Abstract:
Embodiments relate to network management of a wireless network in which inactive cells are selectively activated thereby changing the radio environment of a user equipment. The changed radio environment is assessed to determine a preferred distribution of active cells for that user equipment.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims priority to U.S. Provisional Patent Application No. 61/863,902, filed Aug. 8, 2013, entitled “ADVANCED WIRELESS COMMUNICATIONS SYSTEMS AND TECHNIQUES”, the entire disclosure of which is hereby incorporated by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    Embodiments relate to network management and, more particularly, to wireless network management. 
       BACKGROUND 
       [0003]    As advances in wireless communication technology progress, it is desirable to improve the capacity of LTE-A networks by deploying heterogeneous networks comprising various cells sizes such as, for example, macrocells, microcells, picocells and femtocells. Such a layered cell structure provides a challenging radio environment from a power management perspective with the concomitant risk that a user equipment (UE) might be sub-optimally served by a respective evolved Node B (eNB) when there could be a better eNB to serve that UE. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]    Embodiments described herein are illustrated, without limitation, by way of example, in the accompanying drawings: 
           [0005]      FIG. 1  shows an Evolved Packet System; 
           [0006]      FIG. 2  depicts a network management system; 
           [0007]      FIG. 3  illustrates a first view of a cellular system; 
           [0008]      FIG. 4  shows a first enlarged view of part of the cellular system; 
           [0009]      FIG. 5  illustrates a second enlarged view of part of the cellular system; 
           [0010]      FIG. 6  depicts a third enlarged view of part of the cellular system; 
           [0011]      FIG. 7  illustrates a first flowchart for network management; and 
           [0012]      FIG. 8  shows a second flowchart for network management. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0013]      FIG. 1  shows an Evolved Packet System (EPS)  100 . The EPS  100  comprises an Evolved Packet Core (EPC)  102 , an eNode B (eNB)  104 , a user equipment (UE)  106  and an operator packet data network  108 . 
         [0014]    The EPC  102  has a mobile management entity (MME)  102 - 2 . The EPC  102  also comprises a serving gateway (S-GW)  102 - 4  and a packet data network gateway (P-GW)  102 - 6 . The S-GW  102 - 4  is operable to exchange packets with the eNB  104  that is serving the UE  106 . The S-GW  102 - 4  operates in effect as a router supporting data exchange between the UE  106  and the P-GW  102 - 6 . The P-GW  102 - 6  serves as a gateway to external packet data networks such as, for example, network  108 . The P-GW  102 - 6  also performs other functions such as address allocation, policy enforcement, packet filtering and routing. It can be appreciated that the packet data network gateway  102 - 6  communicates with the external packet data networks via an SGi interface. 
         [0015]    The MME  102 - 2  performs signaling such that data packets do not pass through the MME  102 - 2 , which decouples data from signaling to support developing capacity for signaling and data separately. The MME  102 - 2  is operable to control many aspects of UE  106  engagement such as, for example, paging the UE  106 , tracking area management, authentication, gateway selection, roaming, security and the like. 
         [0016]    The eNB  104  is responsible for providing the air interface, LTE-Uu, via which the UE  106  can transmit and receive packets. The eNB  104  performs various functions such as, for example, admission control to allow the UE  106  access to the EPS  100  and radio resource management. 
         [0017]    The eNB  104  and the MME  102 - 2  communicate via an S1-MME interface. Optionally, and not shown, the eNB  104  can be connected to one or more other eNBs either directly via an X2 interface or indirectly via the S1-MME interface. 
         [0018]    The eNB  104  is an embodiment of a set of base stations. Such a set of base stations can comprise one or more than one base station. Since the eNB  104  is illustrated as serving the UE  106 , it is said to be an active base station. Therefore, the eNB  104  is an embodiment of a set of active base stations. Such a set of active base stations can comprise one or more than one active base station. Conversely, if eNB  104  was not serving the UE  106 , or any other UE, it would be said to an inactive base station such that the eNB  104  would be an embodiment of a set of inactive base stations. Such a set of inactive base stations can comprise one or more than one inactive base station. Typically, a network, such as a mobile network, has a set of base stations comprising a set of active base stations and a set of inactive base stations. One skilled in the art understands that an eNB can be a species of the genus “base station” and that embodiments of the present invention can be implemented or realised using one or more than one base station. 
         [0019]    The EPC  102  comprises a home subscriber server (HSS)  102 - 8 . The HSS  102 - 8  is a centrally accessible database containing subscriber data associated with one or more than one UE such as, for example the UE  106 . 
         [0020]    One skilled in the art appreciates that the various interfaces described above are implemented to exchange data between the UE  106  and the P-GW  102 - 6  using user plane protocols such as, for example, GPRS tunneling protocol user part (GTP-U), and, for example, Generic Routing Encapsulation (GRE); the latter can be used to realise the S5/S8 interface. 
         [0021]    The EPS  100  uses a plurality of signaling protocols. Air interface signaling, via which the eNB  104  influences or otherwise controls the radio resources used by the UE  106 , is realised using a radio resource control (RRC) protocol. The S1-MME link or interface is realised using the S1 application protocol (S1-AP). 
         [0022]    The MME  102 - 2  controls the UE  106  using two air interface non access stratum protocols, which are the EPS session management (ESM) protocol, which controls data streams associated with the external packet data network  108 , and the EPS mobility management (EMM) protocol, which manages the internal operation of the EPC  102 . EMM and EMS messages are exchanged with the UE  106  using RRC and S1-AP messages using the S1-MME and LTE-Uu interfaces. 
