CROSS-REFERENCE TO RELATED APPLICATION 
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     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
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     FIELD OF THE INVENTION 
     The present invention relates to communication networks, and more particularly to a method and apparatus for controlling mobility of a mobile station in a wireless communication network. 
     BACKGROUND OF THE INVENTION 
     As the demand for high speed broadband networking over wireless communication links increases, so too does the demand for different types of networks that can accommodate high speed wireless networking. For example, the deployment of Institute of Electrical and Electronics Engineers (“IEEE”) 802.11 wireless networks in homes and business to create Internet access “hot spots” has become prevalent in today&#39;s society. However, these IEEE 802.11-based networks are limited in bandwidth as well as distance. For example, maximum typical throughput from a user device to a wireless access point is 54 MB/sec. at a range of only a hundred meters or so. In contrast, while wireless range can be extend through other technologies such as cellular technology; data throughput using current cellular technologies is limited to a few MB/sec. Put simply, as the distance from the base station increases, the need for higher transmission power increases and the maximum data rate typically decreases. As a result, there is a need to support high-speed wireless connectivity beyond a short distance such as within a home or office. 
     As a result of the demand for longer range wireless networking, the IEEE 802.16 standard was developed. The IEEE 802.16 standards are often referred to as WiMAX or less commonly as WirelessMAN or the Air Interface Standard. These standards provide specifications for fixed broadband wireless metropolitan access networks (“MAN”s) that use a point-to-multipoint architecture (IEEE 802.16d) and combined fixed and mobile broadband wireless access system&#39;s (IEEE 802.16e). Such communications can be implemented, for example, using orthogonal frequency division multiplexing (“OFDM”) communication. OFDM communication uses a spread spectrum technique distributes the data over a large number of carriers that are spaced apart at precise frequencies. This spacing provides the “orthogonality” that prevents the demodulators from seeing frequencies other than their own. 
     The 802.16 standards support high bit rates in both uploading and downloading from a base station up to a distance of about 30 miles (about 50 km) to handle such services as VoIP, IP connectivity and other voice and data formats, e.g., time division multiplexing (“TDM”). Expected data throughput for a typical WiMAX network is 45 MBits/sec. per channel. The 802.16e standard defines a media access control (“MAC”) layer that supports multiple physical layer specifications customized for the frequency band of use and their associated regulations. This MAC layer uses protocols to ensure that signals sent from different stations using the same channel do not interfere with each other and “collide”. 
     The IEEE 802.16e air interface standard and corresponding WiMAX network architecture standard, as defined by the WiMAX forum, is primarily designed to support user/device mobility. Some network operators have readily available radio spectrum for deploying an 802.16e network; however, governmental regulations may restrict usage of these radio spectrums for supporting mobile wireless devices. In other words, although a network is fully compliant with the IEEE 802.16e standard and capable of supporting full mobility services for mobile wireless devices, government regulations require that the mobility services be either partially or completely restricted or unavailable to the wireless devices. It is therefore desirable to have methods and systems to prevent full or partial mobility support for IEEE 802.16e compliant wireless devices without requiring any changes to either the IEEE 802.16e standard, the Network Architecture as defined by the WiMAX Forum, the mobile devices themselves or the over the air control messages exchanged between the device and the network. 
     SUMMARY OF THE INVENTION 
     It is to be understood that both the following summary and the detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. Neither the summary nor the description that follows is intended to define or limit the scope of the invention to the particular features mentioned in the summary or in the description. 
     This invention provides a method, system and apparatus for controlling mobility on a wireless network, which includes retrieving a network mobility preference, the network mobility preference indicating a level of mobility service for the mobile station, the level of mobility service indicating the extent to which the mobile station can handoff among base stations of the wireless network, and establishing a level of mobility service for the mobile station based on the retrieved network mobility preference. 
     In accordance with one aspect, the present invention provides a method for controlling mobility on a wireless network, the method includes retrieving a network mobility preference, the network mobility preference indicating a level of mobility service for the mobile station, the level of mobility service indicating the extent to which the mobile station can handoff among base stations of the wireless network, and establishing a level of mobility service for the mobile station based on the retrieved network mobility preference. 
