Abstract:
The present invention relates to a method for assigning a radio resource to a mobile station that requests a data service by collecting radio resources at a constant rate from mobile stations being served by a base station apparatus with a 1xEV-DO system. Especially, the present invention is appropriate for managing radio resources more efficiently and for improving the quality of service, by collecting part of the radio resource assigned to a mobile station having a lower service grade, among other mobile stations in service, assigning the collected radio resource to a mobile station that requested a data service, and providing the data service to the mobile station based on the assigned radio resource.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method for assigning a radio resource to a mobile station by collecting a radio resource at a constant rate from another mobile station being served by a base station apparatus having a 1xEV-DO system. 
     2. Background of the Related Art 
     In general, an IS-95 based mobile communication system provides voice-centered services. Recently, however, thanks to the development of the 1xEV-DO wireless protocol, which is a forward link providing the maximum 2.4576 Mbps high speed packet data service, the mobile communication system is now able to provide multimedia services, such as IMT-2000 service as well as high speed packet data service, moving image service, and further packetized voice service. 
     The 1xEV-DO system is not focused on providing voice-centered services like IS-95. Rather, it is aiming to provide high speed packet data services only. Specifically, the data source of each mobile station varies depending on the wireless environment. The high speed data in a forward link is first loaded into a time slot that is segmented into 1.67 ms units and is transmitted through time division communication. 
     Therefore, to process high speed data traffic, the base station apparatus of the 1xEV-DO system needs to be able to increase the data transmission rate in a cell, based on resource capabilities, and to assign forward link resources to users at any time there is a data service request from a mobile station. Particularly, to maintain a designated frame error rate (hereinafter, abbreviated to FER), the base station apparatus sets a limit on the forward link capacity so that the forward link transmits data at a rate less than a maximum data processing capacity within a cell and performs scheduling through scheduling attempts using various types of appropriate methods. 
       FIG. 1  is a block diagram of a mobile communication system in a related art. Referring to  FIG. 1 , the mobile communication system manages a mobile station  11  and includes a base station  10 , which provides data services. Mobile station  11  requests data services from base station  10  and receives the corresponding data services. Here, the base station manages a plurality of mobile stations  11   a  through  11   c  included in a cell. 
     Base station  10 , in order to manage, utilize and assign available resources more efficiently, ranks the services according to the characteristics of a data call requested from mobile station  11   a . That is, base station  10  ranks the priority of a mobile station and the service priority. If it turns out that the service grade given to mobile station  11   a  is higher than the service grade given to other existing mobile stations  11   b  and  11   c  that are already in service, base station  10  assigns a radio resource to mobile station  11   a  first, given that there are sufficient available resources. Based on the radio resources, base station  10  provides data services to the mobile station  11   a.    
     However, if there are not enough available resources, base station  10  cannot assign proper radio resources, which means that it is not capable of providing a high speed packet data service according to the service grade given to mobile station  11   a . As an alternative, base station  10  suspends the data service being provided to a mobile station having a lower service grade than mobile station  11   a , such as  11   b , among other existing mobile stations  11   b  and  11   c  in service, and provides the data service to mobile station  11   a  instead. 
       FIG. 2  is a flow chart explaining a method for managing a radio resource in a related art. With reference to  FIG. 2 , base station  10  receives a new data call from mobile station  11   a  (S 21 ). Up to this point, mobile station  11   a  has no way to find out how much available resources are secured in a base station to which it has access. 
     If there is a data call from mobile station  11   a , base station  10  confirms the priority of the mobile station and the priority of a data service (S 23 ). Once the priorities of the mobile station and the data service are determined, base station  10  determines a service grade for mobile station  11   a  using the priorities (S 25 ). 
     For example, when a data call from a mobile station is received, the base station first confirms the validity of the mobile station and decides a service priority for the mobile station referring to a database. Usually, the database has all the information about each mobile station. More specifically, information of a subscriber who pays an expensive information fee, information of a subscriber assigned to a particular VIP, information of a subscriber in an emergency situation, and so forth can be stored in the database. In addition, the priority of each different situation is decided in accordance with the standards set by the service providers. 
