Nano-networks For Wireless Communications
Abdul Muhaimin Abdullah
Tutor: Prof. Hywel Morgan
MEng Electronic Enginering
Abstract
Research in nano-networks is an
interesting subject that has only
emerged in the last three years or so.
The nano-network is a new kind of
communication scheme that may rival
traditional communication schemes in
the near future. In this report, the
concept of nano-networks will be
introduced. Several types of nanonetworks will be presented and lastly
the benefits and disadvantages of the
nano-network communication scheme
will be discussed.
1. Introduction
A nano-network is described as an
interconnection of nano-machines in
order to establish communication
between them [1]. The purpose of
communicating
between
nanomachines is so that nano-machines
could work together systematically and
tasks could be distributed. Hence,
more complex works can be completed
since different (or similar) nanomachines, each with their own unique
functions are collaborated in the nanonetwork system.
2. Nano-machines
Nano-machines
are
‘machines’
constructed in the nano-scale (i.e. 1 to
100 nanometers) which can perform a
particular task involving simple
computation, sensing and actuation [2].
Presently, there are nano-machines that
could
perform
non-complicated
functions that have been manufactured,
such as nano-gears [3], or at least
designed theoretically, such as
molecular differential gears and pumps
[4].
There are three approaches to choose
from to develop nano-machines. The
first way is to down-scale existing
‘machines’ such as microelectronics or
micro-electromechanical devices into
the nano-scale [5]. This is often called
the top-down approach. The second
approach is to let molecules assemble
by themselves according to the
molecules’ preferences and tendencies
[6]. This is called the bottom-up
approach. The third way is called the
bio-hybrid approach. In this approach,
existing biological nano-machines
found in the natural world, such as
molecular motors, are used to create
new nano-machines [7].
Currently, there are no efficient ways
to fabricate nano-machines; hence
nano-networks only exist in theory.
However, it is hoped that in the near
future, advanced techniques of
developing nano-machines will emerge
making nano-networks a lot more
relevant and may rival traditional
communication schemes.
It is envisaged that nano-machines
would have some characteristics that
will help make creation of nanonetworks more feasible. It is
anticipated that nano-machines will be
capable to make copies of themselves,
can move around freely, can assemble
themselves without external force (i.e.
the bottom up approach), are selfcontained i.e. each nano-machine
contains the instructions that are
needed to operate, and lastly they are
able
to
communicate
among
themselves.
3. Molecular Communication
There are several ways that can be
considered to communicate between
nano-machines in order to create a
nano-network. It can be done nanomechanically,
acoustically,
electromagnetically or chemically [8].
By comparing the different means of
communication, a chemical approach
to communicate between nanomachines looks hopeful. It is called
molecular communication and its
development is inspired by the biohybrid approach of creating nanomachines. The concept of molecular
communication is that we can
communicate between nano-machines
by sending information through the use
of molecules. These molecules would
be encoded with information, and then
be sent from one nano-machine to
another.
Molecular communication is preferred
mainly because of two factors. Firstly,
it is infeasible to miniaturize devices
used in acoustic and electromagnetic
communication in the nano-scale.
Secondly, transmitters and receivers in
molecular communication do not need
to be in direct contact, whereas in
nano-mechanical communication this
is vital.
Briefly,
a
typical
molecular
communication process will be
described. There are five components
involved in molecular communication:
the transmitter nano-machine, the
receiver nano-machine, the message
that is to be transmitted (which is
encoded onto molecules), the carrier
that carries the message, and the
medium. Initially, the transmitter
encodes the message onto molecules
by modifying the molecules through
chemical reactions. The transmitter
then may discharge the message
encoded molecule into the medium
directly, or attach it to a carrier and
then releases it into the medium. The
message will be transported through
the medium until it reaches the
receiver. Finally, the receiver receives
the molecule and decodes it.
4. Different Implementations
Molecular Communication
of
Molecular communication can be
divided into three broad categories.
They are the short-range techniques,
medium-range techniques and longrange
techniques.
Short-range
techniques cover from a few
nanometres to micrometres. Mediumrange covers the micrometre range to
millimetres, while the long-range
techniques start from the millimetre
range to several metres [10].
There are several ways that have been
proposed for each of the three
categories. For short-range molecular
communication, it can be done in two
ways: molecular motors and calcium
signalling. In the medium-range, two
techniques are put forward: flagellated
bacteria and nano-motors. Lastly, there
are five ways proposed for long-range
molecular communication which are
divided into two groups. The first
group is wireless long-range molecular
communication which consists of three
techniques: pheromones, spores/pollen,
and light transduction. The other two
are wired long-range techniques: axons
and capillaries. All in all, there are nine
techniques that have been proposed to
communicate between nano-machines.
