US 4,477,809 A · Method for random-access radio-frequency data communications

Abstract

A method for random-access data communications to and from a central controller, from and to at least one of a plurality of remote stations, by providing at least one radio-frequency channel having the bandwidth thereof allocated into at least a message channel and an acknowledgment channel. The message channel fractional bandwidth is greater than the acknowledgment channel fractional bandwidth. Status data is transmitted from each of the remote stations to the central controller, with the central controller acknowledging receipt thereof. In the event of a change of status message being received by the central controller, the central controller decides upon a course of action for the system and broadcasts system action messages, each addressed to a particular remote station at which the action is to be carried out. The operational system modes include a link-monitoring mode for checking the radio-frequency link paths between each of the remote stations and the central controller and a polling mode to sequentially request status from each of the remote stations.

Claims34

Dependent claims

A method for random-access data communications from and to a central controller, to and from at least one of a plurality of remote stations, comprising the steps of:

providing at least one radio-frequency channel having the bandwidth thereof allocated into at a message channel portion and an acknowledgement channel portion;
transmitting data between at least one of the remote stations and the central controller on the message channel portion;
acknowledging receipt of data at the central controller by a signal sent on the acknowledgment channel portion to at least the remote station transmitting the data;
normally operating the system to require each remote station to report unchanged status to the central controller;
determining, at a particular remote station, that a change of status has occurred;
requesting use by the particular remote station of the message channel portion to transmit changed-status data to the central controller;
recognizing an alert state at the central controller responsive to the received changed-status request;
transmitting from the central controller to the requesting remote station authorization for transmittal of a changed-status message;
and
transmitting the changed-status message to the central controller after receipt of the authorizing message.

7 more elements

A method for random access data communications from and to a central controller, to and from at least one of a plurality of remote stations, comprising the steps of:

providing at least one radio-frequency channel having the bandwidth thereof allocated into at a message channel portion and an acknowledgment channel portion;
transmitting data between at least one of the remote stations and the central controller on the message channel portion;
acknowledging receipt of data at the central controller by a signal sent on the acknowledgment channel portion to at least the remote station transmitting the data;
normally operating the system to require each remote station to randomly report unchanged status to the central controller;
transmitting an acknowledgment message on the acknowledgment channel portion to the reporting remote station after receipt of the unchanged-status message from that remote station;
and
causing a remote station previously transmitting a normal-mode unchanged-status message to the central controller to retransmit that message if an acknowledgment message is not received within a predetermined time interval after the initial unchanged-status message transmission.

4 more elements

Dependencies are inferred from the claim text.

Method for random-access radio-frequency data communications

Life of this patent

Method for random-access radio-frequency data communications

Life of this patent

Abstract

Claims34