CA2228876A1 - Method for high-speed transmission and reception of information - Google Patents

Abstract

A digital access system (5,50, 500, 5000) includes a pair of DSL modems (16, 17) for high-speed downstream transmission of data across a twisted wire pair (15) from a central office (11) and a customer premises (10). Voice-band signalsoriginating at the customer premises may be transmitted across the same wire pair by injecting the signals at a frequency below that of the data transmitted by the DSL
modems.

Description

CA 02228876 1998-02-0~

METHOD FOR HIGH-SPEED TRANSMISSION AND RECEPTION OF
INFORMATION
Technical Field This invention relates to a technique for communication of voice and high-speed data.

Background Art The proliferation of the INTERNET, as well as proprietary on-line services, has prompted demand for the ability to at least down load information at very high rates. To that end, present-day voice modems now provide data transfer rates as high as 56 Kbs over conventional telephone lines. Data transfer rates of 128 Kbs15 may be obtained using special services such as Integrated Services Digital Network (ISDN). Yet, even higher speeds, as much as 10-27 Mbs, may be obtained using coaxial cable. Generally, the rate of downstream tr~n.~mi~ion of information is more critical than upstream information. Most on-line users tend to download large files, as compared to the size of files uploaded to the head end. For that reason, 20 users prefer high downstream tr~n~mi~ion speeds.
U.S. Patent 5,347,304 discloses a technique for high speed downstream tr:~n.~mi~ion of information from a head end to a downstream customer over a coaxial cable. A cable television modem at the head end modulates the information intended for the downstream customer onto a standard 6 MHz channel for 25 tr~n~mi.~.~ion on the coaxial cable. At the customer's premises, another cable television modem demodulates the downstream information. Upstream information from the customer premises is modulated onto a twisted wire pair via a conventional voice-band modem for demodulation at a central office or Information Service Provider (ISP). Using the low-speed upstream path, the customer can signal the 30 central office or ISP to download information via the coaxial cable at relatively high speeds.

CA 02228876 1998-02-0~

While the approach described in U.S. Patent No. 5,347,304 achieves high-speed data tr~nsmission from a head end to a downstream customer, the technique suffers from the disadvantage that two separate transmission paths are needed.
Thus, a customer must obtain a coaxial cable link, via a cable television service S provider, for downstream data transmission, and a twisted wire pair from a telephone company, for upstream tr~n~mis~ion.
Thus, there is a need for a technique for providing high-speed downstream data tr~nsmission, and upstream data tr~nsmission, across a single communications channel, such as a twisted wire pair.
Brief Summary of the Invention Briefly, in accordance with a preferred embodiment, a method is provided for high-speed downstream data tr~n~mis.~ion over a wire pair from a head end to a 15 customer's premises and upstream data tr~n.smission, over the same wire pair, from the customer's premises to the head end. ln accordance with the method, a Digital Subscriber Line (DSL) modem at the head end modulates digital signals into loop signals. for high-speed tr~nsn-is~ion across the wire pair to the customer's premises at which a second DSL modem demodulates the loop signals into digital signals.
20 Voice-band information at the customer's premises is placed on the same wire pair for tr~n.smission to the head end at a frequency below the downstream information modulated on the wire pair by the DSL modems. The voice information typically originates from a telephone station set at the customer premises. Analog voice information may be placed on the wire pair via a first filter at the customer premises 25 for removal at the head end via a second filter and vice versa. Alternatively, the voice information may be digitized, via a CODEC or the like, at the customer premises, for digital tr:~nsmi~.sion on the wire pair to the head end. The voiceinformation may also include digital information modulated into voice-band signals via a voice-band modem at the customer premises for analog or digital tr~n.smission 30 to the head end in the manner just described. In this way, a customer may send CA 02228876 1998-02-0~

information at relatively low speeds (e.g., 28 Kbs) to the head end to initiate a data call, authenticate a transaction, or upload electronic mail or small files whileenjoying relatively fast (up to 8 Mbs or even 25 Mbs) downstream data tr~n.smi~sion from the head end over the same wire pair.

