Abstract:
A method for paging a mobile station ( 40 ) served by a wireless telecommunications network (A) is provided. The network (A) includes a plurality of base stations ( 30 ) serving corresponding cells ( 32 ) which the mobile station ( 40 ) selectively uses to access the network (A). A plurality of location areas ( 22 ) are defined each encompassing a plurality of the aforementioned cells ( 32 ). The method includes: receiving a registration signal from the mobile station ( 40 ) each time the mobile station ( 40 ) enters a new location area ( 22 ); remembering the location area ( 22 ) from which the registration signal was last received; monitoring which cell ( 32 ) the mobile station ( 40 ) uses to access the network (A); remembering the cell ( 32 ) last used by the mobile station ( 40 ) to access the network (A); and, paging selected location areas ( 22 ) when the mobile station ( 40 ) is being sought, the location areas ( 22 ) that are paged being selected based upon the remember location area ( 22 ) and the remembered cell ( 32 ).

Description:
FIELD  
       [0001]     The present inventive subject matter relates to the wireless or mobile telecommunications arts. Particular application is found in conjunction with paging a mobile station (MS), and the specification makes particular reference thereto. However, it is to be appreciated that aspects of the present inventive subject matter are also amenable to other like applications.  
       BACKGROUND  
       [0002]     Wireless or mobile telecommunications networks are generally known in the art. A MS (e.g., a mobile telephone or other mobile or wireless end user device) obtains service and/or access to the wireless network via an over-the-air radio frequency interface with a base station (BS). Each BS provides the over-the-air interface for and/or serves a particular geographic coverage area known as a cell. Typically, a plurality of base stations are operatively connected to and/or served by a mobile switching center (MSC) that is responsible for routing traffic for a particular MS to the appropriate BS currently serving that MS (i.e., to the cell in which the MS is currently located).  
         [0003]     The “mobility” in mobile communications is commonly achieved in part via two communication channels between the BS and MS, namely, a paging channel and an access channel. The paging channel is used to verify and/or establish the location of the MS within the network and to deliver incoming calls to the MS. The access channel is used by the MS for registration purposes, i.e., to report power-up of the MS, to report changes in the location of the MS, etc.  
         [0004]     Typically, a mobile service provider seeks to maximize the number of busy hour call attempts (BHCA) in order to serve an increasing number of mobile subscribers. One obstacle to achieving this goal, however, is the availability of sufficient paging channel bandwidth. While there are known ways to increase paging capacity, they often involve considerable expense and/or lead time, e.g., adding new bandwidth. Accordingly, it is desirable to optimize the usage of existing paging channel bandwidth.  
         [0005]     Historically, when an incoming call arrived at a MSC for a MS, all the cells in the entire MSC would be paged in order to contact the MS and deliver the call. That is to say, the MSC would signal all the base stations it served to transmit a paging signal over their paging channels to verify or establish the location of the MS within one of the cells. This approach, however, used a considerable amount of paging channel bandwidth insomuch as all the cells within the geographic region served by the MSC where paged for any given instance.  
         [0006]     A recent improvement was to partition the cells served by the MSC into a plurality of zones, i.e., groups of neighboring cells known as location areas (LAs), and begin paging only those cells in the last known LA of the MS being sought. While this reduced the load on the paging channel because fewer cells were instructed to page the MS for any given instance, the load on the access channel increased because registration messages were sent by the MS to the MSC every time a LA boundary was crossed. That is to say, in order for the MSC to know which LA the MS was in at any given time, the MS would signal the MSC using the access channel each time it entered a new LA. Smaller LAs in turn mean that the LA boundaries are closer to one another, which in turn means that as a mobile subscriber travels they are more likely to cross more boundaries. Accordingly, increasing the number of LAs per MSC would reduce the size of each LA and the load on the paging channel, but at the expense of increasing the load on the access channel. Service providers have found that creating more than a few LAs per MSC results in access channel overload. However, there remains the desire to further reduce the paging channel load in order to support more mobiles and/or more services.  