         [0023]    The S11 interface signaling and the S5/S8 interface signaling are implemented using the GPRS tunneling protocol control part (GTP-C). 
         [0024]    The EPC  102  also comprises a Policy Control Rule Function (PCRF) network entity  102 - 10 . The PCRF  102 - 10  is responsible for establishing a number of performance objectives. Examples of the performance objectives can comprise at least one of quality of service (QoS) and charging goals for each session based on a respective or committed service level per UE and service type. 
         [0025]    Referring to  FIG. 2 , there is shown an expanded view  200  of the network operator IP network  108 . It can be appreciated that the IP network  108  comprises a network management system (NMS)  202 . The network management system  202  is used to manage cells formed by the eNB  104  and other eNBs. The network management system  202  has access to storage  204 . The storage  204  is used to store one or more than one network management policy  206 . A network management policy can be used to influence the operation and control of the network provided by the one or more eNBs that form the geographical areas, known as cells, within or via which radio service coverage is provided. 
         [0026]    The network management system  202  is arranged to implement the network management policies  206  by communicating with the P-GW  102 - 6  via a P-GW communication system  208 . Embodiments can be realised in which the P-GW communication system  208  implements the above-described data and signaling via the SGi interface. 
         [0027]    The network management policy can contain one or more than one objective or criterion against which the performance of the network can be assessed. One such objective is managing the power consumption of at least one of the UE  106  and the eNB  104  during an exchange, which exchange can comprise a data exchange, a signaling exchange or both. The power consumption management objective can be directed to reducing at least the overall power consumption. 
         [0028]    Additionally, or alternatively, at least one criterion against which the performance of the network can be assessed is a performance metric comprising a measure associated with at least one of: a received power associated with the user equipment and the at least one active base station, a quality of service associated with one or both of the user equipment and the at least one active base station, a traffic load associated with the at least one active base station, a signal to noise ratio of a predetermined signal of at least one of the user equipment and the at least one active base station, a signal to interference and noise ratio of a predetermined signal of at least one of the user equipment and the at least one active base station, interference associated with a predetermined signal of at least one of the user equipment and the at least one active base station, a location associated with the at least one active base station, a mutual location associated with the user equipment and the at least one active base station, a number of user equipments associated with the at least one active base station, and channel state information associated with the at least one active base station taken jointly and severally in any and all permutations. 
         [0029]    One skilled in the art will appreciate that the network management system  202  may comprise processing circuitry  210  to perform the processing described herein. The processing circuitry  210  may comprise at least one of logic, one or more than one processor, circuitry and executable code for execution by the one or more than one processor, all taken jointly and severally in any and all permutations, to realise the functions performed by the network management system  202  as described herein. 
         [0030]    Referring to  FIG. 3 , there is shown a view of a cellular system  300  provided by a number of eNBs of respective cells. The eNBs can be an eNB such as the eNB  104  described above. In the illustrated embodiment, the cellular system  300  comprises multiple base station classes, which, in turn, define respective cell classes or cell sizes. It will be appreciated that an eNB such as the above-described eNB  104  is an embodiment of a base station. The base station classes can be defined with respect to a predetermined parameter. Embodiments are provided in which the predetermined parameter is associated with base station transmit power. Embodiments are provided in which the predetermined parameter is a rated output power, PRAT, of a base station, which is the mean power level per carrier for a base station operating in single carrier, multi-carrier or carrier aggregation configurations available at an antenna connector during a transmitter ON period. Also shown in  FIG. 3  is the UE  106 . 
         [0031]    It will be appreciated that different PRATs can be defined for different base stations. Embodiments are provided in which the rated output power, PRAT, of the eNBs forming the cellular system  300  correspond to a wide area base station having no upper PRAT limit, a medium range base station having an upper PRAT limit of less than or equal to a first respective level, such as, for example, +38 dBm, a local area base station having an upper PRAT limit of a second respective level such as, for example, +24 dBm, and a home base station having an upper PRAT limit of less than or equal to at least a third respective level such as, for example, +20 dBm for a first respective number, such as, for example, one, of transmit antenna ports, less than or equal to +17 dBm for a second respective number, such as, for example, two, of transmit antenna ports, +14 dBm for a third respective number such as, for example, four, of transmit antenna ports and +11 dBm for a fourth respective number such as, for example, eight, of transmit antenna ports. 
         [0032]    In  FIG. 3 , a number of larger cells  302  to  314  are provided. In the illustrated embodiment, eight such larger cells  302  to  314  are provided. The larger cells  302  to  314  correspond to eNBs that are classified as wide area base stations. A number of smaller cells  316  to  326  are provided. In the illustrated embodiment, six such smaller cells  316  to  326  are provided. The smaller cells  316  to  326  correspond to eNBs that are classified as medium range base stations. 
         [0033]    A number of still smaller cells are also provided. In the illustrated embodiment, twenty-one such still smaller cells are provided. The still smaller cells correspond to eNBs that are classified as at least one of local area base stations and home base stations. The still smaller base stations are shown in greater detail in  FIG. 4 . 
