Spread spectrum communication system using DECT protocol

• US 6,272,121 B1
• Filed: 03/03/1997
• Issued: 08/07/2001
• Est. Priority Date: 03/03/1997
• Status: Expired due to Term

• Current Assignee: Intel Corporation
• Original Assignee: Omnipoint Corp. (Deutsche Telekom AG)
• Inventors: Dixon, Robert C., Smith, Douglas G.
• Primary Examiner(s): Hsu, Alpus H.
• Application Number:
  US08/811,108
• Time in Patent Office: 1,618 Days
• Field of Search: 370/277, 370/280, 370/294, 370/329, 370/330, 370/335, 370/337, 370/342, 370/347, 370/350, 375/346, 375/347, 375/348, 375/130, 375/140, 375/141, 375/142, 375/145, 375/146, 375/147, 375/149, 375/150, 455/450, 455/451, 455/452, 455/38.1, 455/507, 455/509, 455/517
• US Class Current: 370/342
• 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 includes 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 (Digital European Cordless Telecommuncation System) base station time slot of a DECT time frame, by modulating a base station data stream with a chip stream output of a chin sequence transmitter generator to provide rapid synchronization in compliance with DECT system timing constraints, 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 DECT time frame, by modulating a user station data stream with a chip stream output of a chip sequence transmitter generator to provide rapid synchronization in compliance with DECT system timing constraints, 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 said DECT time frame.

3. The method of claim 2 wherein said first spread spectrum signal is transmitted during a base station portion of said DECT time frame and wherein said second spread spectrum signal is received in a mobile station portion of said DECT 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 a plurality of user station 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 4 wherein each of said spread spectrum symbol codes is no more than 32 chips in lenght.

6. The method of claim 4 further comprising the steps of

transmitting, simultaneously with said steps of transmitting said first spread spectrum symbol 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 symbol 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 bandwidth of said first spread spectrum signal, and said second narrowband signal having a second bandwidth lying within 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 of communicating comprising the steps of

receiving a data stream in a DECT (Digital European Cordless Telecommunication System) format;

encoding said data stream in a spread spectrum format and generating an encoded spread spectrum signal by modulating said data stream with a chip stream output of a chip sequence transmitter generator to provide rapid synchronization in compliance with DECT system timing constraints;

transmitting said encoded spread spectrum signal during a DECT time slot;

receiving said encoded spread spectrum signal; and

correlating said received spread spectrum signal to recover said data stream in a rapid synchronization manner in compliance with DECT system timing constraints.

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 predetermined 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 encoded spread spectrum signal.

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

13. A communication system comprising:

a series of time frames in DECT (Digital European Cordless Telecommunication System) protocol 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, said base station including a chip sequence transmitter generator that produces a chip stream output, and a modulator to modulate a base station data stream with said chip stream output to provide rapid synchronization within DECT system timing constraints; 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, each of said user stations including a chip sequence transmit generator that produces a chip steam output, and a modulator to modulate a user station data stream with said chip stream output to provide rapid synchronization within DECT system timing constraints;

wherein at least one of said user stations 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.

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 said spread spectrum transmissions received from said at least one user station, converts said user-to-base signal 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 said base-to-user signal received from said base station into a DECT format.

17. A communication system comprising:

a series of time frames in DECT (Digital European Cordless Telecommunication System) protocol 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, said base station including a chip sequence transmitter generator that produces a chips stream output, and a modulator to modulate a base station data stream with said chip stream output to provide rapid synchronization within DECT system timing constraints; 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, each of said user stations including a chip sequence transmitter generator that produces a chip stream output, and a modulator to modulate a user station data stream with said chip stream output to provide rapid synchronization within DECT system timing constraints;

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.

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 said code division multiplexed transmissions received from a first one of said subset of user stations, converts said code division multiplexed 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 said code division multiplexed transmissions received from said base station, converts said code division multiplexed data information received from said base station into a DECT format.

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 with DECT (Digital European Cordless Telecommunication System) protocol, whereby said base station transmits a first packet to each of said user stations in a first portion of a time frame and receives a second 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 plurality of base station time slots, by modulating said data bits with a chip stream output produced by chipping means in said base station to produce a base-to-user spread spectrum signal that provides rapid synchronization within DECT system timing constraints;

a first spread spectrum receiver in said first user station, said first spread spectrum receiver having a correlator configured to despread said base-to-user spread spectrum signal for rapid synchronization within DECT system timing constraints;

means in said first user station for spread spectrum transmitting to said base station 388 data bits in one of said use station time slots, by modulating said data bits with a chip stream output produced by chipping means in said first user station to produce a user-to-base spread spectrum signal that provides rapid synchronization manner providing synchronization within DECT system timing constraints; and

a second spread spectrum receiver in said base station, said second spread spectrum receiver having a correlator configured to despread said user-to-base spread spectrum signal for rapid synchronization within DECT system timing constraints.

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 21 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 comprises an M-ary spread spectrum transmitter.

25. A communication system comprising:

a spread spectrum transmitter operably coupled to a first interface, said first interface operably coupled to a Digital European Cordless Telecommunications System (DECT) Medium Access Control (MAC) layer;

a spread spectrum correlator operably coupled to a second interface, said second interface operably coupled to said MAC layer;

wherein said first interface converts a DECT data stream received from said MAC layer, said DECT data stream being formatted in accordance with the DECT time slot and DECT time frame structure, to a binary data stream provided to said spread spectrum transmitter;

said spread spectrum transmitter generating a spread spectrum signal in response to said binary data stream by modulating said binary data stream with a chip stream output of a chip sequence transmitter generator, said spread spectrum transmitter thereby capable of transmitting said spread spectrum signal in a rapid synchronization manner for providing synchronization within DECT system timing constraints;

said spread spectrum correlator capable of receiving and despreading said spread spectrum signal and generating said binary data stream in response thereto, said spread spectrum correlator further configured to correlate and despread said spread spectrum signal in a rapid synchronization manner for providing synchronization within DECT system timing constraints;

wherein said second interface converts said binary data stream received from said spread spectrum correlator to said DECT data stream provided to said MAC layer; and

wherein said first interface and said second interface permits said MAC layer to function independently from said spread spectrum correlator and said spread spectrum transmitter.

26. The system of claim 25 wherein said spread spectrum correlator achieves data synchronization within each of said Digital European Cordless Telecommunications System (DECT) time slots in about 30 microseconds.

27. The system of claim 25 in which said spread spectrum transmitter transmits said spread spectrum signal in one of said Digital European Cordless Telecommunications System (DECT) time slots and having a frequency bandwidth occupying a plurality of DECT frequency channels.

28. The system of claim 27 in which said spread spectrum transmitter transmits said spread spectrum signal occupying a frequency bandwidth of three of said Digital European Cordless Telecommunications System (DECT) frequency channels.

29. The system of claim 25 in which said spread spectrum transmitter transmits said spread spectrum signal in a plurality of said DECT time slots, said spread spectrum signal occupying one of said Digital European Cordless Telecommunications System (DECT) frequency channels.