         [0007]     A generally effective approach for paging a MS is to being paging a small geographic area, and if there is no response, to increase the size of the area that is paged. Therefore, when an MS is being sought, usually, only the last-seen or last-registered LA for that MS is paged first. If there is no response from the paged MS to the first attempt, then a second paging attempt is made using what is known as LA cluster (LAC) paging. In traditional LAC paging, the last-seen or last-registered LA along with all of its neighboring LAs receive the page.  
         [0008]     For example,  FIG. 1  is used to illustrate a traditional LAC paging configuration. As shown, there are three MSC serving neighboring geographic areas, namely, MSC 1 , MSC 2  and MSC 3 . Each MSC has its coverage area divided into a plurality of LAs. In the illustrated example, MSC 1  serves LA 1  through LA 8 , MSC 2  serves LA 9  through LA 11 , and MSC 3  serves LA 12  through LA 14 . Each LA in turn contains a plurality of cells, for example, as illustrated in LA 5 . As a MS travels among the LAs, it registers its current location with the various MSCs each time it enters a new LA, i.e., each time it crosses from one LA into the next or each time it crosses an LA boundary. For example, the MS registers with the MSC serving its location by sending a registration signal to the MSC using the access channel. In this manner, the MSC is able to remember the most recent LA from which the MS registered. For example, the MSC may store the current registration information (e.g., the identity of the LA from which the MS last registered) in a location register or database. Suitably, the location registers or databases of the other MSCs are updated accordingly. Assuming for purposes of this example that the sought MS last registered from LA 5 , then a traditional LAC paging protocol would page all the LAs highlighted in gray, that is LA 5  (i.e., the last known LA of the MS) along with LA 3 , LA 4 , LA 9 , LA 12  and LA 6  (i.e., all the neighboring LAs surrounding the last known LA of the MS).  
         [0009]     While LAC paging is quite effective in locating a MS that has crossed an LA boundary, a disadvantage remains insomuch as the geographic area encompassed by an LA and all its surrounding LAs is still significantly large, thereby resulting in a significant number of cells being effected by a given LAC page and a significant amount of paging channel bandwidth being used. Therefore, it is desirable to reduce the geographic area paged by LAC paging without significantly reducing the corresponding page response rate of LAC paging, i.e., without significantly reducing the likelihood of verifying or establishing the location of the MS being sought with the LAC page.  
         [0010]     Accordingly, a new and improved paging system and/or method for a wireless telecommunications network is disclosed that overcomes the above-referenced problems and others.  
       SUMMARY  
       [0011]     In accordance with one embodiment, a method for paging a mobile station served by a wireless telecommunications network is provided. The network includes a plurality of base stations serving corresponding cells which the mobile station selectively uses to access the network. A plurality of location areas are defined each encompassing a plurality of the aforementioned cells. The method includes: receiving a registration signal from the mobile station each time the mobile station enters a new location area; remembering the location area from which the registration signal was last received; monitoring which cell the mobile station uses to access the network; remembering the cell last used by the mobile station to access the network; and, paging selected location areas when the mobile station is being sought, the location areas that are paged being selected based upon the remember location area and the remembered cell.  
         [0012]     In accordance with another aspect, a system for paging a mobile station served by a wireless telecommunications network is provided. The network includes a plurality of base stations serving corresponding cells which the mobile station selectively uses to access the network. A plurality of location areas are defined, each location area encompassing a plurality of the aforementioned cells. The system includes: receiving means for receiving a registration signal from the mobile station each time the mobile station enters a new location area; location area remembering means for remembering the location area from which the registration signal was last received; monitoring means for monitoring which cell the mobile station uses to access the network; cell remembering means for remembering the cell last used by the mobile station to access the network; and, paging means for paging selected location areas when the mobile station is being sought, the location areas that are paged being selected based upon the remembered location area from location area remembering means and the remembered cell from the cell remembering means.  
         [0013]     Numerous advantages and benefits of the inventive subject matter disclosed herein will become apparent to those of ordinary skill in the art upon reading and understanding the present specification. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     The present inventive subject matter may take form in various components and arrangements of components, and in various steps and arrangements of steps. The drawings are only for purposes of illustrating example embodiments and are not to be construed as limiting. Further, it is to be appreciated that the drawings are not to scale.  