         [0034]      FIG. 4  shows a view  400  of the still smaller base stations  402  to  442 . In the embodiment illustrated the still smaller base stations can be grouped into cell patterns, with cells  402  to  414  forming a first cell pattern comprising a respective number of cells, cells  416  to  428  forming a second cell pattern comprising a respective number of cells and cells  430  to  442  forming a third cell pattern comprising a respective number of cells. In the illustrated embodiment the first to third cell patterns are formed from a seven-cell repeating pattern. In the illustrated embodiment, the still smaller cells have eNBs corresponding to the home base station class of base stations. Although the embodiment uses a common repeating cell pattern, embodiments are not limited thereto. Embodiments can be realised in which the still smaller cells do not form a cell pattern. Alternatively, or additionally, embodiments can be realised in which the first to third cell patterns are different rather than being a repeating cell-pattern and, in particular, rather than being a seven-cell repeating cell pattern. 
         [0035]    An eNB of a cell can have one of a number of predefined states. Embodiments can be realised in which an eNB of a cell has one of two states. Embodiments can be realised in which an eNB of a cell is in either an ON state or an OFF state. An ON state is defined as a state in which the eNB of the cell is available to serve a user equipment. An eNB can be available to serve a UE by transmitting, for example, a control signal that allows a user equipment to select the eNB of that cell as being a preferred eNB to provide a service to that UE. An ON state is an embodiment of an active state. An eNB in an ON state is an embodiment of an active base station. An OFF state is defined as a state in which the eNB of the cell is not in an ON state. Therefore, an embodiment of an OFF state is a state in which the eNB of the cell is not available to serve a user equipment. An OFF state is an embodiment of an inactive state. An eNB in an OFF state is an embodiment of an inactive base station. 
         [0036]    In the embodiment illustrated, cells  418 ,  424 ,  426 ,  428 ,  438  and  440  have one or more than one respective eNB that is in an active state. In the illustrated embodiment, all of the remaining cells have one or more than one eNB that is in an inactive state. 
         [0037]    Cell  426  is shown, by virtue of the dashed line  444  connecting the UE  106  and the cell  426 , as having an active eNB that is serving the UE  106 . A cell is said to be serving a UE when the eNB of that cell is supporting a data transfer or other exchange with the UE  106  or is at least available for such a transfer or other exchange. 
         [0038]    It can be appreciated that the geographical distribution of the ON cells  418 ,  426 ,  428 ,  438  and  440  is sub-optimal relative to the present network demand. The UE  106  and eNB  104  of the serving cell  426  will both be transmitting at a determined power level appropriate to the separation between them and the channel conditions between them. It can also be appreciated that the overall set of still smaller cells comprises at least two sets of cells, that is, a set of active cells and a set of inactive cells. The set of active cells comprises cells  418 ,  424 ,  426 ,  428 ,  438  and  440 . The set of inactive cells comprises cells  402 ,  404 ,  406 ,  408 ,  410 ,  412 ,  414 ,  416 ,  420 ,  422 ,  430 ,  432 ,  434 ,  436 ,  442 . 
         [0039]    Referring to  FIG. 5 , there is shown a further view  500  of the still smaller cells described above with respect to  FIG. 4 . The network management system  202  is arranged to select a first set of inactive cells, that is, inactive base stations, to be switched, at least temporarily, to an active state. In the illustrated embodiment, it can be appreciated that inactive cells  406 ,  408 ,  410 ,  412 ,  416  have been selected by the network management system  202  to be made active. One skilled in the art will appreciate that selecting such a first set of inactive cells is an embodiment of activating a first set of selected base stations of a set of inactive base stations. It will be appreciated that not all inactive base stations have been selected to be made active. Although embodiments could be realised in which all inactive base stations could have been selected to be made active, such an embodiment could have adverse consequences from a power consumption perspective. 
         [0040]    Making the inactive cells  406 ,  408 ,  410 ,  412 ,  416  active will change the radio environment from the perspective of at least the UE  106 . The network management system  202  is arranged to request that the UE  106  produces data associated with the performance of the network such as, for example, data associated with the prevailing radio environment from the perspective of the UE  106 . The data associated with the performance of the network, such as, for example, the data associated with the radio environment, is used to determine whether or not a different geographical distribution of cells better serves the demands of the UE  106  measured against at least one criterion. Embodiments can be realised in which the at least one criterion is transmit power of one or more than one of the eNBs that are active, the transmit power of the UE  106  or both. Additionally, or alternatively, the at least one criterion can be a measure of the distance between the UE  106  and one or more than one of the eNBs of the active cells. 
         [0041]    The network management system  202  receives and processes the data associated with the performance of the network to determine whether or not a different geographical distribution of cells would be more appropriate. It will be appreciated that such receiving and processing are embodiments of assessing at least one performance metric associated with at least one active base station of the active base stations. 
         [0042]    In the illustrated embodiment, it can be appreciated that the UE  106  would be better served by the eNB associated with cell  408  when measured against the either of the above specified criteria of transmit power or distance or both. Therefore, the network management system  202  is arranged to form a further set of active cells. The further set of active cells includes the cell  408  that is better suited to serving UE  106 . Embodiments can be realised in which the further set of active cells comprises only the cell  408  serving the UE  106 . The remaining cells, that is, those that were made active having formerly been inactive and those that were active in any event, can be made inactive on the assumption that they are not required to support the UE  106 , or any other UE. It will be appreciated that making such cells inactive is an embodiment of deactivating a set of selected base stations of the active base stations in response to assessing the at least one performance metric associated with at least one active base station. In such an embodiment, only the cell  408  most appropriate to serving UE  106  would remain active. It can be appreciated that this would improve the power consumption of the network as a whole because only the eNB of the active cell  408  and the UE  106  would be transmitting. It can be appreciated that this would also improve the power consumption of at least one of the selected cell  408  and the UE  106  because the distance between the selected cell  408  and the UE  106  is less than the distance between the UE  106  and the former serving cell  426 . 
