Int. J. Communications, Network and System Sciences, 2010, 3, 954-961
doi:10.4236/ijcns.2010.312130 Published Online December 2010 (http://www.SciRP.org/journal/ijcns)
High Capacity Mobile Ad Hoc Network Using THz
Frequency Enhancement
Sawatsakorn Chaiyasoonthorn1, Phongphun Limpaibool2, Somsak Mitatha2, Preecha P. Yupapin3
1Electronics Technology, Faculty of Science, Ramkhamhaeng University, Ba ngkok, Thailand
2Hybrid Computing Research Laboratory, Faculty of Engineering,
King Mongkut’s Institute of Technology Ladkrabang, Bangkok, Thailand
3Nanoscale Science and Engineering Research Alliance (N’SERA), Faculty of Science,
King Mongkut’s Institute of Technology Ladkrabang, Bangk ok, Thailand
Received September 25, 2010; revised October 27, 2010; accepted November 23, 2010
Abstract
We propose a new design of the high channel capacity in Mobile Ad Hoc Network that uses the dense wave-
length division multiplexing wavelength enhancement, in which the increasing in channel capacity and sig-
nal security can be provided. The increasing in number of channel can be obtained by the increasing in
wavelength density, while the security is introduced by the specific wavelength filter, which is operated by
the Ad Hoc node operator and link with other nodes in coverage by dedicated one-to-one in direct or relay
node. The optical communication wavelength enhancement is reviewed. The advantage is that the proposed
system can be implemented and used incorporating with the existed communication link in both infrastruc-
ture-based and Ad Hoc networks wireless network, where the privacy can be provided, which is discussed in
details.
Keywords: Ad Hoc Network, THz Technology, High Capacity Network, Frequency Enhancement
1. Introduction
Wireless communication technology has become a part
of human life, which is recognized as the convenient
tools in the world society. Up to date, the merging com-
munication system has become more realistic and avail-
able. The wireless network, whereas the demand has
been increased rapidly. Generally, the wireless network
communications performed by using radio frequency
electromagnetic wave to share information and resources
between wireless devices; such as mobile terminal,
pocket size PCs, hand-held PCs, laptops, cellular phone,
PDAs, wireless sensors, and satellite receivers. Digital
signal processing (DSP) is ideas of software define ratio
(SDR) [1] mechanism, broadcast message between
transmitter and receiver by broadcast channel. Broadcast
channel is the basic form of communication in all wire-
less system by medium access control (MAC) and
CSMA/CA protocol. The wireless operates by two type
modes are infrastructure-based and Mobile Ad Hoc
Network (MANET). The MANET formed dramatically
through the cooperation and self organizations of mobile
nodes; connect via wireless link, no centralized adminis-
trator and free to move randomly. MANET used IEEE
802.11 standard and CSMA/CA in this standard used to
provide collision avoidance and congestion control. Two
mechanisms for performs in MANET are broadcast pro-
tocol [2-4]; one available ad hoc node attempts to broad-
cast message to all participation nodes by broadcast
mechanisms and routing protocols [5]; search or find
between the pair nodes by some mechanisms such as
DSDV, CGSR, WRP, GSR, OLSR, FSR, LAN-MAR,
HRS, DSR, AODV, TORA, ABR, and SSR. Normally,
MANET link by radio frequency and used a channel for
communicate with other participant nodes in a coverage
area by used CSMA/CA protocol to solve hidden and
expose problems, in other way, these problem can re-
solve by some method such as multichannel communica-
tion [6]. In case out of coverage area, MANET commu-
nicates with other coverage via the relay node, this link is
the platform of multi-hop network. The performance of
communication for Ad Hoc network contain with many
factors such as the bandwidth of channel, number of
node, the velocity of node, and the technique for com-

S. CHAIYASOONTHORN ET AL.
955
munication management. Group [7] and cluster-based [8]
accompany the mobile device such as processors, mem-
ory, and I/O devices. Ad Hoc overlay network [9] is the
virtual network for resources management in Ad hoc
such as dissemination, discovery, or other process. The
hybrid network [10], combine various type of technology
to wireless capability, wire network, wireless network,
GPS, and CDMA [11]. The diversity mechanism [12],
transmit more than one channels by using antenna array
and received best channel for data transmissions. This
research we propose the new dedicate intermediary link
between nodes in MANET system by using the dense
wavelength division multiplexing (DWDM) by point-to-
point fashion. Every MANET communicates together
with participant nodes by direct one-to-one link or by via
relay node with THz antenna [13]. The rest of this paper
is structure as follows. Section 2 revises Operating Prin-
ciple, the light source wavelength enhancement. Section
3 proposed the DWDM Frequency Enhancement for
dedicates Wireless Link. Section 4 is the concussion of
this work and section 6 is an acknowledgement.
2. Frequency Enhancement
Light from a monochromatic light source is launched
into a ring resonator with constant light field amplitude
(E0) and random phase modulation as shown in Figure 1,
which is the combination of terms in attenuation () and
phase( 0

