Periodic interference avoidance in a wireless radio frequency communication system

• US 5,574,979 A
• Filed: 06/03/1994
• Issued: 11/12/1996
• Est. Priority Date: 06/03/1994
• Status: Expired due to Term

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Norand Corporation (Baker Hughes Company)
• Inventors: West, Guy J.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): Nguyen, Lee
• Application Number:
  US08/253,791
• Time in Patent Office: 893 Days
• Field of Search: 455/63, 455/67.5, 455/50.1, 455/51.1, 455/9, 455/54.1, 455/67.3, 455/67.1, 455/67.6, 455/295, 455/296, 455/298, 455/299, 455/226.1, 455/218, 455/222, 455/223 , 455/224, 455/38.2, 375/357, 375/346, 375/354, 375/356, 370/95.1, 219/715, 219/716
• US Class Current: 455/63.1
• CPC Class Codes: H04B 1/1027 assessing signal quality or detecting noise/interference for the received signal
• CPC Class Codes: H04L 2007/045 Fill bit or bits, idle words
• CPC Class Codes: H04L 7/027 extracting the synchronising or clock signal from the received signal spectrum, e.g. by using a resonant or bandpass circuit
• CPC Class Codes: H04L 7/046 using a dotting sequence
• CPC Class Codes: H04W 52/46 in multi hop networks, e.g. wireless relay networks

Abstract

A hierarchical communication system is described whereby periodic interference can be detected and avoided utilizing constituents'"'"' computer controllers and sync signals generated in response to the interference. The use of a predictive sync signal allows radio frequency communication to be optimally timed to efficiently make use of the interference-free time within the periodic interference signal.

Claims

1. A system for transmitting and receiving radio frequency communication in an environment where there is periodic interference, comprising:

(a) means for transmitting a communications message via wireless radio frequency communication;

(b) sync means comprising;

(b1) sensing means for sensing periodic interference; and

(b2) means, coupled with said sensing means, for generating a sync signal that tracks an alternating current associated with a power main which is representative of the timing of said periodic interference and controlling said transmitting means to effect radio frequency transmission of a communication message according to the sync signal, so as to tend to avoid errors in radio frequency communication due to said periodic interference.

2. The system of claim 1, comprising a user supported terminal and a radio base station, each having sync means and means for transmitting and receiving communication messages via wireless radio frequency communication.

3. The system of claim 2, wherein the user supported terminal and the radio base station each include sync circuit means and controlling means, comprising a computer controller, for controlling transmission of communication messages to tend to avoid errors in radio frequency communication due to said periodic interference.

4. The system of claim 3, wherein the respective sync circuit means of the user supported terminal and the radio base station is coupled to the respective computer controller means of the user supported terminal and the radio base station to supply the respective sync signal thereto, so that two way transmission of communications messages tends to avoid errors due to periodic interference.

5. The system of claim 4, wherein the computer controller means of the user supported terminal and the radio base station determine whether to inhibit radio frequency communication based on communication error rates.

6. The system of claim 1, wherein radio frequency communication occurs in the 2.4 gigahertz band.

7. The system of claim 1, wherein the sync signal has first and second logic levels corresponding to periodic interference, and said transmitting means is controlled to effect radio frequency communication a relatively short fixed time after the sync signal shifts to the second logic level corresponding to an absence of interference, and to inhibit radio frequency communication a relatively short fixed time before the sync signal shifts to the first logic level corresponding to the presence of interference.

8. The system of claim 1, wherein the sync means includes a sync waveform generator means for generating the sync signal, and the sync waveform generator means is an analog integrated circuit.

9. The system of claim 1, wherein the sensing means comprises a receiving loop means for sensing said periodic interference.

10. The system of claim 1, wherein the periodic interference is generated by ac powered microwave oven magnetrons.

11. The system of claim 1, wherein the sensing means senses said periodic interference by coupling directly to an ac power line.

12. A method of transmitting and receiving wireless communication in an environment where there is periodic and non-periodic interference, comprising the steps of:

sensing interference;

generating a sync waveform that tracks an alternating current signal associated with a power main;

determining whether the sensed interference tracks the sync waveform; and

selectively conducting wireless communication if the sensed interference tracks the sync waveform, so as to tend to avoid communication errors due to said periodic interference.

13. The method of claim 12, wherein wireless communication comprises radio frequency transmission in the 2.4 gigahertz band.

14. The method of claim 12, wherein the step of generating a sync waveform is performed by an integrated circuit.

15. The method of claim 12, wherein the step of sensing interference is performed utilizing a receiving loop.

16. The method of claim 12, wherein the periodic interference is generated by a microwave oven.

17. The method of claim 12, wherein the step of sensing interference is performed by coupling with the power main.

18. A wireless communication device comprising:

a receiver that wirelessly receives messages and detects interference;

a transmitter that wirelessly transmits messages;

a synchronization circuit that tracks an alternating current cycle associated with a power main;

a controller which interacts with said receiver and said transmitter pursuant to a communication protocol for managing exchanges of messages;

said controller coordinates with said synchronization circuit and said receiver to identify periodic interference that is synchronous with the alternating current cycle associated with the power main; and

said controller adapting said protocol for operation when periodic interference is identified.

19. The wireless communication device of claim 18 wherein the period interference is generated by an external device that connects to the power main.