Abstract:
This invention provides a messaging interface between a Mobile Node (MN) and an Access Router (AR) that enables the registration of MN preferences with a current AR (AR_current) and, when appropriate, the notification of the MN of the discovery of an AR in the proximity of AR_current that matches MN-specified preference criteria. The notifying AR_current may be the one that the MN originally registered its preferences with, or it could be another AR that, due to movement by the MN, has assumed the role of AR_current. In this case the MN preference data set to be transferred from one AR to another in response to the movement of the MN. The presently preferred messaging interface has two main modes of operation. In a first mode of operation, a “Query” mode, the MN explicitly queries AR_current for information descriptive of the capabilities of nearby ARs. AR_current responds to the MN query after examining the information stored in its PNL. In a second mode of operation, an “Event Notification” mode, the MN registers a request with AR_current that AR_current notify the MN whenever an AR satisfying certain criteria is available in the proximity of AR_current. The request registered by the MN may be transferred from one AR to another during handoff of the MN.

Description:
CLAIM OF PRIORITY FROM A COPENDING PROVISIONAL PATENT APPLICATION  
       [0001]    This patent application claims priority under 35 U.S.C. 119(e) from U.S. Provisional Patent Application No.: 60/364,139, filed Mar. 15, 2002, incorporated by reference herein in its entirety. 
     
    
     
       TECHNICAL FIELD  
         [0002]    The teachings of this invention relate generally to data communications networks and procedures and, more specifically, relate to techniques for informing a mobile node (MN), such as an Internet-enabled wireless terminal including cellular telephones and personal communicators, about the characteristics of network access in the neighborhood of MN.  
         BACKGROUND OF THE INVENTION  
         [0003]    At present, there is no suitable solution to the problem of informing a MN about the characteristics of network access in the neighborhood of the MN, that can best satisfy the preferences of the MN. As wireless mobile data networks evolve and proliferate, access networks employing different radio technologies (such as WLAN, WCDMA, GPRS, cdma2000, Bluetooth), as well as those belonging to different administrative entities, may each provide coverage within the same geographical area. In such a situation, a MN that is connected to an access router (AR_current) of a given access network may wish to locate an AR or ARs in the proximity of AR_current that can satisfy certain preferred criteria of the MN.  
           [0004]    One suitable enabling technology for this type of operation is the Candidate Access Router (CAR) discovery protocol that is currently under development. Reference in this regard can be had to, for example, “Issues in candidate access router discovery for seamless IP-level handoffs”, http://ietf.org/internet-drafts/drafts-ietf-seamoby-cardiscovery-issues-04.txt. The CAR discovery protocol enables the identification of the capability set of ARs that have overlapping coverage with that of AR_current. The information describing the capabilities of ARs in the proximity of AR_current, which is collected by using the CAR discovery protocol, is stored in a Physical Neighborhood List (PNL) of AR_current.  
           [0005]    However, prior to this invention a need existed for a MN-AR messaging interface that enabled the retrieval of the PNL information at the MN.  
         SUMMARY OF THE INVENTION  
         [0006]    The foregoing and other problems are overcome by methods and apparatus in accordance with embodiments of this invention.  
           [0007]    This invention provides a messaging interface between an MN and an AR that enables the registration of MN preferences with AR_current and, when appropriate, the notification to the MN of the discovery of an AR in the proximity of AR_current (including AR_current itself) that matches MN-specified preference criteria. One suitable technique to describe the preferences is via a set of attribute-value pairs. The notifying AR_current may be the one that the MN originally registered its preferences with, or it could be another AR that, due to movement by the MN, has assumed the role of AR_current. Thus, this invention also provides for the MN preference data set to be transferred from one AR to another in response to the movement of the MN.  
           [0008]    The messaging interface described in accordance with this invention has two main modes of operation. In a first mode, referred to herein as a “Query” mode, the MN explicitly queries AR_current for information descriptive of the capabilities of nearby ARs. AR_current responds to the MN query after examining the information stored in its PNL. In another embodiment, the MN provides its preferences in the query to AR_current. The AR_current responds with an affirmative or a negative answer, after examining the information in its PNL.  
