Mode synchronization in adaptive coding and interleaving systems

Communication systems employing variable rate adaptive error correction codes and adaptive interleaving have been proposed recently. These systems require the receiver to feedback the channel state information to transmitter so that the most efficient mode of operation can be selected. A problem behind these systems is to ensure that both the transmitter and receiver are operating at the same modes. This refers to mode synchronization. In this paper, we propose and compare two general schemes, namely the closed-loop and quasi-closed loop schemes. The closed loop method, which embeds the mode sequence of the current frame in the control header of the forward channel, achieves mode synchronization at the expense of huge overhead. Thus, we proposed the quasi-closed loop method to achieve tradeoff between performance and overhead. Simulation results show that low lost sync rate is achieved with minimal overhead with the proposed scheme.