Spread spectrum data communicator

• US 5,841,807 A
• Filed: 02/20/1996
• Issued: 11/24/1998
• Est. Priority Date: 07/20/1995
• Status: Expired due to Fees

• Current Assignee: Intracoastal System Engineering Corp.
• Original Assignee: Intracoastal System Engineering Corp.
• Inventors: Carroll, Sean C., Hannebauer, Robert S., Tan, Xu
• Primary Examiner(s): Chin, Wellington
• Assistant Examiner(s): Tran, Congvan
• Application Number:
  US08/604,095
• Time in Patent Office: 1,008 Days
• Field of Search: 375/206, 375/200, 375/202, 375/205, 375/207, 375/208, 375/295, 375/316, 375/367, 455/500, 455/91, 455/102, 455/103, 370/342, 370/320, 370/441, 370/479, 370/335
• US Class Current: 375/142
• CPC Class Codes: H04B 1/707 using direct sequence modulation

Abstract

In summary, the spread spectrum direct sequence communication system of the present invention has a plurality of transmitters for uni-directionally simultaneously transmitting, through a transmission medium to a single receiver, a plurality of data streams. Each transmitter transmits a single data stream. Each data stream comprises a plurality of direct sequence data packets. Each transmitter has a data collector, a data formatter, a transmission device, a transmission interface, and a power supply.

Claims

1. A spread spectrum direct sequence communication system comprising:

a plurality of transmitters for uni-directionally simultaneously transmitting through a transmission medium to a single receiver, a plurality of data streams, one data stream for each transmitter in said plurality of transmitters, each data stream comprising a plurality of direct sequence data packets,

each transmitter of said plurality of transmitters comprising a data collector, a data formatter, a transmission device, a transmission interface, and a power supply,

said data collector for collecting data and passing to said data formatter, said data formatter for formatting said data into a serial data packet comprising a preamble, a transmitter identity and said data, and said data formatter serially shifting said data packet into said transmission device,

said transmission device for XOR combination of said data packet with a fixed length, repeated pseudo random noise digital chip sequence at a first clock frequency, and modulation of a resulting pseudo noise signal with a carrier to a carrier centre frequency,

said transmission interface transmitting a resulting carrier modulated pseudo noise signal containing said data packet as said data stream from said transmission device into said transmission medium, whereby said data is transmitted at a constant data rate,

said signal receiver having a second clock frequency and comprising a linear front-end, a carrier demodulator for simultaneously demodulating a plurality of said carrier modulated pseudo noise signals containing said data packets, means for simultaneous detection of said pseudo noise signals, and means for simultaneous correlation of said pseudo noise signals with a replica of said pseudo noise signal,

said single receiver further comprising means for simultaneous reconstruction of said data packets, and means from stripping said data from said data packets once reconstructed.

2. The device of claim 1 wherein, when there is a difference between said first clock frequency and said second clock frequency, said means for reconstruction of said data packets comprises means for compensating for said difference between said first clock frequency and said second clock frequency.

3. The device of claim 1 wherein said data rate is equal to a repeat rate of said fixed length, repeated pseudo random noise digital chip sequence whereby a process gain for said fixed length, repeated pseudo random noise digital chip sequence is maximized.

4. The device of claim 1 wherein said means for simultaneous correlation of said pseudo noise signals with a replica of said pseudo noise signal over-samples said pseudo noise signals.

5. The device of claim 4 wherein said means for simultaneous correlation of said pseudo noise signals with a replica of said pseudo noise signal three times over-samples said pseudo noise signals.

6. The device of claim 1 wherein said means for simultaneous correlation of said pseudo noise signals with a replica of said pseudo noise signal comprises means for performing inner product calculations on said data streams.

7. The device of claim 1 wherein each of said data streams is separated in phase, and said means for simultaneous correlation of said pseudo noise signals with a replica of said pseudo noise signal correlates waveform shape and phase of said data streams with waveform shape and phase of said replica of said pseudo noise signal and generates an indicative output upon a matching correlation.

