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Associate Professor |
Assistant Professor |
Assistant Professor |
Visiting Researcher |
- Optical communication technology, in particular, modeling,
theoretical analysis and simulation of multiple access optical systems;
- New-generation communication network research: architecture design, survivability
and protection methods;
- Architecture design and modeling of computer networks; and
- Internetworking technologies for security & reliability sensitive applications
e.g. medical and healthcare networks.
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Current research at the Computer Communications Laboratory (CCL) encompasses
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Refereed Journal Papers
| [pham-01:2009] |
Ngoc T. Dang, Anh T. Pham, and Zixue Cheng. Impact of GVD on the
Performance of 2-D WH/TS OCDMA Systems using Heterodyne Detection
Receiver. IEICE Trans. on. Fundamentals, E92-A(4):1182 E191, 04 2009. |
| In this paper, a novel model of Gaussian pulse propagation in optical fiber is proposed
to comprehensively analyze the impact of Group Velocity Dispersion (GVD)
on the performance of two-dimensional wavelength hopping/time spreading optical
code division multiple access (2-D WH/TS OCDMA) systems. In addition, many
noise and interferences, including multiple access interference (MAI), optical beating
interference (OBI), and receiver’s noise are included in the analysis. Besides, we
propose to use the heterodyne detection receiver so that the receiver’s sensitivity can
be improved. Analytical results show that, under the impact of GVD, the number
of supportable users is extremely decreased and the maximum transmission length
(i.e. the length at which BER 10∁E can be maintained) is remarkably shortened in
the case of normal single mode fiber (ITU-T G.652) is used. The main factor that
limits the system performance is time skewing. In addition, we show how the impact
of GVD is relieved by dispersion-shifted fiber (ITU-T G.653). For example, a system
with 321 Gbit/s users can achieve a maximum transmission length of 111 km when
transmitted optical power per bit is -5 dBm. |
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| [pham-02:2009] |
Anh T. Pham Ngoc T. Dang and Zixue Cheng. Performance Analysis of
Spectral Amplitude Encoding OCDM Systems over Linear Dispersive Optical
Channel. IEEE/OSA Journal of Optical Communications and Networking,
1(6):521 E29, 11 2009. |
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We propose a new model of pulse propagation over a linear dispersive optical channel
and use this model to comprehensively analyze the performance of spectral amplitude
encoding optical code-division multiplexing (SAE/OCDM) systems under the impact
of group velocity dispersion (GVD). We quantitatively discuss the impact of GVD
on various aspects of SAE/OCDM system performance, including the number of
supportable users and the maximum transmission length and power penalty. We
also investigate the system performance with several types of optical fibers, such
as single-mode fiber (SMF), dispersion-shifted fiber (DSF), and nonzero DSF. In
addition, we discuss techniques to compensate for GVD so that the performance of
SAE/OCDM systems can be improved. |
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| [pham-03:2008] |
Anh T. Pham Ngoc T. Dang and Zixue Cheng. Beat Noise Cancellation
in 2-D Optical Code-Division Multiple-Access Systems using Optical Hardlimiter
Array. IEICE Trans. on Communications, Special Section on Optical
Access Technologies, E93-B(2):289 E92, 2 2010. |
| We analyze the beat noise cancellation in two-dimensional optical code-division
multiple-access (2-D OCDMA) systems using an optical hard-limiter (OHL) array.
The Gaussian shape of optical pulse is assumed and the impact of pulse propagation
is considered. We also take into account the receiver noise and multiple access
interference (MAI) in the analysis. The numerical results show that, when OHL
array is employed, the system performance is greatly improved compared with the cases without OHL array. Also, parameters needed for practical system design are
comprehensively analyzed. |
Refereed Proceeding Papers
| [pham-04:2009] |
Ngoc T. Dang and Anh T. Pham. FWM Impairment in Multiwavelength
Optical Code-division Multiplexing Systems. In Proc. of the Australian
Telecommunication Networks and Applications Conference (ATNAC
2009), Canberra, Australia, Nov. 2009. University of New South Wales, pages
1 E, Digital Object Identifier: 10.1109/ATNAC.2009.5464786, IEEE Xplore. |
| This paper comprehensively analyzes the impact of four wave mixing (FWM) on the
performance of multiwavelength optical code-division multiplexing (MW-OCDM) systems.
The impact of FWM on various aspects of MW-OCDM system performance,
including bit error rate (BER), the number of users, and power penalty, is quantitatively
discussed with several types of optical fibers such as single mode fiber (SMF),
dispersion-shifted fiber (DSF), and non-zero DSF considering different frequency spacings.
