Radio communication system and apparatus

Abstract

A radio communication system for transmitting a radio signal with a transmission format in which a channel response calculation preamble signal serving as a reference upon reception is inserted is disclosed. The output frequency of channel response calculation preamble signals is varied in accordance with a temporal change in radio propagation environment. A channel response variation measurement unit measures a variation of the radio propagation environment. A channel response calculation preamble signal output frequency setting unit sets the output frequency of preamble signals in accordance with the temporal change in radio propagation environment. The preamble signals are inserted in the transmission format to be transmitted at that frequency.

1 . A radio communication apparatus comprising:
 a receiver receiving a radio signal;   a first unit configured to obtain a channel response by use of the radio signal;   a second unit configured to measure amplitude or phase from an obtained channel response by the second unit and to determine a variation of a radio propagation environment based on a measured result;   a third unit configured to set a frequency of insertion of preamble signals based on the variation, the preamble signals being used for obtaining a channel response at a receiving side; and   a transmitted signal generator configured to generate a transmitted signal by inserting the preamble signals in accordance with the set frequency of insertion and inserting an output frequency field indicating the frequency of insertion of the preamble signals, the preamble signals being separated with respect to time,   wherein the third unit refers to an output frequency field contained in the radio signal received by the receiver so as to control the frequency of insertion based on the output frequency field.   
   
   
       2 . The apparatus according to  claim 1 , wherein the frequency of insertion of the preamble signals are increased as the variation of the radio propagation environment gets larger. 
   
   
       3 . A radio communication method comprising:
 receiving a radio signal;   obtaining a channel response by use of the radio signal;   measuring amplitude or phase from an obtained channel response by the obtaining, and determining a variation of a radio propagation environment based on a measured result;   setting a frequency of insertion of preamble signals based on the variation, the preamble signals being used for obtaining a channel response at a receiving side; and   generating a transmitted signal by inserting the preamble signals in accordance with the set frequency of insertion and inserting an output frequency field indicating the frequency of insertion of the preamble signals, the preamble signals being separated with respect to time,   wherein the third unit refers to an output frequency field contained in the radio signal received by the receiving so as to control the frequency of insertion based on the output frequency field.   
   
   
       4 . The method according to  claim 3 , wherein the frequency of insertion of the preamble signals are increased as the variation of the radio propagation environment gets larger. 
   
   
       5 . A radio communication apparatus comprising:
 a receiver receiving a radio signal having symbols;   a first unit configured to calculate a total power of the symbols;   a second unit configured to measure amplitude or phase of the total power, to determine a variation of a radio propagation environment based on a measured result;   a third unit configured to set a frequency of insertion of preamble signals based on the variation, the preamble signals being used for obtaining a channel response at a receiving side; and   a transmitted signal generator configured to generate a transmitted signal by inserting the preamble signals in accordance with the frequency of insertion, the preamble signals being separated with respect to time,   wherein the third unit refers to an output frequency field contained in the radio signal received by the receiver so as to control the frequency of insertion based on the output frequency field.   
   
   
       6 . The apparatus according to  claim 5 , wherein the frequency of insertion of the preamble signals is increased as the variation of the radio propagation environment gets larger. 
   
   
       7 . A radio communication apparatus comprising:
 a receiver receiving a radio signal having symbols, the symbols each including a pilot carrier;   a first unit configured to measure amplitude or phase of the pilot carrier, to determine a variation of a radio propagation environment based on a measured result;   a second unit configured to set a frequency of insertion of preamble signals based on the variation, the preamble signals being used for obtaining a channel response at a receiving side; and   a transmitted signal generator configured to generate a transmitted signal by inserting the preamble signals in accordance with the frequency of insertion, the preamble signals being separated with respect to time,   wherein the second unit refers to an output frequency field contained in the radio signal received by the receiver so as to control the frequency of insertion based on the output frequency field.   
   
   
       8 . The apparatus according to  claim 7 , wherein the frequency of insertion of the preamble signals is increased as the variation of the radio propagation environment gets larger.