           [0009]    In a second mode of operation, referred to herein as an “Event Notification” mode, the MN registers a request with AR_current. The request is for AR_current to notify the MN whenever an AR satisfying certain criteria is available in the proximity of AR_current, including AR_current itself. The request registered by the MN may be transferred from one AR to another. In the presently preferred embodiment, the transfer of the request containing the MN preference criteria data set is performed using a context transfer framework, as the MN changes its data communication network attachment points as a result of handoffs from AR to AR. A handoff is a change in the MN&#39;s point of attachment to the network from one AR to another. Thus, the MN need not register the request with every AR on its path. This technique conserves wireless bandwidth. Whenever any AR_current finds an AR in its vicinity or neighborhood that satisfies the MN preference criteria, it notifies the MN which may then change its connection to the indicated AR, or it may use the information for other application purposes. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    The above set forth and other features of these teachings are made more apparent in the ensuing Detailed Description of the Preferred Embodiments when read in conjunction with the attached Drawings, wherein:  
         [0011]    [0011]FIG. 1 is a block diagram of a wireless mobile access data communications network system that is constructed and operated in accordance with this invention;  
         [0012]    [0012]FIG. 2 shows in greater detail the coupling between access routers and a mobile node via base stations and access points (layer  2  devices);  
         [0013]    [0013]FIG. 3 is a block diagram of an exemplary wide coverage area network and a local coverage area (hot spot) network;  
         [0014]    [0014]FIG. 4 is a simplified block diagram of the MN showing WLAN and cellular interfaces;  
         [0015]    [0015]FIG. 5 is a messaging chart for a Query mode of operation;  
         [0016]    [0016]FIG. 6 is a messaging chart for an Event Notification mode of operation; and  
         [0017]    [0017]FIG. 7 shows an exemplary PNL at an AR. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]    [0018]FIG. 1 shows a wireless mobile access data communications network system  10  that includes a backbone network  12  that connects together a plurality of ARs  14 , shown by example as ARs  14 A,  14 B and  14 C. The illustrated ring configuration of the network  12  should not be viewed as a limitation upon the practice of this invention, as the topology may be more generally viewed as a network cloud type of configuration. Connected to or contained in the network  12  may also be an Authentication, Authorization and Accounting (AAA) server  18  that stores static user (MN) profiles  18 A. An exemplary MN  16  is shown at three points in time, first wirelessly connected to AR  14 A (T1), then to AR  14 B (T2) and finally to AR  14 C (T3).  
         [0019]    In accordance with an aspect of this invention, at T1 the MN  16  sends a Query to AR  14 A to determine the service and network access-related capabilities of ARs  14  in the vicinity of AR_current. The MN  16  can then determine itself if there are any ARs that meet its certain service and network access-related criteria. Alternatively, the MN  16  provides its preferences to AR_current in a query, and AR_current responds with an affirmative or a negative answer. By way of example, the MN service and network access-related criterion or criteria can include a desire to connect to a certain type of access technology, e.g., a wireless local area network or WLAN, (e.g., one operating in accordance with IEEE 802.11 or the European HyperLan standard), or a desire to receive a particular type of service (e.g., bandwidth, quality of service (QoS)), or a desire to discover special features such as security, transcoding services, playout buffer hosting and/or protocol header compression), or a desire to connect to a network with a lower cost of access, or a desire to locate ARs that have access to special services such as a location tracking server, or a security gateway. The AR  14 A has knowledge, stored in its PNL  15 , of the capabilities of ARs  14  in its vicinity, such as the capabilities of AR  14 B. The AR_current  14 A responds to the Query with the capabilities of the neighboring ARs. If appropriate, the response can include information for enabling the MN  16  to access a desired AR  14 . Reference in this regard can be made to the message diagram shown in FIG. 5. The current_AR may also include its capabilities along with the capabilities of the neighboring ARs, in the event the MN  16  does not already have this information.  
         [0020]    In accordance with a further aspect of this invention, at T1 the MN  16  may send an Event Notification Request message to the AR_current  14 . The Event Notification Request message includes MN  16  preferred service and network access-related preferences or criteria, and the Event Notification Request message could be sent in response to receiving a negative response to a Query message, or it could be sent in the first instance. Assuming for this example that the AR  14 A does not have an AR recorded in its PNL  15  that satisfies the MN  16  criteria, then at the T2, when the MN  16  is handed off to AR  14 B, a context transfer occurs whereby the preferred criteria of MN  16  are transferred from AR  14 A to AR  14 B. Assuming further for this example that the AR  14 B does not have an AR recorded in its PNL  15  that satisfies the MN  16  criteria, then at T3, when the MN  16  is handed off to AR  14 C, another context transfer occurs whereby the preferred criteria of MN  16  are transferred from AR  14 B to AR  14 C. Assume now that AR  14 C has knowledge of another AR  14  in its neighborhood that can satisfy the preferred criteria, then by an Event Notification (Response) the AR  14 C signals the MN  16  that such an AR exists in the neighborhood, and also provides the MN  16  with the identification of the AR, such as with the IP address of the AR, and possibly also with an identifier of a specific base station or access point attached to that AR. Reference in this regard can had to FIG. 6. Note that if the AR  14 C can satisfy the MN  16  preferred criteria, the MN  16  could have been notified of this when connected to AR  14 B.  
