile terminal so that one of the above-mentioned power-save modes of TR23.887 can be applied. This advantageously allows for unifying and controlling the selection of a power-save mode for the mobile terminal and can also allow for selection of a power-save mode that best suits the circumstances of a specific mobile terminal and that is acceptable and available by the network. 
         [0082]    As discussed further, a new parameter can be employed by the mobile terminal during Attach or RA/TA update procedure. A mobile terminal can then indicate its power save mode preference in the new parameter ‘UE power save mode preference’ within the Attach Request message or RA/TA Update Request message. The use of any other existing or new (designated) NAS or AS messages to convey the UE power save mode preference is not excluded. 
         [0083]    A new parameter can also be employed by the network (MME/SGSN) and sent to a mobile terminal during the attach procedure or RA/TA procedures. The network (MME/SGSN) can then decide the power save mode for a given mobile terminal based on the latter&#39;s preference (UE power save mode preference received from the mobile terminal), on subscription rights and/or on any other network considerations. Then the network (MME/SGSN) would relay the confirmed ‘power save mode’ to the mobile terminal within the Attach Accept or RA/TA Update Accept messages. The use of any other existing or new (designated) NAS or AS messages to convey the mobile terminal power save mode parameter is not excluded. When Active timer in the mobile terminal expires, the mobile terminal enters a power save mode defined by this ‘power save mode’ parameter. 
       Advantageous Effects of Invention 
       [0084]    As above, the invention proves advantageous insofar as the mobile radio communications device can be arranged to employ a power-saving mode best suited to its own characteristics and/or new network considerations. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0085]      FIG. 1  is a signalling diagram illustrating signalling arising between a mobile radio communications device and a mobile radio communications network for the control of a power saving mode and according to one aspect of the present invention. 
           [0086]      FIG. 2  is a signalling diagram illustrating signalling arising between a mobile radio communications device and a mobile radio communications network for the control of a power saving mode and according to another aspect of the present invention. 
           [0087]      FIG. 3  is a signalling diagram illustrating signalling arising between a mobile radio communications device and a mobile radio communications network for the control of a power saving mode and according to yet another aspect of the present invention. 
           [0088]      FIG. 4  is a schematic illustration of a mobile radio communications device arranged to operate in accordance with an embodiment of the present invention. 
           [0089]      FIG. 5  is a schematic representation of a mobile radio communications network device arranged to operate in accordance with one aspect of the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0090]    The present invention is now described further hereinafter, by way of example only, with reference to the accompanying drawings. 
         [0091]    Turning to  FIGS. 1-3 , there are illustrated signalling exchanges between a mobile radio communications device, i.e. mobile terminal such as a, User Equipment (UE) device  10  and a network schematically represented in the illustrated embodiments of  FIGS. 1-3  as a Mobile Management Entity/Serving GPRS Support Node  12 . 
         [0092]    According to each of the three examples represented by  FIGS. 1-3 , the power saving features according to the present invention first arise in relation to an Attach/RAU/TAU request signal  14  sent from the UE  10  to the network device  12  and which, in addition to the inclusion of Periodic Update Timer and Active timer information, also includes the identification of at least one of a plurality of possible power saving modes available to the mobile terminal. Such indication is provided by way of a specific parameter included within the Attach/RAU/TAU request  14  and which can be characterised as comprising a mobile terminal power saving mode preference parameter. 
         [0093]    As part of the ongoing Attach/RAU/TAU procedure, an accept message  16  is returned from the network device  12  to the UE  10  which, in addition to confirmation of the Periodic Update Timer and active timer data, also includes confirmation of a power saving mode identified by the network device  12  for employment by the UE  10 . 
         [0094]    Subsequent to the receipt of the Attach/RAU/TAU accept signal  16 , the UE  10  then enters its idle mode  18 . 
         [0095]    Subsequent to entry into its idle mode, the operation of the UE  10  continues according to the confirmed power saving mode to be employed and three examples of which are discussed in further detail with reference to  FIGS. 1, 2 and 3  respectively. 
