Communications: electrical – Systems – Selsyn type
Reexamination Certificate
1999-12-20
2001-09-11
Wu, Daniel J. (Department: 2632)
Communications: electrical
Systems
Selsyn type
C340S315000, C340S870030, C375S213000, C375S213000
Reexamination Certificate
active
06288632
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to communications systems and more particularly to power line communications systems. Electric power companies typically have a service person visit customers and read a power meter to determine the amount of power consumed for billing purposes. This can become very cumbersome and time consuming with a large number of customers.
It would be beneficial for power companies to read electric power meters remotely. Power lines are wires that convey power signals from a power source, such as a power generation station to a power customer, such as a home or business. There are extant power lines to each customer's power meter and these are advantageously configured for communicating data between a power company and power meters. However, conventional modulation techniques are not readily adaptable to operate in the high-power, high-noise environment of a power line.
Conventional solutions to the problem of transmitting data over a power line typically utilize complex and cumbersome equipment and techniques in order to perform reliably in the high-power, high-noise, phase distorted power line channels. For example, some systems monitor different frequency channels, select an appropriate channel, and then indicate the appropriate frequency to other communicating units. Others employ a plurality of signals which are not harmonically related. This requires complicated filtering and signal extraction.
Currently there is a need for a less complicated communication system that employs existing power lines to efficiently transmit data.
BRIEF SUMMARY OF THE INVENTION
The invention provides an apparatus and method for communicating information via a power line. The signal of the invention comprises a superset of a plurality of tone sets. The superset is characterized by the relationship:
s
i
(
t
)
=
∑
k
=
1
M
{
α
k
sin
(
2
π
f
ik
t
+
φ
k
)
+
β
k
cos
(
2
π
f
ik
t
+
θ
k
)
}
wherein t is time, i is a tone set index, k is a tone index, and wherein f
ik
represents the frequency of the kth tone of the ith user, and wherein M is the number of tones per tone set, &agr;
k
, &bgr;
k
, are signal amplitudes, and &phgr;
k
, &thgr;
k
are phase offsets. The signal is characterized by having a spectral shape exhibiting, within a harmonic interval, a plurality of main lobes of the signal. Each of the main lobes within the harmonic interval corresponds to a different tone set.
REFERENCES:
patent: 4700188 (1987-10-01), James
patent: 5032833 (1991-07-01), Laporte
patent: 5519692 (1996-05-01), Hershey et al.
patent: 5519725 (1996-05-01), Hershey et al.
patent: 5731765 (1998-03-01), Allison et al.
patent: 5844949 (1998-12-01), Hershey et al.
patent: 5903594 (1999-05-01), Saulnier et al.
“GHM Signaling for Automatic Meter Reading (AMR),” J.E. Hershey, GE Tech. Report 96CRD140, Oct. 1996.
“Digital Communications,” J.G. Proakis, McGraw-Hill, New York, 1995, pp. 686-692.
Hershey John Erik
Hoctor Ralph Thomas
Breedlove Jill M.
General Electric Company
Stoner Douglas E.
Tweel , Jr. John
Wu Daniel J.
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