Patent Publication Number: US-2015061935-A1

Title: Method and apparatus for modeling radio wave environment

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     The present invention claims priority of Korean Patent Application No. 10-2013-0105508, filed on Sep. 3, 2013, which is incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to a method and apparatus for modeling a radio wave environment; and more particularly, to a method and apparatus for predicting a radio wave environment that changes in real time in an atypical environment. 
     BACKGROUND OF THE INVENTION 
     Recently, with an increase in the use of robots, research has been actively conducted in various fields. Research into a group of intelligent robots has been conducted in line with the results of research indicating that when the range of work of a robot is wide and the work is complicated, the use of a group of intelligent robots is more efficient than that of a single robot. 
     A method for communication between a group of robots is performed by constructing a network topology for each communication group. In connection with this communication method, Korean Patent Application Publication No. 2013-0068248 (published on Jun. 26, 2013) discloses a configuration in which a communication path is searched for in order to transmit messages between a group of robots based on an atypical environment network. 
     However, the conventional communication method cannot be rapidly applied to the case where a change in a radio wave environment cannot be predicted or the case of a catastrophic situation in which an infrastructure has been destroyed. Furthermore, the Korean patent application publication does not disclose a method of handling a radio wave environment that rapidly changes depending on a change in an environment in the operation of a group of intelligent robots. 
     SUMMARY OF THE INVENTION 
     In view of the above, the present invention provides a method and apparatus for modeling a radio wave environment, which are capable of estimating an environment parameter using information about communication between a leader robot and at least one follower robot in an atypical environment, classifying environment parameters around the robots, and applying the distance between a lattice and at least one follower robot having the same environment parameter to a wave model, thereby constructing a radio wave map. However, an object to be achieved by the present embodiment is not limited to the aforementioned object, and there may be other objects. 
     In accordance with a first aspect of the present invention, there is provided a method of modeling a radio wave environment, the method being executed by a radio wave environment modeling apparatus using a group of intelligent robots. The method includes: measuring an intensity of radio waves received from at least one follower robot; measuring a distance between the at least one follower robot and a leader robot that belongs to the group of intelligent robots; estimating an environment parameter using a wave model; classifying the environment parameter estimated from at least one lattice by comparing the estimated environment parameter with predetermined environment parameters; and analogizing an intensity of radio waves of the at least one follower robot that are received from the at least one lattice. 
     Further, the environment parameter may be an attenuation rate of reception power over distance. 
     Further, the wave model may be a log-distance path loss model. 
     Further, the wave model may be defined by the following Equation: 
     
       
         
           
             L 
             = 
             
               
                 L 
                 0 
               
               + 
               
                 
                   10 
                   n 
                 
                  
                 
                   log 
                    
                   
                     ( 
                     
                       d 
                       
                         d 
                         0 
                       
                     
                     ) 
                   
                 
               
               + 
               
                 ω 
                 _ 
               
             
           
         
       
     
     where L is the reception power, L 0  is reception power at a point d 0  between the at least one follower robot and the leader robot, d is the distance between the at least one follower robot and the leader robot, n is the environment parameter, and  ω  is noise. 
     Further, the environment parameter may be estimated using a filter. 
     Further, analogizing an intensity of radio waves of the at least one follower robot that are received from the one or more lattices may be performed using a non-parametric density estimation method. 
     Further, analogizing an intensity of radio waves of the at least one follower robot that are received from the at least one lattice may be performed based on the following Equation: 
         X   min =arg min x     iεx     {d ( x,x   i )} 
         y ( x )= y ( x   min ) 
     where d(*,*) is a distance function, x is a lattice value, x i  is a position in the at least one follower robot, and y(x) is an environment parameter in the lattice x. 
     Further, the method may further comprise constructing a radio wave map using the intensity of radio waves of the at least one follower robot that has been analogized for the at least one lattice. 
     Further, an environment in which the at least one follower robot are placed may be analogized by comparing the environment parameter estimated from the at least one lattice with the predetermined environment parameters. 
     In accordance with a second aspect of the present invention, there is provided a apparatus for modeling a radio wave environment using a group of intelligent robots. The apparatus includes an intensity measurement unit configured to measure an intensity of radio waves received from at least one follower robot; a distance measurement unit configured to measure a distance between the at least one follower robot and a leader robot that belongs to the group of intelligent robots; an estimation unit configured to estimate an environment parameter using a wave model; a classification unit configured to classify the environment parameter estimated from the at least one lattice by comparing the estimated environment parameter with predetermined environment parameters; and an analogy unit configured to analogize an intensity of radio waves of the at least one follower robot which are capable of being received from the one or more lattices. 
     Further, the intensity measurement unit may measure the intensity of radio waves using at least one medium between the at least one follower robot and the leader robot. 
     Further, the wave model may be defined by the following Equation: 
     
