Showing papers on "Fast packet switching published in 1978"

The evolution of packet switching

Abstract: Over the past decade data communications has been revolutionized by a radically new technology called packet switching. In 1968 virtually all interactive data communication networks were circuit switched, the same as the telephone network. Circuit switching networks preallocate transmission bandwidth for an entire call or session. However, since interactive data traffic occurs in short bursts 90 percent or more of this bandwidth is wasted. Thus, as digital electronics became inexpensive enough, it became dramatically more cost-effective to completely redesign communications networks, introducing the concept of packet switching where the transmission bandwidth is dynamically allocated, permitting many users to share the same transmission line previously required for one user. Packet switching has been so successful, not only in improving the economics of data communications but in enhancing reliability and functional flexibility as well, that in 1978 virtually all new data networks being built throughout the world are based on packet switching. An open question at this time is how long will it take for voice communications to be revolutionized as well by packet switching technology. In order to better understand both the past and future evolution of this fast moving technology, this paper examines in detail the history and trends of packet switching.

A Microprocessor-Based PSK Modem for Packet Transmission Over Satellite Channels

Abstract: This paper describes a microprocessor-based modem developed for use in a packet switching network over satellite channels. This digital modem can process both BPSK and QPSK packets with near optimum error rate performance over channels with marginal signal energy-to-noise density ratio. Of principal concern is the development of the discrete time algorithms which form the basis of the microinstruction program. The processing of a packet can be decomposed into two basic stages: (1) the detection of the packet preamble and the rapid estimation of signal parameters (symbol timing and carrier frequency offset) for the specific packet, and (2) the demodulation of the data portion of the packet including the tracking of both symbol timing and carrier offset phase, phase ambiguity resolution and data symbol estimation. The paper concludes with details on the performance of the modem under operational conditions and a brief discussion of implementation of the processor.

Packet switching in a processing satellite

Abstract: This brief note represents a simple but significant change in the thinking that is applied to satellite packet switching. It demonstrates that in a precessing satellite there is no fundamental limitation to the efficiency and throughput of packet switching systems. With a minimal impact on spacecraft weight and power, throughput is increased by providing more capacity on the uplink than on the downlink. Efficiency is increased because the power-intensive downlink is more fully utilized. A slotted ALOHA example is given to show how the performance can be made to go from that of conventional slotted ALOHA to that of a TDM system. Several possible variations and far-reaching implications are indicated.

Delay and Throughput Evaluation of Switching Methods in Computer Communication Networks

Abstract: Message, packet and line switching in computer communication networks are analyzed by a queueing model. Message transmission delay time and network throughput between a source-destination node pair are obtained as a function of various parameters including message length, traffic arriving at the network, and the number of switching nodes existing between the nodes. A criterion to determine the most suitable switching method under the given conditions is offered. Also, the maximum length of a packet in packet switching is discussed.

Multiaccess Model for Packet Switching with a Satellite Having Processing Capability: Delay Analysis

Abstract: The multiaccess model for satellite packet switching proposed by the authors [1] employs a frame format, with scheduling assignments broadcast from the satellite. The total delay recurred by a data packet in traversing the satellite channel consists of queueing delay, scheduling delay, transmission delay and propagation delay. In this paper we analyze the queueing and scheduling delays and compare the analytical and simulation results. For the queuemg delay analysis we model the multiaccess scheme using an M/D/N queue, where N is the number of slots per frame. For the scheduling delay analysis we emply a round-robin scheduling assignment algorithm. We treat the cases with and without random transmission; our results indicate that random transmission improves the queueing delay performance.

Combinatorial Issues in Mobile Packet Radio Networks

Abstract: A Packet Radio Network is a store-and-forward packet system employing radio links. A Mobile Packet Radio Network generalizes this system by allowing every radio unit to be independently in motion. In this paper a model for the analysis of connectivity as a function of time in such a network is presented and used to solve for parameters of interest. The model and the related analysis are guides for developing procedures for monitoring connectivity.

Interface communication processor for public packet switching network

Abstract: Promoted by the advancement of computer communication technology and social needs for data communications, many countries are setting up public data networks using mostly packet switching technology. Meanwhile, with the wide distribution of data communication service areas, interconnection of local networks and computers have become very important. Intercomputer communications through public data networks by means of packet switching are expected to become common in the future. In that case, the interfaces between the networks and subscriber terminals (i.e., DTE such as host computers and terminals) and the protocol are very inportant, and they contain many problems requiring solution.

Near optimal behaviour of the packet switching broadcast channel

Abstract: The subject of this paper is an adaptive control procedure for stabilizing and optimizing the performance of ALOHA-like slotted packet switching channels. We prove sufficient conditions, via a mathematical model of the adaptive procedure,under which the procedure stabilizes the channel. This procedure is based on "listening" to the silent periods of the channel and modifying the retransmission probabilities of the blocked terminals as a function of this measurement. The optimal choice of the parameters of the adaptive procedure is analysed and simulation results are given in order to illustrate its practical effect.