Patent Publication Number: US-2007105600-A1

Title: Techniques to communicate information between foreign agents and paging controllers

Description:
BACKGROUND  
      Wireless communication systems exist today to enable electronic devices, e.g., computers, mobile devices, and/or personal communication devices, to communicate and exchange information such as voice and multimedia information (e.g., video, audio and data). The information may be communicated in accordance with a number of different wireless protocols, such as the Institute of Electrical and Electronics Engineers (IEEE) standards including the 802.11 standards for Wireless Local Area Networks (WLANs) and the 802.16 standards for Wireless Metropolitan Area Networks (WMANs), for example.  
      In the context of mobile broadband wireless access (MBWA) systems, wireless communication systems may operate in accordance with protocols and standards that comply with the IEEE 802.16 series of protocols, such as the Worldwide Interoperability for Microwave Access (WiMAX), for example. WiMAX is a wireless broadband technology based on the IEEE 802.16 standard of which IEEE 802.16-2004 and the 802.16e amendment are Physical (PHY) layer specifications. The WiMAX standards-based wireless technology may provide higher-throughput broadband communications over longer distances. WiMAX can be used for a number of applications, including “last mile” wireless broadband connections, hotspots, cellular communications, and high-speed enterprise connectivity for business.  
      Future wireless communication systems that support broadband wireless access technologies such as the IEEE 802.16 series of standards may need to support and manage the operations of the wireless electronics devices throughout the wireless communication system known in the art as mobile stations. Management may include communicating information used for paging between network nodes, location information update for certain mobile stations, paging mobile stations, delivering data to mobile stations, and so forth. As the number of mobile stations increase, however, so does the complexity and cost of such management operations. Consequently, there may be a need for improvements in managing mobile stations to solve these and other problems. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1A  illustrates one embodiment of a communications system.  
       FIG. 1B  illustrates one embodiment of subnets for a communications system.  
       FIG. 2  illustrates one embodiment of a processing system.  
       FIG. 3  illustrates one embodiment of a first message flow.  
       FIG. 4A  illustrates one embodiment of a second message flow.  
       FIG. 4B  illustrates one embodiment of an alternative second message flow.  
       FIG. 5  illustrates one embodiment of a third message flow.  
       FIG. 6  illustrates one embodiment of a logic flow.  
    
    
     DETAILED DESCRIPTION  
      Wireless communication standards include an “idle mode operation” for mobile stations that are not currently involved in active communications. The idle mode operation of mobile stations reduces their battery power consumption. Mobile stations that are in idle mode are tracked by a communications system using paging and location update procedures. The location update may be carried out to update the location of idle mode mobile stations as they move around in a communications system. Paging may be used to, for example, determine the location of a particular idle mode mobile station in a communications system and to deliver voice or data packets destined for that mobile station.  
      Various embodiments may generally relate to managing idle mode operations in support of paging and data delivery operations for idle mode mobile stations distributed throughout a MBWA system. The MBWA system may be arranged to operate or communicate in accordance with various wireless protocols and standards, such as one or more of the IEEE 802.16 series of protocols (WiMAX), for example. Although some embodiments may be described in the context of a MBWA system using one or more WiMAX protocols by way of example, it may be appreciated that other communication protocols may also be used as desired for a given implementation. The embodiments are not limited in this context.  
      More particularly, various embodiments may be directed to techniques for communicating information between various nodes of the MBWA system. For example, the MBWA system may be deployed with multiple functional entities referred to as foreign agents. The location information of idle mode mobile stations is maintained by one or more paging controllers. The foreign agents may be used to request one or more paging controllers to locate idle mode mobile stations. The location information may be used by one or more paging controllers to perform paging operations for the idle mode mobile stations. The foreign agents may initiate paging operations for an idle mode mobile station by communicating a paging request to one or more paging controllers. The foreign agents may communicate with one or more paging controllers using a number of different techniques, such as sending a unicast paging request or a multicast paging request, for example. Improving communication between foreign agents and paging controllers may result in reducing network signaling for the MBWA system, as well as reducing complexity and cost associated with paging operations in the MBWA system.  
      Various embodiments may be directed to improved techniques for communicating information between foreign agents and paging controllers. In one embodiment, for example, an apparatus may comprise a foreign agent having a foreign agent idle mode manager to store at least one paging controller identifier associated with an idle mode mobile station for a subnet. The subnet may have multiple paging controllers and associated paging groups. The foreign agent may send a paging request with a mobile station identifier for the idle mode mobile station to at least one of the multiple paging controllers corresponding to at least one paging controller identifier. The embodiments are not limited in this context.  
      In various embodiments, the foreign agent may send a paging request using various communication techniques. In one embodiment, for example, the foreign agent idle mode manager may store multiple paging controller identifiers associated with the idle mode mobile station. The foreign agent may send a multicast paging request with the mobile station identifier to each of the multiple paging controllers corresponding to the paging controller identifiers. In another embodiment, for example, the foreign agent idle mode manager may store a single paging controller identifier associated with the idle mode mobile station. The foreign agent may send a unicast paging request with the mobile station identifier to a single paging controller corresponding to the single paging controller identifier. The embodiments are not limited in this context.  
       FIG. 1A  illustrates one embodiment of a system.  FIG. 1A  illustrates a block diagram of a communications system  100 . In various embodiments, the communications system  100  may comprise multiple nodes. A node generally may comprise any physical or logical entity for communicating information in the communications system  100  and may be implemented as hardware, software, or any combination thereof, as desired for a given set of design parameters or performance constraints. Although  FIG. 1A  may show a limited number of nodes by way of example, it can be appreciated that additional or fewer nodes may be employed for a given implementation.  
      In various embodiments, a node may comprise, or be implemented as, a computer system, a computer sub-system, a computer, an appliance, a workstation, a terminal, a server, a personal computer (PC), a laptop, an ultra-laptop, a handheld computer, a personal digital assistant (PDA), a set top box (STB), a telephone, a mobile telephone, a cellular telephone, a handset, a wireless access point, a base station (BS), a mobile station (STA), a subscriber station (SS), a mobile subscriber center (MSC), a radio network controller (RNC), a microprocessor, an integrated circuit such as an application specific integrated circuit (ASIC), a programmable logic device (PLD), a processor such as general purpose processor, a digital signal processor (DSP) and/or a network processor, an interface, an input/output (I/O) device (e.g., keyboard, mouse, display, printer), a router, a hub, a gateway, a bridge, a switch, a circuit, a logic gate, a register, a semiconductor device, a chip, a transistor, or any other device, machine, tool, equipment, component, or combination thereof. The embodiments are not limited in this context.  
      In various embodiments, a node may comprise, or be implemented as, software, a software module, an application, a program, a subroutine, an instruction set, computing code, words, values, symbols or combination thereof. A node may be implemented according to a predefined computer language, manner or syntax, for instructing a processor to perform a certain function. Examples of a computer language may include C, C++, Java, BASIC, Perl, Matlab, Pascal, Visual BASIC, assembly language, machine code, micro-code for a network processor, and so forth. The embodiments are not limited in this context.  
      The nodes of the communications system  100  may be arranged to communicate one or more types of information, such as media information and control information. Media information generally may refer to any data representing content meant for a user, such as image information, video information, graphical information, audio information, voice information, textual information, numerical information, alphanumeric symbols, character symbols, and so forth. Control information generally may refer to any data representing commands, instructions or control words meant for an automated system. For example, control information may be used to route media information through a system, or instruct a node to process the media information in a certain manner. The media and control information may be communicated from and to a number of different devices or networks.  
      In various implementations, the nodes of the communications system  100  may be arranged to segment a set of media information and control information into a series of packets. A packet generally may comprise a discrete data set having fixed or varying lengths, and may be represented in terms of bits or bytes. It can be appreciated that the described embodiments are applicable to any type of communication content or format, such as packets, cells, frames, fragments, units, and so forth.  
      The communications system  100  may communicate information in accordance with one or more standards, such as standards promulgated by the IEEE, the Internet Engineering Task Force (IETF), the International Telecommunications Union (ITU), and so forth. In various embodiments, for example, the communications system  100  may communicate information according to one or more IEEE 802 standards including IEEE 802.11 standards (e.g., 802.11a, b, g/h, j, n, and variants) for WLANs and/or 802.16 standards (e.g., 802.16a/d/e wireless broadband access systems, 802.16-2004, 802.16.2-2004, 802.16f, and variants) for WMANs. The communications system  100  may communicate information according to one or more of the Digital Video Broadcasting Terrestrial (DVB-T) broadcasting standard and the High performance radio Local Area Network (HiperLAN) standard. The embodiments are not limited in this context.  