Each of these techniques will be
discussed in subsequent sections.
4.1 Molecular motors [1]
Molecular
communication
using
molecular motors is one way to
communicate between nano-machines.
Its concept is simple. A transmitter
nano-machine and a receiver nanomachine are connected together by
molecular rails called microtubules.
Then, a molecular motor e.g. dynein
will move from the transmitter to the
receiver along the molecular rails,
acting as a carrier to transport a
molecule that has been encoded with
information.
Since this scheme restricts the sending
of information encoded molecules
between one transmitter and one
receiver only, it is comparable to a
point-to-point
communication
in
traditional communication networks
i.e. a unicast system. A multicast
system could be implemented, but
there must be more molecular rails
connecting the transmitter to other
receivers and the transmitter must be
able to produce and release molecules
that contain the same kind of data to
different receivers. Figure 1 shows the
working of a molecular motor
communication system.
Figure 1. Molecular communication
using molecular motors [1]
4.2 Calcium signalling [1]
Molecular
communication
using
calcium signalling is another shortrange category. Here the message or
the information is stored as
concentration of calcium ions (Ca2+),
rather than encoding the message into
molecules as was done in molecular
communication based on molecular
motors. There are two distinct ways of
using calcium signalling to transmit
information from one nano-machine to
another. One is called the direct access
scenario, while the other is called the
indirect access scenario.
In the direct access scenario (Figure
2a), nano-machines are in direct
contact to each other. Hence,
information would be transmitted in
the form of Ca2+ concentration from
the transmitter nano-machine through
neighbouring nano-machines until it
reaches the intended receiver nanomachine. In the indirect access
scenario (Figure 2b), nano-machines
are far apart from each other, without
direct
contact.
Hence,
the
concentration of Ca2+ that represents
the information would be released into
the medium and governed by
Brownian motion to propagate from
the transmitter to the receiver. In both
scenarios, upon arrival at the receiver,
the Ca2+ concentration would be
decoded in order to read the
information.
This scheme is more similar to a
broadcast network in traditional
communication. This is because all
nearby nano-machines would be able
to receive the message sent by the
same transmitter nano-machine since
information is sent as calcium ion
concentration. This allows a more
flexible communication approach then
molecular
communication
using
molecular motors.
inserted into the bacteria and then is
released into the medium. The bacteria
would follow its natural instincts and
will propagate to the receiver that it is
attracted to. The receiver would then
translate the DNA message.
The DNA here can be used to represent
various types of information in
wireless
communications.
For
example, the ‘DNA’ here can represent
the ‘spreading codes’ in a CDMA
system.
4.4 Catalytic nano-motors [10]
Figure 2. Calcium signalling using (a)
the direct access and (b) the indirect
access [1]
4.3 Flagellated Bacteria [10]
Flagellated bacteria and catalytic nanomotors are two ways proposed to
communicate between nano-machines
at a molecular level in the medium
range i.e. from micrometres to
millimetres. These two techniques
differ
from
their
short-range
counterpart such that instead of using
molecules or molecule concentration
as messages, they use DNA sequences
to represent information.
The first proposed method is to use
flagellated
bacteria.
Flagellated
bacteria, such as E. coli, are bacteria
which has flagella on them, allowing
them to move freely. In this molecular
communication
technique,
these
bacteria would be used to act as
carriers to transmit messages in the
form of DNA from a transmitter nanomachine to a receiver nano-machine.
The whole process is as follows:
Specific bacteria that would only be
attracted to specific receivers are
chosen. Next, the DNA information is
The second medium-range molecular
communication technique is by using
catalytic nano-motors. These nanomotors are made out of nano-rods. A
nano-rod is a rod in the range of
nanometres, which is a combination of
metallic molecules such as platinum
(Pt) or gold (Au). If the combination of
these metals is correct, they can move
on their own when they are submerged
in Hydrogen Peroxide (H2O2) as
shown in Figure 3.
There are two ways to control the
propagation of these nano-motors. By
adding nickel (Ni) to the rods, the
movement of the nano-rod could be
controlled magnetically. The other way
is to build a raft of nano-rods.
Receptors are put onto some part the
raft, and the receiver nano-machine
would have inhibitor particles that
attract the receptors on the raft of
nano-rods. So, some parts of the raft
would move towards the nano-machine
receiver, directing the whole raft
towards it.
