Abstract:
A scheduling apparatus and method are capable of maximizing efficiency of trunk line usage and preventing queue congestion when a trunk line is used in a mobile communication system. A variable bandwidth management service for allocating more bandwidth to a queue with greater traffic is provided so that allocation of bandwidth can be made flexibly. A scheduler calculates actually provided class information and performs scheduling according to a current scheduling ratio, thereby preventing congestion of a specific queue.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     Pursuant to 35 U.S.C. § 119(a), this application claims the benefit of earlier filing date and right of priority to Korean Application No. 70091/2004 filed Sep. 2, 2004, the contents of which are hereby incorporated by reference herein in its entirety.  
       FIELD OF THE INVENTION  
       [0002]     The present invention relates to a mobile communication system and, more particularly, to an apparatus and method for controlling scheduling capable of maximizing efficiency of trunk line usage and preventing congestion at a queue for using various multimedia services in the mobile communication system.  
       BACKGROUND OF THE INVENTION  
       [0003]     In line with development of mobile communication techniques and generalization of mobile communication terminals, a mobile communication system is not limited to providing a simple voice call communication service but extends to providing various multimedia data services such as music, video or television or radio broadcast.  
         [0004]     Accordingly, the mobile communication techniques focus on how much data can be transmitted quickly and effectively. When a new or enhanced service is provided, efficiency of data transmission becomes important because the new or enhanced service is operated on the existing mobile communication system.  
         [0005]     Currently, in a recent mobile communication system in which both a data and a voice are simultaneously provided, a method for maximizing usage efficiency of a trunk line such as E1 link or T1 link has been studied.  
         [0006]     In a related art, the scheduling of the processing for a trunk line, transmission of traffic is allocated a fixed bandwidth according to a fixed scheduling ratio. Thus, while bandwidth is allocated according to a scheduling ratio received first from a control plane between voice and data, if the service type of subscribers is subsequently changed so that the ratio between the actually transmitted voice and the data is changed, the efficiency of the trunk line is degraded and queue congestion occurs.  
         [0007]     The control plane is used as a resource management concept in a radio interface of the mobile communication system, and configuration of a protocol can be divided into the control plane and a traffic plane. The control plane relates to the control signals while the traffic (data) plane relates to the data or voice traffic. Thus, in order to transmit actual traffic, the control plane is required, and the discrimination of the planes effectively manages the various type of traffic.  
         [0008]     For example, if the amount of the voice traffic is increased while the amount of the data traffic is decreased compared with the fixed scheduling ratio, voice queue becomes congested. Because the scheduler allocated much of the bandwidth to data traffic, significant bandwidth is wasted, resulting in degradation of efficiency of the trunk line usage. Also, in order to receive a relocated scheduling ratio from the control plane, the scheduler operating at the fixed scheduling ratio must be initialized.  
       SUMMARY OF THE INVENTION  
       [0009]     Therefore, one object of the present invention is to provide an apparatus and method for controlling scheduling in a mobile communication system capable of maximizing efficiency of trunk line usage.  
         [0010]     Another object of the present invention is to provide an apparatus and method for controlling scheduling in a mobile communication system capable of preventing queue congestion.  
         [0011]     To achieve at least the above objects in whole or in parts, an apparatus is provided for controlling scheduling in a mobile communication system, including: a classifying unit for receiving traffic with various class types to be transmitted through a trunk line and classifying the received classes; a forwarding unit for receiving the classified traffic data together with class information and writing traffic in a corresponding voice or data queue by using the received class information; a buffering unit for storing information transferred from the forwarding unit; a scheduler for allocating a band within a trunk line bandwidth range of each voice or data queue, performs scheduling, reading traffic from each voice and data queue, and placing the voice and data traffic on the trunk line; and a changing unit for calculating a bandwidth of each class actually scheduled by the scheduler for a certain time to determine a suitable scheduling ratio, and varying the scheduling ratio.  
         [0012]     Preferably, the scheduling unit regards the voice and data queues in a buffering unit as one virtual integrated queue and manages both queues with a variable bandwidth for a flexible allocation.  
         [0013]     Preferably, the changing unit stores the class type actually scheduled by the scheduling unit in a storage unit during a certain time, calculating a scheduling ratio of each class by analyzing the class type, and changing a current scheduling ratio to a calculated scheduling ratio.  
         [0014]     To achieve at least these advantages in whole or in parts, there is further provided a method for controlling scheduling in a mobile communication system, including: classifying introduced traffic of various class types; transmitting traffic together with class information; storing traffic in a corresponding voice or data queue; monitoring the voice and data queues; sensing a non-empty state of the voice or data queue and determining whether the voice or data queue is actually in the non-empty state; and performing variable scheduling by allocating a corresponding bandwidth to the non-empty queue.  
         [0015]     Preferably, the method for controlling scheduling in the mobile communication further includes performing scheduling according to a scheduling ratio received from a control plane during initialization if the voice or data queue is actually in the non-empty state.  
