Enhancing the Reliability of Large-Scale Multiuser Molecular Communication Systems

Data transmission rate in molecular communication systems can be improved by using multiple transmitters and receivers. In molecular multiple-input multiple-output (MIMO) systems which use only single type of molecules, the performance at the destination is limited by inter-symbol interference (ISI), inter-link interference (ILI) and multi-user interference (MUI). This work proposes a new hybrid modulation for a system with multiple transmitters and receivers which uses different types of molecules to eliminate ILI. Further, to enhance the data rate of the proposed system under ISI and MUI, Mary CSK modulation scheme is used between each transmitter-receiver pair. In this paper, the random locations of transmitters present in the three dimensional (3-D) space are modeled as homogeneous Poisson point process (HPPP). Using stochastic geometry tools, analytical expression is derived for the probability of symbol error for the aforementioned scenario. Finally, the performance of the proposed system is compared using the different existing modulation schemes such as on-off keying (OOK), binary concentration shift keying (BCSK) and quadruple concentration shift keying (QCSK) to develop several important insights.

This paper presents Reed-Solomon (RS) coding applied to an innovative, constant envelope modulation technique that was originally developed by Resnikoff and Tigerman [1]. The general waveform and phaseform are presented as-well-as probability of bit error and symbol error expressions for uncoded binary and uncoded M-ary modulation, respectively. Bit error performance analysis is presented for the case of RS coded waveforms when the modulation symbol size (M) is less than the RS coded symbol size (Q). In addition, upper and lower performance bounds are derived for RS coded waveforms for M less than Q. Performance analysis curves are presented for the M = 8 and Q = 64 case. Finally, simulation results are also presented for the M = 8 and Q = 64 case that strongly agree with analysis.

Hermitian codes are an attractive alternative to Reed-Solomon codes for use in frequency-hop (FH) spread-spectrum packet radio networks. For a given alphabet size, a Hermitian code has a much longer block length than a Reed-Solomon code. This and other considerations suggest that Hermitian codes may be superior for certain applications. Analytical results are developed for the evaluation of the packet error probability for FH transmissions using Hermitian coding. We find there are several situations for which Hermitian codes provide much lower packet error probabilities than can be obtained with Reed-Solomon codes. In general, as the code rate decreases or the symbol alphabet size increases, the relative performance of Hermitian codes improves with respect to Reed-Solomon codes. Performance evaluations are presented for an additive white Gaussian noise channel and for a catastrophic partial-band interference channel, and the packet error probability is evaluated for both errors-only and errors-and-erasures decoding.

The biocompatibility and nanoscale features of Molecular Communication (MC) make this paradigm, based on molecules and chemical reactions, an enabler for communication theory applications in the healthcare at its biological level ( e.g. , bimolecular disease detection/monitoring and intelligent drug delivery). However, the adoption of MC-based innovative solutions into privacy and security-sensitive areas is opening new challenges for this research field. Despite fundamentals of information theory applied to MC have been established in the last decade, research work on security in MC systems is still limited. In contrast to previous literature focused on challenges, and potential roadmaps to secure MC, this paper presents the preliminary elements of a systematic approach to quantifying information security as it propagates through an MC link. In particular, a closed-form mathematical expression for the secrecy capacity of an MC system based on free molecule diffusion is provided. Numerical results highlight the dependence of the secrecy capacity on the average thermodynamic transmit power, the eavesdropper’s distance, the transmitted signal bandwidth, and the receiver radius. In addition, the concept of secure distance in an MC system is introduced and investigated for two different techniques of signal detection, i.e. , based on energy and amplitude. The secrecy capacity can be used to determine how much secure information (bit/sec/Hz) can be exchanged and within which operative range, while the secure distance can be used to set the transmit power to obtain a secure channel at a given distance. We envision these metrics will be of utmost importance for a future design framework tailored to MC systems and their practical applications.

This paper presents coded differential TR (cDTR) receiver that transmits extra bit by mapping information in K different orthogonal codes. The performance of the coded DTR is analyzed and compared with the conventional DTR. Throughout the analysis, the performance of receivers in terms of bit error probability (BEP), data rate and receiver complexity are assessed. The results show that coded DTR is able to outperform conventional DTR receiver in terms of data rate maintaining the same BEP. Additionally, the receiver hardware complexity issue is discussed

Molecular communication is a promising nanoscale communication paradigm that enables nanomachines to exchange information by using molecules as communication carrier. Up to now, the molecular communication channel between a transmitter nanomachine (TN) and a receiver nanomachine (RN) has been modeled as either concentration channel or timing channel. However, these channel models necessitate exact time synchronization of the nanomachines and provide a relatively low communication bandwidth. In this paper, the Molecular ARray-based COmmunication (MARCO) scheme is proposed, in which the transmission order of different molecules is used to convey molecular information without any need for time synchronization. The MARCO channel model is first theoretically derived, and the intersymbol interference and error probabilities are obtained. Based on the error probability, achievable communication rates are analytically obtained. Numerical results and performance comparisons reveal that MARCO provides significantly higher communication rate, i.e., on the scale of 100 Kbps, than the previously proposed molecular communication models without any need for synchronization. More specifically, MARCO can provide more than 250 Kbps of molecular communication rate if intersymbol time and internode distance are set to 2 μs and 2 nm, respectively.

