Abstract:
A microwave radio communications device is configured to communicate with a selected one of at least first and second base stations of respective first and second cells, the first cell having a greater area of coverage than the second cell. The device is configured to retrieve data from a BSID sent from each base station and serving to discriminate between signals from the said first and second base stations indicating the relative cell coverage. Thereby the device achieves selective registration to one of the base stations responsive to the said discrimination.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a microwave radio communications device and related method of operation and network arrangement. 
       BACKGROUND ART 
       [0002]    A microwave radio communication device such as, for example, WiMAX Customer Premises Equipment (CPE), WiMAX Subscriber Stations (SS) and WiMAX Mobile Stations (MS) are well-known elements of a WiMAX communication system. Such devices are arranged to communicate with a WiMAX base station and offer wireless microwave connectivity over distances far in excess of that exhibited by WiFi systems. 
         [0003]    Although WiMAX systems employ WiMAX base stations associated with a corresponding WiMAX cells that have a relatively large geographical coverage, requirements for, sometimes complete, overlap between larger primary WiMAX cells and smaller, generally more localised secondary WiMAX cells often arise. That is, more localised Femto cells can be required within the coverage area of Macro cell and can be employed to assist with reduction in the load on the Macro cell and its associated Macro base station. 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0004]    However, known arrangements are disadvantageously limited in the manner in which, for example, a user device such as a WiMAX CPE or WiMAX MS can discriminate between signals received from a Macro cell base station and those from a Femto cell base station so as to identify which base stations are available for registration purposes. 
         [0005]    An exemplary object of the present invention is to provide for a microwave radio communications device and related method of operation and network arrangement having advantages over known such devices, methods and arrangements. 
       Solution to Problem 
       [0006]    According to one aspect of the present invention there is provided a microwave radio communications device for communication with a selected one of at least first and second base stations of respective first and second cells, the first cell having a greater area of coverage than the second cell. The device is configured to retrieve data from a BSID sent from each base station and serving to discriminate between signals from the said first and second base stations indicating the relative cell coverage. Thereby the device achieves selective registration to one of the base stations responsive to the said discrimination. 
         [0007]    According to another aspect of the invention there is provided a microwave radio communication base station device of a first cell for communication with a microwave radio communication device, the base station device being arranged for transmitting signalling including a BSID serving to differentiate the said base station device from another base station device serving a second cell of lesser area of coverage and for facilitating base station device selection at the microwave radio communication device dependent upon the relative cell coverages. 
         [0008]    According to yet another aspect of the invention, there is provided a method of controlling selected connection in a microwave radio communications device with one of at least a first and second base station of respective first and second cells, the second cell having a lesser area of coverage than the first cell and including the step of retrieving data at the said device from base station originating BSIDs and for discriminating between signals from the said first and second base stations indicating the relative cell coverage for selected connection to one of the base stations and responsive to the discrimination step. 
         [0009]    According to a further aspect of the present invention a base station identification microwave signal comprising an operator identification portion and a base station identification portion, said base station identification portion including data serving to identify the base station from which the signal originates so as to allow discrimination between the said base stations and thereby respective cells at a microwave radio communication device arranged to receive the signal and on the basis of the respective areas of coverage of the cells. 
       ADVANTAGEOUS EFFECTS OF INVENTION 
       [0010]    As will be appreciated, adaption of the BSID so as to provide an indicator for discriminating between different cells can prove particularly advantageous when serving to provide for prioritised registration to at least one of the cells. Such prioritised registration can advantageously be employed within a Macro/Femto cell environment. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0011]      FIG. 1  is a schematic plan view of a WiMAX system configuration arranged for employing the present invention. 
           [0012]      FIG. 2  is a schematic block diagram of a WiMAX user device in the form of a mobile handset and according to an embodiment of the present invention. 
           [0013]      FIG. 3  is a schematic block diagram of a WiMAX base station according to another embodiment of the present invention. 
           [0014]      FIG. 4  is an illustration of broadcast signalling from a base station and having a structure embodying a further aspect of the present invention. 
           [0015]      FIG. 5  is a flow diagram according to an exemplary embodiment of the present invention. 
           [0016]      FIG. 6  is a flow diagram according to an exemplary embodiment of the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Exemplary Embodiment 
       [0017]    Turning first to  FIG. 1  there is illustrated a plan view of a wireless communication system  10  within which a WiMAX user device  12  in the form of a WiMAX CPE is arranged for registration with either a WiMAX base station  14  of a WiMAX Macro cell, or a WiMAX Femto base station  16  of a WiMAX Femto cell. As will be appreciated, the Femto cell offers a more localised geographical coverage and can be advantageously arranged to reduce the load on the WiMAX Macro base station  14 . 
