Motorola Corporation

James R Engel

Eugene J Bruckert

Stuart W Thro

Michael A Stepien

Keith J Glidewell

Eugene Joseph Bruckert

A method and means for controlling transmissions among a plurality of communication units is described that determines an inhibit state based upon an inhibit signal and information in a header preceding a coded message before allowing transmission. This inhibit state prevents all of the other remote units from transmitting while a prescribed remote unit transmits a coded message or an acknowledgment (ACK) so that collisions between messages and ACKs, or between one ACK and another, are avoided. Message-message collisions are substantially reduced since the method causes a remote unit to utilize a random delay before attempting a retry to send the message a second time. Hence, the method and arrangement better coordinates inbound transmissions to the base station so that collisions on the inbound channel to the base station are minimized.

Method and arrangement for channel monitor and control

In a data message communication system, certain messages require a return acknowledgement signal. The present invention contemplates a method and means which are activated whenever an outbound message is received. Each portable unit which receives a message then monitors the outbound communication channel to determine if the inhibit signal is currently active. If the inhibit is not currently active, the particular unit will transmit its acknowledgement message immediately. If the inhibit signal is active, each portable unit will maintain a count of the number of outbound messages, addressed to other units requiring an acknowledgement, since that particular portable received its message. At the termination of the inhibit signal, each portable unit will pause for a period equivalent to the product of the acknowledgement message time slot multiplied by count of messages accumulated since the receipt of the particular portable units message. Each portable unit will then transmit an acknowledgement signal at the termination of its unique pause period.

Inbound acknowledgement stack

A radio data communications system is disclosed in which messages, normally lost to interference caused by independent remote units contending for the radio channel, may be salvaged. If a remote unit communicating a message to a fixed site is interrupted by a second remote unit having a stronger radio signal, the fixed site detects the increase of radio signal strength and activates a synchronization detector which responds to a synchronization data bit sequence which precedes each data message. If the synchronization sequence is detected, the remainder of the first remote data unit message is discarded and the message of the second remote data unit is processed.

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Sleepy Hollow, IL, United States of America

James R Engel