High bit rate infrared communication system for overcoming multipath

• US 5,371,623 A
• Filed: 07/01/1992
• Issued: 12/06/1994
• Est. Priority Date: 07/01/1992
• Status: Expired due to Fees

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Alameh, Rachid, Eastmond, Bruce C., Freeburg, Thomas A.
• Primary Examiner(s): Safourek, Benedict V.
• Application Number:
  US07/907,468
• Time in Patent Office: 888 Days
• Field of Search: 359/137, 359/138, 359/157, 359/161, 359/164, 359/165, 359/167, 359/189, 359/353, 359/118, 455/52.1, 455/52.3, 455/133, 455/134, 455/135, 455/137, 375/100, 375/101
• US Class Current: 398/27
• CPC Class Codes: H04B 10/1149 Arrangements for indoor wireless networking of information

Abstract

A wireless infrared (IR) communications system (100) for communicating packetized information (302) between a control module (12) and a plurality of UMs (14) via infrared transceivers (300/320) is described as having a selectable communications path. In this system at least the user module (14) has a plurality of IR device arrays (A1-A6) for receiving IR signals (312/312'"'"') in relatively narrow IR field of view sectors, and selection circuit (20), coupled to said plurality of IR device arrays (A1-A6), for selecting a communication path between the control module (12) and one of said plurality of IR device arrays (A1-A6), based at least partly on received signal (302'"'"') qualtity, so as to overcome reception errors caused by multipath interference.

Claims

1. For use in a infrared (IR) communication system having a first terminal and a second terminal for communicating data there between by means of a light signal communication path, such communication being subject to substantial multipath interference caused by the reception of multiple signals having differential path delays exceeding a substantial fraction of the data symbol duration, at least a first terminal, comprising:

a plurality of IR device arrays for receiving IR signals in relatively narrow IR field of view sectors; and

selection means, coupled to said plurality of IR device arrays, for selecting one of said plurality of IR device arrays, based at least partly on received IR signal quality, so as to overcome reception errors caused by multipath interference.

2. The terminal of claim 1 wherein said plurality of IR device arrays comprise photon-to-current converters.

3. The terminal of claim 1 wherein each IR device array is arranged to provide a uniform pattern of IR coverage within the IR field of view sector.

4. The terminal of claim 1 wherein each IR device array defines a 60°

field of view sector.

5. The terminal of claim 1 wherein the plurality of IR device arrays defines a 360°

field of view.

6. The terminal of claim 1 wherein the selection means is a switch.

7. The terminal of claim 1 wherein the selection means includes memory means for continually tracking a best communication path.

8. The terminal of claim 1 further comprising circuit means for demodulating the received IR signals to detect communicated data;

and means, coupled to the demodulating means for detecting a bit error rate (BER) for the communicated data.

9. The terminal of claim 8 wherein received signal quality, is determined as a function of the detected bit error rate (BER).

10. A wireless IR communications system including a control module and at least one user module capable of communicating packetized information to the control module via communication paths, the user module comprising:

a plurality of IR device arrays for receiving IR signals from the control module in relatively narrow IR field of view sectors;

means, coupled to the plurality of IR device arrays, for determining the quality of the IR signals received by each of the plurality of IR device arrays;

means, coupled to the determining means, for ranking the quality of the IR signals received by each one of the plurality of IR device arrays; and

selection means, coupled to the ranking means, for selecting one of said plurality of IR device arrays, based at least partly on the ranking, so as to overcome reception errors caused by multipath interference.

11. The user module according to claim 10 further comprising means for periodically generating new rankings based on new determinations of signal quality.

12. The user module according to claim 10 wherein the means for determining the quality of signal received from the control module is a Bit Error Detector.

13. In wireless IR communications system wherein packetized data is communicated between a control module and at least one user module via a plurality of IR device arrays, such communication being subject to substantial multipath interference caused by the reception of multiple signals having differential path delays exceeding a substantial fraction of the data symbol duration, a method for choosing one IR device array from among a plurality of IR device arrays coupled to the user module comprising the steps of:

selecting each IR device array from among a plurality of IR device arrays that cover different geographic areas relative to the user module;

determining the quality of data signals received from the control module on each of said IR device arrays;

ranking each of said IR device arrays according to the determined quality; and

selecting a particular IR device array from among the plurality and for use in communicating with the control module based on the highest ranking.