WO2001099425A1

WO2001099425A1 - Communication system

Info

Publication number: WO2001099425A1
Application number: PCT/NL2001/000456
Authority: WO
Inventors: Menno De Roo; Petro Verheuvel
Original assignee: Roax B.V.
Priority date: 2000-06-19
Filing date: 2001-06-19
Publication date: 2001-12-27
Also published as: NL1015473C2; AU2001266425A1

Abstract

A communication system comprising a cable transmission network as well as at least one subscriber unit, which unit includes several high-frequency transmitting and receiving means for bidirectional transmission of data signals, using a modem for modulating said data signals on selected carrier wave frequencies.

Description

COMMUNICATION SYSTEM

The invention relates to a communication system comprising a cable transmission network as well as at least one subscriber unit, which unit includes several high-frequency transmitting and receiving means for bidirectional transmission of data signals, using a modem for modulating said data signals on selected carrier wave frequencies.

Such a communication system is generally known. In particular, a communication system is known which is suitable as a distribution system for analog or digital data signals, for example, such as radio/television signals, or other so-called utility signals, wherein such signals are transferred from a distribution unit comprising transmitting means to subscriber units comprising receiving means. The transfer of the signals takes place via the cable transmission network, which may for example comprise copper cables, coaxial cables or glass fibre cables. At present, the same communication system is used for bidirectional transmission of data signals, in order to enable activities and/or services, which may or may not be interactive, whereby subscribers transmit to each other and/or to the distribution network via the cable transmission network. The distribution unit will also comprise receiving means in such a case, and the subscriber unit which transmits in such a case will also include transmitting means. The present invention relates to such a communication system, which consequently comprises in particular several subscriber units, each including transmitting and receiving means, for bidirectional transmission of data signals between the subscriber units mutually and/or between the subscriber units on the one hand and the distribution unit on the other hand. The known communication system usually makes use of modems, which modulate/demodulate data signals on a carrier wave for transferring the data signals between the subscriber units mutually and/or between the distribution unit and the subscriber unit.

With the known communication system, various problems may occur, in particular the following:

- the known communication system uses the frequency range above 30 or 65 MHz for the various data signals being transmitted from the distribution unit, so that this bandwidth, which is normally used for radio/television signals, is additionally loaded;

the known communication system uses the bandpass range below 65 or 30 MHz, but certainly not below 15 MHz, for the return traffic, i.e. from subscriber unit to distribution unit, in order to prevent potential interference signals, so that the cable network is not being exploited in an optimum manner.

The object of the invention is to provide a communication system wherein the aforesaid drawbacks of the prior art are overcome, and in order to accomplish that objective, a communication system of the kind referred to in the introduction is according to the invention characterized in that:

said modem is arranged for bidirectional transmission of the data signals in the lower region of the bandpass range of the cable transmission network, in particular the region below 65 MHz, more in particular below 30 MHz, wherein said lower region of the bandpass range is preferably subdivided into sub-bandpass ranges for, respectively, data signals to be received and data signals to be transmitted;

the cable transmission network comprises at least one converter which is arranged for converting a. a data signal having a bandwidth Λ f from a first transmission channel, which is to be received by the modem, into n data signals each having the same bandwidth Λ f /n in the (sub-bandpass range for data signals to be received in the) lower region of the bandpass range of the cable transmission network; b. n data signals, each having the same bandwidth Δ f ' , which are to be transmitted by the modems, into one data signal having a bandwidth n Δ f ' in a second transmission channel .

As will be explained in more detail yet, this results in a strong increase of the capacity in the lower region of the bandpass range of the cable transmission network without affecting the upper region thereof.

In one preferred embodiment of a communication system according to the invention, the various transmitting and receiving means of the subscriber unit are connected to one central house modem, which is connected to the cable transmission network. The present communication system is based on the use of one central modem, which is directly connected to the main cable network, so that the use of various modems connected to the house cable network, at least of modems having their own transmitting means, is dispensed with. The data signals in said house cable network are confined to radio/television signals (i.e. only distributively carried high-frequency signals) , whose signal levels are sufficiently low so as not to cause immunity problems and emission problems.