This paper studies the impact of a transmitter's molecule generation process on the capacity of a concentration-based molecular communication (MC) system. Constraints caused by the molecule generation process affect the availability of the molecules at the transmitter. The transmitter has a storage of molecules, and should decide whether to release or save the currently produced molecules. As a result, the MC system has conceptual connections with energy harvesting systems. In this paper, we consider two scenarios on the propagation channel. The first scenario assumes a channel with no inter-symbol interference (ISI), i.e., a memoryless channel. We derive bounds on the capacity of the MC system in this scenario. The second scenario assumes an MC channel with ISI, in which the output of the channel depends on the history of released molecules in the previous time-slots. Based on the assumptions that either the transmitter or the receiver knows the channel statistics, we compute a lower bound on the channel capacity.

Detection in molecular communications with ligand receptors under molecular interference

Molecular communication provides a mechanism for the coordination and control of micro-scale and nano-scale devices. In this paper, we describe simulation models to evaluate a molecular communication system that uses molecular motors to transport information molecules over a filament network. The molecular communication system includes an abstracted sender device that releases the information molecules into the environment and a receiver device that detects those molecules as information. In biological systems, molecules move through the environment using methods such as molecular motors that walk on filaments (for certain intracellular transport) or passive diffusion through Brownian motion (for both inter and intracellular transport). We perform simulations to compare the molecular motor system and a Brownian diffusion system and measure the success rate and delay of communicating to receivers. Recent research in engineering biological systems focuses on communication on a two-dimensional surface, and thus we focus on characterizing communications between a sender and receiver that are randomly located on a surface.

In this paper, a new scheme, named after parallel quadrature index modulation (PQIM) with transmit diversity, is proposed to not only greatly increase the spectral efficiency but also achieve the transmit diversity gain for improving the bit error rate performance. Specifically, the total number of transmit antennas is grouped into multiple groups. For each group, in the in-phase dimension, two components of a three dimension (3D) constellation symbol are modulated on two active transmit antennas; in the quadrature dimension, the remaining one component of the 3D constellation symbol is modulated on only one active transmit antenna. Then, for achieving the diversity gain, each group of transmit antennas modulates an identical 3D symbol. Furthermore, the average bit error probability (BEP) is analyzed. Simulation results demonstrate the proposed PQIM outperforms other schemes in terms of BEP in wireless communication.

Filter bank multi-carrier (FBMC) is a modulation technique with enhanced spectral properties compared with orthogonal frequency division multiplexing (OFDM). In this letter, we investigate the performance degeneration of OFDM and FBMC in doubly-selective channels, that is, time-selectivity and frequency-selectivity. For that, we derive closed-form bit error probability (BEP) expressions for arbitrary linear modulation methods based on one-tap equalizers, with OFDM and FBMC being special cases, covered by our general BEP expressions. We validate our calculations by Monte Carlo simulations and investigate the BEP error if the interference is approximated as Gaussian noise.

Molecular communication is a bioinspired communication that enables macro-scale, micro-scale and nano-scale devices to communicate with each other. The molecular communication system is prone to severe signal attenuation, dispersion and delay, which leads to performance degradation as the distance between two communicating devices increases. To mitigate these challenges, relays are used to establish reliable communication in microfluidic channels. Relay assisted molecular communication systems can also enable interconnection among various entities of the lab-on-chip for sharing information. Various relaying schemes have been proposed for reliable molecular communication systems, most of which lack practical feasibility. Thus, it is essential to design and develop relays that can be practically incorporated into the microfluidic channel. This paper presents a novel design of passive in-line relay for molecular communication system that can be easily embedded in the microfluidic channel and operate without external energy. Results show that geometric modification in the microfluidic channel can act as a relay and restore the degraded signal up-to 28%.

An analytical derivation of the probability of bit error noncoherent frequency-shift keying (FSK) and coherent phase-shift keying (PSK) signals transmitted through a land-mobile satellite channel is described. The channel characteristics used in the analysis are based on a recently developed model which includes the combined effects of fading and shadowing. Analytical expressions for the probability of bit error of FSK and coherent phase-shift keying (CPSK) signals are obtained. The results show that large amounts of signal-to-noise ratio (SNR) are required to compensate for the combined effect of fading and shadowing. An analytical expression for the irreducible probability of bit error of a CPSK signal due to phase variations caused by fading and shadowing is derived. The results described should be useful in the design of land mobile satellite communication systems.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The performance analysis of mobile-to-mobile (M2M) radio communications over double Hoyt fading channels perturbed by additive white Gaussian noise (AWGN) is considered. First, the probability density function (PDF) of the instantaneous signal-to-noise ratio (SNR) per bit is derived under the assumption that the fading channel is a concatenation (product) of two independent but not necessarily identically distributed Hoyt processes. Then, an expression for the bit error probability (BEP) is investigated for several modulation schemes commonly used in wireless communication systems. In the derivation, the underlying propagation channel is assumed to be slowly varying and having the frequency-flat fading characteristics. Numerical results, considering the impact of the fading severity on the BEP, are presented. Furthermore, the validity of the theoretical results is checked by means of computer simulations for some of the modulation schemes used in the analysis. The obtained BEP expression is general and includes, as special cases, results corresponding to the channel combinations given by Rayleigh×Hoyt, Rayleigh×one-sided Gaussian, Hoyt×one-sided Gaussian, double one-sided Gaussian, and double Rayleigh fading channels.

Enhanced connectivity through double RIS uplink MIMO and advanced modulation