Channel quality indicator decoding for talk-around direct communications based on IEEE 802.16.1a

Codeword decoding schemes are proposed for the channel quality indicator (CQI) of talk-around direct communications based on IEEE 802.16.1a that supports public protection and disaster relief operations. Since a CQI payload is encoded by using near-orthogonal block encoding, a non-coherent correlation method is employed at the receiver to find the CQI index with maximum correlation. To enhance the decoding performance in high mobility environments, a differential decoding scheme is developed. By combining the correlation method and the differential decoder, a new hybrid decoding scheme is proposed. Since the proposed hybrid decoder uses the correlation approach in slow fading channels and exploits the differential decoding in fast fading channels, its decoding performance is robust to the rate of channel variation. Through theoretical analysis and numerical simulations in direction communication environments, it is shown that the proposed non-coherent decoders are advantageous than a coherent decoding scheme, and the performance of the proposed non-coherent decoders is compared for varying channel variation rate.