Distributed Communication Network Research Articles

Distributed communications in collision channels with errors

Analysis of distributed communication networks in noisy collision channels is given. Both feedback and feedforward channel errors are considered. A finite number of buffered users is addressed. It is shown that channel errors lead to stabilization of unstable access protocols, i.e. to elimination of the saturation phenomena and to stabilization of a network in a unique, globally asymptotically stable steady state with relatively high-performance characteristics. Thus channel noise, possibly introduced intentionally, could be viewed as a decentralized stabilizing controller.

System 75:Communications and Control Architecture

The System 75 office communication system uses a unique communications and control architecture that provides great flexibility and a minimum of overhead for small configurations while growing smoothly to larger line sizes. A distributed communication network provides 64 kb/s connectivity for both voice and data. It consists of a pair of time division multiplexed buses and intelligent port circuits. Flexible conferencing and gain adjustment are supported as an integral part of the network. The control complex supports an operating-system-based software structure.

On a Self-Adjusting Capability of Random Access Networks

We consider a distributed communication network with many terminals which are distributed in space and wish to communicate with each other using a common radio channel. Choosing the transmission range in such a network involves the following tradeoff: a long range enables messages to reach their destinations in a few hops, but increases the amount of traffic competing for the channel at every point. We give a simple model for the per-hop delay in random access networks, analyze this tradeoff, and give the optimal transmission range. When choosing this optimal range, as a function of specified traffic and delay parameters, networks demonstrate an important self-adjusting capability. This capability to adjust to traffic makes heavily loaded networks far better than centralized systems (in which all messages must reach one common destination). Dividing a terminal population into power groups can improve any random access system, especially when the traffic is split between groups in an appropriate way, which we demonstrate. But since networks are hurt by destructive interference less than centralized systems, it is harder to improve them. Using power groups can significantly improve centralized systems, but will lead to a smaller relative improvement in networks. Decomposing the system into a hierarchy of ALOHA levels, with only a small population contending at the top level, can improve centralized systems but does not improve networks.

On survivability of networks [Author reply to Deo's comments on "On distributed communications networks," By P. Baran

Narsingh Deo's comments suggests an alternative metric of survivability (pairs of stations in communications) to the one Paul Baran, the original author, chose to use in a recent paper on survivable communications (number of stations in communications with all, see ibid., vol. CS-12. pp. 1-9, March 1964). Deo's point (ibid., vol. COM-12, pp. 227-228, December 1964) is well stated and the original author would like to add to Deo's remarks.

On Distributed Communications Networks

This paper briefly reviews the distributed communication network concept in which each station is connected to all adjacent stations rather than to a few switching points, as in a centralized system. The payoff for a distributed configuration in terms of survivability in the cases of enemy attack directed against nodes, links or combinations of nodes and links is demonstrated. A comparison is made between diversity of assignment and perfect switching in distributed networks, and the feasibility of using low-cost unreliable communication links, even links so unreliable as to be unusable in present type networks, to form highly reliable networks is discussed. The requirements for a future all-digital data distributed network which provides common user service for a wide range of users having different requirements is considered. The use of a standard format message block permits building relatively simple switching mechanisms using an adaptive store-and-forward routing policy to handle all forms of digital data including digital voice. This network rapidly responds to changes in the network status. Recent history of measured network traffic is used to modify path selection. Simulation results are shown to indicate that highly efficient routing can be performed by local control without the necessity for any central, and therefore vulnerable, control point.