Performance Analysis of Convolutional Coding Techniques in Diffusion-Based Concentration-Encoded PAM Molecular Communication Systems

Abstract

In this paper, we investigate the performance of convolutional coding techniques in an ideal diffusion-based concentration-encoded molecular communication (CEMC) channel with pulse amplitude modulation (PAM) transmission scheme. Convolutional codes have shown to provide a significant amount of gain in the signal-to-interference strength (energy) ratio between a pair of communicating nanomachines and thus help increase the communication range and improve the end-to-end system performance. We have also determined the impact of convolutional codes for several key performance factors, e.g. transmission data rate, communication range, and the constraint length of the convolutional code in the context of diffusion-based CEMC. In addition, we have compared the PAM system with the impulse modulation system in CEMC. We have found that the use of a multilevel (M-ary) signalling scheme in the CEMC system provides a degraded bit error rate performance even in short communication ranges. Therefore, a convolutional coded scheme with larger alphabet size should not be recommended for a CEMC system because of the stronger intersymbol interference produced within symbols. As an alternative, a convolutional coded scheme with binary alphabet and higher symbol rate was evaluated and found to provide a gain in the signal-to-interference energy ratio of the system and is therefore recommended for short- to medium-range CEMC. For long communication ranges, an uncoded system can rather be preferred to convolutional coded schemes.