         [0018]    As usual Downlink (DL)-MAP signalling  18 ,  20  occurs respectively between the WiMAX user device  12  and the base stations  16 ,  14  and is discussed in further detail below. 
         [0019]    Turning now to  FIG. 2 , there is illustrated, in block schematic form, further detail of a WiMAX user device  12  of  FIG. 1 . 
         [0020]    The user device  12  includes transceiver functionality  22  along with standard processing functionality  24  and memory functionality  26 . As will be appreciated below, the device also includes functionality  28  for recovering data from the base stations  14 ,  16  serving to discriminate between the said signalling therefrom and to thereby identify the related WiMAX cells available to the handset. 
         [0021]      FIG. 3  represents a schematic block diagram of base station  14  of  FIG. 1 , but could likewise represent schematically the Femto cell base station  16 , and is provided with standard transceiver functionality  30 , processing functionality  32  and memory functionality  34 . In addition, identifier functionality  36  is included for incorporating a base station identifier within the signalling to be transmitted from the WiMAX base station  14  to the WiMAX user device  12 . 
         [0022]    The further particulars of the features functionality  28 ,  36  of the devices  12  and  14  of  FIGS. 2 and 3  respectively will be readily appreciated from the description below. 
         [0023]    As noted, the identifier functionality  36  of the base station  14  is arranged to include a base station identifier within signalling transmitted to the WiMAX user device  12  which, upon receipt, and by way of its retrieval functionality  28  can readily identify, and discriminate between, signalling arising from each of the base stations  14 ,  16  and in a particularly efficient manner. 
         [0024]    As will be appreciated, when a user first switches on the WiMAX user device  12 , the device scans the DL channel within the operational frequency band in an attempt to detect the preamble of a DL sub-frame as transmitted from a base station. Once the preamble has been detected, the user device  12  will then attempt to acquire the DL-MAP within the DL signalling since the DL-MAP commonly contains the Base Station Identification (BSID) which comprises a combination of base station identifier and operator identifier providing the identity of the actual network operator. 
         [0025]    A particular advantageous features of the first exemplary embodiment and which leads to advantageously efficient operation thereof, is that the BSID is employed to allow the user device to readily distinguish between signals from the different WiMAX cells which, in this particular illustrative embodiment, comprises a Macro cell and a Femto cell. 
         [0026]    One embodiment of the manner in which the BSID can be manipulated to provide for such advantageous identification is illustrated with reference to  FIG. 4 . 
         [0027]    As will be appreciated, the BSID  38  comprises a unique global identifier generally forty-eight bits long wherein the upper twenty-four bits  40  contain a unique identifier of the Network Access Provider Identifier (NAP ID) having a first, most significant, bit  42  and a twenty-fourth most significant bit  44  as illustrated in  FIG. 4 . 
         [0028]    The main twenty-four bits of the BSID  38  form the BS identity in which a first bit  48  provides for a Network Service Provider (NSP) identifier flag. In accordance with the particular illustrated embodiments of the present invention, the initial bit  48  of the BS identifier  46  is then followed by the Femto cell identifier bit  52  and a Femto cell operation mode bit  54 . As will be appreciated, the BS identifier  46  has a further twenty-one bits culminating in the least significant bit  50  as illustrated. 
         [0029]    As noted above, the BSID  38  is broadcast from the WiMAX network base station as part of the DL-MAP message and, as will now be appreciated with reference to  FIG. 4 , this message is adapted so as to provide a readily identifiable indication as to whether the BSID  38  received at the user device  12  is associated with the Macro cell or Femto cell base stations  14 ,  16  of in  FIG. 1 . 
         [0030]    As one example, the applied rules are that if the Femto cell identifier bit  52  is “0” then the BSID  38  is taken to be that of a Macro cell, whereas if the cell identifier bit  52  is “1” the BSID  38  is taken to be that of a Femto cell. 
         [0031]    Various modes of operation might also be available, such as with the Femto cell a closed mode or open mode. The closed mode provides restricted access to the cell, wherein the open mode provides unrestricted access to the cell. The relevant mode of operation can be illustrated by way of the operation mode bit  54  as also illustrated with reference to  FIG. 4 . 
         [0032]    Again, the particular ruling adopted can be that of a “0” for the operation mode bit  54  to represent open mode, and a “1” for the operation mode bit  54  to represents closed mode. 
         [0033]    Of course, if the cell identifier bit has already identified the BSID as emanating from a Macro cell, the operational mode bit  54  can be reserved and set to “0”. 
