CDMA/TDMA spread-spectrum communications system and method

• US 5,410,568 A
• Filed: 11/03/1993
• Issued: 04/25/1995
• Est. Priority Date: 01/13/1992
• Status: Expired due to Term

• Current Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Original Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Inventors: Schilling, Donald L.
• Primary Examiner(s): Cain, David C.
• Application Number:
  US08/145,124
• Time in Patent Office: 538 Days
• Field of Search: 375/1, 380/49, 379/63, 379/61, 370/19, 370/18, 370/95
• US Class Current: 370/342
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 7/2618 using hybrid code-time division multiple access [CDMA-TDMA]
• CPC Class Codes: H04J 13/00 Code division multiplex systems for frequency hopping H04B1/713
• CPC Class Codes: H04L 7/043 Pseudo-noise [PN] codes variable during transmission synchronisation of spread spectrum receivers H04B1/69
• CPC Class Codes: H04L 7/046 using a dotting sequence

Abstract

A spread-spectrum transmitter and receiver using code division multiple access with time division multiple access technology for spread-spectrum communications. At a base station, a spread-spectrum transmitter includes a multiplexer for time multiplexing a synchronization-code signal and a plurality of data signals, which may be encoded as a plurality-encoded data signals, to generate a time-multiplexed signal. A chip-code generator generates a chip-code signal which is modulo added with the time-multiplexed signal by an EXCLUSIVE-OR gate to generate a spread-spectrum-time-multiplexed signal. A transmitter transmits the spread-spectrum-time-multiplexed signal over a communications channel. A spread-spectrum receiver at the base station processes a plurality of spread-spectrum signals, received from a plurality of remote units in as time division sequence of spread-spectrum signals, using a despreader circuit to generate a time-division signal. A demultiplexer demultiplexes the time-division signal as a plurality of data signals or as a plurality of privacy-encoded data signals. A remote unit, which may be a handset, includes a despreader circuit for despreading the spread-spectrum-time-multiplexed signal as a time-multiplexed signal. A synchronization-code matched filter detects the synchronization-code signal embedded in the time-multiplexed signal and thereby generates a timing signal. A controller uses the timing signal to generate a control signal. The control signal controls a transmit-receive switch for switching an antenna between the despreader circuit to the transmitter at the remote unit.

Claims

1. A method for spread-spectrum processing a plurality of data signals on a carrier frequency f_o, comprising the steps of:

generating a plurality of privacy-code signals;

modulo adding each of the respective plurality of privacy-code signals to each of the plurality of data signals to generate a plurality of privacy-encoded data signals, respectively;

generating a synchronization-code signal;

time multiplexing the synchronization-code signal and the plurality of privacy-encoded-data signals, respectively, to generate a time-multiplexed signal;

generating a chip-code signal;

spread-spectrum processing the time-multiplexed signal with the chip-code signal as a spread spectrum-time-multiplexed signal; and

transmitting the spread-spectrum-time-multiplexed signal on the carrier frequency over a communications channel.

2. The method as set forth in claim 1 wherein the step of transmitting includes the steps of:

generating a carrier frequency;

shifting the spread-spectrum-time-multiplexed signal to the carrier frequency;

amplifying the spread-spectrum-time-multiplexed signal at the carrier frequency; and

radiating the amplified spread-spectrum-time-multiplexed signal at the carrier frequency over the communications channel.

3. A method for spread-spectrum processing a plurality of data signals on a carrier frequency, comprising the steps of:

generating a synchronization-code signal;

time multiplexing the synchronization-code signal and the plurality of data signals, respectively, to generate the time-multiplexed signal;

spread-spectrum processing the time-multiplexed signal with a chip-code signal to generate a spread-spectrum-time-multiplexed signal; and

converting the spread-spectrum-time-multiplexed signal to a form suitable for sending over a communications channel.

4. The method as set forth in claim 3 wherein the step of spread-spectrum processing includes the steps of:

generating a chip-code signal; and

spread-spectrum processing the time-multiplexed signal with the chip-code signal as the spread-spectrum-time-multiplexed signal.

5. The method as set forth in claim 3 wherein the step of converting includes the steps of:

generating a carrier frequency;

shifting the spread-spectrum-time-multiplexed signal to the carrier frequency;

amplifying the spread-spectrum-tim-multiplexed signal at the carrier frequency; and

radiating the amplified spread-spectrum-time-multiplexed signal at the carrier frequency over a communications channel.

6. A method for spread-spectrum processing a spread-spectrum-time-division signal, wherein the spread-spectrum-time-division signal includes a plurality of spread-spectrum signals received sequentially in time from a plurality of remote units, comprising the steps of:

despreading the spread-spectrum-time-division signal as a time-division signal;

demultiplexing the time-division signal as a plurality of remote-privacy-encoded-data signals;

generating a synchronization-code signal;

generating a timing signal;

a generating a plurality of remote-privacy-code signals; and

decoding the plurality of remote-privacy-encoded-data signals, respectively, as a plurality of remote-data signals.

7. The spread-spectrum receiver as set forth in claim 6 wherein the steps of despreading includes the steps of:

generating a chip-code signal; and

despreading using the chip-code signal the received spread-spectrum-time-division signal as the time-division signal.

8. A method for spread-spectrum processing a spread-spectrum-time-division signal, wherein the spread-spectrum-time-division signal includes a plurality of spread-spectrum signals received sequentially in time from a plurality of remote units, comprising:

despreading the spread-spectrum-time-division signal as a time-division signal; and

demultiplexing the time-division signal as a plurality of remote-data signals.