     If the data service requested by a mobile station belongs to a specific service designated by the service providers (e.g., a service with a high priority) or a requested data transmission rate of a mobile station is high relative to the system usage efficiency, the priority of the corresponding data service may be relatively high. 
     Base station  10  determines the presently available resource (S 27 ) and decides whether the available resource could be assigned to mobile station  11   a  (S 29 ). Here, the available resource means the number of time slots to be assigned to a mobile station in service. 
     If the presently available resource cannot be assigned to mobile station  11   a , base station  10  checks the states of mobile stations  11   b  and  11   c  that are currently in service (S 31 ). When the service grade of mobile station  11   a  turns out to be higher than the service grade of mobile stations  11   b  and  11   c , base station  10  decides whether it is possible to suspend the data service to the mobile stations  11   b  and  11   c  that are in service (S 33 ). 
     Afterwards, base station  10  transmits a suspension message to mobile station  11   b  (S 35 ), given that the data service is suspendible for the station, and accepts the data service requested from mobile station  11   a  (S 37 ). Later, base station  10  undertakes a service opening procedure and provides the data service to the mobile station  11   a  (S 39 ). 
     If the suspension of the data service to mobile stations  11   b  and  11   c  that are in service seems to be impossible at step  33 , base station  10  rejects the data service request from mobile station  11   a  (S 41 ). On the other hand, if the available resource at present can be assigned to mobile station  11   a  in step  29 , base station  10  can carry out the service opening procedure of step  39  directly. 
     In any case, where the presently available resource cannot be assigned to mobile station  11   a  in step  29 , base station  10  either performs the data service at the available data transmission rate, which may be unsatisfactory to the service grade given to the mobile station, or provides the data service to mobile station  11   a  at the proper service grade rate after suspending the data transmissions of mobile stations  11   b  and  11   c  in service at that moment. 
     As described above, the 1xEV-DO mobile communication system generates more traffic volume than the traditional voice service-centered mobile communication system, which unfortunately causes problems like handoff and overload many times. Also, to provide prompt service in response to requests from the mobile station having a high service priority (e.g., high quality of service (QoS)), the 1xEV-DO mobile communication system should reserve more resources than the conventional voice service-centered base station. 
     In short, the base station with the 1xEV-DO system manages the resources to provide the data service requested from the existing mobile station within its cell. Also, the 1xEV-DO system performs the data service through a scheduling process that assigns a radio resource or a band based on the service characteristics of a call requested from the mobile station. Since the resources the base station may assign are limited, the designation of a call and the resource assignment for the quality of service are guaranteed within the limited resources. However, if the resources the base station could assign are not secured, the data service request from the mobile station with a higher service grade, than the data service grade of other mobile stations in service, cannot be met. As a consequence, the data service request from the mobile station with the higher service grade is turned down or the data service provided to the other mobile stations in service should be inevitably suspended to meet the data service request of the mobile station with the higher service grade. 
     Furthermore, some resources might be reserved in a base station by way of solving the above-described problems. But in such case, the entire system could be degraded. 
     The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to solve at least the above problems and/or disadvantages and to provide at least the advantages described hereinafter. 
     It is, therefore, an object of the present invention to provide a method for improving a quality of service and for managing a radio resource of a base station more effectively. 
     To achieve the above objects, the radio resources of a mobile station with a low service grade are collected and assigned to a mobile station with a high service grade. 
     To achieve the above objects, there is provided a method for managing a radio resource in a mobile communication system, including determining a service grade of a mobile station that requests a data service; collecting a radio resource, which is assigned to a mobile station corresponding to a lower service grade among other mobile stations in service, at a constant rate based on a radio resource required for the service grade; and assigning a radio resource to the mobile station using the collected radio resource. 
     The method may further include transmitting a response message for the data service request to the mobile station; providing a data service based on the assigned radio resource corresponding to the service grade assigned to the mobile station; reassigning radio resources of mobile stations in service based on the collected radio resource; reestablishing priorities in accordance with service grades of the mobiles stations in service; and providing data services to the mobile stations in service, in accordance with the reestablished priorities. 
