A resource assignment method for a communication system provides a method to realize an estimate of channel with high accuracy for terminals which change channels rapidly. A resource assignment unit (102), supplied with channel information ISCI1 to NSCIN, determines assignment of resources to a first to a Nth terminals and outputs a resource assignment information SRA. A multiplex signal generating unit (103), supplied with the resource assignment information SRA, outputs a transmission signal STX. A resource selector (104), supplied with the channel information 1SCI1 to NSCIN and the relative position information SRP, determines the assignment of resources to the first to Nth terminals and outputs the resource assignment information SRA. A resource position generating unit (105), supplied with the resource assignment information SRA, calculates a relative position of an empty resource with respect to a multiplex position of a pilot signal and outputs the relative position information SRP.