Molecular Signal Modeling of a Partially Counting Absorbing Spherical Receiver

Abstract

To communicate at the nanoscale, researchers have proposed molecular communication as an energy-efficient solution. The drawback to this solution is that the histogram of the molecules' hitting times, which constitute the molecular signal at the receiver, has a heavy tail. Reducing the effects of this heavy tail, inter-symbol interference (ISI), has been the focus of most prior research. In this paper, a novel way of decreasing the ISI by defining a counting region on the spherical receiver's surface facing towards the transmitter node is proposed. The beneficial effect comes from the fact that the molecules received from the back lobe of the receiver are more likely to be coming through longer paths that contribute to ISI. In order to justify this idea, the joint distribution of the arrival molecules with respect to angle and time is derived. Using this distribution, the channel model function is approximated for the proposed system, i.e., the partially counting absorbing spherical receiver. After validating the channel model function, the characteristics of the molecular signal are investigated and improved performance is presented. Moreover, the optimal counting region in terms of bit error rate is found analytically.

Simulation Study and Analysis of Diffusive Molecular Communications With an Apertured Plane

“…For an MCvD channel with memory L, theoretical BER evaluation ideally requires 2 L cases' error probability evaluations. Stemming from the complexity of such an operation, various performance metrics including signal-to-interference ratio (SIR) [24], signal-to-interference-and-noise ratio (SINR) [25], and signal-to-interference difference (SID) [15] have been proposed in the literature. Inspired by the existence of a correlation between BER and the ratio between a molecular signal's mean and standard deviation [26], we propose an alternative performance metric to evaluate the signal quality in this work.…”

“…Note that SINAR also takes the number of transmitted molecules (M ) into account, which is a key difference when compared to SIR [24] and SID [15] metrics. In addition, the fact that M is used in first order makes physical sense, since the number of transmitted molecules is considered to be directly proportional to energy required to synthesize and/or emit them [27].…”

“…In such a case, [14] considers unbinding the blocking molecules using chemical and optogenetic methods. For an MCvD system consisting of a single transmitter and a single absorbing receiver, a recent work has proposed to partially count the arriving molecules at the receiver end [15]. In other words, [15] considers absorbing all molecules that arrive at the receiver as usual, but only counting the ones that hit to a specific region of the receiver's surface.…”

“…For an MCvD system consisting of a single transmitter and a single absorbing receiver, a recent work has proposed to partially count the arriving molecules at the receiver end [15]. In other words, [15] considers absorbing all molecules that arrive at the receiver as usual, but only counting the ones that hit to a specific region of the receiver's surface. Interestingly, the study shows that if the counted molecules are the ones that arrive at the receiver's side that faces the transmitter, a sense of directivity can be achieved.…”

Analytical derivation of the impulse response for the bounded 2-D diffusion channel

“…Inspired from the nature of diffusion, it is shown that using a partially-counting receiver based on angular position has beneficial effects in molecular communications [16]. Since molecules move slowly, it takes much higher expected time to move to the part of the receiver, which are far from the transmitter.…”