         [0015]      FIG. 1  is a diagram illustrating how a wireless or mobile telecommunications network implements a traditional LAC paging protocol.  
         [0016]      FIG. 2  is a diagram illustrating a telecommunications network suitable for practicing aspects of the present inventive subject matter.  
         [0017]      FIG. 3  is a diagram used for illustrating an exemplary implementation of a customized LAC paging protocol embodying aspects of the present inventive subject matter. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0018]     For clarity and simplicity, the present specification shall refer to structural and/or functional elements, entities and/or facilities, relevant communication standards, protocols and/or services, and other components and features that are commonly known in the telecommunications art without further detailed explanation as to their configuration or operation except to the extent they have been modified or altered in accordance with and/or to accommodate the embodiment(s) presented herein.  
         [0019]     With reference to  FIG. 2 , a telecommunications network A includes a public switched telephone network  10  operatively connected to and/or in communication with a MSC  20  in the usual manner. The MSC  20  is operatively connected to and/or in communication with a plurality of base stations  30  in the usual manner. As is understood in the art, each BS  30  provides an over-the-air radio frequency interface for its respective geographic area or cell  32 . Selectively, a MS (such as the exemplary MS  40  illustrated) is provided telecommunication services and/or otherwise accesses the network A via the interface and/or BS serving the cell in which the MS is located. In the usual manner two communication channels are selectively employed between the BS  30  and MS  40 , namely, a paging channel and an access channel. The paging channel is used to verify and/or establish the location of the MS  40  within the network A and to deliver incoming calls to the MS  40 . The access channel is used by the MS  40  for registration purposes, i.e., to report power-up of the MS  40 , to report changes in the location of the MS  40 , etc.  
         [0020]     While only one MSC is illustrated in  FIG. 2  for purposes of simplification and clarity, it is to be appreciated that the network A may in fact include any number of one or more MSCs that are similarly situated and/or arranged. Additionally, while three BS  30  and three corresponding cells  32  are illustrated in  FIG. 2 , it is to be appreciated that more or less than three base stations and/or cells may be similarly situated with respect to any of the one or more MSCs in the network A. That is to say, each MSC in the network A may optionally serve any number of one or more base stations and/or corresponding cells. Additionally, while only one exemplary MS is illustrated in  FIG. 2 , the network A optionally serves any number of one or more mobile stations similarly situated and/or arranged in any of the one or more cells  32 .  
         [0021]     With reference to  FIG. 3 , three MSCs  20  of the network A are shown serving neighboring geographic areas. For distinction purposes they are labeled MSC 1 , MSC 2  and MSC 3 . Each MSC  20  has its coverage area divided into a plurality of LAs  22 . For distinction purposes they are labeled LA 1  through LA 14 . In the illustrated example, MSC 1  serves LA 1  through LA 8 , MSC 2  serves LA 9  through LA 11 , and MSC 3  serves LA 12  through LA 14 . Each LA  22  in turn contains a plurality of cells  32 , for example, as illustrated in LA 5 . As the MS  40  travels among the LAs  22 , it registers its current location with the various MSCs  20  each time it enters a new LA  22 , i.e., each time it crosses from one LA  22  into the next or each time it crosses an LA boundary. For example, the MS  40  registers with the MSC  20  serving its location by sending a registration signal to the MSC  20  using the access channel. In this manner, the MSC  20  is able to remember the most recent LA  22  from which the MS  40  registered. For example, the MSC  20  may store the current registration information (including, e.g., the identity of the LA from which the MS last registered) in a location register or database  24  (see  FIG. 2 ). Suitably, the location registers or databases of the other MSCs  20  are updated accordingly. Alternately, the database  24  is arranged within the network A so as to be accessible by each of the MSCs.  