      In various embodiments, the communications system  100  may employ one or more protocols such as medium access control (MAC) protocol, Physical Layer Convergence Protocol (PLCP), Simple Network Management Protocol (SNMP), Asynchronous Transfer Mode (ATM) protocol, Frame Relay protocol, Systems Network Architecture (SNA) protocol, Transport Control Protocol (TCP), Internet Protocol (IP), TCP/IP, X.25, Hypertext Transfer Protocol (HTTP), User Datagram Protocol (UDP), and so forth.  
      The communications system  100  may include one or more nodes arranged to communicate information over one or more wired and/or wireless communications media. Examples of wired communications media may include a wire, cable, printed circuit board (PCB), backplane, switch fabric, semiconductor material, twisted-pair wire, co-axial cable, fiber optics, and so forth. An example of a wireless communication media may include portions of a wireless spectrum, such as the radio-frequency (RF) spectrum. In such implementations, the nodes of the system  100  may include components and interfaces suitable for communicating information signals over the designated wireless spectrum, such as one or more transmitters, receivers, transceivers, amplifiers, filters, control logic, antennas and so forth.  
      The communications media may be connected to a node using an input/output (I/O) adapter. The I/O adapter may be arranged to operate with any suitable technique for controlling information signals between nodes using a desired set of communications protocols, services or operating procedures. The I/O adapter may also include the appropriate physical connectors to connect the I/O adapter with a corresponding communications medium. Examples of an I/O adapter may include a network interface, a network interface card (NIC), a line card, a disc controller, video controller, audio controller, and so forth.  
      In various embodiments, the communications system  100  may comprise or form part of a network, such as a WiMAX network, a broadband wireless access (BWA) network, a MBWA network, a WLAN, a WMAN, a wireless wide area network (WWAN), a wireless personal area network (WPAN), an SDMA network, a Code Division Multiple Access (CDMA) network, a Wide-band CDMA (WCDMA) network, a Time Division Synchronous CDMA (TD-SCDMA) network, a Time Division Multiple Access (TDMA) network, an Extended-TDMA (E-TDMA) network, a Global System for Mobile Communications (GSM) network, an Orthogonal Frequency Division Multiplexing (OFDM) network, an Orthogonal Frequency Division Multiple Access (OFDMA) network, a North American Digital Cellular (NADC) network, a Universal Mobile Telephone System (UMTS) network, a third generation ( 3 G) network, a fourth generation ( 4 G) network, a Universal Mobile Telecommunications System (UTS) network, a High-Speed Downlink Packet Access (HSDPA) network, a Broadband Radio Access Networks (BRAN) network, a General Packet Radio Service (GPRS) network, a 3 rd  Generation Partnership Project (3GPP) network, a local area network (LAN), a wide area network (WAN), a metropolitan area network (MAN), a Global Positioning System (GPS) network, an Ultra Wide Band (UWB) network, an Internet network, a World Wide Web network, a cellular network, a radio network, a satellite network, and/or any other communications network configured to carry data. The embodiments are not limited in this context.  
      In various embodiments, the communications system  100  may be arranged to perform data communications using any number of different wireless protocols over various wireless communications media. In one embodiment, for example, various nodes of communications system  100  may be arranged to perform data communications using any number of different data communications systems or techniques, such as GSM with General Packet Radio Service (GPRS) systems (GSM/GPRS), CDMA/1xRTT systems, Enhanced Data Rates for Global Evolution (EDGE) systems, Evolution Data Only or Evolution Data Optimized (EV-DO) systems, Evolution For Data and Voice (EV-DV) systems, High Speed Downlink Packet Access (HSDPA) systems, one or more IEEE 802 standards including IEEE 802.11 standards (e.g., 802.11a, b, g/h, j, n, and variants) for WLANs and/or 802.16 standards (e.g., 802.16-2004, 802.16.2-2004, 802.16e, 802.16f, and variants), DVB-T, HiperLAN, and others. The embodiments are not limited in this respect.  
      In various embodiments, the communications system  100  may employ various modulation techniques including, for example: OFDM modulation, Quadrature Amplitude Modulation (QAM), N-state QAM (N-QAM) such as 16-QAM (four bits per symbol), 32-QAM (five bits per symbol), 64-QAM (six bits per symbol), 128-QAM (seven bits per symbol), and 256-QAM (eight bits per symbol), Differential QAM (DQAM), Binary Phase Shift Keying (BPSK) modulation, Quadrature Phase Shift Keying (QPSK) modulation, Offset QPSK (OQPSK) modulation, Differential QPSK (DQPSK), Frequency Shift Keying (FSK) modulation, Minimum Shift Keying (MSK) modulation, Gaussian MSK (GMSK) modulation, and so forth. The embodiments are not limited in this context.  
      The communications system  100  may form part of a multi-carrier system and/or a multiple input multiple output (MIMO) system. A multi-carrier system may use multi-carrier modulations for RF transmissions. A MIMO system is one that uses multiple input and output antennas. In one embodiment, for example, the communications system  100  may comprise a MIMO system arranged to use multi-carrier modulation. For example, the MIMO system may employ one or more multi-carrier communications channels for communicating multi-carrier communication signals. A multi-carrier channel may comprise, for example, a wideband channel comprising multiple sub-channels. The MIMO system may be arranged to communicate one or more spatial data streams using multiple antennas. Examples of an antenna include an internal antenna, an omni-directional antenna, a monopole antenna, a dipole antenna, an end fed antenna, a circularly polarized antenna, a micro-strip antenna, a diversity antenna, a dual antenna, an antenna array, and so forth. Alternatively, the communications system  100  may comprise a multi-carrier system using only a single antenna, such as a single input single output (SISO) system. The embodiments are not limited in this context.  
      In various embodiments, the communications system  100  may comprise a physical (PHY) layer component for communicating devices, which can be implemented in either hardware or software, and which is based on IEEE standards 802.11 n, 802.16-2004, and/or 802.16e, for example. In one embodiment, one or more nodes within the communications system  100  may include a transceiver for a MIMO-OFDM system. The embodiments are not limited in this context.  
      As shown in  FIG. 1A , the communications system  100  may be illustrated and described as comprising several separate functional elements, such as modules and/or blocks. In various embodiments, the modules and/or blocks may be connected by one or more communications media. Communications media generally may comprise any medium capable of carrying information signals. For example, communication media may comprise wired communication media, wireless communication media, or a combination of both, as desired for a given implementation.  
      The modules and/or blocks may comprise, or be implemented as, one or more systems, sub-systems, processors, devices, machines, tools, components, circuits, registers, applications, programs, subroutines, or any combination thereof, as desired for a given set of design or performance constraints. Although certain modules and/or blocks may be described by way of example, it can be appreciated that a greater or lesser number of modules and/or blocks may be used and still fall within the scope of the embodiments. Further, although various embodiments may be described in terms of modules and/or blocks to facilitate description, such modules and/or blocks may be implemented by one or more hardware components (e.g., processors, DSPs, PLDs, ASICs, circuits, registers), software components (e.g., programs, subroutines, logic) and/or combination thereof.  
      In various embodiments, the communications system  100  may be implemented as MBWA that operates in accordance with WiMAX wireless broadband technology based on the IEEE 802.16 standard, for example. System  100  may comprise multiple nodes such as a home agent (HA)  101 , mobile stations  102 - 1 -m, paging controllers  104 - 1 -n, foreign agents  105 - 1 -q, paging groups  106 - 1 -o, and base stations  108 - 1 -p, where m, n, o, p and q may represent any arbitrary number, all connected via a network  103 . Although  FIG. 1A  illustrates the communications system  100  with a limited number of nodes, it may be appreciated that more or less nodes may be implemented for the communications system  100  and still fall within the scope of the embodiments.  
      In various embodiments, a communications system  100  may include home agent  101 . Home agent  101  may be used to implement, for example, one or more protocols to manage network addresses for a network. In one embodiment, for example, home agent  101  may be used to implement a mobile Internet Protocol (IP). Mobile IP is an IETF standard communications protocol that is designed to allow mobile device users to move from one network to another while maintaining their permanent IP address. Mobile IP provides techniques for node mobility within the Internet. Using Mobile IP, nodes may change their point-of-attachment to a network such as the Internet without changing their IP address. This allows them to maintain transport and higher-layer connections while moving. Node mobility is realized without the need to propagate host-specific routes throughout the Internet routing fabric.  
      In general operation, Mobile IP routes packets destined for one or more mobile stations  102 - 1 -m to a home network, or a network identified by the network prefix of the permanent home address for one or more mobile stations  102 - 1 -m. At the home network, home agent  101  may intercept such packets and tunnels them to a most recently reported care-of-address for a mobile station  102 - 1 -m. The care-of-address may correspond to the address of the foreign agent serving the network where the mobile station is currently residing. At the endpoint of the tunnel, the inner packets are decapsulated and delivered to the mobile station  102 - 1 -m. In the reverse direction, packets sent by mobile stations  102 - 1 -m are routed to their destination using standard IP routing techniques.  