       
         
           
             L 
             = 
             
               
                 L 
                 0 
               
               + 
               
                 
                   10 
                   n 
                 
                  
                 
                   log 
                    
                   
                     ( 
                     
                       d 
                       
                         d 
                         0 
                       
                     
                     ) 
                   
                 
               
               + 
               
                 ω 
                 _ 
               
             
           
         
       
     
     where L is the reception power, L 0  is reception power at a point d 0  between the at least one follower robot and the leader robot, d is the distance between the at least one follower robot and the leader robot, n is the environment parameter, and  ω  is noise. 
     Further, the analogy unit may analogize the intensity of radio waves of the at least one follower robot that are received from the at least one lattice based on the following Equation: 
         x   min =arg min x     iεx     {d ( x,x   i )} 
         y ( x )= y ( x   min ) 
     where d(*,*) is a distance function, x is a lattice value, x i  is a position in the at least one follower robot, and y(x) is an environment parameter in the lattice x. 
     In accordance with an embodiment of the present invention, a radio wave environment that changes in real time can be predicted using information about communication between a group of intelligent robots in an atypical environment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects and features of the present invention will become apparent from the following description of embodiments given in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a configuration diagram illustrating a group of intelligent robots in accordance with an embodiment of the present invention; 
         FIG. 2  is a configuration diagram illustrating the radio wave environment modeling apparatus of the leader robot illustrated in  FIG. 1 ; 
         FIG. 3  is a diagram illustrating an embodiment in which the radio wave environment modeling apparatus of  FIG. 1  models a radio wave environment; and 
         FIG. 4  is a flow chart illustrating a method of modeling a radio wave environment in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, embodiment of the present invention will be described in detail with reference to the accompanying drawings so that they can be readily implemented by those skilled in the art. 
     Throughout the specification and the claims, when an element is described as being “connected” to another element, this implies that the elements may be directly connected together or the elements may be connected through one or more intervening elements. Furthermore, when an element is described as “including” one or more elements, this does not exclude additional, unspecified elements, nor does it preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof. 
       FIG. 1  is a configuration diagram illustrating a group of intelligent robots in accordance with an embodiment of the present invention. Referring to  FIG. 1 , the group of intelligent robots 1 in accordance with this embodiment of the present invention may include a leader robot  100  and at least one follower robot  200 . The group of intelligent robots 1 illustrated in  FIG. 1  is merely an embodiment of the present invention, and thus the present invention should not be construed as being limited to the embodiment of  FIG. 1 . Since the leader robot  100  performs a method of modeling a radio wave environment in accordance with an embodiment of the present invention, the leader robot  100  is assigned the same reference numerals as a apparatus  100  for modeling a radio wave environment. 
     The elements of  FIG. 1  may be typically connected over a wireless network. For example, as illustrated in  FIG. 1 , the leader robot  100  and the at least one follower robot  200  may be connected over a wireless network. If the at least one follower robot  200  includes a plurality of follower robots, the plurality of follower robots may be connected over a wireless network. The leader robot  100  and the at least one follower robot  200  illustrated in  FIG. 1  are not limited to those illustrated in  FIG. 1 . 
     When the group of intelligent robots 1 performs their tasks, the most basic function is communication between the robots 1. The capability to communicate between the leader robot  100  that belongs to the group of intelligent robots 1 and the at least one follower robot  200  is the most important issue in the establishment of cooperation policies. In the performance of tasks using the group of intelligent robots 1, such as searching and rescue, the establishment of a seamless network between the leader robot  100  and the at least one follower robot  200  is an essential requirement. For this purpose, the apparatus  100  for modeling a radio wave environment in accordance with an embodiment of the present invention predicts and models a radio wave environment that varies in real time using information about communication between the robots. 
     The leader robot  100  may include the apparatus  100  for modeling a radio wave environment. The apparatus  100  for modeling a radio wave environment may measure the intensity of radio waves and distance from the at least one follower robot  200 , and may estimate an environment parameter of an environment where the at least one follower robot  200  is placed using a wave model. In this case, the apparatus  100  for modeling a radio wave environment may classify environment parameters by comparing an environment parameter estimated from at least one lattice with predetermined environment parameters, and may analogize the intensity of radio waves of the at least one follower robot  200  that may be received from the at least one lattice. Accordingly, the apparatus  100  for modeling a radio wave environment in accordance with this embodiment of the present invention may predict a radio wave environment that varies in real time using information about communication between the leader robot  100  and the at least one follower robot  200  in an atypical environment. 
     The at least one follower robot  200  enables the leader robot  100  to measure the intensity of radio waves of the at least one follower robot  200  through communication with the leader robot  100 . The at least one follower robot  200  may receive a control signal from the leader robot  100 , or may update its current data stored in the leader robot  100  through communication with the leader robot  100 . 
       FIG. 2  is a configuration diagram illustrating the radio wave environment modeling apparatus of the leader robot illustrated in  FIG. 1 , and  FIG. 3  is a diagram illustrating an embodiment in which the radio wave environment modeling apparatus of  FIG. 1  models a radio wave environment. 
     Referring to  FIG. 2 , the apparatus  100  for modeling a radio wave environment in accordance with an embodiment of the present invention may include an intensity measurement unit  110 , a distance measurement unit  120 , an estimation unit  130 , a classification unit  140 , an analogy unit  150 , and a construction unit  160 . 
     The intensity measurement unit  110  measures the intensity of radio waves that may be received from the at least one follower robot  200 . The intensity measurement unit  110  may measure the intensity of radio waves using at least one type of medium between the at least one follower robot  200  and the leader robot  100 . The at least one type of medium may be, for example, ultraviolet rays, infrared rays, or radio waves. 
     The distance measurement unit  120  measures the distance between the at least one follower robot  200  and the leader robot  100  that belongs to the group of intelligent robots 1. 
     The estimation unit  130  estimates an environment parameter using a wave model. The wave model may be a log-distance path loss model, and may be defined by the following Equation 1: 
     
