Diversity for direct-sequence spread spectrum systems

• US 5,394,435 A
• Filed: 02/22/1994
• Issued: 02/28/1995
• Est. Priority Date: 12/29/1992
• Status: Expired due to Term

• Current Assignee: American Telephone & Telegraph Company (AT&T, Inc.)
• Original Assignee: AT&T Corporation (AT&T, Inc.)
• Inventors: Weerackody, Vijitha
• Primary Examiner(s): Barron, Jr., Gilberto
• Application Number:
  US08/200,090
• Time in Patent Office: 371 Days
• Field of Search: 375/1, 375/100, 375/102, 370/18, 455/52.3
• US Class Current: 375/144
• CPC Class Codes: H04B 7/0613 using simultaneous transmission H04B7/0686 takes precedence

Abstract

An invention for providing diversity for direct sequence spread spectrum wireless communication systems is presented. The invention provides a transmitting technique for communicating a first signal comprising one or more segments to a receiver with use of a plurality of M antennas. The first signal includes one or more signal segments. The technique comprises forming M copies of the first signal; for a segment of a signal copy, weighting each of two or more sub-segments of the segment with a distinct signal, wherein a sequence of the distinct weighting signals for the segment is distinct from sequences of signals weighting the same segment of one or more other signal copies; and for each of M weighted signal copies, transmitting a signal to the receiver using a distinct antenna, the transmitted signal based on the weighted signal copy. Illustratively, the first signal is a spread spectrum signal. Moreover, the process of weighting comprises applying a phase shift to a sub-segment. The invention further provides a receiving technique which comprises, for a copy of a received signal, despreading a segment of the received signs, demodulating a plurality of sub-segments of the despread signal segment, wherein each sub-segment is demodulated with use of one or more estimated communication channel characteristics corresponding to the sub-segment, and forming a summation signal reflecting a summation of a plurality of demodulated sub-segments. The receiving technique further comprises forming a signal reflecting a signal segment value, the formed signal based on one or more summation signals. The step of demodulating may precede the step of despreading in some embodiments.

Claims

1. A method of operating a direct-sequence spread spectrum transmitter for communicating a first signal to a receiver, said transmitter including a plurality of antennas, said first signal including one or more signal segments, the method comprising the steps of:

forming a plurality of second signals, each of the second signals formed based on two or more sub-segments of a given segment of the first signal and two or more corresponding weighting signals, wherein a sequence of weighting signals used in forming one of said second signals is distinct from one or more other sequences of weighting signals used in forming one or more other of said second signals; and

transmitting a plurality of signals each with a distinct antenna, wherein at least two of said plurality of transmitted signals represent second signals which are formed with use of distinct sequences of weighting signals.

2. The method of claim 1 wherein the step of forming a plurality of second signals comprises forming at least one of said second signals based on a sequence of two or more weighting signals, each of which two or more weighting signals equals unity, such that the two or more corresponding sub-segments of the first signal are unaltered.

3. The method of claim 1 wherein a second signal is formed by applying a phase shift to at least one sub-segment of the first signal, the phase-shift specified by a corresponding weighting signal.

4. The method of claim 1 wherein the first signal is a spread spectrum signal which reflects the product of an information signal and a signature sequence signal.

5. The method of claim 4 wherein a signal segment represents a discrete information signal value.

6. The method of claim 1 wherein the step of transmitting a plurality of signals comprises forming a spread spectrum signal which represents a product of a second signal and a signature sequence signal.

7. A direct-sequence spread spectrum transmitter for communicating a first signal to a receiver, said first signal including one or more signal segments, the transmitter comprising:

means for forming a plurality of second signals, each of the second signals formed based on two or more sub-segments of a given segment of the first signal and two or more corresponding weighting signals, wherein a sequence of weighting signals used in forming one of said second signals is distinct from one or more other sequences of weighting signals used in forming one or more other of said second signals;

a plurality of antennas; and

means for transmitting a plurality of signals each with a distinct antenna, wherein at least two of said plurality of transmitted signals represent second signals which are formed with use of distinct sequences of weighting signals.

8. The transmitter of claim 7 wherein the means for forming a plurality of second signals comprises means for forming at least one of said second signals based on a sequence of two or more weighting signals, each of which two or more weighting signals equals unity, such that the two or more corresponding sub-segments of the first signal are unaltered.

9. The transmitter of claim 7 wherein the means for forming a plurality of second signals comprises means for applying a phase shift to at least one sub-segment of the first signal, the phase-shift specified by a corresponding weighting signal.

10. The transmitter of claim 7 wherein the first signal is a spread spectrum signal which reflects the product of an information signal and a signature sequence signal.

11. The transmitter of claim 10 wherein a signal segment represents a discrete information signal value.

12. The transmitter of claim 7 wherein the means for transmitting a plurality of signals comprises means for forming a spread spectrum signal which represents a product of a second signal and a signature sequence signal.