In another preferred embodiment of a communication system according to the invention, said one central modem comprises means for blocking any interference signals that may be present. In this manner, the interference signals originating from the house cable network cannot find their way into the main cable network .

In another preferred embodiment of a communication system according to the invention, said one (single) central modem is arranged for bidirectional transmission of the data signals in the lower region of the bandpass range of the cable transmission network, in particular the region below 65 MHz, more in particular below 30 MHz.

In another preferred embodiment of a communication system according to the invention, said one modem comprises switching means, wherein, depending on a switching status of the switching means, bidirectional transmission of the data signals can take place in a preselected bandpass range of the cable transmission network corresponding to said switching status. In particular, said switching means can be switched between a first switching status corresponding to a bandpass range below 30 MHz, and a second switching status corresponding to a bandpass range below 65 MHz . Consequently, the present communication system has a high-frequency switching circuit, which makes it possible to selectively operate with the conventional limit value (30 MHz) in the bandpass range during an initial stage and with a new limit value (for example 65 MHz) in said range during a later stage. Said switching preferably takes place by remote control. In another preferred embodiment of a communication system according to the invention, said switching means are capable of exchanging sub-bandpass ranges for received data signals and transmitted data signals, respectively, within a preselected bandpass range. What is meant by this is that it is possible in the present communication system to exchange, that is, reverse, the upper region and the lower region of the bandpass range for received (downstream) or transmitted (upstream) data signals. After said reversal, said downstream is defined from 5 - 30 MHz, for example, and the upstream from 40 - 65 MHz.

In another preferred embodiment of a communication system according to the invention, said one central modem comprises an amplifier for amplifying data signals of a specific type that are transmitted to the subscriber, wherein the amplifier can be turned off so as to block the data signals of said specific type. In the present communication system, an amplifier is present which amplifies the high-frequency data signals before delivering said signals to the house cable network. Said amplifier can be deactivated at the command of, for example, a microprocessor which is present in the system. As a result, all radio/television signals for the house cable network will be blocked. This is preferred when the subscriber unit is to be turned off if the subscriber has not paid for a respective service. Important is that the bidirectional transmission of other data signals can be continued, if desired.

The invention will now be explained in more detail with reference to a figure illustrated in a drawing, wherein a preferred embodiment of a communication system according to the invention is schematically shown. The figure shows a communication system 1, comprising a glass fibre cable network 7 including transmission channels 7a, 7b, 7c and a cable transmission network 2 comprising coaxial cables. Data signals or information in the form of high-frequency central antenna radio and television signals are received in a station 3, which functions as a distribution unit, and transmitted to subscriber units 4 of network 2 via a dedicated transmission channel 7a. The signals, which are carried to the subscriber units over the network, via intermediate stations 5 and distributing stations 6, contain modulated high-frequency carrier waves. The modulation techniques that are used may comprise analog or digital modulation techniques, depending on what is required. Communication system 1 is a bidirectional communication system, which means that it is capable of functioning not only function as a distribution system but also as a medium for carrying data signals from subscriber units 4 to station 3 or to other subscriber units 4 located within the same district or outside said district. Consequently, station 3 is capable of transmitting and receiving both via the cable and via the air. As already said before, the present communication system 1 comprises the glass fibre network 7 with the electromagnetic light-transmitting transmission channels 7a, 7b, 7c, to which district centres 8 are connected. Said district centres 8 form coupling stations, as it were, for taking data signals received from station 3 from network 7, or conversely, for placing data signals from subscriber units 4 onto network 7. Present in the district centres 8 are the illustrated opto-electrical converters 11, which convert the light into the high-frequency electrical signals, and vice versa. In accordance with the invention, said high-frequency signals are transformed by a converter 9 in each of the district centres 8 to channels on the coaxial cable in the lower region of the band-pass range of network 2, in particular the region below 65 MHz, more in particular below 30 MHz. According to the invention, said lower region of the bandpass range is subdivided into two sub-bandpass ranges: one for data signals to be received by modems 10 of subscriber units 4, and the other for data signals to be transmitted by modems 10. The modems 10 that are present in the subscriber units or houses 4, will also be arranged for bidirectional transmission of the data signals in the aforesaid lower region of the bandpass range of network 2 in that case, wherein - as already said before - sub- bandpass ranges can be distinguished in said lower region 2 for data signals to be received by modems 10 on the one hand and for data signals to be transmitted by said modems on the other hand. Each converter 9 in the district centres 8 transforms the high-frequency electrical signals transmitted by the modems 10 in the houses to a common transmission channel 7c on a dedicated glass fibre cable in network 7. A major advantage of the communication system 1 according to the invention is the fact that the capacity in the lower region of the bandpass range is enormously increased, without affecting the upper region thereof, i.e. the region above 80 MHz, as will be explained in more detail by means of the example below.

