Browse Prior Art Database

Channel Access Via Multiple Level Polling

IP.com Disclosure Number: IPCOM000048634D
Original Publication Date: 1982-Feb-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 3 page(s) / 95K

Publishing Venue

IBM

Related People

Gravate, CD: AUTHOR [+3]

Abstract

Digital Radio Communications Systems (DRCSs) for the deployment of, and communications with, servicemen are becoming more common. The DRCS involves a large number of remote, hand-held terminals which communicate with a central station controller (CSC) over one or more shared radio frequency (RF) channels. All data is preferably digital in nature and is transmitted in blocks, or "packets," not to exceed, for example, a predetermined block size (e.g., 256 bytes). However, classical access methods are inefficient where the number of devices sharing a communication channel is high.

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Channel Access Via Multiple Level Polling

Digital Radio Communications Systems (DRCSs) for the deployment of, and communications with, servicemen are becoming more common. The DRCS involves a large number of remote, hand-held terminals which communicate with a central station controller (CSC) over one or more shared radio frequency (RF) channels. All data is preferably digital in nature and is transmitted in blocks, or "packets," not to exceed, for example, a predetermined block size (e.g., 256 bytes). However, classical access methods are inefficient where the number of devices sharing a communication channel is high.

Wired or wireless communication channels are created through the use of frequency, time, code, or space division. Once a channel has been defined and must be shared by a plurality of communicating devices, a means of multiple channel access must be defined. These techniques are typically called either channel access control procedures or link control protocols. Digital data sources usually generate sequences of data at random instants of time. Because of this randomness, data sources utilizing the same communication channel will not always require simultaneous access to the channel. The proper selection of a dynamic resource allocation technique is fundamental to efficient system communication, since it is clearly wasteful to allocate capacity to an idle user. However, at times, the channel capacity is into the network so as to match the available capacity to offered traffic and obtain efficient use of the channel is the objective of any link control protocol.

The DRCS discussed above may involve over 1000 terminals sharing a single channel. Specifically, the channel is an FCC (Federal Communications Commission) allocated RF channel. Two common types tions Commission) allocated RF channel. Two common types of channel access methods are (1) completely random access and (2) unit polling of each sharing terminal. For the DRCS, the first approach can result in severe contention problems during high traffic periods, and eventually result in system "lock-up." The latter approach avoids a "lock-up" condition, but results in wasted channel capacity by polling numerous idle terminals. U.S. Patent 3,755,782 addresses some additional problems of the prior art.

The method disclosed here provides pseudo-random channel access while minimizing channel capacity used for contention resolution and useless polls. Fig. 1 depicts the current method applied to a system of 512 addressable terminals. Once the poll process is begun, the first poll is a "universal" poll to determine whether there is any terminal with inbound traffic. If there is no response, a decision is made whether to continue polling or exit the poll sequence. If there is a response, and there is no contention, the controller immediately services the respondin...