         [0022]     In addition to the last or most recent LA  22  from which MS  40  registered, the last or most recent cell  32  accessed by the MS  40  is also monitored and/or remembered by the network A. This information is optionally stored along with and/or as part of the current registration information in the database- 24 . Cell access events include those events where the MS  40  accesses a cell  32 , i.e., the MS  40  sends, receives or otherwise exchanges a transmission to, from or with a BS  30 . For example, a cell access event may include, registration of the MS  40 , the MS  40  receiving an incoming call, the MS  40  placing an outgoing call, the transmission of packet data to or from the MS  40 , short message service (SMS) message receipt or transmittal, etc. For each of these activities, the network A is able to determine which BS  30  and/or cell  32  the MS  40  is using. Suitably, this cell location and/or identity is captured and/or updated at each cell access event, e.g., by the MSC  20 . Suitably, the captured cell location and/or identity for the last or most recent cell access event is then maintained or stored in the database  24  along with and/or as part of the current registration information including the last or most recent LA from which the MS  40  registered.  
         [0023]     Suitably, a customized LAC (CLAC) paging protocol is employed to page the MS  40  when it is being sought by the network A. The CLAC protocol uses the current registration information, e.g., in the database  24 , including the last known LA of the MS and the last known cell of the MS, to determine which LAs  22  are to be paged. That is to say, the network A knows and/or remembers the last or most recent LA  22  from which the MS  40  registered and the cell  32  the MS  40  use during its last or most recent cell access event, and based upon this information, the CLAC paging protocol determines which LAs  22  are to be paged when seeking the MS  40 .  
         [0024]     For purposes of explanation, the last or most recent LA  22  from which the MS  40  registered shall be referred to herein as the last registered LA  22 , and the cell  32  use by the MS  40  for the last or most recent cell access event shall be referred to herein as the last used cell  32 . In accordance with a suitable CLAC paging protocol, the last registered LA  22  is paged. Optionally, a number of particular LAs  22  neighboring the last registered LA  22  are also paged, depending upon the location of the last used cell  32  within, the last registered LA  22 . Suitably, if the last used cell  32  is located at or towards the interior or center of the last registered LA  22 , then no neighboring LAs  22  are paged along with the last registered LA  22 , i.e., only the last registered LA  22  is paged. On the other hand, if the last used cell  32  is located at or towards the exterior or boundary of the last registered LA  22 , then one or more neighboring LAs  22  nearest the last cell used  32  are also paged along with the last registered LA  22 . However, the number of neighboring LAs  22  which are also paged is suitably less than the total number of LAs  22  neighboring the last registered LA  22 . In this way, paging channel bandwidth is conserved as compared to traditional LAC paging wherein all the LAs  22  neighboring the last registered LA  22  are paged along with the last registered LA  22 .  
         [0025]     Assuming that LA 5  is the last registered LA  22 , we shall consider the paging determinations made by an exemplary CLAC paging protocol in five different instances: (i) where the last used cell  32  is the cell labeled  1 ; (ii) where the last used cell  32  is the cell labeled  2 ; (iii) where the last used cell  32  is the cell labeled  3 ; (iv) where the last used cell  32  is the cell labeled  4 ; and, (v) where the last used cell  32  is the cell labeled  5 .  
         [0026]     In case (i), cell  1  is deemed sufficiently interior or centrally located within LA 5 , accordingly the CLAC paging protocol calls for the paging of LA 5  only. In case (ii), cell  2  is deemed sufficiently near or at the exterior boundary of LA 5 , accordingly the CLAC paging protocol calls for the paging of LA 5  along with the paging of those neighboring LAs sufficiently near and/or nearest cell  2 , i.e., LA 4  and LA 9  in this case. In case (iii), cell  3  is deemed sufficiently near or at the exterior boundary of LA 5 , accordingly the CLAC paging protocol calls for the paging of LA 5  along with the paging of those neighboring LAs sufficiently near and/or nearest cell  3 , i.e., LA 9  and LA 12  in this case. In case (iv), cell  4  is deemed sufficiently near or at the exterior boundary of LA 5 , accordingly the CLAC paging protocol calls for the paging of LA 5  along with the paging of those neighboring LAs sufficiently near and/or nearest cell  4 , i.e., only LA 12  in this case. In case (v), cell  5  is deemed sufficiently near or at the exterior boundary of LA 5 , accordingly the CLAC paging protocol calls for the paging of LA 5  along with the paging of those neighboring LAs sufficiently near and/or nearest cell  5 , i.e., LA 3 , LA 4  and LA 6  in this case.  
