Generally, an error control scheme used in a communication system is classified into a Forward Error Correction (FEC) scheme and an Automatic Repeat Request (ARQ) scheme.
The FEC scheme corrects an error in received information using a code having an error correction capability, and is used when there is no feedback channel used by a receiver to transmit, to a transmitter, information indicating whether it has successfully received the information transmitted by the transmitter.
The ARQ scheme uses a Cyclic Redundancy Check (CRC) code having high error detection capability, wherein upon detecting an error in received information, a receiver sends a request for retransmission of the defective information to a transmitter.
The FEC scheme has a problem that a data containing an error is maintained when a receiver fails to correct the error. So, the FEC scheme must use a powerful code to correct a plurality of errors to implement a system to ensure high reliability. But, the powerful code increases decoding complexity. The ARQ scheme, though it has a simple structure and high reliability, suffers a drastic reduction in information throughput at a high channel error rate. The HARQ scheme has advantages of both the ARQ scheme and the FEC scheme.
The HARQ scheme is classified into a synchronous HARQ scheme, an asynchronous HARQ scheme, an adaptive HARQ scheme, and a non-adaptive HARQ scheme according to whether a transmission timing point of a retransmitted packet, quantity of resource, and location of the resource are varied.
The synchronous HARQ scheme is a scheme that a transmitter transmits a retransmitted packet in a predetermined period according to a transmission timing point of the retransmitted packet. The asynchronous HARQ scheme is a scheme that a transmitter transmits a retransmitted packet on a packet retransmission timing point determined by a scheduler.
Also, quantity and location of assigned resource vary when the adaptive HARQ scheme is used. On the contrary, quantity and location of assigned resource are fixed when the non-adaptive HARQ scheme is used.
It is preferable to use synchronous HARQ scheme with a fixed retransmission timing point and non-adaptive HARQ scheme with a fixed quantity and location of assigned resource to reduce signaling overhead. But, it is preferable to use asynchronous HARQ scheme with a scheduling gain and adaptive HARQ scheme without consideration for a signaling overhead.
As described above, since signaling overhead can be incurred for a scheduling gain, there is a need that the scheduling gain must be given up to minimize the signaling overhead. So, there is a need for a new HARQ scheme to reduce the signaling overhead and consider the scheduling gain.