Pcm modem over all-digital connection

• US 20040047407A1
• Filed: 10/20/2003
• Published: 03/11/2004
• Est. Priority Date: 03/29/2000
• Status: Abandoned Application

• Current Assignee: Surf Communications Solutions
• Original Assignee: Surf Communications Solutions
• Inventors: Kasher, Assaf, Fisher, Abraham, Somekh, Oren
• Application Number:
  US10/416,973
• Publication Number:
  US 20040047407A1
• Time in Patent Office: Days
• US Class Current: 375/222
• CPC Class Codes: H04L 25/4927 using levels matched to the quantisation levels of the channel
• CPC Class Codes: H04L 5/1438 Negotiation of transmission parameters prior to communication modified according to link quality H04L1/0001
• CPC Class Codes: H04M 11/06 Simultaneous speech and data transmission, e.g. telegraphic transmission over the same conductors
• CPC Class Codes: H04M 11/066 Telephone sets adapted for data transmision

Abstract

A method of transmitting data. The method includes establishing a modem connection (72) between two digitally connected modems (24, 28) and transmitting data on the modem connection (82) in accordance with a transmission scheme defined only for transmission from analog to digital modems.

Claims

1. A method of transmitting data, comprising:

establishing a modem connection between two digitally connected modems; and

transmitting data on the modem connection in accordance with a transmission scheme defined only for transmission from analog to digital modems.

2. A method according to claim 1, wherein transmitting the data comprises transmitting in accordance with the upstream transmission scheme of the V.92 protocol.

3. A method according to claim 1 or claim 2, wherein the transmission scheme defined only for transmission from analog to digital modems is defined for use concurrently on a same line with an opposite direction transmission scheme which has a higher maximal transmission rate.

4. A digitally connected modem, comprising:

a digital line interface adapted to transmit symbols at a predetermined rate defining respective symbol periods; and

a signal generation unit adapted to generate, during a training phase of a modem connection, symbols of a pair of instances of a training signal, shifted relative to each other by a phase shift of a fractional symbol period, for transmission by the line interface.

5. A modem according to claim 4, wherein the training signal comprises a signal defined by the V.92 protocol.

6. A modem according to claim 4 or claim 5, wherein the phase shift comprises a shift of half the symbol period.

7. A modem according to any of claims 4-6, wherein the signal generation unit comprises an interpolator adapted to convert a generated training signal into a series of samples with a sampling rate higher than that of the signals transmitted by the digital line interface and a decimator adapted to down-sample the training signal to the sampling rate of the signals transmitted by the digital line interface, with a phase shift, when a phase shift is required.

8. A modem according to any of claims 4-7, wherein the signal generation unit comprises a memory which stores segments of the training signal with and without the phase shift and the generation of the signals is performed with reference to the segments stored in the memory.

9. A modem according to any of claims 4-7, wherein the signal generation unit comprises a memory which stores a sample series representing both the instances of the training signal together with at least one signal transmitted between the instances.

10. A modem according to any of claims 4-7, wherein the signal generation unit comprises a memory which stores a table which includes all the sample values of the training signal with different phase shift values.

11. A modem according to any of claims 4-10, wherein the different instances of the training signal have different lengths.

12. A modem according to any of claims 4-11, wherein the different instances of the training signal are shifted relative to each other by a shift period including a non-integer number of symbol periods, the phase shift being equal to a fractional portion of the shift period.

13. A method of transmitting modem training signals, comprising:

transmitting, from a first modem to a second modem, a message including a value of at least one parameter of a training signal expected to be received by the first modem; and

transmitting, by the second modem, the training signal expected to be received by the first modem, with a predetermined value of the at least one parameter, which is independent of the value of the at least one parameter in the message.

14. A method according to claim 13, wherein transmitting the message comprises transmitting a J_p message of the V.92 protocol.

15. A method according to claim 13 or claim 14, wherein the at least one parameter is related to a length of the training signal.

16. A method according to any of claims 13-15, wherein the second modem comprises a digital modem.

17. A method of establishing a modem connection, comprising:

establishing a physical connection between a pair of digital modems;

selecting a protocol which requires that at least one of the modems of the connection is a digital modem, to govern the transmission on the physical connection; and

transmitting, on the established connection, at least one signal defined for evaluating analog effects of the physical connection.

