Radio Communication Device and Radio Communication Method

Abstract

A radio base station 100 judges a receiving state of a radio signal in conformity with the orthogonal frequency division multiplexing scheme, and changes a symbol string configuration of a symbol string defined by a size in a frequency axis direction and in a time axis direction, on the basis of the judged receiving state.

1 . A radio communication device that receives a radio signal from a communication destination by using the orthogonal frequency division multiplexing scheme, the radio signal including a symbol string having a predetermined size in a frequency axis direction and in a time axis direction, and performs control of a radio signal to be transmitted to the communication destination, on the basis of the symbol string included in the received radio signal, the radio communication device comprising:
 a receiving state judging unit configured to judge a receiving state of the radio signal; and   a symbol string configuration changing unit configured to change a symbol string configuration of the symbol string defined by the size in the frequency axis direction and in the time axis direction, on the basis of the receiving state judged by the receiving state judging unit.   
     
     
         2 . The radio communication device according to  claim 1 , further comprising a symbol configuration notification unit configured to notify the communication destination of the symbol string configuration changed by the symbol string configuration changing unit. 
     
     
         3 . The radio communication device according to  claim 1  or  2 , wherein
 the symbol string configuration includes a reference symbol string configuration, and a narrowband symbol string configuration having a size in the frequency axis direction smaller than the reference symbol string configuration, and 
 the symbol string configuration changing unit changes the symbol string configuration from the reference symbol string configuration to the narrowband symbol string configuration, when the receiving state judging unit judges that the receiving state satisfies a predetermined condition. 
 
     
     
         4 . The radio communication device according to  claim 1  or  2 , wherein
 the symbol string configuration includes a reference symbol string configuration, and a wideband symbol string configuration having a size in the frequency axis direction larger than the reference symbol string configuration, and 
 the symbol string configuration changing unit changes the symbol string configuration from the reference symbol string configuration to the wideband symbol string configuration, when the receiving state judging unit judges that the receiving state satisfies a predetermined condition. 
 
     
     
         5 . The radio communication device according to  claim 1  or  2 , wherein
 the symbol string configuration includes a reference symbol string configuration, a first narrowband symbol string configuration and a second narrowband symbol string configuration, the first narrowband symbol string configuration having a size in the frequency axis direction smaller than the reference symbol string configuration, the second narrowband symbol string configuration having a size in the time axis direction larger than the first narrowband symbol string configuration, and 
 the symbol string configuration changing unit changes the symbol string configuration from the reference symbol string configuration to the first narrowband symbol string configuration when the receiving state judging unit judges that the receiving state does not satisfy a predetermined condition, and changes the symbol string configuration from the first narrowband symbol string configuration to the second narrowband symbol string configuration when the receiving state judging unit judges that the receiving state does not satisfy the predetermined condition even in the first narrowband symbol string configuration. 
 
     
     
         6 . The radio communication device according to  claim 3 , wherein
 the radio communication device receives a radio signal including the symbol string and performs adaptive array control of the radio signal transmitted to the communication destination, on the basis of the symbol string included in the received radio signal,   the symbol string includes preamble symbols used in calculation of an array weight, and   the symbol string configuration changing unit changes the reference symbol string configuration and the narrowband symbol string configuration to symbol string configurations having a same number of preamble symbols.   
     
     
         7 . The radio communication device according to  claim 4 , wherein
 the radio communication device receives a radio signal including the symbol string and performs adaptive array control of the radio signal transmitted to the communication destination, on the basis of the symbol string included in the received radio signal,   the symbol string includes preamble symbols used in calculation of an array weight, and   the symbol string configuration changing unit changes the reference symbol string configuration and the wideband symbol string configuration to symbol string configurations having a same number of preamble symbols.   
     
     
         8 . The radio communication device according to  claim 1  or  2 , wherein
 the symbol string includes preamble symbols used in calculation of an array weight, and 
 the symbol string configuration changing unit changes a symbol string configuration of the preamble symbols defined by a size in the frequency axis direction and in the time axis direction. 
 
     
     
         9 . A radio communication method in which a radio signal including a symbol string having a predetermined size in a frequency axis direction and in a time axis direction is received from a communication destination by using the orthogonal frequency division multiplexing scheme, and in which an adaptive array control of a radio signal to be transmitted to the communication destination is performed on the basis of the symbol string included in the received radio signal, the radio communication method comprising the steps of:
 judging a receiving state of the radio signal; and   changing a symbol string configuration of the symbol string defined by the size in the frequency axis direction and in the time axis direction, on the basis of the judged receiving state.   
     
     
         10 . The radio communication method according to  claim 9 , further comprising the step of notification the communication destination of the symbol string configuration changed in the step of changing the symbol string configuration. 
     
     
         11 . The radio communication method according to  claim 9  or  10 , wherein
 the symbol string configuration includes a reference symbol string configuration and a narrowband symbol string configuration having a size in the frequency axis direction smaller than the reference symbol string configuration, and 
 in the step of changing the symbol string configuration, the symbol string configuration is changed from the reference symbol string configuration to the narrowband symbol string configuration, when it is judged that the receiving state satisfies a predetermined condition. 
 
     
     
         12 . The radio communication method according to  claim 9  or  10 , wherein
 the symbol string configuration includes a reference symbol string configuration and a wideband symbol string configuration having a size in the frequency axis direction larger than the reference symbol string configuration, and 
 in the step of changing the symbol string configuration, the symbol string configuration is changed from the reference symbol string configuration to the wideband symbol string configuration, when it is judged that the receiving state satisfies a predetermined condition. 
 
     
     
         13 . The radio communication method according to  claim 11 , wherein
 the symbol string includes preamble symbols used in calculation of an array weight, and,   in the step of changing the symbol string configuration, the reference symbol string configuration and the narrowband symbol string configuration are changed into symbol string configurations including a same number of preamble symbols.   
     
     
         14 . The radio communication method according to  claim 12 , wherein
 the symbol string includes preamble symbols used in calculation of an array weight, and   in the step of changing the symbol string configuration, the reference symbol string configuration and the wideband symbol string configuration are changed into symbol string configurations including a same number of preamble symbols.   
     
     
         15 . The radio communication method according to  claim 9  or  10 , wherein
 the symbol string includes preamble symbols used in calculation of an array weight; and 
 in the step of changing the symbol string configuration, the symbol string configuration of the preamble symbols defined by a size in the frequency axis direction and in the time axis direction is changed.