Brief Summary of the Drawings FIGURE 1 shows a block schematic diagram of a first access system in accordance with the invention for achieving bi-directional DSL voice and data lO tr~n.smi~sion over a single wire pair;
FIGURE 2 shows a block schematic diagram of a second access system in accordance with the invention for hybrid DSL voice and data tr~n~mi~sion over a single wire pair;
FIGURE 3 shows a block schematic diagram of a third access system in 15 accordance with the invention for DSL data tr~n.smi.s.sion and digitized voice tr~n.smi~sion over a single wire pair; and FIGURE 4 shows a block schematic diagram of a fourth access system in accordance with the invention for DSL data transmission over a single wire pair and voice tr~n.smis.sion across another communications channel.
Detailed Description FIGURE 1 depicts a functional block diagram of a first DSL access system 5 in accordance with the invention for the exchange of information between a 25 customer premises 10 and a central office l l m~int~ined by provider of telecommunications services. The customer premises 10 may be a home or business located at which are a digital appliance 12, such as a personal computer or a Set-Top Box, and an analog telephone station set 14.
Pursuant to the invention, the customer premises 10 exchanges both data and 30 voice information with the central office 1 l over at least one wire pair 15, typically, CA 02228876 1998-02-0~

a twisted wire pair. To exchange data, the customer premises includes a Digital Subscriber Line (DSL) modem 16 linked to the digital appliance 12 via an internal bus, a parallel port connection, or a 10 Base T interface. The DSL modem 16 functions serves to modulate digital signals from the digital appliance 12 onto a 5 twisted wire pair 15 for tr~n~mi~sion to the central office 11 as well as to demodulate signals received from the central office over the same wire pair. DSLmodems are known in the art and provide tr~n.~mi~sion and reception of digital data at high rates by modulating and demod~ ting such data at frequencies well above 3 KHz at which conventional voice grade modems operate.
To interface with the DSL modem 16 at the customer premises 10, the central office 11 includes at least one DSL modem 17 connected to the opposite end of the wire pair 15. In practice, the central of fice 11 serves a plurality of customers premises, each served by at least one separate wire pair 15. To that end, the central office 11 typically includes a plurality of DSL modems 17-17, each available for15 connection to a wire pair 15 serving a separate customer premises 10. The outputs of the modems 17-17 are combined via a multiplexer/router 20 for tr~n~mi~sion onone of trunks 22, typically having DS 1, DS3 or OC3 bandwidth, to a Data Network, Information or INTERNET Service Provider.
The nature of the multiplexer/router 20 will depend of the nature of the 20 output interface associated with the DSL modems 17-17. In the illustrated embodiment, each DSL modem 17 has an Ethernet 10 base T interface, in which case, the multiplexer/router 20 takes the form of a router for routing signals onto the trunk 22. The DSL modems 17-17 may employ other output data protocols: such as frame relay, ATM or FDDI; to create time-division multiplexed signals (in which 25 case, the multiplexer/router 20 would take the form of a TDM multiplexer) or packet multiplexed signals wherein the multiplexer/router 20 could be a packet multiplexer, router, or switch.
In the access system 5 depicted in FIG. 1, the DSL modems 16 and 17 at the customer premises 10 and at the central office 1 1, respectively, possess the 30 capability to transmit and receive data at relatively high speeds across the twisted CA 02228876 1998-02-0~

wire pair 15. In practice, such high tr~n.~mi.csion rates can be obtained provided the following constraints are satisfied:
l . The distance between the customer premises 10 and the serving central office 11 is relatively short (e.g., 2-3 miles) depending on the gauge of the twisted wire pair 15 and the tr~n~mi~sion rate of the modems;

2. No intervening electronic devices or load coils are present between the DSL modems 16 and 17; and 3. There are a limited number of bridged taps in the loop between the modems.
Should any of these constraints not be satisfied, alternative access technology,such as a Tl line or a radio channel will be necessary in place of the twisted wire pair 1 5.
In accordance with the invention, the same twisted wire pair 15 that 15 carries data between the customer premises 10 and the central office 1 1 can simultaneously carry voice information as well. To that end, voice signals from the telephone station set 14 at the customer premises 10 are placed on the twisted wire pair 15 through a filter 24 at a frequency below the frequency at which theDSL modems modulate data onto the twisted wire pair. Typically, the DSL
20 modems depicted in FIG. 1 modulate data at a frequency above 3 KHz. Thus, the voice traffic, of the type associated with Plain Old Telephone Service (POTS) which operates in a conventional frequency range (e.g., at or below 3 KHz), can be injected onto the twisted wire pair 15 via the filter 24 in accordance with the invention.
At the central of fice 11, a filter 26 serves to strip-off the voice information on the twisted wire pair 15 upstream of the associated one of the DSL modems 17-17 serving the wire pair. The voice information stripped by the filter 26 is carried on a trunk 28 to a voice network, such as m:~int~ined by a Local Access Provider. POTS voice signals from other telephone station sets 30 (not shown) may also be received at the central office 11 for tr~n.cmi.~sion on at CA 02228876 1998-02-0~

least one trunk 29 to the voice network. As may now be appreciated, by transmitting the voice information on the twisted wire pair 15 at a frequency below that of the data modulated by the DSL modems 16 and 17, the twisted wire pair can be made to carry both voice and high speed data.
FIG 2 shows a hybrid DSL access system 50 for voice and data tr~n~mi~sion similar to the access system 5 of FIG. 1. Therefore like elements have been depicted by like reference numbers. Thus, the DSL access system 50 includes DSL modems 16 and 17- 17 at the customer premises 10 and at the central of fice 11, respectively, to enable high speed downstream tr~n.~mi.~.sion data from the central office to the 10 customer premises. Like the access system 5 of FIG. 1, the access system 50 of FIG.
2 includes a filter 24 at the customer premises 10 for separating voice information on the twisted wire pair 15 at a frequency below that of the DSL modems 16 and 17- 17.
The access system 50 of FIG. likewise includes a filter 26 at the central of fice 11 to strip offthe voice information for tr~n~mi.~.sion to the voice network on the trunk 28.
In contrast to the access system 5 of FIG. 1, the DSL modem 16 at the customer premises 10 of the access system 50 of FIG. 2 only possesses the ability to receive data, affording a cost savings over the DSL modem 16 of FIG. 1 that has both receive and transmit capabilities. Typically, the central office 11 possesses the DSL modems 17- 17 which support the ability to transmit only, further reducing costs.
To afford the customer premises 10 an upstream data tr~n~mi~sion capability, a voice-band modem 30, of the type well known in the art, either internal to, orseparate from the digital appliance 12, modulates upstream digital signals from the customer's digital appliance 12 into analog signals. These analog signals modulated into the voice-band via the modem 30 are input to the filter 24 for tr~n.cmission via the twisted wire pair 15 to the central office 11. At the central office 11, the analog signals modulated into the voice-band are stripped by the filter 26 of FIG. 3 for tr~n~mission on the trunk 28 to a conventional voice-band modem pool of the sameinformation provider supplying the customer premises 10 with data . As discussedpreviously, voice-band modems of the type which comprise the modem 30 typically CA 02228876 1998-02-0~

achieve a data tr~ncmic.sion rate of 9.6 Kbs-56 Kbs. Such a rate is generally satisfactory for upstream data tr~n.smicsion since most customers upload relatively small files as compared with very large files that are commonly downloaded. Thus, in accordance with the access system 50 of FIG.2, large files can be rapidly downloaded via the DSL modem 17 at the central of fice 11 of FIG.2 to the receive-only DSL modem 16 at the customer premises 10. At the same time, voice information from the telephone set 14, or upstream data from the digital appliance 12, modulated into the voice-band via the modem 30, can be sent over the twistedwire pair 15 via the filter 24 for receipt at the central office 11. In this way, the 10 access system 50 of FIG.2 can achieve high-speed downstream data tr~n.cmi.ccion from the central office 1 1 to the customer premises 10, as well as transmission of voice and ~I,ea l- data from the customer's digital appliance 12.
FIG.3 depicts a third digital access system 500 for voice and data tr~n.cmiccion similar to the access systems 5 and 50 of FIGS.l and 2, respectively.
15 Therefore like elements have been depicted by like reference numbers. Thus, the access system 500 includes DSL modems 16 and 17-17 at the customer premises 10 and at the central office 11, respectively, to enable high speed downstream tr~ncmicsion data from the central office to the customer premises via the twisted wire pair. Like the access system 50 of FIG. 2, the DSL modem 16 connected to the 20 digital appliance 12 at the customer premises 10 within the access system 500 of FIG.3is receive only. Thus, like the DSL access system 50 of FIG. 2, the DSL
access system 500 of FIG.3 includes a voice-band modem 30 for mod~ ting digital signals from the customer's digital appliance 12 into analog signals for upstream tr~n.cmi~cion to the central office 11 via the twisted wire pair.
In contrast to the DSL access system 50 of FIG. 2, the DSL access system 500 of FIG. 3 includes a Coder-Decoder (CODEC) 32 connected to either a conventional analog phone 14, or to the voice-band modem 30, for digitizing thissignal for input through the DSL modem 16 onto the twisted wire pair 15, or onto a second wire pair 33 (shown in phantom). The CODEC 32 may also digitize voice 30 information from the telephone station set 14 (as well as other sets (not shown)) for CA 02228876 1998-02-0~