         [0034]    Returning to  FIG. 1  therefore, it will be appreciated that the DL-MAP signalling delivered from the WiMAX Macro base station  14  has a BSID within which the cell identifier bit is set to “0” and the operation mode bit is reserved but with a default value “0”. The DL-MAP arising from the WiMAX Femto cell base station  16  includes a BSID with the cell identifier bit set to “1”, and the operation mode bit  54  set to either “0” or “1” depending upon the particular open/closed mode of operation of the WiMAX Femto cell base station  16 . 
         [0035]    Thus, the exemplary embodiment of the invention as illustrated with reference to  FIGS. 1 and 4 , allows the operation mode of the Femto cell to be readily derived from the BSID since it is included with the DL-MAP messaging delivered from the base station  16 . 
         [0036]    The exemplary embodiment of the invention therefore allows for ready and efficient identification of the presence of a Femto cell within a particular locality, and to thereby readily distinguish that cell from a Macro cell also available such that the user can readily select to camp-on the Femto cell if available. 
         [0037]    Such ready identification of the Femto cell therefore serves to allow for ease and accuracy of selection of that Femto cell so as to, amongst other things, reduce the load in the Macro cell. First priority can therefore be readily given to the Femto cell even when the user device is first switched on, or during handover/cell reselection procedures. 
         [0038]    Also, the provision of ready identification of the mode of operation of the particular cell can also serve to reduce power requirements and power wastage by preventing attempted registration with, a Femto cell that is closed to a particular user device. Ready identification of whether the cell is operating in open, or closed, mode therefore further enhances the advantageous and efficient operation arising from the various embodiments of the present invention. 
         [0039]    As an example therefore, and with reference to the schematic diagram of  FIG. 2 , the memory functionality  26  of the user device  12  can be arranged to store a list of cells with which the particular handset can achieve registration and, in particular those cells that might be closed to access by other devices. 
         [0040]    In particular, once the user device is registered with a WiMAX network by way of a Femto cell operating in closed mode, the device is arranged to store the BSID of that particular Femto cell within its memory functionality so as to create a “stored closed mode Femto cell list” which can be employed subsequently in particular during reselection/handover procedures since preferential registration procedures can be given to any WiMAX base station whose identification matches that contained within the aforementioned stored cell list. This can advantageously reduce unnecessary scanning of other frequencies corresponding to BSIDs that might arise from neighbouring cells. 
         [0041]    Of course, and as will be appreciated below, the stored listing is maintained dynamically such that it can readily be supplemented by further BSIDs as subsequent successful registrations occur. Alternatively the stored listing can be revised by deletion of a BSID from the stored list subsequent to failure to achieve registration with the related base station. 
         [0042]    Turning now to  FIG. 5 , there is provided a flow diagram illustrating operation in relation to potential Femto cell detection during a power-on sequence for the user device  12  such as that illustrated in  FIG. 1 . 
         [0043]    After power-on at step  56 , the WiMAX user device  12  scans the downlink frequency in the operational band in an attempt to achieve camp-on with the first suitable cell identified (step  58 ). After the reading DL-MAP and its associated BSID at step  60 , it is determined at step  62  whether the BSID is that of a permitted operator. Assuming that this is to be the case, the procedure continues to step  64  where it is determined whether or not the BSID exists within the “closed in the Femto cell list” stored within the user device  12 . If, at step  64 , it is determined that the BSID does not exist in that stored list, a determination is then made as step  64  as to whether the BSID is that of a Femto cell. If a Femto cell is identified, the procedure continues to step  68  where a determination of a particular operational mode of the cell is made. If, at step  68 , the operational mode is identified as “open” then a camp-on procedure with the Femto cell commences at step  70  along with a subsequent determination as to whether successful registration is achieved at step  72 . If successful registration is achieved then post-registration signalling procedures continue between the user device and the relevant post station device as indicated at “X”. 
         [0044]    If, at step  66 , it is determined that the BSID is not that of a Femto cell, then by default the cell is identified as a Macro cell at step  67  the user device  12  attempts to camp-on with that Macro cell with the aforesaid subsequent indication at step  72  as to whether registration has proved successful. Should, at step  64 , it be identified that the BSID exists within the “closed mode Femto cell list”, or should it be determined at step  68  that the operation mode of the cell is “closed” then the process continues to step  72  where a camp-on procedure with the Femto cell commences. If such camp-on with the Femto cell proves successful, such that registration is determined to be successful at step  78 , the BSID can be added to the “closed mode Femto cell list” at step  80  if it is not already present. 
         [0045]    Should, at step  78  it be determined that registration was not successful, then the particular BSID, if already present in the “closed mode Femto cell list” can be deleted therefrom. 
         [0046]    Of course, if at either step  72  or  78  the Femto registration was not successful, then the procedure returns to the original frequency scan stage as indicated by “A”. 