         [0043]    Alternatively, or additionally, embodiments can be realised in which the network management system  202  applies one or more than one rule of a set of rules that can be used to expand the further set of active cells. The set of rules can form part of the above described policies  206 . Therefore, referring to  FIG. 6 , there is shown a view  600  of an embodiment in which the network management system  202  has applied a rule that adds a still further set of cells to the further set of active cells. The still further set of cells can comprise, for example, all cells that neighbour the selected active cell  408 , or selected cells of the cells that neighbour the selected active cell  408 . The network management system  202  is arranged to form such a still further set of cells active cells. Therefore, in total, the further set of active cells comprises cells  402 ,  404 ,  406 ,  408 ,  410 ,  412 , and  414 . It will be appreciated that a mobile UE  106  will have a relatively high chance of moving from the presently serving active cell  408  into one cell of the still further set of cells, that is, one of the neighbouring cells in the illustrated embodiment. 
         [0044]    Alternatively, or additionally, the network management system  202  can store additional data associated with the network and that additional data can be used in expanding or establishing the further set of active cells. For example, data associated with a cell may indicate whether or not that cell serves a section of, for example, a motorway, highway or other type of road. Therefore, the additional data may comprise cell data that identifies other cells associated with the same section of motorway, highway or other type of road. Therefore, the network management system  202  is arranged to expand the further set of active cells to include one or more than one further cell associated with the section of the motorway, highway or other type of road. In such an embodiment, the further set of active cells can span an elongate geographical region or any other shaped geographical region. It will be appreciated that the further set of active cells can therefore comprise a selected cell and one or more than one additional cell that is prescribed for selection by data associated with the selected cell. For example, the additional data associated with selected cell  408  may indicate that whenever cell  408  is selected, then cell  406  must also be selected. 
         [0045]    Referring still to  FIG. 6 , it can be appreciated that formerly active cells  416 ,  418 ,  424 ,  426 ,  428 ,  438 , and  440  have been made inactive, that is, switched OFF. 
         [0046]    The one or more than one rule applied by the network management system  202  in constructing the further set of active cells can form part of one or more than one network management policy of the network management policies  206 . 
         [0047]    Embodiments can be realised in which an eNB of a cell that has been selected to be made active, at least temporarily, is arranged to transmit a predetermined signal that can be used in assessing the performance of the network, such as, for example, assessing the prevailing or resulting radio environment. An embodiment can be realised in which such a predetermined signal is a reference signal. The reference signal can comprise a cell specific reference signal, a UE specific reference signal, an MBMS reference signal, a positioning reference signal, a CSI reference signal, a sounding reference signal, or any other signal that can be used by the UE  106  to assess the radio environment and provide data associated with that assessment to the eNBs of cells from which the UE  106  can receive such signals. 
         [0048]    Referring to  FIG. 7 , there is shown a flowchart  700  associated with an embodiment. The network management system  202 , or, more particularly, the processing circuitry  210  of the NMS  202 , can be configured to implement the processing depicted in and described with reference to  FIG. 7 . At step  702 , a first set of inactive cells is selected from inactive cells of a cellular system. Selected cells of the first set of inactive cells are made active. Embodiments can be realised in which making the first set of cells active comprises switching ON the cells of the first set of inactive cells on the assumption that they were formerly in an OFF state. The performance of the network, such as for example, the performance of the resulting or prevailing radio environment, is assessed, at step  706 , against at least one criterion. It will be appreciated that the assessment, at  706 , is an embodiment of assessing at least one performance metric associated with at least one active base station of the active base stations. Embodiments are provided in which the at least one criterion is power consumption of at least one of the UE  106  and at least one active base station. In light of the assessment, a determination is made regarding which active cell or active cells should be switched OFF at step  708 . Those active cells selected to be switched OFF are switched OFF at step  710 . It will be appreciated that switching OFF selected active cells is an embodiment of deactivating a set of selected base stations of the active base stations in response to assessing the performance metric. 
         [0049]    Referring to  FIG. 8 , there is shown a flowchart  800  of a further embodiment. The network management system  202 , or, more particularly, the processing circuitry  210  of the NMS  202 , can be configured to implement the processing depicted in and described with reference to  FIG. 8 . At step  802 , one or more than one eNB of inactive eNBs of a cellular system is selected to have a change of state. The change of state is realised at step  804  in which the selected one or more than one eNB is moved from the inactive, or sleep, state to an active state in which one or more than one signal is output that can be used by a receiving UE to assess channel conditions. The selected one or more than one eNB is instructed, at step  806 , to commence transmitting such a signal that can be used by a receiving UE to assess channel conditions. The UE  106  is instructed at step  808  to provide measurement data associated with channel conditions, that is, associated with the radio environment. The measurement data is forwarded, at step  810 , to a network element, such as, for example, the above described network management system  202 , at which a determination is made, at step  812 , regarding whether or not sufficient measurement data has been collated to take a decision on changing or otherwise updating the geographical distribution of the active eNBs. If the decision at step  812  is that there is insufficient such measurement data, processing resumes at step  802  where one or more than one further eNB is selected to be switched ON and steps  804  to  812  are repeated. For example, the network management policy may prescribe a one or more than one rule that is applied in taking the decision. Embodiments can be realised in which the rule relates to whether or not measurement data has been received relating to all base stations instructed to transmit the reference signal. If such measurement data has not been received from all such base stations, then steps  804  to  812  could be repeated. One skilled in the art will appreciate that one or more than one additional rule might be applied such as, for example, if measurement data from a prescribed number or percentage of base stations instructed to transmit a reference signal has been received, then the determination would be deemed to be sufficient. If the determination at step  812  is that sufficient measurement data has been collated, the processing continues at step  814  where a new distribution of active eNBs is determined. Alternatively, or additionally, a determination is made regarding any presently active eNBs that can be switched OFF. At step  816 , any eNBs that are not needed or that have become redundant are selected to be switched OFF. At step  818 , a command is output to give effect to the decision to switch OFF any such redundant cells. 
