A guide to data communications: interconnecting LANs

The use of T1 multiplexers, bridges, routers, and gateways to tie together LANs spread over areas from a single building to a metropolitan area is addressed. What each of these does is described. Also discussed are backbone networks for LANs. Network planning, transmission facilities, switched services, and network management are considered with reference to interconnected LANs     

A guide to data communications: B-ISDN and how it works

The capabilities of the emerging broadband integrated services digital network (B-ISDN) are examined. Fundamental differences between broadband and narrowband ISDN are identified. The basics of asynchronous transfer mode (ATM), the switching technique used by BISDN networks, are discussed. Channel identification, generic flow control, using ATM, and connectionless service are considered. The first services expected to make use of ATM are briefly described     

An approach to high-performance, high-speed data networks

An approach that establishes a framework of design for high performance that scales well with increasing delay-bandwidth products is described. A basic conceptual model to explain the roles of window and access controls is presented. A static model of the system is then studied. The steady-state distribution of the buffer sizes, asymptotic expressions, and relationships between window size and delay that will be used to control windows are derived. A class of adaptive control schemes is proposed, and some results on simulation studies of one scheme are presented. A fluid model with dynamics is introduced to study fundamental questions of adaptive windows to adaptive rates. Bursty sources are considered. The proposals are then compared with other approaches     

ISO 8802/3 local-area networks

The most widely used form of local-area network is formally defined as the ISO 8802/3 carrier sense multiple access with collision detection system, more commonly known as Ethernet. Different market surveys attribute varying degrees of commercial penetration for Ethernet but within Europe it is generally agreed that it is used for some 50% of all installed local networks (token ring installations accounting for another 25%). It is therefore somewhat surprising to find that there is still a considerable amount of ignorance in understanding how it operates and the range of architectural options available for installations. In fact it is the extent of this ignorance amongst users and network managers which reflects its ease and simplicity of use and which is a tribute to its outstanding product engineering and the efforts of the standardisation organisations     

Half-symbol-rate-carrier PSK modulation for bandwidth-efficient high-speed data communications

This paper proposes new quadrature phase-shift-keying (QPSK) modulation techniques for high-speed data communication systems that use two orthogonal half-symbol-rate-carrier (HSRC) signals by which channel bandwidth requirements are reduced compared to that of the conventional non-return-to-zero (NRZ) modulation. The simulation results show the HSRC-QPSK has almost the same bit-error-rate (BER) performance with reduced signal bandwidth compared to that of the NRZ modulation. This paper also analyzes the performance of the recently proposed HSRC offset-QPSK (HSRC-OQPSK), which improves spectral efficiency by reducing the side lobes of the signal spectrum. In addition, HSRC minimum-shift-keying (HSRC-MSK) modulation is also introduced. The performances and the simulation results of the proposed modulation techniques are studied and compared with those of the conventional ones.     

Token-ring local-area networks and their performance

The major technical concepts underlying token-ring technology are examined, and performance issues arising in the design of such local-area networks (LANs) are detailed. Following a survey of analytical queuing models to describe the basic token-ring operation, three topics are discussed in detail: (1) the IEEE 802.5 token ring and its performance; (2) the ANSI fiber distributed data interface (FDDI) token ring and its performance; and (3) architecture and performance issues arising in the interconnection of token-ring networks with regard to the various components of a multiring architecture demonstrating which congestion-control problems can arise in such a network and how they can be overcome. The author concludes with a number of open questions concerning the understanding of the quantitative behavior of token-ring-based LANs     

Fiber optic backbone boosts local-area networks

The evolving Fiber Distributed Data Interface (FDDI) for fiber optic networks, which greatly increases system capacity and flexibility, is discussed. The standard is described in terms of the ISO's Open Systems Interconnection (OSI) reference model. The initial FDDI standard defines four protocols: physical layer medium dependent, physical layer, media access control, and station management. Each of these is examined. Optical technology and the use of application-specific integrated circuits required by FDDI are discussed. Applications of FDDI and its future evolution are considered     

Media access control for high-speed local area and metropolitanarea communications networks

