Browse Prior Art Database

AC Cycle Phase Constant Noise Identification and Avoidance Method

IP.com Disclosure Number: IPCOM000104417D
Original Publication Date: 1993-Apr-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 2 page(s) / 94K

Publishing Venue

IBM

Related People

Cato, RT: AUTHOR

Abstract

When problems are encountered in communicating over the power lines, it is extremely useful to be able to identify the problem. Frequently, interfer ence of some kind is the problem as opposed to a weak signal. Quick identification of the source of the interference is the key to maintaining a reliable data link, and thus, a satisfied customer. This disclosure provides the customer or customer engineer with an automatic means of classifying the source of interference -- which is a very important step in finding and eliminating the interference. In other words, knowing the characteristics of the interference helps tremendously in identifying it and then eliminating it.

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AC Cycle Phase Constant Noise Identification and Avoidance Method

      When problems are encountered in communicating over the power
lines, it is extremely useful to be able to identify the problem.
Frequently, interfer ence of some kind is the problem as opposed to a
weak signal.  Quick identification of the source of the interference
is the key to maintaining a reliable data link, and thus, a satisfied
customer.  This disclosure provides the customer or customer engineer
with an automatic means of classifying the source of interference --
which is a very important step in finding and eliminating the
interference.  In other words, knowing the characteristics of the
interference helps tremendously in identifying it and then
eliminating it.

      This method of classifying interference as AC cycle phase
dependent requires that the AC cycle phase be known at the instant of
interference.  A common means of measuring AC cycle phase is relative
to the zero crossing of the AC cycle.  This disclosure holds with the
measurements being made relative to any place in the AC cycle, but
the zero crossing will be assumed to be the reference point.

      It is common for power line communication systems to
synchronize their transmissions with the AC cycle.  This is done in
order to transmit the data packets near the AC cycle zero crossing,
and therefore, attempt to avoid phase constant interference.  Thus,
the AC phase measurement hardware is typically available in power
communication systems.  Therefore, it would be easy for a competitive
power line communications system to duplicate this invention.

      When a transmitter actually transmits a packet, it "remembers"
to look for an acknowledgement from the receiver that the packet
arrived successfully.  This disclosure would have the transmitter
also remember the AC cycle phase information associated with each
packet.  The phase information could be a byte read from a constantly
counting counter that is reset every time the AC cycle crosses zero
volts.

      When an acknowledgement is not received from the addressed
receiver, the transmitter would log this fact, as well as the AC
cycle phase information of the lost packet.  After a suitable amount
of lost packet data is collected, the data would be analyzed to see
if an unusual percentage of packets are lost at a particular place in
the AC cycle.  Random interference would be uniformly spre...