PATENT ABSTRACT
A method of establishing call termination to a mobile station of a called subscriber in a fixed wireless communication network which can be only allowed to receive call terminations in one of its HomeZones. The identification and location of the MS is ascertained prior to routing a call to the switching center serving the MS. The radio link between the serving switching center and the MS is maintained and used to terminate a call if the MS is determined to be within a HomeZone. The present invention eliminates the need to page a MS twice thereby speeding up the call termination. The MS provides its location area code and Cell ID to the serving/visited mobile switching center to facilitate the SCP identifying the MS&#39;s location prior to routing the call termination to the MS. The HomeZone call may be routed to a mobile station voicemail if it is determined to be outside its HomeZones, or, terminated to the mobile station but at a higher wireless billing rate.

PATENT DESCRIPTION
This application claims priority under 35 USC § 119 (e) (1) of provisional application Ser. No. 60,064,309, filed Nov. 5, 1997. 
    
    
     FIELD OF THE INVENTION 
     The present invention is generally related to wireless communications systems, and more particularly to fixed wireless systems provided with HomeZone service whereby subscribers are provided communications service, and billed accordingly, depending on whether or not a subscriber&#39;s mobile station (MS) is located within one of its designated HomeZones. 
     BACKGROUND OF THE INVENTION 
     The implementation of wireless communications systems throughout the world is growing rapidly. This can be seen by the extensive sales and marketing of mobile cellular phone service throughout North America as well as the rest of the World. Existing and emerging technologies include AMPS, TDMA, CDMA, and GSM just to name a few. In these systems, a subscriber of an MS is typically billed for calls at a rate determined by a plan contracted to by the subscriber of the MS, whereby the rate per minute may be based on the time of day, the amount of use and the geographical location of the MS during a call. 
     Another emerging wireless communication system is known as a fixed wireless system. In many parts of the world including Europe and Asia, subscribers are being provided with wireless communication transceivers e.g. mobile stations as their primary communication device for use within a residence, business and other defined locations. These fixed wireless transceivers are specially suitable where wireline services are to date not available, inadequate, or exceptionally expensive to install. With the decreasing cost of wireless transceivers and supporting infrastructure, those places of the world in need of new or upgraded communication systems are finding fixed wireless systems as economically attractive and versatile solutions. 
     In fixed wireless communication systems, a subscriber&#39;s mobile station is assigned to one or more HomeZones. Each HomeZone defines a geographical home area in which the wireless mobile station is to receive and originate wireless calls at a predetermined low billing rate. While it is primarily intended that a subscriber will primarily use its mobile station within the HomeZone areas, these mobile stations may be transported by a subscriber outside the HomeZone calling areas and may be allowed to originate or receive calls outside the HomeZone area at another predetermined billing rate. 
     The HomeZone service allows telecommunications providers to define the HomeZone calling areas for their MSs, where the tariff for calls originated and terminated in one of the HomeZones is different than the regular wireless tariff. The HomeZone service is attractive for telecommunications providers wanting to offer both fixed wireless and wireless services to subscribers over one mobile phone. One of the significant costs in providing wireline services is laying copper to each subscribers home. HomeZone service eliminates this cost by using wireless systems which don&#39;t require the cost of laying copper. The HomeZone service allows the provider to charge subscribers a particular tariff when they use their mobile station in one of their HomeZones at their wireline rate, and at another tariff when they use their mobile station outside their HomeZones at their wireless rate. The wireline rate is usually less expensive than the wireless rate. This attractive to consumers because they are charged the same low rates in their Homezone as they would have been charged by a wireline provider but without the hassle of multiple phones bills. 
     As part of the HomeZone feature, on call termination, the location of the mobile station must be determined before the call is routed to the network access element, such as a visitors mobile switching center (VMSC), currently serving the mobile station, so that the network can potentially disallow or reroute the termination if the subscriber&#39;s mobile station is not in one of is HomeZones. There is a need to provide a method for determining whether a mobile station is located in one of its HomeZones, and also a method for speeding up the potential termination to the mobile station that may follow. 