         [0047]    Turning now to  FIG. 6 , there is illustrated a flow diagram related to a cell reselection or handover procedure. 
         [0048]    As shown in  FIG. 6 , initially the WiMAx user device  12  is camped on at  84  with the Macro cell  14 . When cell re-selection or handover triggers  86 , then a probable list of BSIDs of neighbour cells is provided  88  to the user device  12 . According to this aspect of the present invention, if it is determined that neighbour cell&#39;s BSID exists  90  in the “closed mode Femto cell list”, then the device  12  will prefer to camp-on with that Femto cell. Otherwise the device  12  will give preference  92  to others Femto cell BSID. Subsequent to camp-on with the Femto cell  94  the WiMAX user device  12  can store  98  the BSID (if it does not already exist) in the “closed mode Femto cell list”. If however there as no successful registration such that WiMAX user device  12  is not able to camp-on with the Femto cell, then the WiMAX user device  12  will delete  100  the entry of the BSID from the “closed mode Femto cell list”. Assuming that it exists. Subsequently, the WiMAX user device  12  will at  102  try to camp-on with the other cells found in the Neighbour Cell List, but first priority can be given to Femto cells. 
         [0049]    As will be appreciated, the first embodiment of the invention can provide for a particularly efficient mechanism for identification of a Femto cell by means of a one-bit identifier within the structure of the BSID. Also a one-bit identifier within the same BSID can be employed so as to, for example, indicate the operation mode of the Femto cell. 
         [0050]    The present invention finds particular use within the WiMAX environment and particularly in relation to for WiMAX CPE, WiMAX MS and any WiMAX user and network device. Priority of camp-on with Femto cells can therefore be readily achieved so as to efficiently realise an advantageous reduction in load on a Macro cell. 
       Other Exemplary Embodiments 
       [0051]    In other exemplary embodiment, a microwave radio communications device includes storage means for retaining a list of local cells with which the device can achieve registration. 
         [0052]    The device can then include comparison means for comparing the content of the said list with a cell identified by way of the said discrimination. 
         [0053]    For dynamic control of the list, the device can include means for entering a cell identifier within the said memory responsive to successful registration therewith. 
         [0054]    Likewise, the device can include means for removal of the cell identity from the said memory if registration proves unsuccessful. 
         [0055]    In particular, the device can be arranged to receive data from a base station identification portion of the BSID. 
         [0056]    Preferably a single bit within the BSID can be employed to indicate the identity of the cell. 
         [0057]    Yet further, the device can be arranged to retrieve data from the BSID including an operational mode indicator. Again, the operational mode indicator can be provided within the base station identifier part of the BSID. Also, the said data includes a single bit of the base station part of the BSID. 
         [0058]    In still other exemplary embodiment, a method includes the step of allowing for the storage of a list of local cells with which the device can achieve registration. In particular, a list of cells has closed availability. 
         [0059]    The method can then also include a step of comparing the content of the said list with a cell identified by way of the discriminating step. 
         [0060]    Preferably, the method can include the step of entering a cell identifier within the said memory responsive to successful registration therewith, and/or the removal of the cell identity from the said memory if registration proves unsuccessful. 
         [0061]    Again, the method advantageously employs a base station identification portion of the BSID for transport of the said data and, in particular, a single bit within the BSID can be employed to indicate the identity of the cell. 
         [0062]    The BSID can also be employed for the provision of an operational mode indicator which can be provided within the base station identifier part of the BSID, and preferably as a single bit thereof. 
         [0063]    It should be appreciated that the functionality of the various devices noted above can be provided as part of a hardware or software solution depending upon particular requirements. 
         [0064]    While the invention has been particularly shown and described with reference to exemplary embodiments thereof, the invention is not limited to these embodiments. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the claims. 
       INCORPORATION BY REFERENCE 
       [0065]    This application is based upon and claims the benefit of priority from UK patent application No. 0810004.2, filed on Jun. 2, 2008, the disclosure of which is incorporated herein in its entirety by reference. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           10  Wireless communication system 
           12  WiMAX user device 
           14  WiMAX Macro base station 
           16  WiMAX Femto base station 
           18  DL-MAP signalling 
           20  DL-MAP signalling 
           22  Transceiver functionality 
           24  Processing functionality 
           26  Memory functionality 
           28  Functionality for recovering data from the base stations 
           30  Transceiver functionality 
           32  Processing functionality 
           34  Memory functionality 
           36  Identifier functionality 
           38  BSID 
           40  NAP ID 
           42  Most significant bit 
           44  Twenty-fourth most significant bit 
           46  BS identifier 
           48  NSP identifier flag 
           50  Least significant bit 
           52  Femto cell identifier bit 
           54  Femto cell operation mode bit