Abstract:
Problems with communication interface selection control using a fluctuation control equation are that it is difficult for the control to address large environmental variations and that the control requires parameter adjustments according to environments, which incurs operating cost. A communication method according to the present invention includes the step of observing communication environment conditions to generate communication environment data, generating fluctuation information by using the communication environment data as the data occurs, and allocating communication resources by performing attractor selection control on the basis of the fluctuation information. The step of generating fluctuation information comprises the step of using a fluctuation equation to perform fluctuation equation control utilizing the fluctuation information as the fluctuation information occurs. The fluctuation information is not fluctuation terms that are independent random noise terms in the fluctuation equation but include a fluctuation term reflecting the communication environment data.

Description:
This application is a National Stage Entry of PCT/JP2013/003261 filed on May 22, 2013, which claims priority from Japanese Patent Application 2012-197148 filed on Sep. 7, 2012, the contents of all of which are incorporated herein by reference, in their entirety. 
     TECHNICAL FIELD 
     The present invention provides a communication system that controls allocation of communication resources on the basis of attractor selection control. 
     BACKGROUND ART 
     Rapid changes in traffic patterns on a communication network, such as traffic concentration around the same time, are occurring with increasing frequency in these years. To address such rapid variations in traffic patterns, routing control techniques based on attractor selection, which models the mechanism of living organisms behaving adaptively to environmental changes are being studied as one of candidate methods for constructing future new generation network infrastructures. Attractor selection is one of approaches that is based on a biological paradigm and models a state in which living organisms create a stable state (attractor). 
     In classical control methods in general, responses to changes in a given environment are provided beforehand as algorithms for adapting to environmental changes. Accordingly, adaptation to expected environmental changes can be achieved with a high degree of accuracy. On the other hand, adaptation to unexpected environmental changes adds to the complexity of a system and is difficult to implement. To address the problem, methods that model living organisms have been proposed. Attractor selection, which is one of such methods, uses fluctuations to perform control and therefore has accuracy slightly lower than the classical control methods but has the property of more readily adapting to unknown environmental changes. Accordingly, attractor selection control infrastructure techniques, which are communication techniques to which the attractor selection is applied, have the advantage that systems can flexibly respond to environmental changes such as device failures and communication quality variations. 
     A fluctuation equation is generally written as: 
     
       
         
           
             
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     1 
                   
                   ] 
                 
               
               
                 
                     
                 
               
             
             
               
                 
                   
                     
                       ⅆ 
                       m 
                     
                     
                       ⅆ 
                       t 
                     
                   
                   = 
                   
                     
                       α 
                       · 
                       
                         f 
                         ⁡ 
                         
                           ( 
                           m 
                           ) 
                         
                       
                     
                     + 
                     η 
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
     The right-hand side of Equation (1) represents fluctuation information and η represents a fluctuation term (noise term). Attractor selection has two behaviors: the fluctuation term η (noise term) and a control structure f(m) that has an attractor. The behaviors are controlled by an activity α. The activity α is a value indicating a state of the system. When the state of the system degrades, the activity α decreases and the influence of the fluctuation η increases relatively. As a result, the state m of the system randomly changes. When m changes and the state of the system is improved, the activity α increases and m is controlled by f(m). Such a mechanism represents a model in which living organisms respond to environmental changes. Description of typical attractor selection is provided in section III of Non Patent Literature 1. 
     Patent Literature 1 describes a virtual network control method and a virtual network control device that are capable of following environmental variations by using fluctuation equations. 
     Non Patent Literature 1 describes a next-generation wireless network capable of following environmental variations by using fluctuation equations. 
     CITATION LIST 
     Patent Literature 
     [Patent Literature 1] 
     
         
         Japanese Laid-open Patent Publication No. 2011-155508
 
[Non Patent Literature 1]
 
