Method and apparatus for diversity enhancement using pseudo-multipath signals

• US 5,991,345 A
• Filed: 09/22/1995
• Issued: 11/23/1999
• Est. Priority Date: 09/22/1995
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Ramasastry, Jayaram
• Primary Examiner(s): Vo, Don N.
• Application Number:
  US08/532,452
• Time in Patent Office: 1,523 Days
• Field of Search: 375/200, 375/205, 375/206, 375/211, 375/260, 375/267, 375/316, 375/347, 370/18, 370/104.1, 370/97, 370/316, 370/317, 370/320, 370/342, 455/7, 455/12.1, 455/52.1, 455/52.3, 455/65, 455/11.1, 455/13.1, 455/277.1, 455/277.2, 455/133-135
• US Class Current: 375/347
• CPC Class Codes: H04B 7/18534 for enhancing link reliablility, e.g. satellites diversity

Abstract

Method and apparatus for enhancing diversity in spread spectrum type communication systems by creating pseudo-multipath conditions or links for certain communication signals. The invention provides alternative or additional signal paths, for signals being transferred between gateways and communication system users through one or more a satellite repeaters. These additional paths are used to establish and maintain adequate signal diversity as well as certain signal links by remote subscribers in heavy urban areas. In further aspects of the invention, diversity enhancers can employ high gain parabolic antennas and tracking mechanisms, or passive reflective surfaces. Signals can be relayed to subscriber units in canyon type blocked areas or within structures.

Claims

1. Apparatus for providing signal diversity in a spread spectrum communication system, comprising:

at least one source for transmitting a CDMA communication signal;

at least one diversity enhancer, each for generating at least one pseudo-multipath signal from said source; and

a subscriber unit in diversity reception directly with said at least one source and with said at least one diversity enhancer.

2. Apparatus of claim 1 wherein said at least one source for transmitting a CDMA communication signal comprises at least one satellite.

3. Apparatus of claim 1 wherein said at least one source for transmitting a CDMA communication signal comprises at least one terrestrial-based repeater.

4. Apparatus of claim 1 wherein said at least one diversity enhancer comprises:

means for receiving said communication signal from said at least one source;

means for immediately transmitting said CDMA communication signal to said subscriber unit;

means for delaying said communication signal by a predetermined amount of delay; and

means for transmitting said delayed CDMA communication signal to said subscriber unit.

5. Apparatus of claim 4 wherein said predetermined amount of delay is substantially equal to a spreading code chip period.

6. Apparatus of claim 4 further comprising a controller for dynamically adjusting said predetermined amount of delay.

7. Method for providing signal diversity in a spread spectrum communication system, comprising the step of:

transmitting a CDMA communication signal by at least one source;

receiving said CDMA communication signal by at least one diversity enhancer and transmitting said CDMA communication signal to a subscriber unit capable of diversity mode reception to provide at least one psuedo-multipath signal to said subscriber unit; and

receiving said CDMA communication signal directly from said at least one source and from said diversity enhancer, said CDMA communication signal from said diversity enhancer being received at a time later than said CDMA communication signal from said at least one source.