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Communication Link Between a Loop System and a Remote Loop

IP.com Disclosure Number: IPCOM000076027D
Original Publication Date: 1971-Dec-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 4 page(s) / 67K

Publishing Venue

IBM

Related People

Mallar, EE: AUTHOR [+4]

Abstract

In high-speed multichannel loop transmission systems, there is a need to attach a control unit to the main loop which connects via common carrier to another control unit, which in turn drives a remote loop (Fig. 1). The nature of the data transfer between the main loop and the remote loop requires multiple channels, as well as bidirectional data transfer. Conventional methods of communicating over a communication line allow for interleaving of data to different sinks at the message level. This method necessitates a buffered device, which in turn requires that the remote loop control unit has the intelligence necessary to maintain the desired level of reliability and serviceability. The hardware and response time considerations make this approach unfeasible for this application.

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Communication Link Between a Loop System and a Remote Loop

In high-speed multichannel loop transmission systems, there is a need to attach a control unit to the main loop which connects via common carrier to another control unit, which in turn drives a remote loop (Fig. 1). The nature of the data transfer between the main loop and the remote loop requires multiple channels, as well as bidirectional data transfer. Conventional methods of communicating over a communication line allow for interleaving of data to different sinks at the message level. This method necessitates a buffered device, which in turn requires that the remote loop control unit has the intelligence necessary to maintain the desired level of reliability and serviceability. The hardware and response time considerations make this approach unfeasible for this application. Therefore, a data byte interleaving technique was developed. As a further consideration, the data rates on each channel have no fixed relationship to each other, but are limited by the individual channel rates of the various channels on the main loop and/or remote loop. The total thruput is governed by the lesser of the sum of the individual channel rates, or the maximum thruput that can be achieved over a particular common carrier facility using the interleaving technique that was developed.

To meet these requirements, a full-duplex communication facility is interfaced at each end with a communication adapter which has the following features:
1) A framing technique or line control for transmitting data

and control information over the communication line.
2) Interleaving of channels for transfer of data at the frame

level at unrelated data rates in both directions (i.e.,

both "read" and "write" capabilities).
3) Checking of the data transfer over the communication line

by a "readback" method in lieu of other techniques such as

vertical redundancy check, longitudinal redundancy check,

cyclic redundancy check, double transmission of data, etc.
4) Interlocking/self-regulating flow of data to and from the remote loop.

In general, this technique can be extended to any number of channels. For each additional channel, a portion of the hardware in the control units at either end of the communication line would be duplicated and the controls extended. Also, the data rate on the communication line would need to be increased in order to maintain the maximum thruput on all the channels. To further generalize, this technique could be used as a communication link between two removed communication systems, not necessarily of the loop variety. However, it was developed to solve a practical problem in which two channels sufficiently satisfy the requirements. For this reason and for simplification, the following discussion will use the two-channel case to explain the highlights of the technique in more detail.

The control units at each end of the communication line can be divided into the following three functional u...