Abstract:
The present invention relates to a location management system and a paging server in an Internet Protocol, IP, communication network that is adapted for wireless communication. The wireless IP network comprises multiple routers wherein at least one of the routers is an access router adapted for wireless communication with mobile nodes. The location management system is divided into at least one location area manager, and at least one regional location manager, the location area manager is a first signaling server and the regional location manager is a second signaling server, one of said location area manager and regional location manager comprises means for maintaining a list of mobile nodes located within at least one location area. The regional location manager comprises means for managing location information within a single location management region, and wherein the location area manager and regional location manager are connected to each other and adapted to exchange information. Furthermore, the paging server comprises means for obtaining location management information from the location management system and means for multicasting paging requests to the access routers wherein the access routers is determined by using said location management information.

Description:
This patent application claims priority from and incorporates by reference the entire disclosure of U.S. Provisional Patent Application No. 60/322,332, filed on Sep. 12, 2001. 

   FIELD OF INVENTION 
   The present invention relates to a communication system with Internet Protocol (IP) based transmission. 
   In particular, the present invention relates to a location management system and a paging server connectable to said location management system in an IP communication system adapted for wireless communication with Mobile Nodes (MN). 
   BACKGROUND OF THE INVENTION 
   The growing importance of the Internet and of mobile communication creates the demand to attach mobile computing devices adapted for wireless communication with mobile nodes to the Internet. The original Internet Protocol (IP) does not support mobile communication, therefore the Internet protocols must be augmented with mobility support. 
   The BRAIN Candidate Mobility Protocol (BCMP) is an example of a communication protocol that allows a network to provide wireless Internet access for mobile computers. BCMP is further described in IST-1999-10050 BRAIN, “BRAIN Architecture specifications and models, BRAIN functionality and protocol specification,” published on Mar. 30, 2001. Mobile computers adapted for BCMP is allowed to connect to a BCMP network and can send and receive data packets to and from other computers connected to the Internet. 
     FIG. 1  illustrates a BCMP network  100 . The BCMP network  100  comprises gateways  108 , routers  106 , Access Routers (AR)  104  and Mobile Nodes (MN)  102 . At least one of the routers  106 , is an Anchor Point (ANP) that owns and allocates IP addresses, authenticates users, maintains user records, and tunnels packets towards the Mobile Nodes (MN)  102 , e.g. laptops, which are connected to the IP network via the ARs  104 . The ARs  104  is connected to a wireless interface towards the MNs  102  and route information received from the MNs  102  further into the IP network. The ARs  104  are called BRAIN Access Routers (BAR) within the BCMP network  100 . Each AR is adapted to terminate tunnels from the ANPs and forwards packets to/from mobile hosts, e.g. terminals such as mobile phones, laptops or palmtop computers. The gateways  108  (i.e. border routers towards e.g. Internet) are called BRAIN Mobility Gateways (BMG) in BCMP. The gateways  108  are not required to have BCMP specific functionality. The role of the gateways  108  is to shield the rest of the BCMP network from the exterior routing protocols and to distribute traffic to the appropriate ANPs  106 . Besides these entities, the BCMP network  100  can also incorporate other network entities, such as AAA servers that store and manage user related information, Network Management functions, Quality of Service functions, Resource Management function, etc. 
   Each ANP  106  has globally routable address space and it allocates an IP address to the MN  102  when the MN  102  attach to the BCMP network  100 . This address is kept constant, despite handovers. The handover procedure is described further below. The pool of IP addresses owned by the ANP  106  is advertised using legacy IP routing inside the BCMP network  100  and toward external IP networks. This ensures that packets addressed to the address of the MN  102  obtained locally are routed, by means of standard IP routing, to the ANP  106  that allocated the address. The Anchor Points  106 , in turn, use IP-in-IP encapsulation to forward packets to the AR  104  where the MN  102  that is the destination is located at the moment. 
   When the MN  102  first contacts the AR  104  it must execute a login procedure. First it sends a login request message to the AR  104  at which it has appeared. In this request the MN  102  provides login and security information (e.g., mobile user identifier). The AR  104  selects the ANP  106  for the MN  102  according to a policy specified by an operator and forwards the login request to it. The MN  102  is not required to be aware of the policy and of the internal structure of the AR  104 . The selected ANP  106  identifies and authenticates the MN  102  and allocates a globally routable IP address and a new session identifier for the MN  102 . The session identifier is a temporary identifier used to index control messages in the BCMP network  100 . The session identifier, a security key and the IP address are sent back to the MN  102  in a login response message. 
