Chaos-Based Anytime Reliable Coded Communications

Anytime reliable communication systems are needed in contexts where the property of vanishing error probability with time is critical. This is the case of unstable real time systems that are to be controlled through the transmission and processing of remotely sensed data. The most successful anytime reliable transmission systems developed so far are based on channel codes and channel coding theory. In this work, another focus is proposed, placing the stress on the waveform level rather than just on the coding level. This alleviates the coding and decoding complexity problems faced by other proposals. To this purpose, chaos theory is successfully exploited in order to design two different anytime reliable alternatives. The anytime reliability property is formally demonstrated in each case for the AWGN channel, under given conditions. The simulation results shown validate the theoretical developments, and demonstrate that these systems can achieve anytime reliability with affordable resource expenditure.Comment: 31 pages, 7 figure

Chaos-Based Multicarrier VLC Modulator With Compensation of LED Nonlinearity

The massive deployment of light-emitting diode (LED) lightning infrastructure has opened the opportunity to reuse it as visible light communication (VLC) to leverage the current RF spectrum crisis in indoor scenarios. One of the main problems in VLC is the limited dynamic range of LEDs and their nonlinear response, which may lead to a severe degradation in the communication, and more specifically in the bit error rate (BER). This is aggravated by the extensive usage of multicarrier multiplexing, based on optical orthogonal frequency division multiplexing (O-OFDM), characterized by a high peak-to-average power ratio. Here, we present a chaos-based coded modulation (CCM) setup specifically adapted to the LED nonlinearities. It replaces the usual modulation, while keeping the multicarrier O-OFDM structure unchanged. First, we obtain a semi-analytical bound for the bit error probability, taking into account the LED nonlinear response. The bound results particularly tight for the range of signal-to-noise ratio of interest. Then, we propose a method to design the modulator based on optimization techniques. The objective function is the semi-analytical bound, and the optimization is applied to a parameterization of the CCM conjugation function. This appropriately shapes the chaotic waveform and leads to BER improvements that outperform classical counterparts under ideal predistortion.Comment: 9 pages, 7 figure