) constants, which results in temporal coher-
ence degradation. Hence, the time dependent input light
field (Ein), without pumping term, can be expressed as
[14]


0
0
L
jt
in
Et Ee
 
 (1)
where L is a propagation distance(waveguide length).
We assume that the nonlinearity of the optical ring
resonator is of the Kerr-type, i.e., the refractive index is
given by
2
02 0,
eff
n
nn nInP
A

 



(2)
where 0 and 2 are the linear and nonlinear refrac-
tive indexes, respectively.
n n
I
and are the optical
intensity and optical power, respectively. The effective
mode core area of the device is given by eff
P
A
. For the
microring and nanoring resonators, the effective mode
core areas range from 0.10 to 0.50 m2 [15]
When a Gaussian pulse is input and propagated within
a fiber ring resonator, the resonant output is formed, thus,
the normalized output of the light field is the ratio be-
tween the output and input fields ( and) in
each roundtrip, which can be expressed as [16]
()
out
Et ()
in
Et

  


22
22
11
11
111 411sin
2
out
in
x
Et
Et xx








 

 



(3)
Equation (3) indicates that a ring resonator in the par-
ticular case is very similar to a Fabry-Perot cavity, which
has an input and output mirror with a field reflectivity,
(1 –), and a fully reflecting mirror.
 is the coupling
coefficient, and


exp 2x  

L
0
represents a roundtrip
loss coefficient, 0 kLn

 and 2
NL eff
n
kL P
A





are
the linear and nonlinear phase shifts, 2k

  is the
wave propagation number in a vacuum. Where L and

are a waveguide length and linear absorption coefficient,
respectively. In this work, the iterative method is intro-
duced to obtain the results as shown in Equation (3),
similarly, when the output field is connected and input
into the other ring resonators.
The input optical field as shown in Equation (1), i.e. a
Gaussian pulse, is input into a nonlinear microring reso-
nator. By using the appropriate parameters, the chaotic
signal is obtained by using Equation (3). To retrieve the
signals from the chaotic noise, we propose to use the
add/drop device with the appropriate parameters. This is
given in details as followings. The optical outputs of a
ring resonator add/drop filter can be given by the Equa-
tions (4) and (5) [16,17].
  


22
112 2
2
121 2
1211cos 1
11 1211cos
L
L
n
t
L
in Ln
ekL e
E
Eee




 
 



 

  kL
(4)
and


22
12
2
121 2
11 1211cos
L
d
L
in Ln
Ee
Eee




 




  kL
(5)

956 S. CHAIYASOONTHORN ET AL.
Figure 1. A schematic of a Gaussian soliton generation system, where Rs: ring radii, 
s: coupling coefficients, Rd: an add/drop
ring radius, Aeff: Effective areas, MRR: Microring resonator, NRR: Nanoring resonator, K42 and K42 are add/drop coupling
coefficients.
where Et and Ed represents the optical fields of the
throughput and drop ports respectively. The transmitted
output can be controlled and obtained by choosing the
suitable coupling ratio of the ring resonator, which is
well derived and described by reference [17]. Where
eff
kn

 represents the propagation constant, eff is
the effective refractive index of the waveguide, and the
circumference of the ring is
n
2LR

, here is the
radius of the ring. When the chaotic noise cancellation
can be managed by using the specific parameters of the
add/drop device, which the required signals at the spe-
cific wavelength band can be filtered and retrieved.
К1and К2 are coupling coefficient of add/drop filters,
R
2
n
k

  is the wave propagation number for in a
vacuum, and the waveguide (ring resonator) loss is  =
0.5 dBmm-1. The fractional coupler intensity loss is  =
0.1. In the case of add/drop device, the nonlinear refrac-
tive index is neglected.
3. High Capacity Ad Hoc Network Using
Wireless Link
MANET is an autonomous node and independent re-
sources management, majority used a channel for link all
nodes by using CSMA/CA to access management. In this
paper, we propose new platform for link wireless node
by using a link per node (1-1), show in Figure 1.
From Figure 2, depict the Ad Hoc link model, (a)
nodes A, B, and C can communicate with all other nodes
or in coverage, in this cast A link to B directly, B link to
C directly, and A link to C by directly. From Figure 2(b),
all nodes not in coverage, node A, B, and C are in cov-
erage, nodes C and D are in coverage, and nodes D, C,
and E are in coverage. From Figure 1(c), show diagram
for link by 1-1 of node A, node A can link to node B
directly, node A can link to node C directly, node A can
link to node B directly, but node A cannot link to nodes
E and F directly due to out of coverage. In this case, we
propose virtual direct link by using relay node, node A
link to node E and F by used relay nodes C and D. Node
A link to node E by using a channel via relay node C
relay node D and in this case node A use four cannel for
link in a time.
From Figures 1 and 3, in principle, light pulse is
sliced to be the discrete signal and amplified within the
first ring, where more signal amplification can be ob-
tained by using the smaller ring device (second ring).
Finally, the required signals can be obtained via a drop
port of the add/drop filter. In operation, an optical field
in the form of Gaussian pulse from a laser source at the
specified center wavelength (frequency) is input into the
system. In practice, the maximum frequency that can be
confined within the optical waveguide has been in-
creased by using the composite of materials known as
meta-materials [18], which is shown that the wavelength
close to few mm (THz region) can be confined within the