We find that the operational range of optical power is strictly limited under the
impact of FMW. For example, it is about 6 dB in the case of spectral amplitude
encoding OCDM systems using MQC code (132, 12, 1) and SMF. Also, the impact
of FWM can be relieved so as to extend the operational power range by using two
dimensional (2-D) codes (especially when different time-spreading patterns are used)
or increasing the frequency spacing. |
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| [pham-05:2009] |
Ngoc T. Dang and Anh T. Pham. Impact of Four Wave Mixing on
2-D OCDM Systems. In Proc. of the IEEE/LEOS Summer Topical Meeting,
number Digital Object Identifier: 10.1109/LEOSST.2009.5226236, pages 29 E30, Newport Beach, CA, USA, 7 2009. IEEE Photonics, IEEE Xplore. |
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This paper theoretically analyzed the impact of FWM on 2-D OCDM system performance
considering various noises, interferences, and system’s parameters. Specifically,
the impact on the operational power range, power penalty is quantitatively analyzed
and discussed. |
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| [pham-06:2009] |
Ngoc T. Dang and Anh T. Pham. Beat Noise Cancellation in 2-D
OCDMA Systems using Optical Hard-limiter Array. In Proc. of the Int’l
Conference on Advanced Technologies for Communications (ATC/REV 2009),
number Digital Object Identifier: 10.1109/ATC.2009.5349255, pages 121 E24,
Haiphong, Vietnam, 10 2009. IEEE Xplore. |
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We comprehensively investigate beat noise cancellation in 2-D OCDMA systems using
OHL array considering the real shape of optical pulse. The receiver’s noises and
multiple access interference (MAI) as well as the impact of pulse propagation are all
taken into account. The numerical results show that, when OHL array is employed,
the performance of 2-D OCDMA systems is much improved compared with the other
cases of without OHL array. In addition, the 2-D OCDMA systems using OHL array
can meet the requirements of the optical access networks in both number of users and
transmission length. For example, with the average transmitted power per chip is -12
dBm, the system can support 30 users at bit rate 1 Gbit/s and maximum transmission length of 33 km. Other necessary parameters for practical system design also can be
found in this paper including required transmitted power and optimum threshold. |
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| [pham-07:2009] |
Tu A. Luu, Ngoc T. Dang, and Anh T. Pham. Performance Analysis
of Optical Atmospheric Turbo-Coded CDMA Systems with PPM Signaling.
In Proc. of the 8th Asia-Pacific Symposium on Information and Telecommunication
Technologies, Sarawak, Malaysia, June 2010. IEICE Comm. Society,
pages 1 E, IEICE. |
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This paper proposes Turbo code for optical atmospheric 2-dimensional (2-D) CDMA
systems using pulse-position modulation (PPM) signaling. The system performance
is theoretically analyzed and the upper bound of bit-error rate (BER) is derived considering
the impact of scintillation. The analysis also takes into account various types
of interferences and noises such as multiple access interference (MAI), optical beating
interference (OBI), and receiver noise. It is shown that system performance is significantly
improved when Turbo codes is employed. In particular, the use of Turbo code
results in a power gain of 3.5 dB at the BER = 10∁E, the supportable number of users
is also increased. |
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| [t-huang-01:2009] |
Zixue Cheng, Mizuo Kansen, and Tongjun Huang. Troublesome Detectable
Context-aware Services based on Game-theory. In The 2nd IEEE
International Conference on Ubi-media Computing (U-Media 2009), Taipei,
Taiwan., December 2009. Tamkang University. |
|
With rapid progress on ubiquitous technologies, various services become available at
anytime and anywhere. One of hot topics in ubiquitous computing is context-aware
services, which provide the services at proper time and proper place, in a proper way
personalized to a user. However, there may be conflicts of services among users whose
contexts are overlapped. Moreover, a context-aware service convenient for a user may
cause another user ’s unpleasantness even troublesome. In this paper, we consider
the relations between contexts of different users. A mechanism consisting of multiagents,
to find and reduce the unpleasantness of users due to context-aware services
is constructed based on game-theory. |
Grants
| [s-saito-01:2009] |
T. Hayashi. Ministry of Education Scientific Research Fund, 2008-2009. |
Academic Activities
| [pham-08:2009] |
Anh T. Pham, 2010. Technical reviewer for various IEEE, IEICE journals/transactions & international conferences |
| [pham-09:2009] |
Anh T. Pham, 2010. Technical Program Committee member of: ICCE 2010, SoICT 2010 and ICIS 2010 |
Ph.D, Master and Graduation Theses
| [pham-10:2009] |
Yuta Masuda. Graduation Thesis: Performance Improvement of Optical
Atmospheric CDMA Systems Using Convolutional Codes, University of Aizu,
03 2009. Thesis Advisor: Anh T. Pham |
| [s-saito-02:2009] |
J. Sugawara. Master thesis: A Management of inter-domain Fulfillment
Information and Control of Fulfillment, University of Aizu, 2009. Thesis Advisor: S. Saito |
| [s-saito-03:2009] |
JR. Haneda. Master thesis: A Rate Control System based on the Quality
fulfillment Route of the Internet, University of Aizu, 2009. Thesis Advisor: S. Saito |
| [s-saito-04:2009] |
T. Yanagida. Graduation Thesis: The Ryuki Observation System providing
the Fullfillment Service status, University of Aizu, 2009. Thesis Advisor: S. Saito |
| [s-saito-05:2009] |
M. Egawa. Graduation Thesis: SoS Fulfillment Information System
based on Ryuki Observation System, University of Aizu, 2009. Thesis Advisor: S. Saito |
| [s-saito-06:2009] |
K. Inomata. Graduation Thesis: A Browsing System for the Internet
Ryuki Information, University of Aizu, 2009. Thesis Advisor: S. Saito |
| [s-saito-07:2009] |
M. Sato. Graduation Thesis: The Distributed Ryuki Information Management
System for the Ryuki Browsing, University of Aizu, 2009. Thesis Advisor: S. Saito |
| [s-saito-08:2009] |
T. Sano. Graduation Thesis: A QoS Fulfillment Modeling using AS
Multi-path for Rate Control, University of Aizu, 2009. Thesis Advisor: S. Saito |
| [s-saito-09:2009] |
D. Sugimoto. Graduation Thesis: Dynamic Collection System of the
AS path status for the Domain Routing, University of Aizu, 2009. Thesis Advisor: S. Saito |
