Abstract:
A channel allocation method for radio data calls having different bandwidths to each other in a radio data call processing structure between a mobile switching system and an IWF is disclosed. The method includes receiving a data call connection request; allocating an available time slot and an E 1  link; judging a requested bandwidth on the basis of a service option of a received data call; defining a weight value of each data call by using a rate of the requested bandwidth; and dynamically allocating an H 0  channel on an E 1  link on the basis of the number of data calls occupied at each H 0  channel and the weight value of each data call.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a mobile communication system, and more particularly, to a channel allocation method for radio data calls having different bandwidths to each other.  
           [0003]    2. Background of the Related Art  
           [0004]    In a mobile communication network, a call connection of a mobile subscriber is typically performed by a call processing unit of a mobile switching system. The call processing unit discriminates and processes a voice call and a data call according to a service option of a call. The traffic of the voice call is transmitted in a 64 Kbps PCM (Pulse Code Modulation) method, while the traffic of the data call is converted to a frame relay mode, and processed by being interworked with an Interworking Function (IWF) of a data network.  
           [0005]    [0005]FIG. 1 illustrates a call processing structure between the mobile switching system  10  and the IWF  20 . When a call set-up request is inputted from a mobile subscriber, a call processing unit  11  determines whether it is a voice call or a data call according to a service option of that call. If the call is determined to be a voice call, the call processing unit  11  transmits the voice call to its destination through a relay line processing unit  14  to a PSTN (Public Switched Telephone Network) network. If, however, the call is a data call, the call processing unit  11  outputs the service option of the corresponding call and its related parameters to a frame relay converting unit  12 , and requests that the frame relay converting unit  12  connect a traffic path to the IWF  20 .  
           [0006]    Upon receipt of the request for a traffic path connection from the call processing unit  11 , the frame relay converting unit  12  converts the traffic of the 64 Kbps data call, that is, the traffic transmitted in the PCM method, to a frame relay mode. The frame relay connecting unit  12  then transmits the traffic to the IWF  20 . The traffic of each data call thusly converted to the frame relay is sequentially multiplexed to an H 0  channel of an E 1  link and transmitted to the IWF  20 .  
           [0007]    The IWF  20  then determines whether the data call outputted from the frame relay converting unit  12  is transmitted in a circuit switching system or in a packet switching system. If the data call is to be transmitted in the circuit switching system, it is transmitted in an ISDN PRI (Primary Rate Interface) method through the PSTN path processing unit  13  of the mobile switching system  10  to the PSTN network. If, however, the data call is to be transmitted in the packet switching system, it is directly transmitted to a PSDN (Public Switched Data Network).  
           [0008]    [0008]FIG. 2 is a diagram showing a construction of a related art frame relay converting unit of FIG. 1. The frame relay converting unit  12  includes a plurality of selves (self 1 ˜selfn). 15 control boards, each having 8 time slots, and two control boards, each having 5 H 0  channels, are mounted per single self. That is, each self includes total 120 time slots (64 Kbps) and two E 1  links each having five H 0  channels (384 Kbps).  
           [0009]    Referring to FIG. 3, the operation of the related art method of channel allocation will be described. First, a data call connection request is received from the call processing unit  11  (Step S 31 ). The frame relay converting unit  12  then allocates an available time slot (Step S 32 ). At this time, since each self (self 0 ˜selfn) includes total 120 time slots (64 Kbps), 120 data calls can be accommodated altogether.  
           [0010]    When a time slot is allocated, the frame relay converting unit  12  allocates the H 0  channel on the E 1  link corresponding to the time slot, and assigns DLC (Data Link Connection Identifier) values sequentially or in a round-robin method, thereby allocating a plurality of data calls to the H 0  channel (Step S 33 ).  
           [0011]    Accordingly, when only an IS (Interim Standard)-95A based data call is supported, the data call has a maximum single bandwidth of 13 Kbps due to the bandwidth limitation of a wireless interval. Thus, in order to guarantee a quality of data service, a maximum of 30 data calls can be allocated to a single H 0  channel. Each data call is discriminated by DLCI values (DLCI 0 ˜DLCI 119 ) in the same channel.  
           [0012]    As the H 0  channel and the DLCI value are assigned on the E 1  link, the frame relay converting unit  12  stores channel state information (Step S 34 ), and converts the traffic transmitted from the allocated time slot to a frame relay and transmits it through the E 1  channel to the IWF  20  (Steps S 35 , S 36 ).  
           [0013]    FIGS.  4  show a sequential channel allocation for data calls having a single bandwidth to each other in accordance with the related art.  
           [0014]    The method of sequential channel allocation according to the related art has various problems. For example, as described above, for the purpose of interworking with the IWF, the channel allocation on the E 1  link is performed whenever a call is requested. For radio data calls according to IS-95A having a single bandwidth (13 Kbps) as shown in FIG. 4, since the number of occupied DLCs, that is, the number of data calls, signifies an occupied bandwidth, no problem arises with respect to channel allocation.  