     In accordance with another aspect, the present invention provides an apparatus for controlling mobility on a wireless network, the apparatus includes a mobility disabling control module, the mobility disabling control module configurable to restrict mobility of a mobile station in the wireless network by using a network mobility preference to establish a level of mobility service for a mobile station based on the network mobility preference. 
     In accordance with yet another aspect, the present invention provides a gateway for controlling mobility on a wireless network, which includes a memory for storing data from corresponding to at least one network mobility preference; and a processor, the processor operates to receive a handoff request message from a network device, to analyze the handoff request message to determine a level of mobility service to assign to a mobile station and to establish a level of mobility service for the mobile station based on the network mobility preference. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the present invention, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein: 
         FIG. 1  is a block diagram of the network architecture of a communication network constructed in accordance with the principles of the present invention; 
         FIG. 2  is a block diagram of a first operational embodiment of the present invention; 
         FIG. 3  is a sequence diagram illustrating a mobile station initiated handoff process; 
         FIG. 4  is a sequence diagram illustrating a network (base station) initiated handoff process; 
         FIG. 5  is a sequence diagram illustrating a mobile station reactive handoff process; 
         FIG. 6  is a sequence diagram illustrating a location update process; 
         FIG. 7  is a sequence diagram illustrating a network initiated idle mode exit process; and 
         FIG. 8  is a sequence diagram illustrating a mobile station initiated idle mode exit process. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     This invention provides a method, system and apparatus for controlling mobility in a wireless network that deploys the air interface defined by the Institute of Electrical and Electronics Engineers (“IEEE”) 802.16e standard, and the corresponding worldwide interoperability for microwave access (“WiMAX”) network architecture standard as defined by the WiMAX Forum. 
     Referring now to the drawing figures in which like reference designators refer to like elements, there is shown in  FIG. 1 , a system constructed in accordance with the principles of the present invention and designated generally as “ 10 .” System  10  includes base stations  12  (“BS”) and mobile stations  14  (“MS”). Base stations  12  engage in wireless communication with mobile stations  14 . Similarly, mobile stations  14  engage in wireless communication with base stations  12 . 
     Base station  12  can be any base station arranged to wirelessly communicate with mobile stations  14 . Base stations  12  include the hardware and software used to implement the functions described herein to support the MAC control plane functions. Base stations  12  include a central processing unit, transmitter, receiver, I/O devices and storage such as volatile and nonvolatile memory as may be needed to implement the functions described herein. 
     Mobile stations  14  can be any mobile station including but not limited to a computing device equipped for wireless communication, cell phone, wireless personal digital assistant (“PDA”) and the like. Mobile stations  14  also include the hardware and software suitable to support the MAC control plane functions needed to engage in wireless communication with base station  12 . Such hardware can include a receiver, transmitter, central processing unit, storage in the form of volatile and nonvolatile memory, input/output devices, etc. 
       FIG. 2  shows system  10  with an access service network gateway  18  (“ASN GW”) in communication with base stations  12 A,  12 B in accordance with the principles of the invention (base stations  12 A and  12 A are referred to collectively herein as “base stations  12 ”). The ASN GW  18  provides an aggregation of control plane functions, e.g., mobility, in addition to performing bearer plane routing or bridging functions. The ASN gateway  18  includes the hardware and software suitable to support the MAC control plane functions used to engage in communication with base stations  12 . Such hardware can include protocol translators, impedance matching devices, rate converters, fault isolators, or signal translators as necessary to provide system interoperability. More importantly, the ASN GW  18  provides a number of options for allowing mobility between base stations  12 . For example, ASN GW  18  allows system operators to select “no mobility” “partial mobility” and “full mobility” options, which are selectable at the ASN GW level to restrict or control mobility support for IEEE 802.16e compliant wireless mobile stations  14 . These options are functionally implemented within ASN GW  18  as described below. 
