Abstract:
A system and method are provided by which a wireless network service provider is able to provide and maintain a high level of quality of service for terminals in the corresponding network, by overcoming problems that result in a diminished quality of service, including handoff delays as terminals move between cells in a network and the uncertainly as to which cell the individual terminals are moving to as they roam within the network. Providing and maintaining a high level of quality of service in a wireless network includes recording a history of movements of a terminal within the wireless network, analyzing the movements of the terminal within the wireless network to compute a probability distribution of the terminal&#39;s target location, and allocating network resources, including bandwidth and priority scheme, to the terminal based on the probability distribution for the terminal.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to wireless networks. More particularly, the invention relates to managing the quality of service (hereafter “QoS”) in a wireless network. 
     As the use of mobile terminals in wireless networks increases, a serious challenge confronting wireless network service providers is providing and maintaining a high quality of services for their subscribers. In particular, in view of the expanding range of applications for mobile wireless terminals (which will be referred to simply as “terminals” henceforth), including video, audio and text applications, wireless network service providers must allocate sufficient bandwidth and assign appropriate scheduling (e.g., priority) schemes to the traffic of subscribing terminals on the end-to-end path of traffic across the network. The allocation of bandwidth determines the transfer speed of a terminal&#39;s application traffic across the network, and the scheduling determines the order of processing and transmission of the different application&#39; traffic at network nodes. Examples of such network nodes include, but are not limited to, base stations and routers. A priority scheme provides an example of such scheduling, by providing one type of traffic precedent over another. For instance, in a network that supports both voice and data traffic, the priority schemes may assign voice traffic priority over data traffic. As a result the nodes in the example network transmit voice traffic packets before they transmit data packets. However, meeting this QoS challenge is made more difficult by the ever-increasing volume of network traffic, and the fact that the terminals are usually roaming around a given network and frequently change their points of connection to the network. 
     The challenge, noted above, of providing and maintaining the QoS in a wireless network is a difficult one due to the fact that the terminals are often roaming around the network and frequently change their points of attachment to the network. 
     As an example, consideration is given to a communication between the terminals of two subscribers to the services of a particular network, whereby at least one of the subscriber terminals is a mobile terminal. When a first terminal, which is a mobile terminal, attempts to contact the other subscriber terminal, which may be referred to as the “corresponding terminal”, an end-to-end connection traversing a wireless/wireline infrastructure having sufficient resources, as well as an appropriate scheduling scheme is established between the two terminals. The end-to-end connection begins in the mobile terminal&#39;s present location in its present cell, which will be referred to as the “serving cell” hereafter. QoS for such connection is easily maintained so long as the mobile terminal remains in the serving cell. 
     However, as the mobile terminal moves from its serving cell to another cell, which will be referred to as a “target cell” hereafter, within the network, the network connection to the mobile terminal is handed off from the serving cell to the target cell. The hand off from the serving cell to the target cell interrupts the end-to-end connection between the two terminals, and thus QoS then becomes an issue of concern, for both the terminal users and the network providers. 
     In order to maintain a high level of QoS and to further ensure minimal disruption of an ongoing communication session, a new end-to-end connection that has sufficient bandwidth and an appropriate priority scheme must be established from the target cell between the mobile terminal and the corresponding terminal as quickly as possible. 
     Presently, maintaining a high level of QoS for an ongoing communication session by providing sufficient bandwidth and an appropriate priority scheme is not ensured after handoff from a service cell to a target cell due to at least a handoff delay or a bandwidth deficiency in the target cell. A handoff delay occurs when the time taken to set up a new end-to-end connection between the mobile terminal in the target cell and the corresponding terminal is so great that the communication session is disrupted, if not terminated altogether. Further, a bandwidth deficiency in the target cell prohibits completion of the connection between the mobile terminal and its corresponding terminal. As a result the communication session may be terminated because there is no transfer of information between the mobile terminal and its corresponding terminal. 
     Interruptions in communication sessions, in particular, may often be attributed to the network traffic management system not having sufficient notice of the target cell to which the mobile terminal is moving in time for the handoff to be handled efficiently. As a result, sufficient resources are not assured for the roaming terminal in a timely manner after the handoff to the target cell. 
     Thus, there is a need for a systems and technique that ensures that a high level QoS is provided and maintained for a mobile terminal&#39;s applications as the mobile terminal roams throughout a wireless network, the quality-of-service pertaining to, for example, the provision of sufficient bandwidth and appropriate priority schemes. 
     SUMMARY OF THE INVENTION 
     Thus, the present invention provides a system by which a wireless network service provider is able to provide and maintain a high level QoS for terminal&#39; applications in the network, by overcoming the problems that result in a diminished quality of service, including handoff delays as terminals move between cells in a network and the uncertainly as to which cell the individual terminals are moving to as they roam within the network. 
     According to the present invention, providing and maintaining a high level of quality of service, which has threshold requirements, in a wireless network may include (a) recording a history of movements of a mobile terminal within the wireless network, (b) analyzing the movements of the mobile terminal within the wireless network to produce a probability distribution of the mobile terminal&#39;s target location, (c) predicting the target cell for the mobile terminal using the probability distribution of the mobile terminal&#39;s target location, and (d) transferring the context of the mobile terminal&#39;s ongoing communication session to the predicted target cell for allocating appropriate network resources thereto, including bandwidth and priority scheme. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The scope of the present invention will be apparent from the following detailed description, when taken in conjunction with the accompanying drawing. The detailed description, while indicating preferred embodiments of the invention, are given as illustrations only since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description, in which: 
         FIG. 1  shows an example of a wireless network in which the present invention may be utilized. 
         FIG. 2  is a flowchart showing an example of a method according to the present invention. 
         FIGS. 3   a  and  3   b  are examples of cells within wireless networks in which the present invention may be utilized. 
     