The features, architectures, and principles of key media access control (MAC) schemes for high-speed LAN and MAN systems are categorized and reviewed. These architectures are related to the hierarchical structure of a telecommunications network. An overview is given of the MAC protocol operation of key local- and metropolitan-area network systems, as defined by standards committees, covering current methods as well as approaches for future broadband integrated services digital networks. Modeling and analysis techniques are then reviewed for key classes of relevant MAC schemes, including fixed-assignment time-division-multiaccess (TDMA) schemes; demand-assignment reservation schemes, involving, in particular, pure packet-switched, pure circuit-switched and hybrid-switched integrated-services demand-assignment TDMA and time-division-multiplexing structures; demand-assigned polling procedures; and random-access policies     

Secure virtual private networks: the future of data communications

The Internet is an almost ideal means for information retrieval and exchange. It is cost‐effective, easy to use and easily accessible. However, it can also be susceptible to devious practices such as data tempering, eavesdropping and theft. This paper analyses secure virtual private networks (VPNs) and their use in countering the problems of the Internet. Copyright © 1999 John Wiley & Sons, Ltd.     

Transmission code for high-speed fibre-optic data networks

A new DC-balanced 8B/10B code for packet transmission on fibre-optic links optimises data integrity, efficiency and implementation cost. It translates eight bits into ten with bounds of five and six on run length and digital sum variation, respectively. Encoders and decoders built with 380 ECL 10K-series gates have passed tests at 20 Mbytes/s.     

Topological design of local-area networks using genetic algorithms

In this paper, we describe an algorithm for designing local-area networks (LANs) with the objective of minimizing the average network delay. The topology design includes issues such as determination of the number of segments in the network, allocating the users to the different segments, and determining the interconnections and routing among the segments. The determination of the optimal LAN topology is a very complicated combinatorial optimization problem. Therefore, a heuristic algorithm that is based on genetic ideas is used. Numerical examples are provided and the quality of the designs obtained by using the algorithm is compared with lower bounds on the average network delay that are developed     

Ethernet-based passive optical local-area networks for fiber-to-the-desk application

We introduce optical local-area network (LAN) architectures based on multimode optical fiber and components, short wavelength lasers and detectors, and the widely used fast Ethernet protocol. These architectures are designed to lower the costs associated with passive optical LAN implementation. Further reduction in overall cost is achieved through decreased network downtime, lower maintenance cost, extended geometrical spans, and larger headroom for future capacity increase. These optically transparent networks represent a novel approach for implementing fiber-to-the-desk.     

ISO 8802/5 token ring local-area networks

Token ring networks are the second most commonly used type of local-area network (LAN). The second version of the formal token ring multiple access mechanism, ISO 8802/5, was released in late 1995 and this rationalised many of the new developments, e.g. the 16 Mbit/s solutions. The latest innovations are the full duplex dedicated token ring and the development of a 100 Mbit/s high-speed token ring solution. To many people's surprise there is an extensive legacy of token ring installations and the latest innovations, such as token ring switching, are an attempt to maintain and support this significant market presence. Token ring is designed to provide high throughput under heavy loads (something which is normally impossible for Ethernet to sustain) but in most cases it is used in typical office environments where there is infrequent occurrence of heavy loads     

Architectures and technologies for high-speed optical data networks

Current optical networks are migrating to wavelength division multiplexing (WDM)-based fiber transport between traditional electronic multiplexers/demultiplexers, routers, and switches. Passive optical add-drop WDM networks have emerged but an optical data network that makes full use of the technologies of dynamic optical routing and switching exists only in experimental test-beds. This paper discusses architecture and technology issues for the design of high performance optical data networks with two classes of technologies, WDM and time division multiplexing (TDM). The WDM network architecture presented stresses WDM aware Internet protocol (IP), taking full advantage of optical reconfiguration, optical protection and restoration, traffic grooming to minimize electronics costs, and optical flow-switching for large transactions. Special attention is paid to the access network where innovative approaches to architecture may have a significant cost benefit. In the more distant future, ultrahigh-speed optical TDM networks, operating at single stream data rates of 100 Gb/s, may offer unique advantages over WDM networks. These advantages may include the ability to provide integrated services to high-end users, multiple quality-of-service (QoS) levels, and truly flexible bandwidth-on-demand. The paper gives an overview of an ultrahigh-speed TDM network architecture and describes recent key technology developments such as high-speed sources, switches, buffers, and rate converters     