     The collecting step may include confirming an available resource of a base station; deciding whether the available resource of the base station satisfies a radio resource required for the service grade; inquiring about the service grades of mobile stations in service, if the available resource does not satisfy the radio resource required for the service grade; and determining a collection rate of a radio resource, which is assigned to a lowest service grade among other service grades of the mobile stations in service. 
     The collection rate of the radio resource may be determined in accordance with a data transmission rate of a mobile station in service corresponding to a lowest service grade, the data transmission rate of the mobile station that requests the data service, a quality of service of the mobile station that requests the data service, or the quality of service of the mobile station corresponding to the lowest service grade. 
     In addition, the present invention provides a method for providing data services of a mobile communication system, including collecting a radio resource, at a constant rate, assigned to a mobile station corresponding to a lower service grade among other mobile stations in service at present, in case an available resource does not satisfy the request of a mobile station requesting a new data service; assigning a radio resource to the mobile station using the colleted radio resource; and providing the data service to the mobile station based on the assigned radio resource. 
     To achieve the objects in whole or in part, there is provided a method of allocating communication resources including collecting less than all of a first resource that is allocated to a first communication device, which is assigned a lower service priority than a service priority assigned to a second communication device; deallocating the collected first resource from the first communication device; and allocating the collected first resource to the second communication device. 
     To achieve the objects in whole or in part, there is provided a method of allocating a resource among a plurality of subscriber units including determining an amount of the resource required to meet a first prescribed condition; and apportioning the determined amount of the resource among the plurality of subscriber units according to a prioritization scheme, wherein each of the plurality of subscriber units is apportioned some of the resource. 
     Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described in detail with reference to the following drawings in which like reference numerals refer to like elements wherein: 
         FIG. 1  illustrates a block diagram of a mobile communication system in the related art; 
         FIG. 2  illustrates a flow chart explaining a method for managing a radio resource in the related art; and 
         FIG. 3  illustrates a flow chart explaining a method for managing a radio resource in accordance with a preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 3  is a flow chart explaining a method for managing a radio resource in accordance with a preferred embodiment of the present invention. When a base station receives a data service request from a new mobile station rather than the mobile stations in service, which the base station usually provides data services to, the base station determines a service grade for this new mobile station using the priority of the new mobile station and the priority of the data service requested (S 51 ). In other words, in order to confirm the priority of the new mobile station, the base station finds out whether the new base station should be given a specific service or whether the new base station is usually assigned a high quality of service at a high usage fee. The base station also confirms the priority of the data service requested from the new mobile station. Following the confirmation process, the base station determines the service grade of the new mobile station based on the priority of the mobile station and the priority of the service. If the priority of the mobile station and the priority of the service are designated high, the service grade of the new mobile station can be designated high as well. 
     Once the service grade of the new mobile station is determined, the base station confirms the radio resource to be assigned to the service grade of the new mobile station and, simultaneously, confirms the presently available resources. And, the base station decides whether the radio resource of the new mobile station can be satisfied by the presently available resource (S 53 ). More specifically, the base station decides whether the new mobile station requires more radio resource than the presently available resource. If the requested radio resource turns out to be more than the presently available resource, the base station refers to a database to confirm the service grade of a mobile station in service. The database has information about the mobile station in service, the service grade thereof, and the radio resources assigned to the mobile station. After referring to the database, the base station collects the assigned radio resources at a constant rate from a mobile station having a lower grade service (S 55 ). Preferably, the mobile station with the lower grade service corresponds to the lowest service grade. Of course, the radio resource assigned to the mobile station having the lowest service grade might be insufficient to satisfy the radio resource requested by the new mobile station. In such case, the radio resource assigned to the mobile station with the next lowest service grade could be collected as well, if necessary. 
