This letter presents the implementation framework of a video streaming server which uses an optical disk library as a source of media archiving. In order to handle the optical storage subsystem in the framework of disk-based stream service model, we have devised an effective stream scheduling, disk caching, and admission control mechanism. The proposed system has been implemented and its key principles are validated with real experiments.

A term rewriting system which effectively preserves recognizability (EPR-TRS) has good mathematical properties. In this paper, a new subclass of TRSs, layered transducing TRSs (LT-TRSs) is defined and its recognizability preserving property is discussed. The class of LT-TRSs contains some EPR-TRSs, e.g., {f(x)f(g(x))} which do not belong to any of the known decidable subclasses of EPR-TRSs. Bottom-up linear tree transducer, which is a well-known computation model in the tree language theory, is a special case of LT-TRS. We present a sufficient condition for an LT-TRS to be an EPR-TRS. Also reachability and joinability are shown to be decidable for LT-TRSs.

An improved movement-based registration scheme reduces location update cost on conventional movement-based location update scheme but increases uncertainty of the position of a mobile terminal (MT). The effect of this uncertainty of the MT position on the paging cost of the improved movement-based registration scheme is analyzed. We show that the paging cost of the improved movement-based registration scheme in [2] is underestimated, especially for large values of movement threshold. The result shows that the underestimation cannot be ignored.

As multimedia and high-speed traffic become more popular on the Internet, the various traffic requiring different qualities of service (QoS) must co-exist. In addition, classified services based on Diff-Serv (Differentiated Service), MPLS (Multi-Protocol Label Switching), etc., have come into wide use. Today's Internet environment requires routers to perform control mechanisms in order to guarantee various QoSs. In this paper, we propose a smart buffer management scheme for the Internet router that uses hierarchical priority control with port class and flow level. Furthermore, since the proposed scheme must operate at very high speed, we first propose several design policy for high speed operation and the hardware implementation is performed in VHDL code. Implementation results show that the proposed scheme can scale with high-speed link, achieving the maximum rate of 4.0 Gbps by using the 3.5 µm CMOS technology.

Assume that each edge e of a graph G is assigned a list (set) L(e) of colors. Then an edge-coloring of G is called an L-edge-coloring if each edge e of G is colored with a color contained in L(e). It is known that any series-parallel simple graph G has an L-edge-coloring if either (i) |L(e)| max{4,d(v),d(w)} for each edge e=vw or (ii) the maximum degree of G is at most three and |L(e)| 3 for each edge e, where d(v) and d(w) are the degrees of the ends v and w of e, respectively. In this paper we give a linear-time algorithm for finding such an L-edge-coloring of a series-parallel graph G.

Class-based delay differentiation model has been recently proposed as a part of relative differentiated services frameworks, and it is shown that the model can provide delay differentiation without admission control and end-to-end resource reservation. In this paper, however, we observe that there can be inconsistent delay differentiation caused by different size of packets. We propose packet size-based delay differentiation model and show that packet size-based queueing is effective to achieve equal delay within a class and provide consistent delay differentiation between classes through simulations. Simulation results also show that the proposed model improves jitter characteristics of CBR flows.

To support video streaming over the current Internet, a media server usually needs to perform adaptive streaming in combination with congestion control. While existing streaming schemes are mainly designed for particular congestion algorithms and rate shaping techniques, this paper proposes a general buffer-driven adaptive streaming scheme based on control theory. Our scheme can be applied in combination with different congestion control algorithms and different rate shaping (and source coding) techniques. It is also amenable to analysis and easy to implement. Analytical and simulation results show that the proposed scheme gives satisfactory video quality under various Internet conditions while fully utilizing the available network bandwidth.

Many services on the Internet are provided by multiple identical servers in order to improve performance and robustness. The number, the location and the distribution of servers affect the performance and reliability of a service. The server placement is, however, often determined based on the empirical knowledge of the administrators. This paper investigates issues of the server placement in terms of the service performance and the server load. We identify that a server selection mechanism plays an important role in server placement, and thus, evaluate different server selection algorithms. The result shows that it is essential to the robustness of a service to employ a mechanism which distributes service requests to the servers according to the measured response time of each server. As a case study, we evaluate the server selection mechanisms employed by different DNS (Domain Name System) implementations. Then, we show the effects of the different server selection algorithms using root-server measurements taken at different locations around the world.