     SUMMARY OF THE INVENTION 
     The present invention achieves technical advantages as a method of establishing call termination to a called mobile station in a wireless communication network which can be only allowed to receive call terminations in one of its HomeZones by determining the mobile station&#39;s location and identity before completing a call termination to the network access element currently serving the mobile station. 
     In the preferred embodiment of the present invention, the method comprises first determining if a call termination received by a wireless communication network is a HomeZone type call. This may be done, for instance, at a gateway MSC by identifying prefix digits attached to the call. Upon determining that the call termination is a HomeZone type call, the location of the called mobile station to the cell level is first identified in the wireless communication network before routing the call termination to a network access element currently serving the mobile station. It is then determined if the identified location (e.g. serving cell of the mobile station) is within one of the mobile station&#39;s HomeZones. If the mobile station&#39;s location is determined to be within one of the mobile station&#39;s HomeZones, then the call termination is routed to the network access element currently serving the mobile station, and the call termination is completed to the mobile station by the network access element currently serving the mobile station. Preferably, the network access element comprises an MSC, but could comprise other equivalent network devices. If the mobile station is determined to be outside its HomeZones, the call may be routed by the network to the mobile stations voicemail, or to an associated wireless phone number and billed accordingly. 
     According to the present invention, a mobile station radio link is established between the MSC currently serving the mobile station and the mobile station during the mobile station location process, wherein the call termination is completed to the mobile station on the same mobile station radio link. The radio link is preferably established by sending a PSI message from a HLR to the MSC currently serving the mobile station and paging the mobile station, whereby the mobile station then responds to the page with a page response to the serving MSC. If the mobile station is currently on a call, the location of the MS is known to the serving MSC and is returned to the HLR. If a subsequent termination arrives at the serving MSC, then the call termination to the mobile station is completed if the MS is configured to receive multiple calls e.g. call waiting, without establishing a new radio link between the MSC serving the mobile station and the mobile station. 
     A PAGE_RESPONSE message which includes the mobile station&#39;s identity is generated in response to the page message by the mobile station. The identity included in the PAGE_RESPONSE message comprises preferably either the mobile station&#39;s International Mobile Subscriber Identity (IMSI) or Temporary Mobile Subscriber Identity (TMSI). If the response contains the TMSI, the TMSI is used by the serving MSC to find the IMSI. The page response also includes the mobile station&#39;s current Cell ID and the mobile station&#39;s current location area code (LAC). The mobile station&#39;s identity, LAC, and Cell ID are all sent by the MSC serving the mobile station to the home location register (HLR) of the mobile station. The mobile station&#39;s identity, LAC and Cell ID are then sent to a service control point (SCP) of the wireless communication network. The SCP determines if the mobile station is in one of the mobile station&#39;s HomeZones. If the SCP determines the mobile station is in one of its HomeZones, the SCP notifies the gateway MSC of the wireless communication network to complete the call termination to the mobile station. If the mobile station is determined to be outside its HomeZones, the call may be routed by the SCP to the mobile station&#39;s voicemail, or to an associated wireless phone number and billed accordingly. 
     The present invention achieves technical advantages by determining the location of the mobile station to the cell level before the call is routed to the serving MSC, and speeding up the potential call termination to the mobile station that may follow. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring now to FIG. 1, there is illustrated a typical fixed wireless communication network generally which is well suited to benefit from the method of the present invention; and 
     FIG. 2 is flow diagram of a method of identifying a mobile station location to provide HomeZone service according to the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIG. 1, there is generally shown at  10  a typical fixed wireless communication network which is adapted to provide HomeZone service according to the method of the present invention. The network  10  is seen to comprise a fixed network  12  which may comprise a public switched telephone network (PSTN), a gateway mobile switching center (GMSC)  14  and a subscriber switching center  16  which may be a MSC, serving a wireless mobile station (MS)  18  via a base switching station (BSS)  20 . MS  18  is seen to be assigned to one or more HomeZone location areas, one HomeZone area generally shown at  22 , which may be one geographic cell area served by BSS  20 . Associated with the serving/visited switching center MSC  16  is a visitors location register (VLR)  26 . A home location register (HLR)  30  is assigned to handle all of the MS  18  information, including the address of the MSC currently serving the MS, service capabilities, etc. A service control point (SCP)  32  interfaces with the GMSC  14  and HLR  30 . 