9. The method as set forth in claim 8 wherein the steps of despreading includes the steps of:

generating a chip-code signal; and

despreading, using the chip-code signal, the received spread-spectrum-time-division signal as the time-division signal.

10. A method for spread-spectrum processing a spread-spectrum-time-division signal, wherein the spread-spectrum-time-division signal includes a plurality of spread-spectrum signal received sequentially in time from a plurality of remote units, comprising the steps of:

despreading the spread-spectrum-time-division signal as a time-division signal;

demultiplexing the time-division signal as a plurality of remote-privacy-encoded data signals; and

decoding the plurality of remote-privacy-encoded signals as a plurality of remote-data signals, respectively.

11. The method as set forth in claim 10 wherein the steps of despreading includes the steps of:

generating a chip-code signal; and

despreading, using the chip-code signal, the received spread-spectrum-time-division signal as the time-division signal.

12. The method as set forth in claim 11 wherein steps of synchronization includes the steps of:

generating a synchronization code; and

generating, using the synchronization-code signal a timing signal.

13. The method as set forth in claim 10 wherein the step of decoding includes the steps of:

generating, using the timing signal a plurality of privacy-coded signals; and

generating a synchronization code; and

generating, using the timing signal, the synchronization-code signal.

14. The method as set forth in claim 10 wherein the steps of decoding includes the steps of:

generating, using the timing signal, a plurality of privacy-code signals; and

decoding the plurality of privacy-encoded data signals as a plurality of data signals, respectively.

15. A method for receiving a spread-spectrum-time-multiplexed signal, having a synchronization signal and a plurality a privacy-encoded data signals including a first privacy-encoded-data signal, on a first carrier frequency, f₁, and for spread-spectrum transmitting a remote-data signal on a second carrier frequency, f₂, comprising the steps of:

despreading a spread-spectrum-time-multiplexed signal as a time-multiplexed signal;

generating, using a synchronization-code signal embedded in the time-multiplexed signal, a timing signal;

generating, in response to the control signal, a first privacy-code signal;

decoding the first privacy-encoded-data signal as a first data signal;

generating, in response to the control signal, a remote-privacy-code signal;

encoding the remote-data signal with the remote-privacy-code signal as a remote-privacy-encoded-data signal;

generating a second chip-code signal;

spread-spectrum processing the remote-privacy-encoded signal with the second chip-code signal as a spread-spectrum signal; and

transmitting the spread-spectrum signal on the second carrier frequency, f₂.

16. The method as set forth in claim 15 wherein step of despreading includes:

despreading, using the first chip-code signal, the received spread-spectrum-time-multiplexed signal as the time-multiplexed signal; and

filtering the time-multiplexed signal.

17. A method for receiving a spread-spectrum-time-multiplexed signal, having a synchronization-code signal and a plurality of privacy-encoded data signals including a first privacy-encoded data signal, at a first carrier frequency, and for spread-spectrum transmitting a remote-data signal at a second carrier frequency, comprising the steps of:

despreading the spread-spectrum-time-multiplexed signal as a time-multiplexed signal;

detecting in the time-multiplexed signal the synchronization-code signal and generating a timing signal;

decoding, using the timing signal, the first privacy-encoded data signal embedded in the time-multiplexed signal as a first data signal;

encoding, in response to the control signal, the remote-data signal with a remote-privacy-code signal as a remote-privacy-encoded data signal;

spread-spectrum processing the remote-privacy-encoded data signal with a second chip-code signal to generate a spread-spectrum signal; and

converting the spread-spectrum signal to a form suitable for sending over a communications channel.

18. The method as set forth in claim 17 wherein the step of despreading includes the steps of:

generating a first chip-code signal;

despreading, using the first chip-code signal, the received spread-spectrum-time-multiplexed signal as the time-multiplexed signal; and

filtering the time-multiplexed signal.

19. The method as set forth in claim 17 wherein the step of decoding includes the steps of:

storing, in response to the control signal, the first privacy-encoded data signal embedded in the time-multiplexed signal;

generating, in response to the control signal, a privacy-code signal; and

decoding the first privacy-encoded data signal as the first data signal.

20. The method as set forth in claim 17 wherein the step of encoding includes the steps of:

generating, in response to the control signal, the remote-privacy-code signal; and

encoding the remote-data signal with the remote-privacy-code signal as the remote-privacy-encoded data signal.

21. The method as set forth claim 17 wherein steps of spread-spectrum processing includes the steps of:

storing the remote-privacy-encoded data signal;

generating a second chip-code signal; and

spread-spectrum processing the second privacy-encoded signal with the second chip-code signal as a spread-spectrum signal.

22. A method for receiving a spread-spectrum-time-multiplexed signal, having a synchronization-code signal and a plurality of data signals including a first data signal, at a first carrier frequency, and for spread-spectrum transmitting a remote-data signal at a second carrier frequency, comprising the steps of:

despreading the spread-spectrum-time-multiplexed signal as a time-multiplexed signal;

detecting in time-multiplexed signal the synchronization-code signal and generating a control signal;

spread-spectrum processing the remote-data signal with a second chip-code signal as a spread-spectrum signal; and

converting the spread-spectrum signal to a form suitable for sending over a communications channel.

23. The method as set forth in claim 22 wherein said remote-despreader means includes the steps of:

generating a first chip-code signal;

despreading using the first chip-code signal the received spread-spectrum-time-multiplexed signal as the time-multiplexed signal; and

filtering the time-multiplexed signal.

24. The method as set forth in claim 22 wherein the step of spread-spectrum processing includes the steps of:

storing the remote-data signal;

generating a second chip-code signal; and

spread-spectrum processing the remote-data signal with the second chip-code signal to generate a spread-spectrum signal.