Molecular code division multiple access in nano communication systems

Transmission of information in nano-networks can be implemented by the emission and reception of molecules in diffusion-based molecular communications. Since the propagation environment is shared among multiple nodes, the molecules emitted by different transmitters cause interuser interference (IUI). In this paper, we propose molecular code division multiple access (MCDMA) to overcome the IUI caused by transmitted signals from asynchronous users. Based on adopting on-off keying (OOK) modulation scheme in implementing molecular codes, we develop a chip detection scheme with an adaptable threshold to decide between “on” and “off” hypotheses, by counting the number of received molecules. To eliminate the inter-symbol interference (ISI) caused by residual molecules, the receiver is modified by exploiting previously detected chips. The performance evaluation of the proposed MCDMA system via computer simulations show that the symbol error rate (SER) of the receiver considering previously detected chip outperforms the memory-less receiver. Results indicate that the MCDMA system is a promising approach to reduce interference created by asynchronous users in multi-user molecular communications.