APPARATUS AND METHOD FOR ESTIMATING CHANNEL IN MIMO SYSTEM BASED OFDM/OFDMA

• US 20100085866A1
• Filed: 12/31/2007
• Published: 04/08/2010
• Est. Priority Date: 12/31/2006
• Status: Active Grant

• Current Assignee: Wireless Alliance, LLC (Intellectual Discovery Co., Ltd.)
• Original Assignee: POSDATA Co., Ltd (Posco)
• Inventors: Li, Zheng Zi, Kim, Byung-Chul
• Granted Patent: US 8,644,363 B2
• Time in Patent Office: Days
• US Class Current: 370/208
• CPC Class Codes: H04L 2025/03426 transmission using multiple-input and multiple-output channels
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 25/0224 using sounding signals
• CPC Class Codes: H04L 27/2657 Carrier synchronisation
• CPC Class Codes: H04L 27/2662 Symbol synchronisation
• CPC Class Codes: H04L 27/2675 Pilot or known symbols

Abstract

The present invention relates to an apparatus and method for estimating a channel in a MIMO wireless telecommunication system supporting the 0FDM/0FDMA. The present invention, in estimating a channel by using two or more pilots included in at least one received signal among received signals of a first channel and a second channel received through a first receiving antenna and received signals of a third channel and a fourth channel received through a second receiving antenna, determines a subchannel mapping rule respectively for the received signals of the first channel to the fourth channel, and estimates a channel with a different method according to the determined subchannel mapping rule. That is, the channel is estimated by using two or more pilots included in two or more tiles corresponding to the same subcarrier respectively, in case a subchannel rotation does not exist in the subchannel mapping rule, while the channel is estimated by using two pilots included in an individual tile, in case a subchannel rotation exists in the subchannel mapping rule.

Claims

1. An apparatus for estimating a channel in a MIMO wireless telecommunication system supporting an OFDM or OFDMA, the apparatus comprising:

FFT means for transforming signals of a first channel and a second channel received through a first receiving antenna and signals of a third channel and a fourth channel received through a second receiving antenna, from a time domain to a frequency domain;

carrier frequency offset processing means for estimating a carrier frequency offset for a corresponding received signal by using two or more pilots included in at least one received signal among received signals of the first channel to the fourth channel, which are transformed into the frequency domain;

time offset processing means for estimating a time offset for a corresponding received signal by using two or more pilots included in at least one received signal among received signals of the first channel to the fourth channel, which are transmitted from the carrier frequency offset processing means or the FFT means; and

channel estimating means for estimating a channel of each received signal of the first channel to the fourth channel with a different method according to a subchannel mapping rule by using pilots included in each received signal, which is transmitted from the time offset processing means.

2. The apparatus of claim 1, further comprising a subchannel mapping rule determining means for determining the subchannel mapping rule and selectively transmitting the received signal of the first channel to the fourth channel, which is outputted from the FFT means, to the carrier frequency offset processing means or the time offset processing means according to the subchannel mapping rule.

3. The apparatus of claim 1, wherein the channel estimating means estimates a channel by using two or more pilots included in two or more tiles corresponding to the same subcarrier respectively, in case a subchannel rotation does not exist in the subchannel mapping rule, while the channel estimating means estimates a channel by using two pilots included in an individual tile, in case a subchannel rotation exists in the subchannel mapping rule.

4. The apparatus of claim 3, wherein the channel estimating means estimates each channel by performing the averaging or the interpolation of pilots included in each received signal which is received through the receiving antenna.

5. The apparatus of claim 4, wherein the channel estimating means interpolates the pilots by using an index difference or a distance difference for the pilots, in case of estimating a channel by interpolating the pilots.

6. The apparatus of claim 1, wherein the carrier frequency offset processing means includes a carrier frequency offset estimating means comprising:

a first phase difference operator for calculating a phase difference according to a carrier frequency offset for two or more pilots having the same subcarrier index;

a first phase difference accumulator for accumulating a phase difference according to the calculated carrier frequency offset;

a first linear phase operator for calculating a linear phase according to a carrier frequency offset by using a phase difference according to the accumulated carrier frequency offset; and

a carrier frequency offset operator for calculating a carrier frequency offset based on the linear phase according to the carrier frequency offset.