     In another embodiment, it may be desirable to restrict mobility from any base station to any other base station. Other examples of restricting mobility would include but are not limited to restricting mobility to groups of base stations (e.g., paging groups) with no particular geographical significance, or for those base stations within certain geographical boundaries. Additionally, mobility may be restricted based on “no-mobility” being explicitly configured on the mobility disabling control module. Other examples of criteria for no mobility would be time of day constraints, network (or base station) load, users subscription profile, and the like. 
     As shown in  FIG. 2 , mobile station  14  engages in bidirectional communication with base stations  12 , which have overlapping coverage regions  22 A,  22 B respectively. The ASN GW  18  supports interfaces such as the WiMAX network reference architecture R6 interfaces, which implement a set of control and bearer plane protocols for communication between the base stations  12  and the ASN GW  18 . The bearer plane includes an intra-ASN data path or inter-ASN tunnel between the base stations  12  and the ASN GW  18 . The control plane includes protocols for IP tunnel management (establish, modify and release) in accordance with the mobile station  14  mobility events. The ASN GW  18  to base stations  12  interface may also serve as a conduit for exchange of media access control (“MAC”) layer state information between neighboring base stations  12 . The ASN GW  18  to mobile station  14  interface may include additional protocols related to the management plane. 
     In this embodiment, a mobility disabling control module  20  (“MDC”) is coupled to the ASN GW  18  and provides the communications network system  10  with the capability to control the mobility service by implementing employing a MAC layer 2 handoff manager on the ASN GW  18 . For example, when there is a requirement that mobility be fully restricted in communications network system  10 , the layer 2 handoff manager is notified by the MDC module  20  that mobility is to be disabled, and the handoff manager of ASN GW will reject any handoff requests from mobile station  14 , base stations  12  and or both mobile station  14  and base stations  12 . In this way, the MDC module  20  provides a configurable feature that can control the decision-making process associated with the handoff manager of the ASN GW  18 . In other words, the MDC module  20  can be seen as providing a way to implement a configurable mobility preference that indicates a level of mobility service a mobile station  14  is to have in a particular network. The MDC module  20  can be a software implementation, a hardware implementation or a combination of both. 
     Many of the functional units described in this specification have been labeled as modules, in order to more particularly emphasize their implementation independence. For example, a module may be implemented as a hardware circuit comprising custom circuits or gate arrays, off-the-shelf semiconductors such as logic chips, transistors, or other discrete components. A module may also be implemented in programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices or the like. 
     Modules may also be implemented in software for execution by various types of processors. An identified module of executable code may, for instance, comprise one or more physical or logical blocks of computer instructions, which may, for instance, be organized as an object, procedure, or function. Nevertheless, the executables of an identified module need not be physically located together, but may comprise disparate instructions stored in different locations which, when joined logically together, comprise the module and achieve the stated purpose for the module. 
     A module of executable code could be a single instruction, or many instructions, and may even be distributed over several different code segments, among different programs, and across several memory devices. Similarly, operational data may be identified and illustrated herein within modules, and may be embodied in any suitable form and organized within any suitable type of data structure. The operational data may be collected as a single data set, or may be distributed over different locations including over different storage devices. 
     An operational embodiment of the present invention is described with reference to  FIG. 3 .  FIG. 3  illustrates a timing diagram of a mobile station  14  initiated handoff in an access service network (“ASN”) that has had mobility disabled. The source or serving base station  12 A (“SBS”) and the target base station  12 B (“TBS”) are in communication with the ASN GW  18 . The mobile station  14  initiates the handoff process by sending a handoff request message, such as the IEEE 802.16e defined MOB_MSHO-REQ to its current SBS  12 A, indicating a list of potential base station(s) to which the mobile station  14  seeks a handoff (Step S 100 ). SBS  12 A receives the handoff request from mobile station  14  and sends a handoff request, such as the WiMAX networking group (“NWG”) defined R6_HO-REQ to the layer 2 handoff manager of ASN GW  18  (Step S 102 ). Because mobility is disabled on ASN GW  18 , the handoff manager on the ASN GW  18  rejects the handoff request from serving base station  12 A by sending a response message, such as WiMAX NWG defined R6_HO-RSP to the serving base station  12 A. The rejection can be communicated to serving base station  12 A by omitting to include any recommended base station in the response message (e.g., R6_HO-RSP) and/or by using an explicit reject type-length-value (“TLV”) element in the message (Step S 104 ). At Step S 108 , the serving base station  12 A responds to the mobile station  14  with a message, e.g., an IEEE 802.16e defined MOB_BSHO-RSP message indicating that the handoff to selected base station  12 B is not recommended, e.g., with mode equal to “0b111”. At this point, the mobile station  14  may reconfigure the base station list and sent another mobility handoff request, such as the IEEE 802.16e defined MOB_MSHO-REQ. 