         [0050]    The measurement data or other data provided by the UE  106  to allow the performance of the network, such as for example the radio environment, to be assessed can comprise Channel Quality Information (CQI). 
         [0051]    Embodiments can be realised in which the network management system  202  can implement the methods described herein and, in particular, shown in the above flowcharts. Alternatively, or additionally, rather than the network management system  202  implementing embodiments of the present invention, some other network element or apparatus can be used to implement embodiments of the invention. 
         [0052]    The embodiments herein have been described with reference to the selection of inactive cells as being deterministic. However, embodiments are not limited thereto. Embodiments can be realised in which the selection is random. 
         [0053]    Although the above embodiments have been described with reference to two states, that is, an ON state and an OFF state, embodiments are not limited thereto. Alternatively, or additionally, embodiments are provided in which there is a predetermined number of states. For example, embodiments can be realised in which there are three states. The three states can be an active state, in which an eNB of a cell is not in a sleep state and is presently serving at least one respective user equipment, an intermediate state, in which an eNB of a cell is not in a sleep state but is presently not serving at least one respective user equipment, and an inactive state such as, for example, a sleep state, in which an eNB of a cell is in a lower power consumption mode. Embodiments can be realised in which the lower power consumption mode is an OFF state. 
         [0054]    Although the eNBs corresponding to the cells in the cellular system  300  have been classified as being wide area base stations to at least one of local area base stations and home base stations, embodiments are not limited to such an arrangement. Any and all embodiments described herein can take any starting and ending base station classes in the hierarchy of base stations. For example, the largest base station class of the cellular system  300  might correspond to the local area base station with various sizes, such as at least one size, of home base station below that local area base station class. Alternatively, the largest area base station class might be a wide area base station with at least one of the other base stations in the lower base station classes being a medium base station class, a local area base station or a home base station class. The base station classes of the base stations constituting the cellular system  300  can comprise any permutation or combination of a predetermined number of base stations classes such as, for example, the above-described wide area base station class, the medium range base station class, the local area base station class and the home base station class taken jointly and severally in any and all combinations. 
         [0055]    It will be appreciated that embodiments of the present invention can be realised in the form of hardware, software or a combination of hardware and software. Any such software may be stored in the form of volatile or non-volatile storage such as, for example, a storage device like a ROM, whether erasable or rewritable or not, or in the form of memory such as, for example, RAM, memory chips, device or integrated circuits or machine readable storage such as, for example, DVD, memory stick or solid state medium. It will be appreciated that a storage device and storage medium are embodiments of non-transitory machine-readable storage that are suitable for storing a program or programs comprising instructions that, when executed, implement embodiments described and claimed herein. Accordingly, embodiments provide machine executable code for implementing a system, device, apparatus or method as described herein or as claimed herein and non-transitory machine readable storage storing such a program. Still further, such programs may be conveyed electronically via any medium such as a communication signal carried over a wired or wireless connection and embodiments suitably encompass the same. 
         [0056]    Any such hardware can take the form of a processor, suitably programmable, such as for example, a programmable general purpose processor designed for mobile devices, a FPGA, or an ASIC. The foregoing can constitute embodiments of processing circuitry to perform the functions of the above examples and embodiments. Any such hardware can also take the form of a chip or chip set arranged to operate according to any one or more of the above described diagrams, such diagrams and associated descriptions being taken jointly or severally in any and all permutations. 
         [0057]    Although the examples and embodiments have been described separately with respect to their accompanying drawings, embodiments are not limited thereto. Embodiments can be realised in which the embodiments or examples associated with the figures can be taken jointly and severally in any and all permutations. For example, the features of  FIG. 1 , and/or the features of the description of  FIG. 1 , can be taken together with the features of  FIG. 2  or the description of  FIG. 2  and so on. 
         [0058]    Where variations of examples or embodiments have been presented as being at least a member of an enumerated list, either with or without the accompanying language “taken jointly or severally in any and all permutations”, it is clear that all permutations of such enumerated list members are contemplated, which is made more emphatic by the accompanying language “taken jointly and severally in any and all permutations” or, where appropriate, “taken jointly and severally in any and all combinations”. 
         [0059]    In the embodiments described herein, it will be appreciated that a set can comprise one or more than one member. Therefore, for example, the set of inactive eNBs may comprise a single inactive eNB or a plurality of inactive eNBs. Furthermore, the language “active cell” and “inactive cell” can be used synonymously with the language “active base station”, “active eNB” and “inactive base station” and “inactive eNB”. 
         [0060]    Although the above embodiments have been described with reference to using an assessment criterion, alternative or additional embodiments can be realised in which a complex criterion is established. For example, the complex criterion can comprise a multivariate optimization problem expressed and solved using linear programming techniques such as, for example, the Simplex Method. Such a multivariate optimisation can seek to achieve a balance between a plurality of variables such as, for example, UE power consumption and signal to interference and noise ratio. 