7. The apparatus of claim 1, wherein the carrier frequency offset processing means estimates a carrier frequency offset by using a pair of pilots in which the symbol index difference is a multiple of 3 while the pilot pair has the same subcarrier index.

8. The apparatus of claim 1, wherein the carrier frequency offset processing means estimates the carrier frequency offset by using two pairs of pilots having the same subcarrier index difference.

9. The apparatus of claim 1, wherein the time offset processing means includes a time offset estimating means comprising:

a second phase difference operator for calculating a phase difference according to a time offset for two or more pilots;

a second phase difference accumulator for accumulating a phase difference according to the calculated time offset;

a second linear phase operator for calculating a linear phase according to a time offset by using a phase difference according to the accumulated time offset; and

a time offset operator for calculating the time offset based on the linear phase according to the time offset.

10. The apparatus of claim 1, wherein the time offset processing means estimates the time offset for the received signal transmitted from the carrier frequency offset processing means, by using a pilot pair in which the carrier frequency offset is compensated while the pilot pair has a different subcarrier index.

11. The apparatus of claim 1, wherein the time offset processing means estimates the time offset for the received signal transmitted from the FFT means, by using two pilots included in an individual tile.

12. The apparatus of claim 1, wherein the received signals of the first and the third channel and the received signals of the second and the fourth channel are transmitted from different terminals.

13. The apparatus of claim 1, wherein the channel estimating apparatus supports at least one among IEEE 802.16d/e, Wibro, and WiMAX standard.

14. A method for estimating a channel in a MIMO wireless telecommunication system supporting an OFDM or OFDMA, the method comprising the steps of:

a) receiving signals of a first channel and a second channel through a first receiving antenna, and signals of a third channel and a fourth channel through a second receiving antenna;

b) determining a subchannel mapping rule for the received signal of the first channel to the fourth channel; and

c) estimating the first channel to the fourth channel respectively with a different mode according to the determined subchannel mapping rule.

15. The method of claim 14, wherein the step c) includes the step of:

c-1) estimating a channel by using two or more pilots included in two or more tiles corresponding to the same subcarrier, for the received signal having no subchannel rotation in the subchannel mapping rule among the received signals of the first channel to the fourth channel.

16. The method of claim 15, after the step b), further comprising the step of:

b′

) estimating and compensating a carrier frequency offset and a time offset by using two or more pilots included in the received signal having no subchannel rotation in the subchannel mapping rule among the received signals of the first channel to the fourth channel.

17. The method of claim 14, wherein the step c) includes the step of:

c-2) estimating a channel by using two pilots included in an individual tile, for the received signal having the subchannel rotation in the subchannel mapping rule among the received signals of the first channel to the fourth channel.

18. The method of claim 17, after the step b), further comprising the step of:

b′

) estimating and compensating a time offset by using two or more pilots included in the received signal having the subchannel rotation in the subchannel mapping rule among the received signals of the first channel to the fourth channel.

19. The method of claim 14, wherein, in the step c), the estimating a channel is performed through the averaging or the interpolation of pilots included in the received signal of the first channel to the fourth channel respectively.

20. The method of claim 19, wherein in the step c), the estimating a channel through the interpolation of pilots is performed by using an index difference or a distance difference for the pilots.

21. The method of claim 14, wherein the received signals of the first and the third channel and the received signals of the second and the fourth channel are transmitted from different terminals.

22. A method for estimating a channel for an uplink PUSC mode in a MIMO wireless telecommunication system supporting an OFDM or OFDMA, the method comprising the steps of:

a) receiving signals transmitted with a spatial multiplexing through the same subcarrier with different pilot patterns from a first terminal and a second terminal equipped with one transmitting antenna respectively, through a first receiving antenna and a second receiving antenna, wherein the signals have no subchannel rotation;

b) estimating a first carrier frequency offset and a first time offset by using two or more pilots included in at least one received signal among the received signals of a first channel and a third channel transmitted from the first terminal, and estimating a second carrier frequency offset and a second time offset by using two or more pilots included in at least one received signal among the received signals of a second channel and a fourth channel transmitted from the second terminal; and

c) estimating the first channel and the third channel by using two or more pilots which are included in the received signals of the first channel and the third channel respectively and are compensated for the first carrier frequency offset and the first time offset, and estimating the second channel and the fourth channel by using two or more pilots which are included in the received signals of the second channel and the fourth channel respectively are compensated the second carrier frequency offset and the second time offset.