         G. Motoyoshi, N. Wakamiya, and M. Murata, “Future Mobile Network Management With Attractor Selection,” in proceedings of 2012 9th Annual Conference on Wireless On-Demand Network Systems and Services (WONS &#39;12), January 2012. 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     The fluctuation terms (noise terms) that constitute the fluctuation equations given in the literatures are independent and use random numbers according to a normal distribution. A system that has such a configuration requires adjustment of a standard deviation value that corresponds to the amplitude of artificial noise in accordance with the levels of environmental variations beforehand in a system design stage in order to perform communication interface selection control using fluctuation control equations. It is therefore difficult to collectively responding to every condition in a wide range, such as a condition where environmental variations are large and a condition where environmental variations are small. Therefore there is a problem that adjustments of parameters to the levels of environmental variations are required, which incurs operating cost. 
     An object of the present invention is to provide a communication device, a communication method, and a non-transitory computer readable medium that are capable of solving the problem described above. 
     Solution to Problem 
     In one aspect, a communication method includes the steps of observing communication environment conditions to generate communication environment data, generating fluctuation information by using the communication environment data as the data occurs, and allocating communication resources by performing attractor selection control on the basis of the fluctuation information. The step of generating fluctuation information comprises the step of using a fluctuation equation to perform fluctuation equation control using the fluctuation information as the fluctuation information occurs. The fluctuation information is not fluctuation terms that are independent random noise terms in the fluctuation equation but include a fluctuation term reflecting the communication environment data. 
     In another aspect, a communication device is configured to observe communication environment conditions to generate communication environment data. The communication device is further configured to generate fluctuation information by using the communication environment data as the data occurs. The communication device is configured to allocate communication resources by performing attractor selection control on the basis of the fluctuation information. The configuration for generating fluctuation information is configured to use a fluctuation equation to perform fluctuation equation control utilizing the fluctuation information as the fluctuation information occurs. The fluctuation information is configured so that fluctuation terms in the fluctuation equation are not an independent random noise terms but include a fluctuation term reflecting the communication environment data. 
     In still another aspect, a non-transitory computer readable medium includes a set of instructions for causing a computer to perform the communication method described above. 
     Advantageous Effects of Invention 
     The present invention eliminates the need for adjusting a standard deviation value that correspond to the amplitude of artificial noise of a fluctuation term to the levels of environmental variations in a system design stage in order to perform communication interface selection control using a fluctuation control equation. Furthermore, the present invention eliminates the need for parameter adjustments to the levels of environmental variations and therefore can provide a communication system infrastructure with a reduced operating cost. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a functional block diagram of a communication system according to a first exemplary embodiment of the present invention. 
         FIG. 2  is a network configuration diagram of the communication system according to the first exemplary embodiment of the present invention. 
         FIG. 3  is a functional block diagram of an existing communication system relating to the present invention. 
         FIG. 4  is a control flowchart of the communication system according to the first exemplary embodiment of the present invention. 
         FIG. 5  is a network configuration diagram of a communication system (before a domain change) according to a second exemplary embodiment of the present invention. 
         FIG. 6  is a network configuration diagram of the communication system (after the domain change) according to the second exemplary embodiment of the present invention. 
         FIG. 7  is a control flowchart of the communication system according to the second exemplary embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
       FIG. 2  illustrates an example of a radio interface selection control system configuration based on related attractor selection control devised in conjunction with the present invention. It is assumed that a communication terminal  111  includes a plurality of radio interfaces, for example radio interfaces  112  and  113 . The communication terminal is capable of communicating with a plurality of radio base stations through associated radio interfaces. It is also assumed that for example the radio interface  112  communicates through a radio base station A  114  and the radio interface  113  communicates through a radio base station B  115 . 
     As illustrated in  FIG. 3 , the communication terminal includes the function of controlling interface selection and autonomously performs interface selection adaptive to environmental variations. A statistical information collecting unit  101  of the interface selection control function unit collects statistical information concerning communication traffic at the radio interfaces and stores the collected statistical information in a statistical information storage unit  102 . An artificial noise generating unit  107  generates random numbers in accordance with white Gaussian noise that is Gaussian-distributed with an average of 0 and stores the resulting random numbers in an artificial noise storage unit  108 . A fluctuation equation control unit  105  utilizes the information stored in the statistical information storage unit  102  and the artificial noise storage unit  108  to calculate a fluctuation equation and sends the output result to a selecting unit  106 . The selecting unit  106  selects a radio interface to use at the time in accordance with the value. However, the system configuration has a problem that environmental variations need to be predicted and a standard deviation value corresponding to the amplitude of artificial noise needs to be adjusted to the levels of the environmental variations beforehand in a system design stage. 
     Exemplary Embodiments of the present invention will be described below in detail with reference to drawings. 
     First Exemplary Embodiment 
     A communication system of the present invention has a configuration similar to that of the system in  FIG. 2  and includes communication terminals and radio base stations. A communication terminal  111  is a terminal capable of transferring communication data and includes a plurality of radio interfaces. For example, the communication terminal  111  includes radio interfaces  112  and  113  and is capable of communicating with a plurality of radio base stations through the associated radio interfaces. For example, the radio interface  112  can communicate through a radio base station A  114  and the radio interface  113  can communicate through a radio base station B  115 . The part of the exemplary embodiment described so far is the same as the related techniques. 
     The communication terminal  111  includes a radio interface selecting function therein as illustrated in  FIG. 1 . The radio interface selecting function unit includes a communication environment data generating device  300 , a fluctuation information generating device  301  and a selecting unit  106 . The environmental data generating device  300  includes a statistical information collecting unit  101  and a statistical information storage unit  102 . The fluctuation information generating device  301  includes a fluctuation information calculating unit  103 , a fluctuation information storage unit  104  and a fluctuation equation control unit  105 . 
     The statistical information collecting unit  101  collects statistical information concerning communication traffic at each radio interface and stores the collected information in the statistical information storage unit  102 . This operation will be called communication traffic statistical information store step S 101 . Statistical information concerning communication traffic may be information about instantaneously observed communication quality (for example BER: Bit Error Ratio) at an interface, communication quality information (for example SNR: Signal-Noise Ratio), information about an available communication bandwidth (for example BW: BandWidth) and the like calculated from information about packet losses in communication performed. Equation (2) represents a BER calculating Equation. Equation (3) represents an SNR calculating formula. Equation (4) represents a BW calculating formula. 
     [Equation 2]
 
