Non-coherent spread-spectrum continuous-phase modulation communication system

• US 5,754,584 A
• Filed: 06/07/1995
• Issued: 05/19/1998
• Est. Priority Date: 09/09/1994
• Status: Expired due to Term

• Current Assignee: Intel Corporation, Omnipoint Technologies, Inc. (Intel Corporation)
• Original Assignee: Omnipoint Corp. (Deutsche Telekom AG)
• Inventors: Scott, Logan, Jensen, Ryan N., Williams, Claude M., Durrant, Randolph L., Burbach, Mark T.
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): GLUCK, JEFFREY WILLIAM
• Application Number:
  US08/480,443
• Time in Patent Office: 1,077 Days
• Field of Search: 375/206, 375/208, 375/209, 375/210, 375/336, 375/274, 375/305, 375/343
• US Class Current: 375/142
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/708 Parallel implementation
• CPC Class Codes: H04B 1/7093 Matched filter type
• CPC Class Codes: H04B 2201/70701 featuring pilot assisted reception
• CPC Class Codes: H04J 13/10 Code generation
• CPC Class Codes: H04J 14/005 Optical Code Multiplex
• CPC Class Codes: H04L 27/2014 in which the phase changes in a piecewise linear manner during each symbol period, e.g. minimum shift keying, fast frequency shift keying H04L27/201 takes precedence
• CPC Class Codes: H04L 27/2278 using correlation techniques, e.g. for spread spectrum signals
• CPC Class Codes: H04L 27/2332 using a non-coherent carrier

Abstract

A technique for modulating and demodulating CPM spread spectrum signals and variations of CPM spread spectrum signals. A spread spectrum transmitter includes a chip sequence generator for generating a chip sequence from a data stream, a switch for dividing said chip sequence into an odd chip sequence and an even chip sequence, and a modulator for generating and transmitting a continuous phase modulated signal from said odd chip sequence and said even chip sequence. A spread spectrum receiver comprises a plurality of non-coherent serial CPM correlators, each generating a correlation signal. In a preferred embodiment, the chip sequence generator of the transmitter comprises a table of symbol codes, each symbol code comprising a series of chips corresponding to a unique series of bits in said data stream, and each non-coherent serial CPM correlator is configured to detect one of the symbol codes. The spread spectrum receiver selects a data symbol based on said correlation signals output from the non-coherent serial CPM correlators. A spread spectrum preamble may be used to set initial timing for the non-coherent serial CPM correlators.

Claims

1. A spread spectrum communication system comprising:

a spread spectrum transmitter and a spread spectrum receiver, said spread spectrum transmitter comprising;

a chip sequence generator for generating a chip sequence from a data stream, said chip sequence generator comprising a table of symbol codes, each symbol code comprising a series of chips corresponding to a unique series of bits in said data stream, said chip sequence generator further comprising means for generating at least one spread spectrum fill code chip sequence,

a switch for dividing said chip sequence into an odd chip sequence and an even chip sequence, and

a modulator for generating and transmitting a continuous phase modulated signal from said odd chip sequence and said even chip sequence; and

said spread spectrum receiver comprising;

means for despreading said spread spectrum signal using a plurality of non-coherent serial CPM correlators to generate a plurality of correlation signals, one for each one of said plurality of non-coherent serial CPM correlators, and

means for selecting a data symbol based on said correlation signals.

2. A spread spectrum communication system as in claim 1 wherein:

said spread spectrum receiver comprises

means for despreading said continuous phase modulated signal without reference to an synchronization signal external to said spread spectrum receiver.

3. The spread spectrum communication system of claim 1 wherein said spread spectrum fill code chip sequence comprises an alternating pattern of ones and zeroes.

4. A spread spectrum communication system comprising:

a spread spectrum transmitter and a spread spectrum receiver, said spread spectrum transmitter comprising;

a chip sequence generator for generating a chip sequence from a data stream, said chip sequence generator comprising means for generating a spread spectrum preamble,

a switch for dividing said chip sequence into an odd chip sequence and an even chip sequence, and

a modulator for generating and transmitting a continuous phase modulated signal from said odd chip sequence and said even chip sequence; and

said spread spectrum receiver comprising;

means for despreading said spread spectrum signal using a plurality of non-coherent serial CPM correlators to generate a plurality of correlation signals, one for each one of said plurality of non-coherent serial CPM correlators,

means for selecting a data symbol based on said correlation signals, and

a non-coherent CPM correlator for correlating said spread spectrum preamble, said non-coherent CPM correlator generating a preamble correlation signal establishing chip timing for said plurality of non-coherent serial CPM correlators.

5. The spread spectrum communication system as in claim 4 wherein

said spread spectrum receiver comprises

a plurality of non-coherent CPM correlators, each non-coherent CPM correlator configured to detect one of said symbol codes without reference to an synchronization signal external to said receiver and without tracking a carrier signal.

7. The spread spectrum communication system of claim 5 wherein said spread spectrum receiver further comprises a preamble correlator configured to detect said spread spectrum preamble, said preamble correlator generating a preamble correlation signal establishing chip timing for said plurality of non-coherent CPM correlators.

6. A spread spectrum communication system comprising:

a spread spectrum transmitter and a spread spectrum receiver, said spread spectrum transmitter comprising

a table of symbol codes,

a data stream connected to said table of symbol codes, whereby a symbol code is output for each set of data bits in said data stream,

a chip sequence comprising symbol codes output from said symbol table,

a spread spectrum preamble generator having as an output a spread spectrum preamble, wherein said chip sequence further comprises said spread spectrum preamble,

a switch connected to said chip sequence,

an odd chip sequence output from said switch,

an even chip sequence output from said switch, and

a modulator connected to said odd chip sequence and to said even chip sequence, said modulator outputting a continuous phase modulated signal; and

said spread spectrum receiver comprising

a plurality of non-coherent CPM correlators, each non-coherent CPM correlator configured to detect one of said symbol codes,

a plurality of correlation signals, one output from each of said plurality of non-coherent CPM correlators, and

a selector connected to said correlation signals, said selector outputting a data symbol based on said correlation signals.

8. A method of spread spectrum communication comprising the steps of:

receiving a data signal;

selecting, from among a set of spread spectrum codes, a spread spectrum code for each predefined number of data bits in said data signal, and forming a chip sequence thereby;

dividing a preamble chip sequence into an odd preamble chip sequence and an even preamble chip sequence;

generating a continuous phase modulated preamble signal from said odd preamble chip sequence and said even preamble chip sequence;

transmitting said continuous phase modulated preamble signal;

dividing said chip sequence into an odd chip sequence and an even chip sequence;

generating a continuous phase modulated signal from said odd chip sequence and said even chip sequence;

transmitting said continuous phase modulated signal following said continuous phase modulated preamble signal;

receiving said continuous phase modulated preamble signal;

non-coherently correlating said continuous phase modulated preamble signal and generating a serial correlator clock signal thereby;

despreading said continuous phase modulated signal, said step of despreading including the step of simultaneously correlating said continuous phase modulated signal against each spread spectrum code in said set of spread spectrum codes using said serial correlator clock signal;

generating a plurality of correlation signals; and

selecting a data symbol based upon a comparison of said correlation signals.