23. A method for estimating a channel for an uplink PUSC mode in a MIMO wireless telecommunication system supporting an OFDM or OFDMA, the method comprising the steps of:

a) receiving signals transmitted with a spatial multiplexing through the same subcarrier with different pilot patterns from a first terminal and a second terminal equipped with one transmitting antenna respectively, through a first receiving antenna and a second receiving antenna, wherein the signals have the subchannel rotation;

b) estimating a first time offset by using two or more pilots included in at least one received signal among the received signals of a first channel and a third channel transmitted from the first terminal, and estimating a second time offset by using two or more pilots included in at least one received signal among the received signals of a second channel and a fourth channel transmitted from the second terminal; and

c) estimating the first channel and the third channel by using two or more pilots which are included in the received signals of the first channel and the third channel respectively and are compensated for the first time offset, and estimating the second channel and the fourth channel by using two or more pilots which are included in the received signals of the second channel and the fourth channel respectively and are compensated for the second time offset.

24. A method for estimating a channel in a MIMO wireless telecommunication system, the method comprising the steps of:

a) receiving signals transmitted with a spatial multiplexing through the same subcarrier with different pilot patterns from a first terminal and a second terminal equipped with one transmitting antenna respectively, through a first receiving antenna and a second receiving antenna, wherein the signals have subchannel mapping rule without subchannel rotation; and

b) estimating a channel for each signal by using pilots respectively included in at least two tiles among tiles which correspond to the same subcarrier and are adjacent to each other in the direction of the OFDMA symbol axis.

25. An apparatus for estimating a channel in a MIMO wireless telecommunication system supporting an OFDM or OFDMA, the apparatus comprising:

FFT means for transforming signals of a first channel and a second channel received through a first receiving antenna and signals of a third channel and a fourth channel received through a second receiving antenna, from a time domain to a frequency domain;

subchannel mapping rule determining means for determining a subchannel mapping rule for the received signal of the first channel to the fourth channel;

time offset processing means for estimating a time offset for a corresponding received signal by using a plurality of tiles or slots adjacent in the direction of the OFDMA symbol axis, for a received signal having no subchannel rotation in the subchannel mapping rule among the received signals of the first channel to the fourth channel, which are transformed into the frequency domain; and

channel estimating means for estimating a channel of each received signal by using pilots respectively included in the corresponding received signal, for the received signals of the first channel to the fourth channel transmitted from the time offset processing means.

26. The apparatus of claim 25, wherein the channel estimating means estimates a channel by using a channel compensation value of a corresponding tile which is obtained by reflecting a calculated channel estimation value of an adjacent tile into a channel estimation value of the corresponding tile after calculating the channel estimation value of each tile adjacent in the direction of the OFDMA symbol axis, for a signal having no subchannel rotation in the subchannel mapping rule.

27. The apparatus of claim 26, wherein the channel compensation value of the corresponding tile is calculated by multiplying the channel estimation value of the corresponding tile and the channel estimation value of a tile which is adjacent to the corresponding tile in the direction of the OFDMA symbol axis by a weight respectively.

28. The apparatus of claim 25, wherein the channel estimating means estimates a channel by using the channel estimation value of the corresponding tile which is calculated by averaging pilots included in each received signal by the tile, for a signal having the subchannel rotation in the subchannel mapping rule.

29. The apparatus of claim 25, wherein the time offset processing means estimates a time offset by using a linear phase compensation value according to the time offset of a corresponding slot region, which is produced by averaging the linear phase according to the time offset for an individual slot by slot region, calculating the linear phase average value according to the time offset by slot region, and reflecting a linear phase average value according to the time offset of the adjacent slot region into the linear phase average value according to the time offset of the corresponding slot region.

30. The apparatus of claim 29, wherein the linear phase compensation value according to the time offset of the corresponding slot region is calculated by multiplying the linear phase average value according to the time offset of the corresponding slot region and the linear phase average value according to the time offset of the adjacent slot region by a weight respectively.