         [0027]     It is to be noted that LA 5  has a total of five neighboring LAs  22 , namely, LA 3 , LA 4 , LA 9 , LA 12  and LA 6 . In traditional LAC paging, all five of the neighboring LAs  22  would be paged regardless of the different instances proposed above. However, with a CLAC paging protocol as proposed herein, paging channel bandwidth is conserved by customizing the paging for different instances. The customized paging is selected so that less than all the neighboring LAs  22  are paged in any given instance (e.g., paging a minimum number of LAs  22 ), while optimizing a likelihood of paging the correct LA  22 , i.e., the one in which the sought MS  40  is located. For example, if the last used cell  32  where located within LA 5  nearer to LA 4  than LA 6 , it is a reasonable assumption that if the MS  40  is no longer in LA 5  it is more likely to have traveled to the closer LA 4  rather than the farther LA 6 . Accordingly, to conserve paging channel bandwidth while increasing the likelihood of the page actually reaching the MS  40 , it is beneficial to page LA 4  (i.e., the LA  22  in which the MS  40  is more likely to be found) and not page LA 6  (i.e., the LA  22  in which the MS  40  is less likely to be found).  
         [0028]     Of course, the CLAC paging protocol may vary across the network A depending on the relative arrangement of neighboring LAs  22  and/or the configuration of cells  32  within the LAs  22 . That is to say, the CLAC paging protocol is optionally tuned or otherwise adjusted to account for the particular layout of LAs, cells and/or other geographic considerations in a particular area. Suitably, for a given LA  22 , a look-up table (LUT) or the like is used to map a CLAC paging area to each cell  32  within that LA  22 . For example, a LUT for LA 5  would relate each cell  32  within LA 5  to a CLAC paging area including one or more LAs  22 . Accordingly, when the last registered LA  22  is LA 5 , the LUT for LA 5  is accessed. Using the accessed LUT for LA 5 , the last used cell  32  is used as an index to look-up the CLAC paging area for that cell  32 . Accordingly, the LAs  22  identified in the LUT as part of the CLAC paging area for the cell  32  are paged.  
         [0029]     Suitably, the CLAC paging protocol is employed in a multi-tiered or multi-level paging architecture. Each tier or level of the paging architecture represents one paging attempt. When an incoming call arrives for the MS  40  at the MSC  20 , paging attempts continue to progress through the levels or tiers in turn until the MS  40  responds to the page or the last level or tier is reached. At an optional first level or tier, the first paging attempt is suitably limited to paging only the last registered LA  22 . At an optional second level or tier, the second paging attempt suitably employs the CLAC paging protocol. At an optional third level or tier, the third paging attempt is suitably a traditional LAC page.  
         [0030]     It is to be appreciated that in connection with the particular exemplary embodiments presented herein certain structural and/or function features are described as being incorporated in defined elements and/or components. However, it is contemplated that these features may, to the same or similar benefit, also likewise be incorporated in other elements and/or components where appropriate. It is also to be appreciated that different aspects of the exemplary embodiments may be selectively employed as appropriate to achieve other alternate embodiments suited for desired applications, the other alternate embodiments thereby realizing the respective advantages of the aspects incorporated therein.  
         [0031]     It is also to be appreciated that particular elements or components described herein may have their functionality suitably implemented via hardware, software, firmware or a combination thereof. Additionally, it is to be appreciated that certain elements described herein as incorporated together may under suitable circumstances be stand-alone elements or otherwise divided. Similarly, a plurality of particular functions described as being carried out by one particular element may be carried out by a plurality of distinct elements acting independently to carry out individual functions, or certain individual functions may be split-up and carried out by a plurality of distinct elements acting in concert. Alternately, some elements or components otherwise described and/or shown herein as distinct from one another may be physically or functionally combined where appropriate.  
         [0032]     In short, the present specification has been set forth with reference to preferred embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the present specification. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.