Molecular Code Index Modulation: Signaling, Detection, and Performance Analysis

The Internet of Bio-Nano Things (IoBNT) is expected to play a pivotal role in the future healthcare systems. This paper proposes a molecular code index modulation (MCIM) scheme to achieve reliable information transmission for molecular communiction (MC), which may find applications in micro/nano scale networks, including the IoBNT. The MCIM system, making use of two distinct types of molecules, encodes information into the indices of both spreading codes and molecular types. At the receiver, the concentration differences between the molecules of two types with respect to all chips of a code are exploited for information detection. Correspondingly, two low-complexity detectors dispensing with channel state information, namely joint detector and stepwise detector, are proposed based on the correlation detection principles. Furthermore, to mitigate the inter-symbol interference (ISI) caused by the MC channel and specifically structured spreading code, an enhanced stepwise detector is developed to improve the performance of the stepwise detector. The bit error rate (BER) upper bound of the MCIM systems with joint detection, as well as the throughput and the computational complexity of MCIM systems with any detection schemes are analyzed. Our studies demonstrate that the proposed MCIM scheme has the potential to achieve the superior BER and throughput performance at low computational complexity, when compared with the existing modulation schemes employing two molecular types, such as molecular shift keying and molecular type permutation shift keying schemes.