High-performance Local Area Network Research Articles

Opnet Based Performance Analysis and Comparison Among Different Physical Network Topologies

Physical network topology is the configuration of computers, cables and other peripherals as a geometrical shape. There are many types of topologies each of them has many advantages and disadvantages. For high performance Local Area Networks (LANs), the builder of a network should select the best physical network topology. This paper analyzes three basic network topologies including bus, star and ring for different number of connected nodes (various network topology size) using OPNET simulator. Four scenarios are configured for each topology with number of connected nodes equal to 5, 10, 15 and 20 for senario1, 2, 3 and 4 respectively. In this analysis, four parameters investigated in Delay (Sec.) for the complete network, Load (Bits/Sec.), Traffic Received (Bits/Sec.) and the number of Collision for single node (server). Performance comparison is made in each topology separately based on various network size and another comparison is also made between these topologies for the same number of connected devices. The comparison results indicate that performance decreased when the network size increased and also show that bus topology is more effected than two other topologies.

A reconfigurable platform for evaluating the performance of QoS networks

Nowadays, high performance System and Local Area Networks (SAN/LAN) have to serve heterogeneous traffic consisting of information flows with different bandwidth and latency requirements. This makes it necessary to provide Quality of Service (QoS) and optimize the design of network components. In this paper we present a hardware tool designed to analyze the performance of QoS networks, under given traffic conditions and server models. In particular, a reprogrammable multimedia traffic Generator/Monitor platform has been built. This permits prototyping the communication system of a high speed LAN/SAN on a single FPGA device. Hence, it can be used at design to produce more efficient devices. To illustrate the applicability of the platform we have used the Simple Multimedia Router (SMMR), an existing proposal to provide QoS. The modular structure of the tool and the fact that it has been implemented on an FPGA using a high level hardware programming language makes it flexible, scalable and easy to reconfigure. Besides, the architecture and implementation can be adapted to be used in more recent QoS NoC environments.

Multimedia-MAC protocol: its performance analysis and applications for WDM networks

The design of the medium-access control (MAC) protocol is the most crucial aspect for high-speed and high-performance local and metropolitan area networks, since the decisions made at this level determine the major functional characteristics of these networks. Most of the MAC protocols proposed in the literature are not suitable for multimedia applications, since they have been designed with one generic traffic type in mind. As a result, they perform quite well for the traffic types they have been designed for, but poorly for other traffic streams with different characteristics. In this paper, we propose an integrated MAC protocol called the Multimedia-MAC (M-MAC), which integrates different MAC protocols into a hybrid protocol in a shared-medium network to efficiently accommodate various types of multimedia traffic streams with different characteristics and quality-of-service demands, namely, a constant-bit-rate traffic, bursty traffic (say, variable-bit-rate traffic), and emergency messages (say, control messages). We have developed a mathematical framework for the analysis and performance evaluation of our M-MAC protocol, which involves a queueing system with vacation. We have applied our M-MAC design approach to a wavelength-division multiplexing network, and evaluated its performance under various traffic conditions.

Performance analysis of HIPERLAN∕2 in QAM mode with punctured and non-punctured convolutional coding

Simulation of ETSI's High Performance Local Area Network Type 2 (HIPERLAN/2) is presented. MATLAB/Simulink modelling demonstrated that for 64-QAM mode, with coding rate 2/3, a data rate of 48 Mbit/s is achieved with 3.2 dB SNR improvement compared to coding rate 3/4 (with puncturing) as required for the maximum 54 Mbit/s.

Space-frequency coded HIPERLAN/2

This paper attempts to provide an evaluation of high performance local area network type 2 (HIPERLAN/2), equipped with space-frequency coded double-antenna transmit diversity. The HIPERLAN/2 physical layer entities are simulated for frequency-selective fading channels for the standard's digital modulation schemes of BPSK, QPSK, 16-QAM and 64-QAM. Protocol data unit (PDU) error rate comparisons of HIPERLAN/2 with and without space-frequency coding reveal the potential gains and caveats. The analytical bit error probability calculations confirm that the simulation results are consistent with the theory.

