Computer Automation, Inc.

Hughes Aircraft Company

Michael S Friedman

Royce Earle Slick

Peter D Shloss

Dale R Feikema

Philip T Chan

Kenneth D Thomas

A TDMA network for reader-transponder communications including a receiver having an antenna for receiving and transforming radiated energy to a first RF signal and a detector for demodulating and converting the first RF signal to a digital signal. A protocol logic device is provided for decoding the digital signal and for executing a protocol. The protocol comprises a plurality of randomly selected time slots to gain admission to the TDMA network and a plurality of assigned time slots to transmit messages during the reader-transponder communications. In a transponder implementation, an oscillator is provided for converting protocol formatted digital signals from the logic device to a second RF signal. Thereafter, the antenna transforms the second RF signal to radiated energy and transmits the radiated energy. In a preferred embodiment, the TDMA network includes a transmit/receive switch for directing the first and second RF signals along the receive and transmit paths, respectively. A digital memory which communicates with the protocol logic device is provided for storing data unique to a transponder. The protocol also includes a reader control message time slot for interrogating the transponder and an acknowledgment time slot for indicating the reception of a message.

TDMA network and protocol for reader-transponder communications and

An interface modem for use in a broadband local area data network with collision avoidance protocol. The data link controller features hardware acknowledge circuitry that acknowledges the receipt of a perfect data packet immediately upon receipt thereof without request to or assistance by the client data processing unit. The DLC prepares the acknowledgement packet from the incoming data packet and places it on the data link without going through a line acquisition protocol. Each received acknowledgment packet is placed in a transmit buffer at a known location relative to the data packet which was just transmitted, for which it is an acknowledgment so that each acknowledgment packet may be located in less time by the client data processing unit. The acknowledgment packets are logically part of the transmit process and are therefore placed in the transmit buffer.

Decentralized line reservation interface within a local data network

A modem for a single frequency, modulated RF carrier local data network for a distributed data processing system and a method for line acquisition and contention resolution. The protocol established for line acquisition and contention resolution is implemented by a modem controller. The controller causes the receiver section to listen for foreign carriers to determine when the line is busy. When the client device of the modem desires to send a data packet to another unit, the modem controller causes the receiver to listen for a certain pre-burst period and then causes the transmitter to send a burst of RF carrier out on the line and simultaneously causes the receiver to listen to the line for interference beating, i.e. changes in amplitude on the line which indicates another unit is requesting the line. To insure beat patterns, the frequency of the burst carrier is swept over a range during the burst. If a contention is found, a resolution thereof is made utilizing a random delay and retry protocol. After the burst, the controller causes the receiver to listen to the line for other carriers. If none are found, the controller causes the transmitter to transmit a data packet preceded by a preamble of 100% modulation level RF carrier. During the preamble period, all receivers in the system set their respective automatic gain control levels to a level for comfortable reception. The gain level so established depends upon the strength of the received signal. This amplification level is maintained throughout the entire data packet.

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Irvine, CA, United States of America

Michael S Friedman