Molecular Code-Division Multiple Access for Nanosensor Networks: Signaling, Detection, and Performance

To accomplish relatively complex tasks of, such as, monitoring in vivo, information collected by different nanosensors (NSs) is usually sent via multiple-access channels to fusion centers (FCs) for further processing. Relying on two types of molecules, in this article, a molecular code-division multiple-access (MoCDMA) scheme is designed for multiple NSs to simultaneously send information to an access point (AP) in a diffusive molecular communication (DMC) environment. We assume that different NSs may have different distances from AP, which generates “near-far” effect. Correspondingly, the uniform and channel-inverse-based molecular emission schemes are proposed for NSs to emit information molecules. To facilitate the design of different signal detection schemes, the received signals by AP are represented in different forms. Specifically, by considering the limited computational power of nanodevices, three low-complexity detectors are designed in the principles of matched-filtering (MF), zero-forcing (ZF), and minimum mean-square error (MMSE). The noise characteristics in MoCDMA systems and the complexity of various detection schemes are analyzed. The error performance of the MoCDMA systems with various molecular emission and detection schemes is demonstrated and compared. Our studies and performance results demonstrate that MoCDMA constitutes a promising scheme for supporting multiple-access transmission in DMC, while the channel-inverse-based transmission can ensure the fairness of communication qualities (FoCQs) among different NSs. Furthermore, different detection schemes may be implemented to attain a good tradeoff between implementation complexity and communication reliability.