Abstract:
The present invention relates to a bandwidth allocation apparatus and a method thereof. The present invention provides a method for adaptively allocating and controlling radio channels to multimedia traffic having various characteristics. Particularly, the present invention proposes a method for maximizing a system resource use rate while satisfying a communication QoS requirement for individual video traffic. Therefore, the adaptive bandwidth allocation method according to the present invention guarantees system performance and user-required communication QoS.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims priority to and the benefit of Korean Patent Application Nos. 10-2005-0119982 and 10-2006-0041347 respectively filed in the Korean Intellectual Property Office on Dec. 8, 2005 and May 9, 2006, the entire contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     (a) Field of the Invention  
         [0003]     The present invention relates to a bandwidth allocation apparatus and a method thereof. More particularly, the present invention relates to an apparatus for adaptively allocating radio channels in a mobile communication system, and a method thereof.  
         [0004]     (b) Description of the Related Art  
         [0005]     The next generation mobile communication system will mainly handle multimedia traffic services having various features.  
         [0006]     Thus, the next generation mobile communication system controls a bandwidth for efficient processing of multimedia traffic while satisfying communication quality of service (QoS).  
         [0007]     A significant increase of usable resources for each cell is expected in the next generation mobile communication system compared to the present mobile communication system. For example, each cell is allocated with up to 2 Mbps of bandwidth in the WCDMA system but it will be allocated with up to 100 Mbps of bandwidth in the next-generation mobile communication system. Therefore, a bandwidth allocation determination scheme will be an important factor for an efficient use of radio resources and multimedia traffic processing in the next generation communication system.  
         [0008]     The bandwidth allocation determination scheme will be more complex in the future since various types of traffic will be generated as user traffic is changed from small-capacity voice and data communication to large-capacity multimedia communication.  
         [0009]     Particularly, video traffic is a main concern in the multimedia traffic, and various studies have been conducted to develop an efficient bandwidth allocation scheme thereof.  
         [0010]     One of the most well-known bandwidth allocation schemes is an effective bandwidth scheme. The effective bandwidth scheme produces a value between an average bandwidth and the maximum bandwidth, and the value satisfies a communication quality of service (QoS) traffic requirement (e.g., packet loss rate and delay).  
         [0011]     The concept of the effective bandwidth scheme is quite attractive, but it is difficult to apply to a substantial communication system. Also, it is difficult to determine an effective bandwidth for video traffic in advance.  
         [0012]     Conventionally, communication QoS for voice traffic has been controlled by providing a predetermined communication QoS or controlled by determining priority of services depending on a condition (e.g., a bottleneck) of a system.  
         [0013]     However, multimedia traffic services having various features have distinctive service characteristics, and accordingly they cannot be indiscriminately controlled by the conventional communication QoS scheme.  
         [0014]     The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.  
       SUMMARY OF THE INVENTION  
       [0015]     The present invention has been made in an effort to provide a bandwidth allocation apparatus for periodically filling a token bucket with an amount of tokens that corresponds to the amount of bandwidth determined to be allocated for each traffic flow by the call admission control module and adaptively allocating bandwidths, and a method thereof.  
         [0016]     An exemplary bandwidth allocation method according to an embodiment of the present invention adaptively allocates radio channels in a mobile communication system. The bandwidth allocation method includes: (a) allocating a bandwidth to process traffic services and compare a current queue length and a minimum queue length, the current queue length being measured for a unit of time; (b) when the current queue length is less than the minimum queue length, comparing a packet loss rate and a packet loss threshold value to determine which one is greater than the other one, wherein the packet loss rate determines an amount of bandwidth to be allocated for the next time interval; and (c) when the packet loss rate is less than the packet loss threshold value, reducing the current bandwidth by a large amount.  