Hence, the communication process is
done in the following steps: The nanomotors would be loaded with DNA as
messages using methods reported in
[11]. The nano-motors would be
released to propagate either by
magnetic control or by building nanorod rafts. Eventually the nano-motors
would reach the receiver and the DNA
message would be decoded.
Figure 3. A Pt-Ni-Au-Ni-Au nanomotor in hydrogen peroxide, H2O2 [10]
4.5 Pheromones [1, 12]
As stated above, there are five ways
that are proposed for long-range
molecular communication. They are
divided into two groups: wireless and
wired communication. Pheromones
come under the wireless long-range
molecular communication group.
In the biological world, pheromones
are used to communicate between
members of the same species such as
ants, bees, butterflies etc. Each
pheromone type corresponds to a
unique species and a precise message.
This characteristic of pheromones is
called pheromone diversity and would
be very useful if implemented in nanomachine
communication.
Noninterfering channels could be created
since every nano-machine would
produce unique sets of pheromones.
Another approach that could be taken
is to mix up all the pheromones
together to create a new diverse
alphabet for information. Either
approach could be taken, or both could
be used together.
The
transmission
scheme
of
pheromones is as follows: specific sets
of pheromones are transmitted by the
transmitter nano-machine. Pheromones
are left to spread by way of molecular
diffusion until it reaches the receiver
nano-machine, where the message
would be decoded. Figure 4 shows the
concept
of
how
molecular
communication using pheromones
would work.
Figure 4. Molecular communication
using pheromones [1]
4.6 Light transduction [12]
Light transduction is another method
proposed for wireless long-range
molecular communication. It involves
converting short-range molecular
information
(such
as
calcium
signalling) to optical signals and vice
versa.
The following is the description of
how the system works. Firstly, shortrange
molecular
communication
techniques would be used to send
molecular
information
from
a
transmitter to an M-O (molecular to
optical) transceiver which will convert
the information into an optical signal.
The optical signal would propagate
through the optical system to O-M
(optical to molecular) transceiver that
is nearest to the intended receiver. At
the O-M transceiver, the signal would
be converted back to molecular
information and eventually sent to the
intended receiver by way of shortrange
molecular
communication
schemes.
There are two ways proposed to
convert molecular information to
optical signals, the first is by using
fluorescent
proteins.
Fluorescent
proteins are molecules composed of
amino acids that fluoresce when
exposed to a particular wavelength. So,
fluorescent proteins would be used at
the M-O transceiver to sense the
presence of a molecular signal and
emit a laser signal through the optical
system that corresponds to the
molecular signal. The second way is to
use Molecular Organic Light Emitting
Diode (MOLED). MOLEDs are
semiconductors that can convert
molecular signals to optical. In
principle, they are designed by
downscaling LEDs in the nano-scale.
[13]
To convert the optical signal back to
molecular information, another two
ways are proposed: to use molecular
wires [14] and molecular switches
[15]. These two ways would convert
optical signals to electrons. The
electrons would then be converted to
molecular information through the
synapse process. Figure 5 shows the
light transduction scheme.
However, there are some differences
between
pollen/spores
and
pheromones. Firstly, pollen/spores are
larger than pheromones, so they do not
propagate by means of molecular
diffusion. Secondly, pollen/spores are
chemically
more
robust
then
pheromones, hence they would not be
modified by encountering external
chemical compounds. Lastly, instead
of particle diversity, DNA of
pollen/spores could be manipulated to
represent messages. This then would
be similar to molecular communication
using flagellated bacteria or catalytic
nano-motors.
Nevertheless, the transmission of
pollen/spores is quite the same as
pheromones. The transmitter nanomachine would release pollen/spores
using either the property of particle
diversity or DNA as messages. Next,
the pollen/spores would propagate to
the intended receiver which will then
translate the message into useful
information.
4.8 Axons [12]
Figure 5.
Scheme of molecular
communication
using
light
transduction [12]
For wired long-range molecular
communication, there are two methods
proposed: axons and capillaries. Here
the use of axons will be discussed.
Axons are slender projection of
neurons in animals and humans.
Electrical signals travel in axons,
which are called action potentials.
4.7 Pollen/Spores [12]
Long-range molecular communication
by pollen/spores acts similar to
molecular
communication
using
pheromones. It is a wireless molecular
communication and pollen/spores have
particle diversity like pheromones as
well. This property offers a variety of
features to the encoding process since
only certain receivers could understand
certain pollen or spores.