         [0061]    Embodiments of the present invention can be applied to, for example, broadband wireless wide area networks (WWANs). However, embodiments are not limited thereto and can be applied to other types of wireless networks where the same or similar advantages may be realised. Such networks specifically include, if applicable, wireless local area networks (WLANs), wireless personal area networks (WPANs) and/or wireless metropolitan area networks (WMANs) such. Further, embodiments may be realised using one or a number of access and modulation techniques, such as, for example, Orthogonal Frequency Division Multiplexing (OFDM) or multi-user OFDM, otherwise referred to as Orthogonal Frequency Division Multiple Access (OFDMA) and, for example, other air interfaces including single carrier communication channels or a combination of protocols or other air interfaces where suitably applicable. 
         [0062]    Furthermore, embodiments may be used in a variety of applications including transmitters and receivers of a radio system, although the present invention is not limited in this respect. Radio systems specifically included within the scope of embodiments of the present invention include, but are not limited to, network interface cards (NICs), network adaptors, fixed or mobile client devices, relays, base stations, femtocells, gateways, bridges, hubs, routers, access points, or other network devices. Further, the radio systems within the scope of embodiments of the invention may be implemented in cellular radiotelephone systems, satellite systems, two-way radio systems as well as computing devices including such radio systems including personal computers (PCs), tablets and related peripherals, personal digital assistants (PDAs), personal computing accessories, hand-held communication devices and all systems which may be related in nature and to which the principles of the inventive embodiments could be suitably applied. 
         [0063]    Still further, the above embodiments have been described with reference to a 3GPP LTE network. However, embodiments are not limited to such a network. Embodiments can be realised within the context of another type of network, such as, for example, an IEEE 802.11 or an IEEE 801.16 wireless network, or any other type of network. 
         [0064]    Although embodiments of the present invention have been described as being implemented by a network management system, embodiments are not limited thereto. Embodiments can be implemented or realised by another apparatus that is able to influence the operation of the base stations, such as the above described eNBs, of the cells of the cellular system, or any one or more than one of the network elements described with reference to  FIG. 1  such as, for example, the MME  102 - 2 , the S-GW  102 - 4 , the P-GW  102 - 6 , the PCRF  102 - 10 , or any other apparatus such as, for example, another network apparatus forming part of the external data packet network  108 . 
         [0065]    Although the above embodiments have been described with reference to a UE  106  and an eNB  104 , embodiments are not limited thereto. Embodiments can be realised in which the mobile network comprises a plurality of UEs and a plurality of base stations. 
         [0066]    The above embodiments have been described with reference to assessing at least one performance metric associated with at least one active base station of the active base stations. However, embodiments can be realised in which the assessment is based on one or more than one performance metric such as, for example, power consumption of the UE  106  and the eNB  104  or interference. Furthermore, although the embodiments assessing at least one performance metric associated with at least one active base station of the active base stations have been described with reference to at least one performance metric, embodiments can additionally or alternatively be realised in which a plurality of performance metrics, each associated with at least one of respective UEs and respective base stations, is used as the basis for determining which active cells should be rendered inactive. 
         [0067]    Embodiments can be realised according to any of the following clauses taken jointly and severally in any and all permutations: 
         [0068]    Clause 1: A method for managing a set of base stations of wireless cells for serving a user equipment, the set of base stations comprising a set of active base stations and a set of inactive base stations, the method comprising activating a first set of selected base stations of the set of inactive base stations, assessing at least one performance metric associated with at least one active base station of the active base stations; and deactivating a set of selected base stations of the active base stations in response to said assessing. 
         [0069]    Clause 2: The method of clause 1 in which said assessing comprises evaluating at least one performance metric associated with the radio environment of the at least one active base station. 
         [0070]    Clause 3: The method of either of clauses 1 and 2 in which the performance metric comprises a measure associated with at least one of a received power associated with the user equipment and the at least one active base station, a quality of service associated with one or both of the user equipment and the at least one active base station, a traffic load associated with the at least one active base station, a signal to noise ratio of a predetermined signal of at least one of the user equipment and the at least one active base station, a signal to interference and noise ratio of a predetermined signal of at least one of the user equipment and the at least one active base station, interference associated with a predetermined signal of at least one of the user equipment and the at least one active base station, a location associated with the at least one active base station, a mutual location associated with the user equipment and the at least one active base station, a number of user equipments associated with the at least one active base station, and channel state information associated with the user equipment and the at least one active base station. 
         [0071]    Clause 4: The method of any of clauses 1 to 3 in which the assessing comprises requesting the user equipment to provide measurement data associated with the at least one active base station. 
         [0072]    Clause 5: The method of clause 4 in which the measurement report comprises data relating to a reference signal associated with the at least one active base station. 
         [0073]    Clause 6: The method of clause 5 in which the reference signal comprises at least one of a channel state information reference signal, a cell specific reference signal, a position reference signal, a sounding reference signal and a demodulation reference signal. 
         [0074]    Clause 7: The method of any preceding clause in which said assessing comprises determining one or more than one distance associated with the user equipment and the at least one active base station. 
         [0075]    Clause 8: The method of any preceding clause in which activating the first set of selected base stations comprises assessing a criterion associated with the active base stations. 
         [0076]    Clause 9: The method of clause 8 in which the criterion associated with the active base stations comprises assessing a criterion associated with at least one other active base station. 
