GB2386286A

GB2386286A - Combined VoDSL and POTS system with integrated access device/VoDSL to POTS converter and telephones connected to common line via isolating filters

Info

Publication number: GB2386286A
Application number: GB0205406A
Authority: GB
Inventors: Paul David Orton Mason
Original assignee: DATAFLEX DESIGN COMM Ltd
Current assignee: DATAFLEX DESIGN COMM Ltd
Priority date: 2002-03-07
Filing date: 2002-03-07
Publication date: 2003-09-10
Also published as: GB0205406D0

Abstract

A broad band POTS signal is derived from an ADSL signal utilizing an integrated access device (12). The broadband POTS signal is then fed back into the transmission system (11) via a low pass filter (30). The integrated access device (12) is also arranged to receive POTS signals from telephony equipment (20-1-20-n) connected to the transmission system (11) and incorporate signals encoding the received POTS signals into outgoing ADSL signals. The telephony equipment (20-1-20-n) is prevented from receiving ADSL signals on the transmission system (11) by further low pass filters (21-1-21-n) connecting the telephony equipment (20-1-20-n) to the transmission system (11). By utilizing the integrated access device to generate POTS signals and supplying these signals to the transmission system (11) a means is provided to distribute telephony signals derived from an ADSL signal received by the integrated access device (12).

Description

METHOD AND APPARATUS FOR COMBINED BASE BAND POTS AND DSL DISTRIBUTION IN CUSTOMER PREMISES The present application concerns a method and apparatus for combined base band POTS and DSL distribution in customer premises.

With the advent of broadband services to residential and small to medium enterprise environments, various techniques have been used to enable the local loop from the telephone exchange to the customer premises to be used for carrying both broadband services and conventional telephony services. These usually involve splitting the frequency spectrum into a low frequency base band for carrying POTS services and one or more high frequency bands for carrying the digital subscriber loop (DSL) services. Various standards exist for these DSL services generically termed XDSL, however the most frequently used in this way is asymmetrical digital subscriber loop or ADSL.

In a typical installation, at the local exchange, the ADSL service from a DSL access multiplexor (DSLAM) is combined with the telephony service from the standard exchange line card using a device conventionally termed a splitter. The combined low frequency POTS signals and the high frequency DSL signals are then passed onto the

pair of copper lines which connects the exchange to a subscriber's premises. Signals originating from the subscriber are processed by the splitter and divided into two parts to return to appropriate end points. At the subscriber end of the local loop another splitter is used to separate the combined signals to feed the subscriber's telephone wiring and a DSL modem for the broadband services.

Although it is possible to install a splitter into the master socket of subscriber premises, this job needs to be performed by a trained telephone engineer and is therefore a major cost in installation. This has led to an alternative approach which does not require the services of an engineer and is instead suitable for user installation. In such a configuration a number of passive low pass filters are supplied to the subscriber along with a DSL modem which contains its own high pass filter. The low pass filters are then inserted in series with each piece of telephony equipment which is connected to the wiring within the customer's premises. Together these low pass filters and the high pass filter within the DSL modem perform the function of the splitter previously installed at the master socket.

There is now emerging a new family of DSL devices, termed integrated access devices (IADs) which provide an

integrated telephony and data service, both of which carried by the digital DSL link. These IADs provide one or more telephone ports as well as a high speed data port. This is making the base band POTS service redundant such that lines can now be provisioned without this POTS service being present.

A problem encountered, however, is that of IAD location. Without re-wiring the telephones of the customer's premises, it is often difficult to provide both a DSL connection to the IAD and a set of convenient telephony connection out of it, whilst still maintaining a location which is conveniently close to data processing equipment (e. g. a personal computer) which is to take advantage of the high speed DSL data service.

The present invention has been designed with a view to overcome the above problem.

In accordance with one aspect of the present invention there is provided a communications system in which a broad band POTS signal is derived from an ADSL signal utilizing an integrated access device. The broadband POTS signal is then fed back into the transmission system via a low pass filter. The integrated access device is also arranged to receive POTS signals from telephony equipment connected to the transmission system and incorporate signals encoding the

received POTS signals into outgoing ADSL signals. The telephony equipment is prevented from receiving ADSL signals on the transmission system by further low pass filters connecting the telephony equipment to the transmission system. By utilizing the integrated access device to generate POTS signals and supplying these signals to the transmission system, a means is provided to distribute telephony signals derived from an ADSL signal received by the integrated access device.

