Abstract:
A fuzzy channel allocation controller assuring a quality of service and used in a hierarchical wireless communication system. A system with the fuzzy channel allocation controller is provided, and a threshold for allowing a call entering into the system is adaptively adjusted according to system condition so that the calls are sustained in a predetermined quality. Furthermore, in allocating channels, the loads of the macro cell and micro cells are balanced so that the system has a higher channel utility. This system having a macro cell and a plurality of micro cells which includes a base station interface module, a resource estimator, and a performance estimator and a fuzzy channel allocation processor.

Description:
This application is a 371 of PCT/CN98/00314 filed Dec. 23, 1998. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a fuzzy channel allocation controller. A threshold for allowing a call entering into the system is adaptively adjusted so that the calls are sustained in a predetermined quality. 
     BACKGROUND OF THE INVENTION 
     With the increasing development of wireless communication, wireless communication has become more and more important in the human daily life. The frequency spectrum is an important resource in wireless communication. How to use the spectrum resource effectively so as to increase the system capacity and quality of service is a critical problem in wireless technology. 
     In the conventional channel allocation, methods for sustaining quality of service in handoff calls is to leave part of channels to the handoff calls having a higher priority. While how many channels are required to be left so as to sustain quality of service and to cause the utility of channels achieves an optimum level is a key problem. It is often that a system with a random variation of loads is very difficult since the complexities of the system module and mathematical deduction. The fuzzy channel allocation controller of the present invention has got a result from a system simulation. Comparing with the conventional channel allocation ways, the fuzzy channel allocation controller of the present invention substantially sustains the quality of service and has a higher utility of channels. 
     SUMMARY OF THE INVENTION 
     Accordingly, the primary object of the present invention is to provide a fuzzy channel allocation controller. A threshold for allowing a call entering into the system is adaptively adjusted according to system condition so that the calls are sustained in a predetermined quality. Furthermore, in allocating channels, the loads of the macro cell and micro cells are balanced so that the system has a higher channel utility. 
     To achieve above objects, the present invention provides a fuzzy channel allocation controller which includes a base station interface module, a resource estimator, a performance estimator and a fuzzy channel allocation processor. The base station interface module provides an interface circuit to interface with a base station, and provides separated buffers for registering calls temporarily. The function of the resource estimator is to calculate effective resource as a call occurs, which includes space channels and buffers; and the function of the performance estimator is to adaptively estimate performance of the system. 
     The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is the system construction of fuzzy channel allocation controller assuring a quality of service and used in a hierarchical wireless communication system in the present invention. 
     FIG. 2 is a functional block of fuzzy channel allocation controller assuring a quality of service and used in a hierarchical wireless communication system in the present invention. 
     FIG. 3 is a basic function block view of fuzzy channel allocation controller assuring a quality of service and used in a hierarchical wireless communication system in the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In a fuzzy channel allocation controller, a complete-partitioning buffer serves to register calls not being stored due to no dummy channel for reducing the failure of calling and enhancing quality of service. 
     In the present invention, a fuzzy channel allocation controller with an assurance of quality of service. Referring to FIG. 1, the fuzzy channel allocation controller of the present invention includes a base station interface module  10  (BIM), a resource estimator  20 , a performance estimator  30  and a fuzzy channel allocation processor  40 . The base station interface module  10  has a plurality of buffers for being used by various calls. A macro cell has Nna buffers  101  for new calls, Nha buffers  102  for handoff calls from proximate macro cells, and Nho buffers for the overflow handoff calls of a micro cell. Ith base station interface module  10  provides Nni buffers for new calls in the micro cells. Nhui buffers  112  serves for the underflow handoff calls of a macro cell. Nhi buffers  113  serves for the handoff calls of proximate micro cells. Besides, when dummy channels exist in one micro cell, the calling reverse flow being executing in a macro cell is allowable to be handoff to the channels of micro cells. This way may reduce the call jam and balance the loads on the system. 
     The resource estimator  20  calculates effective performance Q0(t) and Qi(t) of the micro cells and macro cells. The effective resource includes dummy channels and buffers. The performance estimator  30  calculates the failure rate PH0(t) and Phi(t), channel utility of the macro cell and micro cells U0(t) and Ui(t), and estimation (v) of moving customer. The outputs of the fuzzy channel allocation processor is Q 1  and Q 2 . The following table lists the means of Q 1  and Q 2 : 
     
       
         
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Q1 
                 Q2 
                 Meanings 
               
               
                   
                   
               
             
             
               
                   
                 0 
                 0 
                 Using macro cell channel to 
               
               
                   
                   
                   
                 allocating calls 
               
               
                   
                 0 
                 1 
                 Using micro cell channel to allocating 
               
               
                   
                   
                   
                 calls 
               
               
                   
                 1 
                 0 
                 Reject calls to enter into a system 
               
               
                   
                 1 
                 1 
                 Reject calls to enter into a system 
               
               
                   
                   
               
             
          
         
       