   As the MN  102  move, it can connect to a new AR  104  when necessary. This is called a handover. The ANPs  106  must maintain up-to-date location information of MNs  102  they have allocated an address for and must update this information when ‘their’ MNs  102  move to another AR  104 . For this purpose, the ARs  104  notify ANPs  106  when the handover occurs. In addition, the BCMP can incorporate various local handover mechanisms that improve the performance of handover by, for example, building a temporary path from the old AR  104  to the new AR  104  in order to avoid loss of data packets sent to the MN  102 . 
   If the MN  102  moves far away from its ANP  106  then the tunnel between the ANP  106  and AR  104  may become very long. In order to avoid long tunnels, the BCMP allows (but does not mandate) the network operator to request that the MN  102  changes the ANP  106 . This improves routing efficiency in the network, in exchange for exposing mobility toward the Internet: the change of the ANP  106  requires a change of the MN&#39;s  102  IP address, which is a global mobility event. Alternatively, the operators may choose to accept long tunnels between the ANPs and the ARs in order to completely hide mobility from external networks. 
   The BCMP protocol provides a paging support that allows the MNs to enter idle mode and to reduce location update signalling load inside the AR. 
     FIG. 2 , illustrates a paging scenario in a BCMP network. The BCMP network  200  comprises the following nodes: a gateway  212  connected to the Internet  214 , routers  210 , 214 , wherein some of the routers are ANPs  208 , 216 , ARs  204 , 206  and a MN  202 . The nodes within the BCMP network exemplified by  FIG. 2  comprise the same functionality as the network depicted in  FIG. 1 . The MN  202  is in idle mode when it is turned on but is not involved in transmission of voice, data or certain time sensitive control information in contrast to active mode that occurs when the MN  202  is involved in such transmission. When the MN changes its state to then it informs its AR  204  about the mode change and performs handover in active mode when it moves  226  to the new AR  206  (as long as it stays within the same group of ARs  204 , 206  called a Paging Area (PA) PA 1 ). The ARs are not notified about the handover, which results in that the ARs will not know in which AR:s proximity the MN  202  is found. When data packets  218  are sent to the MN  202 , these  218  will still be routed to MN&#39;s  202  old AR  204 . This AR  204  knows that the MN  202  is idle and hence instead of transmitting its packets through the radio interface, it multicasts a paging request message  220  to all ARs  204 , 206  within the paging area PA 1 . Each AR  204 , 206  forwards the paging request  220  through its radio interface on a common control channel directed to the correct MN  202 . When the MN receives the paging request  220 , it performs a BCMP handover  222  and returns to normal mode of operation. This allows its packets to be routed to the MN  202 . 
   If, while in idle mode, the MN  202  moves  228  to an AR  224  that belongs to a different paging area PA 2  than its old AR  204 , then it performs a handover and returns to idle state immediately. The rest of the operation is the same as the steps described above. 
   The drawback of the paging mechanism specified by BCMP is that paging request messages  220  must be sent out by the ARs  204 , 206 , 224  and hence the ARs  204 , 206 , 224  must know which ARs  204 , 206 , 224  belong to the same paging area. This means that the configuration and possible reconfiguration of paging areas involves communication with ARs. If, for example, a new AR is added to the network than in addition to configuring this AR, all the other ARs in the same paging area must be notified so they can update their paging areas. 
   There are additional drawbacks of the BCMP paging mechanism if the operator employs advanced paging schemes. A paging scheme defines the list and order of ARs where the MN is paged when it has incoming data packets. An advanced paging scheme may require, for example, that a particular user is always paged first through one particular AR and next through the ARs of its paging area. In this case, the BCMP paging scheme requires that this scheme is known by each AR, which causes significant configuration and processing load on the ARs. 
   As another insufficiency, the BCMP protocol as described above contains no functions that would enable operators to determine which mobile nodes are located in certain parts of the network (e.g., for location aware services). Therefore, it is not possible to trigger external entities when certain users/nodes move into or outside pre-defined areas if their movement matches a certain pattern e.g. speed and direction. For example, an owner of a coffee shop would like to send an ad to each user that enters the district containing the coffee shop. This could be a service provided by the BCMP network, but it needs location management function. A pre-defined area is specified as a set of cells. A cell is the coverage area of a wireless access point within an access router. In this example, an area could be the cell that contains the coffee shop, plus all neighbouring cells. As another service, the ad would be sent to each user that is moving toward the coffee shop. This service requires a location management infrastructure. 