input through the DSL modem 16 for tr~n.cmieeion on one of the twisted wire pairs 15 and 33~ rather that transmit the voice information as an analog signal via the filter 24. For that reason, the filter 24 at the customer premises 10 (as well as the filter 26 at the central office 11) are depicted in phantom since these elements may be 5 elimin~ted if the voice information is digitized via the CODEC 32.
When the voice information is digitized via the CODEC 32 and is input on the twisted wire pair 15 or on the twisted wire pair 33, the digitized voice information will be received at one of the DSL modems 17-17 at the central of fice 11. The DSL modems 17-17 demodulate the digitized voice information and 10 provide the information as a separate DSO (64 Kbs) signal on a trunk 34. Suchvoice signals are supplied, together with voice signals on the POTS trunks 28 and 29, to the voice network, or modem pool of an information services provider.
Alternatively, the voice signals received and stripped via the filter 26 could be multiplexed with other voice signals to form a DS 1 signal. Alternatively, the voice 15 signals could be packetized and routed over a data network.
As may be appreciated, the access system 500 advantageously accomplishes voice tr~n.emieeion via the CODEC 32, while downstream data tr~nemiesion is provided via the DSL modems 16 and 17 as previously discussed. Moreover, digitization of the voice information by the CODEC 32 affords the ability to support 20 multiple separate voice signals, in contrast to the ability of the filters 24 and 26 to support a single signal.
The DSL access system 50 of FIG. 3 typically utilizes a single twisted wire pair 15 to L~ il data between the DSL modems 16 and 17. In some instances it may be desirable to download data from the central office 11 to the customer 25 premises via the twisted wire pair 15 and upload data via a twisted wire pair 34.
Voice data could be transmitted via the twisted wire pair 34, or via the wire pair 33 dedicated for such voice-band information.
FIG. 4 depicts a fourth digital access system 5000 for voice and data tr~n.emieeion similar to the access systems 5, 50, and 500 of FIGS. 1, 2, and 3,30 respectively. Therefore like elements have been depicted by like reference numbers.

CA 02228876 1998-02-0~

Thus, for example, the access system 5000 includes DSL modems 16 and 17-17 at the customer premises 10 and at the central of fice 11, respectively, to enable high speed downstream tr~n~mi~.sion data from the central office to the customer premises. Like the access system 50 and 500 of FIGS. 2 and 3, the DSL modem 16 5 connected to the digital appliance 12 at the customer premises 10 within the access system 5000 of FIG. 4 is receive only. Thus, like the DSL access systems 50 and 500 of FIGS. 2 and 3, respectively, the DSL access system 5000 of FIG. 4 includes a voice-band modem 30 for mocl~ ting digital signals from the customer's digital appliance 12intoanalogsignalsforupstreamtr~n~mi~siontothecentraloffice 11.
In contrast to the DSL access system 50 and 500 of FIGS. 2 and 3, the DSL
access system 5000 of FIG. 4 employs an alternative tr~n~mi~ion path for transmitting voice-band information to the central office 11. In the embodiment of FIG. 4, a wireless transceiver 34 is provided for transmitting voice signals from the telephone station set 14, and the voice-band modem 30 across a radio channel 35 for 15 receipt by a corresponding wireless transceiver 36 at the central office 11. The wireless transceiver 34 at the customer premises 10 also receives voice band information transmitted by the transceiver 36 at the central office 11. The transceiver 36 at the central office 11 is connected, via a voice trunk 38, to the Voice Network or to the Modem Pool of an information provider, in the same way as 20 POTS trunk 29. In this way, voice information is communicated from the customer premises to the Voice Network or to the Modem Pool of an information provider while information is transmitted from the central office to the customer premises via the twisted wire pair 15. Note that voice information could also be communicatedacross the twisted pair 15, as described previously, via the filters 24 and 26 (shown 25 in phantom).
The foregoing discloses a technique for dov~ ll tr~n~mi~ion of information at high speeds from a central of fice 11 to a customer premises 10 across a twisted wire pair and for tr~n~mi~eion of voice information, as well as digital signals, modulated in the voice band, from the customer premises to the central 30 office over the same twisted wire pair (or on a different channel).

It is to be understood that the above-described embotlim~nt~ are merely illustrative of the principles of the invention. Various modifications and changes may be made thereto by those skilled in the art which will embody the principles of the invention and fall within the spirit and scope thereof.

Claims (32)

1. A method for high speed transmission of digital data from a central office to a customer premises and for transmitting voice-band information from the customer premises to the central office, comprising the steps of:
modulating, at a high speed, digital information at the central office into loopsignals via a first Digital Subscriber Line (DSL) modem office for transmission to the customer premises on a first wire pair;
demodulating the loop signals at the customer premises via a second DSL
modem to yield digital signals;
transmitting voice band signals, including digital signals originating at the customer premises and modulated into the voice band via a voice band modem, at afrequency below that of the signals modulated by the first DSL modem for transmission to the central office; and stripping off at the central office the voice band signals.