Smart-antenna operation for indoor wireless local-area networks using OFDM

This paper reports link-level Monte Carlo simulations for a system that is compatible with the physical layer of the 5-GHz IEEE 802.11a wireless-local-area network and utilizes an adaptive antenna array at the access point for single-user smart-antenna operation, as well as for space-division multiple access (SDMA). For the spatial indoor radio propagation channel, complex impulse-response recordings are used. These are obtained in wideband channel-sounder measurements in three different buildings at 5.3 GHz. Thus, no unrealistic assumptions about channel conditions are involved. The paper studies how the packet-error-rate performance for the downlink (DL) is affected by time evolution of the radio channel that takes place after the uplink operation in which channel estimation is performed, and before DL operation in which the estimated channel information is utilized. Based on simulations two-user SDMA is possible with four-antenna elements under indoor propagation conditions and with six antennas three users can simultaneously be served. Delay spreads, coherence bandwidths, and correlation properties (in space, frequency, and polarization) of the radio channels obtained in the measurements are also discussed. The results suggest that indoor time-division-duplex systems with access-point-controlled scheduling are desirable communication systems which can benefit from SDMA.     

Fiber-optic subcarrier multiplexed CDMA local-area networks forsubband image transmission

This paper investigates the application of subcarrier multiplexed code-division-multiple-access (CDMA) techniques to image transmission over fiber-optic local-area networks (LANs). In the hybrid scheme, CDMA is used to suppress the interference caused by the laser nonlinearity in the subcarrier multiplexing (SCM) fiber-optic communication systems. Likewise, the SCM scheme is able to increase the channel data rate of CDMA systems. This hybrid system combines the advantages of both schemes and is particularly well suited to subband coding that divides the image information into multiple parallel data streams using an analysis filter bank, each of which is transmitted via a unique subcarrier-code pair, where the spreading code and subcarrier frequency correspond to the image and one of its subbands, respectively. This hybrid scheme also allows more than one image to be transmitted and be accessed simultaneously at the same channel bandwidth, in which each image is assigned a particular spreading code added to its digital data modulating the subcarrier. After transmission, each received signal is independently recovered at a high-Q surface acoustic wave (SAW) receiver with the matching subcarrier-code pair. Other concurrent signals are rejected by the SAW. Then, all the recovered subbands are reassembled by a synthesis filter bank into a close reproduction to the original image. The image quality of subband image transmission via CDMA/SCM fiber-optic channels is evaluated and examined     

A high-speed low-complexity Reed-Solomon decoder for optical communications

This paper presents a high-speed low-complexity Reed-Solomon (RS) decoder architecture using a novel pipelined recursive modified Euclidean (PrME) algorithm block for very high-speed optical communications. The RS decoder features a low-complexity key equation solver using a PrME algorithm block. The recursive structure enables the novel low-complexity PrME algorithm block to be implemented. Pipelining and parallelizing allow the inputs to be received at very high fiber-optic rates, and outputs to be delivered at correspondingly high rates with minimum delay. This paper presents the key ideas applied to the design of an 80-Gb/s RS decoder architecture, especially that for achieving high throughput and reducing complexity. The 80-Gb/s 16-channel RS decoder has been designed and implemented using 0.13-/spl mu/m CMOS technology in a supply voltage of 1.2 V. The proposed RS decoder has a core gate count of 393 K and operates at a clock rate of 625 MHz.     

A high-speed transmission method for wireless personal communications

The next-generation wireless personal communications systems are expected to support a wide range of high-quality services that require high data rates. Communicating at high transmission rates over the harsh wireless environment, however, creates many difficult and challenging problems. In this paper, we describe a technique for the high-speed transmission of data in wireless personal communications which we denote as multicode modulation. In this technique, the high-rate bit transmitted data is serial to parallel converted into low-rate bit streams in a similar fashion to multicarrier or multitone modulation. However, in contrast to the multicarrier method, here we propose to modulate each low-rate bit stream using direct-sequence spread-spectrum on a single carrier. It is demonstrated that by selecting the processing gain properly the total required bandwidth will be of the same order as the original high-rate data stream; thereby, gaining the inherent benefit of multipath rejection without expanding the bandwidth of the original high-rate stream. To demonstrate the potential and merits of the proposed method as an alternative technique for high-speed transmission for wireless personal communications, various simulation results over a multipath Rayleigh fading link are presented.Supported in part by the Hong Kong Research Grant Council, Project No. HKUST562/94E and the Hong Kong Telecom Institute of Information Technology, Project No. HKTIIT94/95.EG03.