Frequency hopping spread spectrum data communications system

In a radio frequency data communication system of the type comprising at least a plurality of base stations and a plurality of terminals, said system employing a media access protocol of the type that defines a plurality of discrete time slots generated locally at each of said plurality of terminals and at each of said plurality of base stations in response to a slot synchronizing signal broadcast from each said base station, the improvement comprising in combination therewith:

• a frequency hopping spread spectrum transmitter at each said base station for transmitting an information signal for a predetermined hop period on each of a predetermined plurality of channels, in a particular predetermined sequence selected from a set of predetermined sequences, each of said predetermined plurality of channels being associated on a one-to-one basis with one of a plurality of distinct channel numbers and corresponding on a one-to-one basis with one of a predetermined plurality of distinct carrier frequencies,
• time mark generating means at each said base station for generating a time mark frame that is provided as at least a part of said information signal for at least some of said plurality of channels, said time mark frame including information for synchronizing a receiver at each of said plurality of terminals to receive said information signal on each of said predetermined plurality of channels in said particular predetermined sequence;
• terminal slot synchronizing means at each of said plurality of terminals for defining the start of a next one of said discrete time slots a predetermined period of time after receipt of each said time mark frame;
• whereby said time mark frame serves as said slot synchronizing signal and synchronizes both said discrete time slots and said particular predetermined sequence of said plurality of channels between each said base station and said plurality of terminals.

In a radio frequency data communication system of the type comprising at least a plurality of base stations and a plurality of terminals, said system employing a media access protocol of the type that defines a plurality of discrete time slots generated locally at each of said plurality of terminals and at each of said plurality of base stations in response to a slot synchronizing signal broadcast from each said base station, the improvement comprising in combination therewith:

• a frequency hopping spread spectrum transmitter at each said base station for transmitting an information signal for a predetermined hop period on each of a predetermined plurality of channels, in a particular predetermined sequence selected from a set of predetermined sequences, each of said predetermined plurality of channels being associated on a one-to-one basis with one of a plurality of distinct channel numbers and corresponding on a one-to-one basis with one of a predetermined plurality of distinct carrier frequencies, each member of said set of predetermined sequences being a sequence, Z.sub.1, Z.sub.2, Z.sub.3 . . . Z.sub.Y-1, for which said channel number is defined by a multiplicative generator of the form
• Z.sub.i+1 =(XZ.sub.i) MOD (Y)
• where Y is a positive prime integer and X is positive integer chosen from the set consisting of [2,3,5,8,12,14,18,19,20,21,22,26].
• time mark generating means at each said base station for generating a time mark frame that is provided as at least a part of said information signal for at least some of said plurality of channels, said time mark frame including information for synchronizing a receiver at each of said plurality of terminals to receive said information signal on each of said predetermined plurality of channels in said particular predetermined sequence;
• terminal slot synchronizing means at each of said plurality of terminals for defining the start of a next one of said discrete time slots a predetermined period of time after receipt of each said time mark frame;
• whereby said time mark frame serves as said slot synchronizing signal and synchronizes both said discrete time slots and said particular predetermined sequence of said plurality of channels between each said base station and said plurality of terminals.

A terminal for use in communicating with at least one base station in a wireless radio frequency data transmission network comprising in combination:

• a radio receiver;
• a radio transmitter;
• tuning means connected to said radio receiver for selectively tuning its receive frequency response to a frequency control signal and connected to said radio transmitter for selectively changing its transmit frequency in response to said frequency control signal;
• a modulator having a digital input, said modulator being connected to said radio transmitter to selectively vary said transmit frequency in response to a digital transmit data signal at said digital input;
• a demodulator having a digital output, said demodulator being connected to said radio receiver to provide a received digital signal on said digital output in response to variations in said receive frequency;
• a terminal controller connected to a source of terminal input data and said modulator for providing a terminal request to send signal and said digital transmit data signal in response to operation of said source of terminal input data;
• a low power controller connected to said demodulator, said terminal controller, and to said radio transmitter
• for monitoring data packets from said digital output for a time mark frame addressed to said low power controller and for providing said frequency control signal to said tuning means in response to information in said time mark frame, and
• for powering up at least a portion of said radio transmitter in response to said terminal request to send signal, to maintain said portion of said radio transmitter in a powered up condition while said terminal controller is providing said digital transmit data signal, and to otherwise power down said portion of said radio transmitter.

A terminal for use in communicating with at least one base station in a wireless radio frequency data transmission network comprising in combination:

• a radio receiver;
• tuning means connected to said radio receiver for selectively tuning its receive frequency in response to a frequency control signal to provide a received signal;
• a demodulator having a digital output, said demodulator being connected to said radio receiver and said tuning means to provide a received digital signal on said digital output in response to variations in said received signal;
• a low power controller connected to said demodulator and to said radio receiver
• for monitoring said received digital signal from said digital output for a time mark signal and for providing said frequency control signal to said tuning means in response to information in said time mark signal,
• for timing a predetermined hop time interval commencing with its detection of said time mark signal,
• for monitoring said received digital signal from said digital output for an end of message signal;
• for powering down at least a portion of said radio receiver for at least a portion of the remainder of said hop time interval in response to receipt of said end of message signal.

A terminal for use in communicating with a plurality of base stations in a wireless radio frequency data transmission network comprising in combination:

• a radio receiver;
• tuning means connected to said radio receiver for selectively tuning its receive frequency in response to a frequency control signal to provide a received signal;
• level detection means connected to said tuning means for providing a a level signal indicative of the power of said received signal;
• a demodulator having a digital output, said demodulator being connected to said radio receiver and said tuning means to provide a received digital signal on said digital output in response to variations in said received signal;
• a low power controller connected to said demodulator, said radio receiver, and said level detection means
• for monitoring said received digital signal from said digital output for a time mark signal and for providing said frequency control signal to said tuning means in response to information in said time mark signal,
• for timing a predetermined hop time interval commencing with its detection of said time mark signal,
• for monitoring said received digital signal from said digital output for an end of message signal;
• for powering down at least a portion of said radio receiver for at least a portion of the remainder of said hop time interval in response to receipt of said end of message signal when said level signal is above a predetermined threshold value, and alternately for changing said frequency control signal and monitoring said received digital signal on a different channel for an occurrence of said time mark signal for at least said portion of said remainder of said hop time interval in response to receipt of said end of message signal when said level signal is below a predetermined threshold value.