A UNIVERSAL DSL MODEM WHICH IS CAPABLE OF SUPPORTING BOTH DSL OVER PSTN AND DSL OVER ISDN SERVICE

The Subject of the Invention This invention is about a universal DSL modem that can support both DSL over PSTN and DSL over ISDN services with a single hardware and the software associated with this ability. It is also capable of automatically identifying and configuring itself for the appropriate DSL variant.

The Objectives of the Invention The objectives of the universal modem and auto-configuration software in this invention

• Allows End-Users to choose and install a modem without needing to understand which phone service (PSTN or ISDN) or which DSL variant is present.

• Increases customer satisfaction from a Service Provider perspective by providing easy and straightforward installation for users with low levels of technical knowledge. • Allows manufacturers to simplify their product portfolio by providing a single modem that covers a wider range of End-User installations.

• Prevents a Service Provider from sending incorrect hardware to End-Users thus reducing service installation time

• Allows End-Users and Service Providers to install a modem without needing to manually modify the modem settings by means of auto-configuration software that automatically identifies DSL variant.

• Allows Service Providers to decrease stock cost by reducing the number of different types of hardware.

Figures and Description of the Components The attached figures are presented to better describe the Universal DSL Modem proposed in this invention. Figure 1 shows the general system block diagram of how the universal modem is used in this invention. Figure 2 shows the detailed block diagram of the universal modem.

Figure 3 shows the Auto-Configuration Software general algorithm. Descriptions are below: Figure 1 DSL System Block Diagram

Figure 2 Universal DSL Modem Block Diagram

Figure3 Universal DSL Modem Auto-Configuration Software Algorithm Block

Diagram

Figure 4 PSTN frequency band and DSL frequency band over PSTN service Figure 5 ISDN frequency band and DSL frequency band over ISDN service

The elements in the figures are numbered uniquely and are listed below:

1. Universal DSL Modem

Ia. Universal DSL Modem Auto-Configuration Software Ib. Universal DSL Modem Permanent Memory

2. HPF High Pass Filter (End-User side)

3. LPF Low Pass Filter (End-User side)

4. Phone Line Terminating Equipment (TE)

5. End-User Personal Computer (PC) or similar equipment

6. Telephone line carrying DSL over PSTN service or DSL over ISDN service from a Service Provider. Metallic twisted-pair

7. Digital Subscriber Line Access Multiplexer (DSLAM)

8. HPF High Pass Filter (CO side)

9. LPF Low Pass Filter (CO side)

10. PSTN or ISDN Switch 11. DSL Line Interface

12. Digital Signal Processor (DSP)

13. Start of Auto-Configuration Software Algorithm

14. Decision of: Does a Pre-known algorithm and telephony service exist

15. Try pre-detected algorithm to connect to DSLAM 16. Decision of: Is the DSLAM connected

17. Decision of: Are all supported DSL algorithms for DSL-PSTN tried

18. Try other supported algorithms to connect to DSLAM for DSL-PSTN

19. Decision of: Are all supported DSL algorithms for DSL-ISDN tried

20. Decision of: Is the DSLAM connected 21. Try next supported algorithm to connect to DSLAM for DSL-ISDN

22. Check if DSLAM connected

23. Save the detected DSL algorithm and DSL Service

24. End of Auto-Configuration Software Algorithm

25. PSTN service frequency band 26. DSL frequency band over PSTN service

27. ISDN service frequency band

28. DSL frequency band over ISDN service

Prior Art

PSTN (Public Switched Telephone Network) service is an analog phone service also commonly known as POTS (Plain Old Telephone Service). The most typical feature is ordinary telephone communications. Other typical uses of this service are fax machines, analog data modems (example: a data modem which complies with the ITU V.32 or V.90 data communication standards), and other similar devices. The frequency band of PSTN service (25) spans from 0 to 4 kHz on the line.

ISDN BRA (Integrated Services Digital Network Basic Rate Access) service is a pure digital communication service. ISDN BRA can support both phone communications and data communications as an integral part of its service. An ISDN BRA compliant phone or Terminating Equipment is required. The frequency band of ISDN BRA service (27) spans from 0 to 80 kHz on the line.