         [0021]    It should be noted that the network access/service preference(s) of the MN  16  may be obtained from its profile that is stored in the home AAA server  18 . This could occur when the MN  16  sends a request to the AAA server  18 , which in turn responds by pushing the stored static user profile  18 A to AR_current. The static profile may be subsequently overridden, modified or appended by the MN  16  sending an Event Notification Request message to AR_current.  
         [0022]    Also in FIG. 6, if AR_current does not have knowledge of a suitable AR in its vicinity it can provide an explicit NACK response, or it may simply remain silent.  
         [0023]    Note that the exact format of the messages, as well as the payload, i.e., the definition of the criterion to be met, is not within the scope of the present invention, and may take a number of suitable forms and embodiments.  
         [0024]    The Event Notification Request message sent at T1 may be considered as the MN  16  registering a trigger condition with the system  10 , and the Event Notification (Response) that occurs during T3 maybe considered as occurring in response to the trigger condition being satisfied.  
         [0025]    For the purposes of this invention an AR  14  is in the vicinity or the neighborhood of another AR  14  when they have overlapping coverage areas. Referring to FIG. 2, it can be seen that each AR  14 , e.g., AR  14 A,  14 B and  14 C, is associated with some number (e.g., three for  14 A, two for  14 B and one for  14 C) of base stations or base transceiver stations (BSs)  20  through which the MN  16  is wirelessly connected to the ARs. Note that each of BSs  20  may potentially use different radio access technology such as, but not limited to, GPRS, WCDMA, cdma2000, WLAN and Bluetooth. An AR is deemed to be in the vicinity or the neighborhood of another AR, even when their base stations use different radio access technologies, when they have an overlapping coverage area (e.g., the coverage area of the WLAN base station or access point overlapping with the coverage area of WCDMA base station). In this simple example BS 3  and BS 4  have an area of overlap  21 A where the MN  16  is able to connect to either AR  14 A or AR  14 B, and where the MN  16  can be handed off from AR  14 A to AR  14 B, or vice versa depending on the direction of movement of the MN  16 . Similarly, BS 1  and BS 2  have area of overlap  21 B, BS 1  and BS 3  have area of overlap  21 C, and BS 1  and BS 6  have area of overlap  21 D. In this example, the ARs  14 A,  14 B and  14 C are connected to the same network  12 , however, and as will be shown in FIG. 3, the ARs having an overlapping coverage area can be connected to different networks, such as network  12  and a network  30 .  
         [0026]    The PNL  15  at each AR  14  stores the information about the service and network access-related capabilities of ARs in its neighborhood. The PNL  15  can be statically configured, or there are techniques to populate the PNL using dynamic learning-based mechanisms, which are outside the scope of this invention. A typical example of a PNL  15  at AR  14 A is shown in FIG. 7. As shown in this non-limiting example, the PNL  15  of AR  14 A has an entry for AR  14 A, as well as entries for other ARs in the neighborhood, namely, ARs  14 B and  14 C in this example. Each entry lists the capabilities of corresponding AR that are common for all access interfaces of that AR. The PNL  15  also stores a list of base stations or access points connected to the corresponding AR. The capabilities of individual base stations or access points (e.g., the radio access technology) are also listed. Further, for each base station or access point, a list of other base stations or access points (associated with the same AR or different ARs), that have overlapping coverage with it is also stored. The PNL  15  may also contain actual co-ordinates of the access points, if such information is supplied by the associated ARs.  
         [0027]    The invention provides a messaging interface that enables the MN  16  to register its preferences with AR_current  14  and, in some cases, be notified when an AR  14 , that satisfies certain criteria expressed in the preferences of the MN  16 , is available in the proximity of AR_current. It is possible that the discovered AR is actually AR_current itself. This would happen, for example, if the MN  16  is currently attached to one base station or access point of AR_current that employs a specific radio access technology, while another interface of AR_current, possibly employing a different radio access technology, has characteristics that better match the preferences of the MN  16 . As another example, the MN  16  may discover AR_Current if the PNL of the previous AR did not have sufficient information about the characteristics of AR_current, and hence, failed to notify the MN  16  of certain matching criteria.  