         [0096]    Turning first to  FIG. 1 , and as noted above, during an Attach or RAU/TAU procedure, the UE  10  specifies its preferred Periodic Update Timer value, Active timer value and UE power save mode preference in the Attach Request or RAU/TAU Request messages  14 . The ‘UE power-save mode preference’ parameter defines the power save mode that is preferred by the mobile UE  10  i.e. Power Save State, Implicit Detach, Explicit Detach or any other appropriate power-save mode. 
         [0097]    The network device (MME/SGSN)  12  confirms the Periodic Update Timer value, Active timer value and power-save mode in the Attach Accept message or RAU/TAU accept message  16 . The ‘power save mode’ parameter contained within message  16  defines the power save mode to be deployed by both, the UE  10  and the network as represented by the MME/SGSN  12 . The network sets the Active tinier value to the mobile reachable timer value. 
         [0098]    When the UE  10  enters idle mode  18 , it can start the Periodic Update Timer  20  and the Active timer  22  and the network can start the mobile reachability timer  24 . At the expiry of the Active tinier  22  period, the UE  10  enters Power Saving State  26  (such as described above and known from TR23.887. s7.1.3.3). In the Power Saving State  26  the UE  10  deactivates its Access Stratum functions and can also stop all idle mode procedures, but continues to run the periodic TAU/RAU timer  20 . 
         [0099]    At the expiry of Mobile reachable timer  24  the network (MME/SGSN)  12  starts the Implicit detach timer  28  and enters its Power Saving State  30 . In the Power Saving State  30  the network  12  does not page the UE  10 . 
         [0100]    At the expiry of Periodic Update Timer  20  on the UE  10  side, the UE  10  triggers RAU/TAU Request  32  and exits the Power Saving State  26 . Within the RAU/TAU Request  32 , the UE  10  can again express its preference for a power save mode in the UE power save mode preference parameter, and which can comprise the same power save mode, or a different one. 
         [0101]    Turning now to  FIG. 2 , another example is shown and wherein the UE  10  enters idle mode  18  after the aforementioned Request  14  and Accept  16  signalling and starts the Active timer  34 , and the network  12  starts the mobile reachability timer  36 . At the expiry of the Active timer  34  the UE  10  implicitly transfers to a detached state  38 . The UE  10  is thus implicitly detached and the network (SGSN/MME)  12  also implicitly detaches  40  the UE  10  at expiry of the mobile reachability timer  36  that has the same duration as the Active tinier  34 . In this manner, the UE  10  can be implicitly detached from the network  12  according to an Implicit Detach power-save mode such as described in TR23.887, s7.1.3.4.3.3. 
         [0102]    Turning now to  FIG. 3 , a further example is shown and wherein the UE  10  enters idle mode  18  again after Request  14  and Accept  16  signalling exchanges and starts Active timer  42  and the network  12  starts the mobile reachability timer  43 . At the expiry of the Active timer  42  the mobile terminal triggers a request for Explicit Detach  44  for example in accordance with the mobile terminal initiated Detach procedure disclosed in Technical Specifications TS24.301 and TS24.008. For example, in such described advantages, the detach procedure can be initiated by the UE by sending a DETACH REQUEST message and the Detach type IE included in the message indicates whether the detach is due to a “switch off” or not. The Detach type IE also indicates whether the detach is for EPS services only, for non-EPS services only, or for both. 
         [0103]    As noted above,  FIG. 4  comprise a schematic of a mobile radio communications device such as the UE  10  identified in  FIGS. 1-3  and comprising standard mobile radio communications device functionality such as an antenna  46  operatively connected to transmission/reception circuitry  48  operatively connected to control circuitry  50  which is in turn, connected to memory functionality  52  and a user interface  54 . As again illustrated schematically, the control circuitry  50  includes sleep mode preference functionality  56  sends sleep mode initiation functionality  58 . Such functionality can be arranged to operate in accordance with any one or more of the irrelevance of  FIGS. 1-3  wherein the sleep mode preference functionality  56  operative to identify one of a possible plurality of sleep mode functions that can be stored in the memory functionality  52  as a preferred sleep mode or, indeed, indicate a plurality of sleep modes but with a ranking of preference. 