       
         
           
             
               
                 
                   L 
                   = 
                   
                     
                       L 
                       0 
                     
                     + 
                     
                       
                         10 
                         n 
                       
                        
                       
                         log 
                          
                         
                           ( 
                           
                             d 
                             
                               d 
                               0 
                             
                           
                           ) 
                         
                       
                     
                     + 
                     
                       ω 
                       _ 
                     
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
     where L is reception power, L 0  is reception power at a point d 0  (e.g., 1 m) between the at least one follower robot  200  and the leader robot  100 , d is the distance between the at least one follower robot  200  and the leader robot  100 , n is an environment parameter, and  ω  is noise. 
     In this case, the environment parameter may be the attenuation rate of the reception power over distance, the estimation unit  130  may use a filter in order to estimate an environment parameter, and the filter may be, for example, an extended Kalman filter. When a structure is complicated and many obstacles are present, the value of the environment parameter increases. Furthermore, the environment parameter is a value indicative of the slope of a wave model, and is called a loss coefficient because a signal is highly attenuated over a short distance in response to an increase in the value. The environment parameter may be a value that is the most important index in order to predict the discontinuation of radio waves in a method of modeling a radio wave environment according to the present invention. Indices based on the environment may be classified as listed in the following Table 1: 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 ENVIRONMENT 
                 SLOPE INDEX N 
               
               
                   
                   
               
             
            
               
                   
                 Free Space 
                 2 
               
               
                   
                 Urban Area 
                 2.7 to 3.5 
               
               
                   
                 Shadowed Urban Area 
                 3 to 5 
               
               
                   
                 Indoor Line Of Sight (LOS) 
                 1.6 to 1.8 
               
               
                   
                 Indoor No LOS 
                 4 to 6 
               
               
                   
                   
               
            
           
         
       
