Efficient automatic-repeated-request systems for high error rate conditions

The paper deals with some efficient automatic-repeated-request (ARQ) schemes for error control in digital communication systems. The proposed ARQ techniques utilise the redundant information owing to repeated transmission of a same block to perform a soft detection. The M-ary CPFSK schemes are considered in transmission. Coherent and noncoherent soft detection are used in detecting the M-ary CPFSK signals, in particular noncoherent soft detection has been studied to reduce the receiver implementation complexity. The throughput efficiencies for the proposed ARQ schemes are analytically derived and optimised with respect to the number of blocks´ transmitted copies.<>