This concept could be used in
association with short-range molecular
communication networks. Message
obtained
from
short-range
communication would be transformed
into action potentials by the synapse
process. The action potential would
then travel through axons, transform
back to molecular information by the
synapse process and continue to
propagate until it reaches its intended
receiver.
it will decode the message in the
hormones.
Some advantages of using this
approach are as follows. Firstly, axons
are long in length; hence long-range
molecular communication could be
achieved [16]. Secondly, action
potentials move at very high speed
[17]. Thirdly, the action potential
signal does not weaken as it travels
along the axon [16]. Lastly, since
actions potentials are electrical signal,
they could be used with proper
semiconductor
receivers
and
transmitters.
5. Discussions
4.9 Capillaries [12]
The last molecular communication
method and the second method for
wired long-range communication is the
use of capillaries. Capillaries are the
smallest blood vessels in the human
and animal body. To transmit the
message, it will be encoded in the form
of hormones.
Hormones could be encoded as
messages in two ways. The first way is
to embed the message as hormone
concentration, the same way how
calcium signalling is implemented.
Another way is to use different kinds
of hormones to represent different kind
of messages. Similar to pheromones,
there are many kinds of hormones and
each hormone has a unique receptor.
Hence, the transmitter nano-machine
would choose specific hormones
according to the message to be
transmitted and release it into the
capillaries. A pumping mechanism
[18] would be implemented so that the
hormone would propagate, governed
by fluid mechanics, until it reachs the
receiver nano-machine. The receiver
would verify whether the the proper
hormone is transmitted or not, and if so
The theory behind nano-networks has
been briefly described. Overall, it is a
very interesting subject and we look
forward to the results of further
research in the future. In this section,
specifically from a telecommunication
point of view, we would firstly discuss
their disadvantages and some of the
concerns that revolve around current
nano-network technology as well as
suggestion
to
improve
those
disadvantages; secondly we would
evaluate its advantages and how nanonetworks
would
help
improve
telecommunications in the future.
5.1 Disadvantages of Nano-networks
and
Some
Suggestions
for
Improvement
One major concern about nanonetworks is the difficulty of
transferring speech through molecular
communication. This is because
certain molecular communication
techniques are inherently slower than
traditional communication. This is due
to the use of molecules as information
carriers in molecular communication,
while traditional communication may
use optical or electromagnetic signals
to transmit information. However,
some of the molecular communication
methods can offer fast speeds of
transmission such as using light
transduction or action potential in
axons.
Another disadvantage of current nanonetwork technology is the lack of
robustness in the transmission scheme
i.e. the unreliability of transmitting
information from one end to another,
especially
wireless
molecular
communication. This is because
molecular communication techniques
could be affected heavily by medium
conditions, while this does not really
hold in traditional communication
schemes. Hence there is a chance for a
message to not reach its intended
destination. One way to solve this
problem is to model transmission using
molecular
communication
mathematically in order to know how
each molecular communication would
exactly behave. Some mathematical
models have already been published
[19, 12] but a thorough research should
be done to address this issue.
The third concern is the need to
convert digital information into
molecular information. This means
that we would like to translate
information in binary numbers into
molecules or molecule concentration.
In [20], one way to represent bit ‘1’
and bit ‘0’ has been explained. Set the
receiver nano-machine to receive a
specific concentration of molecules or
ions, let say S. If the concentration of
the ions received is less than S, then
the receiver decodes it as bit ‘0’, and if
it is larger than S then bit ‘1’. Other
methods could be proposed as well.
Anyhow, everything will depend on
how further studies into nano-networks
turn up. We need to wait until fully
working nano-machines are developed
before actual outcome of nano-network
implementation could be predicted.
5.2 Advantages of Nano-networks
Only two advantages of nano-networks
could be envisioned with respect to
implementing
nano-networks
in
telecommunication. One advantage of
applying
nano-networks
in
telecommunication is that we could
increase
coverage
of
mobile
communication. This could be
achieved by dispersing numerous
nano-machines in areas which has
small coverage. This will enable
communication in those kinds of areas
without the need of big transceivers.
Internet access would also be
independent of telephone lines and
eventually be truly ‘wireless’.
Another advantage of using nanonetworks for wireless communication
is they consume less power than
traditional communication schemes.
This could be achieved if nanomachines are distributed close enough
to each other. By reducing the distance
between nano-machines, we could
reduce the path loss. This is similar to
the concept of wireless sensor
networks where each sensor can be
powered by battery since the sensors
are relatively near to each other.
