Digital cordless telephony with PCM coding

• US 6,343,217 B1
• Filed: 11/12/1998
• Issued: 01/29/2002
• Est. Priority Date: 11/12/1998
• Status: Expired due to Term

• Current Assignee: RPX Corporation
• Original Assignee: Legerity Incorporated (Microsemi Semiconductor Corp.)
• Inventors: Borland, David J.
• Primary Examiner(s): Bost, Dwayne
• Assistant Examiner(s): CRAVER, CHARLES R
• Application Number:
  US09/191,008
• Time in Patent Office: 1,174 Days
• Field of Search: 455/462, 455/422, 455/425, 455/426, 455/463, 455/554, 455/555, 455/553, 455/552, 455/568, 455/569, 370/277, 375/222, 375/240.21, 375/240.22, 375/242-253, 379/93.09, 379/93.01, 379/93-5-
• US Class Current: 455/462
• CPC Class Codes: H04M 1/6041 Portable telephones adapted for handsfree use
• CPC Class Codes: H04M 1/72502 with one base station connected to a single line
• CPC Class Codes: H04M 1/737 Characterised by transmission of electromagnetic waves other than radio waves, e.g. infrared waves

Abstract

A digital cordless telephone system using lossless pulse code modulation (PCM) for encoding an audio signal. By using an efficiently implemented and uncompressed encoding scheme, the system substantially reduces implementation costs and improves the quality of transmission for white signals such as modem signals. A transceiver implementation includes a PCM coder, an RF transmitter, an RF receiver, and a PCM decoder. Also presented is a method for communicating an audio signal from a transmitter unit to a remote receiver unit. The method includes steps of sampling an audio signal into a PCM data stream, modulating the PCM data stream onto a carrier, transmitting the carrier, receiving the carrier, demodulating the PCM data stream from the carrier, and generating a reconstructed audio signal from the PCM data stream.

Claims

1. A communications system comprising:

an interface configured to allow a user to select a PCM quantization scheme, wherein the PCM quantization scheme may be a logarithmic quatization scheme or a linear quantization scheme;

a base unit; and

a portable unit wirelessly coupled to said base unit;

wherein said base unit is configured to receive an incoming telephone signal from a telephone connection, and wherein said base unit is configured to generate an incoming wireless PCM signal in response to the incoming telephone signal;

wherein said portable unit is configured to receive the incoming wireless PCM signal from said base unit and to generate an incoming audio signal in response to the incoming wireless PCM signal;

wherein said portable unit is further configured to receive an outgoing audio signal and to generate an outgoing wireless PCM signal using the user-selected quantization scheme in response to the outgoing audio signal;

wherein said base unit is further configured to receive the outgoing wireless PCM signal, wherein said base unit is configured to generate an outgoing telephone signal in response to the outgoing wireless PCM signal, and wherein said base unit is configured to provide the outgoing telephone signal to the telephone connection.

2. The communications system of claim 1, wherein the incoming and outgoing audio signals comprise voice signals, and wherein the user-selected PCM quantization scheme comprises a logarithmic quantization scheme.

3. The communications system of claim 2, wherein the logarithmic PCM quantization scheme comprises one of a μ

-law quantization scheme, or an A-law quantization scheme.

4. The communications system of claim 1, wherein the incoming and outgoing audio signals comprise modem signals, and wherein the user-selected PCM quantization scheme comprises a linear quantization scheme.

5. The communications system of claim 1, wherein the logarithmic quantization scheme is selectable for use in voice applications and the linear quantization scheme is selectable for data communications.

6. The communications system of claim 1, wherein the incoming and outgoing telephone signals comprise one or more of POTS telephone signals, wireless local loop telephone signals, and digital telephone signals.

7. The communications system of claim 1, wherein the incoming and outgoing telephone signals comprise one or more of DSL, ADSL, HDSL, HDSL2, and T1 telephone signals.

8. The communications system of claim 1, wherein the incoming telephone signal comprises an incoming PCM signal, and wherein the incoming wireless PCM signal comprises a first RF carrier modulated with the incoming PCM signal;

and

wherein the outgoing wireless PCM signal comprises a second RF carrier modulated with an outgoing PCM signal, and wherein the outgoing telephone signal comprises the outgoing PCM signal demodulated from the outgoing wireless PCM signal.

9. The communications system of claim 1, wherein the incoming and outgoing telephone signals comprise digital signals communicated on a computer network.

10. The communications system of claim 1, wherein the telephone connection comprises a wireless link to a wireless local loop central office, wherein said base unit is comprised in a local-area base station, wherein said base unit communicates call for a plurality of users in a local area, and wherein said portable unit communicates telephone calls for a single user of the plurality of users.

11. The communications system of claim 1, wherein the telephone connection comprises a cellular telephone connection.

12. The communications system of claim 1, wherein the telephone connection comprises a cellular telephone connection, wherein said base unit is configured for operation in an automobile, and wherein said portable unit is either a headset unit or a speakerphone.

13. The communications system of claim 1, wherein the incoming and outgoing wireless PCM signals comprise radio signals.

14. The communications system of claim 1, wherein the incoming and outgoing wireless PCM signals comprise IR signals.

15. A method for communicating an audio signal from a transmitter unit to a receiver unit, the method comprising:

receiving input from a user indicating a selected PCM quantization scheme, where in the PCM quantization scheme may be a logarithmic quantization scheme or a linear quantization scheme;

the transmitter unit sampling the audio signal to generate a PCM data stream therefrom, wherein said sampling is performed according to the user-selected PCM quantization scheme;

the transmitter unit modulating the PCM data stream onto a carrier after said sampling;

the transmitter unit transmitting the carrier after said modulating;

the receiver unit receiving the carrier after said transmitting;

the receiver unit demodulating the PCM data stream from the carrier after said receiving; and

the receiver unit generating a reconstructed audio signal from the PCM data stream after said demodulating.