     
     In the operation of the fuzzy channel allocation controller, the base station interface module  10  provides resources to various calls. The resource estimator  20  and the performance estimator  30  acquires adaptive information from the system to calculate effective resources and performance estimate of the system adaptives, and then, this message is sent to the fuzzy channel allocation processor  40 . Then, the fuzzy channel allocation processor acquires the call allowable threshold and fuzzy channel allocation control message by a fuzzy induction through fuzzy rule and a database according to the received message. Then, the system determines whether to receive a request for allowing a call to enter into the system and which channel is desired to allocated to the call according to the call allowable threshold and fuzzy channel allocation control message. If the system has determined to accept the request, then the following allocation way is allowable: 
     1. If the new call or handoff call only occurs in the coverage of a macro cell, then the channel of the macro cell is allocated to this call. 
     2. When the new call or handoff call occurs in the overlapping area of a micro cell and a macro cell, then a channel of the micro cell is allocated to this call or this call is overflowed to the macro cell to used the channel of the macro cell. 
     3. If the current call in adjacent macro cell is handoff to the overlapping area of the micro cell and macro cell, a channel of the micro cell can be allocated to this handoff call, or the handoff call is underflowed to the micro cell to use the channel of the micro cell. 
     4. To increase the utility of the micro cell, the call in the macro cell can be reversed to the micro cell. 
     As shown in FIG. 2, the fuzzy channel allocation processor  40  is designed by a concept of fuzzy multiple layer logic control way for facilitating the complexity of the structure. In the present invention, a two layer fuzzy logic controller is used. The first layer is a fuzzy allowable call threshold estimator  401  and the second layer is a fuzzy channel allocation controller  402 . The fuzzy allowable call threshold estimator  401  has variables of handoff call failure rate and available resource and a Sugeno displacement gradient way is used to adjust the call threshold so as to allow the threshold H0(t+1) and Hi(t+1), where “t” represents the new call period, and “t+1” represents next time for generating a call. This call threshold is provided to the second layer, which is used as the fuzzy channel allocation controller allocates fuzzy channels. In the second layer, the fuzzy channel allocation controller  402  has the input variables of handset moving speed, channel utility and available resource. The functions thereof is used in the fuzzy channel allocation for increasing the utility of the channels. The methods for allocating channels in the fuzzy channel allocation controller of the present invention and the prior art have been compared through system simulation, it has proved that the fuzzy channel allocation controller of the present invention substantially sustains the quality of service and has a higher channel utility. 
     The fuzzy channel allocation controller of the present invention formed by a two layer fuzzy logic controller. The interior of the fuzzy logic controller is illustrated in FIG. 3, wherein the input message (X) is fuzzied to become language parameters (step  50 ), and is obtained from deduction (step  60 ). In that deduction, professional knowledge is required to build the deduction rule data (step  70 ) as a basis in that deduction. Finally, the acquired language result from the deduction is fuzzied (step  80 ) to be as an output control signal (Y). 
     Since the present invention is according to the deduction rule database according to fuzzy principle and professional knowledge and a two layer control way is used to reduce the complexity in design. Therefore, the fuzzy logic controller has the following two functions: 
     1. The call allowable threshold can automatically adjust the function of estimation. This function is primarily set the threshold of the call allowable to enter into the system. The higher the threshold, the lower the possibility for being allowed to enter into the system. If the setting of a new call is different from that of a current handoff call, then different priorities can be identified. In general, the executing handoff call is set with a lower threshold for protecting an executing macro cell now. 
     2. Fuzzy channel allocation function: in that, the input variable is an available resource which is the sum of moving speed of a handset, available channel numbers, and number of dummy buffers. Then, a min-max deduction method is used as a deduction basis of fuzzy channel allocation. The final result represents whether the call is accepted or is allowable to use the effective resource in the macro cell or micro cell. 
     The present invention has the following advantages: 
     1. In the design concept of the fuzzy channel allocation controller, a separable buffer is used to register calls which has no channel allocated temporarily so as to reduce the rate of failure and increase the quality of service of the system. 
     2. The separable buffer in the fuzzy channel allocation controller make the system can be managed easily, effectively and conveniently. 
     3. In the design concept of the FCAP, a fuzzy multiple layer logic controller is used for facilitating the complexity in design. In this design, a two layer fuzzy logic control is used so that the design can be facilitated and the complex channel allocation problem. 
     4. The first layer of the fuzzy channel allocation processor is a fuzzy call allowable threshold estimator which has the function of adaptively adjusting call threshold. Thus, it can be operated in a system with a random processing load. In the fuzzy deduction method, a Sugeno displacement gradient way is used to adaptively adjust the call threshold. 
     5. Different allowable call threshold are used in different calls for achieving different call priority. For example, the allowable call threshold is set to be large than the allowable call threshold of handoff calls for achieving different priority. 
     6. The second layer of the fuzzy channel allocation processor is a fuzzy channel allocator. The input variables of the fuzzy channel allocator are selected from effective system messages. For example, moving speed of a handset, available channel numbers, and number of dummy buffers. Then, a min-max deduction method is used as a deduction basis of fuzzy channel allocation. The final result represents whether the call is accepted or is allowable to use the effective resource in the macro cell or micro cell. 
     7. The fuzzy channel allocation processor is according to the fuzzy theory, the decision of output is a soft decision. 
     8. The present invention has been proved that it can balance the channel utility between the micro cell and macro cell so as to achieve a higher channel utility higher than that in the prior art designs. 
     9. The quality of service is sustained. 
     The present invention is thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.