Patent Publication Number: US-2007110021-A1

Title: Method and system for directing a call for a mobile station to a band class in a wireless communication network

Description:
FIELD OF THE INVENTION  
      The invention relates generally to wireless communication networks. More specifically, the invention relates to directing a call for a mobile station to a band class in a wireless communication network.  
     BACKGROUND OF THE INVENTION  
      Existing Code Division Multiple Access (CDMA) technology for a wireless communication network comprises a plurality of band classes, for example, a first band class and a second band class. A band class is associated with a particular frequency bandwidth and a particular signal modulation scheme and is used for communication in the wireless communication network. For example, a band class may be a 700 Megahertz (MHz) band class or a 1600 MHz band class. If the second band class has the capacity, the first band class sends an Extended System Parameter Message (ESPM) with an alternate band (ALT_BAND) indicator to a mobile station (MS) initiating a call to indicate that the second band class has the capacity. If the MS supports the second band class, the MS sends an Originating Request Message (ORM) to the first band class, in response to receiving the ESPM with the ALT_BAND indicator.  
      The wireless communication network then determines if an overload condition exists on the first band class. If so, an Extended Channel Assignment Message (ECAM) is sent through the first band class to the MS. The MS then uses a paging channel and sends an ORM to the second band class. The wireless communication network assigns the respective resources and sends an ECAM from the second band class to the MS. The MS is then moved from the shared channel to the traffic channel on the second band class. As a result, the conventional call setup process requires the transaction of multiple messages between an MS and the wireless communication network. Therefore, there is an inherent delay involved in setting up the call. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
      The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views and together with the detailed description below are incorporated in and form part of the specification, serve to further illustrate various embodiments and to explain various principles and advantages all in accordance with the invention.  
       FIG. 1  is a block diagram of a wireless communication network, in accordance with an embodiment of the invention.  
       FIG. 2  is a block diagram of the working of a wireless communication network, in accordance with an embodiment of the invention.  
       FIG. 3  is a block diagram of a wireless communication network, in accordance with an embodiment of the invention.  
       FIG. 4  is a flow diagram of a method for directing a call for a mobile station to a band class in a wireless communication network, in accordance with an embodiment of the invention.  
       FIG. 5  is a flow diagram of a method for directing a call for a mobile station in a wireless communication network, in accordance with another embodiment of the invention. 
    
    
      Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the invention.  
     DETAILED DESCRIPTION OF THE INVENTION  
      Before describing in detail embodiments that are in accordance with the invention, it should be observed that the embodiments reside primarily in combinations of method steps and apparatus components related to directing a call for a mobile station to a band class in a wireless communication network. Accordingly, the apparatus components and method steps have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.  
      In this document, relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprises,” “comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by “comprises . . . a” does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.  
      It will be appreciated that embodiments of the invention described herein may be comprised of one or more conventional processors and unique stored program instructions that control the one or more processors to implement, in conjunction with certain non-processor circuits, some, most, or all of the mobile station. The non-processor circuits may include, but are not limited to, a radio receiver, a radio transmitter, signal drivers, clock circuits, power source circuits, and user input devices. As such, these functions may be interpreted as steps of a method for directing the call during an overload in the multi band system. Alternatively, some or all functions could be implemented by a state machine that has no stored program instructions, or in one or more Application Specific Integrated Circuits (ASICs), in which each function or some combinations of certain of the functions are implemented as custom logic. Of course, a combination of the two approaches could be used. Thus, methods and means for these functions have been described herein. Further, it is expected that one of ordinary skill, notwithstanding possibly significant effort and many design choices motivated by, for example, available time, current technology, and economic considerations, when guided by the concepts and principles disclosed herein will be readily capable of generating such software instructions and programs and ICs with minimal experimentation.  
      Various embodiments of the invention provide a method and system for directing a call for a mobile station (MS) to a band class in a wireless communication network. The wireless communication network includes a plurality of band classes. The method comprises the MS idling in a first band class. The first band class is among the plurality of band classes. The method further comprises the MS receiving an overhead message. The overhead message contains an alternate band class of the plurality of band classes. Further, the wireless communication network sends the overhead message if a predetermined criteria is met on the first band class. The method further includes switching to the alternate band class in response to receiving the overhead message when the MS initiates a connection.  
