Patent ID: 7539157

Claim:
A communication system in which communication is carried out from a transmitting side to a receiving side by the use of a pilot signal known to said transmitting side and said receiving side and added to information to be transmitted, the communication system comprising: receiving means, in said receiving side, for receiving the pilot signal transmitted by said transmitting side; and line quality judging means, in said receiving side, for treating the pilot signal received by the receiving means as pseudo user data and judging a line quality on the basis of the pseudo user data if the information comprises no user data, wherein a signal transmitted by the transmitting side is a signal interleaved in a predetermined cycle, said line quality judging means comprising a bit extracting portion for judging whether or not the information received by the receiving side contains the user data and extracting the received pilot signal as the pseudo user data if the user data are not contained, a pilot converting portion responsive to the pilot signal from said bit extracting portion for carrying out data conversion of the pilot signal by the use of the pilot signal known to the receiving side into a converted pilot signal and arranging the converted pilot signal at an interval corresponding to an interleaving length, a deinterleaving portion for deinterleaving the information processed by the pilot converting portion to produce deinterleaved information, an error correcting portion for decoding the deinterleaved information processed by the deinterleaving portion to produce decoded information, and an error judging portion for judging an error in the decoded information processed by the error correcting portion, and wherein, when the information contains no user data, the deinterleaving portion deinterleaves the pseudo user data corresponding to the pilot signal, and wherein, when the information contains user data, the deinterleaving portion deinterleaves the user data and does not deinterleave the data corresponding to the pilot signal.