Spread spectrum communication system using DECT protocol

• US 20020034171A1
• Filed: 06/14/2001
• Published: 03/21/2002
• Est. Priority Date: 03/03/1997
• Status: Active Grant

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Dixon, Robert C., Smith, Douglas G.
• Granted Patent: US 6,891,816 B2
• Time in Patent Office: Days
• US Class Current: 370/337
• CPC Class Codes: H04B 1/7093 Matched filter type
• CPC Class Codes: H04B 7/2618 using hybrid code-time division multiple access [CDMA-TDMA]

Abstract

A time division multiplexed wireless communication system using the DECT protocol with spread-spectrum modulation. The wireless communication system comprises a spread-spectrum transmitter and receiver. The spread spectrum transmitter transmits using an M-ary spread spectrum transmission technique, sending a predefined chip code (symbol code) for each data symbol. The predefined chip codes used are relatively short, so that spread spectrum synchronization is accomplished within about a single data symbol transmission time, well within the constraints of the DECT timing structure. The spread spectrum signal may be transmitted over a bandwidth of under 20 MHz (e.g., about 5 MHz) covering a plurality of DECT frequency channels, so as to be confined within, or overlapping with, the bandwidth of a DECT system, and so as to minimize interference with other users, if any, of the same frequency spectrum. A spread spectrum transmission in a DECT time slot may overlay one or more narrowband transmissions, or may overlay other spread spectrum transmissions. Code division multiplexing may also be used to allow multiple spread spectrum transmissions to be sent during a single DECT time slot.

Claims

1. A method of communicating comprising the steps of transmitting from a base station, during a DECT base station time slot of a time frame, a first spread spectrum signal to a user station;

receiving said first spread spectrum signal at said user station;

transmitting from said user station, during a DECT mobile station time slot of said time frame, a second spread spectrum signal to said base station; and

receiving said second spread spectrum signal at said base station.

2. The method of claim 1 wherein said DECT base station time slot and said DECT mobile station time slot are in the same DECT time frame.

3. The method of claim 2 wherein said first spread spectrum signal is transmitted during a base station portion of said time frame and wherein said second spread spectrum signal is received in a mobile station portion of said time frame, said method further comprising the steps of

transmitting a first plurality of signals from said base station to a plurality of user stations during said base station portion, one in each of a plurality of base station time slots;

receiving said first plurality of signals at said user stations;

transmitting a second plurality of signals from said user stations to said base station; and

receiving said second plurality of signals during said mobile station portion, one in each of plurality of user time slots.

4. The method of claim 1 wherein said step of transmitting said first spread spectrum signal and said step of transmitting said second spread spectrum signal each comprises the step of transmitting one data symbol for each one of a plurality of spread spectrum symbol codes.

5. The method of claim 1 wherein each of said spread spectrum symbol codes is no more than 32 chips in length.

6. The method of claim 1 further comprising the steps of transmitting, simultaneously with said steps of transmitting said first spread spectrum code, a first narrowband signal to a second user station during said DECT base station time slot, and transmitting, simultaneously with said step of transmitting said second spread spectrum code, a second narrowband signal from said second user station during said DECT user station time slot, said first narrowband signal having a first bandwidth lying within the bandwidth of said first spread spectrum signal, and said second narrowband signal having a second bandwidth lying within the bandwidth of said second spread spectrum signal.

7. The method of claim 1 wherein said first spread spectrum signal and said second spread spectrum signal are each wider than 1.728 Megahertz in bandwidth.

8. A method comprising the steps of

receiving a data stream in a DECT format;

encoding said data stream in a spread spectrum format and generating a spread spectrum signal thereby;

transmitting said spread spectrum signal during a DECT time slot;

receiving said spread spectrum signal;

correlating said received spread spectrum signal to recover said data stream.

9. The method of claim 8

wherein said data stream comprises a plurality of data symbols;

wherein said step of encoding said data stream comprises the step of encoding said data symbols; and

wherein said step of correlating said received spread spectrum signal comprises the step of synchronizing to said received spread spectrum signal after receiving less than two encoded data symbols.

10. The method of claim 8 wherein said step of encoding said data stream comprises the step of selecting one of a plurality of spread spectrum symbol codes for each predefined portion of said data stream.

11. The method of claim 8 further comprising the step of transmitting a narrowband signal during said DECT time slot, said narrowband signal contained within the same bandwidth as said spread spectrum signal.

12. The method of claim 8 wherein said spread spectrum signal has a bandwidth exceeding 1.728 Megahertz.

14. The communication system of claim 13 wherein each of said time frames is about 10 milliseconds in duration, and each of said base station time slots and each of said user station time slots is about 416.7 microseconds in duration.

15. The communication system of claim 13 wherein said base station, in response to spread spectrum transmissions received from said at least one user station, converts data information received from said at least one user station into a DECT format.

16. The communication system of claim 13 wherein said at least one user station, in response to spread spectrum transmissions received from said base station, converts data information received from said base station into a DECT format.

18. The communication system of claim 17 wherein each of said time frames is about 10 milliseconds in duration, and each of said base station time slots and each of said user station time slots is about 416.7 microseconds in duration.

19. The communication system of claim 17 wherein said base station, in response to spread spectrum transmissions received from a first one of said subset of user stations, converts data information received from said one user station into a DECT format.

20. The communication system of claim 17 wherein one of said subset of user stations, in response to spread spectrum transmissions received from said base station, converts data information received from said base station into a DECT format.

13. A communication system comprising:

a series of time frames for communication between a base station and a plurality of user stations, each of said time frames comprising a base station portion and a user station portion;

a plurality of base station time slots in said base station portion, during each of which said base station may transmit a base-to-user signal to one of said user stations; and

a plurality of user station time slots in said user station portion, during each of which one of said user stations may transmit a user-to-base signal to said base station;

wherein at least one of said user station communicates with said base station with spread spectrum transmissions overlaying a narrowband transmission in a time slot used by said at least one user station.

17. A communication system comprising:

a series of time frames for communication between a base station and a plurality of user stations, each of said time frames comprising a base station portion and a user station portion;

a plurality of base station time slots in said base station portion, during each of which said base station may transmit a base-to-user signal to one of said user stations; and

a plurality of user station time slots in said user station portion, during each of which one of said user stations may transmit a user-to-base signal to said base station;

wherein a subset of said plurality of user stations communicate with said base station in a time slot by sending and receiving code division multiplexed transmissions.

21. A communication system comprising:

a base station;

a plurality of frequency channels;

a plurality of user stations communicating with said base station over said frequency channels using time division multiplexing, whereby said base station transmits a packet to each of said user stations in a first portion of a time frame and receives a packet from each of said user stations in a second portion of said time frame, said first portion of said time frame divided into a plurality of base station time slots and said second portion of said time frame divided into a plurality of user station time slots;

means in said base station for spread spectrum transmitting to a first user station 388 data bits in one of said base station time slots;

a first spread spectrum receiver in said first user station;

means in said first user station for spread spectrum transmitting to said base station 388 data bits in one of said user station time slots;

a second spread spectrum receiver in said base station.

22. The communication system of claim 21 wherein each of said base station time slots and each of said user station time slots is about 416.7 microseconds in duration.

23. The communication system of claim 22 wherein said time frame is about 10 milliseconds in duration.

24. The communication system of claim 21 wherein said base station and said first user station each comprise an M-ary spread spectrum transmitter.