Patent ID: 7522668
Filing Date: 2009-04-21
Classification: H04B,H04L,Y02D

Abstract:
1. A radio communication system comprising: a radio transmitter comprising: an adding unit which adds a parity bit for error detection to data; a spreading unit configured to spread, in a time direction and a frequency direction, the data with the parity bit, based on a spreading pattern; a transmission unit configured to transmit the spread data; and a reception unit configured to receive a retransmission request signal, wherein in response to the retransmission request signal, the spreading unit spreads to-be-retransmitted data with the parity bit, based on a varied spreading pattern which is varied according to at least one of the spreading rate in the time direction and the spreading rate in the frequency direction, and the transmission unit transmits the spread to-be-retransmitted data, wherein the spreading unit varies the spreading rate in the time direction to be larger than spreading rate in the time direction in a last data transmission when retransmitting the data at the (2n+1)-th time (n is an integer equal to zero or more) and also the spreading rate in the frequency direction to be larger than spreading rate in the frequency direction in the last data transmission when retransmitting the data at the (2n+2)-th time, or varies the spreading rate in the frequency direction to be larger than spreading rate in the frequency direction in the last data transmission when retransmitting the data at the (2n+1)-th time and also the spreading rate in the frequency direction to be larger than spreading rate in the frequency direction in the last data transmission when retransmitting the data at the (2n+2)-th time, wherein the spreading unit varies a spreading pattern to acquire products of (spreading rate in time direction)×(spreading rate in frequency direction) to be equal with each other in the last transmission and in a retransmission; and a radio receiver comprising: a reception unit configured to receive the transmitted spread data; a de-spreading unit configured to de-spread the received spread data, based on the spreading pattern; an error detection unit configured to detect an error of the de-spread data, based on the parity bit; and a transmission unit configured to transmit the retransmission request signal requesting a retransmission of the data if the error is detected in the de-spread data, wherein the reception unit receives retransmitted data, and the de-spreading unit de-spreads the retransmitted data, based on the varied spreading pattern.