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Components of CANET Nano-Node

By Vandana Sharma, on July 17, 2017

In CANET, performance of nanoscale communication among network nodes, i.e nanonode, is affected by the capabilities of four fundamental hardware components, i.e., nanotransceiver, nanopower, nanoprocessor, and nanomemory units.

Carbon Nanotube Radio

The mechanical resonance frequencies of CNT are in the range of 50 MHz–5 GHz, and this range clearly overlaps with the microwave communication spectrum used in traditional wireless communication systems. Hence, this overlapping gives inspiration for developing many innovative nanoelectronic devices. Recently, a single CNT has been designed as the four fundamental components of a radio circuitry, i.e., antenna, tuner, modulator, and demodulator, to receive radio broadcasts. The operation principles of nanotube radio, i.e., CNT radio or CNT receiver, are extremely different from traditional radios since RF signal reception, tuning, amplification, and demodulation are electromechanical processes rather than completely electrical. When the frequency of the incoming wave matches the resonance frequency of the nanotube, the vibrations tune to the incoming wave. Hence, this electromechanical process allows the nanotube to receive the incoming signal. The resonance frequency of the nanotube, i.e. f, is affected by the length of the nanotube, i.e. L, such that f ∝ 1/L2 can be given. To receive a specific radio broadcast, resonance frequency of the nanotube must be initially set by regulating the length of the nanotube. However, the length of the nanotube may be exposed to possible degradation due to the field emission current that traverses in the nanotube. For the amplification and modulation of the incoming signal, DC bias voltage between the electrodes is used. The field- emission current generated by the bias voltage is demodulated via the mechanical vibrations.

Tunneling Nanotube Radio

Beside its usefulness as a nanoscale receiver circuitry, the current form of CNT radio has severe restrictions, outlined as it requires 200 V of power supply to work, it can only tune to 4 MHz, which is five times lesser than the FM bandwidth of 88–108 MHz. Tunneling nanotube radio is proposed to address the above challenges. To cut the required power level, a tunneling detection method is proposed instead of field emission obtained from the vibrating charged tip of CNT.

Nanotransmitter

Electromechanical vibrations of nanotubes can also be harnessed to design a nanoscale transmitter circuitry. In, using a CNT, an electromechanical transmitter circuitry is devised. The four fundamental components of a transmitter circuitry, i.e., modulator, oscillator, antenna, and amplifier, are implemented using a CNT. Frequency modulation (FM) in the nanotube transmitter is realized by modulating the mechanical resonance frequency of the CNT. This mechanical modulation can be performed by an external electrode fed by another power source (V Tension). The information signal can be applied to this electrode for the modulation. The nanotube works as an antenna to permit the radiation of the modulated information signal. Finally, the power of the radiated information signal can be regulated by changing the oscillation amplitude of the nanotube, or increasing the charge in the nanotube, or using an array of nanotubes.

Carbon Nanotube Antenna

Due to their promising electromagnetic characteristics, CNT-based antennas are favorable in different frequency regimes ranging from microwave to visible. One of the important parameters of a CNT is its quantum resistance, which is much smaller than the normal metal wire with the same geometry in nanometer scale. The skin effect in CNT can also be ignored when the operating frequency reaches terahertz. Therefore, the power dissipation of a CNT antenna is low, and this also leads to high antenna efficiency with respect to a metal wire with the same size. However, theoretical estimates show that due to the estimated –90 dB of losses imposed by ohmic currents, the radiation efficiency of a single-walled CNT antenna, i.e , η=(Pr/Pr)+Pt, is very low, i.e., on the order of 10-4 and 10-5, where Pr is the radiated power and Pt is the power of the thermal losses. Thus, CNT bundles are used to provide higher efficiency.

As the required communication range increases, it may be possible to amplify the transmission power using a number of nanotubes in parallel. In addition to amplifying the power, an antenna array also enables directionality properties of transmission, which leads to less power consumption when point-to-point communication is needed. CNT antennas may be incorporated into available micro or nanoradio circuitries to provide greater efficiency in the size of the overall system volume. In, nickel-zinc batteries having a footprint of 0.02 cm 2 and 0.555 mW h/cm2 of energy supply are manufactured, and their open circuit voltage ranges from 1.7 V to 1.8 V. In, micro-battery arrays with nanoscale anodes and cathodes are introduced using commercially available nanomaterials with extremely small diameter size on the order of nanometers. The capacity of these battery arrays ranges from 3 mAh/g to 18 mAh/g, with 1.5-2 V nominal voltage. Consequently, current technologies may support nanoscale power sources for the realization of nanoscale communication in CANETs. However, overall power budget analysis, including the energy consumption in the transceiver, memory, and processor units, must be performed.

Nanomemory and Nanoprocessor

In, a nanowire crossbar circuit is used to design a nanoscale memory that operates with 0.5–3.5 V. By switching and setting the resistance of the crossbars, each cross point is used as an active memory cell. Crossbar circuits are also configured as multiplexer and demultiplexer circuits. An 8 × 8 crossbar circuit is inserted into an area of 1 μm2 with a density of 64 Gbits/cm2. In, another addressable nanomemory is designed using aligned carbon nanotubes with cross geometry. Some nanoprocessor designs can also be found in the current literature. In, using semiconductor nanowire blocks, functional processor components are constructed. Nanowire junction arrays are configured to build OR, AND, and NOR logic-gates and to enable simple computations. In, sequential nanomemory and processor with clocked operations are devised. Consequently, nanomemory, nanoprocessor, and nanopower units are feasible to enable required nanoscale communication functionalities in CANETs.