Abstract:
A system connected to a mobile station through a network and allocating a radio source to the mobile station for packet data service, the system including a base station connected to the mobile station through a wireless network, and having a physical layer connected to the mobile station through a wireless network and performing wireless access and a medium access control (MAC) layer performing service-specific resource allocation for the mobile station; and a control station having an upper layer connected to the base station through a wired network and receiving a result of service-specific resource allocation from the MAC layer, and performing as an interface between networks.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application claims priority to and the benefit of Korea Patent Application No. 10-2004-0108243 filed on Dec. 17, 2004 in the Korean Intellectual Property Office, the entire content of which is incorporated herein by reference. 
   FIELD OF THE INVENTION 
   The present invention relates to a radio resource allocation system and an allocation method thereof, and more particularly to radio resource allocation and an allocation method for packet data services. 
   BACKGROUND OF THE INVENTION 
   When a mobile station requests a circuit-based call, a base station requests permission of resource allocation for the call from a control station. In other words, the control station manages radio resources for setting calls, and thus the permission by the control station is a prerequisite for controlling the calls (i.e., setting-up and release) for the mobile station that accesses the base station. With the permission of setting up the call, the mobile station occupies a given circuit until the call is disconnected. 
     FIG. 1  illustrates a structure of a conventional circuit-based mobile communication system. 
   As shown therein, the system includes a mobile station (MS)  30 , a base station (BS)  10  providing the MS  30  with wireless access, and a control station (CS)  20  controlling the BS  10  through a wired network connection. 
   The CS  20  performs radio resource allocation while considering inter-cell interference in different BSs, interfacing between networks, and collecting statistical data of radio resources. 
   In detail, the CS  20  receives a resource request from the MS  30 , and manages the radio resources related to setting-up/releasing the calls and use of additional radio resources. In addition, the CS  20  collects statistical data of the radio resources to distinctively distribute the radio resource for each cell in consideration of the interference between the cells. 
   The CS  20  includes a medium access control (MAC) layer  21  and an upper layer  22 . 
   The BS  10  that receives a request for primary radio resource allocation from the MS  30  and transmits the request to the CS  20 , and includes a physical layer  11  and a physical layer controller  12 . 
     FIG. 2  illustrates a method for allocating a radio resource in the conventional circuit-based mobile communication system. 
   As shown therein, a request for radio source allocation is transmitted to the physical layer controller  12  of the BS  12  from the MS  30  in Step S 10  and transmitted to the MAC layer  21  of the CS  20  by the physical layer controller  12  in Step S 11 . The upper layer  22  receives the request from the MAC layer  21  in Step S 13 , permits the request while considering the inter-cell interference in different BSs in Step S 14 , and then allocates the corresponding radio source to the MS  30  through the physical layer controller  12 . 
   However, an existing method for allocating a radio channel is inappropriate for packet transmission since the packet does not have a given occupancy time, and multiple users share a single circuit in the packet-type radio data communication service. In particular, it is difficult to apply the existing radio channel allocation method considering the inter-cell interference to the packet-based radio data communication service because the interference within the cell varies depending on the time and the amount of packets in the packet-based communication service. 
   Thus, the packet-based radio communication service requires another radio resource allocation method that is different from the existing method since the packet-based radio communication service is designed to provide massive data to multiple users that access a single circuit. 
   A MAC layer of the BS manages user information to provide a satisfactory service to a user, and thus the IEEE 802.16 manages a user identifier by using a service flow identifier (SFID), a connection identifier (CID), and a medium access control identifier (MAC ID). In other words, the MAC layer perceives a user with reference to a corresponding relationship between the MAC ID, SFID, and CID. In such a conventional method, however, identification of a user is complicated and a change in the status of service is not considered. Thus more simplified methods for managing the user ID and controlling the user according to the service-specific status are required. 
   The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention, and therefore, unless explicitly described to the contrary, it should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known in this country to a person of ordinary skill in the art. 
   SUMMARY OF THE INVENTION 
   The present invention has been made in an effort to provide a radio source allocation system for a packet data service and a method thereof having an advantage of solving problems of the conventional method. 
   An exemplary radio source allocation system for the packet data service according to an embodiment of the present invention includes a system connected to a mobile station through a network and allocating a radio source to the mobile station for packet data service. The system includes a base station and a control station. The base station is connected to the mobile station through a wireless network and includes a physical layer for radio access to the mobile station and a medium access control (MAC) layer for allocating a service-specific resource to the mobile station when receiving a service-specific resource allocation request from the mobile station. The control station includes an upper layer connected to the base station through a wired network and receiving a result of service-specific resource allocation from the MAC layer, and interfaces with networks. 
   When the MAC layer receives a service-specific resource request from the mobile station, the MAC layer may allocate a resource for the corresponding service when there is a resource left for the requested service. 
   When the mobile station is located on a cell boundary, the MAC layer may allocate a service-specific resource to the mobile station by using a predefined allocatable resource. 
   The MAC layer may manage a user based on a change in the service status of the user. 
