A Comprehensive Survey of Recent Advancements in Molecular Communication (1410.4258v3)

Abstract: With much advancement in the field of nanotechnology, bioengineering and synthetic biology over the past decade, microscales and nanoscales devices are becoming a reality. Yet the problem of engineering a reliable communication system between tiny devices is still an open problem. At the same time, despite the prevalence of radio communication, there are still areas where traditional electromagnetic waves find it difficult or expensive to reach. Points of interest in industry, cities, and medical applications often lie in embedded and entrenched areas, accessible only by ventricles at scales too small for conventional radio waves and microwaves, or they are located in such a way that directional high frequency systems are ineffective. Inspired by nature, one solution to these problems is molecular communication (MC), where chemical signals are used to transfer information. Although biologists have studied MC for decades, it has only been researched for roughly 10 year from a communication engineering lens. Significant number of papers have been published to date, but owing to the need for interdisciplinary work, much of the results are preliminary. In this paper, the recent advancements in the field of MC engineering are highlighted. First, the biological, chemical, and physical processes used by an MC system are discussed. This includes different components of the MC transmitter and receiver, as well as the propagation and transport mechanisms. Then, a comprehensive survey of some of the recent works on MC through a communication engineering lens is provided. The paper ends with a technology readiness analysis of MC and future research directions.

• The paper systematically reviews molecular communication mechanisms, detailing both microscale and macroscale systems and their biocompatible applications.
• It highlights diverse transmission methods, including free diffusion, flow-assisted propagation, and bacterial assistance, to overcome limitations of traditional channels.
• The survey outlines future directions focusing on advanced modulation, robust channel models, and error correction codes to enhance communication performance.

Molecular Communication: An Overview of Recent Advancements

The paper "A Comprehensive Survey of Recent Advancements in Molecular Communication" by Farsad et al., offers a thorough review of molecular communication (MC) systems driven by recent breakthroughs in nanotechnology, bioengineering, and synthetic biology. The paper is structured to deliver an extensive exploration, analyzing physical, chemical, and biological processes foundational to MC systems, while highlighting recent research advances and delineating future directions for the field.

Fundamental Concepts and Typologies

Molecular communication is defined as a process where chemical signals, embodying information particles such as molecules or lipid vesicles, are transmitted and received. These particles propagate through an aqueous or gaseous medium until detection and decoding occur at the receiver. The notable biocompatibility and low-energy requirements for generating and propagating MC signals enhance their applicability in complex biological and environmental scenarios unsuitable for electromagnetic communication.

Microscale Molecular Communication

The paper categorically bifurcates MC into microscale and macroscale systems, with the former referring to communication at nm to cm scale distances. Naturally existing in inter-cellular and intra-cellular domains, MC at microscale leverages mechanisms like:

• Free Diffusion: An energy-efficient propagation using Brownian motion, albeit slow for larger distances.
• Diffusion with First Hitting: Common in nature, where molecules are removed upon first detection, mimicking processes like neurotransmitter degradation.
• Flow Assisted Propagation: Turbocharges diffusion via flow, enhancing propagation speeds.
• Molecular Motors: Exploits motor proteins (e.g., kinesin) for active transport of information particles, guided along microtubule tracks.
• Bacterial Assisted Propagation: Utilizes motile bacteria to transport DNA-based information particles.
• Gap Junctions and Neurochemical Propagation: MC through direct cytoplasmic connection or synaptic neurotransmitter diffusion, highlighting intracellular coordination and responses.

Macroscale Molecular Communication

Conversely, macroscale MC pertains to systems where distances span centimeters to meters, and traditional radio systems prove unreliable or costly. For instance, sea water’s salinity disrupts electromagnetic wave propagation, making MC a viable alternative. Here, the interplay of:

• Diffusion and Flow: Extends diffusion’s principles but integrates flow for long-range communication, modeled via advection-diffusion equations.
• Mechanical and Turbulent Flows: Adds complexity by considering fluid dynamics and flow-induced dispersion, relevant for applications in environmental monitoring and robotic systems.

Transmitter and Receiver Mechanisms

Both microscale and macroscale MC systems necessitate intricate transmitter and receiver designs. Transmitters must generate/storage particles and control their release, while receivers detect, decode, and process the received signals. These components can be organic (e.g., genetically modified cells) or synthetic constructs (e.g., artificial cells using lipid vesicles).

Practical Applications and Implications

The implications of MC span a multitude of interdisciplinary domains:

• Medical Nanorobotics: For targeted drug delivery, artificial immune systems, inter-cellular communication in lab-on-a-chip devices.
• Environmental Control: MC can serve in environmental monitoring, ensuring efficient communication within harsh or biologically sensitive areas.
• Bioengineering: Enhances understanding of cellular processes, enabling the design of bio-computers and synthetic biological systems.

Current Research Trends and Future Directions

The paper meticulously maps current research trajectories, revealing:

1. Modulation Techniques: Emphasizes novel methods like molecular shift keying and concentration shift keying, which are critical for optimizing information transfer.
2. Channel Models: Suggests robust mathematical formulations to model environmental dynamics, addressing challenges like ISI and noise.
3. Error Correction Codes: Indicates the necessity for specialized coding algorithms to accommodate the unique aspects of molecular channels.
4. Network Architectures: Explores integrating MC into existing communication paradigms, ensuring seamless interoperability with nanonetworks and biological systems.
5. Experimental and Simulation Tools: Highlights the development of sophisticated simulation platforms and small-scale experimental setups as pivotal for practical validation.

Conclusion

Farsad et al.'s survey underscores the transformative potential of MC systems in various scientific and engineering disciplines. Bridging the theoretical constructs with experimental realizations remains a pivotal challenge, necessitating collaborative efforts across fields. Future research is poised to expand the scope of MC applications, contributing significantly to both the enhancement of existing technologies and the genesis of novel communication paradigms.

With a focus on addressing practical constraints and further refining theoretical models, the field of molecular communication stands at the cusp of significant breakthroughs, promising enhanced capabilities and new avenues for interdisciplinary research and technological innovation.