     The present invention provides a method to determine if the MS  18  subscribing to a HomeZone service is in one of its HomeZones  22  before routing a call termination to the network access element  16  serving the MS, such as MSC  16 . One HomeZone  22  may be a subscriber&#39;s office, another HomeZone  22  may be a subscriber&#39;s home and so forth. The present invention allows the network  10  to potentially disallow the termination of a call to the MS  18  if the MS is not in one of its HomeZones  22 . The present invention also provides a method to precisely determine the MS&#39;s location. In addition, the present invention speeds up the potential termination to the MS that may follow by using the same radio link in the call termination that was used to find the mobile stations location. 
     By way of illustration, but without limitation to the specific implementation that will soon be described, reference is made to the network of FIG.  1  and the message flow of FIG. 2 which illustrates the preferred embodiment of the present invention to provide the HomeZone feature. The present invention is illustrated and described in considerable detail to provide an understanding of implementation and use of the present invention. It is to be understood that some of the basic elements of the network  10  can be substituted with other equivalent network elements to provide the intended function. For instance, the gateway MSC (GMSC)  14  can be substituted with other network access elements e.g. routers, depending on the technology implementing the HomeZone feature. The present invention is ideal for implementation in a GSM network, but can function in other types of networks as well. 
     With reference to FIG. 1, upon a call termination from the fixed network  12  to GMSC  14 , the GMSC  14  determines if the called number is a HomeZone type number. This is preferably done by ascertaining call data e.g. prefix digits provided with a call termination from the fixed network  12 , although other methods are possible. The GMSC  14  then queries the SCP  32  to determine if the termination is allowed to the intended MS  18 . To determine this, the SCP  32  then queries the HLR  30  to find the location of the MS  18 , and specifically, to determine if the MS  18  is located in one of its assigned HomeZones  22 . The HLR  30  then queries the MSC  16  known by the HLR  30  to be currently servicing the MS  18 , whereby the serving MSC  16  will page the MS  18 . The MS  18  responds to the page with a PAGE_RESPONSE message including its exact location including its current location area code (LAC) and current Cell ID, which is known by the mobile station based on broadcast messages by the serving cell. It is noted that the serving MSC  16  will know the LAC that the MS is located in, before paging, but the LAC is not enough information for the SCP to determine if the MS is in one of its HomeZones  22 . The PAGE_RESPONSE message also includes the mobile station identify, comprising the mobile station International Mobile Subscriber identify (IMSI) or Temporary Mobile Subscriber Identify (TMSI). If the response includes the TMSI, the TMSI is used by the serving MSC to determine the IMSI. 
     The MS  18  will provide a page response containing its LAC and Cell ID to the serving MSC  16 , which information is then sent to the HLR  30  by the serving MSC  16  for that MS  18 . The HLR  30  then sends the LAC and Cell ID to the SCP  32 , which then instructs the GMSC  14  if and how to route the call to the MS  18 . For example, if the SCP  32  determines the MS  18  is in one of its HomeZones  22 , the call will be terminated to the MS  18 . If, however, the MS  18  is determined to be outside its HomeZones  22 , the call may be forwarded to the voicemail associated with MS  18 , or, terminated to an associated wireless phone number, e.g. MSISDN number, associated with the MS  18  wherein the subscriber is billed at the wireless rate, which is usually higher than the wireline rate. 
     After sending the MS LAC and Cell ID location information back to the SCP  32  via the HLR  30 , it is specifically noted that the serving MSC  16  leaves the radio link (RR) connection up in anticipation of a reception of a call termination for that MS  18 . A timer at serving MSC  16  having a predetermined stop time e.g. 3 seconds is started at the serving MSC  16  once the MS LAC and Cell ID information has been sent to the HLR upon receiving the PAGE_RESPONSE message from the mobile station  18 . If a call termination does not arrive to the serving MSC  16  within the specified time, the established RR connection is then cleared by the serving MSC  16 . However, if the call termination does arrive within the predetermined time, the RR connection established between MSC  16  and MS  18  when the location of the MS was determined is then used. Thus, the MS  18  does not need to be paged again. The present invention achieves technical advantages by providing a significant improvement in time and processing over the prior art. The call set up time is improved by not having to page the MS again, by re-using the RR connection that was set up when the location of the MS was first determined. 
