Use of spread spectrum techniques on fiber optic cable for local area networking.

摘要

In contemporary Local Area Networks (LANs), there is a delay associated with gaining network access for transmitting data. This delay is caused by the access protocol in an attempt to ensure that messages are sent without collision on a shared medium or that these messages stay within their own space on a partitioned medium. Typically, there is also a restriction on message length, and all LANs require the potential transmitting site to monitor either the data band or a control band, to determine when transmission is permitted and/or whether transmission was successful.; The proposed system suggests a change to the conventional paradigm. By using Transmitter addressed CDMA (Code Division Multiple Access), as opposed to Receiver addressed, the system does not impose any of these delays, or access/transmission length restrictions. We have based our design of the FOSSL system (Fiber-Optic Spread Spectrum LAN) on demonstrated technology. We examine the impact of the proposed source addressing modification, and describe a network that provides: (1) immediate and simultaneous access by all users; (2) arbitrary length transmissions (including continuous); (3) all data available to all nodes; (4) support of sensor type nodes (no receive or monitor capability required).; We discuss the costs, and implementation restrictions. The optically coupled star on which the FOSSL system is based, gives some limitation, and the fact that the message size increases significantly with the number of possible simultaneous users puts a practical limitation on the number of nodes in a single CDMA network. We present the theoretical limit on the message size rate of increase, and suggest a way in which networks may be interconnected using more conventional techniques.; The discussion and examples include the use of Synchronous CDMA (S/CDMA) a technique with some of the features of Conventional CDMA. Several models of the use FOSSL system as a multiprocessor interconnection fabric are presented. We show the compared time for interprocessor communications for conventional topologies and FOSSL. One example illustrates the use of the system to implement a dynamically reconfigurable multiprocessor.