Further aspects and embodiments of the present invention will now be described with reference to the accompanying drawings in which: Figure 1 is a schematic block diagram of a communications network including an integrated access device in accordance with a first embodiment of the present invention; Figure 2 is a schematic block diagram of a POTS conversion unit of the integrated access device of Figure 1; and Figure 3 is a schematic block diagram of a communications network in accordance with a second embodiment of the present invention.

Referring to Figure 1 a local exchange 1 is shown containing splitter 2 and is connected via the local loop 3 to the master socket 4 of a subscriber's premises 5.

The splitter 2 is arranged to receive signals from the local loop 3 and divide the signals into high frequency ADSL signals and low frequency broadband POTS signals.

The ADSL signals are converted into a high speed data signal by a ADSL access multiplexor (DSLAM not shown) and then passed to a high speed data service 7. The DSLAM (not shown) is also arranged to receive signals from the data transmission service 7. Signals received from the high speed data service 7 are converted to ADSL signals and passed through the splitter 2 and onto the local loop 3. In contrast to a conventional arrangement where the splitter 2 causes POTS signals to be passed to a telephony transmission service 9, in this embodiment the splitter 2 is modified to disable the transfer of POTS signals to the telephony transmission service 9.

As will be described in detail later in accordance with the present invention the local loop 3 is arranged to transmit both telephony and data signals solely in the frequencies corresponding to the high frequency ADSL signal. Thus in this way the data transmission service 7 is able to provide a telephony transmission service for the transmission of telephony signals previously transmitted as a low frequency POTS signals.

Provided within the customer's premises 5 are a number of extension sockets 10-1, 10-2 10-n, which are

connected to each other and the master socket 4 via conventional wiring 11 within the customer's premises 5. Connected to one of the extension sockets 10-1 is an integrated access device (IAD) 12. The IAD 12 is connected to a data processing apparatus 13 such as a personal computer via a data port 14 and to a telephone 16 via a telephone port 18. A number of other telephones 20-1-20n are connected to the other extension sockets 10- 2-10-n via low pass filters 21-1-21-n each of which are arranged to prevent high frequency ADSL signals present on the conventional wiring 11 from activating the telephones 20-1 and 20-n respectively.

In accordance with the present invention the integrated access device (IAD) 10 comprises a high pass filter 23 to separate ADSL signals from low frequency broadband POTS signals. The high pass filter 23 is connected to a DSL modem 24 arranged to convert digital data into ADSL data and vice versa. The DSL modem 24 is also connected to a multiplexor 26 which divides digital data from the modem 24 into digital voice data and data intended for use by the data processing apparatus 13.

The digital voice data is passed to a POTS conversion unit 28 which converts the digital voice data into a corresponding POTS signal. The other data is passed via the data port 14 to the data processing apparatus 13.

The POTS signal generated by the POTS conversion unit 28 is passed via the phone port 18 to the telephone 16 connected to the integrated access device 10. The integrated access device 12 additionally includes a low pass filter 30 which connects the POTS conversion unit 28 back to the extension 10-1 to which the integrated access device 12 is connected.

In accordance with the present invention when an ADSL signal is received from the local loop 3 it passes via the master socket 4 through the conventional wiring 11 which causes the ADSL signal to be transmitted to each of the extension sockets 10-1,10-2, 10-n.

In the case of the extension sockets 10-2,10-n to which telephones 20-1-20-n are connected, the low pass filters 21-1-21-n prevent the high frequency ADSL signal from passing to these telephones 21-1-21-n. However, in the case of the extension 10-1 to which the IAD 12 is connected the ADSL signal passes through the high pass filter 23 and is received by the DSL modem 24. The signal is processed and a generated data signal is passed to the multiplexor 26 which separates any digital voice signal included within the data signal from data intended for use by the data processing apparatus 13. The computer data is then passed via the data port 14 to the data processing apparatus 13 whereas the digital voice

signal, which in this embodiment is taken to include encoded POTS control and status signals is passed to the POTS conversion unit 28.

