Preamble structures for single-input, single-output (SISO) and multi-input, multi-output (MIMO) communication systems

• US 7,269,127 B2
• Filed: 10/04/2002
• Issued: 09/11/2007
• Est. Priority Date: 10/04/2001
• Status: Active Grant

• Current Assignee: Intellectual Ventures II LLC (Intellectual Ventures LLC)
• Original Assignee: BAE Systems Information and Electronic Systems Integration Incorporated (BAE Systems Plc)
• Inventors: Mody, Apurva N., Stuber, Gordon L.
• Primary Examiner(s): Pezzlo; John
• Application Number:
  US10/264,546
• Publication Number:
  US 20030072452A1
• Time in Patent Office: 1,803 Days
• Field of Search: 370/430, 370480-482, 370/208, 370/206, 370/330, 370/210, 370/329, 370/512, 370/513, 342/375, 342/383, 375/146, 375/260, 375/355, 375/267, 375/144, 375/148
• US Class Current: 370/210
• CPC Class Codes: H04B 7/0669 using different channel coding between antennas space-time coding H04L1/0618
• CPC Class Codes: H04L 1/06 using space diversity
• CPC Class Codes: H04L 2027/0095 in a preamble or similar structure
• CPC Class Codes: H04L 25/0226 sounding signals per se
• CPC Class Codes: H04L 27/2607 Cyclic extensions
• CPC Class Codes: H04L 27/2613 Structure of the reference signals
• CPC Class Codes: H04L 27/26134 Pilot insertion in the transmitter chain, e.g. pilot overlapping with data, insertion in time or frequency domain
• CPC Class Codes: H04L 5/0023 Time-frequency-space
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver

Abstract

A communication system is provided herein for transmitting frames across a channel. The frames may be transmitted in single-input, single-output (SISO) and/or multi-input, multi-output (MIMO) communication systems. One such frame includes at least one training symbol, each having a cyclic prefix and a training block. The time length N_I of the training block is equal to an integer fraction I of the time length of a data block, i.e., N_I=N/I. Furthermore, the time length G of the cyclic prefix is an integer fraction of the time length N_I. For example, G may be equal to N_I/4 or 25% of N_I. The training symbols provide coarse and fine time synchronization, coarse and fine frequency synchronization, channel estimation, and noise variance estimation.

Claims

1. A transmitter of a communication system, the transmitter comprising:

an encoder having a pilot/training symbol inserter, the pilot/training symbol inserter configured to insert pilot symbols into data blocks and to combine training symbols with the data blocks;

at least one modulator, each modulator having an inverse discrete Fourier transform (TDFT) stage and a cyclic prefix inserter, each modulator outputting a frame structure comprising a preamble structure and a data structure, the preamble structure comprising at least one training symbol and an enhanced training symbol; and

at least one transmit antenna, each transmit antenna corresponding to a respective one or the at least one modulator, each transmit antenna transmitting the frame structure output from the corresponding modulator, wherein the enhanced training symbol is a single symbol.

2. The transmitter of claim 1, wherein the data structure comprises a plurality of data symbols, each data symbol having a data block and a cyclic prefix, the cyclic prefix being inserted by the cyclic prefix inserter, and each of the at least one training symbol comprises a cyclic prefix and a training block the cyclic prefix being inserted by the cyclic prefix inserter, the training block being inserted by the pilot/training symbol inserter.

3. The transmitter of claim 2 wherein the enhanced training symbol comprises a cyclic prefix and a training block, the cyclic prefix being inserted by the cyclic prefix inserter, the training block inserted by the pilot/training symbol inserter.

4. The transmitter of claim 3, wherein each data block has a number of samples N, each training block of the at lease one training symbol has a number of samples N_I, and the training block of the enhanced symbol has a number of samples N_I, whereby N_I=N/I, where I is an integer.

5. The transmitter of claim 3, wherein the training block of the enhanced training symbol is divided into a number of sections having a number of samples N_J such the N_I=N/J, where J is an integer.

6. The transmitter of claim 5, wherein J equals 4.

7. The transmitter of claim 3, wherein the cyclic prefixes have a number of samples such that G=N/I, where I is art integer.

8. The transmitter of claim 1, wherein the enhanced training symbol comprises a cyclic prefix and a training block, the cyclic prefix having a number of samples G, the training block having a number of samples N_I, whereby N_I=N/I, where N is equal to the number of samples of data blocks of the data structure and I is an integer, and whereby G N_I/4.