         [0028]    Consider, as in FIGS. 3 and 4, a MN  16  that has two radio interfaces, namely a cellular interface  16 B for connecting with BSs  20 , and a WLAN interface  16 A for connecting with BSs  34  of the WLAN  30 . Further, assume that a user carrying the dual interface MN  16  is driving or biking around a town while running a wireless Internet application using cellular access (i.e., using ARs  14  and BSs  20 ). The user, however, wishes to be handed over to the WLAN  30  whenever possible (for example, when the user enters a shopping mall). However, for the sake of saving battery power, the WLAN interface  16 A of the MN  16  is held in a powered-down or off state (sleep mode) and, hence, cannot autonomously wake up itself when the user approaches the shopping mall.  
         [0029]    This invention solves this problem as follows: The user programs into the MN  16 , using a native user interface (UI)  16 D or some other UI (e.g., a PC or a web site) his or her preference to be handed over to the WLAN  30  whenever possible. When the UI  16 D is used, a control unit  16 C of the MN  16  records the entered user preference(s) and thereafter causes the MN  16  to register a request with the AR_current  14  of the cellular network  12 , via cellular interface  16 B, to notify the MN  16  whenever the possibility arises to be handed-off to the WLAN  30 . This could occur at T1 in as in FIG. 1. The request is transferred (context transfer) from one AR  14  to another as the MN  16  undergoes handoffs while the MN  16  is in motion. When the user approaches the shopping mall (where the WLAN  30  is assumed to be located for this example) the corresponding AR_current (AR  14 B in the example of FIG. 3) has knowledge, due to the entries in its PNL  15 , of the AR  32 A in its vicinity that supports WLAN  30  access points (ARs  32 A,  32 B,  32 C,  32 D), and notifies the MN  16  using an Event Notification (Response). The control unit  16 C is then enabled to power up or otherwise activate the WLAN interface  16 A and to begin searching for the WLAN beacon.  
         [0030]    In the example of FIG. 3 it is assumed that there are gateways  34  for connecting the network  12  and the network  30  to the Internet  22 .  
         [0031]    It is anticipated that in the future there will be many “hot spots” covered by different WLANs  30  and, as such, the MN  16  preferably would not activate the WLAN interface  16 A for each one. Rather, the MN  16  would prefer to be notified only when a particular one or type of WLAN  30  system was available. The factors that govern this choice may include preferences expressed by the MN  16  with respect to, as non-limiting examples, one or more of access cost, quality of service (QoS), availability of a particular type of service (e.g., video download) and whether the MN  16  is authorized to access a given WLAN  30 . The MN  16  may directly register these preferences with AR_current  14  using the UI  16 D, or these preferences may be obtained from the profile of the MN  16  that is stored in its home system AAA server  18 . The remainder of the notification operation may be as described above.  
         [0032]    More complex criteria may also be realized with the present invention. For example, a user of a multimode MN  16 , e.g., WLAN and 3G-enabled, is notified by the network  12  that an AR  14  in the near vicinity provides approximately the same data throughput that is necessary for the applications that are currently running, but at a lower cost. This mode of operation can implemented in this invention by receiving a notification from AR_current when the particular capabilities of the neighboring ARs  14  are within a desired range, e.g., at least 90% of current throughput and at a cost that is less than the current cost.  
         [0033]    The transfer of the various messages between the MN  16  and AR  14  may use the Internet Control Messaging Protocol (ICMP), the User Datagram Protocol (UDP), the Transmission Control Protocol (TCP), or any other standard method of message transfer between two nodes in an IP network. In non-IP networks other appropriate messaging protocols can be employed.  
         [0034]    The transfer of the registered request (context transfer) in the Event Notification mode from one AR  14  to another can be performed using the context transfer framework (see, for example, “Problem description: reasons for performing context transfers between nodes in an IP access network”, http//ietf.org/internet-drafts/draft-ietf-seamoby-context-transfer-problem-stat-04.txt).  
         [0035]    The preferences of MN can either be explicitly registered by MN with AR_current or can be retrieved from MN&#39;s profile stored in the AAA server  18 .  
         [0036]    It should be noted that both modes of operation, Query and Event Notification (without the Event NACK and Event Notification (Response) steps) may also be used in the CAR discovery protocol for the MN  16  to register its preferences with AR_current  16 . Knowledge of the MN  16  preferences may be useful to AR_current in selecting the CAR for the MN&#39;s handoff.  
         [0037]    While these teachings have been particularly shown and described with respect to preferred embodiments thereof, it will be understood by those skilled in the art that changes in form and details may be made therein without departing from the scope and spirit of these teachings.