When the POTS conversion unit 28 receives a digital voice signal it converts the received digital data into a POTS signal. Figure 2 is a schematic block diagram of the POTS conversion unit 28 in accordance with this embodiment of the present invention. The POTS conversion unit 28 comprises a coder/decoder 35 which decodes the received digital voice signal to generate an expanded voice signal which is then passed to a digital/analogue converter 37. The digital/analogue converter 37 then processes the expanded voice signal to generate a corresponding analogue signal which is passed to a subscriber line interface 38. The subscriber line interface 38 then passes the generated derived POTS signal which includes any control and status signals encoded in the original digital voice signal both to the phone port 18 and the low pass filter 30 of the IAD 12.

The subscriber line interface 38 is also arranged to receive POTS signals from the low pass filter 30 and the phone port 18 and pass the received POTS signals to an analogue/digital converter 39 which then passes generated digital signals derived from the POTS signals received by the subscriber line interface 38 to the

encoder/decoder 35. The encoder/decoder 35 then proceeds to encode and compress the received digital signals to generate a digital voice signal which is passed to the multiplexor 26 of the IAD 12.

Returning to Figure 1 when the POTS conversion unit 28 has generated an analogue POTS signal from the digital voice data received from the multiplexor 26 the POTS signal is passed to the telephone 16 via the phone port 18 of the IAD 12. The POTS signal is also passed to the other telephones 20-1-20n connected via the conventional wiring 11. In the case of the POTS signal transmitted via the conventional wiring 11 the POTS signal initially passes through the low pass filter 30 to the exchange socket 10-1. From here the derived POTS signal is prevented from passing back to the DSL modem 24 by the presence of the high pass filter 23. The POTS signal can, however, pass via the conventional wiring 11 to the other extension sockets 10-2; 10-n of the subscriber's premises 4 via the filters 21-1-21n to the telephones 20- 1.

Thus by connecting the POTS conversion unit 28 via a low pass filter 30 back to the extension socket 10-1 a means is provided by which the derived POTS signal can be transmitted by the conventional wiring 11 throughout the subscriber premises 5. The provision of this low

pass filter 30 and additional connection to the extension socket 10-1 therefore enables all of extension sockets 10-2; 10-n to be utilized to receive the derived POTS telephone signals and therefore enables the conventional wiring 11 and extension sockets 10-2; 10-n to solve the problem of distributing a DSL based telephony service throughout the subscriber's premises 5 without needing to rewire the subscriber's premises 5.

When data is to be transmitted from the subscriber's premises 5 back to the local exchange 1, in the case of POTS signals obtained from the telephones 20-1-20-n the POTS signals pass via the low pass filters 21-1,21-n and the extension sockets 10-2,10-n and the conventional wiring 11 to the extension socket 10-1 to which the integrated access device 12 is attached.

These POTS signals are then prevented from entering the DSL modem 24 by the high pass filter 23. The POTS signals are instead passed via the low pass filter 30 to the POTS conversion unit 28. The POTS conversion unit 28 also receives any POTS signals from the telephone 16 connected to the IAD 12 via the phone port 18.

When a POTS signal is received by the POTS conversion unit 28, the subscriber line interface 38 of the POTS conversion unit 28 is caused to pass an analogue signal to the analogue/digital converter 39. The

analogue/digital converter 39 then generates a corresponding digital signal which is then encoded by the coder/decoder 35 to form digital voice data which is passed to the multiplexor 26. The multiplexor 26 also receives digital data from the data processing apparatus 13 via the data port 14. The multiplexor 26 combines the data received from the data processing apparatus 13 with any digital voice data received from the POTS the conversion unit 28 and then passes the combined signal to the DSL modem 24. The DSL modem 24 then processes the received signal and passes it as an ADSL signal via the high pass filter 23 to the extension socket 10-1 to which the IAD 12 is attached.

When the extension socket 10-1 receives the ADSL signal from the IAD 12, the high frequency ADSL signal.. is prevented from activating the POTS conversion unit 28 by the presence of the low pass filter 30. Similarly, although the high frequency ADSL signal can pass to the conventional wiring 11 from the extension socket 10-1 the ADSL signal is prevented from passing to the telephones 12-1-12-n by the presence of the low pass filters 21-1- 21-n. The ADSL signal together with any derived POTS signal present on the conventional wiring 11 is, however, able to pass via the master socket 4 and the local loop 3 to the local exchange 1 where the splitter 2 causes the

ADSL signal to be passed to the DSLAM (not shown) to be converted into a high speed signal which is then passed to the data transmission service 7. The data transmission service 7 may then transfer the high speed signal to another local exchange 1 which can then pass derived ADSL signals via another local loop 3 to other subscriber premises 5 which are arranged to receive ADSL signals.

The provision of a connection from the POTS conversion unit 28 of an integrated access device 12 via a low pass filter 30 back to the extension 10-1 enables a POTS signal derived from the digital voice data component of a received ADSL signal to be transmitted via the conventional wiring 11 throughout a customer's premises. The provision of such a low pass filter 30 and connection therefore enables a DSL based telephony service to be more easily distributed and hence enables a data service provider to compete for the transmission of telephony services with a conventional POTS telephony transmission service.

A second embodiment of the present invention will now be described with reference to Figure 3. In the first embodiment the splitter 2 of a local exchange 1 was modified to disable the transfer of POTS signals to a telephony transmission service 9. In contrast in this

embodiment the transmission of POTS signals from the splitter 2 of the local exchange 1 remains in place. However, in this embodiment the master socket 4 of a subscriber's premises 5 is modified to incorporate a high pass filter 40 to prevent low frequency POTS signals from passing via the master socket to the local loop 3.

In this embodiment the integrated access device (IAD) 12 comprises a conventional integrated access device which does not include an additional low pass filter 30. In this embodiment instead of the phone port 18 of the integrated access device 12 being connected to a telephone 16, the phone port 18 is connected to an extension socket 10-1 via a low pass filter 42 separate from the integrated access device 12.

In this embodiment an ADSL signal received via the local loop 3 passes via the master socket 4 to the integrated access device 12 where it is processed the same way as has previously been described to generate a POTS signal and a data signal. As in the first embodiment the data signal is passed to a data processing apparatus 13. In this embodiment, however, the derived POTS signal passes via the phone port 18 and the low pass filter 42 to an extension socket 10-1 connected to the conventional wiring 11 of the subscriber's premises 5.

This enables the derived POTS signal to be passed via the

other extension sockets 10-2,10-n and low pass filters 21-1-21-n to the telephones 20-1-20-n. POTS signals originating from the telephones 20-1-20-n are prevented from passing directly to the local loop 3 by the high pass filter 40 incorporated within the master socket 4.

However, the POTS signal may pass via the low pass filter 42 to the phone port 18 of the IAD 12 where it can be processed and incorporated into an ADSL signal which passes via the high pass filter 40 of the master socket 4 to the local loop 3 and hence via the splitter 2 of the local exchange 1 to a DSLAM (not shown) which converts the ADSL signal into a high speed data signal which is passed to the data transmission service 7.

It will be appreciated that in this embodiment by incorporating a high pass filter 40 within the master socket 4 of a subscriber's premises 5 the derived POTS signals present on the conventional wiring within the subscriber's premises 5 are prevented from reaching the local exchange 1. Thus in this embodiment it is not necessary to disconnect the splitter 2 of the local exchange 1 from the telephony service 9 as no POTS signals are received by the splitter 2 which could be passed to the telephony service 9.

Although in the above two embodiments an integrated access device 12 has been described as being connected

to be that an extension socket 10-1 or an extension socket 10-1 and a master socket 4 it will be appreciated that in other embodiments the integrated access device could be connected either just to a master socket 4 or alternatively to two extension sockets 10-1.

It will also be appreciated that an integrated access device 24 could be arranged to have a single connection to either the master socket 4 or an extension socket 10-1 where the connection from the socket 4; 10-1 incorporates a high pass filter 24 and a low pass filter 42 to separate ADSL signals and POTS signals received from the socket 4 ; 10-1.

Further, it will be appreciated that although the above embodiments refer to telephones 20-1-20-n being connected via filters 21-1-21-n, the present invention is applicable to any form of telephony terminal equipment. Thus, for example, the present invention could be utilised to distribute signals to fax machines or conventional modems instead of telephones.

Alternatively, a number of different types of telephony terminal equipment could be connected to the conventional wiring 11 and receive signals in the manner described above.

