Communications: electrical – Continuously variable indicating – With meter reading
Reexamination Certificate
2001-09-21
2003-11-25
Edwards, Timothy (Department: 2635)
Communications: electrical
Continuously variable indicating
With meter reading
C340S870110, C370S328000
Reexamination Certificate
active
06653945
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a communications network for collecting data from remote data generating stations, and more particularly a radio based system for sending data from a plurality of network service modules, with each network service module attached to a meter, and communicating through remote cell nodes and through intermediate data terminals, to a central data terminal.
DESCRIPTION OF THE RELEVANT ART
Many attempts have been made in recent years to develop an automatic meter reading system for utility meters such as used for electricity, gas and water, which avoids meter reading personnel inspecting and physically noting the meter readings. There are, of course, many reasons for attempting to develop a system of this type.
Most of the prior art systems have achieved little success. The system, which has achieved some success or is most widely used has an automatic meter reading unit mounted on an existing meter at the usage site and includes a relatively small transmitter and receiver unit of very short range. The unit is polled on a regular basis by a traveling reading unit, which is carried around the various locations on a suitable vehicle. The traveling reading unit polls each automatic meter reading unit in turn to obtain stored data. This approach is of limited value in that it requires transporting the equipment around the various locations and, hence, only very infrequent, for example monthly, readings can be made. The approach avoids a meter reader person actually entering the premises to physically inspect the meter which is of itself of some value but only limited value.
Alternative proposals in which reading from a central location is carried out have been made but have achieved little success. One proposal involves an arrangement in which communication is carried out using the power transmission line of the electric utility. Communication is, therefore, carried out along the line and polls each remote reading unit in return. This device has encountered significant technical difficulties.
Another alternative attempted to use the pre-existing telephone lines for communication. The telephone line proposal has a significant disadvantage since it must involve a number of other parties, in particular the telephone company, for implementing the system. The utility companies are reluctant to use a system which cannot be entirely controlled and managed by them.
A yet further system using radio communication has been developed by Data Beam, which was a subsidiary of Connecticut Natural Gas. This arrangement was developed approximately in 1986 and has subsequently received little attention and it is believed that no installations are presently operative. The system includes a meter reading device mounted on the meter with a transmitting antenna which is separate from the meter reading device. The transmitting antenna is located on the building or other part of the installation site which enables the antenna to transmit over a relatively large distance. The system uses a number of receiving units with each arranged to receive data from a large number of transmitters, in the range of 10,000 to 30,000. The transmitters, in order to achieve maximum range, are positioned to some extent directionally or at least on a suitable position of the building to transmit to the intended receiving station. This arrangement leads to using a minimum number of receiving stations for optimum cost efficiency.
The separate transmitter antenna, however, generated significant installation problems due to wiring the antenna through the building to the transmitter and receiver. The anticipated high level of power used for transmitting involved very expensive battery systems or very expensive wiring. The proposal to reduce the excessive cost was to share the transmission unit with several utilities serving the building so that the cost of the transmitter could be spread, for example, between three utilities supplied to the building. Such installation requires separate utility companies to cooperate in the installation. While this might be highly desirable, such cooperation is difficult to achieve on a practical basis.
In order to avoid timing problems, the meter reading units were arranged to communicate on a random time basis. However, the very large number, up to 30,000, of meter reading units reporting to a single receiving station, leads to a very high number of possible collisions between the randomly transmitted signals. The system, therefore, as proposed, with daily or more often reporting signals could lose as many as 20% to 50% of the signals transmitted due to collisions or interference which leads to a very low efficiency data communication. The use of transmitters at the meter reading units which are of maximum power requires a larger interference protection radius between systems using the same allocated frequency.
An alternative radio transmission network is known as ALOHA. ALOHA has a number of broadcasting stations communicating with a single receiving station, with the broadcasting stations transmitting at random intervals. In the ALOHA system, collisions occur so that messages are lost. The solution to this problem is to monitor the retransmission of the information from the receiving station so that each broadcasting station is aware when its transmission has been lost. Each broadcasting station is then programmed to retransmit the lost information after a predetermined generally pseudorandom period of time. The ALOHA system requires retransmission of the information from the receiving station to take place substantially immediately and requires each broadcasting station to also have a receiving capability.
Cellular telephone networks are implemented on a wide scale. Cellular systems, however, use and allocate different frequencies to different remote stations. While this is acceptable in a high margin use for voice communications, the costs and complications cannot be accepted in the relatively lower margin use for remote station monitoring. The technology of cellular telephones leads to the perception in the art that devices of this type must use different frequency networks.
While theoretically automatic meter reading is highly desirable, it is, of course, highly price sensitive and hence it is most important for any system to be adopted for the price per unit of particularly the large number of meter reading units to be kept to a minimum. The high cost of high power transmission devices, receiving devices, and battery systems generally leads to a per unit cost which is unacceptably high.
OBJECTS OF THE INVENTION
A general object of the invention is a communications network for communicating data from a plurality of network service modules to a central data terminal.
Another object of the invention is a communications network which is suitable for an automatic meter reading system.
A further object of the invention is a communications network for collecting data from remote data generating stations that is simple and economic to install and maintain.
A still further object of the invention is a communications network for collecting data from network service modules that is spectrum efficient, and has inherent communication redundancy to enhance reliability and reduce operating costs.
An additional object of the invention is an open architecture communication network which accommodates new technology, and allows the network operator to serve an arbitrarily large contiguous or non-contiguous geographic area.
SUMMARY OF THE INVENTION
According to the present invention, as embodied and broadly described herein, a wide area communications network is provided for sending data from a plurality of network service modules to a central data terminal. The wide area communications network collects NSM data generated by a plurality of physical devices located within a geographical area. The physical devices may be, for example, a utility meter as used for electricity, gas or water. The wide area communications network comprises a plurality of network servi
Holowick Erwin
Jacob Nathan R.
Johnson Dennis F.
Murhpy Michael F.
Schellenberg James J.
Edwards Timothy
Itron, Inc.
Patterson Thuente Skaar & Christensen P.A.
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