    
    
     DETAILED DESCRIPTION 
     In the detailed description to follow, example embodiments and values may be given, although the present invention is not limited thereto. Further, while example embodiments of the present invention will be described in conjunction with a system and method for managing quality of service (which will be referred to as “QoS” hereafter) in wireless networks as an example, practice of the present invention is not limited thereto, i.e., the present invention can be implemented in conjunction with any network. 
       FIG. 1  shows an example of a wireless network in which the present invention may be utilized. The example wireless network of  FIG. 1  may include a plurality of cells  2   a ,  2   b  and  2   c  that may provide a mobile terminal (hereinafter “terminal”) that belongs to a subscriber of services provided by the network service provider with access to the network infrastructure, which may include, but is not limited to, an internet provider (IP) infrastructure. Each of base stations BS 1 , BS 2  and BS 3  may serve as a transmitting and receiving station for terminals in the respective cells  2   a ,  2   b  and  2   c . The terminals may include, but are not limited to, telephones, pagers other wireless transmitting and receiving systems. Therefore, based upon the services offered by the respective network service providers, the respective base stations BS 1 , BS 2  and BS 3  may or may not serve as an IP router, that is, the respective base stations may or may not have IP routing and processing capabilities. 
     Access gateways AG 1 , AG 2  and AG 3 , which may be provided for the respective cells  2   a,    2   b  and  2   c , are edge IP routing and control entities that connect one or more of the base stations BS 1 , BS 2  and BS 3  to the network  1 . However, beyond the example network of the present application, it is noted that an access gateway may actually connect several base stations to a network, and further, in no way is the present invention limited to a network having only three cells or even a one-to-one ratio of base stations to cells. 
     The role of access gateways according to the present invention will be described by way of example only. For instance, if it has been determined that an ongoing communication session between a mobile terminal  4  and its corresponding terminal  6 , which may be a mobile terminal or a fixed wire terminal, requires handoff from serving cell  2   b  to target cell  2   a , the session context may be transferred from the access gateway  5   b  in the serving cell  2   b  to the access gateway  5   a  in the target cell  2   a . The session context may include the radio resources and/or state information that is used to establish a connection for supporting an ongoing communication session. The access gateway  5   a  in the target cell  2   a  may use the transferred session context to establish a connection with sufficient resources between itself (i.e., the access gateway  5   a ) and the corresponding terminal  6  as well as reserve necessary resources in the target cell  2   a  so that a new end-to-end connection between the mobile terminal  4  and the corresponding terminal  6  is available for the ongoing communication as soon as the handoff to the target cell  2   a  occurs. 
     The network  1  may further include geographic location manager (GLM)  3  that is a control/management entity for network  1 . GLM  3  may receive and store information pertaining to the geographic location of active or registered terminals. Such information pertaining to the geographic location of active or registered terminals may be gathered from satellite positioning systems including, but not limited to, the Global Positioning System (GPS), which is well known in the art of communications. For the present description, reference will be made to GPS, although the present invention is not limited to use of only GPS. 
     For a subscriber who requests the QoS assurance provided by the present invention, the GLM  3  may gather GPS information regarding the geographic location of a mobile terminal  4  in the network  1  to which the terminal is registered. Based on the gathered information, the GLM may compute a probability density function, which is a normalized histogram, of the exact location of the active subscriber mobile terminal  4 . The histogram may be refined with each additional geographic location update of the subscriber mobile terminal  4 , which may occur, for example, every time the subscriber mobile terminal  4  re-registers with the network operator (not shown) of network  1  as the subscriber mobile terminal  4  moves from one cell to another, from cell  2   a  to  2   b  in  FIG. 1 , or at predetermined time intervals. The GLM  3  may provide normalized histograms regarding the geographic location of subscriber mobile terminal  4  across network  1  to the network operator, which may include, but is not limited to, the transport entities of the respective cells, which include, but are not limited to, AG 1 -AG 3 . 
