Frequency hopping time-diversity communications systems and transceivers

Abstract

A system utilizing adaptive frequency-hopped spread spectrum modulation to communicate over AC power lines and other noisy communications channels is described. The system employs a modulation structure in which individual packets of data are transmitted with FSK modulation using two frequencies chosen from a larger set. An error coding system is used which provides a controlling microprocessor with data on the quality of reception at each transceiver in the network; this information is used to alter the gain of the receiver, the bit rate of the transmission, and the specific frequencies employed by the network, in real time, to optimize communication error rate. Messages are organized in packets. A Master transceiver, controlling network management, transmits channel control information to other transceivers on the network, enabling system synchronization, acquisition of an existing network by new subscribers, and changes to the bit rate and frequency set in use. Each transceiver comprises a frequency controlled carrier generator, appropriate data keying for the carrier, a pair of digital detectors each having a frequency controlled bandpass filter connected thereto, appropriate microprocessors for control and broad band coupling networks for coupling the transceiver to a communications channel, which may be an AC power line, a private line, the floor loop of an automatic guided vehicle system, or the like.