         [0017]     An exemplary bandwidth allocation apparatus according to an embodiment of the present invention adaptively allocates radio channels in a mobile communication system. The bandwidth allocation apparatus includes a call admission control module, a packet classification module, a buffer module, a packet scheduler module, and a bandwidth allocation module. The call admission control module requests bandwidth allocation in the case that a call signal of a mobile station is accepted. The packet classification module classifies received packets on the basis of one of an Internet Protocol address, a port, and an upper layer protocol in use, and transmits classified packets. The buffer module receives and stores the classified packets transmitted from the packet classification module. The packet scheduler module receives the classified packet from the buffer module and transmits the packets to the mobile station through a radio resource link. The bandwidth allocation module forms the buffer module for bandwidth allocation and processes traffic services by inter-working with the packet scheduler module in the case that the bandwidth allocation is requested by the call admission control module. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]      FIG. 1  is a block diagram showing a mobile station and a base station of a mobile communication system, and main functionalities of sub-systems of the base station according to an embodiment of the present invention.  
         [0019]      FIG. 2  is a diagram showing a structure of an effective bandwidth allocation according to an exemplary embodiment of the present invention.  
         [0020]      FIG. 3  is a flowchart showing a method for allocating bandwidth by using a bandwidth allocation module according to an exemplary embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0021]     An exemplary embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings.  
         [0022]     In the following detailed description, only certain exemplary embodiments of the present invention have 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. The drawings and description are to be regarded as illustrative in nature and not restrictive, and like reference numerals designate like elements throughout the specification.  
         [0023]     Throughout this specification and the claims which follow, unless explicitly described to the contrary, the word “comprise” or variations such as “comprises” or “comprising” will be understood to imply the inclusion of stated elements but not the exclusion of any other elements.  
         [0024]     In addition, throughout this specification and the claims which follow, a module means a unit that performs a specific function or operation, and can be realized by hardware of software, or a combination of both.  
         [0025]     A bandwidth allocation apparatus for adaptively allocating radio channels and a method thereof in a mobile communication system according to an embodiment of the present invention will now be described.  
         [0026]      FIG. 1  is a block diagram showing a base station and a mobile station of a mobile communication system according to an exemplary embodiment of the present invention, and schematically illustrates main functionalities of each sub-system of the base station.  
         [0027]     Downlink bandwidth allocation between the base station and the mobile station according to the exemplary embodiment of the present invention will now be described.  
         [0028]     Particularly, a radio resource control (RRC) connection is established between the mobile station and the base station to control resource allocation modification.  
         [0029]     Protocol layers may be divided into Layer 1 (i.e., a physical layer), Layer 2 (i.e., a data link layer), and Layer 3 (i.e., a radio resource control layer) according to three lower layers of the open system interconnection (OSI) reference model for worldwide communication systems.  
         [0030]     The radio resource control layer located at the bottom of the Layer 3 is defined only for a control plane, and establishes/re-establishes/releases a radio bearer to control transmission and physical channels.  
         [0031]     When a user turns on the mobile station, the mobile station searches for the most appropriate cell and remains idle in the searched cell.  
         [0032]     The mobile station in the idle mode is shifted to a radio resource control (RRC)-connected state by establishing an RRC connection with the base station. That is, the mobile station in the idle mode must perform a RRC connection establishment process in order to have a RRC connection with the base station.  
         [0033]     The base station according to the exemplary embodiment of the present invention includes a call admission control module  100 , a bandwidth allocation module  110 , a buffer module (i.e., queue)  120 , a packet classification module  130 , and a packet scheduler module  140 .  
         [0034]     The mobile station transmits an RRC connection request message to the base station, the base station transmits an RRC connection establishment message to the mobile station in response to the RRC connection request message, and then the mobile station transmits an RRC connection establishment complete message to the base station such that the RRC connection is established between the mobile station and the base station.  
         [0035]     The RRC of the base station determines whether to accept a call signal or not by operating the call admission control module  100 .  
         [0036]     When the call signal is determined to be accepted, the call admission control module  100  generates a bandwidth allocation request signal for the mobile station and transmits the bandwidth allocation request signal to the bandwidth allocation module  110 .  
         [0037]     Upon arrival of the bandwidth allocation request signal from the call admission control module  100 , the bandwidth allocation module  110  forms a buffer module  120  for bandwidth allocation.  
         [0038]     The buffer module  120  receives and stores packets that are determined by the packet classification module  130 , and transmits packets to the packet scheduler module  140  in proportion to the amount of tokens in the token bucket.  
         [0039]     The packet classification module  130  classifies downlink packets on the basis of an Internet Protocol (IP) address, a port, and a usable upper layer protocol, and transmits the classified packets to the corresponding queues  120 , accordingly.  
         [0040]     The packet scheduler module  140  receives the determined packets from the buffer module  120  and transmits the packets to the mobile station through a wireless radio link.  
         [0041]      FIG. 2  is a diagram showing a structure of an effective bandwidth allocation according to an exemplary embodiment of the present invention.  
         [0042]     The bandwidth allocation module  110  of the base station allocates the corresponding token bucket and the corresponding queue  120  to each cell for respective user video traffic flows.  
         [0043]     The bandwidth allocation module  110  periodically fills each token bucket with an amount of tokens that corresponds to an initially allocated bandwidth by the call admission module  100 . The bandwidth allocation module  110  controls the amount of tokens filled in the token so as to control a bandwidth allocated for each video traffic flow.  
         [0044]     The bandwidth allocation module  110  provides many tokens for heavy traffic for accurate transmission of information, and provides few tokens for light traffic in order to provide the rest of the tokens for other traffic services. The bandwidth allocation module  110  determines bandwidth allocation for each traffic flow by employing a token bucket algorithm, and sets a sum of allocated bandwidths to not exceed a maximum supportable resource bandwidth for the cell.  
         [0045]     The bandwidth allocation module  110  may guarantee a minimum throughput for each video traffic flow by using the token bucket algorithm. The bandwidth allocation module  110  allocates a bandwidth for each video traffic flow for each predetermined time interval.  
         [0046]     The bandwidth allocation module  110  according to the exemplary embodiment of the present invention allocates a minimum bandwidth that satisfies demanded quality of communication service, and maximizes utility of the allocated bandwidth.  
         [0047]     In the case that the utility of the bandwidth is relatively low, the bandwidth allocation module  110  reduces bandwidth allocation. Otherwise, the bandwidth allocation module  110  increases bandwidth allocation. The bandwidth allocation module  110  reduces/increases the bandwidth allocation in accordance with measured communication QoS.  
         [0048]     In the case that the probability of communication QoS requirement violation is relatively high, the bandwidth allocation module  110  increases a bandwidth increase rate and decreases a bandwidth decrease rate. In the case that the probability of communication QoS requirement violation is relatively low, the bandwidth allocation module  110  increases the bandwidth decrease rate and increases the bandwidth decrease rate. Herein, the utility value of a current bandwidth is an important factor to determine whether to increase or decrease bandwidth allocation for the next time interval. In addition, satisfaction on the present communication QoS affects the bandwidth change rate. The above-stated process is repeated every time unit.  
         [0049]      FIG. 3  is a flowchart showing a method for maximizing use of system resources while satisfying communication QoS of video traffic of each user. The method uses an adaptive bandwidth allocation algorithm that employs a token bucket.  
         [0050]     Herein, the word “adaptive” implies that bandwidth allocation is determined in real-time and is dynamically and continuously changed in accordance with circumstances.  
         [0051]     In addition, a packet loss rate is used to level communication QoS, and a video traffic flow for each user has a maximum allowable packet loss rate.  
         [0052]     Hereinafter, a bandwidth allocation algorithm performed by the bandwidth allocation module  110  will be described with reference to  FIG. 3 .  
         [0053]      FIG. 3  is a flowchart showing a method for allocating a bandwidth by using the bandwidth allocation module  110  according to the exemplary embodiment of the present invention.  
         [0054]     The bandwidth allocation module  110  according to the exemplary embodiment of the present invention allocates a bandwidth at every time unit for each traffic flow, and allocates a minimum bandwidth that satisfies communication QoS requirement while maximizing utility of the bandwidth.  
         [0055]     In the present embodiment, a queue length and a packet loss rate are used as matrixes for determining bandwidth utility and communication QoS requirement.  
         [0056]     The bandwidth allocation module  110  compares a queue length QL(t) to a minimum queue length QL low  and a maximum queue QL high  to determine whether an excessive amount of bandwidth is allocated or an insufficient amount of bandwidth is allocated.  
         [0057]     Herein, the queue length QL(t) represents a queue length measured for a unit of time t.  
         [0058]     In the case that the queue length QL(t) is less than the minimum queue length QL low , the bandwidth allocation module  110  regards the corresponding signal to waste the bandwidth, and reduces an allocated bandwidth.  