      Although some embodiments are described using Mobile IP, it may be appreciated that other similar protocols may be used as desired for a given implementation. For example, the communications system  100  may be modified to use the session initiation protocol (SIP) and others as well. The embodiments are not limited in this context.  
      In various embodiments, the communications system  100  may include mobile stations  102 - 1 -m. Mobile stations  102 - 1 -m may comprise generalized equipment sets providing connectivity to other wireless devices, such as other mobile devices or fixed devices. Examples for mobile stations  102 - 1 -m may include a computer, server, notebook computer, laptop computer, handheld computer, telephone, cellular telephone, personal digital assistant (PDA), combination cellular telephone and PDA, smartphone, one-way pagers, two-way pagers, handheld video devices, handheld audio devices, handheld multimedia devices, and so forth. In one embodiment, for example, the mobile devices may be implemented as mobile stations (STA) for a WLAN, or mobile subscriber stations (MSS) for a WMAN. Although some embodiments may be described with the mobile devices implemented as a STA or MSS by way of example, it may be appreciated that other embodiments may be implemented using other wireless devices as well. The embodiments are not limited in this context.  
      In various embodiments, the communications system  100  may include paging controllers  104 - 1 -n. Paging controllers  104 - 1 -n may be employed to perform paging operations for system  100 . Paging operations may include sending paging announcement messages to mobile stations  102 - 1 -m. Paging controllers  104 - 1 -n may comprise functional network entities that may be implemented anywhere within system  100 . In one embodiment, for example, a paging controller may be implemented as part of an access service network (ASN) gateway. The ASN gateway may include a grouping of various devices arranged to implement various functional network entities. In another example, a paging controller may be co-located with a mobile subscriber center (MSC), a base station or node B, or other network infrastructure equipment. In yet another example, a paging controller may be implemented as a separate network device or entity. The embodiments are not limited in this context.  
      In various embodiments, a communications system  100  may include foreign agents (FA)  105 - 1 -q. Foreign agents  105 - 1 -q may be arranged to deliver data packets to the mobile stations that are away from their home network. Moreover, foreign agents  105 - 1 -q may manage location operations in support of paging operations as performed by paging controllers  104 - 1 -n for the communications system  100 . As with paging controllers  104 - 1 -n, foreign agents  105 - 1 -q may comprise functional network entities that may be implemented anywhere within the communications system  100 . In one embodiment, for example, a foreign agent may be implemented as part of an ASN gateway with one or paging controllers. In another example, a foreign agent may be co-located with a MSC, a base station or node B, or other network infrastructure equipment. In yet another example, a foreign agent may be implemented as a separate network device or entity. The embodiments are not limited in this context.  
      It is worthy to note that the number of paging controllers  104 - 1 -n and foreign agents  105 - 1 -q used for a given implementation may vary. In addition, the communications system  100  may have a different number of paging controllers  104 - 1 -n relative to foreign agents  105 - 1 -q. Furthermore, paging controllers  104 - 1 -n and foreign agents  105 - 1 -q may have different relationships as desired for a given implementation. For example, paging controllers  104 - 1 -n and foreign agents  105 - 1 -q may have a hierarchical or non-hierarchical relationship. In other examples, paging controllers  104 - 1 -n and foreign agents  105 - 1 -q may have a one-to-one correspondence, a one-to-many correspondence, a many-to-many correspondence, and a completely non-deterministic correspondence. The embodiments are not limited in this context.  
      In various embodiments, a communications system  100  may include paging groups  106 - 1 -o. Paging groups  106 - 1 -o may be a logical unit for paging announcement messages. In one embodiment, for example, paging groups  106 - 1 -o may represent logical groupings of one or more base stations  108 - 1 -p. The geographic area covered by the base station (s) of a particular paging group is referred to as the corresponding paging area. As shown in  FIG. 1 , the communications system  100  comprises three paging groups  106 - 1 ,  106 - 2 ,  106 - 3  and two paging controllers  104 - 1 ,  104 - 2 , for example. Paging controller  104 - 1  manages paging groups  106 - 1  and  106 - 2 . Paging controller  104 - 2  manages paging group  106 - 3 . Paging group  106 - 1  comprises three base stations  108 - 1 ,  108 - 2  and  108 - 3 . Paging group  106 - 2  comprises one base station  108 - 4 . Paging group  106 - 3  comprises two base stations  108 - 5  and  108 - 6 . Base stations  108 - 1 - 4  and paging controller  104 - 1  exchange network backbone messages  120 - 1 - 4 . Base stations  108 - 5 - 6  and paging controller  104 - 2  exchange network backbone messages  120 - 5 - 6 . For brevity and illustrative purposes four mobile stations  102 - 1 ,  102 - 2 ,  102 - 3  and  102 - 4  are shown. The embodiments are not limited, however, to the reference example given in  FIG. 1 .  
      In various embodiments, a paging controller  104 - 1 -n may also perform location information management by maintaining an idle mode register table to store current information about idle mode mobile stations that are residing in the paging groups for which it is responsible. Alternatively, location information about idle mode mobile stations may be managed by a separate network entity other than the paging controllers. In this case, the paging controller may retrieve this location information from the separate network entity when performing paging operations. In the following example, it is assumed that the location information is stored by the paging controller in its idle mode register table, although the embodiments are not limited in this context. A paging controller  104 - 1 -n may perform paging operations by sending or broadcasting a paging announcement message to base stations  108 - 1 -p within a paging group  106 - 1 -o. The paging announcement message may be sent in response to a paging event. Examples of a paging event may include informing a mobile station  102 - 1 -m of an incoming voice call or data packets, forcing a location update of a mobile station  102 - 1 -m, upon expiration of various timers, and so forth. The embodiments are not limited in this context.  
      In various embodiments, the paging announcement message may include a mobile station identifier (MSID) for a given mobile station  102 - 1 -m. The base stations  108 - 1 -p may send or broadcast the paging announcement message to all mobile stations  102 - 1 -m within transmission range of the base stations  108 - 1 -p. When a particular mobile station  102 - 1 -m having the same MSID as contained in the paging announcement message receives the paging announcement message, the receiving mobile station  102 - 1 -m may respond to the paging announcement message.  
      In various embodiments, the communications system  100  may include various fixed devices, such as base stations  108 - 1 -p. A fixed device may comprise a generalized equipment set providing connectivity, management, and control of another wireless device, such as one or more mobile devices. Examples for a fixed device may include a wireless access point (AP), base station or node B, router, switch, hub, gateway, server, computer, PC, workstation, and so forth. In one embodiment, for example, the fixed device may comprise a base station or node B for a cellular radio-telephone system. The fixed device may also provide access to a network, and other nodes accessible via the network (such as a web server). The network may comprise, for example, a packet network such as the Internet, a corporate or enterprise network, a voice network such as the Public Switched Telephone Network (PSTN), and so forth. Although some embodiments may be described with a fixed device implemented as a base station or node B by way of example, it may be appreciated that other embodiments may be implemented using other wireless devices as well. The embodiments are not limited in this context.  
      In general operation, the communications system  100  may be arranged to perform idle mode operations. Efficient implementation of idle mode operation is a consideration in all mobile networks including future IEEE 802.16 based mobile WiMAX networks. At any given point in time, for example, a statistically larger percentage of mobile stations  102 - 1 -m in the communications system  100  are not engaged in active calls (i.e., active mode) and thus are in idle mode. As a result, there may be a need within the communications system  100  to efficiently track a potentially large population of mobile stations  102 - 1 -m while maintaining their power saving profile (i.e., not requiring the mobile stations  102 - 1 -m to resume active mode). Furthermore, there may be a need to efficiently track mobile stations  102 - 1 -m while conserving valuable air-link resources in performing the tracking activity. Air-link control messages such as paging announcement messages and other control signaling messages generally do not comprise active user-traffic. Therefore, these types of air-link messages are non-revenue generating signaling overhead traffic for a network operator. Given a statistically large percentage of mobile stations  102 - 1 -m that may be in idle mode, reducing this signaling overhead may be valuable from a MBWA design standpoint. Consequently, various embodiments described herein may employ various techniques to reduce network signaling overhead.  
      For significant time durations T, mobile stations  102 - 1 -m may be powered on in wireless the communications system  100  but may not be in an active call session. To use time durations T as battery conserving opportunities, Idle Mode and Paging operations are described in the IEEE 802.16 standard. In accordance with these procedures, mobile stations  102 - 1 -m may enter or switch into a low-power state referred to as idle mode. The IEEE 802.16 standard specifies techniques to force mobile stations  102 - 1 -m back into an active mode whenever required by the communications system  100 . This may occur, for example, when there is an incoming call or data packets for a mobile station  102 - 1 -m. The IEEE 802.16 standard provides various procedures to force mobile stations  102 - 1 -m back into an active mode from an idle mode.  