         [0077]    Clause 10: The method of clause 9 in which the criterion associated with the active base stations comprises a criterion associated with different classes of one or more than one active base station. 
         [0078]    Clause 11: The method of any preceding clause in which said assessing comprises establishing multivariate optimisation criterion associated with the user equipment and the active base stations and solving that multivariate optimisation criterion. 
         [0079]    Clause 12: The method of any preceding clause in which the base stations comprise at least one or more than one of: at least two wireless base stations serving a common geographical region, and at least two wireless base stations having different classes in a hierarchical arrangement of the base stations. 
         [0080]    Clause 13: A method of network management, the network comprising a plurality of wireless cells, the plurality of wireless cells comprising one or more than one active wireless cell and one or more than one inactive wireless cells, the method comprising adjusting the geographical distribution of at least one of the active and inactive wireless cells, evaluating a measurement associated with the radio environment of the adjusted geographical distribution of the wireless cells, and, in response to said evaluating, at least one of activating inactive cells and rendering inactive active cells. 
         [0081]    Clause 14: An apparatus for managing a plurality of base stations of wireless cells for serving a user equipment, the plurality of wireless base stations comprising a set of active base stations and a set of inactive base stations, the apparatus comprising processing circuitry to: activate a first set of inactive base stations of the set of inactive base stations, assess the radio environment associated with the active base stations; and deactivate a set of base stations of the active base stations in response to said assessing. 
         [0082]    Clause 15: The apparatus of clause 14 in which said processing circuitry to assess the radio environment associated with the active base stations comprises processing circuitry to evaluate at least one criterion associated with the radio environment. 
         [0083]    Clause 16: The apparatus of clause 15 in which the criterion associated with the radio environment comprises a measure associated with at least one of a received power associated with the user equipment and the at least one active base station, a quality of service associated with one or both of the user equipment and the at least one active base station, a traffic load associated with the at least one active base station, a signal to noise ratio of a predetermined signal of at least one of the user equipment and the at least one active base station, a signal to interference and noise ratio of a predetermined signal of at least one of the user equipment and the at least one active base station, interference associated with a predetermined signal of at least one of the user equipment and the at least one active base station, a location associated with the at least one active base station, a mutual location associated with the user equipment and the at least one active base station, a number of user equipments associated with the at least one active base station, and channel state information associated with the user equipment and the at least one active base station. 
         [0084]    Clause 17: The apparatus of any of clauses 14 to 16 in which the processing circuitry to assess the radio environment associated with the active base stations comprises processing circuitry to request the user equipment to provide measurement data associated with the active base stations. 
         [0085]    Clause 18: The apparatus of clause 17 in which the measurement report comprises data relating to a reference signal associated with at least one of the user equipment and the at least one active base station. 
         [0086]    Clause 19: The apparatus of clause 18 in which the reference signal comprises at least one of a channel state information reference signal, a cell specific reference signal, a position reference signal, a sounding reference signal and a demodulation reference signal. 
         [0087]    Clause 20: The apparatus of any of clauses 14 to 19 in which the processing circuitry to assess the radio environment associated with the active base stations comprises processing circuitry to determine one or more than one distance associated with the user equipment and the active base stations. 
         [0088]    Clause 21: The apparatus of any of clause 14 to 20 in which the processing circuitry to activate the first set of inactive base stations comprises processing circuitry to assess a criterion associated with the active base stations. 
         [0089]    Clause 22: The apparatus of clause 21 in which the criterion associated with the active base stations comprises assessing a criterion associated with at least one other active base station. 
         [0090]    Clause 23: The apparatus of clause 22 in which the criterion associated with the active base stations comprises a criterion associated with different classes of one or more than one base station. 
         [0091]    Clause 24: The apparatus of any of clause 14 to 23 in which the processing circuitry to assess the radio environment comprises processing circuitry to establish multivariate optimisation criterion associated with the user equipment and the base stations and solving that multivariate optimisation criterion. 
         [0092]    Clause 25: The apparatus of any of clauses 14 to 24 in which the base stations comprise at least one or more than one of: at least two wireless base stations serving a common geographical region, and at least two wireless base stations having different classes in a hierarchical arrangement of the plurality of base stations. 
         [0093]    Clause 26: An apparatus for network management, the network comprising a plurality of wireless cells, the plurality of wireless cells comprising one or more than one active wireless cell and one or more than one inactive wireless cells, the apparatus comprising processing circuitry to adjust the geographical distribution of at least one of active and inactive wireless cells, evaluate the performance of the network associated with the adjusted geographical distribution of the wireless cells, and to activate inactive cells in response to the processing circuitry to evaluate the performance of the network or to render inactive active cells in response to the processing circuitry to evaluate the performance of the network 
         [0094]    Clause 27: Computer executable program code comprising instructions arranged, when executed, to implement the method of any of clauses 1 to 13. 
         [0095]    Clause 28: Computer readable storage storing a computer executable program code of clause 27. 
         [0096]    Clause 29. A method, eNodeB, apparatus, network element, computer program and computer readable storage substantially as described herein with reference to and/or as illustrated in the accompanying drawings. 