An antenna diversity MMIC vector modulator for HIPERLAN with low power consumption and calibration capability

The design and performance of a vector-modulator-based phase shifter for high-performance radio local area networks at 5.2 GHz is presented in this paper. Low power consumption is achieved using a 0.6-/spl mu/m GaAs MESFET process. At a voltage supply of 1.4 V and with a current consumption between 3.5-7 mA, the gain is 0.6 dB and the 1-dB input compression point is -9 dBm. A full 360/spl deg/ phase control range is achieved by combining two of the three vectors, which have phase offsets of 120/spl deg/, with variable amplitude. Chip size is only 1.3 mm/sup 2/. The proposed vector modulator applies a new circuit configuration of variable-gain amplifiers to compensate their transmission phase errors. Within a gain control range of 20 dB, the phase error can be reduced to /spl plusmn/3/spl deg/, which is about a factor of eight better than the results obtained by single FET amplifiers. A simple calibration procedure for the proposed vector modulators is presented to improve the manufacturing yield and to decrease the impact due to temperature changes and aging. A maximum gain error of /spl plusmn/0.8 dB and a maximum phase error of /spl plusmn/7/spl deg/ have been measured after applying this calibration to the designed vector modulator.

Making network interfaces less peripheral

A barrier to delivering improvements in network bandwidth and latency to users is the network interface (NI), which connects a network to the host computer that runs the network software. An NI includes hardware that exposes an internal interface-such as device registers-to a host processor. A key problem with most current NIs is that their internal interface is similar to that of a disk's interface. Because of such limitations, current NIs will not be adequate for use with newer, high-performance networks and host computers. High-performance local area networks have advanced so far that some view them as a new class of networks called system area networks (SANs). Emerging SANs deliver bandwidths of 10 Gbps or more and latencies of tens of nanoseconds-two to four orders of magnitude better than that delivered by most current LANs. New hosts demand much higher performance. If NIs do not adapt to these changes they will become a barrier to improving network performance. To solve this problem, future NIs should appear to their hosts more like memory than disk interfaces. The authors argue that treating NI accesses like memory accesses is justified by the importance of network performance to future computers.

Co-channel and self-interference analysis for indoor wireless channels

To achieve a user data rate of 20 Mbit/s in the high performance local area network (HIPERLAN) system operating in indoor environments, channel equalization must be used to mitigate the effects of multipath propagation. If, however, the indoor channel impulse response length is too long, then the multipath power outside of the equalisation capability of the equalizer acts as a form of self interference. Moreover, co-channel interference may also be present at the detector input. Considering these two effects as well as the rms delay spread, this paper derives analytical expressions for the probability of outage.

Performance comparison of media access protocols for Gbit/s networks in the local area

The evolution towards future communication systems is strongly influenced by increasing transmission capacities, changing service requirements and the emerging ATM technology. The next generation of high-performance local and metropolitan area networks has to be designed including control schemes which provide high throughput while simultaneously supporting real-time services. The slotted ring architecture enhanced by spatial slot reuse is one potential approach for data transmission and admission control in distributed Gbit/s networks. Various concepts have been proposed for an efficient medium access control which maintains fairness and bounded access delays. By using simulation results, this paper compares the performance of several protocols: ATMRing (ATMR), CRMA-II (Cyclic Reservation Multiple Access) and MetaRing. First, the differences in their basic mechanisms are generally analysed applying saturated traffic scenarios. Then the behaviour in a multi-service environment is discussed, with particular regard to the requirements of universal broadband services. It is shown that all approaches offer efficient bandwidth sharing mechanisms. They overcome the well-known trade-off between high throughput and strong real-time requirements by providing extended bandwidth for user data and suitable end-to-end delays. Their performance, however, is quite sensitive to the actual network conditions and chosen protocol parameters.