BER=(amount of data successfully received)/(amount of data sent)   (2)
 
[Equation 3]
 
SNR=2 ×erfc   −1 (2×BER)  (3)
 
[Equation 4]
 
BW=(amount of data successfully received)/(unit time)  (4)
 
     Here, erfc is a complementary error function and is generally defined as Equations (5) and (6) given below using an error function erf, which is a type of special function of sigmoid shape. 
     
       
         
           
             
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     5 
                   
                   ] 
                 
               
               
                 
                     
                 
               
             
             
               
                 
                   
                     
                       
                         
                           erfc 
                           ⁡ 
                           
                             ( 
                             x 
                             ) 
                           
                         
                         = 
                           
                         ⁢ 
                         
                           1 
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                             ⁡ 
                             
                               ( 
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                               ) 
                             
                           
                         
                       
                     
                   
                   
                     
                       
                         = 
                           
                         ⁢ 
                         
                           
                             2 
                             
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                   ( 
                   5 
                   ) 
                 
               
             
             
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     6 
                   
                   ] 
                 
               
               
                 
                     
                 
               
             
             
               
                 
                   
                     erf 
                     ⁡ 
                     
                       ( 
                       x 
                       ) 
                     
                   
                   = 
                   
                     
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                         π 
                       
                     
                     ⁢ 
                     
                       
                         ∫ 
                         o 
                         x 
                       
                       ⁢ 
                       
                         
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                   ( 
                   6 
                   ) 
                 
               
             
           
         
       
     
     The fluctuation information calculating unit  103  calculates a fluctuation term η′k on the basis of observational data from the communication traffic statistical information given above. The fluctuation term η′k in interface k can be written as Equation (7) given below. Average μk of BER history of the interface is subtracted from instantaneously observed communication quality information BERk to shift the average of fluctuations toward 0 and the result is multiplied by a fixed-value parameter Ck to adjust amplitude for adaptation to environmental variations. The parameter Ck and the communication quality information BERk may be values specific to each interface or may be values common to the interfaces. The fluctuation terms η′k thus calculated are stored in the fluctuation information storage unit  104 . This operation will be called a fluctuation information calculation step S 102 . 
     [Equation 7]
 
η k   ′=C   k (BER k −μ k )  (7)
 
     The fluctuation equation control unit  105  uses the information stored in the statistical information storage unit  102  and the fluctuation information storage unit  108  to calculate fluctuation equations in Equations (8) to (10) given below (the equations given here are for a case where there are M selectable interfaces). This operation will be called a fluctuation equation calculation step S 103 . The output results are provided to the selecting unit  106 , where a radio interface to be used at the time is selected. This operation will be called an interface selection step S 104 . The fluctuation equation is grounded on a biological control mechanism, which is detailed in Non Patent Literature 1. Output value mk of the fluctuation equation for interface k is updated one after another in accordance with the differential equations given below. Interface k that has the largest value among the output values mk is the interface to be selected under the current environment conditions. β, γ, G, A, θ, Wi and Wj are fixed system parameters. These parameters are adjusted beforehand to optimum values in a system design stage. 
     
       
         
           
             
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     8 
                   
                   ] 
                 
               
               
                 
                     
                 
               
             
             
               
                 
                   
                     
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                         m 
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                   ( 
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                     ⁢ 
                     
                         
                     
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                     Equation 
                     ⁢ 
                     
                         
                     
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                     10 
                   
                   ] 
                 
               
               
                 
                     
                 
               
             
             
               
                 
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                   = 
                   
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                               ( 
                               
                                 
                                   