31. The apparatus of claim 25, wherein the time offset processing means includes a time offset estimating means comprising:

a phase difference operator for calculating a phase difference according to a time offset for two or more pilots included in each tile;

a phase difference accumulator for accumulating a phase difference according to the calculated time offset;

a linear phase operator for calculating a linear phase according to a time offset by slot region by using a phase difference according to the accumulated time offset; and

a time offset operator for calculating the time offset based on the linear phase according to the time offset.

32. The apparatus of claim 25, wherein the time offset processing means estimates the time offset by using a tile or a slot corresponding to the same slot region, for a signal having the subchannel rotation in the subchannel mapping rule.

33. The apparatus of claim 25, wherein the received signals of the first and the third channel are transmitted from a first terminal and the received signals of the second and the fourth channel are transmitted from a second terminal.

34. The apparatus of claim 25, wherein the channel estimating apparatus supports at least one of IEEE 802.16d/e, Wibro, and WiMAX standard.

35. An apparatus for estimating a channel in a MIMO wireless telecommunication system supporting an OFDM or OFDMA, the apparatus comprising:

FFT means transforming signals of a first channel and a second channel received through a first receiving antenna and signals of a third channel and a fourth channel received through a second receiving antenna, from a time domain to a frequency domain;

subchannel mapping rule determining means for determining a subchannel mapping rule respectively for the received signals of the first channel to the fourth channel;

time offset processing means for estimating a time offset for a corresponding received signal, by using two or more pilots included in at least one received signal among the received signal of the first channel to the fourth channel, which are transformed into the frequency domain; and

channel estimating means estimating a channel of each of the received signal by using a channel compensation value of a corresponding tile which is obtained by calculating the channel estimation value of each tile adjacent in the direction of the OFDMA symbol axis and reflecting a calculated channel estimation value of an adjacent tile into a channel estimation value of the corresponding tile, for a signal having no subchannel rotation in the subchannel mapping rule among the received signals of the first channel to the fourth channel transmitted from the time offset processing means.

36. The apparatus of claim 35, wherein the time offset processing means estimates a time offset by using a linear phase compensation value according to the time offset of a corresponding slot region, which is produced by averaging the linear phase according to the time offset for an individual slot by slot region, calculating the linear phase average value according to the time offset of by slot region, and reflecting a linear phase average value according to the time offset of the adjacent slot region into the linear phase average value according to the time offset of the corresponding slot region.

37. An apparatus for estimating a time offset in a MIMO wireless telecommunication system supporting an OFDM or OFDMA, the apparatus comprising:

FFT means for transforming signals of a first channel and a second channel received through a first receiving antenna and signals of a third channel and a fourth channel received through a second receiving antenna, from a time domain to a frequency domain;

subchannel mapping rule determining means for determining a subchannel mapping rule respectively for the received signals of the first channel to the fourth channel; and

time offset processing means for estimating a time offset for a corresponding received signal by using pilots respectively included in a plurality of tiles or slots adjacent in the direction of the OFDMA symbol axis, for a received signal having no subchannel rotation in the subchannel mapping rule among the received signals of the first channel to the fourth channel, which are transformed into the frequency domain.

38. The apparatus of claim 37, wherein the time offset processing means estimates a time offset by using a linear phase compensation value according to the time offset of a corresponding slot region, which is produced by averaging the linear phase according to the time offset for an individual slot by slot region, calculating the linear phase average value according to the time offset by slot region, and reflecting a linear phase average value according to the time offset of the adjacent slot region into the linear phase average value according to the time offset of the corresponding slot region.

39. The apparatus of claim 38, wherein the linear phase compensation value according to the time offset of the corresponding slot region is calculated by multiplying the linear phase average value according to the time offset of the corresponding slot region and the linear phase average value according to the time offset of the adjacent slot region by a weight respectively.

40. The apparatus of claim 37, wherein the time offset processing means includes a time offset estimating means comprising:

a phase difference operator for calculating a phase difference according to a time offset for two or more pilots included in each tile;

a phase difference accumulator for accumulating a phase difference according to the calculated time offset;

a linear phase operator for calculating a linear phase according to a time offset by slot region by using a phase difference according to the accumulated time offset; and

a time offset operator for calculating the time offset based on the linear phase according to the time offset.