         [0016]     To achieve at least these advantages in whole or in parts, there is further provided a mobile communication system including: a mobile station (MS) allowing a subscriber to communicate by using a mobile communication network in a service area; a base station transceiver subsystem (BTS) connected with the MS by a radio interface, controlling the MS and connecting a traffic channel; a base station controller (BSC) having a scheduling controller which is provided at an end thereof, manages introduced traffic with a variable bandwidth and schedules the traffic according to an actual traffic transmission situation, transmitting traffic to the BTS through a trunk line such as an E1 link or a T1 link according to a scheduling result, and handling controlling and management of the BTS; a mobile switching center (MSC) performing functions such as circuit switching, incoming/outgoing processing, handoff, roaming, or the like in order to provide a mobile communication service to a mobile communication subscriber; and a base station manager (BSM) for operating/managing and maintenance of the entire BTS, and performing loading for initialization.  
         [0017]     Preferably, when the BSC receives voice or data traffic introduced from an MS of a different area or a network and transmits it to the MS through the BTS, the BSC includes the traffic in the trunk line according to a scheduling ratio determined by the scheduling controller. The scheduling ratio is received from a control plane during initialization, and the ratio may be changed later by the scheduling controller according to a ratio between the actual voice and data traffic.  
         [0018]     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  
       [0019]     The invention will be described in detail with reference to the following drawings in which like reference numerals refer to like elements wherein:  
         [0020]      FIG. 1  illustrates the construction of a mobile communication system having a scheduling controller in accordance with the present invention;  
         [0021]      FIG. 2  illustrates the construction of the scheduling controller of a trunk line in the mobile communication system in accordance with the present invention;  
         [0022]      FIG. 3  is a flow chart of a method for controlling scheduling of the trunk line in the mobile communication system in accordance with one embodiment of the present invention; and  
         [0023]      FIG. 4  is a flow chart of a method for controlling scheduling of the trunk line in the mobile communication system in accordance with another embodiment of the present invention 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0024]     The embodiments of the present invention will now be described with reference to the accompanying drawings. In describing the present invention, if a detailed explanation for a related known function or construction is considered to unnecessarily divert the intent of the present invention, such explanation has been omitted but would be understood by those skilled in the art.  
         [0025]      FIG. 1  illustrates the construction of a mobile communication system having a scheduling controller in accordance with the present invention, wherein the mobile communication system  100  having the scheduling controller includes a mobile station (MS)  110  allowing a subscriber to communicate by using a mobile communication network in a service area; a base station transceiver subsystem (BTS)  120  connected with the MS  110  by a radio interface, controlling the MS  110  and connecting to a traffic channel; a base station controller (BSC)  140  having a scheduling controller for scheduling introduced traffic for and transmitting traffic according to a scheduling ratio to the BTS  120  through a trunk line  130  such as an E1 link or a T1 link, and controlling and managing the BTS  120 ; a mobile switching center (MSC)  150  performing functions such as circuit switching, incoming/outgoing processing, handoff, roaming, or the like in order to provide a mobile communication service to a mobile communication subscriber; and a base station manager (BSM)  160  for operating/managing and maintaining/repairing the BTS  120 , and performing loading for initialization.  
         [0026]     When the BSC  140  receives voice or data traffic introduced from a mobile station located in a different area or network, and transmits the traffic to the MS  110  through the BTS  120 , The BSC  140  includes the traffic in the trunk line  130  according to a scheduling ratio determined by the scheduling controller  200 . The scheduling ratio is received first from a control plane and can be changed later by the scheduling controller according to a ratio between a voice and data traffic actually received.  
         [0027]      FIG. 2  illustrates the construction of the scheduling controller of a trunk line in the mobile communication system in accordance with the present invention, wherein the scheduling controller  200  of the trunk line includes a classifying unit  210  for classifying a class of introduced traffic; a forwarding unit  220  for writing class information in a corresponding voice or data queue; a buffering unit  230  for storing information transferred from the forwarding unit  220 ; a scheduling unit  240  for performing scheduling to allocate a bandwidth to the voice or data queue according to a scheduling ratio received from the control plane during initialization, and reading traffic from the voice and data queues and including it in the trunk line; and a changing unit  250  for storing a class type scheduled by the scheduling unit  240  for a certain time, determining a suitable scheduling ratio, and varying the current scheduling ratio.  
         [0028]     The classifying unit  210  receives traffic having various class types to be transmitted to the trunk line and classifies the traffic according to whether the traffic is voice or data. The classifying unit  210  provides traffic and corresponding class information to the forwarding unit  220 .  
         [0029]     The forwarding unit  220  determines whether to write the corresponding traffic in a voice queue or in a data queue responsive to the class information provided from the classifying unit  210 , and writes the traffic in a corresponding queue.  