     To more fully understand the preferred embodiment for providing the present invention, reference is now made to the preferred message flow diagram in FIG.  2 . The steps illustrated in FIG. 2 correspond to the message number illustrated in FIG.  1 . Again, this specific implementation is preferred, although variations are possible and covered by the present invention. 
     At step  1 , the GMSC  14  is seen to receive an incoming call termination seen as an Initial Address Message (IAM) from the PSTN  12 . The GMSC  14  then determines if this call termination is to be a HomeZone termination. This is determined by ascertaining a call data e.g. prefix digits provided at the beginning of the call termination which identifies the type of call. At step  2 , the GMSC  14  initiates a query message to the SCP  32  by sending an InitDP message. At step  3 , the SCP  32  initiates identifying the location of the mobile station  18  by sending an AnyTimeIntegration message (ATI) to the HLR  30 . 
     At step  4  the HLR  30  requests the called MS&#39;s location from the VLR  26  associated with the serving MSC  16  using the Provide MS Information (PSI) message. 
     At step  5 , if the mobile station  18  is not on a call, the visited MSC  16  serving the mobile station  18  pages the mobile station  18  to ascertain its location. At step  6 , the mobile station  18  responds to this page with a PAGE_RESPONSE message to the serving MSC  16  containing its Location Area Code (LAC) and its Cell ID. In this regard, the present invention uses the PSI message in a novel way to trigger the serving MSC  16  to ascertain the MS  18  location. The MSC  16  starts the 3 second timer upon receipt of the PAGE_RESPONSE message, and leaves the established radio link to the MS  18  up in anticipation of an imminent call termination. 
     At step  7 , the VLR  26  sends this LAC and Cell ID to the HLR  30  in a PSI response message. In step  8 , the HLR  30  forwards the LAC and Cell ID information to the SCP  32  using an ATI Response message. 
     At step  9 , based on the specific location information received, the SCP  32  determines if the mobile station  18  is in one of its Home Zone&#39;s  22 , or if it is outside the HomeZones  22 . 
     At step  10 , if the SCP  32  determines in step  9  that the mobile station  18  is in one of its HomeZones  22 , the GMSC  14  sends a Send Routing Info (SRI) message to the HLR  30 . If the SCP  32 , however, determines the MS  18  is out of its HomeZones, the call is either terminated to the voicemail of the MS  18  at the wireline rate, or terminated to the MS  18  but at the wireless rate. The servicing MSC  16  handles billing of the call. 
     At step  11 , the HLR  30  responds to the GMSC  14  with a subscriber MS Roaming Number (MSRN) for the terminating mobile station  18  in the SRI ACK message. The MSRN number is generated by the serving MSC  16  and is included in the PRN ACK message per the GSM standard. At step  12 , the GMSC  14  then sends an IAM message to the visited MSC  16 . 
     At step  13 , the visited MSC  16  terminates the call as normal, except that the Paging is skipped since it has already been done earlier in step  5 , as long as the timer at MSC  16  has not expired. The existing radio link established with MS  18  in step  5  is used. As a result, the Authentication Request message is the first message sent, if authentication is required, to the mobile station  18  after the IAM message is received from the GMSC  14 . 
     The forgoing message flow as described with reference to FIG. 2 in view of FIG. 1 is the preferred implementation of the present invention, however, limitation to these specific messages is not to be inferred by the present invention. The present invention encompasses identifying if a MS is in one of its HomeZones prior to routing a call termination to the serving switching center for the mobile station, and using an existing RR connection to eliminate paging a mobile station a second time if a call termination is to be established. A timer is utilized at the switching center serving the MS, upon which the expiration of the timer of the RR connection is released. 
     Though the invention has been described with respect to a specific preferred embodiment, many variations and modifications will become apparent to those skilled in the art upon reading the present application. It is therefore the intention that the appended claims be interpreted as broadly as possible in view of the prior art to include all such variations and modifications.