Nanonetworking: a New Frontier in Communications

Project Description

Nanotechnology and Nanonetworks

Nanotechnology promises new solutions for several applications in biomedical, industrial and military fields. Nanotechnology enables the miniaturization and fabrication of devices in a scale ranging from one to a few hundred nanometers. At this scale, a nanomachine is considered as the most basic functional unit. Nano-machines are tiny components consisting of a set of molecules able to perform specific tasks at nano-level, such as computing, data storing, sensing or actuation. Nanonetworks, i.e., the interconnection of nanomachines, are expected to expand the capabilities of single nanomachines by allowing them to coordinate, share and fuse information. Nanonetworks can be used as a backbone for the development of more complex systems such as nano-robots and computing devices integrated by nano-processors, nano-memory or nano-clocks.

Because of this, there is the need to define the way in which a single nanomachine communicates with other nanomachines based on their physical and practical limitations. In addition, the interconnection of nanomachines with the micro-world will require the development of nano-micro interfaces. Moreover, the communication among thousands or even millions of distributed nanomachines demands for novel cost-effective hardware and software solutions. Classical communication paradigms need to undergo a profound rethinking and redesign in order to meet the requirements (e.g., size, power consumption, etc.) of these new nanonetworks' applications. Existing networking architectures and communication protocols/software have to be completely rethought in light of these new communication paradigms. [Back to top]

Classical paradigms Vs Nanocommunication

Nanonetworks are not a simple extension of traditional communication networks at the nanoscale: they promote the definition of a complete new communication paradigm. Nanonetworks require innovative communication solutions according to the characteristics of the network components and the communication processes. The main constraints to the application of classical communication paradigms at the nanoscale are:

  • Conventional electromagnetic transceivers are not adequate for this scale because of their complexity, size and power consumption.
  • Acoustic communication based on the transmission of ultrasonic waves cannot be used among nanomachines mainly due to the size of acoustic transducers.
  • Electro-mechanical communication among nanomachines, i.e., the transmission of information through linked devices at nano-level, is limited by the size and random nature.

We address the problem of nano-communication from two different perspectives, namely, the study of the transmission and reception of information encoded by using molecules (Molecular Communication), and the application of quantum mechanics to the design of nano-electromagnetic transceivers based on carbon electronics (Nano-electromagnetic Communication). Apart from the implicit limitations and challenges posted by physically working in the nanoscale (in terms of device manufacturing, deployment and range of operation, amongst others), the main differences from the ICT perspective between nano-communication and traditional communication paradigms can be summarized as follows.

In nano-electromagnetic networks, the message can be encoded in the amplitude, frequency or phase of the EM wave (similarly to classical EM communications), but also on the energy levels and polarization of each single particle composing the wave (similarly to quantum communication mechanisms but in the nanoscale domain). In molecular nanonetworks, the message is encoded using molecules by two different and complementary techniques. The first one uses temporal sequences to encode the information, e.g., molecular signals. The second technique, called molecular encoding, uses internal parameters of the molecules to encode the information such as the chemical structure, relative positioning of molecular elements, polarization, DNA encoding.
Propagation Speed
The propagation speed of the signals used in traditional and quantum electromagnetic networks is much faster than the propagation of molecular messages. In molecular nanonetworks, the molecules have to be physically transported from the transmitter to the receiver either passively by means of diffusion or actively using alternative mechanisms such as molecular motors or bacteria.
In nano-electromagnetic networks, the classical definition of noise is still valid, but new noise factors accounting for the interaction of each one of the particles in the wave and the medium should be taken into account. In molecular nanonetworks, two different types of noise can affect the messages: as classical noise or as an undesired reaction occurring between information molecules and other molecules present in the environment.
Power Consumption
In traditional communication networks, the communication processes consume electrical power that is obtained from batteries or from external sources. In molecular nanonetworks, most of the processes are chemically driven resulting in low power consumption. In nano-electromagnetic networks, we envision that both energy harvesting systems similar to RFID tags and hybrid solutions combining carbon nanotubes and molecular batteries will relax the energy requirements for nanomachines.

