Capacity and Delay Spread in Multilayer Diffusion-Based Molecular Communication (DBMC) Channel

Abstract

In nanoscale communication, diffusion-based molecular communication (DBMC) in which information is encoded into molecule patterns by a transmitter nanomachine, has emerged as a promising communication system, particularly for biomedical and healthcare applications. Although, numerous studies have been conducted to evaluate and analyze DBMC systems, investigation on DBMC system through a multilayer channel has received less attention. The aims of this paper are to formulate channel characteristics and to evaluate the performance of multilayer DBMC channel in terms of delay spread and capacity. In this paper, the propagation of molecules over an n- layer channel is assumed to follow the Brownian motion and subjected to Fick's law of diffusion. Fourier transform is used to convert time to frequency domain functions. Besides, the multilayer channel is considered as a linear and deterministic channel. For the performance evaluation, the air-water-blood plasma medium representing the simplified multilayer diffusion model in the respiratory system was chosen. It was found that a high channel capacity can be achieved with wide transmission bandwidth, short transmission distance, and high averaged transmitted power. In addition, the findings showed that channel delay spread increases as both the transmission distance, and the pulse duration increased. By setting the symbol duration greater than the pulse duration or delay spread, an inter-symbol interference problem due to previous molecules transmission can be mitigated. These findings can be used as a guide in the development and fabrication of future artificial nanocommunication and nanonetworks systems involving multilayer transmission medium.

Modelling of multilayer biological medium under molecular communication paradigm

“…The peak time increases because the molecules will take longer time to reach the RN. When average diffusion coefficient for multilayer diffusion is employed [11]- [12], we can observe the larger deviation of the received signal from the actual received signal derived analytically for a three-layer MCvD medium. This shows that the averaging approach can"t predict the amplitude and time characteristics of the molecular received signal accurately in a multilayer MCvD medium .…”

“…Moreover, it is shown that the effective averaging approach for multilayer medium available in the literature [11]- [12] fails to model the multilayer molecular communication environment accurately. The proposed model has important applications in biomedical engineering, particularly, in the design of future targeted drug delivery system where it can be used for predicting the actual drug concentration around the target site.…”

“…There are some other works [11]- [12] which consider the multilayer molecular medium but only to calculate the average effective diffusion coefficient. Then, the diffusion coefficients of each of the multiple layers are replaced by the average effective diffusion coefficient which then is substituted into the well-known expression for molecular concentration of a single layer medium.…”

Performance of diffusive molecular communication systems with binary molecular shift keying modulation

“…In the literature, a lot of research has been carried out in the context of DMC. As some examples, when assuming that the transmitter, receiver or both employ channel knowledge, the capacity of different DMC channels has been investigated [18][19][20][21][22]. In terms of signalling, DMC may make use of molecular concentration to form concentration shift keying (CSK) [18,[23][24][25][26][27], of molecular pulse positions to yield pulse position modulation (PPM) [28], and of molecular types to allow molecularshift keying (MoSK) [24,29,30], which constitute the three basic modulation schemes for information transmission in DMC.…”

Modeling a Composite Molecular Communication Channel

“…However, this work examined the performance of different estimators for a homogeneous medium of single diffusion coefficient without providing any insight M about modelling a multiple-region medium. Recently, in the literature, the channel impulse response (CIR), delay spread etc., have been derived for a MCvD medium with multiple regions with different diffusion properties by replacing it with an equivalent homogeneous medium having a single region with an effective diffusion properties [19]- [20]. The effective (average) diffusion coefficient is derived in [19]- [20] by averaging the diffusion coefficients of all the multiple regions.…”