      While a mobile station  102 - 1 -m is in idle mode, the communications system  100  maintains any desired connection states of the mobile station  102 - 1 -m to facilitate a faster network entry for the mobile station  102 - 1 -m if it needs to return from idle mode to active mode, such as when there is an incoming data or voice traffic pending for an idle mode mobile station, for example. This information may be referred to as Idle Mode Retain Information (IMRI). Examples of IMRI may include a connection identifier for a mobile station, a quality-of-service (QoS) parameter, authentication keys, and so forth. The embodiments are not limited in this context.  
      Furthermore, instead of tracking the exact location of an idle mode mobile station at all times, the IEEE 802.16 specifications describe procedures to only keep track of its approximate location as designated by a paging group  106 - 1 -o. Typically, a paging group  106 - 1 -o comprises of a cluster of one or more base stations  108 - 1 -p. The communications system  100  only maintains the current paging group  106 - 1 -o of the idle mode mobile station  102 - 1 -m. When an idle mode mobile station  102 - 1 -m moves out from its current paging group  106 - 1 -o and enters a new paging group  106 - 1 -o, its location information is updated. In this manner, the communications system  100  keeps track of the location information of the idle mode mobile station  102 - 1 -m to the accuracy of a given paging area corresponding to the current paging group  106 - 1 -o of the idle mode mobile station  102 - 1 -m. The communications system  100  uses the approximate location information and IMRI of an idle mode mobile station  102 - 1 -m to locate and set up new connections with the idle mode mobile station  102 - 1 -m. When needed, the idle mode mobile station  102 - 1 -m may be precisely tracked to its associated base station  108 - 1 -p by sending a broadcast paging announcement message within all base stations  108 - 1 -p that comprise the current paging group  106 - 1 -o of the idle mode mobile station  102 - 1 - m.  
      Various embodiments may include a novel architecture, operations, and signaling message flows to implement idle mode and paging operations for IEEE 802.16 based networks. In one embodiment, for example, network signaling overhead reduction may be implemented by using one or more foreign agents  105 - 1 -q. Each foreign agent  105 - 1 -q may have a foreign agent idle mode manager (FAIMM). The FAIMM may be used to store various types of information depending upon a particular communication technique used to communicate information between foreign agents and paging controllers. When using a multicast paging request technique, for example, the FAIMM may store multiple paging controller identifiers for multiple paging controllers corresponding to a given subnet, paging group, and/or paging area. When using a unicast paging request technique, for example, the FAIMM may store a single paging controller identifier for a single paging controller corresponding to a given subnet, paging group, and/or paging area. A foreign agent may use the paging controller identifier(s) managed and stored by the FAIMM to communicate a paging request to the appropriate paging controller(s) to initiate paging operations for an idle mode mobile station, as described in more detail below.  
      In other embodiments, FAIMM may store idle mode information for mobile stations  102 - 1 -m operating in idle mode in communications system  100 . Examples of idle mode information may include the identifiers of mobile stations (MSID) that went to idle mode while being active in the subnet administered by the foreign agent  105 - 1 -q to which the FAIMM belong. Other examples of idle mode information may include the current paging group identifier (PGID) and paging controller identifier (PCID) of the idle mode mobile stations that went to idle mode while being active in the subnet administered by the foreign agent  105 - 1 -q to which the FAIMM belong. The idle mode information by one or more FAIMM of the foreign agents  105 - 1 -q may also be used by the corresponding foreign agents  105 - 1 -q to send paging requests to one or more paging controllers  104 - 1 -n to implement paging operations for the communications system  100 . The paging controller  104 - 1 -n may process the paging requests from the foreign agents  105 - 1 -q to perform paging operations for one or more mobile stations  102 - 1 -m.  
      Prior to performing paging operations in the communications system  100 , a foreign agent  105 - 1 -q needs to send a paging request to a paging controller  104 - 1 -n that is responsible for the paging group  106 - 1 -o in which a target idle mode mobile station  102 - 1 -m currently resides during a paging event. Various embodiments are directed to techniques for improved interaction and communication between foreign agents  105 - 1 -q and paging controllers  104 - 1 -n.  
      In various embodiments, foreign agents  105 - 1 -q may administer one or more subnets, such as IP subnets, for example. Paging controllers  104 - 1 -n may administer one or more paging groups  106 - 1 -o. Consequently, in order for foreign agents  105 - 1 -q to send paging requests to paging controllers  104 -  1  -n, there must be some sort of mapping or relationship drawn between paging groups  106 - 1 -o and the subnets of foreign agents  105 - 1 -q. As previously described, a paging group  106 - 1 -o may comprise one or more base stations  108 - 1 -p. Similarly, a subnet may comprise one or more base stations  108 - 1 -p. The dimensioning of paging groups  106 - 1 -o and subnets, however, are carried out independently during network deployment planning. Therefore, there can be different topological relationships among paging groups  106 - 1 -o and the various subnets. For brevity and clarity, the following description assumes that a single paging controller  104 - 1 -n is responsible for only a single paging group  106 - 1 -o. It is worthy to note, however, that a single paging controller  104 - 1 -n may administer more than one paging group  106 - 1 -o as desired for a given implementation. The embodiments are not limited in this context.  
      There may be many different possible topological relationships among paging groups  106 - 1 -o and the various subnets. For example, the topological relationships may include a one-to one mapping between paging groups  106 - 1 -o and the subnets. In another example, one subnet may contain or include multiple paging groups  106 - 1 -o. In this case, one paging group  106 - 1 -o may overlap between two different subnets. In yet another example, one paging group  106 - 1 -o may contain or include multiple subnets. In this case, one subnet may overlap between two different paging groups. The potential topological relationships may be described in more detail with reference to  FIG. 1B .  
       FIG. 1B  illustrates one embodiment of subnets for a system.  FIG. 1B  illustrates the communications system  100  having subnets and paging groups arranged such that one subnet may contain or include multiple paging groups. In this case, one paging group may overlap between two different subnets. As shown in FIG. IB, the communications system  100  has been re-configured to illustrate two subnets  140 - 1 ,  140 - 2 . Subnets  140 - 1 ,  140 - 2  may be managed by foreign agents  105 - 1 ,  105 - 2 , respectively. Each of subnets  140 - 1 ,  140 - 2  may have multiple paging groups  106 - 1 -o. For example, subnet  140 - 1  may contain or include paging groups  106 - 1 ,  106 - 2  and a portion of paging group  106 - 3 . Similarly, subnet  140 - 2  may contain or include paging groups  106 - 4 ,  106 - 5  and a portion of paging group  106 - 3 . Paging controllers  104 - 1 - 5  administer paging groups  106 - 1 - 5 , respectively. It is worthy to note that other embodiments may have other topological relationships between various sets of paging groups and subnets. The embodiments are not limited in this context.  
      In general operation, assume that home agent  101  has foreign agent  105 - 1  registered as the foreign agent of idle mode mobile station  102 - 1 . In this case, home agent  101  forwards any packets destined for idle mode mobile station  102 - 1  to foreign agent  105 - 1 . Foreign agent  105 - 1  may be arranged with a FAIMM having idle mode information for idle mode mobile station  102 - 1 . Foreign agent  105 - 1  needs to send a paging request for idle mode mobile station  102 - 1  to a paging controller  104 - 1 -n in which idle mode mobile station  102 - 1  currently resides during an incoming call or data connection request.  
      Various embodiments may be directed to techniques for communicating paging requests between the foreign agents and one or more paging controllers. In one embodiment, for example, foreign agent  105 - 1  may send a multicast paging request with the mobile station identifier (MSID) of the idle mode mobile station to the multiple paging controllers  104 - 1 ,  104 - 2 ,  104 - 3  within its subnet  140 - 1 . In a different embodiment, for example, foreign agent  105 - 1  may send a unicast paging request with the MSID of the idle mode mobile station to a specific paging controller of paging controllers  104 - 1 - 3  that corresponds to a given PCID and/or PGID stored by the FAIMM of foreign agent  105 - 1 . The FAIMM for foreign agent  105 - 1  may be arranged to support both techniques, although the FAIMM may store different types of information for each technique.  
