Telecommunications – Interference signal transmission
Reexamination Certificate
1997-01-17
2001-08-28
Grant, Chris (Department: 2711)
Telecommunications
Interference signal transmission
C340S315000, C348S086000
Reexamination Certificate
active
06282405
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a method of signal injection, transmission, interconnection (termination), and detection, and to a power transmission network, ie. a mains electricity distribution and/or transmission network, and a filter therefor. In particular it relates to the use of mains electricity networks and/or lines for telecommunications transmission (e.g. voice, data, image and/or video).
In the UK, it is conventional to describe a power network for 33 kV and above as a “transmission network”, and one for less than 33 kV as a “distribution network”. In this specification the term “electricity distribution and/or power transmission network” is normally used, but general references to power networks and to transmission of signals are to be construed as applying to all such networks.
Traditionally telecommunications signals have been transmitted on independent networks e.g. telephone lines. More recently, in order to simplify and increase efficiency of telecommunications services to domestic or industrial premises, there have been investigations into using existing electricity transmission and distribution networks to carry telecommunications services.
A transmission network and a filter therefor is described in the applicant's co-pending International Patent Application, PCT/GB93/02163. This describes the use of telecommunications signals having a carrier frequency greater than around 1 MHz on a power transmission network. The teaching and disclosure of that patent application should be referred to in relation to the present invention, and is incorporated herein by reference.
At such carrier frequencies, it has been found that the cables of a power transmission and/or distribution network exhibit pseudo-coaxial characteristics and therefore attenuation of a signal transmitted along the cables is reduced. In this way, both speech and data signals can be transmitted at carrier frequencies of greater than approximately 1 MHz, allowing for a larger available spectrum and greater transmission capacity.
However, it has been found that the attenuation effects still limit the distance over which signals of a given carrier frequency and bandwidth can effectively be transmitted. On, for example, a 415 volt network the carrier frequency may preferably be between 1-10 MHZ, and on, e.g., an 11 kV network maybe between e.g. 1-20 MHZ or possibly 5-60 MHZ. Signals of this frequency can be transmitted over large distances (using repeater stations if necessary) and therefore a network used in this way is suitable for general telecommunications and telephony signals.
However broadband telecommunications signals, such as television communications, generally require a higher carrier frequency (or frequencies) and bandwidth. As indicated above, such signals are therefore usually transmitted on an independent broadband telecommunications network e.g. co-axial cable, optical fibre etc.
A carrier frequency of up to hundreds of MHZ may be used on a network as described in PCT/GB93/02163, although the distance over which a signal with a particularly high carrier frequency may be transmitted is limited by the dynamic range sensitivities and power levels deployed on the network—possibly to around 7-40 metres on a typical UK network.
SUMMARY OF THE INVENTION
The present invention aims to provide a transmission network which alleviates some or all of the above problems.
Accordingly, in a first aspect, the present invention provides a network linking a plurality of premises comprising a section of broadband telecommunications network and a plurality of electrical power cables each connected to a respective one of the premises for supplying mains electrical power thereto, each of said power cables also being connected to the section of broadband telecommunications network so that telecommunications signals are transmissible between the section of broadband telecommunications network and each of said power cables, wherein a telecommunications signal is transmissible to and/or from said plurality of premises by being transmitted along the section of broadband telecommunications network and also along the respective power cable of each of said premises.
In this way, the independent (preferably external) telecommunications network can be used to propagate the telecommunications signal over a long distance, with the (preferably external) power transmission/distribution network being used to propagate the telecommunications signal from the telecommunications network into e.g. the premises of a user and vice versa i.e. the communications may be bi-directional.
By “external”, it is meant that the signal transmission network i.e. power network and/or telecommunications network is external to any building or premises such as an office or house. Inside such buildings, transmission distances are typically short and therefore attenuation losses relatively unimportant.
The broadband telecommunications network may be a standard broadband distribution network e.g. a coaxial, twisted pair or fibre cable. Such telecommunications networks are currently available in most major countries. However, typically, the greatest cost and inconvenience associated with such telecommunications networks is not the initial installation of the main network but the connection of the main network to the premises of users. The present invention allows the existing power distribution networks (which commonly feed into most suitable premises) to be used to connect the existing telecommunications network to the desired premises. Thus the additional cost and inconvenience of installing further standard telecommunications network is avoided.
Typically, the distance between the existing telecommunications network infrastructure and the premises to which it is desired to be connected is short. Therefore broadband telecommunications signals may be transmitted over the power transmission/distribution network without attenuation losses having any significant effect.
Preferably, the present invention further includes satellite receiving means for receiving telecommunications signals from a satellite transmitter, wherein a telecommunications signal is transmissible from said satellite transmitter to said plurality of premises via said satellite receiving means, said section of broadband telecommunications network and said power cables. Alternatively or additionally, the satellite receiving means may be replaced or supplemented by other telecommunications signal receiving means, such as a TV aerial, telephone connection, data connection, etc.
Preferably, the network includes a plurality of interface units, each of said interface units connecting one of said power cables to said section of broadband telecommunications network, each of said interface units including high pass filter means for allowing high frequency telecommunications signals to pass between said section of broadband telecommunications network and said power cable, and for preventing low frequency mains electrical power signals from passing therebetween.
In a further aspect, the present invention provides a method of transmitting a telecommunications signal between a pair of buildings, including the steps of transmitting the signal from a first building along an external power cable for supplying mains power to the first building, followed by transmitting the signal along a section of broadband telecommunications network, followed by transmitting the signal along a second external power cable for supplying mains electrical power to the second building.
Preferably the telecommunications signal has a carrier frequency greater than approximately 1 MHz. The carrier frequency may in fact be less than 1 MHz ie. 800 kHz or even as low as 600 kHz, but as it is reduced so is the bandwidth. The term “carrier frequency” refers to the unmodulated frequency or frequencies of the carrier signal(s), and not to the frequency of the telecommunications signal or signals once modulated.
A plurality of telecommunications signals may be provided, each having different carrier fr
Grant Chris
Howrey Simon Arnold & White , LLP
Norweb PLC
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