SE504570C2 - Combined hybrid fibre coaxial and twisted pair technique - Google Patents

Abstract

A hybrid fibre coax technique is used for transmission of information from the communication installation and the subscriber equipment (down link), and a hybrid fibre twisted pair technique is employed for transmission of information from the subscriber equipment to the communication installation (up link). The hybrid fibre twisted pair technique uses an asymmetric digital subscriber line method for the communication traffic on the up link, and an asymmetric digital subscriber line module functions as multiplexer serving both a computer and an adjustment terminal for the transmission on the up link. The module multiplexes communication traffic before transmission to an integrated service digital network and the ordinary telephone service. The subscriber equipment is installed in a dwelling place or other small location and the communication installation is preferably a video on demand server. The hybrid fibre coax technique uses a cable TV network on the down link and the hybrid fibre twisted pair technique uses an unshielded twisted pair arrangement on the up link.

Description

504 570 10 15 20 25 30 35 40 2 cell transmission according to the ATM standard up to a transmission point in the vicinity of the subscriber. The network does not use the ordinary copper network.

Document US, A, 5,029,333 relates to a communication system that offers broadband communication to and from a subscriber. All communication takes place via an “active pedestal” which is connected to the network with the help of optical fibers (eg SONET). Communication from a regular telephone takes place by connecting the usual copper wires to the "pedestal" which can also offer broadband communication to the subscriber via coaxial cable. The communication over the copper cable is narrow-band here.

Document US, A, 5 303 229 describes a device intended for use in a fiber network. The device terminates the fiber communication and delivers signals in electrical form to the subscribers. Ordinary telephone signals are separated from the optical signal and delivered to the copper network. Furthermore, video signals are separated out and delivered via the coaxial cable.

Although the document WO, A1, 94/28 671 relates to power supply of telephone equipment, the physical structure described shows how a fiber network is connected to a unit which is in contact with both copper telephone lines and coaxial cable lines of a subscriber.

Document W0, A1,93 / 12,624 describes a fiber optic telephone network where signals are distributed to "pedestals" by optical means and delivered to the subscribers via ordinary copper wire.

The documents presented above describe at best asymmetric broadband two-way communication e.g. US, A, 5,029,333 and consequently does not solve the problem described above.

SUMMARY OF THE INVENTION The solution to the technical problem described above is based on the fact that most households today have access to cable TV, usually via coaxial cable, and that relatively broadband signals can be transmitted over short distances on the existing access network.

The problem is thus solved with a method and a device according to the present invention which utilizes the cable TV network for broadband communication to a subscriber equipment in a household or a small company, and the copper network for broadband communication from said subscriber equipment.

The invention involves combining the HFC and HFT techniques to achieve a symmetrical two-way communication.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 schematically shows the configuration of a cable TV network.

Figure 2 schematically shows the configuration of a cable TV network with fiber cable in the primary network.

Figure 3 schematically shows the configuration of a copper cable network using ADSL.

Figure 4 schematically shows the access network of a residential area (eg 500 households) using fiber cable, coaxial cable and two pairs of copper cable in accordance with the present invention.

DETAILED EMBODIMENT OF THE INVENTION In the following, the HFC technology will first be described in detail with reference to Figures 1 and 2.

Next, the current HFT technique is described in detail with reference to Figure 3.

Finally, the combination of the above techniques, in accordance with the present invention, will be described in detail with reference to Figure 4.

HFC technology The HFC technology (Hybrid Fiber Coax) refers to a hybrid system that uses both fiber cable and coaxial cable to transmit information; in the following, this is briefly stated with HFC.

The cable TV network is usually arranged with a tree and branch architecture based on a node called the head end. In the following, the term head end will be called "HE", which refers to the English word "Head End". At HE, programs are frequently converted from e.g. local TV stations or satellite receiver stations (RS) to appropriate channels and transmitted to households. HE is the distribution point for all signals transmitted on the cable 504 570 10 15 20 25 30 35 40 at the cable TV socket. A converter arranged e.g. 4 online. Several main coaxial cables start from HE to line dividers that transmit signals to several smaller mains. Line amplifiers are arranged along the main cables. This part of the network is called the primary network, and its radius coverage is about 5-10 km.

Branches from the primary network are defined as secondary networks, each of which serves several property areas, and extends up to 3 km. Signals transmitted over the secondary network are transmitted to the property network, which covers several hundred meters. Finally, the signals are transmitted via connection cables to special customer locations. The connection cable ends in a TV set then selects the desired signal from the signals available on the cable.

