Power line communications spread spectrum protocol

• US 5,903,594 A
• Filed: 04/16/1997
• Issued: 05/11/1999
• Est. Priority Date: 04/16/1997
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Hershey, John Erik, Hartman, Michael James, Van Stralen, Nick Andrew, Hoctor, Ralph Thomas, Saulnier, Emilie Thorbjorg, Korkosz, Richard August
• Primary Examiner(s): Ghebretinsae, Temesghen
• Assistant Examiner(s): PARK, ALBERT C
• Application Number:
  US08/838,215
• Time in Patent Office: 755 Days
• Field of Search: 340/870.02, 340/870.03, 340/870.06, 340/870.11, 340/310.01, 340/310.02, 340/310.06, 379/106.03, 379/106.05, 379/106.11, 379/106.07, 375/346, 375/200
• US Class Current: 375/130
• CPC Class Codes: H04B 1/69 Spread spectrum techniques
• CPC Class Codes: H04B 2203/5408 using protocols
• CPC Class Codes: H04B 2203/5416 by adding signals to the wave form of the power source
• CPC Class Codes: H04B 2203/5425 improving S/N by matching impedance, noise reduction, gain control
• CPC Class Codes: H04B 2203/5433 Remote metering
• CPC Class Codes: H04B 2203/5458 Monitor sensor; Alarm systems
• CPC Class Codes: H04B 3/546 Combination of signalling, telemetering, protection circuits for remote indication of supply or distribution network condition H02J13/00

Abstract

A spread spectrum protocol in a power line communication (PLC) system uses Harmonic Modulation (HM) as true spread spectrum modulation made up of a plurality of modulated tones spaced in frequency with equal distance between adjacent tones. The protocol incorporates the following modes:

"Conventional"--Master/Slave relation of meters to a common hub.

"Leap Frog"--performing data relay through locally elected/designated meters for relay to a central hub or a distributed set of concentrators.

"Alarm Channel"--reserving an HM signal set for meters to telemeter their configuration in a subnetwork after a power distribution network reconfiguration.

"Probing"--using HM polling to diagnose the location of a feeder fault.

"Derived Timing"--master derived timing for inbound message framing.

"Rate Adapting"--allocating a mix of number of HM channels to the outbound/inbound ratio according to message traffic control requirements and power line distribution topology.

"Priority/Noise Based Adapting"--allocating a different mix of number of HM channels to the outbound/inbound ratio based on message priority or noise conditions.

Claims

1. A protocol implemented in a spread spectrum power line communications (PLC) system for a power line exhibiting a carrier synchronous noise spectrum, said communications system comprising a plurality of meters, each of said meters including a respective transmitter for transmitting message bits on a power line, and at least one receiver in a central hub coupled to the power line for receiving messages transmitted by the transmitters, said protocol comprising the steps of:

synthesizing at a transmitter a waveform s_i (t) having M tones described by ##EQU2## where i is one of a plurality of different signals which may be transmitted simultaneously, f_ik represents a selected frequency, t represents time, and a_ik and b_ik represent fixed amplitude coefficients for the i-th waveform;

modulating at the transmitter the M tones with data;

interstitially inserting the M tones in the power line synchronous noise spectrum so as to be effectively disjoint with the noise spectrum; and

receiving the modulated M tones at the receiver, the transmission of data from the transmitters to the receiver being in a Master/Slave relation of meters to the receiver.

2. The PLC protocol of claim 1 wherein at least one of the meters includes an additional receiver and further comprising, at the receiver in the meter, the steps of:

receiving data from said transmitters in other meters;

collecting and storing received data;

reformatting the collected and stored data; and

relaying the reformatted collected and stored data to said at least one receiver in said central hub.

3. The PLC protocol of claim 1 wherein the meters are connected in a power distribution network which is reconfigurable into a plurality of potentially overlapping subnetworks, each subnetwork having at least one subnetwork concentrator, further comprising the steps of:

reserving a harmonic modulated (HM) signal set for said meters to telemeter their configuration in a subnetwork after a power distribution network reconfiguration; and

transmitting from a meter using the reserved HM signal set information indicating membership or desire for membership in a subnetwork by said meter after said power distribution network reconfiguration.

4. The PLC protocol of claim 1 wherein said central hub includes a transmitter and receiver, and further comprising the steps of:

polling meters with harmonic modulated signals from the central hub; and

receiving messages from polled meters by the central hub to determine location of a feeder fault.

5. The PLC protocol of claim 1 wherein said central hub includes a transmitter and receiver and each of the meters includes a receiver, said protocol further comprising the steps of:

receiving at a meter receiver an inbound signal from the central hub;

detecting marker bits in said signal to derive timing information for inbound message framing at the receiver; and

controlling start of outbound message timing from said meter in accordance with the derived timing information.

6. The PLC protocol of claim 1 wherein said central hub includes a transmitter and receiver and each of the meters includes a receiver, and further comprising the step of allocating a mix of harmonic modulation channels to act as outbound and inbound channels in an outbound/inbound ratio according to message traffic control requirements and power line distribution topology.

7. The PLC protocol of claim 6 further comprising the step of allocating a different mix of number of harmonic modulation channels to act as outbound and inbound channels, based on message priority or noise conditions.