9. The transmitter of claim 8, wherein the training block is divided into four sections, each section having a number of samples N_I/4.

10. The transmitter of claim 9, wherein the cyclic prefix and each of the four sections comprises the same sequence.

11. The transmitter of claim 10, wherein the cyclic prefix and the first section provide time synchronization and coarse frequency offset estimation, the second and third sections provide channel estimation and noise variance estimation, and the cyclic prefix and first, second, and third sections further provide fine frequency offset estimation.

12. The transmitter of claim 11, wherein the communication system is a single-input, single-output (SISO) communication system.

13. The transmitter of claim 8, wherein the cyclic prefix is divided into first and second sections having a number of samples N_I/8, the training block is divided into third, fourth, fifth, sixth, seventh, and eighth sections, the third, fourth, seventh, and eighth sections having a number of samples N_I/8, the fifth and sixth sections having a number of samples N_I/4.

14. The transmitter of claim 13, wherein the first, second, third, fourth, seventh, and eight sections comprise a first sequence, and the fifth and sixth sections comprise a second sequence.

15. The transmitter of claim 14, wherein the first, second, third, and fourth sections provide time synchronization and coarse frequency offset estimation, the fifth and sixth sections provide channel estimation and noise variance estimation, and the first through sixth sections further provide fine frequency offset estimation.

16. The transmitter of claim 15, wherein the communication system is a single-input, single-output (SISO) communication system.

17. The transmitter of claim 8, wherein the number of modulators and transmit antennas is two, a first training block corresponding to a first transmit antenna being divided into four sections, each section having a number of samples N_I/4, and a second training block corresponding to a second transmit antenna being divided into four sections, each section having a number of samples N_I/4.

18. The transmitter of claim 17, wherein the cyclic prefixes of each transmit antenna and the first and fourth sections of the first and second training blocks comprise a first, sequence, the second and third sections of the first training block comprising a second sequence that is the negative of the complex conjugate of the first sequence, and the second and third sections of the second training block comprising a third sequence that is the complex conjugate of the first sequence.

19. The transmitter of claim 18, wherein the cyclic prefixes and first sections of the first and second training blocks providing time synchronization and coarse frequency offset estimation, the first, second, and third sections of the first and second training blocks providing channel estimation and noise variance estimation, and the cyclic prefixes and first, second, and third sections of the first and second training blocks further providing fine frequency offset estimation.

20. A method of forming a frame structure that is transmitted in a communication system, the method comprising the steps of:

providing data blocks;

providing training blocks;

combining the data blocks and training blocks in a parallel format to provide a parallel combination;

taking an inverse discrete fourier transform (IDFT) of the parallel combination to form IDFT blocks;

inserting the cyclic prefixes between the IDFT blocks to form parallel symbols;

converting the parallel symbols to serial format to form a preamble structure and a data structure, the preamble structure comprising at least one training symbol and an enhanced training symbol;

the data structure comprising a plurality of data symbols;

forming data symbols such that each data symbol comprises a cyclic prefix and a data block, the cyclic prefix having a number of samples G, the data block having a number of samples N; and

forming a preamble structure having an enhanced training symbol, the enhanced training symbol comprising a cyclic prefix and a training block, the cyclic prefix having a number of samples G, the training block having a number of samples N_I such that N_I=N/I, where I is an integer and G=N_I/4.

21. The method of claim 20, wherein the step of taking an IDFT comprises receiving an input to an IDFT stage such that the enhanced training symbol is formed having five sections, each section having the same sequence.

22. The method of claim 20, wherein the step of taking an IDFT comprises receiving an input to an IDFT stage such that the enhanced training symbol is formed having eight sections, each of the first, second, third, fourth, seventh, and eight sections comprising a first sequence, each of the fifth and sixth sections having a second sequence.

23. The method of claim 20, wherein the step of combining further comprises dividing the data blocks and training blocks onto two transmit diversity brances (TDBs), and forming a frame structure further comprises forming two frame structures, each frame structure being formed on a respective TB.

24. The method of claim 23, wherein a first enhanced training symbol on a first TDB is formed having five sections, and a second enhanced training symbol on a second TDB is formed having five sections.

25. The method of claim 24, wherein the first, second, and fifth sections of each of the first and second enhanced training symbols are formed such that each comprises a first sequence, the third and fourth sections of the first enhanced training symbol are formed such that each comprises a second sequence that is the negative of a complex conjugate of the first sequence, and the third and fourth sections of the second enhanced training symbol are formed such that each comprises a third sequence that is the complex conjugate of the first sequence.