     The constant collection rate mentioned above may be calculated based on the following formula:
 
 R ( t )=1 −[DRC   low     —     QoS ( t )/ DRC   total ( t )]*[ QoS   low     —     Qos ( t )/ QoS   total (   t )]
 
     wherein DRC low     —     QoS (t) is a data transmission rate of the mobile station in service at present that has the lowest service grade, and QoS low     —     QoS (t) indicates the quality of service of the mobile station in service at present that has the lowest service grade. In addition, DRC total (t) is the sum of the data transmission rate of the mobile station in service at present, having the lowest service grade (i.e., DRC low     —     Qos (t)), and the data transmission rate of a mobile station requesting a new data service (i.e., DRC high     —     QoS (t)). Similarly, QoS total (t) is the sum of the quality of service (QoS) belonging to the mobile station in service at present, having the lowest service grade QoS(QoS low     —     QoS (t)), and the QoS of the mobile station requesting a new data service (i.e., (QoS high     —     QoS (t)). Here, DRC high     —     QoS (t) indicates the data transmission rate of the mobile station requesting a new data service, and QoS high     —     QoS (t) indicates the quality of service of the mobile station requesting a new data service. 
     As may be determined from the formula, to obtain a high collection rate, it is necessary to lower DRC low     —     QoS (t) and QoS low     —     Qos (t) relative to DRC total (t) and QoS total (t). Also, as mentioned before, since DRC total (t) and QoS total (t) are the sum of DRC low     —     QoS (t) and DRC high     —     QoS (t) and the sum of QoS low     —     Qos (t) and QoS high     —     QoS (t), respectively, DRC high     —     QoS (t) and QoS high     —     Qos (t) should be increased to obtain a high collection rate. Naturally, if DRC high     —     Qos (t) and QoS high     —     QoS (t) are lowered, a low collection rate is obtained. Accordingly, the four variables, that is, DRC low     —     QoS (t), DRC high     —     QoS (t), QoS low     —     QoS (t), and QoS high     —     Qos (t), are important factors for determining an appropriate collection rate. 
     Determining the collection rate of the radio resource is very advantageous in many ways. First of all, it guarantees stable data service in accordance with the service grades of the mobile stations in service. In addition, relatively more radio resources can be assigned to mobile stations having a good radio environment. As a result, it is possible to manage the available resources of the base station more efficiently and to improve the entire data transmission rate of the base station as well. Here, the radio environment indicates a degree of received power of each mobile station to interference noise, C/I. In short, the resources of the base station can be managed very efficiently by adjusting the collection rate of the radio environment in consideration of the characteristics of the radio environment, such as, whether the characteristics are good or bad. 
     After the radio resource, which has been assigned to the mobile station corresponding to the lowest service grade, is collected at the constant rate, the base station assigns the collected radio resource to the new mobile station (S 57 ). At this point, the base station can send out a response message to the data service request received from the new mobile station. 
     Moreover, as the radio resource that has been assigned to the mobile station with the lowest service grade is collected, the base station reassigns the radio resources of other mobile stations in service according to the service grades thereof and determines the priority of the service grades of the mobile stations in service once again (S 59 ). As for reassigning the radio resources to the mobile stations in service, the data transmission rate of the new mobile station and the maximum data transmission rate within a cell in service can be taken into account. In other words, much more radio resources can be reassigned to a mobile station within the cell that requests the maximum transmission rate despite a low service grade thereof Also, it is always possible to reassign the radio resources to the mobile stations in service based on the priority of each mobile station in service, the data service priority, and so on. 
     The base station, using the radio resource assigned to the new mobile station, can provide the requested data service and continue providing data services to other mobile stations according to the reestablished priorities (S 61 ). 
     On the other hand, if there is more available resource at present than the requested radio resource assigned to the new mobile station in step  53 , the base station proceeds to step  61  and provides the data service to the new mobile station by assigning the radio resource requested. 
     In conclusion, according to the method for managing the radio resource in the mobile communication system of the present invention, the radio resource of a mobile station having a low service grade is collected to be assigned to another mobile station having a high service grade, which improves the quality of service as well as manages the radio resources in the base station more efficiently. 
     In addition, by collecting part of the radio resource of the mobile station having a low service grade, the present invention minimizes the influences of other mobile stations in service. 
     The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention. The present teaching can be readily applied to other types of apparatuses. The description of the present invention is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures.