GB2330286A

GB2330286A - Communication apparatus

Info

Publication number: GB2330286A
Application number: GB9814052A
Authority: GB
Inventors: David William Bartlett; Roger Joseph Sinclair
Original assignee: WORLDPIPE Ltd
Current assignee: WORLDPIPE Ltd
Priority date: 1997-06-27
Filing date: 1998-06-29
Publication date: 1999-04-14
Anticipated expiration: 2018-06-29
Also published as: GB2330286B; GB9814052D0

Abstract

A communication system for the transfer of broadband data includes a broadcast link in or above the microwave band. The system includes a base station (not shown) and one or more user stations. The user stations utilise existing cabling 25 e.g for the supply of received tv signals, for the routing of data into or out of the user station. A unit 101 transmits or receives the broadcast data by antenna 21, down converts it to an RF frequency different from that of existing signal which uses the cable 25 and couples it at 190 into or out of the cable 25. A separator 200 separates the tv and data signals and supplies them to a tv receiver or a computer 360 for Internet use. Data transmission may be unidirectional as in the case of a security monitoring system. The downconverted data signal may be electromagnetically coupled into the existing cabling or re-radiated into the tv aerial.

Description

COMMUNICATION APPARATUS The present invention relates to a method and apparatus for communication of data. The invention has particular although not exclusive relevance to line of sight communications and the installation of transceiver equipment at user premises.

There has been an increasing demand for providing a broadband communications link into homes and businesses, for the provision of services such as video on demand, high speed internet, video telephony, on-line multiplayer gaming etc. At present, the communications link into homes and businesses is predominantly twisted pair telephone lines which may be used to carry analogue telephone and modem signals or ISDN. The bandwidth provided by such technology is, however, limited and may be described as narrowband.

It has been proposed to provide a broadband communication link for providing such services, by providing a microwave link between a local base station and the homes and businesses. The microwave frequency band between 5 and 60 GHz is presently little used although the franchising of bandwidth in this range is already common.

However at such frequencies, it is necessary that the transmitter and receiver unit remain within line of sight of each other as the electromagnetic radiation has very low penetration, that is to say it cannot pass through objects such as buildings, trees or the like.

Consequently, current proposals such as the microwave multipoint distribution service (MMDS) require the user's microwave transceiver to be mounted as high as possible, i.e. on the roof of the user's building.

The problem that the present invention addresses is that of how to install the microwave link in the most economic manner, including routing the signals to the user's desired location, without significantly compromising system performance.

One of the most expensive parts of the installation of such a communications link is the cost involved in installing a new cable run from the microwave antenna to the user's equipment which may be several floors below the roof. The present invention avoids the need for the installation of such an expensive cable run by coupling into an existing cable run such as the coaxial cable commonly used to connect a user's television to the roof mounted aerial.

According to one aspect, the present invention provides a signal routing system for user station for use in a communications system of the type which broadcasts data in or above the microwave band from a base station to one or more user stations, the user station comprising: an existing cable for routing an RF signal from an aerial on the user station to a terminal internal to the user station; and a first unit comprising: (i) means for receiving the broadcast data; (ii) means for down-converting the received data to an RF frequency carrier different from that of said RF signal; and (iii) means for coupling the down-converted data into the existing cable.

The present invention also provides a communications system as set out in claim 1, a converter unit as set out in claim 33 and a data distribution method as set out in claim 44.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 schematically illustrates a communications system having a base station which transmits and receives data from a plurality user stations; Figure 2 is a block diagram illustrating the components of the base station shown in Figure 1; Figure 3 is a block diagram illustrating the components of a transceiver system forming part of one of the user stations shown in Figure 1; Figure 4 is a block diagram showing in more detail the components of a converter unit which forms part of the transceiver unit shown in Figure 3; Figure 5 is a diagram showing the electromagnetic spectrum of the signals passed along an existing aerial cable forming part of the transceiver system shown in Figure 3; Figure 6 is a block diagram showing in more detail the components of a separator unit forming part of the transceiver system shown in Figure 3; Figure 7 is a block diagram of a base station transmitter for use in a communication system in which a base station transmits data to a plurality of user stations; Figure 8 is a block diagram illustrating the components of a receiver forming part of a user station which can receive the data transmitted by the base station transmitter shown in Figure 7; and Figure 9 is a diagrammatic representation of one way in which a transceiver system, such as the one shown in Figure 3, or a receiver system, such as the one shown in Figure 8, can couple with an existing television aerial system.

First Embodiment Figure 1 schematically illustrates a microwave communication system between a base station 10 and three user stations 20-1, 20-2 and 20-3. In this embodiment, the microwave communications link is provided to give the users in the respective user stations 20 access to the internet via the base station 10. In this embodiment, the communication link between the base station 10 and each of the user stations 20 is bi-directional with the data being carried from the base station 10 to the user stations 20 modulated onto a microwave carrier signal having a first frequency and with the data transmitted back from the user stations 20 to the base station 10 modulated on a second microwave carrier signal having a different frequency. In this embodiment, the carrier signals have a frequency between 5 and 60 GigaHertz. In the remaining description, the data transmitted from the base station 10 is referred to as forward data and the data transmitted from the user stations 20 is referred to as return data.

As illustrated in Figure 1, the forward and return data passes between a base station antenna 11 and user antenna 21-1, 21-2, 21-3. In order to attempt to ensure a clear line of sight path between the base station antenna 11 and each user 21, both the base station antenna 11 and the user antenna 21 are mounted on the roofs of the respective premises. In this embodiment, the user stations 20-1, 20-1, 20-3 are located within a range of 5 kilometres and the user stations are located in proximity to each other so that the microwave link between the user stations 20 and the base station 10 does not have to be high powered and can be directional in nature. If 360" coverage is required then the base station 10 will require a plurality of transceivers each pointing in a different direction.

As illustrated in Figure 1, each of the user stations 20 have an existing terrestrial television aerial 22-1, 22-2 and 22-3 which are mounted on the roof in order to provide good television reception. As will be described in more detail below, the forward and return data is transported between the roof of the respective user station 20 and the user's equipment by coupling the data into the existing cabling which connects from the roof mounted television aerial to a socket located in the respective user house.

Figure 2 shows in more detail the components of the base station 10. As shown, the base station 10 is connected to an internet router 52 which is connected to other servers on the internet (not shown) via a bidirectional communications link 50 which, in this embodiment, is a fibre optic link. In response to a request for information from one of the user stations 20, the internet router 52 retrieves the required information locally or via other internet servers via the link 50 and passes this information to an encoder 54 where the data is encoded so as to reduce errors caused by interference in the communications channel and to introduce redundancy for error correction purposes. The encoded data is then provided to modulator 56 where the encoded data is modulated using quadrature phase shift keying (QPSK) technique and then up-converted to a microwave frequency.

The modulated data is then passed to amplifier 54 where it is amplified to a power suitable for transmission to the user stations 20. As will be appreciated by a person skilled in the art, the necessary amplifier gain is a function of the required broadcast distance and the broadcast beam angle. The amplified output signal is then fed to the circulator 60 which routes the signal to be broadcast to the bidirectional antenna 11.

As mentioned above, the internet router 52 provides data in response to requests received from the user stations 20. These requests are transmitted from the user stations 20 and are received by the bi-directional antenna 11. As will be explained in more detail below, each of the user stations 20 transmits the requests on a common frequency channel but on a time division multiplexed basis. The signals received by antenna 11 are passed to the circulator 60 which routes them to amplifier 59. The amplified received signals are then down-converted and demodulated by the demodulator 57 and then decoded by the decoder 55. The decoded requests are then passed to the internet router 52 which separates the requests from the three user stations 20 and takes the necessary steps to retrieve the requested information.

In this embodiment, the bandwidth of the microwave link is 30 MHz which is shared between the forward and return data. In this embodiment, since the user stations 20 do not need a large bandwidth to transmit their requests, a bandwidth of 25 MHz is allocated to the forward data and a bandwidth 5 NHz is allocated to the return data.

By using a standard QPSK modulation technique, this allows 25Mbits per second of data to be transmitted from the base station 10 to the user stations 20 in the available bandwidth. In order that each of the user stations can receive data at the same time, the data for each user station 20 is multiplexed in time. Therefore, in this embodiment, with three user stations, each user can receive up to 25M bits per second from the base station 10 as compared with 64K bits per second available via a conventional ISDN line.

The system arrangement at user station 20 will now be described with reference to Figures 3 to 5.

As mentioned above, each user station 20 comprises a microwave antenna 21 for receiving data from and for transmitting data to the base station 10 and a TV aerial 22 for receiving teresterial broadcast television signals. As shown in Figure 3, the TV aerial 22 is connected to a TV aerial socket 27 via a coaxial cable 25. As illustrated in Figure 3, the microwave antenna 21 forms part of a user microwave transceiver unit 101 which is provided as a single unit so as to facilitate installation on the roof of the user station. As shown, the antenna 21 is connected to a converter unit 100 via a wave guide 24. The converter 100 down-converts the received microwave frequency signal to a radio frequency (RF) signal and outputs this to an electromagnetic coupling device 190 via cable 180. As schematically illustrated in Figure 3, the electromagnetic coupling device 190 surrounds a portion of the coaxial cable 25 which is located near the TV aerial 22 on the roof of the user station. The electromagnetic coupling device 190 operates to couple the radio frequency signal output by the converter unit 100 into the coaxial cable 25 using electromagnetic induction. The operating principals of the electromagnetic coupling device 190 are well known to those skilled in the art and a further description will be omitted. Therefore, as those skilled in the art will appreciate, in this embodiment, no physical alteration is required to the existing television installation. In this embodiment, power for the convertor unit 100 is provided by a solar cell 102 having a back-up battery which is rechargeable from surplus power generated by the solar cell, e.g. when the user station is not in use.

The converter unit 100 will now be described in more detail with reference to Figure 4. The signal input to the converter unit 100 is input to a circulator 170 which separates the forward and return data signals and provides the forward data signal to a primary downconverter 110 for down-conversion to an intermediate frequency lying between 3 GHz and 10 GHz. The output of the primary down-converter 110 is then passed to a secondary down-converter 120 which down converts the intermediate frequency signal to a frequency just above that of the conventional television and radio frequency spectrum so that they do not overlap. The signal output from the secondary down-converter 120 is then passed to an amplifier 130 where it is amplified to a suitable power so as to allow coupling into the existing TV cable run 25 via the coupling device 190. In this embodiment, an externally adjustable gain control unit (not shown) is provided for allowing adjustment of the gain of the amplifier 130. This allows the installer to be able to ensure that the gain is such that there is adequate signal to noise ratio at the other end of the cable run 25, but not so much as to waste power consumption from the solar cell/battery unit 102. The amplified forward data signal is then routed to the cable 180 by the circulator 135.

In addition to coupling the forward data signal output by the converter unit 100, the electromagnetic coupling device 190 also acts as a sensing pick-up for the return data signal which is passed, via cable link 180, back to the converter unit 100. This return data signal is routed by the circulator 175 to an amplifier 160 for appropriate pre-amplification before up conversion to the microwave frequency band for subsequent transmission.

Up-conversion is achieved using primary and secondary upconverters 150 and 140 respectively. The output from the secondary up-converter 140 is then amplified by a power amplifier (not shown) and passed to circulator 170 which routes the return data signal, via waveguide 24, to the microwave antenna 21 for transmission back to the base station antenna 11.

In the convertor unit 100 of this embodiment, it will be noted that primary and secondary up and down-converters have been utilised. This is because suitable "off the shelf" units are currently readily available. However, it will be appreciated that a single up and a single down-converter could be used instead.

Returning to Figure 3, the forward data signal coupled into TV cable 25 passes along the cable 25 to the TV aerial socket 27. The electromagnetic spectrum of the signals which pass along this cable is shown in Figure 5. As shown, the portion of spectrum between 50 Megahertz and 1 Gigahertz (reference numeral 400) is conventionally used for television and radio signals, three such signals being shown. This allows the portion above 1 Gigahertz (reference numeral 410) to be used for transmission of the internet data. The transfer characteristics of coaxial cable 25 commonly provided for television signal routing is sufficient for the propagation of a 30 MHz bandwidth signal (which is what required in this embodiment to accommodate the forward and return data) even at a band commencing at 1 Gigahertz, over the cable run conventionally found in most dwellings. As shown in Figure 5, the forward and return data are separated in the frequency domain, with the forward data being located between 1 GHZ and 2 GHZ and the return data being located between 2 GHZ and 3 GHZ of the spectrum. As shown and as explained earlier, the return data occupies a smaller bandwidth since, in this embodiment, less data usually travels from the user stations 20 to the base station 10.

Returning again to Figure 3, the portion of the system after the TV aerial socket 27 will now be described. The television aerial socket 27 is connected to a separator unit 200 using a coaxial cable 201. The separator unit 200 splits the signal into the conventional television signal and the forward internet data signal. The conventional television signal is passed via coaxial cable 340 to a television receiver 350 and the internet data signal is passed to a decoder unit 300, to be described below.

The operation of the separator unit 200 will now be described in more detail with reference to Figure 6. As shown, the received forward data signal from cable 201 is passed to a circulator 210 which routes the incoming forward data signal to a splitter 220. In this embodiment, the splitter 220 comprises a divider having a single input and two outputs, the outputs having identical signals to the input. The signal for transmission to the television receiver 350 is passed to a low pass filter 230 which removes the higher frequency forward data signal component (reference numeral 410 in Figure 5) and output to cable 340. The other output signal from the splitter is passed through high pass filter 240 which removes the low frequency television components (reference numeral 400 in Figure 5), to leave just the high frequency forward data signal which is output to the decoder 300.

As shown in Figure 6, the separator unit 200 also has an input 207 for a RF modulated return data signal which is routed via the circulator 210 to the cable 201. In this embodiment, an amplifier (not shown) is provided in the separator unit 200 for amplifying the return data signal before being fed along the TV cable 25 via socket 27.

However, due to the provision of the circulator 26, the return amplified data signal will not be passed to the television receiver 350 via cable 340, thereby preventing any possible damage to the television receiver.

The separator unit 200 therefore provides a forward data signal to and receives a return data signal from decoder box 300 shown in Figure 3. In this embodiment, the separator unit 200 and the decoder box 300 are provided as separate units, although they can be provided in a single package. As shown in Figure 3, the decoded box 300 comprises a demodulator 302 for demodulating the radio frequency forward data signal and a decoder 304 for decoding the forward data to retrieve the information provided by the internet server 52 shown in Figure 2.

This information is then passed to the user's personal computer 360 where the information is displayed on the display 370. The decoder box 300 also contains an encoder 308 for encoding the requests input via the PC and the keyboard 380 and a modulator 306 for modulating the requests to provide the radio frequency return data signal.

It will be understood from the above description, that a bi-directional internet communication link has been provided which does not require the installation of an additional cable from the roof based antenna to the user's computer. As those skilled in the art will appreciate, in the case where the microwave link is provided for a plurality of the users in the same building (for example, for a block of flats or for a business user) additional cabling from the roof mounted antenna to each user can be avoided since the more extensive existence cabling can be used.

In the first embodiment the forward and return data signals are separated in the frequency domain and the signals to and from the different user stations are separated in the time domain. However this need not be the case. Either type of multiplexing could be used for either task or, alternatively, a more sophisticated multiplexing technique could be employed. Equally the broadcast data could include a destination address making multiplexing of the forward signal unnecessary.

Additionally, instead of the return data being passed back to the base station 10 via the microwave link, a separate link via, for example, the telephone could be used.

It will also be understood that the data modulation used in this embodiment (QPSK) and the bandwidth of the forward and return signals are by way of example and other types of modulation are equally applicable.

Second Embodiment A second embodiment of the invention will now be described. In this embodiment, the data transmitted over the microwave link is digital video data. Therefore, in this embodiment, the microwave link is unidirectional with the data only being transmitted from the base station to the user station or stations. The arrangement of base station and user stations is similar, therefore, to that shown in Figure 1, save that the link is unidirectional.

The base station transmitter of this embodiment will now be described with reference to Figure 7. As shown, the video data to be transmitted is stored in a video data store 70 which, in this embodiment, comprises a stack of optical discs. Alternatively, the video data could be provided from a communications channel (not shown) such as a fibre optic or satellite link, with the base station 10 effecting local distribution. The video data output by the video data store is encoded for transmission using encoder 72. The encoded data is then modulated and upconverted to a microwave signal by modulator 74 in the same manner as in the first embodiment, except that there is more bandwidth available since there is no return data. The modulated signal is then amplified to a suitable power for transmission by the amplifier 76 and passed to a transmitting antenna 78 which is situated so as to maintain line of sight communication with the domestic user stations in a similar manner to the first embodiment.

The system arrangement at the user station will now be described with reference to Figure 8. Where there is no modification from the system of the first embodiment, like reference numerals has been employed and a detailed description of the like components has been omitted. As shown, in this embodiment, the converter unit 100' only requires the receive electronics, namely, in sequence, primary down-converter 110', secondary down-converter 120' and amplifier 130'. No circulators are required in converter unit 100' because the data is purely unidirectional in nature. The data is output along cable 180 and coupled into TV cable 25 via induction loop 190 in the same manner as the first embodiment.

At the other end of the TV cable 25, the separator unit 200' is a simplified version of that used in the first embodiment. Again, a circulator is unnecessary and the data is passed directly to splitter 220 and thereafter to low pass filter 230 and high pass filter 240 for output to the existing television equipment and decoder box 300' respectively. Decoder box 300' contains the necessary modules for digital video decoding, mainly demodulator 302 and decoder 304. In this case, the digital data is also converted into an analogue signal using a digital to analogue converter (not shown) so that it can be provided to the analogue television receiver 350. The signal to the television receiver is provided by cable 345, which is, in this embodiment, a scart lead.

If, however, a digital television display unit is available, the digital to analogue converter may be dispensed with and the output from the decoder passed directly to the digital television.

In this embodiment the unidirectional data channel is from the base station to the user station. However this need not be the case and a unidirectional data channel from the user station to the base station may be appropriate in certain circumstances. For example, where the user stations form part of a monitoring system, such as a security system, where data is generated at the user stations and transmitted back to a central monitoring base station.

In the above embodiments, the cable 25 has been referred to as a cable for a television aerial. This need not be the case and the existing cabling could be provided for, for example, radio reception.

In the above embodiments, the down converted microwave data was coupled into the existing coaxial run 25 using an electromagnetic coupling device 190. An alternative mode of coupling the signal to the existing cabling will now be described with reference to Figure 9. In this embodiment, microwave data is received and/or transmitted by antenna 21 as before. In the case of received data, it is passed to the converter for down conversion to the appropriate RF frequency. However, instead of subsequently being fed to an induction loop, the output from the converter is fed to a short range antenna 500 which is adapted to be highly directional and of low power so as to have a very short range to avoid any interference and to minimise its external power consumption. The broadcast signal is then received by the terrestrial TV (or radio) aerial 22. The transmitter need, therefore, only have a range of between 1 and 5 metres or less. The received signal is then passed along TV cable and separated from the TV and/or radio signals as before. In a similar manner, return data passes up the TV cable and to some degree will be broadcast by the TV aerial. This broadcast signal is then sensed by the antenna 500 and passed to the converter unit for processing as before.

The modification described above and the inductive coupling of the embodiments are preferred embodiments of the invention because they require no physical alteration to the existing cabling structure. This results in ease of installation and removes any possibility of degradation of the existing system. However, in a further modification, the input/output from converter 100 may be directly coupled via cable 180 to the existing television cable run 25 by soldering, screw terminations or the like. This does, however, require modification of television cable run 25 which will require to be weather tight in order to prevent corrosion or other degradation. However, with such an embodiment, it is possible to provide power to the converter unit 100 by feeding a DC or low frequency AC voltage up the television cable 25 thus dispensing with the necessity of a solar cell and back up battery and providing a reliable power source without the necessity of further cable runs.