           [0015]    However, in the related art sequential channel allocation as shown in FIG. 4, when a new data call is requested after a third H 0  channel is allocated, even though there is a H 0  channel which does not go beyond the service quality guarantee limitation, a fourth H 0  channel is allocated. Thus, channel congestion occurs and the call is delayed. This phenomenon becomes more serious where a middle-speed service and an high-speed service, such as the IS-95B and the IS-95C, having different bandwidths (64 Kbps, 128 Kbps) are supported together.  
           [0016]    Accordingly, the related art sequential channel allocating method, which considers only the number of data calls without counting the bandwidth, causes a traffic delay due to traffic congestion. This results in a waste of the channel resource and a deterioration of capacity to accommodate subscribers.  
           [0017]    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  
         [0018]    It is an object of the present invention to provide a channel allocation method for radio data calls that substantially obviates disadvantages and problems due to limitations of the related art.  
           [0019]    It is another object of the present invention to provide a channel allocation method for radio data calls that is capable of variably allocating a channel for data calls having different bandwidth each other.  
           [0020]    Another object of the present invention is to provide a channel allocation method for radio data calls that is capable of preventing a traffic delay and effectively utilizing a channel resource by allocating an H 0  channel according to a bandwidth required by each data call.  
           [0021]    To achieve at least the above objects in whole or in parts, there is provided a channel allocation method for radio data calls between a mobile switching system and an IWF wherein traffic attributions of each data call are discriminated based on a service option value of a mobile subscriber call and data calls having different bandwidth to each other are dynamically allocated to an H 0  channel of an E 1  link.  
           [0022]    To further achieve at least the above objects in whole or in parts, there is also provided a channel allocation method for radio data calls having different bandwidths to each other in a radio data call processing structure between a mobile switching system and an IWF, including the steps of: receiving a data call connection request; allocating an available time slot and an E 1  link; judging a requested bandwidth on the basis of a service option of a received data call; defining a weight value of each data call by using the rate of the requested bandwidth; and dynamically allocating an H 0  channel on an E 1  link on the basis of the number of data calls occupied at each H 0  channel and the weight value of each data call.  
           [0023]    According to the channel allocation method for radio data calls, the step of allocating the H 0  channel preferably includes sub-steps of comparing whether the requested bandwidth is greater than a reference bandwidth; operating the number of the data calls and the weight value of each data call, to compute a bandwidth occupied by a data call currently being in a connected state; subtracting the occupied bandwidth from the maximum allowable bandwidth by H 0  channels, to check whether there is any available bandwidth in each H 0  channel; and variably allocating an H 0  channel according to existence of the available bandwidth.  
           [0024]    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  
       [0025]    The invention will be described in detail with reference to the following drawings in which like reference numerals refer to like elements wherein:  
         [0026]    [0026]FIG. 1 is a drawing illustrating a related art call processing structure between a mobile switching system and an IWF;  
         [0027]    [0027]FIG. 2 is a drawing illustrating construction of a frame relay converting unit of FIG. 1;  
         [0028]    [0028]FIG. 3 is a flow chart of a related art channel allocation method for a radio data call having a single bandwidth;  
         [0029]    [0029]FIG. 4 is a drawing illustrating a related art sequential channel allocation for data calls having a single bandwidth;  
         [0030]    [0030]FIG. 5 is a flow chart showing a channel allocation method for radio data calls having different bandwidth to each other, in accordance with a preferred embodiment of the present invention; and  
         [0031]    [0031]FIG. 6 is a drawing illustrating a dynamic channel allocation for data calls having different bandwidths to each other in accordance with the preferred embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0032]    The data call processing structure of the present invention is similar to that of the related art, as shown in FIG. 1. The mobile switching system  10  preferably determines a traffic attribute of a data call, and discriminates between a voice call and a data call according to a service option value of a call. Additionally, however, the data call processing structure supports data calls having different bandwidths than each other.  
         [0033]    That is, when the mobile switching system  10  is interworking with the IWF  20 , it determines an attribute of each data call, and variably allocates the H 0  channel of the El link according to a bandwidth required by each data call.  
         [0034]    The channel allocation method for radio data calls in the call processing structure of the present invention will now be described. When a call set-up request is inputted, the call processing unit  11  determines whether the corresponding call is a voice call or a data call according to the service option.  
         [0035]    If the call is a voice call, the call processing unit  11  transmits it through the relay line processing unit  14  to the PSTN network. If the call is a data call, however, the call processing unit  11  outputs a service option and its related parameters to the frame relay converting unit  12 , to request connection of a traffic path to the IWF  20 .  
         [0036]    Upon receiving the data call connection request from the call processing unit  11  (Step S 41 ), the frame relay converting unit  12  allocates an available time slot for the requested data call, and determines a required/requested bandwidth based on the service option of the corresponding data call (Steps S 42 , S 43 ).  
         [0037]    At this time, the requested bandwidth is divided into 13 Kbps, 64 Kbps, and 128 Kbps depending on the service option, and weighted values of each requested bandwidth are allocated and managed according to the rate of the bandwidth.  
