On the coding scheme for joint channel estimation and error correction over block fading channels

In this work, we propose a novel systematic code construction scheme for joint channel estimation and error correction for channels with independently varying fading subblocks. Unlike the existing noncoherent codes that are designed with the help of computer search, a code of desired code length and code rate can be directly generated with our coding scheme. We then compare our codes with the three-times-repetitive (12, 6) code proposed by Xu et al. for use of channel quality indicator (CQI) in uplink control for IEEE 802.16m. Simulations show that our constructed (36, 6) code has comparable performance to Xu's code when channel coefficients changes randomly in every 12 symbols. If the channel taps remain constant in the entire coding block of length 36, our code outperforms Xu's code by 0.7 dB. This indicates that the new constructed code adapts more robustly to the two simulated scenarios. For frequency selective channels of unit memory order, our simulation results suggest that our code that takes in consideration the varying characteristic of channels can achieve better performance at median-to-high signal-to-noise ratio over the computer-searched, union-bound-minimized code of length less than the varying subblock size. A side advantage of our code construction scheme is that its systematic structure makes it maximum-likelihoodly decodable by the priority-first search algorithm. The decoding complexity is therefore significantly decreased in contrast to that of exhaustive decoder for the structureless computer-searched codes.