Communication Traditional Molecular Nano-electromagnetic
Communication carrier Electromagnetic waves Molecules Electromagnetic waves (THz band)
Signal type Electromagnetic Chemical Electromagnetic
Propagation Speed Light Extremely low Light
Medium Conditions Affect electromagnetic waves propagation Affect diffusion of molecules Affect electromagnetic waves propagation
Noise Electromagnetic fields and signals Chemical Electromagnetic fields, THz band effects
Power Consumption High Low -

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Molecular Communication

Molecular communication is a new and interdisciplinary field that spans nano, bio, and information and communication technologies (ICT). Unlike previous communication techniques, the integration of molecular transceivers in nanomachines is more feasible due to their size and natural domain. These transceivers are nanomachines able to react to specific molecules and to release others as a response to an internal command. The high bio-compatibility, the lower power consumption with reference to the classical communication schemes and the exploitation of truly nanoscale structures (molecules) enable the feasibility of this approach for solving nanocommunications problems.

For molecular communication we are evaluating several different nanonetwork architectures whose classification is based on distances:

  • Short Range (mn-μm)
  • Molecular Motors
    A molecular motor is a protein or a protein complex that transforms chemical energy into mechanical work at a molecular scale. It has the ability to move molecules. Molecular motors travel or move along molecular rails called microtubules.

    Components in molecular motor communication systems.

    Ion Signaling
    The information is transmitted by varying a given concentration of molecules (signals) according to the message that needs to be propagated. The molecule concentration level may be modulated in frequency or in amplitude.

    Signal propagation in calcium signaling communication systems.

  • Medium Range (μm-mm)
  • Flagellated Bacteria
    Bacteria follow gradients of attractant particles in a cellular process called chemotaxis. If the receiver is constantly releasing attractant particles to the environment, the bacteria transport and carry the desired information.

    Encoding of a DNA packet using plasmids.

    Catalytic Nanomotor
    The information can be encoded inside a plasmid attached to the catalytic nanomotor using AEDP and CaCl2. Catalytic nanomotors are able to move in a hydrogen peroxide solution.

    Encoding of the plasmids in the Au/Ni/Au/Ni/Pt nanorods.

  • Long Range (mm-m)
  • Pheromones
    Each node transmits a different molecular compound, thus being clearly identified by its receptor. Pheromones propagate in space by means of diffusion.

    Antenna structure for pheromone reception.

    Pollen and Spores
    There exist different packets that can only be understood by certain receivers. This feature can aid encoding protocols.

    Pollen distribution in first half of mid anthesis.

    Light transduction
    Interfaces of nano and micro devices can be designed using optical signals as common understandable carriers.

    Light transduction technique scheme.

    Axons and Capillaries
    The emulation of axons and capillaries for long-range wired architectures enables the usage of most of communication particles that are already used in animal blood.

    Left: neuron and axons possibly used to transmit action potential impulses between nanonetworks nodes. Right: Capillary circuit in a token ring implementation example.

We investigate the different architectures, the types of molecules, their concentration and the timing aspects of these molecular communication paradigms. We also investigate and understand the physical channel model behavior from an information theory perspective so that we can develop new communication protocols.

We study the molecule diffusion physical channel, both in terms of molecule emission/reception and molecule propagation. In order to initially tackle the molecular communication problem with the most general framework possible, we are concentrating our efforts in the study of the channel based on free molecule diffusion, modeled using the well known Fick's laws. In this initial solution, the desired information modulates the molecule concentration at the transmitter side. This modulated signal is then propagated by the diffusion process to the receiver side where the concentration is sensed and a received signal is generated accordingly. The membrane of a cell contains a large number of receptors (e.g., neurotransmitter-gated channels involved in synaptic communication), to which these molecules may bind, and emitters (e.g. machinery for neurotransmitter or hormone release), which release molecules for short- or long-range communication.