         [0097]    Clause 30: An apparatus for managing a set of eNBs for serving a user equipment, the apparatus comprising processing circuitry to: 
         [0098]    process data defining a geographical radio service area provided by the set of eNBs; the set of eNBs comprising a first set of eNBs, in a first respective power state, available to serve the user equipment and a second set of eNBs, in a second respective power state, unavailable to serve the user equipment, the processing circuitry to process the data defining the geographical radio service area comprising processing circuitry for: 
         [0099]    adapting the data defining the geographical radio service area provided by the set of eNBs by changing at least one eNB of the second set of eNBs from the second respective power state to a first respective power state in the first set of eNBs to define an adapted geographical radio service area provided by the set of eNBs, 
         [0100]    processing performance data associated with the adapted geographical radio service area provided by the set of eNBs, and 
         [0101]    establishing data defining a further geographical radio service area provided by the first set of eNBs in response to said processing. 
         [0102]    Clause 31: An apparatus of clause 30, in which said processing circuitry for establishing comprises transitioning at least one eNB of the first set of eNBs from a first respective power state to the second set of eNBs having the second respective power state. 
         [0103]    Clause 32: An apparatus of either of clauses 30 and 31, in which said processing performance data associated with the adapted geographical radio service area provided by the set of eNBs comprises processing a performance metric associated with at least one of the user equipment and at least one eNB of the first set of eNBs to determine whether or not the performance of the first set of eNBs meets at least one criterion. 
         [0104]    Clause 33: An apparatus of clause 32 in which said establishing comprises adapting the data defining the adapted geographical radio service area to provide a different geographical radio service area. 
         [0105]    Clause 34: An apparatus of clause 33 in which said adapting the data defining the adapted geographical radio service area to provide a different geographical radio service area comprises at least one of switching a first eNB of the first set of eNBs that was previously in the second set of eNBs back the second set of eNBs having the second respective power state and switching a first eNB of the first set of eNBs that was in the first set of eNBs to the second set of eNBs having the second respective power state. 
         [0106]    Clause 35: The apparatus of clause 32 in which the at least one criterion comprises a measure associated with at least one of a received power associated with the user equipment and at least one eNB of the first set of eNBs, a quality of service associated with one or both of the user equipment and at least one eNB of the first set of eNBs, a traffic load associated with at least one eNB of the first set of eNBs, a signal to noise ratio of a predetermined signal of at least one of the user equipment and at least one eNB of the first set of eNBs, a signal to interference and noise ratio of a predetermined signal of at least one of the user equipment and at least one eNB of the first set of eNBs, interference associated with a predetermined signal of at least one of the user equipment and at least one eNB of the first set of eNBs, a location or distance associated with at least one eNB of the first set of eNBs, a mutual location associated with the user equipment and at least one eNB of the first set of eNBs, a number of user equipments associated with at least one eNB of the first set of eNBs, and channel state information associated with the user equipment and at least one eNB of the first set of eNBs. 
         [0107]    Clause 36: The apparatus of any of clauses 30 to 35 in which the processing circuitry comprises processing circuitry associated with requesting the user equipment to provide measurement data associated with one or more than one eNB of the first set of eNBs. 
         [0108]    Clause 37: The apparatus of clause 36 in which the measurement data comprises data relating to a reference signal associated with at least one of the user equipment and at least one eNB of the first set of eNBs. 
         [0109]    Clause 38: The apparatus of clause 37 in which the reference signal comprises at least one of a channel state information reference signal, a cell specific reference signal, a position reference signal, a sounding reference signal and a demodulation reference signal. 
         [0110]    Clause 39: The apparatus of any of clauses 30 to 38 in which the processing circuitry for processing performance data comprises processing circuitry to determine one or more than one distance associated with the user equipment and one or more than one eNB of the first set of eNBs. 
         [0111]    Clause 40: The apparatus of any of clauses 30 to 39 in which the processing circuitry to process performance data associated with the adapted geographical radio service area provide by the first set of eNBs comprises processing circuitry to establish multivariate optimisation criterion associated with the user equipment and at least one eNB of the first set of eNBs and processing circuitry for solving that multivariate optimisation criterion. 
         [0112]    Clause 41: The apparatus of clause 40 in which processing circuitry for establishing the data defining the further geographical radio service area provided by the first set of eNBs comprises selecting one or more than one eNB of the first set of eNBs according to said solving of the multivariate optimisation criterion to provide the data defining the further geographical radio service area provided by the first set of eNBs. 
         [0113]    Clause 42: The apparatus of any of clauses 30 to 41 further comprising processing circuitry to output a request to at least one of the user equipment and one or more than one eNB of the first set of eNBs to provide measurement data associated with the radio environment provided by at least part of the adapted geographical radio service area. 
         [0114]    Clause 43: The apparatus of clause 41 further comprising processing circuitry to receive performance data in response output the request to at least one of the user equipment and one or more than one eNB of the first set of eNBs to provide measurement data associated with the radio environment provided by at least part of the adapted geographical radio service area. 
         [0115]    Clause 44: The apparatus of any of clauses 30 to 43 further comprising processing circuitry for outputting an instruction to one or more eNB of the first set of eNBs and to one or more of the second set of eNBs to adopt respective power states. 
         [0116]    Clause 45: An apparatus for network management, the network comprising a plurality of wireless cells, the plurality of wireless cells comprising one or more than one active wireless cell and one or more than one inactive wireless cells, the apparatus comprising processing circuitry to adjust the geographical distribution of at least one of active and inactive wireless cells, evaluate the performance of the network associated with the adjusted geographical distribution of the wireless cells, and to activate inactive cells in response to the processing circuitry to evaluate the performance of the network or to render inactive active cells in response to the processing circuitry to evaluate the performance of the network.