      In the multicast paging request technique, for example, the FAIMM may be arranged to store a PCID for each paging controller servicing the subnet of foreign agent  105 - 1 . Since this information is relatively static, the FAIMM may be programmed with this information during initialization operations for foreign agent  105 - 1  and/or the communications system  100 . In response to incoming data for idle mode mobile station  102 - 1 , foreign agent  105 - 1  may then send a multicast paging request with the MSID of idle mode mobile station  102 - 1  to all paging controllers corresponding to the stored PCID of the FAIMM to initiate paging operations by the appropriate paging controller having the MSID currently stored in its idle mode register table. The embodiments are not limited in this context.  
      In the unicast paging request technique, for example, the FAIMM may be arranged to store the MSID, current PCID and/or current PGID of the idle mode mobile stations that went to idle mode while being active in the subnet of foreign agent  105 - 1 . In contrast to the multicast paging request technique, this information is dynamic and therefore the FAIMM of foreign agent  105 - 1  needs to track and maintain a current PCID and/or PGID for idle mode mobile station  102 - 1  as idle mode mobile station  102 - 1  travels through the various paging groups  106 - 1 - 5  and subnets  140 - 1 ,  140 - 2  of the communications system  100 . In response to incoming data for an idle mode mobile station, foreign agent  105 - 1  may then send a unicast paging request with the MSID of an idle mode mobile station to a specific paging controller matching a PCID and/or PGID stored by the FAIMM in its idle mode information table to initiate paging operations by the given paging controller. The embodiments are not limited in this context.  
       FIG. 2  illustrates one embodiment of a processing system.  FIG. 2  illustrates one embodiment of a processing system  200 . Processing system  200  may be implemented for any of the nodes shown in  FIG. 1 . In various embodiments, processing system  200  may include one or more elements  202 - 1 -x, where x is a positive integer. For example, processing system  200  may include a processor  202 - 1 , a memory  202 - 2 , and a data bus  202 - 3  to connect processor  202 - 1  with memory  202 - 2 . Although a limited number of elements may be illustrated and described for processing system  200  by way of example, it may be appreciated that more or less elements may be implemented for processing system  200 , and still fall within the scope of the embodiments. The embodiments are not limited in this context.  
      In one embodiment, for example, element  202 - 1  may comprise a processor. Processor  202 - 1  may be implemented as any processor, such as a complex instruction set computer (CISC) microprocessor, a reduced instruction set computing (RISC) microprocessor, a very long instruction word (VLIW) microprocessor, a processor implementing a combination of instruction sets, or other processor device. In one embodiment, for example, processor  202 - 1  may be implemented as a general purpose processor, such as a processor made by Intel® Corporation, Santa Clara, Calif. Processor  202 - 1  may also be implemented as a dedicated processor, such as a controller, microcontroller, embedded processor, a digital signal processor (DSP), a network processor, a media processor, an input/output (I/O) processor, and so forth. The embodiments are not limited in this context.  
      In various embodiments, processing system  200  may include an element  202 - 2 . In one embodiment, for example, element  202 - 2  may comprise memory. Memory  202 - 2  may include any machine-readable or computer-readable media capable of storing data, including both volatile and non-volatile memory. For example, memory  202 - 2  may include read-only memory (ROM), random-access memory (RAM), dynamic RAM (DRAM), Double-Data-Rate DRAM (DDRAM), synchronous DRAM (SDRAM), static RAM (SRAM), programmable ROM (PROM), erasable programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), flash memory, polymer memory such as ferroelectric polymer memory, ovonic memory, phase change or ferroelectric memory, silicon-oxide-nitride-oxide-silicon (SONOS) memory, magnetic or optical cards, or any other type of media suitable for storing information. It is worthy to note that some portion or all of memory  202 - 2  may be included on the same integrated circuit as processor  202 - 1 , or alternatively some portion or all of memory  202 - 2  may be disposed on an integrated circuit or other medium, for example a hard disk drive, that is external to the integrated circuit of processor  202 - 1 . The embodiments are not limited in this context.  
      In various embodiments, memory  202 - 2  may include one or more elements, such as elements  204 - 1 -y, where y represents a positive integer. In one embodiment, for example, memory  202 - 2  may include a FAIMM  204 - 1  and/or a mobile station idle mode manager (MSIMM)  204 - 2 . The MSIMM may be arranged to handle the idle mode and paging related operations at a mobile station. When implemented as part of a foreign agent  105 - 1 -q, processor  202 - 1  may execute FAIMM  204 - 1  of memory  202 - 2 . When implemented as part of a mobile station  102 - 1 -m, processor  202 - 1  may execute MSIMM  204 - 2  of memory  202 - 2 . Although a limited number of elements may be illustrated and described for memory  202 - 2  by way of example, it may be appreciated that more or less elements may be implemented for memory  202 - 2 , and still fall within the scope of the embodiments. Furthermore, it may be appreciated that FAIMM  204 - 1  and MSIMM  204 - 2  may be implemented using software, hardware, or a combination of both, as desired for a given set of performance and design constraints. The embodiments are not limited in this context.  
      In various embodiments, FAIMM  204 - 1  may be used to store idle mode information for mobile stations  102 - 1 -m operating in idle mode in the communications system  100 . The idle mode information may include any information used to locate and/or page a mobile station  102 - 1 -m. Examples of idle mode information may include a MSID of each idle mode mobile station  102 - 1 -m that went idle originally at the foreign agent  105 - 1 -q, a current PCID and/or PGID corresponding to each idle mode MSID, and so forth. FAIMM  204 - 1  may maintain the idle mode information in an idle mode information table for each mobile station  102 - 1 -m that went to idle mode while being active in the subnet of the corresponding foreign agent  105 - 1 -q. The idle mode information may be used when implementing the unicast paging request technique. When implementing the multicast paging request technique, FAIMM  204 - 1  may maintain idle mode information that is limited to one or more paging controller identifiers. The embodiments are not limited in this context.  
      In various embodiments, foreign agent  105 - 1  may send a paging request for idle mode mobile station  102 - 1  using a multicast paging request technique. More particularly, foreign agent  105 - 1  may send paging requests for idle mode mobile station  102 - 1  by sending a multicast paging request to all paging controllers  104 - 1 - 3  servicing its subnet  140 - 1 . In this technique, when foreign agent  105 - 1  receives a data packet for idle mode mobile station  102 - 1 , it learns all of the paging controllers  104 - 1 - 3  serving its subnet  140 - 1  from its FAIMM that stores this information in the idle mode information table. This depends on the specific network topology implemented between the subnets and paging groups. For example, if there is a one-to-one mapping between each paging controller and each foreign agent, then there is only one possible paging controller for the foreign agent. If there are multiple paging groups in a subnet for a foreign agent, however, the paging controllers corresponding to these paging groups are all of the possible paging controllers within a subnet for the foreign agent.  
      As shown in  FIG. 1B , when foreign agent  105 - 1  receives data for idle mode mobile station  102 - 1 , foreign agent  105 - 1  multicasts a paging request to paging controllers  104 - 1 - 3 . Similarly, potential paging controllers can be determined for other network topologies. When paging controllers  104 - 1 - 3  receive the multicast paging announcement message from foreign agent  105 - 1 , paging controllers  104 - 1 - 3  determine if idle mode mobile station  102 - 1  is located in their respective paging groups  106 - 1 - 3  by searching for the presence of the MSID for idle mode mobile station  102 - 1  in their respective idle mode register tables. If a paging controller  104 - 1 - 3  does not find the MSID for idle mode mobile station  102 - 1  in its idle mode register table it ignores the multicast paging request. Only one paging controller from among paging controllers  104 - 1 - 3  will determine that idle mode mobile station  102 - 1  is located in its associated paging area. That paging controller then carries out the paging operations to locate idle mode mobile station  102 - 1 . For example, assume that idle mode mobile station  102 - 1  is residing in paging group  106 - 2  when foreign agent  105 - 1  broadcasts the multicast paging request. In this case, only paging controller  104 - 2  will carry out paging operations to locate idle mode mobile station  102 - 1  in paging group  106 - 2  of subnet  140 - 1 , and paging controllers  104 - 1 ,  104 - 3  will ignore the multicast paging request message from foreign agent  105 - 1 .  
      The multicast paging request technique may have several advantages and disadvantages. For example, the multicast paging request technique does not introduce any state to foreign agents  105 - 1 -q as they do not need to know the current PCID and/or PGID for idle mode mobile stations. Therefore, foreign agents  105 - 1 -q may have reduced complexity and associated costs. The multicast paging request technique, however, may consume additional network bandwidth since the foreign agent needs to multicast the paging requests to all paging controllers serving its subnet. Consequently, the number of signaling messages may be equal to the number of paging controllers servicing the subnet of a given foreign agent. This number can be relatively large resulting in significant signaling overhead. The selection of the multicast paging request technique may be based on the particular design goals of a given implementation. The embodiments are not limited in this context.  