In recent years, requests for new advanced features, decentralization, and improvements in the forwarding speed, have been made for IX. A new IX architecture using MPLS (Multiple Label Switching) technology (MPLS-IX) is proposed to solve these requirements and rectify the problems. In this paper, a comparison between current IX and MPLS-IX based on router's packet forwarding performance is examined, and the feasibility of MPLS-IX is discussed. Moreover, the QoS requirements to provide IX service are discussed.

The use of fluid Generalized Processor Sharing (GPS) algorithm for integrated service networks has received much attention since early 1990's because of its desirable properties in terms of delay bound and service fairness. Many Packet Fair Queuing (PFQ) algorithms have been developed to approximate GPS. However, owing to the implementation complexity, it is difficult to support a large number of sessions with diverse service rates while maintaining the GPS properties. The grouping architecture has been proposed to dramatically reduce the implementation complexity. However, the grouping architecture can only support a fixed number of service rates, thus causing the problems of granularity, bandwidth fairness, utilization, and immunity of flows. In this paper, we propose a new implementation approach called dual-rate grouping, which can significantly alleviate the above problems. Compared with the grouping architecture, the proposed approach possesses better performance in terms of approximating per session-based PFQ algorithms without increasing the implementation complexity.

Existing research related to RSVP with mobility support has mainly focused on maintaining reservation state along the routing path, which changes continuously with the movements of mobile host (MH), without much overhead and delay. However, problems such as deepening RSVP's inherent scalability problem and requiring significant changes in the existing network infrastructure have not been adequately addressed. In this paper, we propose a new approach, known as Concatenation and Optimization for Reservation Path (CORP), which addresses these issues. In CORP, each BS pre-establishes pseudo reservations to its neighboring BSs in anticipation of the MH's movement. When the MH moves into another wireless cell, the associated pseudo reservation is activated and concatenated to the existing RSVP session to guarantee continuous QoS support. Because a pseudo reservation is recognized as a normal RSVP session by intermediate routers, little change is required in the current Internet environment to support both movements within a single routing domain and between two different routing domains. CORP also dynamically optimizes the extended reservation path to avoid the infinite path extension problem. Multicast addressing is used to further reduce resource consumption in the optimization process. The experimental results of the CORP implementation demonstrate that it significantly reduces the delay and overhead caused by handoffs compared to the case of establishing a new RSVP session. The improvement increases as the distance between the MH and its correspondent host (CH) grows.

In this paper, we propose a Distributed Request based CDMA Reservation ALOHA protocol to support multi-class services, such as voice, data, and videophone services, efficiently in multi-rate transmission cellular systems. The proposed protocol introduces a frame structure composed of an access slot and an transmission slot and an adaptive access permission probability based on the estimated number of contending users for each service, in order to control MAI by limiting the access to slots. It can provide voice service without the voice packet dropping probability through the proposed code assignment scheme, unlike other CDMA/PRMA protocols. The code reservation is allowed for voice and videophone services. The low-rate data service basically uses the remaining codes among the codes reserved for the voice service, but it can also use the codes already assigned to voice calls during the their silent periods to utilize codes efficiently. On the other hand, the high-rate data service uses the codes reserved for itself and the remaining codes among the codes reserved for the videophone service. Using the analytic method based on the Markov-chain subsystem model for each service including the handoff calls in uplink cellular systems, we show that the proposed protocol can guarantee the constant GoS for the handoff calls even with a large number of contending users through the proposed code assignment scheme and the access permission probability. Also, we show that the data services are integrated efficiently on the multi-rate transmission environment.

A new distributed medium access control (MAC) protocol--Soft Reservation Multiple Access with Priority Assignment (SRMA/PA) protocol--is introduced for supporting the integrated services of real-time and non-real-time applications in mobile ad-hoc networks. The SRMA/PA protocol allows the distributed nodes to contend for and reserve time slots with RTS/CTS-like "collision-avoidance" handshake and "soft reservation" mechanism augmented with distributed and dynamic access priority control. The SRMA/PA protocol realizes distributed scheduling for guaranteeing QoS requirements of integrated services and maximizes statistical multiplexing gain. We have demonstrated by simulation studies that the multiplexing gain can be improved significantly without unduly compromising on system complexity. Moreover, we have shown that the proposed back-off mechanism designed for delay-constrained services is useful for further improving utilization of the channel.

