Link adaptation with retransmissions for non-binary LDPC codes

We develop a link adaptation scheme based on non-binary LDPC codes for two scenarios: a frequency-selective quasi-static channel and a time-selective flat fading channel with very limited channel state information at the transmitter. For both cases, we present a unified characterization of the coding performance including puncturing and repetition coding which is based on the accumulated mutual information per code symbol. In the following, we apply this description for the adaptation of modulation and code rate. For frequency-selective channels, the modulation is adapted per subchannel while the same code is applied to all subchannels of a link. For fading channels with limited channel knowledge at the receiver, basically the same characterization of the code performance is applied, but in this case the knowledge of the accumulated mutual information is obtained at the receiver and fed back to the transmitter in order to adapt the size of the retransmission units. This approach leads to an adaptive retransmission scheme which maintains the throughput to a great extent although there is no reliable channel state information available. Both schemes can be combined in a straightforward manner and may be embedded into a multi-user multi-carrier system.