     
     A value that is analogized by the apparatus  100  for modeling a radio wave environment in accordance with the embodiment of the present invention is a slope index n. The reason for this is that if a slope index n in a specific area is predicted, it is possible to approximately analogize a corresponding environment that is similar to a radio wave environment in Table 1. 
     Returning to  FIG. 2 , the classification unit  140  classifies an environment parameter estimated from at least one lattice by comparing the estimated environment parameter with predetermined environment parameters. In this case, it is possible to analogize an environment in which the at least one follower robot  200  is placed by comparing the environment parameter estimated from the at least one lattice with the predetermined environment parameters. 
     The analogy unit  150  analogizes the intensity of radio waves of the at least one follower robot  200  that may be received from the at least one lattice. When the analogy unit  150  analogizes the intensity of radio waves of the at least one follower robot  200  that may be received from the at least one lattice, the analogy unit  150  may use a non-parametric density estimation method. 
     Furthermore, the analogy unit  150  may analogize the intensity of radio waves of the at least one follower robot  200  that may be received from the at least one lattice in accordance with the following Equation 2: 
         x   n =arg min x     iεX     {d ( x,x   i )} 
         y ( x )= y ( x   min )  (2)
 
     where d(*,*) is a distance function, x is a lattice value, x i  is the position in the at least one follower robot, and y(x) is an environment parameter in the lattice x. 
     The construction unit  160  may construct a radio wave map using the intensity of radio waves of the at least one follower robot  200  that has been analogized for the at least one lattice. 
     The operation of the apparatus  100  for modeling a radio wave environment in accordance with the embodiment of the present invention, which is configured as described above, will be described below with reference to  FIG. 3 . In accordance with the apparatus  100  for modeling a radio wave environment in accordance with the embodiment of the present invention, the leader robot  100  equipped with a communication module may receive information about radio waves from the follower robots  200  ( 200 ( 2 ),  200 ( 3 ), and  200 ( 3 )) placed in different environments, and may estimate environment parameters at the positions of the follower robots  200  ( 200 ( 2 ),  200 ( 3 ), and  200 ( 3 )) using information based on the intensity of radio waves and the relative positions. Furthermore, the apparatus  100  for modeling a radio wave environment may classify environment parameters around the follower robots  200  ( 200 ( 2 ),  200 ( 3 ), and  200 ( 3 )) using the estimated environment parameter, and may apply the distances between a lattice and the follower robots  200  ( 200 ( 2 ),  200 ( 3 ), and  200 ( 3 )) having the same environment parameter to the wave model, thereby analogizing the intensity of radio waves in each lattice, generating a radio wave map, and analogizing the radius of communication between the robots. 
       FIG. 4  is a flow chart illustrating a method of modeling a radio wave environment in accordance with an embodiment of the present invention. Referring to  FIG. 4 , the apparatus for modeling a radio wave environment measures the intensity of radio waves that may be received from at least one follower robot in operation  54100 . 
     The apparatus for modeling a radio wave environment measures the distance between the at least one follower robot and a leader robot that belongs to a group of intelligent robots in operation  54200 . 
     The apparatus for modeling a radio wave environment estimates an environment parameter using a wave model in operation  54300 , and classifies the environment parameter estimated from at least one lattice by comparing the estimated environment parameter with predetermined environment parameters in operation  54400 . 
     Finally, the apparatus for modeling a radio wave environment analogizes the intensity of radio waves of the at least one follower robot that may be received from the at least one lattice in operation  54500 . 
     Descriptions that are not given in connection with the method of modeling a radio wave environment illustrated in  FIG. 4  are omitted because they are the same as those of the method of modeling a radio wave environment given in conjunction with  FIGS. 1 to 3  or because they can be easily inferred from the given descriptions. 
     The method of modeling a radio wave environment in accordance with an embodiment of the present invention, which has been described in conjunction with  FIG. 4 , may also be implemented in the form of a computer-readable medium including computer-executable instructions, such as an application or a program module that can be executed by a computer. A computer-readable medium may be a specific available medium that is accessible to a computer, and the computer-readable medium includes volatile and non-volatile media and separate and non-separate type media. Furthermore, the computer-readable medium may include both a computer storage medium and a communication medium. The computer storage medium includes all of computer-readable instructions, a data structure, a program module, and volatile and non-volatile and separate and non-separate type media implemented using a specific method or technique and configured to store other data. The communication medium typically includes computer-readable instructions, a data structure, a program module, other data of a modulated data signal, such as a carrier, other transmission mechanisms, and specific information transfer media. 
     While the invention has been shown and described with respect to the embodiments, the present invention is not limited thereto. It will be understood by those skilled in the art that various changes and modifications may be made without departing from the scope of the invention as defined in the following claims.