         [0059]     In the case that the queue length QL(t) is greater than QL high , the bandwidth allocation module  110  regards the corresponding signal to over-utilize the bandwidth, and increases the allocated bandwidth.  
         [0060]     In the case that the queue length QL(t) has a middle value of the minimum queue length Q low  and the maximum queue QL high , the bandwidth allocation module  110  does not change the allocated bandwidth.  
         [0061]     The bandwidth allocation module  110  allocates a bandwidth at every unit of time for each traffic flow in step S 100 , and determines whether a current queue length is less than the minimum queue length in step S 102 .  
         [0062]     When the current queue length is less than the minimum queue length, the bandwidth allocation module  110  determines whether the current queue length is less than the minimum queue length during two consecutive time intervals in step S 104 .  
         [0063]     In the case that the current queue length is less than the minimum queue length during the two consecutive time units, the bandwidth allocation module  110  measures a packet loss rate (i.e., packet loss rate due to transmission error in the network) by sampling a packet loss through a ping.  
         [0064]     The packet loss rate is used as a parameter for determination of an amount of bandwidth to be allocated to the next time interval.  
         [0065]     Subsequently, the bandwidth allocation module  110  determines whether the packet loss rate is less than a packet loss threshold value PL threshold  in step S 106 .  
         [0066]     When the packet loss rate is less than the packet loss threshold value, the bandwidth allocation module  110  reduces the current bandwidth by a relatively small amount in order to avoid packet loss in the next unit of time in step S 108 .  
         [0067]     In the case that the packet loss rate is less than the packet threshold value, the bandwidth allocation module  110  reduces the current bandwidth by a relatively large amount in order to avoid packet loss in the next unit of time, in step S 110 .  
         [0068]     When the current queue length is greater than the minimum queue length, the bandwidth allocation module  110  determines whether the current queue length is greater than the maximum queue length in step S 112 .  
         [0069]     In the case that the current queue length is greater than the maximum queue length, the bandwidth allocation module  110  determines whether the packet loss rate is less than the packet loss threshold value PL threshold  in step S 114 .  
         [0070]     When the packet loss rate is greater than the packet loss threshold value, the packet bandwidth allocation module  110  increases the current bandwidth by a relatively large amount since the bandwidth in the time interval may allow packet loss, in step S 116 .  
         [0071]     When the packet loss rate is less than the packet loss threshold value, the bandwidth allocation module  110  reduces the current bandwidth by a relatively small amount since the bandwidth in the next time interval may allow packet loss, in step S 118 .  
         [0072]     The bandwidth allocation module  110  calculates a bandwidth to be allocated by using Equation 1.  
               EB   ⁡     (     t   +   1     )       =     {               EB   ⁡     (   t   )       /   DF     ,           for   ⁢           ⁢   bandwidth   ⁢           ⁢   decrease                   EB   ⁡     (   t   )       ×   IF     ,           for   ⁢           ⁢   bandwidth   ⁢           ⁢   Increase                     [     Equation   ⁢           ⁢   1     ]             
 
         [0073]     where EB(t) denotes the current bandwidth, DecreaseFactor (DF) and IncreaseFactor (IF) denote re-allocation parameters, EB(t+1) denotes a bandwidth to be allocated for the next unit of time, DF small  denotes a small amount of reduction in bandwidth re-allocation, DF large  denotes a large amount of reduction in bandwidth re-allocation, IF small  denotes a small amount of increase in bandwidth re-allocation, and IF large  denotes a large amount of increase in bandwidth re-allocation.  
         [0074]     The above-described exemplary embodiments of the present invention can be realized not only through a method and an apparatus, but also through a program that can perform functions corresponding to configurations of the exemplary embodiments of the present invention or a recording medium storing the program, and this can be easily realized by a person skilled in the art.  
         [0075]     According to the above-stated configuration, the exemplary embodiment of the present invention provides a method for adaptive bandwidth allocation and control to thereby guarantee system performance and user&#39;s demanded communication QoS requirements.  
         [0076]     In addition, the maximum system resource use rate is guaranteed while satisfying communication QoS of video traffic for each user according to the exemplary embodiment of the present invention.  
         [0077]     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 embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.