The modern world fully relies on wireless communication. Because of intrinsic physical constraints of the wireless physical media (multipath, damping, and filtering), signals carrying information are strongly modified, preventing information from being transmitted with a high bit rate. We show that, though a chaotic signal is strongly modified by the wireless physical media, its Lyapunov exponents remain unaltered, suggesting that the information transmitted is not modified by the channel. For some particular chaotic signals, we have indeed proved that the dynamic description of both the transmitted and the received signals is identical and shown that the capacity of the chaos-based wireless channel is unaffected by the multipath propagation of the physical media. These physical properties of chaotic signals warrant an effective chaos-based wireless communication system.

In additive white Gaussian noise channel, chaos has been shown to be the optimal coherent communication waveform in the sense of using a very simple matched filter to maximize the signalto-noise ratio. Recently, Lyapunov exponent spectrum of the chaotic signals after being transmitted through a wireless channel has been shown to be unaltered, paving the way for wireless communication using chaos. In wireless communication systems, inter-symbol interference caused by multipath propagation is one of the main obstacles to achieve high bit transmission rate and low bit-error rate (BER). How to resist the multipath effect is a fundamental problem in a chaos-based wireless communication system (CWCS). In this paper, a CWCS is built to transmit chaotic signals generated by a hybrid dynamical system and then to filter the received signals by using the corresponding matched filter to decrease the noise effect and to detect the binary information. We find that the multipath effect can be effectively resisted by regrouping the return map of the received signal and by setting the corresponding threshold based on the available information. We show that the optimal threshold is a function of the channel parameters and of the information symbols. Practically, the channel parameters are time-variant, and the future information symbols are unavailable. In this case, a suboptimal threshold is proposed, and the BER using the suboptimal threshold is derived analytically. Simulation results show that the CWCS achieves a remarkable competitive performance even under inaccurate channel parameters.

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Some new properties of the chaotic signal have been implemented in communication system applications recently. They include: (i) chaos is proven to be the optimal communication waveform in the sense of very simple matched filter being used to achieve maximum signal to noise ratio; (ii) the amount of information contained in a chaotic signal is unaltered by a wireless multipath channel; and (iii) chaos property can be used to resist multipath effect. All these support the application of chaos in a practical communication system. However, due to the broadband property of the chaotic signal, it is very difficult for a practical transducer or antenna to convert such a broadband signal into a signal that would be suitable for practical band-limited wireless channel. Thus, the use of chaos property to improve the performance of conventional communication system without changing the system configuration becomes a critical issue in communication with chaos. In this paper, chaotic baseband waveform generated by a chaotic shaping filter is used to show that this difficulty can be overcome. The generated continuous-time chaotic waveform is proven to be topologically conjugate to a symbolic sequence, allowing the encoding of arbitrary information sequence into the chaotic waveform. A finite impulse response filter is used to replace the impulse control in order to encode information into the chaotic signal, simplifying the algorithm for high speed communication. A wireless communication system is being proposed using the chaotic signal as the baseband waveform, which is compatible with the general wireless communication platform. The matched filter and decoding method, using chaos properties, enhance the communication system performance. The Bit Error Rate (BER) and computational complexity performances of the proposed wireless communication system are analyzed and compared with the conventional wireless systems. The results show that the proposed chaotic baseband waveform of our wireless communication method has better BER performance in both the static and time-varying wireless channels. The experimental results, based on the commonly-used wireless open-access research platform, show that the BER of the proposed method is superior to the conventional method under a practical wireless multipath channel. * Corresponding author: renhaipeng@xaut.edu.cn information. To avoid the difficulty of the precise synchronization, the Differential CSK (DCSK)[10-12] was proposed. The DCSK system is robust under practical wireless channel and exhibits lower implementation complexity [13]. However, the weaknesses of DCSK are high energy consumption, low data rate, weakened information security and requirement of widewidth delay lines. Subsequently, several variants of DCSK were developed to improve the performance of DCSK in different ways, as shown in Table I. However, these variants of DCSK have low bandwidth efficiency as compared to conventional wireless communication.Another chaotic communication scheme is to encode the information bit...

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This paper proposes a new switched capacitor (SC-Type) inverter for asymmetrical multilevel inverters (MLIs) with fewer components. In order to balance the voltages of the capacitors, the proposed topology uses a special method to charge/discharge the capacitors. In the proposed inverter, the number of switches, the number of dc voltage sources, the amount of blocked voltage in the switches, and the power losses are reduced. Fewer components result in lower size, complexity, and cost of MLI. Cascade connection of the proposed topology is used to achieve a higher number of output voltage levels. The MATLAB simulations and experimental results of a 25-level MLI verify the good performance of the proposed inverter.INDEX TERMS Multilevel inverters (MLIs), switched capacitor inverter, asymmetric topology, components reduction.