   The MAC layer may identify a service for a user by using a medium access identifier (MAC ID) assigned during an authentication process of the mobile station and a status identifier mapped to the MAC ID. 
   The status identifier may include a sleep identifier (ID) for the mobile station in the sleeping status, and a waiting ID for the mobile station in the waiting status. 
   In a further embodiment of the present invention, there is provided a method for allocating radio sources for a packet data service in a radio resource allocation system that includes a base station having a medium access control (MAC) layer for allocating a radio source to a mobile station and a control station connected to the base station. In the method, a) the MAC layer receives a service-specific resource request from the mobile station, b) the MAC layer allocates a service-specific radio source to the mobile station in response to the request, and c) the MAC layer reports a result of the service-specific resource allocation performed in b) to the control station. 
   In b), the residual resource may be allocated to the corresponding service when there is a residual resource for the requested service. 
   b) may include determining whether a resource is left for the requested service, determining whether the mobile station is located on a cell boundary when the resource is left for the request service; and allocating a resource from among predefined allocatable resources when the mobile station is located on the cell boundary, and allocating a resource from among allocatable resources when the mobile station is not located on the cell boundary. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  illustrates a structure of a circuit-based conventional mobile communication system. 
       FIG. 2  illustrates a method for allocating radio resources in the circuit-based conventional mobile communication system. 
       FIG. 3  illustrates a structure of a packet-based mobile communication system according to an exemplary embodiment of the present invention. 
       FIG. 4  illustrates a method for allocation of radio resources in the packet-based mobile communication system according to an exemplary embodiment of the present invention. 
       FIG. 5  illustrates a flow of the method of  FIG. 4  in more detail. 
       FIG. 6  illustrates a relationship between a packet classifier of an upper layer and a memory of a MAC layer. 
       FIG. 7  illustrates an identifier mapping relationship according to an exemplary embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE EMBODIMENTS 
   In the following detailed description, only certain exemplary embodiment of the present invention has been shown and described, simply by way of illustration. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not restrictive. 
   A MAC layer is set to manage a mobile station and allocate radio sources, and thus utilizes user information that sensitively changes depending on the radio channel condition according to an exemplary embodiment of the present invention. Thus, the MAC layer is included in the BS rather than included in the CS, and is located close to a physical layer. 
     FIG. 3  illustrates a structure of a packet-based mobile communication system according to an exemplary embodiment of the present invention. 
   As shown therein, the system includes a base station (BS)  100  accessed by a mobile station (MT)  300 , and a control station (CS)  200  controlling the BS  100  through a wired network connection. 
   The CS  200  interfacing with a network includes an upper layer  210 . 
   The BS  100  includes a physical layer  110  for radio access with the MT  300 , and a medium access control (MAC) layer  120  for allocating the corresponding resource when resource allocation is requested. 
   In other words, the structure of the packet-based mobile communication system is bisectional such that the MAC layer  120  mainly manages users using packet data and radio sources, and the CS  200  mainly performs network-related functions. 
     FIG. 4  illustrates a method for allocating a radio source in the packet-based mobile communication system according to an exemplary embodiment of the present invention. 
   Referring to  FIG. 4 , the MAC layer  120  of the BS  100  receives a service-specific resource request from the MS  300  in Step S 100 . The MAC layer  120  allocates a service-specific resource to the MT  300  in response to the request in Step S 120 , and reports a result of the service-specific resource allocation to the upper layer  210  of the CS  200  in Step S 120 . In other words, the upper layer  210  receives the result of the resource allocation from the MAC layer  120  rather than directly allocating the resource or setting-up/releasing the MT  300 . 
   The MAC layer  120  of the BS  100  grants a user service when there is a resource presently left for the requested service. For example, the MAC layer  120  cannot grant the resource allocation request for the user requesting resource allocation for a video service when there is a resource left for a packet voice service. 
   When resource allocation is requested as described above, the resource allocation is granted in consideration of interference of a user to a cell in a conventional circuit-based system, but a user service request is granted when there is a residual resource according to an exemplary embodiment of the present invention because it is difficult to calculate general interference of each user service that requires a different amount of traffic depending on the radio channel condition in the packet-based system. However, each cell is informed of allocatable resources within each cell boundary during initialization of each base station to thereby avoid inter-cell interference. The inter-cell interference may be reduced by using pre-defined allocatable resources since the radio channel condition becomes poor on the cell boundary. Further, a process for using the pre-defined allocatable resources according to the embodiment of the present invention is similar to a process for distributing resources to each user in consideration of the inter-cell interference. 
     FIG. 5  illustrates a flowchart of a resource allocation method performed by the MAC layer  120  according to an exemplary embodiment of the present invention in more detail. 
   The MAC layer  120  of the BS  100  receives a resource allocation request for a service from the MT  300  in Step S 11 , and checks whether there is a resource left for the service in Step S 112 . When there is a residual resource for the service, the MAC layer  120  checks whether the MT  300  is located on the cell boundary in Step S 113 . 
