US 4,583,231 A · Method of, and apparatus for, frequency-hopped frequency-shift-keyed digital data communications

Abstract

A digital data communications method and system combining frequency agility with a frequency-shift-keyed signal to transmit a unique code word representing a plurality of data states. Each code word comprises a plurality of chips, each of which is an integer subportion of the bit time interval in which one data bit is communicated. The multiple-chip word provides a frequency-hopped spread spectrum signal in which the nominal carrier frequency value is offset for transmitting binary data, or is offset in either frequency direction by different discrete amounts for transmitting multilevel digital data, to allow the data value to be properly decoded at a receiver even if the transmitter instantaneous frequency during at least one chip time interval is jammed by another signal. The frequency offset, can also be provided in complementary fashion during selected chip time intervals to even further encode the data bit being communicated and further reduce the probability of jamming. The multiple-chip code word, of normal or selected-chip-complemented form, modulates a carrier at the transmitter end. The FH-FSK carrier is demodulated at the receiver end by an inverse modulation process which converts the signal into a serial bit stream, for matched filtering transmission and reception apparatus of non-complemented and/or complemented chip-encoded words is described.

Claims38

Dependent claims

A method for the transmission of digital data, comprising the steps of:

(a) assigning one of a plurality of sequential bit time intervals (BTIs) for the transmission of an associated bit of data in a sequential stream of a like plurality of digital data bits;
(b) separating each BTI into the same number of a sequential plurality C, where C is an integer greater than 1, of successive chip time intervals (CTIs);
(c) designating a plurality N, wherein N is an integer greater than 1, of known nominal signal frequencies for transmission of data;
(d) substantially permanently assigning a predeterminately-selected, and different, one of the plurality N of known nominal transmission frequencies for utilization during each associated and like-positioned one of the plurality C of chip time intervals and with the same sequence of C frequencies for all BTIs;
and
(e) transmitting a signal with an output frequency which differs from the associated known nominal transmission frequency of each sequential CTI of that particular BTI by an offset frequency responsive to that one data value, of a plurality of possible digital data values, to be transmitted in a particular BTI.

3 more elements

Apparatus for digital data communications over a transmissions medium, comprising:

(I) at least one transmitter means for providing a data transmission signal to said transmission medium, each transmitter means including:
(a) means for assigning one of a plurality of sequential bit time intervals (BTIs) for the transmission of an associated bit of data in a sequential stream of a like plurality of digital data bits;
(b) means for separating each BTI into a sequential plurality C of the same number of successive chip time intervals (CTIs);
(c) means for generating an instantaneous transmission signal frequency within a predetermined frequency range;
(d) means for designating a plurality N of known nominal signal frequencies, within said preselected frequency range, for data transmission;
(e) means for substantially permanently assigning a predetermined different one of the plurality N of known nominal transmission frequencies designated by said designating means (1d) for utilization during each associated one of the plurality C of chip time intervals and with the same sequence of C frequencies for all BTIs;
(f) means for designating an offset frequency;
responsive to the particular one of a plurality of digital data values to be transmitted in a particular BTI, for modification of the nominal transmission frequency assigned by said assigned means, (1e) to cause said generating means to provide an output signal frequency for coupling to said transmission medium during each sequential CTI of each particular BTI;
and
(II) at least one receiver means coupled to said transmission medium for recovering the digital data value of each actual frequency signal received from said medium.

7 more elements

Dependencies are inferred from the claim text.

Method of, and apparatus for, frequency-hopped frequency-shift-keyed digital data communications

Life of this patent

Method of, and apparatus for, frequency-hopped frequency-shift-keyed digital data communications

Life of this patent

Abstract

Claims38