       FIG. 1  is a block diagram of a wireless communication network  100 , in accordance with an embodiment of the invention. The wireless communication network  100  can be a RAN and comprises at least one base station (for example, a base station  105 ). The base station  105  comprises a transceiver  110  and a processor  115  working in conjunction to direct a call for one or more MS  120  to a band class. The base station  105  communicates with the MS  120  through a plurality of band classes  125  (for example, a band class  130  and a band class  135 ). A band class is associated with a particular frequency bandwidth and a particular signal modulation scheme and is used for communication in the wireless communication network  100 . For example, a band class may be a 700 Megahertz (MHz) band class or a 1600 MHz band class. It will be readily apparent to a person skilled in the art that the wireless communication network can have more than two band classes. In this embodiment of the invention, the MS  120  idles on the band class  130 .  
      The transceiver  110  can be adaptively coupled with the processor  115 . The processor  115  is configured to determine whether a predetermined criteria is met on the band class  130 . The processor  115  is further configured to broadcast an overhead message to the MS in response to determining that the predetermined criteria is met on the band class  130  and to receive a message from the MS  120  in direct response to the overhead message, where the message requests a call on an alternate band class (for example, the band class  135 ).  
      The overhead message contains an alternate band class of the plurality of band classes  125 . In an embodiment of the invention, the overhead message is an Extended System Parameter Message (ESPM). The ESPM may comprise an alternate band indicator (ALT_BAND indicator). The ALT_BAND indicator indicates one or more alternate band classes in the wireless communication network  100  that can be used for initiating a call by the MS  120 . The ALT_BAND indicator may also further indicate the priority of the plurality of alternate band classes in the wireless communication network  100 . The method of sending the overhead message by the wireless communication network  100  will be apparent to a person ordinarily skilled in the art.  
      In various embodiments of the invention, the wireless communication network  100  sends the overhead message (that contains the alternate band class of the plurality of band classes) if a predetermined criteria is met on the first band class. In an embodiment of the invention, the predetermined criteria comprise an overload condition on the first band class. A band class may be overloaded for example, but not limited to, if resource utilization on the band class exceeds a predetermined-threshold corresponding to the band class. Therefore, the MS may also use the overhead message to detect that the first band class is in overload conditions. In another embodiment of the invention, the predetermined criteria indicate that a predefined time interval has lapsed. For example, this can be performed periodically. In another example, this can be performed during peak hours of usage of the wireless communication network. In yet another embodiment of the invention, the predetermined criteria may be combinations thereof. For example, the predetermined criteria can be the first band class is overloaded for the predefined time interval.  
      The processor  115  may be further configured to determine priority of the plurality of alternate band classes and broadcast priority in the overhead message. In this embodiment of the invention, the ALT_BAND indicator further indicates the priority of each alternate band class. For example, if the wireless communication network  100  comprises a plurality of alternate band classes, the ALT_BAND indicator can indicate the priority of each alternate band class depending on the overload condition of each alternate band class. As a result, an alternate band class A can have a higher priority than an alternate band class B, if the alternate band class A is less overloaded than the alternate band class B. The processor  115  may also be configured to send an assignment message to the MS  120  in response to receiving an Origination Response Message (ORM) from the MS  120 . In an embodiment of the invention, the assignment message indicates allocation of traffic channel resources to the MS on the alternate band class. The assignment message can be, for example, an Extended Channel Assignment Message (ECAM). The assignment message can further comprise the frequency of the alternate band class, Pseudonoise (PN) and Walsh Code (WC). The method of sending the assignment message will be apparent to a person ordinarily skilled in the art.  
       FIG. 2  is a block diagram of an MS  200 , in accordance with an embodiment of the invention. The MS  120  may be similar to the MS  200 . The MS  200  comprises an MS-transceiver  205  and an MS-processor  210 . The MS-transceiver  205  can be adaptively coupled with the MS-processor  210 . The MS-processor  210  is configured to receive an overhead message indicating that the MS  200  uses an alternate band class when the MS  200  is idling in the band class  130 . If the MS  200  initiates a call, the MS-processor  210  is configured to determine if the MS  200  supports the alternate band class indicated by the overhead message. If the MS  200  supports the alternate band class, the MS-processor  210  is configured to send an ORM for initiating a call directly to the alternate band class in the wireless communication network  100 . In an embodiment of the invention, the MS-processor  210  is configured to send the ORM to an alternate band class based on the priority of the alternate band class indicated by the overhead message.  