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     In fluctuation equation (8), the certainty of the selected interface is represented by α. In conditions where α takes a large value, the control terms (the first and second terms of the right-hand side of the fluctuation differential equation) based on communication traffic statistical information become dominant and fine interfaces selection control based on environmental information is performed. On the other hand, in conditions where α takes a small value, the noise term (the third term of the right-hand side of the fluctuation differential equation) which randomly varies becomes dominant and random interface selection control is performed. 
     The fluctuation term (noise term) utilized in the present invention is a fluctuation term generated by utilizing communication traffic statistical information, rather than an independent random noise term. Accordingly, the first and second terms of the right-hand side of the fluctuation differential equation correlate with the third term of the right-hand side of the fluctuation differential equation to some degree and noise term that correlates with environmental variations can be obtained. Therefore, a system is provided that eliminates the need for adjustment of the amplitude of noise term in accordance with environmental variations, which is the problem with the related systems.  FIG. 4  flowcharts the description of this exemplary embodiment of the present invention given above. 
     Second Exemplary Embodiment 
     While selection of a radio interface is used as the system for which fluctuation control is used in the first exemplary embodiment, the control mechanism can be applied to other systems. 
       FIG. 5  illustrates a system configuration diagram. A communication network is made up of a plurality of domains in each of which a control device manages a plurality of communication nodes. As the number of communication terminals that move between base station A and base station B across a domain boundary increases, a problem arises that the amount of control signals between the domains increases. To solve the problem, a system can be provided that uses fluctuation control to change a domain (select a cluster) to which base stations and communication nodes with many communication terminals performing inter-domain handovers belong. An example is illustrated in  FIG. 6  in which node A2 and base station A that belonged to domain A are moved from domain A to domain B. 
     The domain change process is controlled in accordance with the same fluctuation equation that is used in the first exemplary embodiment. First, communication environment data is acquired and stored (communication/control traffic statistical information store step S 201 ). Then, fluctuation information is calculated from the data (fluctuation information calculation step S 202 ). Then each control device calculates fluctuation equation information for communication nodes that belong to its own domain S 203 . The domain to which a base station and a communication node belong is changed (a cluster is selected)  5204 . 
     Since control based on the amount of inter-domain control signals is performed in this system, k of an equation output mk represents the domain to which the communication node is to belong. Moreover, a control equation Q is represented by using the amount of control signal traffic against the amount of user traffic that passes the communication node in this system, thereby the control equation Q can implement the control in order that a communication node through which a large amount of control signals passes come to belong to another domain.  FIG. 7  illustrates a flowchart. 
     Other Exemplary Embodiments 
     A communication system that controls allocation of communication resources on the basis of attractor selection control described in the exemplary embodiments may be implemented using a semiconductor processing device including an ASIC (Application Specific Integrated Circuit). Furthermore, the method may be implemented by causing a computer system including at least one processor (for example, a microprocessor, MPU, or DSP (Digital Signal Processor)) to execute a program. Specifically, one or more programs including an instruction set for causing a computer system to execute an algorithm concerning a bias voltage control described with reference to flowcharts and other drawings may be written and the program or programs may be provided to the computer. 
     The programs can be stored on any of various types of non-transitory computer readable media and provided to a computer. The non-transitory computer readable media include various types of tangible media. Examples of the non-transitory computer readable media include a magnetic recording medium (for example a flexible disk, a magnetic tape, and a hard disk drive), a magneto-optical recording medium (for example a magneto-optical disk), a CD-ROM (Read Only Memory), a CD-R, a CD-R/W, a semiconductor memory (for example a mask ROM, a PROM (Programmable ROM), an EPROM (Erasable PROM), a flash ROM, and a RAM (Random Access Memory)). The programs may be provided to a computer by using any of various types of transitory computer readable media. Examples of the transitory computer readable media include electric signals, optical signals and electromagnetic waves. A transitory computer readable medium can provide programs to a computer through a wired communication path such as an electrical cable, optical fiber, or the like or a wireless communication path. 
     While the present invention has been described with reference to exemplary embodiments thereof, the present invention is not limited by the exemplary embodiments described above. Various modifications that are apparent to those skilled in the art can be made to the configurations and details of the present invention within the scope of the invention. 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2012-197148 filed on Sep. 7, 2012, the entire contents of the disclosure are incorporated herein. 
     REFERENCE SIGNS LIST 
     
         
           101  . . . Statistical information collecting unit 
           102  . . . Statistical information storage unit 
           103  . . . Fluctuation information calculating unit 
           104  . . . Fluctuation information storage unit 
           105  . . . Fluctuation equation control unit 
           106  . . . Selecting unit 
           107  . . . Artificial noise generating unit 
           108  . . . Artificial noise storage unit 
           111  . . . Communication terminal 
           112  . . . Radio interface #1 
           113  . . . Radio interface #2 
           114  . . . Base station A 
           115  . . . Base station B 
           116  . . . Network node A1 
           117  . . . Network node A2 
           118  . . . Network node B1 
           119  . . . Network node B2 
           121  . . . Control device A 
           122  . . . Control device B 
           300  . . . Communication environment data generating device 
           301  . . . Fluctuation information generating device