G. Huet (1980) showed that a left-linear term-rewriting system (TRS) is Church-Rosser (CR) if P Q for every critical pair < P, Q > where P Q is a parallel reduction from P to Q. This paper shows that Huet's result can be generalized under the assumption that a subsystem K of TRS R (i.e., KR) is CR. That is, we show that R is CR if P K Q for every < P, Q > CP(K,R-K) and P R-K *K*K Q for every < P, Q > CP(R-K,R). Here, CP(R1,R2) is the set of critical pairs obtained from some rule of R1 and one of R2.

We propose and demonstrate a novel method to measure the polarization mode dispersion (PMD) of optical devices. The device under test (DUT) is installed in a fiber laser cavity which can operate at multiwavelength. PMD can be evaluated by the wavelength spacing of the multiwavelength laser output spectrum. In our method, the maximum extrema wavelength is easier to be identified than in the conventional fixed-analyzer (FA) method. We measure the PMD of polarization maintaining fibers (PMFs) and the ITU-T round robin KDD samples.

This paper presents an effective approach for estimating of the load matching conditions for dielectric barrier discharge (DBD) load. By the simulation method proposed here, optimal working frequency and optimal applied voltage for driving of DBD load can be calculated. Estimation results for the DBD ultraviolet generation lamp as a load of series resonant inverter are presented here, together with their evaluations.

In an order-specified multisignature scheme, one can verify not only a set of signers who have signed the message but also its signing order. Though we have seen several schemes with such properties proposed, none of them is given the security proof against active adversaries. The scheme can be easily modified to be an order-specified multisignature scheme, but still has the restriction that the possible signing orders are only ones of the type of serial signing. In this paper, we propose the first order-specified multisignature scheme, which is shown to be secure against adaptive chosen-message insider attacks in the random oracle model, and which allows the signing orders to form like any series-parallel graphs. The security is shown by using ID-reduction technique, which reduces the security of multisignature schemes to those of multi-round identification schemes. Furthermore, we discuss the efficiency of the proposed scheme and the upper bound of the possible number of participating signers.

There is a strong demand to expand captioned broadcasting for TV news programs in Japan. However, keyboard entry of captioned manuscripts for news program cannot keep pace with the speed of speech, because in the case of Japanese it takes time to select the correct characters from among homonyms. In order to implement simultaneous subtitled broadcasting for Japanese news programs, a simultaneous subtitling system by speech recognition has been developed. This system consists of a real-time speech recognition system to handle broadcast news transcription and a recognition-error correction system that manually corrects mistakes in the recognition result with short delay time. NHK started simultaneous subtitled broadcasting for the news program "News 7" on the evening of March 27, 2000.

This paper presents a beamspace-time transmit diversity scheme that uses a space-time block code (STBC) and a fixed multi-beam transmit array with low sidelobes for time-domain spreading orthogonal frequency-division multiplexing code-division multiplexing (OFDM-CDM) downlink transmission. The scheme assigns space-time-coded signals to a pair of neighboring beams via closed-loop beam selection. Time-domain spreading provides non-frequency selectivity in each spreading region, which makes it possible for multiple STBCs to share any beam and to be decoded after despreading. Simulation results demonstrated that multiple transmit beams and multiple receive antennas provide large beam gains and/or a high order of diversity gains. In addition, the proposed scheme spatially separates users by beam and thus alleviates multi-user interference.

Interference Cancellation (IC) receivers can be used in CDMA cellular systems to improve the capacity. The IC receivers can be divided into two main categories, Single-User Detectors (SUD) and Multi-User Detectors (MUD). They have different characteristics in terms of intra-cell and inter-cell interference cancellation ability. In this paper we propose two new IC receivers that combines the properties of SUD and MUD receivers. The first one is a Serial IC receiver followed by the Normalized Griffiths' algorithm (SING). The second one is an Integrated Serial IC and Normalized Griffiths' algorithm (iSING). We first compare their basic single-cell performance with the conventional RAKE receiver, the Serial IC and the Normalized Griffiths' Algorithm. Next, we examine their multi-cell performance by doing multi-cell link-level simulations. The results show that even though the Serial IC receiver has good single-cell performance, the proposed receivers have as much as 35-40% higher capacity than the Serial IC receiver in the multi-cell case under the ideal conditions assumed in this paper.