8. The device of claim 1 wherein said fixed length, repeated pseudo random noise digital chip sequence is a hierarchical pseudo noise bit sequence generated by a plurality of hierarchical pseudo noise generators whose respective output of pseudo noise sequences are XOR'"'"'d, whereby said fixed length, repeated pseudo random noise digital chip sequence is formed as a hierarchy of said pseudo noise sequences.

9. The device of claim 8 wherein said plurality of hierarchical pseudo noise generators comprises a first PN generator of length L emitting a PN sequence of length 2^L -1, at a first clock rate and a second PN generator of length K emitting a PN sequence of 2^K -1 at a second clock rate, and wherein said second clock rate is 1/(2^L -1) said first clock rate.

10. A spread spectrum direct sequence communication system comprising:

a plurality of transmitters for uni-directionally simultaneously transmitting through a transmission medium to a single receiver, a plurality of data streams, one data stream for each transmitter in said plurality of transmitters, each data stream comprising a plurality of direct sequence data packets,

each transmitter of said plurality of transmitters comprising a data collector, a data formatter, a transmission device, a transmission interface, and a power supply,

said data collector for collecting data and passing to said data formatter, said data formatter for formatting said data into a serial data packet comprising a preamble, a transmitter identity and said data, and said data formatter serially shifting said data packet into said transmission device,

said transmission device for XOR combination of said data packet with a fixed length, repeated pseudo random noise digital chip sequence at a first clock frequency, and modulation of a resulting pseudo noise signal with a carrier to a carrier centre frequency,

said transmission interface transmitting a resulting carrier modulated pseudo noise signal containing said data packet as said data stream from said transmission device into said transmission medium, whereby said data is transmitted at a constant data rate,

said signal receiver having a second clock frequency and comprising a linear front-end, a carrier demodulator for simultaneously demodulating a plurality of said carrier modulated pseudo noise signals containing said data packets, means for simultaneous detection of said pseudo noise signals, and means for simultaneous correlation of said pseudo noise signals with a replica of said pseudo noise signal,

said single receiver further comprising means for simultaneous reconstruction of said data packets, and means from stripping said data from said data packets once reconstructed,

and wherein said fixed length, repeated pseudo random noise digital chip sequence is a hierarchical pseudo noise bit sequence generated by a plurality of hierarchical pseudo noise generators whose respective output of pseudo noise sequences are XOR'"'"'d, whereby said fixed length, repeated pseudo random noise digital chip sequence is formed as a hierarchy of said pseudo noise sequences.

11. The device of claim 10 wherein said plurality of hierarchical pseudo noise generators comprises a first PN generator of length L emitting a PN sequence of length 2^L -1, at a first clock rate and a second PN generator of length K emitting a PN sequence of 2^K -1 at a second clock rate, and wherein said second clock rate is 1/(2^L -1) said first clock rate.

12. The device of claim 10 wherein, when there is a difference between said first clock frequency and said second clock frequency, said means for reconstruction of said data packets comprises means for compensating for said difference between said first clock frequency and said second clock frequency.

13. The device of claim 12 wherein said data rate is equal to a repeat rate of said fixed length, repeated pseudo random noise digital chip sequence whereby a process gain for said fixed length, repeated pseudo random noise digital chip sequence is maximized.

14. The device of claim 10 wherein said means for simultaneous correlation of said pseudo noise signals with a replica of said pseudo noise signal over-samples said pseudo noise signals.

15. The device of claim 14 wherein said means for simultaneous correlation of said pseudo noise signals with a replica of said pseudo noise signal three times over-samples said pseudo noise signals.

16. The device of claim 10 wherein said means for simultaneous correlation of said pseudo noise signals with a replica of said pseudo noise signal comprises means for performing inner product calculations on said data streams.

17. The device of claim 10 wherein each of said data streams is separated in phase, and said means for simultaneous correlation of said pseudo noise signals with a replica of said pseudo noise signal correlates waveform shape and phase of said data streams with waveform shape and phase of said replica of said pseudo noise signal and generates an indicative output upon a matching correlation.