     Referring to  FIG. 4 , with respect to serving base station  12 A, the serving base station  12 A initiates a handoff request for mobile station  14 , such as the WiMAX NWG defined R6_HO-REQ to the layer 2 handoff manager of ASN GW  18  (Step S 110 ). Since mobility is disabled on ASN GW  18 , the handoff manager on the ASN GW  18  rejects the handoff request by sending a corresponding rejection message such as the WiMAX NWG defined R6_HO-RSP response to the serving base station  12 A. The rejection can be communicated to serving base station  12 A by omitting to include any recommended base station data in the rejection message (R6_HO-RSP) and/or by using an explicit reject TLV element in the message (Step S 112 ). Since the handoff response message from the ASN-GW  18  (e.g., R6_HO-RSP response) signaled a rejection, the serving base station  12 A will not initiate a network handoff by sending an appropriate message, e.g., an IEEE 802.16e defined MOB_BSHO-REQ. Alternatively, the MDC module  20  can be configured to provide partial disablement of mobility service conditioned upon which network element initiates the handoff request. For example, in the event that the mobile station  14  initiates a handoff request, then mobility is always disabled, however, if a base station  12 A,  12 B initiates the handoff request, then the layer 2 handoff manager of ASN GW  18  will permit the handoff to occur. 
     Referring to  FIG. 5 , with respect to mobile station  14 , the mobile station  14  initiates a reactive handoff request by sending a ranging request, e.g., the IEEE 802.16e defined RNG-REQ message, to a target base station  12 B (Step S 120 ). In this case, the ranging request is sent to indicate the mobile station&#39;s re-entry into the network  10 . The target base station  12 B sends a context request message, e.g., the WiMAX NWG defined Context-REQ, to ASN GW  18  and requests the mobile station&#39;s context information (Step S 122 ). Because mobility is disabled on the system  10 , the ASN GW  18  replies with a context response without including any of the context information (Step S 124 ) for mobile station  14 . At Step S 126 , the target base station  12 B sends a context acknowledgement message, e.g., the WiMAX NWG defined Context-ACK, to acknowledge the context-response from ASN GW  18 . When the ASN GW  18  receives a context acknowledgement message, such as the WiMAX NWG defined Context-ACK, an “accounting stop” can be sent to an AAA accounting server (not shown) to stop additional charges by the previous base station  12  to the mobile station  14  account. Upon receiving the context response message without the mobile station  14  context information, target base station  12 B sends a ranging response message, such as the IEEE 802.16e defined RNG-RSP to the mobile station  14  (Step S 128 ). Since the base station  12 B did not receive any mobile station  14  context information, it can neither include any connection identifier (“CID”) update message, e.g., CID-UPDATE TLV, in the ranging response nor handoff optimization messages e.g., TLVs to the mobile station  14 . As a result, the mobile station  14  is unable to conduct a mobile handoff to the target base station  12 B and the call terminates. This means that in order for mobile  14  to establish network connectivity it must perform a full network reentry. Accordingly, once mobile station  14  receives the ranging request (RNG-RSP) from the base station  12 B, and that ranging request is without any optimization TLV or a CID-UPDATE TLV, the mobile station  14  will perform network entry procedures. 
