Computer Communications Laboratory, Annual Review 2006, The University of Aizu

Annual Review 2006 > Computer Communications Laboratory

Computer Communications Laboratory


Atsushi Kara Professor	Senro Saito Associate Professor	Pham Tuan Anh Assistant Professor

Current research at the Computer Communications Laboratory (CCL) encompasses:

optical communication technology, in particular, modeling, theoretical analysis and simulation of multiple access optical systems;
architecture design and modeling of computer networks; and
internetworking technologies for security & reliability sensitive applications
e.g. medical and healthcare networks.

We welcome undergraduate and graduate students who are interested in the research of communication networks and their applications.

Refereed Journal Papers

[kara-01:2006]	Y. M. Asem and A. Kara. A new group rekeying algorithm using the combination of secret mask patterns and hash values. IEICE Transactions on Information and Systems, Vol. e89-d(No. 9):pp. 2525.2532, September 2006.
[pham-01:2006]	Anh T. Pham, N. Miki, and H. Yashima. Performance Analysis of 2-D WH/TS OCDM System Using Prime Sequences and a Heterodyne Detection Receiver. pages CD.ROM, Nov.-Dec. 2006.
	This paper proposes a novel two-dimensional wavelength hopping/time spreading (WH/TS) optical code divisionmultiplexing (2-D WH/TS OCDM) system using prime sequences and a heterodyne detection receiver for broadband opticalmultiple access networks (OMAN). The performance of the proposed system is theoretically analyzed taking into accountvarious kinds of noise and interference, including multiple access interference (MAI), optical beating interference( OBI), crosstalk and receiver noise. The prime sequences are used as the signature codes for both wavelength hoppingand time spreading. Both symmetric and over-colored asymmetric systems are considered. Analytical results show thatthe proposed system offers much better performance compared with that of a conventional 2-D WH/TS system usingdirect-detection. As a matter of fact, the OBI is well suppressed in the proposed system resulting in a considerableincrease in the number of supportable users. Moreover, the system’s sensitivity is significantly improved enablingthe proposed system to be a promising candidate for the broadband OMAN deployed using the passive optical network (PON)configuration.
[pham-02:2006]	Anh T. Pham and H. Yashima. Performance Enhancement of 2- D WH/TS OCDM Systems using a Heterodyne Detection Receiver and PPM Signaling. OSA Journal of Optical Networking, page to appear, 2007.
	Two-dimensional wavelength hopping/time spreading (2-D WH/TS) synchronous optical code division multiplexing(OCDM) systems using a heterodyne detection receiver and pulse-position modulation (PPM) signaling are investigated.Prime sequences are used as signature code for both wavelength hopping and time spreading. Performance of the proposedsystems is theoretically analyzed taking into account various kinds of noise and interference, including multipleaccess interference (MAI), optical beating interference (OBI), crosstalk and receiver noise. We also compare theperformance of the proposed systems with the conventional ones using on-off keying (OOK) signaling. Numerical resultsshow the improvement in both number of users and optical power gain with a proper selection of PPM word length M

Refereed Proceeding Papers

[kara-02:2006]	Md. Nurul Islam and A. Kara. Throughput Analysis of SCTP over a Multi-homed Association. In Sixth IEEE International Conference on Computer and Information Technology (CIT’06), pages pp. 110.111, September 2006.
[pham-03:2006]	Anh T. Pham and H. Yashima. Novel 2-D Wavelength Hopping/ Time Spreading OCDM System using Heterodyne Detection Receiver and PPM Signaling. In Proc. of the First IEEE’s International Conference on Communications and Electronics (ICCE 2006), pages 259.263, Hanoi, VIETNAM, Oct. 2006. REV/IEEE/EIC/IEEK.
	We propose and theoretically analyze the performance of two-dimensional wavelengthhopping/ time spreading optical code division multiplexing (2-D WH/TS OCDM) systems usingheterodyne detection receiver and pulse-position modulation (PPM) signaling. The analysis iscarried out taking into account various kinds of noise and interference, including multipleaccess interference (MAI), optical beating interference (OBI), crosstalk and receiver’s noise.We compare the performance of the proposed system with the one using OOK signaling. Numericalresults show the improvement in both number of users and optical power gain. In particular, whenthe PPM signaling with M = 4 is used, we can achieve a more than 6 times increase in the numberof users and an optical power gain of 15 dB in comparison with the conventional system

Unrefereed Papers

[pham-04:2006]

Anh T. Pham and Hiroyuki Yashima. Performance Analysis of 2-D WH/TS OCDM Systems Using Prime Sequences and a Heterodyne Detection Receiver. In IEICE Tech. Rep., volume CS 2006-17. IEICE, IEICE, 5 2006.

Grants

[pham-05:2006]

Anh T. Pham. Grants-in-Aid (Grant No. 18760278) for Encouragement of Young Scientists, awarded by the Japan Society for Promotion of Science, 2006-2008.

Academic Activities

[pham-06:2006]	Anh T. Pham, 2005. Technical reviewer for various IEEE, IPSJ, Elsevier, IASTED journals, transactions and international conferences.
[pham-07:2006]	Anh T. Pham, 2005-2008. Member of the Technical Committee on Telecommunications, IASTED.