Scheme of the molecule diffusion communication system used for physical channel modeling.

This physical channel model based on free particle diffusion can be applied to networking architectures involving entities communicating by means of particle diffusion at the nanoscale level. For example, both researches on short-range molecular signaling (e.g., using calcium ions, Ca 2+) and on long-range pheromone communication are governed by this model. [Back to top]

Nano-electromagnetic Communication

The limitations of silicon in terms of size, complexity and power consumption, have motivated the study of new materials that could be used as the building block for the incoming nano-devices. Amongst others, one of the most promising candidates is graphene. This novel nano-material consists of a one-atom-thick planar sheet of bonded carbon atoms densely packed in a honeycomb crystal lattice. The unique quantum properties observed in graphene and its derivatives, i.e., Carbon Nanotubes (CNT) and Graphene Nanoribbons (GNR), have drawn the attention of the scientific community in the recent years. Despite the challenges that manufacturing these structures still pose, nano-batteries, nano-memories, logical circuitry in the nanoscale and even nano-antennas have been proposed since the first discovery of Carbon Nanotubes.

The need for compact and reliable transceivers suitable for the nanoscale motivates the study of the electromagnetic radiation properties of graphene and its derivatives. Up to date, several work has been done both from the radio-frequency and the optical perspectives. The main difference between the two trends relies on the interpretation of the radiation in terms of high frequency waves or low energy photons.

In a RF approach, the possibility to manufacture resonant structures in the nanoscale enables the development of novel antenna designs. According to classical antenna theory, the reduction of the antenna dimensions down to a few nanometers would impose the use of resonant frequencies drastically high. However, the reduced speed of electrons in graphene turns into a reduction of the resonant frequency up to one hundred times below the predicted values. The possibility to define an antenna with atomic precision working at feasible resonant frequencies opens a new set of opportunities.

A few initial antenna designs based on graphene have been proposed so far, such as a nano-dipole or a nano-patch antenna. For an antenna size on the order of a few hundreds of nanometers, these antenna structures can radiate EM waves in the Terahertz Band (0.1-10~THz). At the same time, the emission of photons from nano-structures due to electron-phonon interaction has motivated the study of nanotubes and nanoribbons as optical emitters (and reciprocally as detectors too). Amongst others, it has been recently shown that a quasi-metallic carbon nanotube can emit THz radiation when a potential difference is applied to its ends. Going one step further, nanotechnology will enable the development of optical antennas. An optical antenna is a device able to emit/absorb energy to/from the free-space from/to a confined region with a size on the order of the wavelength of the EM field.

Three possible antenna designs based on graphene.

For all these, we believe that the implicit domain of operation for the incoming nano-devices will be the terahertz band. This result has a twofold effect. First, it encourages the use of graphene-based electronics to address the terahertz radiation generation problem in macro-scale Terahertz communications. Second, more within the scope of nanocommunications, it motivates a study of the Terahertz communication channel for future wireless nanonetworks.

Within this project, we will investigate the Teragertz band, transmission range and energy efficiency of novel EM transceivers and, in light of this, define novel networking protocols and architectures. [Back to top]

Envisioned applications

The range of applications in which nanonetworking devices are required is astonishingly wide. We can identify five main areas:

  • Biomedical Applications: e.g., immune system support, bio-hybrid implants, health monitoring mechanisms, drug delivery systems and applications within genetic engineering.
  • Industrial and Consumer Goods Applications: e.g., development of new materials, manufacturing processes and quality control procedures, also for food and water quality control applications, and advanced fabrics and materials development.
  • Military Applications: e.g., nuclear, biological and chemical (NBC) defenses and nano-functionalized equipments;
  • Environmental Applications: e.g., biodegradation assistance, animal and biodiversity control, and air pollution control.
  • Telecommunications, ICT and Future Internet: e.g., distributed execution and management of dynamic and intelligent services in unpredictable environments.

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