CTN Issue: March 2014

Since Richard Feynman’s talk on top-down nanotechnology, people have eagerly pursued practical work on smaller and smaller scales, most notably through nanotechnology. Nanotechnology, recently, opened a new branch of research called nano communication networks (NCNs), which may be realized by several methods. For example, we can rely on traditional RF communication systems. Such a method, however, has to overcome RF device barriers. Therefore, researchers have introduced a new concept utilizing diffusion that is especially useful for short-range communications.

Molecular communication is an emerging communication paradigm for bio-nanomachines (e.g., artificial cells, genetically engineered cells) to perform coordinated actions in an aqueous environment. This interdisciplinary research is considerably different from the traditional communication system, since it utilizes not electromagnetic waves but biological molecules both as carriers and as information. It originally mimics the existing communication mechanisms in biology, e.g., communications among micro-organisms.

Molecular communication has a variety of potential applications in the biomedical, military, and environmental areas. The most direct and promising applications are in the biomedical field. The advantages provided by molecular communication are from size, biocompatibility, and biostability. Some envisaged applications are drug delivery system (DDS), bio-hybrid implants, and lab-on-a-chip (LoC) systems.

1. Channel Model and Capacity Analysis of Molecular Communication with Brownian Motion

Molecular communication has the potential to explore new application domains of communications technology. One application domain to which molecular communication may be applicable is nanomedicine, where a number of biological nanomachines are injected deeply inside the human body and they coordinate through molecular communications to perform diagnosis and therapy. The design and development of applications of molecular communication involves scientists and engineers from both academia and industry. For instance, IEEE has formed a working group to standardize technologies and specifications to facilitate the research and development of molecular communication.

In this paper, the authors address one of the most fundamental questions in molecular communication, i.e., how many bits of information can be transmitted through molecular communication. Molecular communication is challenging, because the motion of molecules is affected by thermal noise in the environment and thus, molecules randomly move (according to the Brownian motion), arrive at the receiver with large latency and jitter, or the molecules may degrade and never reach the receiver. In this work, the authors develop a model of molecular communication, and demonstrate through analysis that the amount of information that can be transmitted through molecular communication can be maximized by controlling the number of molecules to transmit and the degradation rate of the molecules in the environment.

Title and author(s) of the original paper in IEEE Xplore:

Title: Channel Model and Capacity Analysis of Molecular Communication with Brownian Motion
Author: T. Nakano, Y. Okaie, and J. Q. Liu
This paper appears in: IEEE COMMUNICATIONS Letters
Issue Date: June 2012

2. Molecular Communication in Fluid Media: The Additive Inverse Gaussian Noise Channel

Nanoscale systems are the key to unlocking a realm of futuristic possibilities, transforming what are staples of science fiction into reality: such as self-repairing machines, nanoscale self-assembly, and autonomous microsurgery.  But why are these applications still considered “futuristic”? After all, fundamental building blocks such as micro/nano electromechanical systems (MEMS/NEMS), and systems biology to produce custom microorganisms with designer DNA, have already been available for some time.

However, the transformative applications have one feature in common: they involve not just single devices working independently, but swarms of communicating devices working in concert. Thus, it is the communication problem that remains to be solved, and many of the physical principles used in everyday digital communication break down as devices approach microscale or nanoscale dimensions. Molecular communication has been proposed as a solution to this problem.

This paper provides a useful channel model for nanoscale communication, known as the additive inverse Gaussian noise (AIGN) channel. Analogously to the famous AWGN channel, the AIGN model allows tractable analysis and optimization of an important kind of nanoscale molecular communication system:  individual molecules propagating via Brownian motion. As a key example, the paper is able to find closed-form bounds on the Shannon capacity of the AIGN channel.

Title and author(s) of the original paper in IEEE Xplore:

Title: Molecular Communication in Fluid Media: The Additive Inverse Gaussian Noise Channel
Author: K. V. Srinivas, A. W. Eckford, and R. S. Adve
This paper appears in: IEEE Transactions on Information Theory
Issue Date: July 2012

3. Novel Modulation Techniques using Isomers as Messenger Molecules for Nano Communication Networks via Diffusion

Molecular communication is one of the most promising communication mechanisms for nanoscale communication networks. In molecular communication systems, information can be encoded in molecules’ physical or chemical properties at the transmitter side. The molecules, often called messenger molecules, then propagate through the medium until they arrive at the receiver side where the molecules are detected and decoded. Since tiny transmitters/receivers (or nanomachines) can only function simple tasks, modulation techniques also have to be deployed without any complexity.

Therefore, for molecular communication via diffusion, this paper proposes three novel modulation techniques, i.e., concentration-based, molecular-type-based, and molecular-ratio-based, using isomers as messenger molecules. For example, molecular-ratio-based modulation represents different information with different ratios of messenger molecules. Isomers are molecules that are composed of the same number and types of atoms, and mostly have the same physical properties. Therefore, it reduces transmitter complexity, which synthesizes messenger molecules as well as helps systematic analysis.

Three proposed modulation techniques are (i) isomer-based concentration shift keying (ICSK), (ii) isomer-based molecule shift keying (IMoSK), and (iii) isomer-based ratio shift keying (IRSK). To evaluate the achievable rate performance, this paper compares the proposed techniques with conventional insulin-based concepts under practical scenarios. Analytical and numerical results confirm that the proposed modulation techniques achieve higher data transmission rate than the previous concepts. Also, there is a trade-off relationship between the size of the messenger molecules and modulation order, and guidelines are provided for selecting from among several possible candidates of isomer sets.

Title and author(s) of the original paper in IEEE Xplore:

Title: Novel Modulation Techniques using Isomers as Messenger Molecules for Nano Communication Networks via Diffusion
Author: N.R. Kim and C.B. Chae
This paper appears in: IEEE Journal on Selected Areas in Communications
Issue Date: December 2013