Claims

CLAIMS 1. A communications network comprising: a transmitter/receiver for transmitting and receiving signals; a plurality of telephony terminals; an integrated access device operable to derive telephony signals in a first frequency band from received signals in a second frequency band separate from said first frequency band and operable to generate signals in said second frequency band corresponding to received telephony signals in said first frequency band; and a transmission network interconnecting said transmitter/receiver, said plurality of telephony terminals and said integrated access device, wherein each of said plurality of telephony terminals is connected to said transmission network via a filter operable to prevent passage of signals in said second frequency band; and said integrated access device is connected to said transmission network via a first connector operable to permit passage of signals in said second frequency band and a second connector operable to prevent passage of signals in said second frequency band said integrated access device being arranged to process signals received

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via said first connector to derive telephony signals in said first frequency band and to output said telephony signals via said second connector; and to process telephony signals received via said second connector to generate signals in said second frequency band corresponding to said received telephony signals and to output said generated signals via said first connector.
2. A communications network in accordance with claim 1, wherein said first frequency band comprises frequencies corresponding to POTS signals and said second frequency band comprises frequencies corresponding to ADSL signals.
3. A communications network in accordance with claim 1 or claim 2, wherein said integrated access device comprises: means for deriving digital data from signals received in said second frequency band; means for extracting digital voice data from said digital data derived from signals in said second frequency band; and means for converting said extracted digital voice data into a signal in said first frequency band.

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4. A communications network in accordance with claim 3, wherein said integrated access device is further operable to output a data signal comprising digital data derived from said signals in said second frequency band which is not utilized by said means for converting said extracted digital voice data.
5. A communications network in accordance with claim 3 or claim 4, wherein said integrated access device further comprises: means for receiving a data signal; means for combining said data signal with voice data derived from a telephony signal in said first frequency band; and means for processing combined voice data and said received data to generate a signal in said second frequency band.
6. A method of distributing analogue signals comprising : providing a transmission network in accordance with any preceding claim; receiving analogue signals in said second frequency band utilizing said transmitter/receiver and passing said signals to said integrated access device via said

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transmission means and said first connector; utilizing said integrated access device to process received signals in said second frequency band to generate telephony signals in said first frequency band; routing telephony signals in said first frequency band between said telephony terminals and said integrated access device via said second connector, said transmission network and said plurality of filters; utilizing said integrated access device to generate signals in said second frequency band encoding telephony signals in said first frequency band received via said second connector; and routing said generated signals in said first frequency band to said transmitter/receiver via said first connector and said transmission network.
7. An integrated access device operable to derive telephony signals in a first frequency band from received signals in a second frequency band separate from said first frequency band and operable to generate signals in said second frequency band corresponding to received telephony signals in said first frequency band; said integrated access device comprising a first connector operable to permit passage of signals in said second frequency band and a second connector operable to

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prevent passage of signals in said second frequency band, said integrated access device being arranged to process signals received via said first connector to derive telephony signals in said first frequency band and to output said telephony signals via said second connector; and to process telephony signals received via said second connector to generate signals in said second frequency band corresponding to said received telephony signals and to output said generated signals via said first connector.
8. An integrated access device in accordance with claim 7, wherein said first frequency band comprises frequencies corresponding to POTS signals and said second frequency band comprises frequencies corresponding to ADSL signals.
9. An integrated access device in accordance with claim 7 or claim 8, wherein said integrated access device comprises : means for deriving digital data from signals received in said second frequency band; means for extracting digital voice data from said digital data derived from signals in said second

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frequency band; and means for converting said extracted digital voice data into a signal in said first frequency band.
10. An integrated access device in accordance with claim 9, wherein said integrated access device is further operable to output a data signal comprising digital data derived from said signals in said second frequency band which is not utilized by said means for converting said extracted digital voice data.
11. An integrated access device in accordance with claim 9 or claim 10, wherein said integrated access device further comprises: means for receiving a data signal; means for combining said data signal with voice data derived from a telephony signal in said first frequency band; and means for processing combined voice data and said received data to generate a signal in said second frequency band.
12. A communications network substantially as herein described with reference to the accompanying drawings.

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13. A method of distributing analogue signals substantially as described herein with reference to the accompanying drawings.