Energy Efficient Parallel Concatenated Index Modulation and $M$-ary PSK Aided OFDM-DCSK Communications With QoS Consideration

In this paper, we propose a parallel concatenated index modulation and M-ary phase shift keying (MPSK) to integrate with carrier interferometry (CI) codes into the orthogonal frequency division multiplex (OFDM) differential chaotic shift keying (DCSK) communication system. Our objective is to meet different quality of service (QoS) user demands while achieving higher energy efficiency and retaining reliable communications with low peak-to-average power ratio (PAPR). In our design, one input bit set is modulated by the index of the CI codes matrix whose rows are rotated circularly, another bit set is mapped to the MPSK symbols to realize the M-ary modulation. Subsequently, the resultant MPSK symbols are modulated by reference chaotic sequences and spread by the information-bearing rotated CI codes matrix at the transmitter. After the OFDM modulations, the information bearing symbols are transmitted over multiple subcarriers. At the receiver, after the non-coherent chaotic correlation demodulation, the maximum likelihood detection method is firstly applied to attain the estimates of the index modulated bit set, which are then used to recover the phases of chaotic sequences for further evaluation of another MPSK modulated symbols. Since no additional energy is required while more bits can be transmitted via the M-ary modulation and index modulation, the energy efficiency can be improved. In addition, thanks to the orthogonality of the CI codes matrix and the spreading in the frequency domain, the PAPR could be suppressed and reliability performances can be improved. Then theoretical analysis is conducted and simulation results validate the theoretical analysis. Moreover, the results demonstrate the superior bit error rate (BER) performances to benchmarks and flexible data rate could be provided for user terminals via different combinations of the index modulation and the M-ary modulation.