Chiung-Shien Wu

Some routing problems on broadband ISDN

Abstract In this paper, three related virtual channel routing problems on Broadband ISDN are investigated and shown to be NP-complete. A distributed routing heuristic is proposed to reduce the call blocking rate while preserving a fast call setup time. Various traffic patterns and network topologies are employed to evaluate the performance of the proposed heuristic by simulations. Two existing famous routing schemes are also applied for comparison. The simulation results show that the proposed heuristic performs better in most cases than the other two schemes.

Extended baseline architecture for nonblocking photonic switching

A new switch architecture called extended baseline networks (EBN) is proposed for nonblocking photonic switching. This switch is a space-division multistage network using 2/spl times/2 optical switch elements which may be directional couplers fabricated on titanium diffused lithium niobate (Ti:LiNbO/sub 3/) substrates. A recursive definition for the proposed architecture is presented. Some properties including the number of switch elements required, blocking characteristics, number of crossovers, system attenuation, and signal-to-noise ratio (SNR) are derived and analyzed. Most of the characteristics are shown to be better than those of other well-known networks fabricated on single Ti:LiNbO/sub 3/ substrates.

Internet Access For Personal Mobile Equipments In A Wireless WAn Environment

Personal mobile equipment are often required to be simple, inexpensive, as well as powerful. We refer to this equipment as lightweight intelligent mobile equipment (LIME). This paper presents a protocol architecture supporting the Internet access for LIME using wireless WAN technologies such as GSM (Global System for Mobile communications), or CDPD (Cellular Digital Packet Data). Each LIME has a service agent located in a server connected to the mobile switching center. The proposed protocol is intended for the handover and data transportation between LIME and the LIME agent. The architectural design of LIME and its agent is also described.

A cell scheduling algorithm for VBR traffic in an ATM multiplexer

An efficient cell scheduling algorithm is proposed for multiplexing traffic sources with variable bit rate requirement in an ATM multiplexer. Three types of traffic sources an assumed in the multiplexer, namely the constant bit rate (CBR), variable bit rate (VBR), and best-effort traffic. For VBR and CBR sources, a statistical bandwidth requirement should be claimed before they are multiplexed in the ATM outgoing link. The proposed algorithm dynamically schedules the traffic and preserves the claimed throughput in the outgoing link for each CBR or VBR source. When there is no cell arrival at the VBR or CBR sources, the proposed algorithm assigns the bandwidth to the best-effort sources. The performance of the proposed algorithm is evaluated via simulation. The result shows that the proposed method has better performance over other static multiplexing schemes such as the weighted round-robin method.

Efficient real-time data retrieval through scalable multimedia storage

This paper presents a novel data placement and retrieving scheme or real-time multimedia stream playback via a scalable storage system. The multimedia streams are contiguous data packets which may be representing video, audio, or other media be retrieved simultaneously from a storage system on a real-time and on-demand basis, The major challenge in implementing the system is the support of simultaneously retrieving a big number of streams from a large-capacity storage system. This bottleneck comes from the seeking delay caused by the random movement of disk head in the storage under multiple stream requests. The proposed scheme efftciently reduces the seeking time by a very simple placement method and a retrieval scheduler and, in the mean time, continuous playback of multiple real-time streams and a scalable storage capacity are both achieved. Performance valuation of the proposed scheme is provided through theoretical analysis and experimental measure.

A scalable storage supporting multistream real-time data retrieval

Abstract. This paper presents a new data placement scheme for continuous-media playback via a scalable storage system. Multimedia contents are segmented into data blocks for the purpose of being stored, retrieved, and manipulated. If these data blocks belong to some continuous media, then they must be handled in a timely manner, for example, being retrieved before some deadline. One of the main challenges in implementing the above system is the simultaneous retrieval of a great number of different media streams from a very large storage system. The proposed scheme efficiently reduces the seeking delay by a very simple placement method and a retrieval scheduler. Thus, both the storage capacity and the number of concurrent accesses to the storage are scalable. The performance of the proposed scheme is evaluated through a simple analytical model and a practical prototype implementation.

A dual bus approach for LAN interworking with ATM networks

The interworking between conventional legacy LANs and the ATM network plays an important role in the initial step of the ATM roadmap. This paper presents a dual bus approach for connecting LAN interworking units (IWU) to ATM networks. Several IWUs connecting heterogeneous LANs are configured into a dual bus structure and the end of the buses are directly connected to the ATM ports. Each IWU transforms the connectionless frame from the legacy LAN to fixed-length time-slots on the dual bus. To provide reliable connectionless services, a cell-based flow control scheme is proposed for dynamically adjusting the cell input rate so as to match with the current resources in the ATM switch. The scheme is further verified to be able to provide an optimal, best-effort and reliable interconnection scenario through simulations. The results show that the total throughput obtained by each local subnetwork dynamically matches with the cell processing throughput of the ATM switch. Besides, each IWU on the dual bus shares a fair bandwidth.

A scalable architecture for video-on-demand servers

One of the most important requirements to bring the interactive video-on-demand services to residential consumer use is the scalability of the video server. The design issues for a scalable video server is described and, according to these issues, the system architecture of the scalable video servers are proposed. The system uses ATM switching technology to scale up the dimension of the service. There are four major components within the proposed system, namely the server headend control (SHC) unit, the stream router, the video pumping unit (VPU) and distributed storage devices. The functions of each components is described and the key components in the system are the stream router and the VPU. Operations and performance limitations on the video pumping unit are given and the result shows that a single storage device can serve only a limited number of video streams. Finally the paper focuses on the stream router as it is used to connect multiple VPUs. Experimental results show that the proposed stream router can produce guaranteed throughput and bounded delay variance for video applications.

A time-wavelength scheduling algorithm for interconnected WDM star networks

Although WDM-based single-hop star networks are attractive owing to their all-optical communication features, the throughput of such lightwave networks is limited due to the small number of available wavelengths. In this paper, a wavelength-reusable local lightwave network which consists of interconnected WDM star networks is proposed. Based on this architecture, the lower bound for the problems of minimizing the switching duration is derived. A transmission scheduling algorithm for this architecture to efficiently reuse the wavelengths is also proposed. The analytical result shows that the proposed scheduling algorithm always produces solutions no greater than twice of the lower bounds. Simulation results show that given the same number of users and available wavelengths, the solutions (in terms of the average switching duration and the average number of switching matrices) obtained by the proposed scheduling algorithm on the interconnected WDM networks are better than the optimal solution on a single-star WDM network. In most cases, the performance improvement achieves 20% to 45%.<<ETX>>

A new nonblocking network for photonic switching

A new switch architecture culled extended baseline networks (EBN) is proposed for nonblocking photonic switching. This switch is a space-division multistage network using 2/spl times/2 optical switch elements which may be directional couplers fabricated on titanium diffused lithium niobate (Ti:LiNbO/sub 3/) substrates. A recursive definition for the proposed architecture is presented. Some properties including the number of switch elements required, blocking characteristics, number of crossovers, system attenuation, and signal-to-noise ratio (SNR) are derived and analyzed. Most of the characteristics are shown to be better than those of other well-known networks-fabricated in single Ti:LiNbO/sub 3/ substrate.