18. A method according to claim 17, wherein selecting a protocol comprises selecting a protocol which uses different provisions for upstream and downstream transmission.

19. A method according to claim 17 or claim 18, wherein transmitting at least one signal defined for evaluating analog effects comprises transmitting a signal for evaluating a phase shift caused by the physical connection.

20. A method according to any of claims 17-19, wherein transmitting at least one signal defined for evaluating analog effects comprises transmitting a signal for determining a required echo cancellation.

21. A method according to any of claims 17-20, wherein transmitting at least one signal defined for evaluating analog effects comprises transmitting a signal for channel equalizer training.

22. A modem, comprising:

a line interface adapted to receive signals transmitted in a downstream of a modem connection in accordance with a modem protocol which has different provisions for the upstream and the downstream; and

a digital interpretation unit adapted to receive samples from the line interface, after passing through fewer than all of an echo canceller, an automatic gain controller, a rate converter, a time recovery unit, an equalization unit and a channel filter.

23. A modem according to claim 22, wherein the line interface is adapted to receive signals transmitted in a downstream of a modem connection in accordance with the ITU V.90 or V.92 protocol.

24. A modem according to claim 22 or claim 23, wherein the digital interpretation unit is connected directly to the line interface.

25. A modem according to any of claims 22-24, wherein the digital interpretation unit comprises a symbol decision module adapted to receive samples directly from the line interface.

26. A modem according to any of claims 22-25, wherein the line interface is adapted to receive symbols at a rate of 8000 symbols per second.

27. A method according to any of claims 22-26, wherein the line interface is connected to a digital trunk line.

28. A method according to any of claims 22-27, wherein the digital interpretation unit is adapted to receive samples from the line interface, without the samples passing through any unit for overcoming analog signal effects.

29. A modem, comprising:

a line interface adapted to transmit signals in accordance with an upstream of a modem protocol which has different provisions for the upstream and the downstream, on a communication line; and

a digital transmission unit adapted to transmit samples through the line interface, without passing the samples through both a precoder filter and a prefilter.

30. A modem according to claim 29, wherein the digital transmission unit is adapted to transmit samples without passing through a precoder filter or a prefilter.

31. A modem according to claim 29 or claim 30, wherein the line interface is adapted to transmit signals in accordance with the upstream of the V.92 modem protocol.

32. A modem according to any of claims 29-31, wherein the digital transmission unit comprises a constellation point selector which is connected to the line interface without intervening filters.

33. A modem according to any of claims 29-32, wherein the digital transmission unit performs calculations using 16 bit linear level samples and the modem comprises a converter, which converts 16 bit linear level samples into PCM samples.

34. A modem according to any of claims 29-33, wherein the line interface is adapted to transmit signals onto a digital trunk.

35. A method of forming a modem connection, comprising:

establishing a physical connection between a first and a second modem; and

transmitting a message including data on the capabilities of the first modem, from the first modem to the second modem, the message purposely identifying the first modem as being of a different type, having a different capability or being connected differently than the first modem is actually connected.

36. A method according to claim 35, wherein the first modem is digitally connected and the message identifies the first modem as being analog connected.

37. A method according to claim 36, wherein the message identifies the first modem as supporting an all digital protocol.

38. A method according to claim 36, wherein the message does not identify the first modem as supporting an all digital protocol.

39. A method according to any of claims 35-38, wherein the second modem is digitally connected.

40. A method according to any of claims 35-39, wherein the message identifies the first modem as supporting at least one protocol which differentiates between analog connected and digital connected modems.

41. A method according to claim 40, wherein the message identifies the first modem as supporting at least one of the V.90 and V.92 protocols.

42. A method according to any of claims 35-41, comprising receiving a user instruction on whether to identify as an analog or digital connected modem and wherein the message identifies the connection of the modem responsive to the user indication.

43. A method according to any of claims 35-42, comprising determining whether to identify as analog or digital connected responsive to a telephone number of the second modem and wherein the message identifies the connection of the modem responsive to the determination.

44. A method according to any of claims 3543, wherein the message is transmitted during a protocol negotiation procedure.

45. A method according to claim 44, wherein the first modem does not perform, during the protocol negotiation procedure, at least one test required to determine analog connection parameters.

46. A method according to claim 44, wherein the first modem disregards results of at least one test required to determine analog connection parameters.