     In general, the procedures that a mobile station  14  performs when entering a network includes performing basic capability negotiations via the exchange of subscriber station basic capability (“SBC”) request and SBC response with the network. Next, authentication and authorization of the mobile station  14  is performed and the exchange of registration request and registration response with the network is completed. A negotiation for security keys occurs and the network can set up the service flows, which are the connections by which information packets are transmitted and received to complete the entry procedures (Step S 130 ). At Step S 132 , the re-entry into the system  10  by mobile station  14  is complete. 
     Referring to  FIG. 6 , with respect to mobile station  14 , the mobile station  14  is forced to perform a full network re-entry from idle mode if location update (“LU”) is performed via a base station other than the base station through which the mobile station either entered idle mode or performed a successful location update.  FIG. 6  illustrates a mobile station  14  initiating a location update by sending a ranging request, e.g., RNG-REQ to a target base station  12 B (Step S 140 ). The target base station  12 B sends a location update request message, e.g., LU-REQ, to the paging controller of the ASN GW  18  and requests location update (Step S 142 ). Because mobility is disabled on the network and the location update request is coming from a new base station  12 B, the ASN GW  18  paging controller replies with a location update response without any of the context information for mobile station  14  (Step S 144 ). Upon receiving the location update response without mobile station  14  context information, target base station  12 B sends a ranging response message, e.g., RNG-RSP message to the mobile station  14  indicating that location update failed, e.g., location update response equal to “failure” (Step S 146 ). At Step S 148 , the target base station  12 B sends a location update confirmation, e.g., LU-Confirm to acknowledge the LU-response from paging controller of ASN GW  18 . Once mobile station  14  receives the ranging response message, e.g., RNG-RSP without any handoff optimization TLV, the mobile station  14  will perform all network entry procedures as discussed previously with respect to  FIG. 5  and Step S 130 . At Step S 150 , the mobile station  14  can send a subscriber base station capabilities request, e.g., SBC-REQ to commence the network re-entry process. 
     Referring to  FIG. 7 , with respect to mobile station  14 , the mobile station  14  is forced to perform a full network re-entry from idle mode if the network initiates a network idle mode exit page in order to transmit a downlink packet received on behalf of the idle mobile station  14 , when the mobile station  14  has moved into a coverage area of a new base station  12 B.  FIG. 7  illustrates an ASN GW  18  initiating a paging announcement to all base stations  12  in mobile station&#39;s  14  current paging group without any of mobile station&#39;s  14  context information (Step S 160 ). The serving and target base stations  12  receiving the paging announcement will page the mobile station  14  by sending out a mobile paging advertisement, e.g., MOB_PAG-ADV, to the mobile station  14  to inform it to re-enter the network (Step S 162 ). Mobile station  14  re-enters the network at one of the base stations  12  by sending a ranging request, e.g., RNG-REQ with ranging purpose set to re-entry from idle mode (Step S 164 ). New serving base station  12 B sends a context request e.g., CONTENT-REQ to obtain mobile station&#39;s  14  context from the paging controller (“PC”) of ASN GW  18  (Step S 166 ). Since mobility is disabled by the ASN GW  18 , the paging controller determines that mobile station  14  has moved to a different base station  12 B and sends a Context-Response without any of mobile station&#39;s context information (Step S 168 ). Upon receiving the location update response without mobile station&#39;s  14  context information, at Step S 170 , new serving base station  12 B sends a ranging response message, e.g., RNG-RSP message without any handoff optimization TLV or CID-UPDATE TLV to the mobile station  14  informing the mobile station  14  to perform all network entry procedures as discussed previously with respect to  FIG. 5  and Step S 130 . At Step S 172 , the new serving base station  12 B sends a content acknowledgement message, e.g., CONTENT-ACK, to acknowledge the content response from paging controller of ASN GW  18 . At Step S 174 , the mobile station  14  will perform all network entry procedures as discussed previously with respect to  FIG. 5  and Step S 130 . At Step S 176 , the mobile station&#39;s  14  re-entry into the network is complete. 