     Explanation of an example embodiment of invention will now be further explained in reference to the flow chart of  FIG. 2 . The example embodiment further refers to  FIG. 1  in which a registered terminal, which is subscribed to a particular network, moves among cells  2   a  through  2   c  in the network  1 , although the present invention and application thereof is in no way limited thereto. In addition, the example embodiment of the invention may be implemented by a program run by the network entities described herein. 
     After subscribing to the services offered by the network services provider associated with network  1 , as mobile terminal  4  moves among cells  2   a  to  2   c  in the network  1 , GLM  3  may gather information from GPS to monitor all movement of the mobile terminal  4  within the network  1  and may further maintain such tracking information in a GLM database, as in step  200 . With each recorded movement of the mobile terminal  4  within the network  1 , or at predetermined time intervals, GLM  3  may update a normalized histogram as in step  220 , which includes a probability distribution of the exact movements of the mobile terminal  4  among the adjacent ones of cells  2   a  through  2   c.  GLM  3  may continue to monitor movement of the mobile terminal  4  in network  1 , as in step  220 , and with each recorded movement of the mobile terminal  4  within the network  1 , or at predetermined time intervals, GLM  3  may transmit the updated histogram for mobile terminal  4  to the network operator of network  1 . 
     Thus, a normalized pattern for the movement of mobile terminal  4  within the network  1  may be established. The histograms may include information regarding the movement pattern of mobile terminal  4  among adjacent ones of cells  2   a  through  2   c  in the network  1 . Accordingly, the services provided by the present invention may have significant appeal to commuters, couriers, or any other people who have regular commuting or traveling habits, though application of the present invention is in no way limited thereto. 
     As shown in step  240 , QoS management according to the present invention may use the mobility history of mobile terminal  4  obtained in step  220  to predict the adjacent target cell that the ongoing communication session between the mobile terminal  4  and its corresponding terminal  6  will be handed off to. Thus, as mobile terminal  4  moves from cell  2   a  to cell  2   b , in the example of  FIG. 1 , AG  5   a  may transfer the necessary context (e.g., the traffic descriptor of the present connection between mobile terminal  4  in cell  2   a  and network  1 ) to AG  5   b , which is the target AG, so that AG  5   b  has sufficient time to reserve the necessary resources and mechanisms, including appropriate priority schemes, so that handoff of the ongoing communication session from AG  5   a  to AG  5   b  may be completed quickly, with minimal delay and minimal performance degradation. 
     QoS management according to the present invention may be predicated upon a mobility matrix of the mobile terminal  4  among the adjacent cells  2   a  through  2   c  in network  1 . The mobility matrix is computed as part of the analysis in step  220  of  FIG. 2 . In accordance with the description set forth above, GLM  3  may obtain a mobility matrix by computing the normalized histogram of movements of mobile terminal  4 , as well as every other terminal in the network, from cell to cell within network  1 . GLM  3  updates the mobility matrix upon each transition of a mobile terminal between cells. The network operator may maintain either a mobility matrix per user that reflects each terminal&#39;s specific mobility history or an aggregated mobility matrix that reflects the collective mobility pattern of all terminals in the network. In addition, the mobility matrix may be computed based on the history taken at the same time of the day, week or even month of the year, to thereby ensure that the mobility matrix reflects the temporal and spatial behavior of the terminals. The temporal behavior specifically represents the movement pattern of the mobile terminals during a particular time of day and the spatial behavior represents the movement patterns of mobile terminals regardless of the time of day. 
     The mobility matrix, which provides a probability that mobile terminal  4  will move to a target adjacent cell is given as:
 
 P=[p ( n|k )], wherein 1 &lt;n  and  k&lt;M;  
 
     For the mobility matrix, the cells within the network  1  are labeled 1 through “M”; “p(n|k)” denotes the probability of the movement of mobile terminal  4  from cell k to cell n; “k” is the present cell in which mobile terminal  4  is located; and “n” is a target adjacent cell. 
     For instance, with regards to the example wireless network of  FIG. 3   a , which includes network  11  and seven micro cells  21 - 27 , the a 7×7 mobility matrix is computed as follows: 
     