      In various embodiments, foreign agent  105 - 1  may send a paging request for idle mode mobile station  102 - 1  using a unicast paging request technique. In the unicast paging request technique, a foreign agent  105 - 1 -q tracks and maintains a state that stores a PCID and/or PGID in the idle mode information table of its FAIMM for each idle mode mobile station  102 - 1 -m. In this case, when a foreign agent  105 - 1 -q receives a data packet destined to an idle mode mobile station  102 - 1 -m, it sends a unicast paging request to a paging controller  104 - 1 -n corresponding to the PCID and/or PGID instead of multicasting the paging requests to all paging controllers servicing its subnet. The paging controller  104 - 1 -n corresponding to the PCID and/or PGID may then perform paging operations in order to locate the idle mode mobile station under consideration. Referring again to our previous example, if idle mode mobile station  102 - 1  for which foreign agent  105 - 1  receives new data packets resides in paging group  106 - 2 , then foreign agent  105 - 1  will learn about it and send a paging request only to paging controller  104 - 2  which administers paging group  106 - 2 .  
      As with the multicast paging request technique, the unicast paging request technique may have several advantages and disadvantages. For example, a foreign agent needs to send only a single paging request message since the foreign agent knows the current paging controller for the idle mode mobile station. Therefore, the unicast paging request technique reduces the signaling overhead associated with foreign agent and paging controller interactions during call delivery relative to the multicast paging request technique. The unicast paging request techniques, however, forces the foreign agent to maintain current PCID and/or PGID information of each idle mode mobile station in its subnet. Therefore, an additional state is introduced into a foreign agent implementation. Furthermore, the foreign agent needs to update the current PCID and/or PGID information of idle mode mobile stations when the latter move moves between paging groups. This may increase the complexity of the foreign agents and associated costs in order to implement idle mode paging operations. The selection of the unicast paging request technique may be based on the particular design goals of a given implementation. The embodiments are not limited in this context.  
      In order to implement unicast paging request techniques, FAIMM  204 - 1  may need to store additional idle mode information for mobile stations  102 - 1 -m operating in idle mode in the communications system  100  relative to the multicast paging request technique where the FAIMM does need not to store any information relating to the mobile stations  102 - 1 -m operating in idle mode. The additional idle mode information may include a MSID of each idle mode mobile station  102 - 1 -m that went idle originally at the foreign agent  105 - 1 -q, a PGID and/or PCID corresponding to each MSID and so forth. FAIMM  204 - 1  may maintain the idle mode information in an idle mode information table for each mobile station  102 - 1 -m that went to idle mode while being active in the subnet of the corresponding foreign agent  105 - 1 -q. An example of an idle mode information table for foreign agent  105 - 1  may be shown in TABLE 1 as follows:  
                           TABLE 1                                   MSID   PCID, PGID                          MSIDMS1   PC1 and/or PG2           MSIDMS2   PC2 and/or PG3           MSIDMS3   PC3 and/or PG1           MSIDMS4   PC4 and/or PG4                      
 
 As shown in TABLE 1, each entry of the idle mode information table maintained by FAIMM  204 - 1  may have two columns. The first column is the MSID and the second column is a PCID and/or PGID corresponding to the MSID. When an idle mode mobile station  102 - 1 -m having idle mode information stored in the idle mode information table of FAIMM of a foreign agent  105 - 1  -q moves from one paging area to another, FAIMM  204 - 1  updates the PCID and/or PGID for that mobile station  102 - 1 -m. In this manner, FAIMM  204 - 1  maintains current information about the PCID and/or PGID of each idle mode MS that are in its idle mode information table. 
 
      In various embodiments, FAIMM  204 - 1  may be used to keep updated information about the PCID and/or PGID of mobile stations  102 - 1 -m that are in idle mode. Paging controllers  104 - 1 -n may perform the paging operations upon receiving paging requests from a foreign agent  105 - 1 -q. Paging groups  106 - 1 -o may be identified by a PGID and represent the coverage area of a cluster of base stations  108 - 1 -p (e.g., base stations of a paging area). Foreign agents  105 - 1 -q may maintain the current PCID and/or PGID information for mobile stations  102 - 1 -m in idle mode in their FAIMM. As long as mobile stations  102 - 1 -m in an idle mode remain in a given paging group  106 - 1 -o they do not have to update their idle mode information (i.e., PCID and/or PGID). If mobile stations  102 - 1 -m trigger a location update event such as crossing into different paging groups  106 - 1 -o while in the idle mode, however, mobile stations  102 - 1 -m perform a location update procedure to (1) update foreign agents  105 - 1 -q of the new paging group(s)  106 - 1 -o and the corresponding paging controller(s) and (2) to inform the paging controller that a MSID in its idle mode register table needs to be updated with a new paging group. Alternatively, mobile stations  102 - 1 -m may perform location update procedures in response to other location update events, such as at periodic or aperiodic time intervals using a system timer, and other location update events as well. The embodiments are not limited in this context.  
      In various embodiments, paging controllers  104 - 1 -n may use the location information stored in their associated idle mode register tables to track down and reach mobile stations  102 - 1 -m in idle mode within the coverage area of their respective paging groups  106 - 1 -o. This may be implemented using any number of paging techniques. For example, a paging controller  104 - 1 -n may broadcast a paging announcement message, such as a mobile-paging-advertising (MOB-PAG-ADV) message, for example. The broadcast message may be broadcast by all base stations  108 - 1 -p in the respective paging groups  106 - 1 -o whenever the communications system  100  needs to reach any one of mobile stations  102 - 1 -m. There may be a variety of reasons for the communications systems  100  to reach mobile stations  102 - 1 -m. For example, to request an update of its location (i.e., paging group  106 - 1 -o), perform network entry (e.g., when there is an incoming packet), among other reasons.  
      In various embodiments, each paging controller  104 - 1 -n maintains an idle mode register table that keeps information about all mobile stations  102 - 1 - 4  that have gone into idle mode while being active in the particular paging group(s)  106 - 1 - 3  managed by the respective paging controller  104 - 1 - 2 .  FIG. 1  illustrates a snapshot in time t of four representative mobile stations  102 - 1 - 4  in idle mode. At time t, all four mobile stations  102 - 1 - 4  are located in coverage area of base station  108 - 4  and in paging group  106 - 2 , for example. Prior to t, mobile station  102 - 1  was in coverage area of base station  108 - 3  in paging group  106 - 1  and moved to base station  108 - 4  in paging group  106 - 2  as indicated by vector  110 . Prior to t, mobile station  102 - 4  was in coverage area of base station  108 - 5  in paging group  106 - 3  and moved to base station  108 - 4  in paging group  106 - 2  as indicated by vector  112 . Although only four idle mode mobile stations  102 - 1 - 4  are shown in  FIG. 1 , it will be expected that in actual deployments additional mobile stations, both idle mode and active mode, may be present in the coverage area of base station  108 - 4 . The embodiments are not limited in this context.  
      Accordingly, various embodiments may be implemented in accordance with the following techniques for using location information to broadcast paging announcement messages in the communications system  100 . The techniques may include various operations/procedures and accompanying message flows. For example, the techniques may include a procedure at a provisioning time for the communications system  100 , a procedure when mobile stations  102 - 1 - 4  enter idle mode, a procedure when idle mode mobile stations  102 - 1 - 4  performs location update, and a procedure for paging an idle mode mobile station.  
       FIG. 3  illustrates one embodiment of a first message flow.  FIG. 3  illustrates a message flow  300 . Message flow  300  may be representative of, for example, operations for when a mobile station  102 - 1 -m (e.g., mobile station  102 - 1 ) enters into an idle mode (e.g., from an active mode). Message flow  300  may illustrate messages communicated between a mobile station  302 , a base station  304 , a foreign agent  306  and a paging controller  308 , which may be representative of one or more mobile stations  102 - 1 -m, base stations  108 - 1 -p, foreign agents  105 - 1 -q, and paging controllers  104 - 1 -n, respectively.  
      As shown in message flow  300 , when mobile station  302  decides to initiate idle mode, it sends a deregistration request (DREG-REQ) message  302 - 1  using the format defined in IEEE 802.16e to its serving base station  304 . The mobile station includes its MSID in DREG-REQ message  302 - 1 . Upon receiving DREG-REQ message  302 - 1 , base station  304  sends a data path release request (DATA-PATH-REL-REQ) message  304 - 1  to a corresponding foreign agent  306  to trigger the data path release process for mobile station  302 . The DATA-PATH-REL-REQ message  304 - 1  may include information such as a MSID, base station identifier (BSID), PGID, PCID, and IMRI.  
      When foreign agent  306  receives DATA-PATH-REL-REQ message  304 - 1 , it sends a mobile station information report (MS-INFO-RPT) message  306 - 1  to paging controller  308  as identified by the PCID of DATA-PATH-REL-REQ message  304 - 1 . MS-INFO-RPT message  306 - 1  may include information such as a MSID, PGID, and IMRI.  