The cable TV network was used for the distribution of analogue TV channels. Multiple TV channels are multiplexed on the cable using FDM (Frequency Division Multiplexing). The spectrum is transposed to the 6 MHz bands in the USA (the 7 MHz band in Sweden) where each band corresponds to a single TV channel. The older cables provide a frequency from 5 MHz to 450 MHz. The upgraded cables provide frequencies up to 750 MHz.

Today, cable TV operators install fiber links in In HFC, fiber links are connected via HE with a number of local nodes, instead of coaxial cables in the primary network. each of which is located approximately one to three kilometers from households (see especially Figure 2). Each local node has a service area with approximately 500 households. The coaxial cable then transmits signals over shorter distances between the premises node and the property, ie the secondary network and the property network in Figure 2. The signals received in the property are essentially the same as the signals delivered from HE due to the fiber carrying the same multi-carrier spectrum as used by the cable TV industry.

The use of fiber optics (see especially Figure 2) reduces online service and entertainment costs and increases transmission quality. With fiber optics, signal transmission with a much larger bandwidth than is the case with the coaxial cable can also be achieved. In addition, the reliability of the signal transmission is improved.

Cable TV operators are increasingly trying to provide various integrated communication services. Currently, VDT (Video Dial Tone) transmissions are the main interest for them. The VDT service is asymmetric because it requires higher bandwidth communication in the downlink (to the customer) than in the uplink (from the customer). Examples of VDT are e.g. VOD (Video On-Demand, use video directories, distance learning etc). The high bandwidth of the most modern cable TV systems and the compatibility between analogue and digital modulation in different channels on the same cable make it possible to provide VDT.

Video signals on the downlink can consequently be transmitted in a digitally modulated 6 MHz band between 450-750 MHz. The modulation is based on techniques such as 64 QAM (Quadrature Amplitude Modulation). The 6 MHz channel can be modulated to transmit everything from 3 Mbit / s signals to 28 Mbit / s signals, and consequently more than one video signal can be transmitted in the same 6 MHz band. The system can therefore provide a sufficient number of downlink channels for "VOD services".

In HFC, the uplink transmission takes place in the frequency spectrum 5-30 MHz. HFC equipment that provides uplink communication in the frequency range 5-40 MHz is under development.

The uplink channel is shared by all subscribers in the service area and consequently a multiple access protocol is needed that regulates the channel use.

The main problems with using the cable TV network for two-way transmissions are as follows: 0 The tree topology and branch topology are intended for broadcasting of TV signals and are less suitable for two-way communication; Some systems do not have uplink transmission hardware due to the one-way amplifier chains arranged all the way from HE to households.

Amplifiers and filters must therefore be added to handle uplink channels. This modification is extensive, expensive and difficult to implement because the cable TV operators are not responsible for the property networks in Sweden. 504 570 10 15 20 25 30 35 40 6 To eliminate this problem, it has been proposed to use POTS (Plain Old Telephone Service) or ISDN (Integrated Service Digital Network) as a return route for VOD; Uplink transmissions may interfere with multiple noise sources as branch signals radiate together on their way to HE. Digital signal regeneration may be needed for successful uplink transmissions, leading to expensive uplink amplifiers; 0 The uplink frequency of cables in residential areas is divided and has limited capacity, ie four 6 MHz bands are shared by all customers in the service area. It can serve 480 channels at 56 Kbit / s, which is probably enough for VOD, but not enough for video conferencing and data services (eg LAN links) that need very high bandwidth in both directions.

HFT technology The HFT technology (Hybrid fiber / twisted pair) refers to a hybrid system where both fiber cable and two pairs of copper cable are used for the transmission of information; in the following, this is briefly stated with HFT.

Business operations in video distribution are increasingly becoming an interesting area for telecommunications operators. Video services and revenue generated therefrom will support and increase the development of the public telecommunications network to B-ISDN. The video services will also generate traffic on the already installed fiber optic transmission systems in the transport network. The existing copper-based access network in its current form is not possible to use for large-scale transmission of video information to households.

A recently developed technology, the Asymmetric Digital Subscriber Line (ADSL), makes it possible to transmit VOD over existing UTP-based access networks.

UTP means "Unshielded Twisted Pair" and refers to only two pairs of copper cable, hereinafter the abbreviation "UTP" is used.

ADSL I is based on a new coding technology and uses FDM to transmit information on a single copper pair; 2 10 15 20 25 30 35 40 504 570 7 Mbit / s in the downlink, 16 Kbit / s (full duplex) and full duplex POTS or ISDN (128 Kbit / s).

ADSL can be used on the copper pair that extends approximately 5.5 km without the need for any special modifications. ADSL only requires multiplexer equipment at the local exchange (LEX) and at the property network without any line repeaters to provide VOD.

ADSL I transmits only a single channel of MPEG-1 Picture Experts Group) encoded video information that has a limited video quality. To transmit video signals in the control channel (Exercise higher quality requires a higher capacity. ADSL III which is based on discrete multiton modulation has been developed by ANSI Working Group T1E1.4 to provide up to 6.3 Mbit / s downlink, 308 Kbit / s data channel (full duplex), 64 Kbit / s control channel, full duplex POTS and ISDN ADSL III operates over short distances up to 2.5 km ADSL III supports transmission of MPEG-2 video information.

To implement ADSL III in access networks, fiber cables can be used from the local exchange to local nodes in the residential area, and UTP can then transmit ADSL signals at shorter distances from these nodes to the homes. area of 2.5 km, approximately 500 households can be served by a single local node. Many public network operators install SDH-I fl About a Call in the primary part of the access network. The use of SDH rings together with fiber cables in the subfeeder cable enables the placement of local nodes within an area of 2.5 km from the homes. finnin HFC HFT-t knik n enli för li Both the HFC technology and the HFT technology described above are suitable for asymmetric services such as e.g. VOD. However, they are not suitable for services that require high bandwidth in both directions.

To support symmetrical broadband access, the HFC technology and the HFT technology can be combined in such a way that HFC is only used for downlink communication and HFT (ADSL), with high uplink bandwidth, is only used for uplink communication.

Like most HFC systems, the HFC / HFT system of the present invention is also based on the use of FDM 504 10 15 20 25 30 35 40 570 8 where the services are transmitted 64-QAM modulated in 6 MHz (7 MHz in Sweden) bands in the spectrum between 450 and 750 MHz. As mentioned earlier, the 6 MHz band can be modulated to transmit anything from 3 Mbit / s signals to more than 28 Mbit / s.

The HFC / HFT technology uses the cable TV network as it was originally designed, namely for one-way broadcasting communication.

Since there is no need for a return path (5-30 MHz), no modification of the coaxial cable distribution (tree and branch architecture) is needed, and the uplink frequency can instead be used for downlink traffic, resulting in even higher bandwidth for transmission services.

Furthermore, no multiple access protocol is needed, which provides a much simpler and cheaper system with less control procedures.

Finally, and perhaps most importantly, no modification of the physical cable TV networks is required.

By using ADSL, existing telecommunications services such as ISDN and POTS will be supported by HFC / HFT technology. Each customer can be guaranteed an uplink channel of up to 6.3 Mbit / s, which is quite sufficient for most services. As a temporary solution, e.g. ISDN is used for the return route for residential customers instead of ADSL.

Access configuration The main elements included in the HFC / HET architecture are illustrated in Figure 4. Each service area of approximately 500 households forms a network called a neighborhood network (NN). For each NN, a local node is defined to be located within an area from 1-2.5 km from households. These local nodes are called NNs (NNEs).

The housing network units (NNE) provide dynamic resource allocation of the housing network's resources, e.g. coaxial cable RF frequency spectrum. NNE digitally modulates the services in its assigned bands. NNE also supports network management, calls and traffic control. Incoming data via the ADSL modem is forwarded to the local exchange (LEX).

NNE is connected to SDH ADM (Add / -Drop Multiplexer) via a fiber link. The broadcast analogue video services (at 50-450 MHz) received from HE on a separate analogue fiber or main coaxial cable are assembled at NNE with the reserved spectrum for the digital services. HE can also be connected to the SDH ring.

A tuning terminal (ST) together with a TV and a remote control provide various video services. The ST box demodulates the incoming QAM signal to retrieve the digital service signal. These signals are transmitted on the RF band where ST is tuned for this band. The digital signal will then be decompressed; converted into an analog form and presented on the TV screen. On the uplink, the ST unit transmits data information and control information using ADSL.

Another customer equipment that can be installed is computer equipment. As in the case of ST, the computer equipment is equipped with a converter which receives QAM signals and demodulates them into digital signals, these being transmitted on the uplink by using ADSL.

As a result, the ADSL service module that serves both the computer and the ST becomes a multiplexer for uplink traffic.

Before transmission over the two-pair copper network, the traffic from the ADSL service module to POTS and ISDN is multiplexed. The full-duplex channels with 384 Kbit / s or 64 Kbit / s are shared between the ST and the computer. equip both ST and the computer equipment with their own digital In the future it is predicted that there will be QAM converters.

HFC / HFT technology uses ATM as the transmission mode for the following reasons: 0 ATM provides a powerful and flexible mechanism for multiplexing different types of services and different digital multiplex hierarchies. ATM also supports multiple QOS classes that include guaranteed bandwidth and resource allocation; The fixed cell format is economical in terms of required buffer space, implementation complexity and consequently costs; ATM technology is expected to be everywhere in networks that provide uninterrupted integration. It is a safe investment for the future (longer life) and in the near future the cost of ATM equipment is expected to decrease significantly; 504 10 15 20 25 30 570 10 0 The many ATM standards produced for administration, calls and traffic control can be adopted by the HFC / HFT technology; 0 ATM is independent of the transmission system used.

ATM has been standardized for transmission technologies that include ADSL. It is also expected to be standardized for cable TV networks.

The present invention thus relates to a broadband access by utilizing the HFC / HFT technology for households and small businesses. The HFC / HFT technology is a provisional access technology for B-ISDN until the fiber network becomes sufficiently cost-effective to be used for "end-to-end" transmissions.

The invention is based on the combination of HFC and HFT and uses the latest advances in these technologies.

The full duplex bandwidth provided by the present invention is more than sufficient for most broadband services that customers will utilize.

ATM has also been proposed as a transmission mode for the HFC / HTF technology due to the many advantages of this transmission system.

By using ATM, uninterrupted integration is achieved between CPE, LEX and the access network units.

The elements covered by the HFC / HFT technology have been identified, and their functions have been described. Most standards produced for ATM can be used in HFC / HFT technology.

The above is to be considered only as an embodiment of the present invention and the scope of the invention is limited only by what is stated in the appended claims.

Claims (11)

10 15 20 25 30 35 i ”504 570 EAIENIKRBY Device in a telecommunication network enabling broadband two-way communication between a communication equipment and a subscriber equipment, wherein it utilizes an HFC technology in transmitting information from said communication equipment to said subscriber equipment (downlink) and an HFT technology in transmitting information from said subscriber equipment. subscriber equipment for said communication equipment (uplink), characterized in that said HFT technology uses ADSL for communication traffic on said uplink, an ADSL module acting as a multiplexer serving both a computer and a setting terminal (ST) for transmission on the uplink and the ADSL module multiplies communication traffic before transmission to ISDN and POTS. Device according to claim 1, characterized in that said subscriber equipment is arranged in a household, dwelling or in a small company. Device according to claim 2, characterized in that said communication equipment is preferably a VOD server. Device according to claim 1, characterized in that said HFC technology uses the cable TV network on the downlink and that the HFT technology uses UTP on the uplink. Device according to claim 4, characterized in that said UTP consists of the public two-pair telephone copper network. Device according to any one of the preceding claims, characterized in that said HFC technology together with said HFT technology uses FDM. Device according to any one of the preceding claims, characterized in that a residential network unit (NNE) delivers broadband signals to said subscriber equipment via said cable TV network and receives broadband signals from said subscriber equipment via said two-pair copper network. Device according to one of the preceding claims, characterized in that the HFC technology and the HFT technology use ATM as the transmission mode. Method in a telecommunication system for broadband telecommunications between a communication equipment and a subscriber equipment, wherein in communication from said communication equipment, preferably a VOD server, broadband information is transmitted by means of HFC technology via existing cable TV network to said subscriber equipment, and in communication from said subscriber equipment, preferably a computer, video equipment, telephone equipment, TV equipment, broadband information is transmitted by HFT technology via the public two-pair telephone network to said communication equipment, characterized in that said HFT technology uses ADSL for ADSL on said uplink, an ADSL module acting as a multiplexer serving both a computer and an uplink transmission terminal (ST), said broadband information from said subscriber equipment to said communication equipment being multiplexed by said ADS L-module for POTS and ISDN before transmission via UTP. Method according to claim 9, characterized in that the broadband information is transmitted by means of ATM. Method according to any one of claims 9 or 10, characterized in that said subscriber equipment is arranged in a household, dwelling or in a small company.