Alternatively another form of local power source could be used such as long life batteries or wind power. A further possibility is to run a new and separate power cable directly to the converter unit 100. Although this requires additional cabling, it is generally likely to be of short length as, in many cases, mains power is available in or near to the roof space. Furthermore, only a single cable capable of carrying low power DC need be installed, as the return could be provided via the aerial earth.

In the embodiment described herein data has been broadcast in the microwave band, however, other bands such as that of light (visible or otherwise) could be utilised.

Also in the described embodiments, the TV or Radio infrastructure was pre-existing. However it will be appreciated that the TV or radio aerial could be installed after the broadband transceiver system. In such a case the TV or Radio signals could share the cabling installed for the broadband transceiver system.

Other modifications and variations will be apparent to those skilled in the art.

Claims

CLAIMS: 1. A communications system comprising: a base station having means for broadcasting data modulated in or above the microwave frequency band; and a user station comprising: a cable for carrying an RF signal from an aerial on the user station to a terminal internal to the user station; a first unit comprising (i) means for receiving the broadcast data from the base station; (ii) means for down-converting the received data to an RF frequency carrier different from that of said RF signal; and (iii) means for coupling the down-converted data into the existing cable; and a second unit comprising means for connection to the terminal internal to the user station for receiving the down-converted data from the cable.
2. A system according to claim 1 wherein said data broadcast is bidirectional in forward and return directions, data broadcast from the base station to the user station being in the forward direction, wherein: the second unit further comprises (i) means for inputting return data; (ii) means for modulating the input return data at an RF frequency different from that of the RF signal; and (iii) means for passing the RF modulated return data to the terminal internal to the user station for return to the first unit; wherein said first unit further comprises means for up-converting the return RF modulated return data to a frequency in or above the microwave band and means for broadcasting said return data modulated in or above the microwave band to the base station; and wherein the base station further comprises means for receiving the return broadcast data.
3. A system according to claim 2 wherein said means for modulating the return data at an RF frequency is adapted so as to modulate the return data at a frequency different from that of the RF modulated forward data.
4. A system according to claim 2 or 3 wherein said means for up-converting the return data to a frequency in or above the microwave band, is adapted so as to up-convert the return data to a frequency different to the modulation frequency of the forward broadcast data.
5. A communications system according to any preceding claim wherein said second unit further comprises means for splitting the down-converted data from the RF signal.
6. A communications system comprising a base station and at least one user station wherein: the user station comprises a cable carrying a RF signal from an aerial on the user station to a terminal internal to the user station and first and second units; wherein the second unit of the user station comprises a data input and means for modulating the input data at an RF frequency different from that of the RF signal; and wherein the first unit comprises means for coupling the RF modulated data out of the cable; means for up-converting the RF modulated data to a frequency in or above the microwave band and means for broadcasting the modulated data in or above the microwave band to the base station; and wherein the base station comprises means for receiving the broadcast data.
7. A system according to any preceding claim wherein the first unit of the user station further comprises a local power supply.
8. A system according to claim 7 wherein said local power supply is a solar cell having a battery back up.
9. A system according to any preceding claim wherein the means for coupling the data into or out of or both into and out of the cable comprises an inductive loop for surrounding the cable and arranged so as to induce a signal therein or pick up a signal therefrom or both.
10. A system according to any of claims 1 to 8, wherein the means for coupling the data into or out of or both into or out of the cable comprises means for the short range broadcast transmission of the data between the first unit of the user station and the aerial.
11. A system according to any of claims 1 to 8, wherein the means for coupling the data into or out of or both into and out of the cable comprises a direct physical connection to the cable.
12. A system according to any preceding claim wherein the modulation frequency in or above the microwave band lies between 5 and 60 GHz.
13. A system according to any preceding claim wherein the modulation frequency in or above the microwave band lies between 18 and 40 GHz.
