Method and apparatus for synchronizing a transmitter clock of an analog modem to a remote clock

• US 20060045174A1
• Filed: 08/31/2004
• Published: 03/02/2006
• Est. Priority Date: 08/31/2004
• Status: Abandoned Application

• Current Assignee: Silicon Laboratories Incorporated
• Original Assignee: Ittiam Systems Pte Ltd, Silicon Laboratories Incorporated
• Inventors: Pai, Narasimha, Phogat, Vikram
• Application Number:
  US10/930,210
• Publication Number:
  US 20060045174A1
• Time in Patent Office: Days
• US Class Current: 375/222
• CPC Class Codes: H04L 7/0029 interpolation of received data signal
• CPC Class Codes: H04L 7/0091 Transmitter details
• CPC Class Codes: H04M 11/066 Telephone sets adapted for data transmision

Abstract

A method and apparatus for synchronizing a transmitter clock of an analog modem to a codec sampling clock within a central office are provided. The analog modem includes a transmitter, a receiver and a codec. The analog modem also includes a transmitter re-sampler and a receiver re-sampler coupled to the transmitter and the receiver, respectively. Transmitter signals provided to the codec in a transmit path of the analog modem are re-sampled. The sampling rate of the transmitter re-sampler is subsequently derived from a re-sampling period of the receiver re-sampler provided between the receiver and the codec. The transmitter clock of the analog modem is then synchronized with the codec sampling clock in the central office.

Claims

1. A method for synchronizing a clock within an analog modem to a remote clock within a public switched telephone network, wherein said analog modem includes a modem transmitter, a modem receiver and a modem codec, said method comprising:

utilizing a transmitter re-sampler to re-sample a plurality of transmitter signals from said modem transmitter to said modem codec in a transmit path of said analog modem;

deriving a sampling rate for said transmitter re-sampler from a re-sampling period of a receiver re-sampler provided between said modem receiver and said modem codec; and

synchronizing a transmitter clock within said modem transmitter to a sampling clock within a codec in said central office.

2. The method of claim 1, wherein said transmitter re-sampler re-samples said plurality of transmitter signals via interpolation and decimation.

3. The method of claim 1, wherein said method further includes synchronizing a symbol rate of said modem transmitter to a sampling rate of said codec within said central office after said estimated phase offset correction.

4. A computer program product residing on a computer usable medium for synchronizing a clock within an analog modem to a remote clock within a public switched telephone network, wherein said analog modem includes a modem transmitter, a modem receiver and a modem codec, said computer program product comprising:

program code means for utilizing a transmitter re-sampler to re-sample a plurality of transmitter signals from said modem transmitter to said modem codec in a transmit path of said analog modem;

program code means for deriving a sampling rate for said transmitter re-sampler from a re-sampling period of a receiver re-sampler provided between said modem receiver and said modem codec; and

program code means for synchronizing a transmitter clock within said modem transmitter to a sampling clock within a codec in said central office.

5. The computer program product of claim 4, wherein said transmitter re-sampler re-samples said plurality of transmitter signals via interpolation and decimation.

6. The computer program product of claim 4, wherein said computer program product further includes program code means for synchronizing a symbol rate of said modem transmitter to a sampling rate of said codec within said central office after said estimated phase offset correction.

7. An apparatus for synchronizing a clock within an analog modem to a remote clock within a public switched telephone network, wherein said analog modem includes a modem transmitter, a modem receiver and a modem codec, said apparatus comprising:

a transmitter re-sampler for re-sampling a plurality of transmitter signals from said modem transmitter to said modem codec in a transmit path of said analog modem;

means for deriving a sampling rate for said transmitter re-sampler from a re-sampling period of a receiver re-sampler provided between said modem receiver and said modem codec; and

means for synchronizing a transmitter clock within said modem transmitter to a sampling clock within a codec in said central office.

8. The apparatus of claim 7, wherein said transmitter re-sampler re-samples said plurality of transmitter signals via interpolation and decimation.

9. The apparatus of claim 7, wherein said apparatus further includes means for synchronizing a symbol rate of said modem transmitter to a sampling rate of said codec within said central office after said estimated phase offset correction.