      When paging controller  308  receives the MS-INFO-RPT message  306 - 1 , paging controller  308  adds mobile station  302  to its idle mode register table of mobile stations in the paging area identified by the PGID of the MS-INFO-RPT message  306 - 1 . Paging controller  308  also adds the IMRI of the idle mode mobile station to its idle mode register table. Paging controller  308  may send a mobile station information response (MS-INFO-RSP) message  308 - 1  to foreign agent  306 . MS-INFO-RSP message  308 - 1  may include information such as a MSID, PGID, PCID, and IMRI. The message flow from this point may vary depending upon whether the multicast paging request technique or unicast paging request technique is implemented.  
      If the multicast paging request technique is used, for example, foreign agent  306  may receive MS-INFO-RSP message  308 - 1 . Since the idle mode information stored by FAIMM is static in the multicast mode, foreign agent  306  may send a data path release response (DATA-PATH-REL-RSP) message  306 - 2  to base station  304  without updating the idle mode information table of its FAIMM. DATA-PATH-REL-RSP message  306 - 2  may include such information as a MSID, PGID, PCID, and IMRI, for example.  
      If the unicast paging request technique is used, foreign agent  306  may also receive the MS-INFO-RSP message  308 - 1 . Since the idle mode information stored by the FAIMM is dynamic in the unicast mode, the FAIMM may add the MSID, PCID and/or PGID from MS-INFO-RSP message  308 - 1  to its idle mode information table. Foreign agent  306  may then send DATA-PATH-REL-RSP message  306 - 2  to base station  304 .  
      Base station  304  may receive DATA-PATH-REL-RSP message  306 - 2 . Upon receiving DATA-PATH-REL-RSP message  306 - 2 , base station  304  may send a deregistration command (DREG-CMD) message  304 - 2  containing the PCID to mobile station  302 .  
      When mobile station  302  receives DREG-CMD message  304 - 2 , mobile station  302  may enter into or switch to idle mode operations. Mobile station  302  may use MSIMM  204 - 2  to store the PCID for location update purposes. Finally, mobile station  302  listens to paging announcement messages in the current paging area to acquire a current PGID. Mobile station  302  needs the PGID to do a location update in case the PGID changes.  
       FIG. 4A  illustrates one embodiment of a second message flow.  FIG. 4A  illustrates a message flow  400 -A. Message flow  400 -A may be representative of, for example, operations for when mobile station  302  performs location update operations when the foreign agent uses the multicast paging request technique. When idle mode mobile station  302  moves from one paging area to another it performs location update operations. During normal operations, mobile station  302  may move from one paging group  106 - 1 -o to a different paging group  106 - 1 -o. As mobile station  302  moves between paging groups  106 - 1 -o, mobile station  302  acquires a new PGID for the new paging group  106 - 1 -o. Mobile station  302  may compare the new PGID with its current PGID as stored by MSIMM  204 - 2 . If the new PGID and current PGID fail to match, mobile station  302  initiates location update operations to update location information stored by paging controller  308 .  
      As shown in message flow  400 -A, mobile station  302  sends a ranging request (RNG-REQ) message  302 - 2  to base station  304  indicating that it needs to perform location update operations. Mobile station  302  includes its PCID in RNG-REQ message  302 - 2 , such as in the “Paging-controller-ID” field of RNG-REQ message  302 - 2 , for example.  
      Upon receiving RNG-REQ message  302 - 2 , base station  304  sends a location update request (LU-REQ) message  304 - 3  to paging controller  308  identified by the PCID in the RNG-REQ message. LU-REQ message  304 - 3  may contain information such as an MSID, PGID, and PCID. It may be noted that the PGID corresponds to a new paging area for mobile station  302 .  
      Paging controller  308  may receive LU-REQ message  304 - 3 . Upon receiving LU-REQ message  304 - 3 , paging controller  308  may update the PGID of the idle mode mobile station identified by the MSID in the LU-REQ message  304 - 3  in its idle mode register table. Then, paging controller may send a location update response (LU-RSP) message  308 - 2 .  
      When base station  304  receives LU-RSP message  308 - 2 , base station  304  sends ranging response (RNG-RSP) message  304 - 4  to mobile station  302  to inform mobile station  302  about the successful completion of the location update operations. Base station  304  then sends a location update confirm (LU-CFM) message  304 - 5  to paging controller  308 . LU-CFM message  304 - 5  may include information such as MSID and PGID.  
      Paging controller may receive LU-CFM message  304 - 5  and learn that the location update process for the idle mode mobile station identified by the MSID of LU-CFM message  304 - 5  is successful.  
       FIG. 4B  illustrates one embodiment of an alternate second message flow.  FIG. 4B  illustrates a message flow  400 -B. Message flow  400 -B may be representative of, for example, operations for when mobile station  302  performs location update operations when the foreign agent uses a unicast paging request technique. When idle mode mobile station  302  moves from one paging area to another it performs location update operations. During normal operations, mobile station  302  may move from one paging group  106 - 1 -o to a different paging group  106 - 1 -o. As mobile station  302  moves between paging groups  106 - 1 -o, mobile station  302  acquires a new PGID for the new paging group  106 - 1 -o. Mobile station  302  may compare the new PGID with its current PGID as stored by MSIMM  204 - 2 . If the new PGID and current PGID fail to match, mobile station  302  initiates location update operations to update location information stored by paging controller  308 .  
      As shown in message flow  400 -B, mobile station  302  sends a RNG-REQ message  302 - 3  to base station  304  indicating that it needs to perform location update operations. Mobile station  302  includes its PCID in RNG-REQ message  302 - 3 , such as in the “Paging-controller-ID” field of RNG-REQ message  302 - 3 , for example.  
      Upon receiving RNG-REQ message  302 - 3 , base station  304  sends LU-REQ message  304 - 6  to paging controller  308  identified by the PCID in the RNG-REQ message. LU-REQ message  304 - 6  may contain information such as an MSID, PGID, and PCID. It may be noted that the PGID corresponds to a new paging area for mobile station  302 .  
      Paging controller  308  may receive LU-REQ message  304 - 6 . Upon receiving LU-REQ message  304 - 6 , paging controller  308  may send location update information (LU-INFO) message  308 - 3 . The LU-INFO message  308 - 3  may contain information such as MSID, PGID, and PCID.  
      Foreign agent  306  may receive LU-INFO message  308 - 3 . Upon receiving LU-INFO message  308 - 3  foreign agent updates the PCID and/or PGID for the idle mode mobile station  302  identified by the MSID of the LU-INFO message  308 - 3  to update the new PCID and/or PGID for the idle mode mobile station  302  in the idle mode information table of its FAIMM. Foreign agent  306  then sends location update information confirmation (LU-INFO-CFM) message  306 - 2 . LU-INFO-CFM message  306 - 2  may contain information such as MSID, PGID, and PCID.  
      Paging controller  308  may receive LU-INFO-CFM message  306 - 2 . Upon receiving LU-INFO-CFM message  306 - 2 , paging controller  308  may update the PGID of the idle mode mobile station identified by the MSID in the LU-INFO-CFM message  306 - 2  in its idle mode register table. Then, paging controller may send LU-RSP message  308 - 4 .  
      When base station  304  receives LU-RSP message  308 - 4 , base station  304  sends RNG-RSP message  304 - 7  to mobile station  302  to inform mobile station  302  about the successful completion of the location update operations. Base station  304  then sends LU-CFM message  304 - 8  to paging controller  308 .  
      Paging controller may receive LU-CFM message  304 - 8  and learn that the location update process for the idle mode mobile station identified by the MSID of LU-CFM message  304 - 8  is successful.  
       FIG. 5  illustrates one embodiment of a third message flow.  FIG. 5  illustrates a message flow  500 . Message flow  500  may be representative of, for example, operations for paging idle mode mobile station  302  and for mobile station  302  to exit idle mode. When a communications system  100  needs to locate idle mode mobile station  302 , paging controller  308  may page idle mode mobile station  302  using, for example, a MOB-PAG-ADV message. It may be noted that the need to locate idle mode mobile station  302  may be initiated in response to any number of paging events, such as the arrival of new packets destined for idle mode mobile station  302 , for example. Message flow  500  assumes that all packets destined for idle mode mobile station  302  first reaches a home agent  504  for idle mode mobile station  302 . Home agent  504  may be representative of, for example, home agent  101  as described with reference to  FIG. 1 .  
      As shown in message flow  500 , home agent  504  forwards any received packets destined for idle mode mobile station  302  in the form of downlink data  504 - 1  to foreign agent  306 . Home agent  504  may accomplish this, for example, using Mobile IP address binding that is present in a database for home agent  504 .  
      Upon receiving downlink data  504 - 1 , foreign agent  306  determines that mobile station  302  is currently operating in idle mode. Foreign agent  306  may determine that a mobile station is in idle mode using different techniques, such as by maintaining a list of mobile stations that went to idle mode while being active in the subnet of the foreign agent  306 , for example. Other techniques can be used by the foreign agent to determine that a mobile station is in idle mode. The embodiments are not limited in this context.  
      When foreign agent  306  determines that a mobile station is in idle mode it sends mobile station paging request (MS-PAG-REQ) message  306 - 3  to paging controller(s) that serve its subnet. MS-PAG-REQ message  306 - 3  may contain MSID and PGID. This may be used, for example, to implement the multicast paging request technique.  
      When foreign agent  306  determines that a mobile station is in idle mode, it sends mobile station paging request (MS-PAG-REQ) message  306 - 3  to the paging controller identified by the PCID and/or PCID of mobile station  302  stored at the idle mode information table of FAIMM. MS-PAG-REQ message  306 - 3  may contain MSID and PGID. This may be used, for example, to implement the unicast paging request technique.  
      When paging controller  308  receives MS-PAG-REQ message  306 - 3 , paging controller  308  checks its idle mode register table to learn if mobile station  302  is in idle mode in a paging area  502  as identified by the PGID. If mobile station  302  is in idle mode in a paging area  502 , paging controller  308  sends a mobile station paging initiation (MS-PAG-INIT) message  308 - 5  to foreign agent  306 . Paging controller  308  also broadcasts a paging announcement message in the form of a paging announcement (PAG-ANN) message  308 - 6  to all base stations in paging area  502  as identified by the PGID. PAG-ANN message  308 - 6  may include information such as MSID of the idle mode mobile station that needs to be paged. Each base station, including base station  304 , broadcasts PAG-ANN  308 - 6 .  
      Assuming mobile station  302  currently resides in the coverage area of base station  304 , mobile station  302  receives PAG-ANN message  308 - 6  that contains its MSID. Mobile station  302  may reply to PAG-ANN message  308 - 6  using a mobile page response (MOB-PAG-RSP) message  302 - 4 . MOB-PAG-RSP message  302 - 4  may include information such as MSID and PCID.  
      Base station  304  may receive MOB-PAG-RSP message  302 - 4 . Base station  304  learns the identity of paging controller  308  using the PCID provided with MOB-PAG-RSP message  302 - 4 . Base station  304  may send an IMRI request (IMRI-REQ) message  304 - 9  to paging controller  308  corresponding to the PCID.  
      When paging controller  308  receives IMRI-REQ message  304 - 9 , paging controller  308  retrieves IMRI information for mobile station  302  from its idle mode register table. Paging controller  308  sends an IMRI response (IMRI-RSP) message  308 - 7  with the retrieved IMRI information to base station  304 . Base station  304  initiates mobile station re-entry operations to allow mobile station  302  to re-establish connectivity with the communications system  100 .  
      As previously described, foreign agents  105 - 1 -q may be used to track and maintain idle mode information (e.g., PCID and/or PGID) for mobile stations  102 - 1 -m. Paging controllers  104 - 1 -n may use the location information stored in their idle mode register table to perform paging operations for various mobile stations  102 - 1 -m operating in an idle mode. The paging operations may be implemented in accordance with any number of paging techniques as defined by any number of paging protocols, such as the paging protocols set forth in the IEEE  802 . 16  series of protocols, for example. The embodiments are not limited in this context.  
      Operations for various embodiments may be further described with reference to the following figures and accompanying examples. Some of the figures may include a logic flow. It can be appreciated that an illustrated logic flow merely provides one example of how the described functionality may be implemented. Further, a given logic flow does not necessarily have to be executed in the order presented unless otherwise indicated. In addition, a logic flow may be implemented by a hardware element, a software element executed by a processor, or any combination thereof. The embodiments are not limited in this context.  
       FIG. 6  illustrates one embodiment of a logic flow.  FIG. 6  illustrates a logic flow  600 . Logic flow  600  may represent various operations as described with reference to  FIGS. 3-5 , such as foreign agent  306 , for example. As shown in logic flow  600 , at least one PCID associated with an idle mode mobile station for a subnet, the subnet having multiple paging controllers and associated paging groups, may be stored at block  602 . A paging request with a MSID for the idle mode mobile station may be sent to at least one of the multiple paging controllers corresponding to the at least one PCID at block  604 . The embodiments are not limited in this context.  
      In one embodiment, for example, multiple paging controller identifiers associated with the idle mode mobile station may be stored. A multicast paging request with the mobile station identifier may be sent to each of the multiple paging controllers corresponding to the paging controller identifiers. The embodiments are not limited in this context.  
      In one embodiment, for example, a single paging controller identifier associated with the idle mode mobile station may be stored. A unicast paging request with the mobile station identifier may be sent to a single paging controller corresponding to the single paging controller identifier. The embodiments are not limited in this context.  
      In one embodiment, for example, the at least one paging controller identifier may be updated as the idle mode mobile station moves through a communication system. The embodiments are not limited in this context.  
      In one embodiment, for example, a paging announcement message may be sent for the idle mode mobile station corresponding to the mobile station identifier. The embodiments are not limited in this context.  
      Numerous specific details have been set forth herein to provide a thorough understanding of the embodiments. It will be understood by those skilled in the art, however, that the embodiments may be practiced without these specific details. In other instances, well-known operations, components and circuits have not been described in detail so as not to obscure the embodiments. It can be appreciated that the specific structural and functional details disclosed herein may be representative and do not necessarily limit the scope of the embodiments.  
      It is also worthy to note that any reference to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment.  
      Some embodiments may be implemented using an architecture that may vary in accordance with any number of factors, such as desired computational rate, power levels, heat tolerances, processing cycle budget, input data rates, output data rates, memory resources, data bus speeds and other performance constraints. For example, an embodiment may be implemented using software executed by a general-purpose or special-purpose processor. In another example, an embodiment may be implemented as dedicated hardware, such as a circuit, an application specific integrated circuit (ASIC), Programmable Logic Device (PLD) or digital signal processor (DSP), and so forth. In yet another example, an embodiment may be implemented by any combination of programmed general-purpose computer components and custom hardware components. The embodiments are not limited in this context.  
      Some embodiments may be described using the expression “coupled” and “connected” along with their derivatives. It should be understood that these terms are not intended as synonyms for each other. For example, some embodiments may be described using the term “connected” to indicate that two or more elements are in direct physical or electrical contact with each other. In another example, some embodiments may be described using the term “coupled” to indicate that two or more elements are in direct physical or electrical contact. The term “coupled,” however, may also mean that two or more elements are not in direct contact with each other, but yet still co-operate or interact with each other. The embodiments are not limited in this context.  
      Some embodiments may be implemented, for example, using a machine-readable medium or article which may store an instruction or a set of instructions that, if executed by a machine, may cause the machine to perform a method and/or operations in accordance with the embodiments. Such a machine may include, for example, any suitable processing platform, computing platform, computing device, processing device, computing system, processing system, computer, processor, or the like, and may be implemented using any suitable combination of hardware and/or software. The machine-readable medium or article may include, for example, any suitable type of memory unit, memory device, memory article, memory medium, storage device, storage article, storage medium and/or storage unit, for example, memory, removable or non-removable media, erasable or non-erasable media, writeable or re-writeable media, digital or analog media, hard disk, floppy disk, Compact Disk Read Only Memory (CD-ROM), Compact Disk Recordable (CD-R), Compact Disk Rewriteable (CD-RW), optical disk, magnetic media, various types of Digital Versatile Disk (DVD), a tape, a cassette, or the like. The instructions may include any suitable type of code, such as source code, compiled code, interpreted code, executable code, static code, dynamic code, and the like. The instructions may be implemented using any suitable high-level, low-level, object-oriented, visual, compiled and/or interpreted programming language, such as C, C++, Java, BASIC, Perl, Matlab, Pascal, Visual BASIC, assembly language, machine code, and so forth. The embodiments are not limited in this context.  
      Unless specifically stated otherwise, it may be appreciated that terms such as “processing,” “computing,” “calculating,” “determining,” or the like, refer to the action and/or processes of a computer or computing system, or similar electronic computing device, that manipulates and/or transforms data represented as physical quantities (e.g., electronic) within the computing system&#39;s registers and/or memories into other data similarly represented as physical quantities within the computing system&#39;s memories, registers or other such information storage, transmission or display devices. The embodiments are not limited in this context.  
      While certain features of the embodiments have been illustrated as described herein, many modifications, substitutions, changes and equivalents will now occur to those skilled in the art. It is therefore to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the embodiments.