41. The apparatus of claim 37, wherein the time offset processing means estimates the time offset by using a tile or a slot corresponding to the same slot region, for a signal having the subchannel rotation in the subchannel mapping rule.

42. The apparatus of claim 37, wherein the received signals of the first and the third channel are transmitted from a first terminal and the received signals of the second and the fourth channel are transmitted from a second terminal.

43. The apparatus of claim 37, wherein the channel estimating apparatus supports at least one of IEEE 802.16d/e, Wibro, and WiMAX standard.

44. A method for estimating a channel for an uplink PUSC mode in a MIMO wireless telecommunication system supporting an OFDM or OFDMA, the method comprising the steps of:

a) receiving signals transmitted with a spatial multiplexing through the same subcarrier with a different pilot patterns from a first terminal and a second terminal equipped with one transmitting antenna respectively, through a first receiving antenna and a second receiving antenna;

b) estimating and compensating a time offset for a corresponding received signal by using a plurality of slots adjacent in the direction of the OFDMA symbol axis, for a signal having no subchannel rotation in a subchannel mapping rule among the received signals; and

c) estimating a channel by using pilots respectively included in each received signal, for the received signal in which the time offset is compensated.

45. The method of claim 44, wherein the step b) includes the steps of:

b-1) calculating a linear phase average value according to a time offset by slot region by averaging a linear phase according to the time offset for an individual slot by slot region;

b-2) calculating a linear phase compensation value according to a time offset of a corresponding slot region by reflecting a linear phase average value according to a time offset of an adjacent slot region into a linear phase compensation value according into the time offset of the corresponding slot region; and

b-3) estimating a time offset by using the linear phase compensation value of the corresponding slot region.

46. The method of claim 44, wherein the step c) includes the steps of:

c-1) calculating a channel estimation value of each tile adjacent in the direction of the OFDMA symbols axis;

c-2) calculating a channel compensation value of a corresponding tile by reflecting the calculated channel estimation value of the adjacent tile into a channel estimation value of the corresponding tile; and

c-3) estimating a channel of the received signal by using the channel compensation value of the corresponding tile.

47. A method for estimating a channel for an uplink PUSC mode in a MIMO wireless telecommunication system supporting an OFDM or OFDMA, the method comprising the steps of:

a) receiving signals transmitted with a spatial multiplexing through the same subcarrier with different pilot patterns from a first terminal and a second terminal equipped with one transmitting antenna respectively, through a first receiving antenna and a second receiving antenna;

b) estimating and compensating a time offset for a corresponding received signal, by using two or more pilots included in at least one received signal among the received signals; and

c) estimating a channel of the received signal by using the channel compensation value of a corresponding tile, which is produced by calculating the channel estimation value of each tile adjacent in the direction of the OFDMA symbol axis and reflecting the calculated channel estimation value of an adjacent tile into the channel estimation value of the corresponding tile, for a signal having no subchannel rotation in a subchannel mapping rule among the signals in which the time offset is compensated.

48. A method for estimating a time offset for an uplink PUSC mode in a MIMO wireless telecommunication system supporting an OFDM or OFDMA, the method comprising the steps of:

a) receiving signals transmitted with a spatial multiplexing through the same subcarrier with different pilot patterns from a first terminal and a second terminal equipped with one transmitting antenna respectively, through a first receiving antenna and a second receiving antenna; and

b) estimating a the time offset for a corresponding received signal by using pilots respectively included in a plurality of slots which are adjacent in the direction of OFDMA symbol axis, for a signal having no subchannel rotation in a subchannel mapping rule among the received signals.

49. The method of claim 48, wherein the step b) includes the steps of:

b-1) calculating a linear phase average value according to a time offset by slot region by averaging a linear phase according to the time offset for an individual slot by slot region;

b-2) calculating a linear phase compensation value according to a time offset of a corresponding slot region by reflecting a linear phase average value according to a time offset of an adjacent slot region into a linear phase compensation value according into the time offset of the corresponding slot region; and

b-3) estimating a time offset by using the linear phase compensation value of the corresponding slot region.