Data transmission over a power line communications system

• US 5,828,293 A
• Filed: 06/10/1997
• Issued: 10/27/1998
• Est. Priority Date: 06/10/1997
• Status: Expired due to Term

• Current Assignee: RPX Clearinghouse LLC (RPX Corporation)
• Original Assignee: Northern Telecom Limited (Nortel Networks Corporation)
• Inventors: Rickard, Robin Paul
• Primary Examiner(s): Wu, Daniel J.
• Application Number:
  US08/871,930
• Time in Patent Office: 504 Days
• Field of Search: 340/310.01, 340/310.03, 340/310.04, 375/259, 375/257, 375/258, 375/295, 455/3.3, 455/63, 455/66, 455/402
• US Class Current: 375/257
• CPC Class Codes: H04B 2203/542 using zero crossing information
• CPC Class Codes: H04B 2203/5425 improving S/N by matching impedance, noise reduction, gain control
• CPC Class Codes: H04B 2203/5445 Local network
• CPC Class Codes: H04B 2203/5458 Monitor sensor; Alarm systems
• CPC Class Codes: H04B 2203/5466 using three phases conductors
• CPC Class Codes: H04B 2203/5483 using coupling circuits
• CPC Class Codes: H04B 2203/5495 having measurements and testing channel
• CPC Class Codes: H04B 3/542 the information being in digital form

Abstract

A power line communications system has at least one power line upon which noise level varies with time. The system determines quiet periods when noise upon the line is at a reduced level and transmits one or more data packets within the quiet periods, so as to increase data throughput in the system.

Claims

1. A method of transmitting data in a power line communications system comprising a power line upon which noise level varies with time, the power line comprising a plurality of different phase lines, there being a plurality of subscriber stations coupled to the phase lines, the method comprising:

determining quiet periods when noise upon the phase lines is at a reduced level; and

transmitting data packets over the power line to subscriber stations, each packet being transmitted within a single one of the determined quiet periods, wherein each of the packets is preferentially transmitted to a subscriber station on a phase line during a quiet period occurring on that phase line.

2. A method according to claim 1 wherein the power line carries a periodic power signal, the quiet periods being located about a characteristic point of the power signal, and wherein the step of determining a quiet period comprises determining the quiet period based on the timing of the characteristic point.

3. A method according to claim 2 wherein the power signal is an alternating power signal which has a plurality of zero-crossing points, the quiet periods extending each side of the zero-crossing points, and the step of transmitting comprises transmitting the data packet such that it extends in time each side of the zero-crossing point.

4. A method according to claim 3 wherein the data packet is transmitted such that it extends unequally each side of the zero-crossing point.

5. A method according to claim 2 wherein the step of determining quiet periods comprises predicting future quiet periods based on the periodic nature of the power signal.

6. A method according to claim 2 further comprising monitoring noise level on the line and determining the quiet period based on the timing of the characteristic point and the monitored noise.

7. A method according to claim 1 wherein the power line comprises n phase lines, each power signal has a period T, and the step of transmitting comprises transmitting over a particular phase line within the quietest duration T/n on that line.

8. A method according to claim 1 further comprising sequentially transmitting to subscribers coupled to different phase lines, one at a time, in a cyclic fashion.

9. A method according to claim 1 wherein the method is performed at a base station and the base station determines the phase line to which a subscriber station is coupled by:

instructing the subscriber station to transmit a test signal, and

monitoring quality of the test signal received on each phase line at the base station.

10. A method according to claim 1 wherein the power line comprises a plurality of phase lines which each carry a power signal, the power signals being offset from one another by a predetermined phase relationship, and wherein the step of determining quiet periods comprises monitoring a first phase line and determining quiet periods on other phase according to the monitoring of the first phase line and the predetermined phase relationship.

11. A method according to claim 1 wherein the data packet contains a token and the step of transmitting comprises transmitting the packet such that the token is transmitted during the quietest portion of the determined quiet period.

12. A method according to claim 1 wherein the step of transmitting comprises transmitting a downstream packet from a first station to a second station and an upstream packet from the second station to the first station during the determined quiet period.

13. A method according to claim 1 wherein the step of determining a quiet period comprises monitoring a power supply line to a transmitting station.

14. A method according to claim 1 wherein the step of determining a quiet period comprises monitoring noise level on the line.

15. A method according to claim 13 further comprising identifying, from the monitored noise level on the line, a periodic noise pattern and predicting future quiet periods based on the identified pattern.

16. A method of operating a communications transmitting station in a power line communications system comprising a power line upon which noise level varies with time, the power line comprising a plurality of different phase lines, there being a plurality of subscriber stations coupled to the phase lines, the method comprising:

determining quiet periods when noise upon the phase lines is at a reduced level; and

transmitting data packets over the power line to subscriber stations, each packet being transmitted within a single one of the determined quiet periods, wherein each of the packets is preferentially transmitted to a subscriber station on a phase line during a quiet period occurring on that phase line.

17. A transmitting station apparatus for use in a power line communications system comprising a power line upon which noise level varies with time, the power line comprising a plurality of different phase lines, there being a plurality of subscriber stations coupled to the phase lines;

the apparatus comprising;

means for determining quiet periods when noise upon the phase lines is at a reduced level; and

,

means for transmitting data packets over the power line to subscriber stations, each packet being transmitted within a single one of the determined quiet periods, wherein each of the packets is preferentially transmitted to a subscriber station on a phase line during a quiet period occurring on that phase line.

18. A power line communications system comprising:

a power line upon which noise level varies with time, the power line comprising a plurality of different phase lines;

a plurality of subscriber stations coupled to the phase lines;

means for determining a quiet period when noise upon the phase lines is at a reduced level; and

,

means for transmitting data packets over the power line to subscriber stations, each packet being transmitted within a single one of the determined quiet periods, wherein each of the packets is preferentially transmitted to a subscriber station on a phase line during a quiet period occurring on that phase line.