       
         
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
             
             
               
                 0 
                 0.2 
                 .05 
                 0.5 
                 0.2 
                 0.01 
                 0.04 
               
               
                 0.5 
                 0 
                 0.4 
                 0 
                 0 
                 0 
                 0.1 
               
               
                 0.3 
                 0.3 
                 0 
                 0.4 
                 0 
                 0 
                 0 
               
               
                 0.3 
                 0 
                 0.3 
                 0 
                 0.4 
                 0 
                 0 
               
               
                 0.6 
                 0 
                 0 
                 0.1 
                 0 
                 0.3 
                 0 
               
               
                 0.5 
                 0 
                 0 
                 0 
                 .05 
                 0 
                 0.45 
               
               
                 0.45 
                 0.45 
                 0 
                 0 
                 0 
                 0.1 
                 0 
               
               
                   
               
             
          
         
       
     
     For the wireless network shown in  FIG. 3   b  having network  40 , macro-cell  34  and micro cells  31 - 33 , a 4×4 mobility matrix is computed as follows: 
     
       
         
               
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
             
             
               
                   
                 0 
                 .3 
                 .2 
                 .5 
               
               
                   
                 .2 
                 0 
                 .2 
                 .6 
               
               
                   
                 .3 
                 .2 
                 0 
                 .5 
               
               
                   
                 .2 
                 .4 
                 .4 
                 0 
               
               
                   
                   
               
             
          
         
       
     
     Once GLM  3  has computed the mobility matrix, as in step  220 , a decision regarding a target cell, or cells, from the present cell k to one of its “L” adjacent cells is a “L hypothesis test” ( 240 ). If φ is a set of the L neighboring cells of cell k, the target cell tεφ is the cell that maximizes p(n|k)| n=t ; {nεφ}. That is, the target cell “t” may be the cell that maximizes the likelihood test. It should be noted that the computation of the target cell may actually result in multiple target cell. That is, the highest likelihood that the terminal may move from its present cell to more than one other target cell may be equal. 
     Therefore, if mobile terminal  4  is in cell  21  of  FIG. 3   a , the first row of its mobility matrix in Table 1 indicates that the target cell may be cell  24 . However, for instance, if the mobile terminal  4  is in cell  27 , the target cell may be either of cell  21  or  22 . In the example of  FIG. 3   b , the mobility matrix in Table 2 may indicate that if mobile terminal  4  is in macro cell  34 , it is equally likely to end up in any of cells  2  or  3 , whereas if the mobile terminal  4  is in micro cell  31 , its target cell may be macro cell  34 . 
     After the target cell, or cells, “t” has been determined in the manner described above in step  240 , the access gateway AG of the cell in which mobile terminal  4  is currently located forwards the necessary connection information to the access gateway(s) AG(s) of the target cell(s). Therefore, in the example of  FIG. 1 , step  260  of  FIG. 2  may include AG  5   a  transmitting the session context (e.g., traffic descriptor, etc.) of the present connection between mobile terminal  4  in cell  2   a  and network  1 , including bandwidth requirements and priority scheme, to AG  5   b  of cell  2   b , if cell  2   b  is found to be the cell that maximizes the probability function set forth above. 
     Continuing with the example of  FIG. 1 , AG  5   b , which is the target access gateway in the target cell  2   b , may serve as a resource management proxy on behalf of mobile terminal  4  to ensure that the handoff is without delay and diminishment of parameters. If the target cell(s) does not have sufficient resources to ensure a high level of QoS for the connection between mobile terminal  4  and network  1 , AG  2   b  may transmit a message to mobile terminal  4  to so inform the user thereof, so that the user of mobile terminal  4  may decide whether to terminate the connection, to remain in cell  2   a  or to take continue roaming in another direction. 
     Upon handoff of the connection for mobile terminal  4  to the target cell, GLM  3  may update the mobility matrix accordingly to support the roaming of mobile terminal  4  within network  1 . 
     The present invention is predicated, in part, upon a probability distribution of a mobile terminal&#39;s movements across a wireless network. Thus, it may predict a target cell with a certain statistical accuracy/confidence and “guarantees” the handoff QoS with a certain statistical assurance/confidence, though not with absolute certainty. 
     This concludes the description of the example embodiments. Although the present invention has been described with reference to illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the scope and spirit of the principles of the invention. More particularly, reasonable variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the foregoing disclosure, the drawings and the appended claims without department from the spirit of the invention. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.