16. The method of claim 15, wherein the incoming and outgoing audio signals comprise voice signals, and wherein the user-selected PCM quantization scheme comprises a logarithmic quantization scheme.

17. The method of claim 16, wherein the logarithmic PCM quantization scheme comprises one of a μ

-law quantization scheme or an A-law quantization scheme.

18. The method of claim 15, wherein the incoming and outgoing audio signals comprise modem signals, and wherein the user-selected PCM quantization scheme comprises a linear quantization scheme.

19. The method of claim 15, wherein the logarithmic quantization scheme is selectable for use in voice applications and the linear quantization scheme is selectable for data communications.

20. The method of claim 15, wherein the incoming and outgoing telephone signals comprise one or more of POTS telephone signals, wireless local loop telephone signals, digital telephone signals, DSL, ADSL, HDSL, HDSL2, and T1 telephone signals.

21. The method of claim 15, wherein the audio signal comprises an analog signal with frequency components substantially in the range of 30 Hz to 20 kHz.

22. The method of claim 15, wherein the audio signal comprises an analog signal with frequency components substantially in the range of 300 Hz to 3 kHz.

23. The method of claim 15, wherein the audio signal comprises a modem signal.

24. The method of claim 15, wherein the carrier comprises an RF carrier.

25. The method of claim 15, wherein the carrier comprises an IR carrier.

26. The method of claim 15, wherein the transmitter unit is comprised in a portable handset and the receiver unit is comprised in a fixed base unit.

27. The method of claim 15, wherein the transmitter unit is comprised in a fixed base unit and the receiver unit is comprised in a portable handset.

28. A communications transceiver comprising:

an interface configured to allow a user to select a PCM quantization scheme, wherein the PCM quantization scheme may be a logarithmic quantization scheme or a linear quantization scheme;

a PCM coder configured to receive a transmit audio signal and to sample the transmit audio signal using the user-selected PCM quantization scheme to generate a PCM data stream therefrom;

an RF transmitter coupled to said PCM coder and operable to receive the transmit audio signal therefrom;

wherein said RF transmitter is configured to modulate an RF carrier with the PCM data stream to generate an RF transmit signal, and wherein said RF transmitter is configured to transmit the RF transmit signal;

an RF receiver operable to receive an RF received signal, wherein said RF receiver is operable to demodulate a received PCM data stream from the RF received signal; and

a PCM decoder coupled to said RF receiver, wherein said PCM decoder is operable to receive the received PCM data stream and to generate a received audio signal therefrom.

29. The communications transceiver of claim 28, wherein the transmit and received audio signals comprise voice signals, and wherein the user-selected PCM quantization scheme comprises a logarithmic quantization scheme.

30. The communications transceiver of claim 29, wherein the logarithmic PCM quantization scheme comprises one of a μ

-law quantization scheme or an A-law quantization scheme.

31. The communications transceiver of claim 28, wherein the transmit and received audio signals comprise modem signals, and wherein the user-selected PCM quantization scheme comprises a linear quantization scheme.

32. The communications transceiver of claim 28, wherein the logarithmic quantization scheme is selectable for use in voice applications and the linear quantization scheme is selectable for data communications.

33. The communications transceiver of claim 28, wherein the audio signal comprises a modem signal.

34. The communications transceiver of claim 28, wherein said PCM coder, said RF transmitter, said RF receiver, and said PCM decoder are comprised in portable handset.

35. The communications transceiver of claim 28, further comprising:

a microphone coupled to said PCM coder and operable to generate the transmit audio signal from an acoustic source; and

a speaker coupled to said PCM decoder and operable to produce an acoustic output in response to the received audio signal.

36. The communications transceiver of claim 28, further comprising:

a modem port coupled to said PCM coder and to said PCM decoder and configured to couple to a modem, wherein said modem port is operable to receive the transmit audio signal from the modem, and wherein said modem port is operable to provide the received audio signal to the modem.

37. The communications transceiver of claim 28, further comprising:

a microphone operable to generate the transmit audio signal from an acoustic source;

a speaker operable to produce an acoustic output in response to the received audio signal;

a modem port configured to couple to a modem, wherein said modem port is operable to receive the transmit audio signal from the modem, and wherein said modem port is operable to provide the received audio signal to the modem; and

a selector switch coupled to said microphone, said speaker, said modem port, said transmitter, and said receiver, wherein said selector switch is operable to couple (i) said microphone to said RF transmitter and said speaker to said RF receiver, or (ii) said modem port to said RF transmitter and said modem port to said RF receiver.

38. The communications transceiver of claim 28, wherein said PCM coder, said RF transmitter, said RF receiver, and said PCM decoder are comprised in a fixed base unit.

39. The communications transceiver of claim 28, further comprising:

a telephone port coupled to said PCM coder and to said PCM decoder, wherein said telephone port is operable to couple to a telephone line, wherein said telephone port is operable to receive the transmit audio signal from a telephone line, and wherein said telephone port is operable to provide the received audio signal to the telephone line.

40. The communications system of claim 39, wherein the transmit audio signal and received audio signal comprise one or more of POTS telephone signals, wireless local loop telephone signals, and digital telephone signals.

41. The communications system of claim 39, wherein the transmit audio signal and received audio signal comprise one or more of DSL, ADSL, HDSL, HDSL2, and T1 telephone signals.

42. The communications system of claim 39, wherein the transmit audio signal and received audio signal comprise digital signals communicated on a computer network.