14. A system according to any preceding claim wherein the RF frequency carrier of the data lies above the existing RF signal.
15. A system according to claim 14 wherein the RF carrier displaced above that of the existing RF signal lies between 1 and 3 GHz.
16. A system according to any preceding claim comprising plural user stations.
17. A system according to claim 16 wherein the broadcast data between the base station and the plural user stations is time division multiplexed.
18. A communications system substantially as described herein with reference to or as shown in the accompanying drawings.
19. A user station for use in a communications system of the type which broadcasts data in or above the microwave band from a base station to one or more user stations, the user station comprising: a cable for carrying an RF signal from an aerial on the user station to a terminal internal to the user station; a first unit comprising: (i) means for receiving the broadcast data; (ii) means for down-converting the received data to an RF frequency carrier different from that of said RF signal; and (iii) means for coupling the down-converted data into the existing cable; and a second unit comprising means for connection to the terminal internal to the user station for receiving the down-converted data from the cable.
20. A user station according to claim 19 wherein said data broadcast is bidirectional in forward and return directions, data broadcast from the base station to the user station being in the forward direction, wherein tte second unit further comprises: (i) means for inputting return data; (ii) means for modulating the input return data at an RF frequency different from that of the RF signal; and (iii) means for passing the RF modulated return data to the terminal internal to the user station; and wherein said first unit further comprises: means for up-converting the RF modulated return data to a frequency in or above the microwave band; and means for broadcasting said return data modulated in or above the microwave band to the base station.
21. A user station according to claim 20 wherein said means for modulating the return data at an RF frequency is adapted so as to modulate the return data at a frequency different from that of the RF modulated forward data.
22. A user station according to claim 20 or 21 wherein said means for up-converting the return data to a frequency in or above the microwave band is adapted so as to up-convert the return data to a frequency different to the modulation frequency of the forward broadcast data.
23. A user station for use in a communications system of the type where broadcasts data from one or more user stations to a base station, the user station comprising: a cable carrying a RF signal from an aerial on the user station to a terminal internal to the user station; a second unit comprising a data input and means for modulating the input data at an RF frequency different from that of the RF signal; and a first unit comprising: (i) means for coupling the RF modulated data out of the cable; (ii) means for up-converting the RF modulated data to a frequency in or above the microwave band; and (iii) means for broadcasting the modulated data in or above the microwave band to the base station.
24. A user station according to any of claims 19 to 23 wherein the first unit further comprises a local power supply.
25. A user station according to claim 24 wherein said local power supply is a solar cell having a battery back up.
26. A user station according to any of claims 19 to 25 wherein the means for coupling the data into or out of or both into and out of the cable comprises an inductive loop for surrounding the cable and arranged so as to induce a signal therein or pick up a signal therefrom or both.
27. A user station according to any of claims 19 to 25, wherein the means for coupling the data into or out of or both into or out of the cable comprises means for the short range broadcast transmission of the data between the first unit and the aerial.
28. A user station according to any of claims 19 to 25 wherein the means for coupling the data into or out of or both into and out of the cable comprises a direct physical connection to the cable.
29. A user station according to any of claims 19 to 28 wherein the modulation frequency in or above the microwave band lies between 5 and 60 GHz.
30. A user station according to any of claims 19 to 29 wherein the RF frequency carrier of the data lies above the existing RF signal.
31. A user station according to claim 30 wherein the RF carrier displaced above that of the existing RF signal lies between 1 and 3 GHz.
32. A user station substantially as described herein with reference to or as shown in the accompanying figures 1, 3 to 6, 8 or 9.
33. A converter unit for use in a user station of a communication system of the type having a base station communicating with a user station via a broadcast link in or above the microwave band, the user station having a cable for carrying an RF signal from an aerial on the user station to a terminal internal to the user station; the converter unit comprising: (i) means for receiving the broadcast data from the base station; (ii) means for down-converting the received data to an RF frequency carrier different from that of said RF signal; and (iii) means for coupling the down-converted data into the existing cable.