      The MS-processor  210  may further be configured to switch to the alternate band class when the MS-processor  210  receives the overhead message and supports the alternate band class. The MS-processor  210  is configured to receive an assignment message from the wireless communication network  100  in response to the ORM. The assignment message can include traffic channel information and an assign mode. The MS-processor  210  is configured to then determine the traffic channel and the assign mode included in the assignment message for the call set up.  
       FIG. 3  is a block diagram of the working of the wireless communication network  100 , in accordance with an embodiment of the invention. In this embodiment of the invention, the band class  130  is in the overload condition and broadcasts an overhead message  305  to one or more MS  200 . The overhead message  305  indicates to the plurality of MS that the band class  130  is in the overload condition.  
      The MS  200  receives the overhead message  305  and continues to idle on the band class  130 . The overhead message  305  comprises the ALT_BAND indicator indicating to the MS  200  an alternate band class that is available in the wireless communication network  100 . The ALT_BAND indicator indicates to the MS  200  that the band class  135  can be used by the MS  200  to initiate the call. When the MS  200  initiates the call, the MS  200  determines if the band class  135  is supported by the MS  200 . If the MS  200  does not support the band class  135  then the MS  200  initiates the call on the band class  130 . If the MS  200  supports the band class  135 , then the MS  200  sends an ORM  310  to the band class  135  to initiate the call. The wireless communication network  100  processes the ORM  310  sent by the MS  200  and sends an assignment message  315  to the MS  200  in response to the ORM  310  sent by the MS  200 .  
       FIG. 4  is a flow diagram of a method for directing a call for a MS to a band class in a wireless communication network, in accordance with an embodiment of the invention. The wireless communication network can be, for example, a RAN. In an embodiment of the invention, the wireless communication network is a RAN in a Code Division Multiple Access (CDMA) system. The wireless communication network comprises a plurality of band classes. The MS idles  405  on a first band class (which can be for example, the band class  130 ). The first band class is among the plurality of band classes in the wireless communication network.  
      The MS receives  410  an overhead message. The overhead message contains an alternate band class (for example, the band class  135 ) of the plurality of band classes. In an embodiment of the invention, the overhead message is an ESPM. The ESPM may comprise an ALT_BAND indicator. This has been explained in detail in conjunction with  FIG. 1 . In various embodiments of the invention, the wireless communication network sends the overhead message (that contains the alternate band class of the plurality of band classes) if a predetermined criteria is met on the first band class. The predetermined criteria have been explained in detail in conjunction with  FIG. 1 .  
      The MS switches  415  to the alternate band class in response to receiving the overhead message when the MS initiates the call. This is further explained in conjunction with  FIG. 5 .  
       FIG. 5  is a flow diagram for directing a call for a MS in a wireless communication network, in accordance with another embodiment of the invention. A MS idles  505  in a first band class. The MS receives  510  the overhead message from the wireless communication network. The overhead message contains an alternate band class of the plurality of band classes. For example, the overhead message may be an ESPM that comprises an ALT_BAND indicator. The MS then checks the overhead message to determine one or more alternate band class in which to operate. The MS then determines  515  whether the MS supports one or more alternate band class. If the MS does not support one or more alternate band class, the MS then sends  520  a message to the wireless communication network indicating that the MS does not support the at least one alternate band class.  
      However, if the MS supports one or more alternate band class, then the MS switches  525  to an alternate band class when the MS initiates a connection with the wireless communication network. In an embodiment of the invention, if the wireless communication has a plurality of alternate band class and one or more alternate band classes are determined to be supported by the MS, the MS then switches to an alternate band class that has a higher priority. To switch, the MS sends  530  an ORM to the alternate band class for initiating the call and receives  535  an assignment message for the alternate band class.  
      Various embodiments of the invention provide a method and a system to reduce the call set up duration as the MS sends an ORM directly to the alternate band class. Further, the various embodiments of the invention provide a method and system in which load on the wireless communication network is balanced without migrating the idle MS from the first band class to the alternate band class. Also, no registrations are involved before call setup procedure. As result, there is a reduction in the re-registration process in the wireless communication network.  
      In the foregoing specification, specific embodiments of the invention have been described. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the invention. The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential features or elements of any or all the claims. The invention is defined solely by the appended claims including any amendments made during the pendency of this application and all equivalents of those claims as issued.