S. CHAIYASOONTHORN ET AL.
957
Figure 2. (a) Link 1-1 by direct node, (b) Link 1-1 via relay node, and (c) Diagra m for node A link to all node (B, C, D, E, and
F).
Figure 3. Ad Hoc wireless link model, where Rs: ring radii, 
s: coupling coefficients, Rd: an add/drop ring radius, Aeff: Effec-
tive areas, MRR: Microring resonator, NRR: Nanoring resonator, K42 and K42 are add/drop coupling coefficients.
waveguide. In operation, light pulse is sliced to be the
discrete signal and amplified within the first ring, where
more signal amplification can be obtained by using the
smaller ring device (second ring) as shown in Figure 1.
Finally, the required signals can be obtained via a drop
port of the add/drop filter. An optical field in the form of
Gaussian pulse from a laser source at the specified center
frequency is input into the system. From Figure 3, the
Gaussian pulse with center frequency (f0) at 3.0 THz,
pulse width (Full Width at Half Maximum, FWHM) of

958 S. CHAIYASOONTHORN ET AL.
20 ns, peak power at 2 W is input into the system as
shown in Figure 4(a). The large bandwidth signals can
be seen within the first microring device, and shown in
Figure 4(b). The suitable ring parameters are used, for
instance, ring radii R1 = 15.0 μm, R2 = R3 = 9.0 μm, and
Rd = 50.0 μm. In order to make the system associate with
the practical device [19,20], the selected parameters of
the system are fixed to n0 = 3.34 (InGaAsP/InP), Aeff =
0.50 m2 and 0.25 m2 for a microring and add/drop ring
resonator, respectively,
 = 0.5 dBmm-1,  = 0.1. In this
investigation, the coupling coefficient (kappa,
 ) of the
microring resonator is ranged from 0.10 to 0.96. The
nonlinear refractive index of the microring used is n2 =
2.2 × 10-17 m2/W.
In this case, the attenuation of light propagates within
the system (i.e. wave guided) used is 0.5 dBmm-1. After
light is input into the system, the Gaussian pulse is
chopped (sliced) into a smaller signal spreading over the
spectrum due to the nonlinear effects [16], which is
shown in Figure 4(b). The large bandwidth signal is
generated within the first ring device. In applications, the
specific input or output frequencies can be used and gen-
erated, where the suitable parameters are used and shown
in the figures. The similar manner is as shown in Figures
5-7, where the different parameters are the Rd radii and
coupling coefficients, where the small FSR is obtained.
In Figure 5, results of the THz frequency band with the
center frequency at 3 THz, where (a) the input Gaussian
pulse, (b) the large bandwidth signal, (c) the filtering and
amplifying signals, (d) output frequency band, (e) and
(f )are the drop port signals, (g) and (h)are the through
port signals.
4. Conclusions
We have shown that the multi frequency bands can be
generated by using a Gaussian pulse propagating within
the microring resonator system, which can be simulta-
neous link within a single device and available for the
extended multi switching application with the frequency
relay at the THz band. The Mirroring resonators system
embedded in mobile node to generate bandwidth for
serve two communication styles are direct communica-
tion and multi-hop communication by relay service. This
can be used for wireless network with the existed public
networks or the Ad Hoc network.
Figure 4. Results of the THz frequency band wi th the center frequency at 3THz, where (a) the input Gaussian pulse, (b) the
large bandwidth signal, (c) the filtering and amplifying signals, (d) output frequency band, (e) and (f) are the drop port sig-
nals, (g) and (h) are the through port signals.

S. CHAIYASOONTHORN ET AL.
959
Figure 5. Results of the THz frequency band wi th the center frequency at 3THz, where (a) the input Gaussian pulse, (b) the
large bandwidth signal, (c) the filtering and amplifying signals, (d) output frequency band, (e) and (f) are the drop port sig-
nals, (g) and (h) are the through port signals.
Figure 6. Results of the THz frequency band w ith the center frequency at 3 THz, where (a) the input Gaussian pulse , (b) the
large bandwidth signal, (c) the filtering and amplifying signals, (d) output frequency band, (e) and (f )are the drop port sig-
nals, (g) and (h)are the through port signals.

S. CHAIYASOONTHORN ET AL.
960
Figure 7. Results of the THz frequency band wi th the center frequency at 3THz, where (a) the input Gaussian pulse, (b) the
large bandwidth signal, (c) the filtering and amplifying signals, (d) output frequency band, (e) and (f) are the drop port sig-
nals, (g) and (h) are the through port signals.
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