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-01:2005]	Y. M. Asem and A. Kara. A scalable group rekeying scheme using secret mask patterns. International Journal of High Performance Computing and Networking, Vol 3(5/6):346-355, 2005.
[pham-01:2005]	Anh T. Pham and H. Yashima. Performance Analysis of MDSS Code Acquisition Using SLS for Optical CDMA Systems. IEICE Transaction on Communications, E88-B(12):4570-4577, 2005.
	We propose a multiple dwell serial search (MDSS) code acquisition for optical code-division multiple-access (O-CDMA) systems and theoretically analyze its performance. The search/lock strategy (SLS) is used as verification scheme for the multiple dwell detector. The operation of SLS is modeled by finite Markov chain to analyze the performance of the proposed system. Effect of system parameters, such as number of users, threshold and mean photon count per chip, on the performance of the proposed system is investigated. The theoretical result shows that the performance of the proposed system is less sensitive to parameter settings than the conventional single dwell serial search (SDSS) code acquisition system is. In addition, the proposed MDSS code acquisition system offers shorter mean acquisition time than that of conventional SDSS system.
[pham-02:2005]	Anh T. Pham, N. Miki, and H. Yashima. Spectral Amplitude Encoding Optical Code Division Multiplexing System using Heterodyne Detection Receiver for Broadband Optical Multiple Access Networks. OSA Journal of Optical Networking, 4(10):621-631, 2005.
	This paper proposes a spectral amplitude encoding optical code division multiplexing (SAE/OCDM) system using heterodyne detection receiver for broadband optical multiple access networks (OMAN). The performance of the proposed system is theoretically analyzed, taking into account various noise, interferences, including multiple access interference (MAI), crosstalks, optical beating interference (OBI) and receiver's noise. Analytical results show that the proposed system offers significant improvement in terms of receiver sensitivity and system capacity (number of users) compared with conventional direct detection systems. The paper also discusses conditions for the heterodyne detection receiver to work properly in the SAE/OCDM system. In addition, the system performance is analyzed with several signature code sets including msequence, Hadamard and Modified Quadratic Congruence (MQC). It is found that signature code sets with higher weight, such as m-sequence, Hadamard, in preferred in the SAE/OCDM system using heterodyne detection receiver.

Refereed Proceeding Papers

[pham-03:2005]	Anh T. Pham, N. Miki, and H. Yashima. Performance Analysis of SAE/OCDM System using Heterodyne Detection Receiver. In 4th International Conference on Optical Communications and Networks (ICOCN 2005), pages 93-96, Bangkok, Thailand, Dec. 2005. OSA/IEEE/SPIE.
	This paper proposes a spectral amplitude encoding optical code division multiplexing (SAE/OCDM) system using heterodyne detection receiver for optical access networks. The performance of the proposed system is theoretically analyzed, taking into account various noise, interferences, including multiple access interference (MAI), crosstalks, optical beating interference (OBI) and receiver's noise. Analytical results show that the proposed system offers significant improvement in terms of receiver sensitivity and system capacity (number of users) compared with conventional direct detection systems. Moreover, we find that signature code sets with higher weight, such as sequence, Hadamard, in preferred in the SAE/OCDM system using heterodyne detection receiver.
[pham-04:2005]	Anh T. Pham and H. Yashima. Performance Analysis of Multiple Dwell Serial Search Code Acquisition using Search/Lock Strategy for PPM/OPPM OCDMA Systems. In 20th Iternational Technical Conference on Circuits/Systems, Computers and Communications (ITCCSCC 2005), pages 199-204, Jeju, KOREA, Jul. 2005. IEEK/IEICE.
	Multiple dwell serial search (MDSS) code acquisition using Search/Lock strategy (SLS) is proposed for overlapping pulse-position modulation (OPPM) optical CDMA (OCDMA) systems. It is seen that the proposed system offers better performance than the conventional sing dwell serial search (SDSS) in terms of both the required number of training frames an the optimum operation range.
[s-saito-01:2005]	Ashraf Uddin Ahmed, Senro Saito, and Zixue Cheng. Zonebased Traffic Load Balancing to Ensure Quality of Service (QoS) in Distributed Systems. In proc. of the 2005 11th IEEE International Conference on Parallel and Distributed Systems, volume Vol.II, pages 590-594. ICPADS, July 2005.
	The Zone-based routing algorithm is proposed to route the traffic to achieve efficient resource utilization.
[s-saito-02:2005]	Ashraf Uddin Ahmed, Senro Saito, and Zixue Cheng. Zone-based Routing Algorithm for Congestion Control over the Internet. In proceedings of 19th IEEE International Conference on Advance Information Networking and Applications, volume Vol.1, pages 453-458, Tamkang University, Taiwan, March 2005. AINA.
	We proposed zone-based, congestion control algorithm whitch is easy to implement and users do not have to wait if the link or router is congested or broken down.

Grants

[pham-05:2005]	Anh T. Pham. Sasagawa Scientific Research Grant (Grant No. 17-196) for Young Researcher awarded by The Japan Science Society, 2005-2006.
[pham-06:2005]	Anh T. Pham. Publishing Support Grant, awarded by the Research Foundation for the Electro-technology of Chubu, 2005.

Academic Activities

[pham-07:2005]	Anh T. Pham, 2005-2008. Member of the Technical Committee on Telecommunications, IASTED
[pham-08:2005]	Anh T. Pham, 2005. Technical reviewer for IEEE, IPSJ, Elsevier, IASTED journals/transactions & international conferences.

Ph.D and Other Theses

[s-saito-03:2005]	Ashraf Uddin Ahmed. Ph.D. thesis:A Study on a Zone-based Network Flow Model and Its Applications, University of Aizu, 2005. Thesis Advisor: Senro, S
[s-saito-04:2005]	Yasuharu Araki. Master Thesis:Autonomous Path Management Protocol Implementation and Evaluation, University of Aizu, 2005. Thesis Advisor: Senro, S
[s-saito-05:2005]	Masato Ono. Graduation Thesis:Ryuki Observation for Representing of Network Status, University of Aizu, 2005. Thesis Advisor: Senro, S
[s-saito-06:2005]	Syunsuke Niitsuma. Graduation Thesis:Execution Environment of Event Driven Application based on PDM, University of Aizu, 2005. Thesis Advisor: Senro, S
[s-saito-07:2005]	Shoutrou Nozawa. Graduation Thesis:Verification of a Rate Control Scheduling, University of Aizu, 2005. Thesis Advisor: Senro, S
[s-saito-08:2005]	Hiroaki Saimura. AS Multi-path Policy Routing through the Collaboration of IRR, BGP-4 and APM, University of Aizu, 2005. Thesis Advisor: Senro, S

Others

[s-saito-09:2005]	Committee Member, IPSJ's Special Interest Group on Distributed Systems and Internet Management Technology
[s-saito-10:2005]	Editor, Special Issue of IPSJ Journl on DSM

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