     Referring to  FIG. 8 , with respect to mobile station  14 , the mobile station  14  is forced to perform a full network re-entry when the mobile station  14  attempts idle mode exit via a base station  12 B other than the one at which the mobile station  14  either entered idle mode or performed a successful location update.  FIG. 8  illustrates a mobile station  14  initiating a location update by sending a ranging request, e.g., RNG-REQ, to a target base station  12 B indicating intention to re-enter the network from the idle mode (Step S 180 ). The target base station  12 B sends a context request message, e.g., CONTEXT-REQ, to the ASN GW  18  and requests context information (Step S 182 ). Because mobility is disabled on the network and the context request is coming from a new base station  12 B, the ASN GW  18  paging controller replies with a context response (“CONTEXT-RESPONSE”) without any of the mobile&#39;s context information (Step S 144 ). Upon receiving the context response without mobile station  14  context information, target base station  12 B sends a ranging response, e.g., RNG-RSP message to the mobile station  14  without the handoff optimization TLV and CID-UPDATE TLV (Step S 16 ). At Step S 148 , the target base station  12 B sends a context acknowledgement message, e.g., Content-ACK, to acknowledge the Content-response from paging controller of ASN GW  18 . Once mobile station  14  receives the ranging response, e.g., RNG-RSP without any handoff optimization TLV, the mobile station  14  will perform all network entry procedures as discussed previously with respect to  FIG. 5  and Step S 130 . At Step S 190 , the mobile station  14  will perform all network entry procedures as discussed previously with respect to  FIG. 5  and Step S 130 . At Step S 192 , mobile station&#39;s  14  re-entry into the network is complete. 
     The present invention advantageously provides a method, system and apparatus for restricting full or partial mobility support for IEEE 802.16e compliant wireless devices without requiring any changes to the IEEE 802.16e standard, the Network Architecture as defined by the WiMAX Forum or the over the air control messages exchanged between the wireless device and the network by employing a mobility disabling control module. By employing this improved mobility disabling control scheme, the communication network operator can comply with governmental regulations without having to revert to costly replacement systems. Of course, it is understood that the present invention is not limited to IEEE 802.16e compliant wireless networks and that the invention can be implemented in any wireless network that includes the ability to hand off communications with a wireless device among different base stations. 
     The present invention can be realized in hardware, software, or a combination of hardware and software. An implementation of the method and system of the present invention can be realized in a centralized fashion in one computing system or in a distributed fashion where different elements are spread across several interconnected computing systems. Any kind of computing system, or other apparatus adapted for carrying out the methods described herein, is suited to perform the functions described herein. 
     A typical combination of hardware and software could be a specialized or general-purpose computer system having one or more processing elements and a computer program stored on a storage medium that, when loaded and executed, controls the computer system such that it carries out the methods described herein. The present invention can also be embedded in a computer program product, which comprises all the features enabling the implementation of the methods described herein, and which, when loaded in a computing system is able to carry out these methods. Storage medium refers to any volatile or non-volatile storage device. 
     Computer program or application in the present context means any expression, in any language, code or notation, of a set of instructions intended to cause a system having an information processing capability to perform a particular function either directly or after either or both of the following a) conversion to another language, code or notation; b) reproduction in a different material form. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. Significantly, this invention can be embodied in other specific forms without departing from the spirit or essential attributes thereof, and accordingly, reference should be had to the following claims, rather than to the foregoing specification, as indicating the scope of the invention. 
     It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described herein above. A variety of modifications and variations are possible in light of the above teachings without departing from the spirit or essential attributes thereof, and accordingly, reference should be had to the following claims, rather than to the foregoing specification, as indicating the scope of the of the invention.
This invention provides a method, system and apparatus for controlling mobility on a wireless network, which includes retrieving a network mobility preference, the network mobility preference indicating a level of mobility service for the mobile station, the level of mobility service indicating the extent to which the mobile station can handoff among base stations of the wireless network, and establishing a level of mobility service for the mobile station based on the retrieved network mobility preference. The method and apparatus may further include determining the level of mobility service for the mobile station to be fully or partially restricted based on the mobility preference.