   When the MT  300  is located on the cell boundary, the MAC layer  120  allocates a resource from among predefined allocatable resources in Step S 114 , but the MAC layer  120  allocates a resource from among allocatable resources in Step S 115  when the MT  300  is not located on the cell boundary. 
   When there is no residual resource for the requested service, the MAC layer  120  reports a message to the MT  300  to inform that the resource allocation of the requested service is not granted in Step S 116 . 
     FIG. 6  illustrates a relationship between a packet classifier of the upper layer  210  and a memory of the MAC layer  120 . 
   The CS  200  classifies data packets, and transmits the classified packets to the MAC layer  120 . The MAC layer  120  identifies the packets according to user-specific priorities. 
   As shown in  FIG. 6 , the MAC layer  120  reclassifies the data packets transmitted from the upper layer  210  into a data packet  410  for a user UID 1 , a data packet  420  for a user UID  2 , a data packet  430  for a user UID  3 , and a data packet for a user UID  4  and stores the re-classified data packets in the memory. 
   Herein, the MAC layer  120  identifies types of user-specific services according to quality of service (QoS), and prioritizes the user-specific services considering an optimized radio channel allocation time, an occupancy time in service-specific queues, an arrival time of packets, and packet occupancy in the service-specific queues for each user rather than indiscriminately prioritizing the services according to the QoS. 
   An identifier according to an exemplary embodiment of the present invention will be described. 
   Status of a user may be variously defined (i.e., waiting, busy, or idle), and a packet-based transmission user may use more than one service. Therefore, the status of the user is defined depending on services. In particular, when the user uses a voice packet service and an Internet service, the Internet service may be in the busy status but the voice packet may be in the waiting status for a while, and then an associated call may be disconnected. 
   Therefore, information on the status of a service-specific user becomes an important factor for determining a type of user management for packet transmission. The status may be defined for different purposes so as to be used for managing services of the users. For example, information on a user in the busy status is required for controlling packet retransmission, and information on a user in the waiting status is required for a scheduler to determine priority. 
   User management is performed based on changes in the status of the service-specific users according to an exemplary embodiment of the present invention. Thus, a change in a method for assigning an identifier may be required to manage the users according to the changes in the status of the users. 
   According to an exemplary embodiment of the present invention, a method for identifying service-specific users uses a medium access control identifier (MAC ID) assigned during an authentication process for a user&#39;s mobile station, and a status identifier mapped to the MAC ID. Service status of users is identified as sleep status and waiting status. The waiting status represents that the corresponding service of the user is waiting for transmission, and the sleep status can be applied to the following cases: when the mobile station is turned on without requesting resource allocation; when no resource allocation is continuously requested for a given period of time after receiving a service by using a previously allocated resource; when too many users request resource allocation and thus the corresponding service is disconnected; and when no resource is allocated from the earlier stage. Finite sleep IDs assigned to user services in the sleep status are different from each other, and each service user changes its status and periodically reports radio channel information by using an associated sleep ID. 
     FIG. 7  illustrates a mapping relationship of the identifier according to an exemplary embodiment of the present invention. 
   As shown therein, the MAC layer  120  receives voice packets  510 , video packets  520 , and Internet packets  530  from the upper layer  210 . 
   The MAC layer  120  uses an identifier in a format of a MAC ID-Sleep ID to differentiate user services when transmitting/receiving control information on the a user service in the sleep status. 
   The user service requesting radio sources is considered to be in the waiting status and thus a finite waiting ID  630  is assigned to the user service. 
   The MAC layer  120  uses an identifier in a format of a MAC ID-Waiting ID to differentiate user services when transmitting/receiving control information on the user services in the waiting status. 
   In other words, each user service belongs to one status identifier, and the MAC layer  120  uses two combinations of the MAC ID ( 610 ) and the status identifiers (Sleep ID ( 620 ) and Waiting ID ( 630 )) to receive/transmit the control information by applying a different status identifier to each user service. 
   The status identifier of the user service is variable and is forcibly changed to another status identifier according to the change in the status. For example, if a user of the Internet user service and the voice packet user service does not request a resource for the Internet service, the status of the user is forcibly changed to thereby extend a chance for another user service. 
   The MAC layer  120  transmits a status change message to the MT  300 , and identifies the user service by using a combined identifier to avoid complexity due to the change of the variable status identifier. In addition, the MT  300  possesses a different status identifier for each user service and transmits/receives the control information by using a status identifier corresponding to the changes in the status of the user service. 
   As previously described, the upper layer  210  controls the MAC layer  120  to manage a radio source rather than directly allocates the radio sources or sets/releases the MT to reduce waste of time due to duplicate functions between layers to thereby efficiently control the system. 
   In addition, a method for user management is provided in consideration of service-specific status of each user rather than equally applying quality of service (QoS) to various types of services, thereby improving massive packet data transmission and increasing capacity. 
   Further, the MAC layer uses an identifier that is simple and unique, and is flexible to a change in the status, and thus management of identifiers for user services becomes easy to thereby offer chances of service for multiple users. 
   While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiment, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.