Media access techniques: The evolution towards terabit/s LANs and MANs

Abstract Multimedia services, teleconferencing, high-performance visualization and open-system connectivity are expected to accelerate the demand for high-speed and high-performance Local and Metropolitan Area Networks (LAN/ MANs). These must be able to span large geographical areas and to serve large populations. This paper tracks the evolution of the diverse media access techniques used in standardized, experimental and proposed networks through three technology generations. Full exploitation of technological advances has been an ongoing challenge. The first generation, which includes Ethernet, Token Ring, and Token Bus, predominantly covers bit rates of some 10 Mbit/s. The second generation comprises a large variety of network configurations and access mechanisms in the speed range from 100 Mbit/s up to multi-Gbit/s. A remarkable number of basic access schemes and numerous variations reflect the difficulty of simultaneously achieving high throughput, low delay, fairness and scalability. In the third technology generation, architectural and experimental network designs have begun taking advantage of the tremendous transmission bandwidth of more than 20 THz of the optical medium. The intent of this paper is to track this evolution, giving a concise characterization of the diverse access protocols and providing pointers to the related literature.

A scheme for high-performance LAN interconnection across public MAN's

The proliferation of local area networks (LANs) and the emergence of high-bandwidth public networks will create an environment in which it will become increasingly simple and attractive to communicate among different organizations across a common public networking infrastructure. The open bridging scheme proposed, which employs inherent features of forthcoming cell-based metropolitan area networks (MANs) in order to achieve efficient interenterprise communications is introduced. It uses enhanced remote LAN bridging techniques to ensure router-level functionality with bridge-level simplicity and performance. The practicality of open bridging is shown by describing how it can be incorporated in networks using current standard protocol stacks, such as open systems interconnnection (OSI) and transmission control protocol/internet protocol (TCP/IP). >

Local Area Networks for microcomputers

This paper analyses the ways in which modern high performance Local Area Networks (LANs) can be of use to microcomputers. It discusses some of the basic concepts of LANs, with special reference to international standards. It then presents ways in which LANs may be connected to, and used with microcomputers. Examples are given of existing applications.

HUBNET performance measurement

Media-access delays in HUBNET, a high-performance local area network, are examined. An experimental technique for loading such a network with data up to 97.5% of its nominal bit rate is described. The results of a series of measurements of the packet-access delay in a network operating at loads up to 87.5% of capacity are presented. A modeling technique for this process is developed, and the results of calculations based on that model are compared to the experimental results. Extremely good agreement is obtained. The model is then used to examine the network behavior comprehensively over an extensive range of parameters.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The evolution of the mission control center

A discussion of the function and history of the Space Shuttle Mission Control Center describes the communications and data processing facilities, with an emphasis on display system changes. The current display system will be replaced by new technology as part of a project called the Mission Control Center Upgrade. That upgrade will implement a set of high-performance Local Area Networks (LANs) which transmit real-time and historical data to engineering workstations for processing and display. The benefits from such an architecture include a more flexible software development environment and a more modular system which will promote future upgrades. The proposed upgrade architecture is explored, and the engineering and project management challenges of that effort are described, emphasizing the local area networks task.

Centrenet - A High Performance Local Area Network

Centrenet - A High Performance Local Area Network

An overview of the proposed american national standard for local distributed data interfaces

The Local Distributed Data Interface (LDDI) Project of X3 Technical Committee X3T9 has resulted in three draft proposed American National Standards for a high performance local area network. The proposed standards are organized in accordance with the ISO Reference Model for Open Systems Interconnection and encompass the lowest two protocol layers (data link and physical) of the model, plus a serial broadband coaxial bus interface. The intended application of the LDDI is as a backend network for the interconnection of high performance CPUs and block transfer peripherals such as magnetic disk and tapes. A carrier-sense multiple access with collision prevention (CSMA-CP) distributed bus arbitration protocol is employed. The cable interface supports the attachment of up to 28 ports over a cable distance of 0.5 km (8 ports may be attached to a 1 km cable) at a transfer rate of 50 Mbit/s.