Example

The converter 9 that is present in each district centre 8 comprises n gates (n = 1, 2, 3 ...), wherein each gate is connected via network 2 to n neighbourhoods within district centre 8, and wherein a neighbourhood comprises 100 - 200 modems 10, for example. In practical terms, converter 9 will comprise 8 gates, for example, and thus correspond to eight neighbourhoods (i.e. 800 - 1600 modems 10) . High-frequency electric data signals having a bandwidth Δ f, which are received from station 3 via a

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I. Communication system

2. Coaxial cable transmission network

3. Distribution unit (also receiving) 4. House with house network

5. Intermediate station

6. Distribution station

7. Glass fibre transmission network (several fibres)

8. District centre 9 . Converter

10. Central modem in house

II. Electrical/optical converter

Claims

1. A communication system comprising a cable transmission network as well as at least one subscriber unit, which unit includes several high- frequency transmitting and receiving means for bidirectional transmission of data signals, using a modem for modulating said data signals on selected carrier wave frequencies, characterized in that

said modem is arranged for bidirectional transmission of the data signals in the lower region of the bandpass range of the cable transmission network, in particular the region below 65 MHz, more in particular below 30 MHz, wherein said lower region of the bandpass range is preferably subdivided into sub- bandpass ranges for, respectively, data signals to be received and data signals to be transmitted;

the cable transmission network comprises at least one converter which is arranged for converting a. a data signal having a bandwidth Δ f from a first transmission channel, which is to be received by the modem, into n data signals each having the same bandwidth Δ f /n in the (sub-bandpass range for data signals to be received in the) lower region of the bandpass range of the cable transmission network; b. n data signals, each having the same bandwidth Δ f ' , which are to be transmitted by the modems, into one data signal having a bandwidth n Δ f ' in a second transmission channel.

2. A communication system according to claim 1, wherein the various transmitting and receiving means of the subscriber unit are connected to one central house modem, which is connected to the cable transmission network.

3. A communication system according to claim 1 or 2 , wherein said one central modem comprises means for blocking interference signals.

4. A communication system according to claim 1, 2 or 3, wherein said one modem comprises switching means, wherein, depending on a switching status of the switching^' means, bidirectional transmission of the data signals can take place in a preselected lower region of the bandpass range of the cable transmission network corresponding to said switching status.

5. A communication system according to claim 4, wherein said switching means can be switched between a first switching status corresponding to a bandpass range below 30 MHz, and a second switching status corresponding to a bandpass range below 65 MHz.

6. A communication system according to claim 4 or 5 , wherein said said switching means are capable of exchanging sub-bandpass ranges for received data signals and transmitted data signals, respectively, within a preselected bandpass range.

7. A communication system according to claim 5 or 6 , wherein said switching means can be activated by remote control.

8. A communication system according to any one of the preceding claims 1 - 7, wherein said one modem comprises an amplifier for amplifying TV, radio and/or broadcasting data signals, wherein said amplifier can be turned off so as to block said signals .