6. Conclusion
In this report, we have tried to
introduce and describe the concept of
nano-networks which is a very
interesting subject indeed. The
communication scheme offered by
nano-networks is a new kind of
communication system, different from
traditional communications. In theory,
if nano-networks could be formed, it
would enable us to do things
differently and achieve what currently
is impossible. We have tried to
evaluate nano-networks in the area of
telecommunication and have found
that even though at present nothing
could be used to improve current
telecommunication technologies, given
time, nano-networks can work and will
prove to be a benefit to mankind.
References
[1] I. F. Akyildiz, F. Brunetti, and C.
Blazquez, “NanoNetworking: A New
Communication Paradigm,” Computer
Networks (Elsevier) Journal, Vol. 52,
pp. 2260-2279, August, 2008.
[2] T. Suda, M. Moore, T. Nakano, R.
Egashira, A. Enomoto, “Exploratory
research on molecular communication
between
nanomachines,”
in:
Proceedings
of
Genetic
and
Evolutionary Computation Conference
(GECCO’05), June 2005.
[3] Y.J. Yun, C.S. Ah, S. Kim, W.S.
Yun,
B.C.
Park,
D.H.
Ha,
“Manipulation of freestanding Au
nanogears using an atomic force
microscope,” Nanotechnology 18
(November) (2007).
[4] C. Peterson, “Taking technology to
the molecular level,” IEEE Computer
33 (January) (2000) 46–53.
[5] H. Goldstein, “The race to the
bottom [consumer nanodevice],” IEEE
Spectrum, vol. 42, no. 3, pp. 32–39,
March 2005.
[6] K. Drexler, “Nanosystems: molecular
machinery,
manufacturing,
and
Computation,” New York: John Wiley and
Sons, 1992.
[7] E. Drexler, C. Peterson, G.
Pergamit, and S. Brand, “Unbounding
the future: the nanotechnology
revolution,” 1991.
[8] R.A. Freitas, Nanomedicine,
Volume I: Basic Capabilities. Landes
Biosience, 1999.
[9] S. Hiyama, Y. Moritani, T. Suda,
R. Egashira, A. Enomoto, M. Moore,
T.
Nakano,
“Molecular
communication,” in: Proceedings of
the NSTI Nanotechnology Conference,
October 2005.
[10] M. Gregori, and I. F. Akyildiz, “A
New NanoNetwork Architecture using
Flagellated Bacteria and Catalytic
Nanomotors,” IEEE JSAC (Journal of
Selected Areas in Communications),
Vol. 28, No. 4, pp. 612-619, May
2010.
[11] A. K. Salem, P. C. Searson, and
K. W. Leong, “Multifunctional
nanorods for gene delivery,” Nat
Mater, vol. 2, no. 10, pp. 668–671,
September 2003.
[12] Gine, L. P. and Akyildiz, I. F.,
“Molecular Communication Options
for Long range nanonetworks,”
Computer Networks (Elsevier) Journal,
Vol. 53, No. 16, pp. 2753-2766,
August 2009.
[13] L. Brus, “Chemistry and physics
of semiconductor nanocrystals,” in:
The 37th Middle Atlantic Regional
Meeting, 2005.
[14] R.W. Wagner, J.S. Lindsey, “A
molecular photonic wire,” Journal of
the American Chemical Society
(1994).
[15] S. Crosson, K. Moffat,
“Photoexcited structure of a plant
photoreceptor domain reveals a light
driven molecular switch,” The Plant
Cell (2002).
[16] Encyclopedia Britannica 2008,
“axon,” Viewed on 1st October 2010,
at Encyclopedia Britannica Online:
<http://www.britannica.com/EBcheck
d/topic/46342/axon>.
[17] J.B. Hursh, “Conduction velocity
and diameter of nerve fibers,”
American Journal of Physiology
(1939).
[18] P.K. Dasgupta, S. Liu,
“Electroosmosis: a reliable fluid
propulsion system for flow injection
analysis,”
Analytical
Chemistry
(1994).
[19] M. Pierobon and I. F. Akyildiz,
“A physical end-to-end model for
molecular
communication
in
nanonetworks,” IEEE JSAC (Journal
of Selected Areas in Communications),
Vol. 28, No. 4, pp. 602-611, May
2010.
[20] N. Roca Lacasa and I. F.
Akyildiz, “Modeling the Molecular
Communication
Nanonetworks,”
Universitat Politècnica de Catalunya
(2009).