Towards High-Data-Rate Noncoherent Chaotic Communication: A Multiple-Mode Differential Chaos Shift Keying System

In this paper, we focus on designing a high-data-rate noncoherent chaotic communication scheme to satisfy the demand of the explosive growth in data traffic. To achieve this goal, a joint time-frequency index modulation assisted multiple-mode DCSK (JTFIM-MM-DCSK) system is proposed, where a pair of distinguished signal modes are modulated into the selected subcarriers and another signal mode is transmitted by the unselected subcarriers. In this configuration, besides the modulated bits used for physical transmission, the carrier index bits and time slot index bits, conveyed by the state of whether subcarriers and time slots are selected or not, are also transmitted implicitly to achieve higher data rate. Moreover, the design of multiple-mode signals ensures that it is taking full advantage of all subcarriers and time slots to transmit the information bits, thereby improving the data rate significantly. The bit error rate (BER) expressions of the JTFIM-MM-DCSK system are derived over additive white Gaussian noise (AWGN) and multipath Rayleigh fading channels, which are checked by computer simulations. Finally, the advantage of the JTFIM-MM-DCSK system over other up-to-date noncoherent chaotic communication systems is demonstrated in terms of BER performance through extensive computer simulations.

I. Introduction

With a great potential to offer many favorable advantages, such as easy generation even by a simple nonlinear circuit with very few off-the-shelf electronic components, a delta-function-like auto-correlation property, wide-band, non-periodic and random-like features, chaotic signals have been recognized as the excellent candidate for spread-spectrum communication (SS) and secure communication [1]. Chaotic communication utilizing the chaotic signal as its carrier has been the subject of continued interest in the last two decades [2]. Generally, chaotic communication can be categorized as coherent and noncoherent schemes according to whether the exact replicas of the unmodulated chaotic carriers are needed at the receiver [3]. As a typical representative of coherent chaotic communication schemes, the chaos shift keying (CSK) system [4], [5] can provide better robustness in contrast to the noncoherent counterparts. Unfortunately, these coherent schemes are restricted by the complicated and difficult chaos synchronization. Although increasing efforts have been devoted to studying synchronization algorithms [6]–[8], very little progress was made in tackling this obstacle.