This paper considers a diffusion-based molecular communication system, where the transmitter uses reaction shift keying (RSK) as the modulation scheme. We focus on the demodulation of RSK signal at the receiver. The receiver consists of a front-end molecular circuit and a back-end demodulator. The front-end molecular circuit is a set of chemical reactions consisting of multiple chemical species. The optimal demodulator computes the posteriori probability of the transmitted symbols given the history of the observation. The derivation of the optimal demodulator requires the solution to a specific Bayesian filtering problem. The solution to this Bayesian filtering problem had been derived for a few specific molecular circuits and specific choice(s) of observed chemical species. The derivation of such solution is also lengthy. The key contribution of this paper is to present a general solution to this Bayesian filtering problem, which can be applied to any molecular circuit and any choice of observed species.
black The demodulation of RSK signals have previously been considered in @cite_20 @cite_23 . However, each of these works considers only a specific choice of molecular circuit. Instead the results of this paper are general. The general algorithm can be applied to any receiver molecular circuit and for any choice of measurements.
@cite_23 @cite_20
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This paper considers a diffusion-based molecular communication system, where the transmitter uses reaction shift keying (RSK) as the modulation scheme. We focus on the demodulation of RSK signal at the receiver. The receiver consists of a front-end molecular circuit and a back-end demodulator. The front-end molecular circuit is a set of chemical reactions consisting of multiple chemical species. The optimal demodulator computes the posteriori probability of the transmitted symbols given the history of the observation. The derivation of the optimal demodulator requires the solution to a specific Bayesian filtering problem. The solution to this Bayesian filtering problem had been derived for a few specific molecular circuits and specific choice(s) of observed chemical species. The derivation of such solution is also lengthy. The key contribution of this paper is to present a general solution to this Bayesian filtering problem, which can be applied to any molecular circuit and any choice of observed species. Reaction shift keying (RSK) is a recently proposed modulation scheme for diffusion-based molecular communication networks. For RSK, the transmitter uses different chemical reactions to generate different emission patterns to represent different symbols. The receiver front end consists of a molecular circuit and the back end uses a bank of demodulation filter for detection. The aim of this paper is to study the impact of the choice of molecular circuits on communication performance. We consider two circuits: (1) ligand-receptor binding with feedback regulation; (2) ligand-receptor with multiple binding sites. For each circuit, we derive the maximum a posteriori demodulation filter by solving a Bayesian filtering problem. We show that appropriate amount of feedback can reduce symbol error rate. We also show how the choice of measurements in the multiple multiple binding site case can affect communication performance. Demodulation in a random multiple access channel is considered where the signals are chosen uniformly randomly with unit energy. It is shown that by lifting (replicating) the graph of this system and randomizing the graph connections, a simple iterative cancellation demodulator achieves the same performance as an optimal symbol-by-symbol detector of the original system. The iterative detector has a complexity that is linear in the number of users, while the direct optimal approach is known to be NP-hard. However, the maximal system load of this lifted graph is limited to @math $ can go to infinity as the SNR goes to infinity. Our results apply to several well-documented system proposals, such as interleave-division multiple access, partitioned spreading, and certain forms of multiple-input multiple-output communications. In this letter, we propose a new decoding algorithm based on a soft-input soft-output run-length limited (RLL) decoder in visible light communication (VLC) with on–off keying (OOK) modulation and Reed–Solomon (RS) codes. Conventional RLL codes are used for dimming adjustments in VLC; however, in our receiver model, the posterior probability matrix is produced by the new RLL decoder, and it can be matched as the input of the soft RS decoder to enhance the throughput in the VLC system. A significant advantage of our proposed method is that it leads to the enhancement of bit error rate (BER) and frame error rate (FER) performances without any change in the transmitter in VLC systems. The simulation results show that the majority of the BER and FER performances of our proposed method are better than those of hard-input hard-output RLL decoding and soft-input hard-output RLL decoding methods.