         [0038]    Accordingly, a requested bandwidth of the IS-95A (13 Kbps)-based low speed data call is defined to be 1 unit, a requested bandwidth of the IS-95B (64 Kbps)-based middle speed data call is defined to be 5 units, and a requested bandwidth of the IS-95C (128 Kbps)-based high speed data call is defined to be 10 units.  
         [0039]    For purposes of example, a case where the two bandwidths of the IS-95A and the IS95B are supported together is described hereinafter. It should be understood that any configuration could be used.  
         [0040]    When a bandwidth of a data call is determined, the frame relay converting unit  12  analyzes the bandwidth and determines whether the requested bandwidth is greater than a reference bandwidth. For purposes of example, the reference bandwidth is 2 units (Step S 44 ). If the requested bandwidth (1 unit) is smaller than the reference bandwidth (2 units), the frame relay converting unit  12  computes a bandwidth occupied by a data call currently in a connected state for each H 0  channel (Step S 45 ). In this respect, the bandwidths being used in each channel can be obtained by adding weight values as much as the currently allocated DLCIs.  
         [0041]    Upon computing the occupied bandwidth, the frame relay converting unit  12  determines whether there is an H 0  channel having an available bandwidth (Step S 46 ). Generally, the H 0  channel allows 384 Kbps bandwidth, so that a single H 0  channel is able to provide a call connection service for at least 30 units without a traffic delay. Thus, the frame relay converting unit  12  subtracts an occupied bandwidth (currently occupied weigh (unit)) from the maximum allowable bandwidth (30 units) by H 0  channels, to compute an available bandwidth.  
         [0042]    If no H 0  channel has an available bandwidth, the frame relay converting unit  12  allocates an H 0  channel having the least occupied bandwidth for traffic processing of the corresponding data call. This is done to reduce a traffic delay of the corresponding data call at the maximum.  
         [0043]    Meanwhile, if there is an H 0  channel having an available bandwidth, the frame relay converting unit  12  allocates an H 0  channel having the least available bandwidth. Thus, as the H 0  channel having the least available bandwidth is allocated for traffic of the corresponding data call if a data call, having a requested bandwidth that is larger than the reference bandwidth is requested to be connected later, the traffic of the corresponding data call can be processed more effectively.  
         [0044]    For example, if a first H 0  channel having an available bandwidth of 2 units and a second H 0  channel having an available bandwidth of 5 units are both available, a data call which requests a bandwidth of 1 unit is allocated to the first H 0  channel, while a data call which requests a bandwidth of 5 units is allocated to the second channel. In this way, traffic of the next requested data call can be effectively processed.  
         [0045]    Meanwhile, in Step S 44 , if the requested bandwidth (for example, 5 units) is greater than the reference bandwidth (2 units), the frame relay converting unit  12  computes the occupied bandwidth in the same manner (Step S 52 ) and subtracts the occupied bandwidth from the maximum 30 units, to thereby check whether there is an H 0  channel having an available bandwidth (Step S 53 ).  
         [0046]    Upon checking, if no H 0  channel having an available bandwidth exists, the frame relay converting unit  12  allocates an H 0  channel having the least occupied bandwidth for traffic processing. If, on the other hand, an H 0  channel having an available bandwidth exists, the frame relay converting unit  12  allocates an H 0  channel having the largest available bandwidth.  
         [0047]    In other words, as shown in FIG. 6, in the preferred embodiment, a data call having a smaller bandwidth is allocated to a first H 0  channel, while a data call having a larger bandwidth is allocated to a third H 0  channel, so that an even bandwidth distribution can be made, and thus, the uneven channel congestion as shown in FIG. 4 can be prevented.  
         [0048]    Next, as the H 0  channel is allocated on the E 1  link, the frame relay converting unit  12  stores state information of the allocated H 0  channel (Step S 49 ). It then converts the traffic of the data call transmitted from the call processing unit  11  to a frame relay, and transmits it through the corresponding H 0  channel to the IWF  20  (Steps S 50 , S 51 ).  
         [0049]    It should be understood that the above-described system and method is not limited to the case that the both bandwidths of the IS-95A and IS-95B are supported. Thus, the present invention is also effectively adopted to a case that an IS-95A-based low speed data call, an IS-95B-based middle speed data call, and an IS-95C-based high speed data call can be supported altogether in consideration of occurrence frequency of each data call.  
         [0050]    For example, after the reference bandwidth is set as 5 units for the middle speed data call, an H 0  channel is allocated in the same manner as described above. If a requested bandwidth is the same as the reference bandwidth, a channel can be allocated in consideration of an occurrence frequency of the high speed data call having 10 units of bandwidth.  
         [0051]    In other words, if the occurrence frequency of the high speed data call is high, the channel allocation method when a requested bandwidth is smaller than the reference bandwidth is used. If, however, the occurrence frequency of the high speed data call is low, the channel allocation method when a requested bandwidth is greater than the reference bandwidth.  
         [0052]    As described herein, the channel allocation method for radio data calls having different bandwidths to each other of the present invention has many advantages. For example, the H 0  channel of the E 1  link is variably allocated according to the bandwidth required for a data call. Consequently, a traffic delay due to a channel congestion is prevented and the channel resources can be more effectively utilized.  
         [0053]    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.