DSL is a technology that provides broadband Internet access to End-Users over the phone line. DSL service and Telephone service runs on the same phone line simultaneously. Internet access for End-Users with a Digital Subscriber Line (DSL) is provided by a DSLAM (Digital

Subscriber Line Access Multiplexer) (7) that resides on Central Office and provides

broadband internet service over telephone lines and a DSL modem at end user's site. The DSL signals from the DSLAM (7) are merged with the phone service signals (either PSTN or ISDN) at the Telephone Company's Central Office (CO) Switch (10) and DSL signals from the DSL modem are merged with phone service signals at the end user's site. The DSL signals and the phone service signals share the frequency spectrum of a common metallic line (6) from the CO to the End-User. The phone service occupies frequencies at the bottom of the spectrum while the DSL signals occupy frequency spectrum above the phone service. The High Pass Filter (HPF) (8) on the CO and end user side passes only the higher frequency DSL signals and blocks the lower frequency phone service signals. The Low Pass Filter (LPF) (9) on the CO-side and the end user side passes only the lower frequency phone service signals and blocks the higher frequency DSL signals. These are used to isolate and protect the two services from each other at the sources and permit them to coexist on the common line (6). Phone Line Terminating Equipment (TE) (4), depends on the type of phone service. For PSTN phone service, the TE (4) could be a single phone, fax machine, or other device which connects to a regular phone line. There could also be phone distribution wiring, such as in a residence or office, between the LPF (3) and the TE (4). For ISDN BRA phone service, the TE (4) could be a single ISDN compliant device, or an ISDN compliant device which can provide another ISDN BRA interface that can support multiple additional local ISDN TEs.

Many DSL variants specify how the DSL service coexists with a phone service on the same wire. The DSL frequency band specified for optimal coexistence with PSTN service (i.e. the lowest DSL frequency is located as close as possible to the highest PSTN frequency) will be referred to in this document as the DSL over PSTN service frequency band (26) (Example: In ITU-T recommendation G.992.5 Annex A, ADSL2+ over POTS, the beginning of the DSL frequency band starts at 25 kHz).

The DSL frequency band specified for optimal coexistence with ISDN BRA service (i.e. the lowest DSL frequency is located as close as possible to the highest ISDN BRA frequency) will be referred to in this document as the DSL over ISDN service frequency band (28) (Example: In ITU-T recommendation G.992.5 Annex B, ADSL2+ over ISDN, the beginning of the DSL frequency band starts at 120 kHz).The upper end of the DSL-PSTN/ISDN frequency bands is DSL variant dependent.

Prior art requires to use two separate types of DSL modems with different hardware design that can generate and receive DSL signals at two different frequency bands depending on the telephone network type (PSTN or ISDN). The DSL Line Interface (11) found in any DSL Modem has multiple purposes. Some of those are providing proper impedance matching for the DSL line, line surge immunity, and isolation. It also provides the function of a supplementary HPF for DSL signals. In current modem designs, the frequency pass band of the supplementary HPF function in the DSL Line Interface (11) is set to match the HPF(2) at end user side. This leads to different modem implementations for different DSL frequency bands. (Example: A typical DSL modem intended to support DSL over ISDN service implements a DSL Line Interface (11) with the supplementary HPF function specifically designed for the DSL over ISDN service frequency band (27). If a normal DSL modem is required to support DSL over PSTN service, the high pass filter on its line interface needs to be designed per DSL over PSTN service frequency band (25).

The signals that come from DSL Line Interface (11) are delivered to Digital Signal Processor (DSP) (12) in order to be processed. Separately the data that needs to be sent to internet are converted into DSL signals by DSP(12) and sent to the line (6). The behavior of DSP software changes depending on which DSL variant is being (DSL over PSTN (26) or ISDN(28)). For each DSL variant, different DSP software usually loaded to DSL modems depending on telephone service type is PSTN or ISDN.

In the known previous methods, modems are specifically built for a particular DSL variant and phone service. Such methods require the End-User to know the specific details of their phone service and DSL variant and increases the required number of modem models.

Detailed Description of the Invention

This invention is about a universal DSL modem that can support both DSL over PSTN and DSL over ISDN services with a single hardware and the software associated with this ability. The Universal DSL Modem has an DSL Line Interface (11) which supports both DSL over PSTN and DSL over ISDN service frequency band (26, 28). The Universal DSL Modem is connected to the telephone line (6) with an End-User HPF (2) which is appropriate for the DSL service present (DSL over PSTN or DSL over ISDN). The Phone Line Terminating Equipment(4) is connected to the telephone line (6) with an End-User LPF (3) which is appropriate for the phone service present (PSTN (25) or ISDN (26) ). Software, which runs in the modem, automatically detects the DSL service and executes the algorithm in the DSP (12) that supports the appropriate DSL type. By means of these hardware and software features, the Universal Modem in this invention is capable of supporting both DSL over PSTN service and DSL over ISDN service using the same hardware.