         [0030]     The buffering unit  230  includes a plurality of integrated queues,  230 - 1  to  230 -N, each integrated queue comprising a voice queue and a data queue, for storing the traffic forwarded from the forwarding unit  220  according to whether the traffic is voice or data. The voice and data queues are regarded as one virtual integrated queue and managed by the scheduling unit  240 . Accordingly, the N number of queues of Q 1 ˜QN  230 - 1  to  230 -N are managed as the N/2 number of virtual integrated queues. Information forwarded from the forwarding unit  220  is classified as voice traffic or data traffic and stored in a corresponding queue.  
         [0031]     The scheduling unit  240  regards the voice and data queues of the buffering unit  230  as one virtual integrated queue with a variable bandwidth according to the scheduling ratio received from the control plane during initialization. Though not shown, schedulers corresponding to the number of integrated queues are provided in the scheduling unit  240  and the schedulers monitor the integrated queues in real time. When the integrated queue informs the scheduler that one of the two queues is not in an empty state with stored traffic, the scheduler checks whether the other queue is actually not in the empty state, and if the non-empty state is confirmed, the scheduler performs scheduling according to the scheduling ratio. Meanwhile, if the other queue is in an empty state, the scheduler determines that a non-empty state of the other remaining queue makes the virtual integrated queue non-empty state and allocates corresponding bandwidth to the other remaining queue. In addition, the scheduler reads traffic from each voice and data queue and includes the traffic in the trunk line.  
         [0032]     The changing unit  250  stores the actually scheduled class type in the storage unit for a certain time, analyzes it to calculate a scheduling ratio of each class, and changes the current scheduling ratio of the scheduling unit  240  to the calculated scheduling ratio. In this case, the calculated scheduling ratio can be directly applied to the scheduling unit  240  or information on whether to change the scheduling ratio is provided to an upper operator such as the BSM  160 .  
         [0033]      FIG. 3  is a flow chart of a method for controlling scheduling of the trunk line in the mobile communication system in accordance with one embodiment of the present invention.  
         [0034]     With reference to  FIG. 3 , the classifying unit  210  generates class information by discriminating whether introduced traffic is a voice signal or a data signal, and transmits the generated class information together with traffic to the forwarding unit  220  (step S 310 ). Upon receiving the class information from the classifying unit  210 , the forwarding unit  220  determines whether to write the corresponding traffic in the voice queue or in the data queue by referencing the generated class information, writes the traffic into the voice or data queue, and transmits the traffic (step S 320 ). Upon receiving the traffic from the forwarding unit  220 , the buffering unit  230  stores the received traffic in a voice or data queue (step S 330 ). The scheduling unit  240  regards the voice and data queues as one virtual integrated queue and monitors the virtual integrated queue (step S 340 ). When one of the integrated queue is sensed to be in non-empty state during monitoring (step S 350 ), the scheduling unit  240  determines whether the other queue is actually in the empty state or not (step S 360 ). If the other queue is not in the empty state, the scheduling unit  240  performs scheduling according to the scheduling ratio initially received from the control plane (step S 370 ). However, if the other queue is in an empty state, the scheduling unit  240  performs variable scheduling for allocating a corresponding bandwidth to the non-empty queue (step S 380 ).  
         [0035]      FIG. 4  is a flow chart of a method for controlling scheduling of the trunk line in the mobile communication system in accordance with another embodiment of the present invention.  
         [0036]     As shown in  FIG. 4 , the classifying unit  210  discriminates whether introduced traffic is a voice signal or a data signal, generates class information, and transmits the generated class information together with traffic to the forwarding unit  220  (step S 410 ). Upon receiving the class information from the classifying unit  210 , the forwarding unit  220  determines whether to write the corresponding traffic in the voice queue or in the data queue with reference to the received class information, writes it in the voice or data queue, and forward the traffic (step S 420 ). Upon receiving the traffic from the forwarding unit  220 , the buffering unit  230  stores the received traffic in a voice or data queue (step S 430 ). The scheduling unit  240  performs scheduling according to the scheduling ratio initially received from the control plane (step S 440 ). The changing unit stores the class type actually scheduled by the scheduler in the storage unit for a certain time, analyzing it to calculate a scheduling ratio of each class (step S 450 ), and changes the current scheduling ratio of the scheduler to the calculated scheduling ratio (step S 460 ). In this case, the calculated scheduling ratio can be directly applied to the scheduler, or information on whether to change the calculated scheduling ratio is provided to an operator such as the BSM, so that the operator can change the scheduling ratio of the scheduler.  
         [0037]     As so far described, the apparatus and method for controlling scheduling in the mobile communication system have many advantages. For example, bandwidth may be flexibly allocated between voice and data traffic when one of the data or voice queues is in a non-empty state. Instead of using a fixed bandwidth allocation ratio, the bandwidth ratio allocated to voice and data traffic may be varied according to the traffic. If trunk line occupancy rate is high due to traffic, there is a possibility of congestion in each queue, therefore the scheduler calculates actual class information to determine an optimum scheduling ratio, thereby preventing congestion of the corresponding queue.  
         [0038]     As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalence of such metes and bounds are therefore intended to be embraced by the appended claims.