   HMIPv6 is another protocol for mobile IP that has a similar network architecture to BCMP. The drawback of HMIPv6 regarding the location management is identical to BCMP. One difference between BCMP and HMIPv6 is that HMIPv6 uses IETF (Internet Engineering Task Force) Mobile IPv6 message formats. 
   SUMMARY 
   The present invention tackles the above stated problem associated with the fact that conventional IP networks do not provide an efficient and simple tool for locating a mobile node within said IP network. 
   Thus, an object of the present invention to provide a location management system within said IP network that does not load access routers with location management related tasks. The access routers should primarily be adapted for tasks relating to packet forwarding. 
   Another object of the present invention is to provide an enhanced paging functionality that utilizing location information from said location management system within said IP network. 
   The above-mentioned object is achieved by a location management system in an Internet Protocol, IP, communication network that is adapted for wireless communication. The wireless IP network comprises multiple routers wherein at least one of the routers is an access router adapted for wireless communication with mobile nodes, wherein an area served by one access router is a cell. The location management system is divided into at least one location area manager, and at least one regional location manager, the location area manager is a first signaling server and the regional location manager is a second signaling server, one of said location area manager and regional location manager comprises means for maintaining a list of mobile nodes located within at least one location area which is a first predefined set of cells. The regional location manager comprises means for managing location information within a single location management region, which is a second predefined set of cells, and wherein the location area manager and regional location manager are connected to each other and adapted to exchange information. 
   Moreover, the above-mentioned object is achieved by a paging server in an Internet Protocol, IP, communication network adapted for wireless communication, wherein the wireless IP network comprises multiple routers. At least one of the routers is an access router adapted for wireless communication with mobile nodes, wherein an area served by one access router is a cell. The paging server comprises means for obtaining location management information from a location management system and means for multicasting paging requests to access routers wherein the access routers is determined by using said location management information. 
   Preferred embodiments are set forth in the depending claims. 
   An advantage with the present invention is that the location management is separated from the routing. The Access Routers are no longer involved within the location management or paging. This implies that the access routers are not required to be aware of paging areas or location areas. The only location management task required by the access router is to send handover notification to the Regional Location Manager. 
   Another advantage with the present invention is that it provides a centralized entity, the location management system, which overviews the mobility of a particular mobile node and is adapted to analyze or possibly predict its mobility pattern for optimizing paging or other functions of the network (e.g., location aware services changes). 
   Moreover, it removes the need to add paging related functions to access routers and to configure them according to paging settings. Further, it allows implementing advanced paging schemes without overloading access routers with configuration and processing. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic illustration of a BCMP network according to prior art. 
       FIG. 2  is a schematic illustration of a paging procedure in a BCMP network according to prior art. 
       FIG. 3  is a schematic illustration of an IP network where a location management system according to the present invention may be implemented. 
       FIG. 4  is a schematic illustration of the location management system according to the present invention. 
       FIG. 5  is a schematic illustration of a first handover scenario in a network that comprises the location management system according to the present invention shown in  FIG. 4 . 
       FIG. 6  is a schematic illustration of a second handover scenario in a network that comprises the location management system according to the present invention shown in  FIG. 4 . 
       FIG. 7  is a schematic illustration of a paging server connected to the location management system according to the present invention shown in  FIG. 4 . 
       FIGS. 8 ,  9  and  10  is a schematic illustration showing paging procedures with paging servers according to the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The present invention is applicable to an IP network  300 , which is exemplified in  FIG. 3 , comprising a plurality of routers  302 , wherein at least one of the routers is an Access Router (AR)  304 . The AR  304  is the closest router to the radio interface and it is associated with an access point  308  to which wireless Mobile Nodes (MN)  306 , e.g. laptops, can connect for transmission of IP traffic. That implies that the access point  308  comprises a unit for wireless communication, e.g. a base station. The MN  306  is hence a device accessing the network  308  via an access point. A Mobile User is a node or subscriber who is using the network. A mobile user may have various MNs out of which more than one may be connected to the network  300  at the same time. The ARs are connectable to the Internet  310  via further routers  302  and gateways  308 . In addition, the IP network is required to comprise entities handling the mobility. An example of such IP network  300  is a BCMP network  100  in accordance with  FIG. 1 , and a Hierarchical Mobile IP [HMIPv6] network that is running a similar protocol to BCMP. 
   In accordance with a first aspect of the present invention a set of functional entities that together are called Location Management system is specified. The Location Management system according to the present invention makes it possible for the network operators to trace the mobility of the MNs and use it to optimise operation or to provide location aware services. In particular, Location Management allows the network operator to find out the location of a mobile user; obtain the list of mobile users located in a given area; be alerted when a mobile user moves into or out of a given area; or find and eventually predict special mobility patterns (speed, direction) of users. 
   In accordance with the present invention, the location management system  400  comprises at least one Location Area Manager (LAM)  404   a - c  and at least one Regional Location Manager (RLM)  406   a - b . This is illustrated in  FIG. 4 . The location management system  400  comprises further a Location Manager (LM)  402  if there is more than one LAM  404   a - c . The LM  402  is used when the location management system comprise more than one LAM. The LM  402  is an interface to the LAMs  404   a - c . Requests to the location management system  400  arrive to the LM  402 . The LM  402  dispatches the request to the appropriate LAM. The functionality of the LAMs  404   a - c  and the RLMs  406   a - b  is described below. 
   Location Area 
   A Location Area (LA)  410   a - e  is a pre-defined set of cells used to determine the location of the MNs, wherein the term cell is well-known for a man skilled in the art. An IP network where the location management system may be implemented may contain any number of LAs  410   a - e  that may arbitrarily overlap. The Network operators may define the LA  410   a - e  by listing the cells it contains. If needed, the LAs  410   a - e  can be as small as a single cell. 
   Location information on a per cell basis is not always needed. In addition, updating user location database on a per cell basis would create significant signaliing and processing load in the location management system. The architecture of the location management system according to the present invention allows network operators to define customized LAs. Location information can thus be obtained on a per LA basis. 
   Location Area Managers 
   A Location Area Manager (LAM)  404   a  is a signalling server responsible for the LA  410   a . The LAM  404   a  may be responsible for more than one LA  410   a.  The LAM  404   a  contains a central processor, some data storage device (e.g., hard disk) and a communication interface to send and receive control messages. The network may contain a single LAM or multiple LAMs. In the case of multiple LAMs, they are co-ordinated by the LM  402 . 
   In accordance with a first embodiment of the present invention, the LAM  404   a  maintains a list of MNs  412  located in the particular Location Area  410   a . One LAM may maintain lists for a large number of LAs. The LAM  404   a  may be combined with the RLM  406   a , or it may be a separate server. 
   The RLM  406   a  notifies the appropriate LAM  404   a  when a handover results in a change of LA, which is illustrated in  FIG. 5 . The LAMs  404   a,b  in turn, update their respective lists. 
   According to a second embodiment of the present invention, the LAMs does not maintain the list of mobile nodes in particular Location Areas if that task is performed by RLMs. In that case LAMs serve as signalling forwarding entities. When they receive a request for a particular LA, they multicast the request to all RLMs that have ARs in the given LA. Then LAMs also collect and merge the responses. 
   Regional Location Manager 
   A Regional Location Manager (RLM)  406   a  is a signalling server that is responsible for handling location management operations inside its respective region, region1. Each region comprises a pre-defined subset of cells. The RLM  406   a  contains a central processor, some data storage device (e.g., hard disk) and a communication interface to send and receive control messages. The network may contain one single or a multiple RLMs depending on the number of regions it is partitioned into. For scalability, the location management related tasks may be distributed between a plurality of RLMs  406   a - b . The network is hence partitioned into location management regions that preferably are non-overlapping. Thus, each region is handled by the RLM  406   a , which is not required to be aware of LAs  410   d - e  that are outside its region. 
   Each cell (i.e. AR  408   a - i ) of the network should be assigned to at least one RLM  406   a - b , which is illustrated in  FIG. 4 . The group of cells assigned to one RLM is called location management region. The partitioning of cells into location management regions need not be co-ordinated with LAs. Note the difference between LAs and location management regions. 
   The Location Areas are defined in order to define areas e.g. a city or a district. The size and structure of LAs is defined such that the information obtained is useful—by using location areas, the network operator can tell the location of mobile users with a granularity of location areas. If each city is a separate LA  410   a  then the network knows in which city the MN  412  is located in, or if each district is a location area then it knows which district the MN is located in, and so on. Thus, the higher the number of LAs, the more accurate information is possible to gather, but the higher the processing and management load in the network becomes. 
   Location management regions, in contrast, are used merely for load distribution in the network. Instead of handling the location management of the entire network in one signalling server, cells are portioned and assigned to a plurality signalling servers, called RLMs  406   a - b . The size of the location management regions is determined by the capacity of RLM and by the rate at which the MNs  412  perform handovers in the particular area. 
   The RLMs  406   a - b  keep track of all the nodes in their region. They may be equipped with intelligence to match mobility patterns to user mobility for categorising the users; to predict user mobility; or for other purposes. 
   Since mobile networks may be very large and the number of mobile users very high, a query of location information is required to be a relatively cheap operation, e.g., listing the users located in a given area should not include querying all the cells in the particular area. For example, if the location area membership information is needed very rarely then it is a waste to continuously maintain these lists. On the other hand, if they are needed very frequently then it is inefficient to broadcast queries to each cell when the lists are needed. Using Regional Location Managers allows using a solution between these two extremes. An example is, when RLMs  406   a  do not automatically forward each notification to the LAM  404   a , but wait until the LAM  404   a  asks for the information. 
   Handover Notifications 
   When a mobile node moves into a new cell (i.e., performs a handover), the RLM should be notified. In what follows, it is assumed that the AR  408   b , that the MN  412  will be connected to after handover, sends a notification to the RLM(s)  406   a  it is assigned to in accordance with  FIG. 5 . Alternatively, a notification could be sent by the old AR  408   a  or by the Anchor Point if such exists. It is also possible to send separate notifications from two or all of these three entities at a single handover event. 
   According to one embodiment of the present invention, one MN  412  can be “assigned to” multiple RLMs  406   a - b  and send the notifications to them according to a load sharing principle. In an extreme case, all ARs can be assigned to the same RLMs(s). 
   In accordance with the present invention, sending the handover notification to the RLMs  406   a - b  is the only task ARs  408   a - i  need to perform for location management. This allows the location management system to be separated from routing. For example, it allows the ARs  408   a - i  to be unaware of the structure of the LAs  410   a - d  and it removes the need to update all ARs when a new LA is created. 
   In  FIG. 6 , the scenario when the handover brought the MN  412  into a new region is illustrated. The new RLM  406   b  contacts the old RLM  406   a  to download the accumulated information about the MNs  412  movement. 
   Extracting Location Change Information 
   When a MN  412  performs the handover, it may move into or out of any number of Las  410   a - e  depending on which two cells it performs the handover between. The role of the RLMs  406   a - b  is to decide which LAs  410   a - e  are affected by the particular handover. 
   In accordance to one embodiment, each RLM  406   a,b  knows which of the cells in its region belongs to which LA(s). In accordance with another embodiment, the RLM  406   a - b  obtains this information on demand. In addition, the RLMs  406   a - b  may be aware of, or may have access to a LA membership  410   a -e of other cells in the network. 
   When the RLM  406   a - b  receives the handover notification, it checks the Location Area membership of the cells affected in the handover. Based on this information, the RLM  406   a - b  determines whether the MN  412  has entered one or more new LAs  410   a - e  or has left one or more LAs  410   a - e . If the handover results in an entry or exit to/from one or more LAs  410   a - e , according to one embodiment the RLM  406   a - b  notifies other network entities such as the LAM  404   a - c  or according to another embodiment, the RLM  406   a - b  updates a local information base. According to a further embodiment, the RLM  406   a - b  does not notify the other network entities until it receives a request for such notification. 
   In order to find out the location of a particular mobile node using BCMP or HMIPv6, the Anchor Point should be contacted. The Anchor Point knows which Access Router the mobile node is located at. However, the presence of an Anchor Point is not required by the present invention. The method of finding the correct AR may be performed in another way which is apparent by the man skilled in the art. Next, it must be established to which LAs this particular AR belongs. This may be performed by using a database or by contacting the AR and its RLM. 
   Configuring Location Areas 
   According to the architecture of the location management system  400  in accordance with  FIG. 4 , the definition of the LAs needs to be configured in RLMs. However, not all RLMs need to be aware of all LAs. Typically, the RLM would know only about those LAs that are included in, or have an overlap with the region of the RLM. 
   Paging Servers 
   In accordance with a second aspect of the present invention, a paging server is introduced, that in connection with the location management system, instead of the ARs, performs paging of idle MNs. This is illustrated in  FIG. 7 , which shows the paging server  702  connected to the location management system  400  of  FIG. 4 . One paging server  702  is responsible for paging within one single paging area  702 . The paging area  702  is defined by an area served by a predetermined set of ARs  408   a - c . Each AR is required to be covered by one paging area, however only one paging area and paging server is illustrated in  FIG. 7 . 
   The paging server  702  may be used within a network using BCMP, HMIPv6 or within another network using a similar protocol for mobile IP communication. The paging server  702  is a signalling server connected to the location management system  400 , that multicasts paging messages to the destination ARs  408   a - c . It  702  contains a central processor, some data storage device (e.g., hard disk) and a communication interface to send and receive control messages. The network contains a single or multiple paging servers  702 . The paging server  702  may be a part of the RLM  406   a.    
   The introduction of paging servers  802  modifies the BCMP paging mechanism as the schematic illustration in  FIG. 8 .  FIG. 8  shows paging areas PA 1 - 5 , wherein one of the paging areas is controlled by the illustrated paging server  802 . The MN  804  is located within an area covered by the AR  816  which is within said paging area PA 3 . The operation of MNs  804  is unchanged. However, when the AR  806  receives data packets  808  addressed to the idle MN  804  then it contacts the paging server  802  instead of transmitting paging requests  810  itself. Next, the paging server  802  performs paging, i.e., transmits multicast paging requests  812 ,  814  in accordance with  FIG. 8 . Finally, as in the original BCMP paging mechanism, the MN performs a handover in response to receiving the paging request which is not shown in the figure. 
   If there are multiple paging servers in the network, each paging area must be uniquely assigned to one of them. Note, that the paging area may consist of the same area as the LA. 
   In accordance with one embodiment of the present invention, the AR  816  contacts the paging server  802  that handle the current paging area PA 3  of the MN  804 . 
   In an alternative embodiment of the present invention, illustrated in  FIG. 9 , wherein  FIG. 9  is a schematic illustration similar to  FIG. 8 , the AR  902  may contact  906  any paging server  904  (e.g., the one that is configured by a network management or by the one that is closest to the AR  902 ) when the AR  902  receives data packets  914  addressed to the idle MN  912 , and let the contacted paging server  904  forward the request  908  to the appropriate paging server  910 . The paging server  910  performs paging, i.e., transmits multicast paging requests  916 ,  918  accordingly. This removes the need for ARs to know the association of paging areas to the paging servers. In this case either the request  906  sent by the AR  902  to the paging server  904  must contain a reference to the MN&#39;s  912  paging area PA 3  or some paging servers must be aware of the MN&#39;s  912  paging area. The latter can be achieved by regularly updating one or more paging servers when the MN  912  changes paging area. 
   In accordance with a further embodiment of the present invention, paging servers  904 , 910  is used in advanced paging schemes where paging is not performed according to strictly pre-defined paging areas. For example, the paging servers  904 , 910  may have a database that contains a custom paging scheme for the individual MNs  912  (e.g. paging the MN in its home area first). This database should then be contacted when paging is initiated and paging should be performed accordingly. 
   In accordance with yet another embodiment of the present invention, paging servers contact the location management system and obtain information about the past location or past mobility of the MN and use this information to determine the set of ARs at which the MN shall be paged or to aid advanced paging schemes. 
   In addition to forwarding paging messages, an alternative operation of the paging servers would be in accordance with yet a further embodiment of the present invention as illustrated in  FIG. 10 . The paging server  1002  in this alternative can receive and temporarily store data packets  1004  addressed to the idle MN  1010 . When the MN  1010  goes into idle state then the paging server  1002  must be notified. Future data packets addressed to the MN&#39;s  1010  IP address will then be delivered to the paging server  1002  instead of the AR  1012 . The paging server  1002  should then temporarily store these packets  1004  and initiate the paging  1006 , 1008  as described previously. 
   Obtaining Location Information 
   The architecture of the location management system  400 , as illustrated in  FIG. 4 , according to the present invention allows the network operators to
         obtain a list of MNs  412  located in the given LAs  410   a - e . This is performed by asking the appropriate LAM  404   a - c  (possibly via the LM  402 ), who may check the list it maintains or ask the appropriate RLMs.   obtain a mobility characteristic or predicted movement of the MN  412 . This is achieved by asking the current RLM  406   a  of the MN  412 .   aid the optimal selection of paging areas in case of an incoming message destined to an idle mobile node. This is achieved by contacting the appropriate paging server. One important benefit of the present invention is that it allows an operator to have several LAs. Hence, there is a possibility for optimisation in terms of which LA the MN should be paged in.   obtain notifications when the MN  412  enters or exits LAs  410   a - e  (from RLMs  406   a - b  or from LAMs  404   a - c ).       

   The present invention is not limited to the above-described preferred embodiments. Various alternatives, modifications and equivalents may be used. Therefore, the above embodiments should not be taken as limiting the scope of the invention, which is defined by the appended claims.