Echo state network based symbol detection in chaotic baseband wireless communication

The Chaotic Baseband Wireless Communication System (CBWCS) is expected to eliminate the Inter-Symbol Interference (ISI) caused by multipath propagation by using the optimal decoding threshold that is the sum of the ISI caused by past decoded bits and the ISI caused by future transmitting bits. However, the current technique is only capable of removing partial effects of the ISI, because only past decoded bits are available for the suboptimal decoding threshold calculation. The unavailability of the future information needed for the optimal decoding threshold is an obstacle to further improve the Bit Error Rate (BER) performance. In contrast to the previous method using Echo State Network (ESN) to predict one future bit, the proposed method in this paper predicts the optimal decoding threshold directly using ESN. The proposed ESN-based threshold prediction method simplifies the symbol decoding operation by avoiding the iterative prediction of the output waveform points using ESN and accumulated error caused by the iterative operation. With this approach, the calculation complexity is reduced compared to the previous ESN-based approach. The proposed method achieves better BER performance compared to the previous method. The reason for this superior result is twofold. First, the proposed ESN is capable of using more future symbols information conveyed by the ESN input to obtain more accurate threshold rather than the previous method in which only one future symbol was available. Second, the proposed method here does not need to estimate the channel information using Least Squared (LS) method, which avoids the extra error caused by inaccurate channel information estimation. Simulation results and experiment based on a wireless open-access research platform under a practical wireless channel show the effectiveness and superiority of the proposed method.