Patent ID: 8295227

Claim:
A radio communication system that transmits and receives packets according to a hybrid automatic repeat request (HARQ) method between a base station and a plurality of radio mobile stations, the base station and each of the radio mobile stations comprising: an RF transmission/reception circuit; a packet transmission circuit that divides an original packet including parity bits into a plurality of subpackets and outputs each of the subpackets to the RF transmission/reception circuit at a predetermined interval; a packet reception circuit for, when receiving one of the subpackets from the RF transmission/reception circuit, repeating decoding processing by combining the received one of the subpackets and a previously received subpacket until the original packet is successfully decoded; and a controller that generates an ACK response, when the original packet is successfully decoded by the packet reception circuit, as a response to the received one subpacket, and generates a NAK response, when the original packet is unsuccessfully decoded, as the response to the received one subpacket, and sends back the ACK or NAK response through the packet transmission circuit at a predetermined timing, wherein, if a size of a subpacket corresponding to the original packet is not shorter than a predetermined size, the controller performs HARQ control such that a transmission of subpackets related to the original packet or responses to transmitted subpackets are transmitted in a normal transmission mode with a first fixed time interval between transmissions related to the original packet, wherein, if a size of a subpacket corresponding to the original packet is shorter than a predetermined size the controller performs HARQ control such that a transmission of subpackets related to the original packet or responses to transmitted subpackets are transmitted in a shortened transmission mode with a second fixed time interval between transmissions related to the original, packet, wherein the second fixed time interval is less than the first fixed time interval, wherein the packet transmission circuit comprises an OFDM (Orthogonal Frequency Division Multiplexing) type transmission circuit where a channel for subpacket transmission and a channel for transmitting the response are formed with a subcarrier group whose subcarriers have different wavelengths, wherein the packet reception circuit comprises an OFDM type reception circuit, and wherein the controller has a management table for storing HARQ control mode information for specifying a HARQ transmission interval so as to be associated with an interlace ID (identification number) indicating a relation between a time frame for subpacket transmission and a time frame for response transmission, and controls the HARQ transmission interval of the shortened transmission mode according to the interlace corresponding to the interlace ID of the management table.