Digital cordless phone system for improving distance of speech communication using error concealment and method thereof

• US 6,714,912 B2
• Filed: 01/29/2001
• Issued: 03/30/2004
• Est. Priority Date: 01/28/2000
• Status: Expired due to Fees

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Lee, Yoon-yung
• Primary Examiner(s): Dorvil, Richemond
• Assistant Examiner(s): PATEL, KINARI M
• Application Number:
  US09/772,208
• Publication Number:
  US 20010011216A1
• Time in Patent Office: 1,156 Days
• Field of Search: 359/113, 375/219, 714/755, 704/503, 704/500
• US Class Current: 704/500
• CPC Class Codes: G10L 19/005 Correction of errors induced by the transmission channel, if related to the coding algorithm
• CPC Class Codes: H04M 1/72502 with one base station connected to a single line

Abstract

A digital cordless phone system and a communication method for improving the distance of speech communication using error concealment are provided. The digital cordless phone system has a base unit and a remote unit, and each of the base and remote units has a first codec, a data processing unit, a controller, a modem and a switch. The first codec encodes voice data in a first encoding mode, and decodes the data encoded in the first encoding mode in a first decoding mode. The data processing unit having a second codec encodes the voice data in a second encoding mode, adds an error-detection code to encoded data to indicate existence of an error in the encoded data, removes the error-detection code from encoded data received from one of the base unit and the remote unit in the second encoding mode, performs error concealment with respect to the encoded data from which the error-detection code is removed, and provides error concealed data to the second codec to decode the error concealed data in a second decoding mode. The controller generates a selection signal for changing an encoding mode of the digital cordless phone system in response to a signal representing strength of a signal received from the base unit or the remote unit. The modem modulates data output from the first codec or the data processing unit, and demodulates data remotely received from the base unit or the remote unit. The switch connects the first codec or the data processing unit to the modem in response to the selection signal.

Claims

1. A digital cordless phone system having a base unit and a remote unit, wherein each of the base unit and the remote unit comprising:

a first codec for encoding voice data in a first encoding mode and decoding data encoded in the first encoding mode in a first decoding mode;

a data processing unit having a second codec for encoding the voice data in a second encoding mode, the data processing unit for adding an error-detection code to encoded data to indicate existence of an error in the encoded data, removing the error-detection code from encoded data received from one of the base unit and the remote unit, performing error concealment with respect to the encoded data from which the error-detection code is removed, and providing error concealed data to the second codec to decode the error concealed data in a second decoding mode;

a controller for generating a selection signal for changing an encoding mode of the digital cordless phone system in response to a signal representing strength of a signal received from the base unit or the remote unit;

a modem for modulating data output from the first codec or the data processing unit, and demodulating data remotely received from the base unit or the remote unit; and

a switch for connecting the first codec or the data processing unit to the modem in response to the selection signal.

2. The digital cordless phone system of claim 1, wherein the data processing unit comprises:

an error detection encoder for receiving data encoded in the second encoding mode and encoding the data with the error-detection code;

an error detector for determining whether a corresponding voice sample has an error, based on the error-detection code contained in the encoded data with the error-detection code, and outputting the encoded data from which the error-detection code is removed; and

an error concealment unit for performing error concealment with respect to encoded data of a voice sample determined having an error, and outputting error concealed data to the second codec.

3. The digital cordless phone system of claim 1, wherein the first codec encodes the voice data in units of voice samples using adaptive differential pulse code modulation (ADPCM) and generates encoded data having a 24 Kbps transmission rate.

4. The digital cordless phone system of claim 1, wherein the second codec encodes the voice data in units of voice samples using ADPCM and generates encoded data having a 16 Kbps transmission rate.

5. The digital cordless phone system of claim 1, wherein the switch, in response to the selection signal, connects the first codec to the modem if a speech communication distance between the base unit and the remote unit is within a preset distance of speech communication, and connects the data processing unit to the modem if the speech communication distance is beyond the preset distance of speech communication.

6. The digital cordless phone system of claim 1, wherein for input voice data, data encoded in the second encoding mode is represented by a second bit number, which is smaller than a first bit number which is used for representing data encoded in the first encoding mode.