To support the DSL over PSTN service (6), the Universal DSL Modem (1) is combined with an End-User HPF (2) whose pass band supports the DSL-PSTN frequency band (26), and an LPF (3) whose pass band supports the PSTN frequency band (25). The DSL line interface (11) in the Universal Modem has a high pass filter feature. The high pass filter feature on DSL line interface (11) only blocks PSTN phone service signals (25) which are below DSL over PSTN service frequency band (26).

To support the DSL over ISDN service, the Universal DSL Modem (1) is combined with an End-User LPF (3) whose pass band supports the ISDN frequency band (27) and an End-User HPF (2) whose pass band supports the DSL over ISDN service frequency band (28). The high pass filter in the DSL Line Interface (11) of the Universal DSL Modem (1) only blocks the phone service signals which are below the DSL over PSTN service frequency band (26), instead of starting just below the DSL-ISDN frequency band (28). Externally connected End- User HPF (2) prevents signals from the ISDN frequency band (27) below DSL over ISDN service frequency band (28) from reaching the Universal Modem (1), that way provides necessary high pass filtering requirements of DSL Line Interface (11) in End-User HPF (2) instead of DSL modem.

In some applications DSL over PSTN service and DSL over ISDN service uses the same frequency. When using the Universal DSL Modem with this service variation, End-User HPF (2) which only supports the DSL over ISDN service frequency band (28) is used. The End- User LPF (3) would support the ISDN frequency band (27).

The Universal DSL Modem Auto Configuration Software (Ia) runs on the Universal Modem (1) and automatically detects which DSL service is present. DSL Digital Signal Processor (DSP) (12), executes the algorithm which supports the detected DSL service type (DSL over PSTN service (26) or DSL over ISDN service (28)). So that the Universal DSL Modem can support both DSL over PSTN and DSL over ISDN services with a single hardware.

.After The Auto Configuration Software Algorithm (Ia) detected the DSL frequency band and DSL variant that is being connected the first time, the Auto Configuration Software saves this information in the Universal Modem Permanent Memory (Ib) and uses it as the pre- detected configuration in later trials. If connecting to the DSLAM (7) fails using the pre- detected configuration, then the algorithm finds the DSL frequency band and the DSL variant once more from scratch. The Auto Configuration Software Algorithm (Ia) starts (13) and first checks whether the DSL variant and its frequency band were pre-detected or not (14). If there is a pre-detected configuration, the Auto Configuration Software first executes the appropriate algorithm for the pre-detected DSL type on the DSP (12). The Auto Configuration Software then tries connecting to DSLAM (7) for a while (15). At the end of this period, the connection to the DSLAM (7) is checked (16). If the connection is established, the Auto Configuration Software Algorithm (Ia) finishes (24) searching for appropriate DSL Digital Signal Processing algorithm operation and DSL Digital Signal Processor (12) continues to run the algorithm loaded until the DSL connection is lost. If the connection with the DSLAM (7) is not established, the Auto Configuration Software (Ia) goes on to try all supported DSL variants for DSL over PSTN service frequency band (26) and DSL over ISDN service frequency band (28) (17). First, it tries to connect to DSLAM (7) for a period of time (18) using all supported DSL variants for the DSL over PSTN service frequency band (26). After each attempt, the connection to the DSLAM (7) is checked (20). If the connection is established, the Auto Configuration Software (Ia) identifies the detected DSL variant and the DSL-PSTN frequency band (26) as the configuration of choice and saves this information in the Universal Modem Permanent Memory (Ib) as the pre-detected configuration (23) and finishes (24). DSL Digital Signal Processor (12) continues to run the algorithm loaded until the DSL connection is lost. If all of the DSL variants for the DSL-PSTN frequency band (26) are tried and none of them works (17), the Auto Configuration Software (Ia) then tries all supported DSL variants for the DSL over ISDN service frequency band (28). It tries to connect to the DSLAM (7) for a period of time using each supported DSL variant for the DSL over ISDN service frequency band (21). After each attempt, it checks the DSLAM connection (22). If the connection is established, the Auto Configuration Software identifies the detected DSL variant and the DSL over ISDN service frequency band as the configuration of choice and saves this information in the Universal Modem Permanent Memory (Ib) to be used as the pre-detected configuration (23) then finishes (24). DSL Digital Signal Processor (12) continues to run the algorithm loaded until the DSL connection is lost.

A different way of using the Universal DSL Modem Auto Configuration Software (Ia), is where the End-User selects the DSL service and manually saves it in the Universal DSL Modem Permanent Memory (Ib) as the configuration of choice. When starting, the Universal DSL Auto Configuration Software (Ia) executes the DSL algorithm in the DSP (12) which is appropriate for the saved DSL service.