Radio reception apparatus, radio reception method and radio reception program capable of switching modulation methods

Abstract

In a radio reception apparatus compatible with adaptive modulation, based on a received IQ signal processed by a reception processing unit, a determining unit calculates EVM that corresponds to a magnitude of shift-off between a true symbol point and the received symbol point. The calculated EVM is averaged and thereafter applied to a control unit. The control unit compares the applied EVM with a prescribed threshold value, and determines with high accuracy, switching among a plurality of modulation methods having different multi-value numbers.

1 - 27 . (canceled)  
   
   
       28 . A radio reception apparatus compatible with a plurality of modulation methods having different multi-value numbers, comprising: 
 a determining unit calculating an error vector corresponding to a distance between an original symbol point of a received signal and an actually received symbol point on an IQ coordinate plane; and    a control unit selecting a modulation method based on said calculated error vector.    
   
   
       29 . The radio reception apparatus according to  claim 28 , wherein 
 when a switching request is made during a communication in a first modulation method having a small multi-value number for switching to a second modulation method having a larger multi-value number, said control unit compares said calculated error vector with a prescribed threshold value,    when it is determined that said calculated error vector is not larger than said prescribed threshold value, said control unit switches the modulation method from said first modulation method to said second modulation method, and    when it is determined that said calculated error vector is larger than said prescribed threshold value, said control unit maintains said first modulation method.    
   
   
       30 . The radio reception apparatus according to  claim 29 , wherein 
 when it is determined that said calculated error vector is larger than said prescribed threshold value, said control unit maintains said first modulation method even when other parameter for evaluating communication quality of a propagation path represents a relatively satisfactory communication quality.    
   
   
       31 . The radio reception apparatus according to  claim 28 , further comprising a reception processing unit performing a reception process of selecting or synthesizing said received signal, wherein 
 said determining unit calculates said error vector of the received signal that has been subjected to said reception process.    
   
   
       32 . The radio reception apparatus according to  claim 28 , further comprising an averaging unit for averaging error vectors for symbol points calculated by said determining unit over a prescribed number of symbols in a frame.  
   
   
       33 . The radio reception apparatus according to  claim 28 , further comprising an averaging unit for averaging error vectors for symbol points calculated by said control unit over frames.  
   
   
       34 . The radio reception apparatus according to  claim 28 , wherein 
 said control unit notifies a radio apparatus of a partner of communication about result of the selection of the modulation method.    
   
   
       35 . A radio reception method in a radio reception apparatus compatible with a plurality of modulation methods having different multi-value numbers, comprising the steps of: 
 measuring an error vector corresponding to a distance between an original symbol point of a received signal and an actually received symbol point on an IQ coordinate plane; and    selecting a modulation method based on said measured error vector.    
   
   
       36 . The radio reception method according to  claim 35 , wherein 
 in said step of selecting a modulation method,    when a switching request is made during a communication in a first modulation method having a small multi-value number for switching to a second modulation method having a larger multi-value number, said measured error vector is compared with a prescribed threshold,    when it is determined that said measured error vector is not larger than said prescribed threshold value, the modulation method is switched from said first modulation method to said second modulation method, and    when it is determined that said measured error vector is larger than said prescribed threshold value, said first modulation method is maintained.    
   
   
       37 . The radio reception method according to  claim 36 , wherein 
 in said measuring step, other parameter for evaluating communication quality of a propagation path is detected in addition to said error vector, and    in said step of selecting a modulation method, when it is determined that said measured error vector is larger than said prescribed threshold value, said first modulation method is maintained even when said detected parameter represents a relatively satisfactory communication quality.    
   
   
       38 . The radio reception method according to  claim 35 , further comprising the step of performing a process of selecting or synthesizing said received signal, wherein 
 in said measuring step, said error vector of the received signal that has been subjected to said process of selecting or synthesizing said received signal is measured.    
   
   
       39 . The radio reception method according to  claim 35 , further comprising the step of averaging error vectors for symbol points measured in said measuring step over a prescribed number of symbols in a frame.  
   
   
       40 . The radio reception method according to  claim 35 , further comprising the step of averaging error vectors for symbol points measured in said measuring step over frames.  
   
   
       41 . The radio reception method according to  claim 35 , wherein 
 in said step of selecting a modulation method, a radio apparatus of a partner of communication is notified about result of the selection of the modulation method.