7. The digital cordless phone system of claim 1, wherein each of the base unit and the remote unit further comprises a frequency shift keying (FSK) processor for generating FSK data indicating that the encoding mode is to change into the first encoding mode or the second encoding mode.

8. The digital cordless phone system of claim 1, wherein the base unit and the remote unit are a base set and a handset, respectively, of the digital cordless phone system.

9. A voice communication method between a base unit and a remote unit in a digital cordless phone system, the method comprising the steps of:

(a) determining whether a current speech communication distance between the base unit and the remote unit is beyond a preset distance of speech communication;

(b) if it is determined that the current speech communication distance is within the preset distance of speech communication, encoding voice data in a first encoding mode and decoding receiving data in a first decoding mode corresponding to the first encoding mode to restore the voice data; and

(c) if it is determined in step (a) that the current speech communication distance is beyond the preset distance of speech communication, encoding the voice data in a second encoding mode, adding an error-detection code to encoded data, removing the error-detection code from receiving data, and decoding the receiving data from which the error-detection code is removed in a second decoding mode corresponding to the second encoding mode to restore the voice data.

10. The voice communication method of claim 9, wherein the step (c) further comprises the steps of:

(c1) encoding the voice data to be transmitted using the second encoding mode;

(c2) performing error-detection encoding with respect to data encoded in the step (c1);

(c3) performing error concealment for error-detection encoded data received remotely from the base unit or the remote unit; and

(c4) restoring the voice data, of which error has been concealed in the step (c3), using the second decoding mode.

11. The voice communication method of claim 10, wherein the step (c1) further comprises the steps of:

(c11) performing a communication-temporarily-stop mode between the base unit and the remote unit;

(c12) transmitting predetermined data indicating that an encoding mode of the digital cordless phone system is to change, during the communication-temporarily-stop mode;

(c13) changing the encoding mode from the first encoding mode into the second encoding mode; and

(c14) turning off the communication-temporarily-stop mode, and encoding the voice data using the second encoding mode.

12. The voice communication method of claim 9, further including after the step (c) the step of changing an encoding mode of the digital cordless phone system from the second encoding mode into the first encoding mode, if the current speech communication distance comes into again within the preset distance of speech communication.

13. The voice communication method of claim 9, wherein if the current speech communication distance changes to exceed the preset distance of speech communication or to come into within the preset distance of speech communication, either the base unit or the remote unit that recognizes first the change provides information indicating the change to the other.

14. The voice communication method of claim 9, wherein for voice data, data encoded in the second encoding mode is represented by a second bit number, which is smaller than a first bit number which is used for representing data encoded in the first encoding mode.

15. A program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform method steps for managing a plurality of data points in a multi-dimensional space, the method comprising the steps of:

performing communication in a first codes mode between a base unit and a remote unit of a digital cordless phone system;

detecting if a current communication distance between the base and remote units is beyond a preset communication distance;

generating a first information to change a coding-decoding mode of the digital cordless phone system from the first codec mode to a second codec mode, when the current communication distance is beyond the preset communication distance; and

performing the communication in the second codec mode between the base and remote units upon receiving the first information.

16. The program storage device of claim 15, further including instructions for performing the steps of:

detecting if the current communication distance is within the preset communication distance;

generating a second information to change the coding-decoding mode from the second codec mode to the first codec mode, when the current communication distance is within the preset communication distance; and

performing the communication in the first codec mode between the base and remote units upon receiving the second information.

17. The program storage device of claim 15, wherein the instructions for performing the communication in the second codec mode comprise instructions for performing the steps of:

encoding voice data and adding an error-detection code to generate and remotely transmit encoded data with the error-detection code;

receiving the encoded data remotely transmitted and detecting an error from the encoded data using the error-detection code;

performing error concealment with respect to the encoded data from which the error is detected, to generate error concealed data; and

decoding the error concealed data to restore the voice data.

18. The program storage device of claim 17, wherein the instructions for detecting an error comprise instructions for performing the steps of:

counting a number of a predetermined binary value in the encoded data;

determining if the number counted in the counting step is an odd number;

removing the error-detection code from the encoded data when the number counted is the odd number; and

providing the encoded data from which the error-detection code is removed, to perform the error concealment.