         [0104]    Such preference, whether it refer to a single sleep mode, or a ranked order of sleep modes, is then arranged by the control circuitry  50  to be transmitted by way of the transmission/reception circuitry  48  and antenna  46  from the UE  10 , to the network. Signalling to the UE  10  serving to confirm which of the, ideally preferred, power-save modes proposed in the signalling from the UE  10  is actually going to be initiated and employed. Such indication is received by way of the antenna  46  and transmission/reception circuitry  48  then initiated within sleep mode initiation functionality  58  of the controller  50  so that the UE  10  can then operate in accordance with an appropriate sleep mode given UE device  10  preferences and also network consideration. 
         [0105]    Turning now to  FIG. 5 , there is provided a similarly schematic illustration but this time of a mobile radio communications network device, such as the SGSN/MME  12  discussed and illustrated in relation to embodiments of  FIGS. 1-3 . 
         [0106]    The network device contains a functionality of an interface  60  preferably connected to a transmission reception circuitry  62  which, in turn, is operatively connected to a controller  64  in turn connected to memory functionality  66 . 
         [0107]    As will be appreciated, the controller  64  is arranged to indicate one or more power-saving modes preferred for adoption by a UE  10  such as that in  FIG. 4  and to determine, also advantageously based on network considerations, which of the preferred power-saving modes is to be employed by the UE  10  and, returns appropriate control signalling under control of the control functionality  64  so as to initiate the appropriate power-saving mode within the UE  10 . It would be appreciated, the power-saving mode may comprise that indicated as the preferred mode of the UE  10  or they comprise a selection from the ranking order of preferred modes, illustrated by the UE  10 . 
         [0108]    It should of course be appreciated that, for example, although described in relation to 3G Radio Access Technology, the invention is equally applicable to other RATs including 2G technology. As such, the above mentioned reference to 3G can include reference to 2G and accordingly reference to RAU/TAU messages can optionally refer to LA Update messages, and reference to SGSN/MME can include reference to MSC devices will be appreciated, the invention is particularly advantageous in providing a new mechanism for power-save control within a mobile radio communications device and network and that allows for increased/improved power save options for the UE mobile terminal and the network. It also allows for a power-save mode that better suits the specific mobile terminal circumstances and requirements, and further can allow for a dynamic control and change of the power-save modes while the mobile terminal is travelling, i.e. non-stationary. 
         [0109]    Although the present invention has been explained with reference to the exemplary embodiments, the present invention is not limited by the above exemplary embodiments. Various modifications, obvious to those in the art, can be made to the configurations and details of the present invention within the scope of the invention. 
         [0110]    This application is based upon and claims the benefit of priority from United Kingdom patent application No. 1319226.5, filed on Oct. 31, 2013, the disclosure of which is incorporated herein in its entirety by reference. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           10  UE 
           12  Network device 
           14  Attach/RAU/TAU request signal 
           16  Accept message 
           18  Idle mode 
           20  Periodic Update Timer 
           22  Active timer 
           24  Mobile reachability timer 
           26  Power Saving State 
           28  Implicit detach timer 
           30  Power Saving State 
           32  RAU/TAU Request 
           34  Active timer 
           36  Mobile reachability timer 
           38  Detached state 
           40  Detach 
           42  Active timer 
           43  Mobile reachability timer 
           44  Explicit Detach 
           46  Antenna 
           48  Transmission/reception circuitry 
           50  Control circuitry 
           52  Memory functionality 
           54  User interface 
           56  Sleep mode preference functionality 
           58  Sleep mode initiation functionality 
           60  Interface 
           62  Transmission reception circuitry 
           64  Controller 
           66  Memory functionality