34. A converter unit according to claim 33 wherein said data broadcast is bidirectional in forward and return directions, data broadcast from the base station to the user station being in the forward direction, wherein the unit further comprises: means for up-converting RF modulated return data passed to the unit via the existing cable to a frequency in or above the microwave band; and means for broadcasting said return data modulated in or above the microwave band.
35. A converter unit for a user station of a communications system of the type having a user station broadcasting to a base station in or above the microwave band, the user station having a cable carrying a RF signal from an aerial on the user station to a terminal internal to the user station, the converter unit comprising: means for coupling the RF modulated data out of the cable; means for up-converting the RF modulated data to a frequency in or above the microwave band and means for broadcasting the modulated data in or above the microwave band.
36. A unit according to any of claims 33 to 35 further comprising a local power supply.
37. A unit according to claim 36 wherein said local power supply is a solar cell having a battery back up.
38. A unit according to any of claims 33 to 37 wherein the means for coupling the data into or out of or both into and out of the cable comprises an inductive loop for surrounding the cable and arranged so as to induce a signal therein or pick up a signal therefrom or both.
39. A unit according to claims 33 to 37, wherein the means for coupling the data into or out of and both into or out of the cable comprises means for the short range broadcast transmission of the data to or from or both to and from the aerial.
40. A unit according to any of claims 33 to 37 wherein the means for coupling the data into or out of or both into and out of the cable comprises a direct physical connection to the cable.
41. A unit according to any of claims 33 to 40 wherein the modulation frequency in or above the microwave band lies between 5 and 60 GHz.
42. A unit according to any of claims 33 to 41 wherein the RF frequency carrier of the data lies above the existing RF signal.
43. A unit according to claim 42 wherein the RF carrier displaced above that of the existing RF signal lies between 1 and 3 GHz.
44. A method of distributing about a user station data received as modulated data in or above the microwave band, using a cable providing a communication channel for an existing RF signal the method comprising the steps of: prior to passing the data along the existing RF transmission channel: receiving data broadcast in or above the microwave band; down-converting the data to an RF carrier displaced above that of the existing RF signal; coupling the data at the RF carrier into the cable; and after passing the data along the existing RF transmission channel: separating the data from that of the existing RF channel; and providing the data as a data output and a signal output being from the existing RF channel.
45. A method according to claim 44 wherein said data transmission is bidirectional in forward and return directions and wherein the method further comprises the steps of: prior to passing return data along the existing RF transmission channel: inputting return data; modulating said return data at an RF frequency above that of the RF channel; and after return data has been passed from the existing RF transmission channel: up-converting the return data to the microwave band; and outputting said microwave modulated return data.
46. A method according to claim 45 wherein said return data is modulated at an RF frequency different to that of the RF modulated forward data.
47. A method according to claim 45 or 46 wherein said up-conversion of return data to the microwave band, up-converts the return data to a frequency different to the modulation frequency of the forward microwave data.
48. A method according to any of claims 44 to 47 wherein said cable connects a roof-mounted terrestrial television or radio aerial at said first end of the cable to an internal output socket at the said an or other end of the cable.
49. A method according to any of claims 44 to 48 wherein the data at the RF carrier frequency is induced into the RF transmission channel.
50. A method according to claim 48 wherein the data at the RF carrier frequency is coupled into the RF transmission channel by the step of short range transmission of the data towards the roof-mounted terrestrial television or radio aerial.
51. A method according to any of claims 44 to 50 wherein the microwave modulation frequency lies between 5 and 60 GHz.
52. A method according to any of claims 44 to 51 wherein the RF carrier displaced above that of the existing RF channel lies between 1 and 3 GHz.
53. A method of transmitting data modulated at or above a microwave frequency along a cable providing an existing RF transmission channel substantially as described herein with reference to or as shown in the accompanying drawings.
54. An internet distribution system including the communications system of any of claims 1 to 5 or any of claims 7 to 17 when dependent upon claims 1 to 5.
55. A video distribution system including the communications system of any of claims 1 to 5 or any of claims 7 to 17 when dependent upon claims 1 to 5.
56. A security system including the communications system of any of claims 1 to 17.