2. The method according to claim 1 wherein the voice band information is transmitted from the customer premises by injecting the voice band information onto the first wire pair through a first filter and wherein the voice band information is stripped off at the central office via a second filter.

3. The method according to claim 1 wherein the voice band signals are transmitted on a wire pair the same as the digital signals at a baseband frequency corresponding to a conventional frequency range for Plain Old Telephony Service.

4. The method according to claim 1 wherein the voice band signals are transmitted on a wire pair different from the digital signals at a baseband frequency corresponding to a conventional frequency range for Plain Old Telephony Service.

5. The method according to claim 1 wherein the digital signals originating at the customer premises are generated at a digital appliance at thecustomer premises to set up a call and support low speed transmission of digitalsignals to an information services provider.

6. The method according to claim 5 wherein the digital signals further include user data communicated to the information services provider.

7. The method according to claim 1 wherein the voice band information comprises voice band signals generated by a telephone station set.

8. The method according to claim 1 wherein the second DSL modem at the customer premises modulates at a high speed digital data originating at the customer premises into high-speed loop signals and wherein the first DSL modem at the central office demodulates the loop signals received from the customer premises into digital signals.

9. The method according to claim 8 wherein the digital signals originate from a digital appliance at the customer premises.

10. The method according to claim 9 wherein the loop signals produced by the second DSL modem are transmitted over a second wire pair to the central office.

11. The method according to claim 1 wherein the voice-band signals are transmitted to the central office by first digitizing the voice band signals via a Coder-Decoder and then passing the digitized signals onto the wire pair via the first DSL to the second DSL modem which separates the digitized voice band signals.

12. The method according to claim 11 wherein the voice band signals includes digital voice-band signals originating at the customer premises and modulated into the voice band via a voice band modem.

13. The method according to claim 11 wherein the digital signals are generated at a digital appliance at the customer premises to set up a call to a information services provider.

14. The method according to claim 13 wherein the digital signals further include user data communicated to the information services provider.

15. The method according to claim 11 wherein the voice band signals include voice band signals generated by a telephone station set.

16. The method according to claim 11 wherein the voice-band signals are transmitted over the first wire pair.

17. The method according to claim 1 wherein the voice-band signals are transmitted between the customer premises and the central office over a second wire pair.

18. The method according to claim 1 wherein the voice-band signals are transmitted between the customer premises and the central office over a radio channel.

19. Apparatus for high speed transmission of information from a central office to a customer premises and for transmitting voice-band information from the customer premises to the central office, comprising:
a first wire pair connecting the customer premises and the central office;

a first Digital Subscriber Line (DSL) modem at the central office for modulating, at a high speed, digital signals at the central office into loop signals for transmission across the first wire pair to the customer premises;
a second DSL modem at the customer premises for demodulating the loop signals to yield digital signals;
means, at the customer premises, for originating voice band signals, including digital signals modulated into the voice band, at a frequency below that of signals modulated by the first DSL modem, for transmission to the central office;
means at the customer premises for injecting the voice band signals onto a communications channel for transmission to the central office; and means at the central office for stripping off the voice band signals.

20. The apparatus according to claim 19 wherein the means at the customer premises for originating voice band signals includes a telephone set.

21. The apparatus according to claim 19 wherein the means for originating voice band signals includes a computer and a voice band modem for modulating digital signals from the computer into the voice band.

22. The apparatus according to claim 19 wherein the communications channel comprises the first wire pair.

23. The apparatus according to claim 22 wherein the means at the customer premises for injecting voice band signals onto communications channel comprises a first filter.

24. The apparatus according to claim 23 wherein the means at the central office for stripping off voice band signals comprises a second filter.

25. The apparatus according to claim 19 wherein the means at the customer premises for injecting the voice band signals onto the communications channel comprises a first Coder-Decoder.

26. The apparatus according to claim 25 wherein the means at the central office for stripping off the voice band signals comprises a second Coder-Decoder.

27. The apparatus according to claim 19 wherein the communications channel comprises a second wire pair.

28. The apparatus according to claim 27 wherein the means at the customer premises for injecting voice band signals onto communications channel comprises a first filter.

29. The apparatus according to claim 28 wherein the means at the central office for stripping off voice band signals comprises a second filter.

30. The apparatus according to claim 27 wherein the means at the customer premises for injecting the voice band signals onto the communications channel comprises a first Coder-Decoder

31. The apparatus according to claim 30 wherein the means at the central office for stripping off the voice band signals comprises a second Coder-Decoder.

32. The apparatus according to claim 19 wherein the communications channel comprises a radio channel.