Apparatus and method for transmitting/receiving pilot signal in communication system using OFDM scheme

• US 7,583,586 B2
• Filed: 06/27/2005
• Issued: 09/01/2009
• Est. Priority Date: 07/02/2004
• Status: Active Grant

• Current Assignee: Nokia Technologies Oy (Nokia Corporation)
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Park, Dong-Seek, Park, Sung-Eun, Choi, Seung-Hoon, Jang, Ji-Ho, Kim, Jae-Yoel, Joo, Pan-Yuh
• Primary Examiner(s): Moore; Ian N
• Assistant Examiner(s): VILLA, JOSE F
• Application Number:
  US11/167,663
• Publication Number:
  US 20060028976A1
• Time in Patent Office: 1,527 Days
• Field of Search: 370203-210, 370/335, 370/342, 370/491, 370/480, 375/25, 375/141, 375/142, 714/755, 714/780
• US Class Current: 370/209
• CPC Class Codes: H04B 2201/70701 featuring pilot assisted reception
• CPC Class Codes: H04B 2201/709709 Methods of preventing interference
• CPC Class Codes: H04J 13/0048 Walsh
• CPC Class Codes: H04J 13/16 Code allocation
• CPC Class Codes: H04L 27/2613 Structure of the reference signals
• CPC Class Codes: H04L 27/262 Reduction thereof by selection of pilot symbols
• CPC Class Codes: H04L 27/2655 Synchronisation arrangements
• 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

Disclosed is a method for transmitting a reference signal for identification of each cell in a communication system including a plurality of cells each of which is identified by a cell identifier. The method includes receiving a cell identifier, and generating a block code corresponding to the cell identifier using a predetermined block code generator matrix, and generating a first part sequence using the block code; selecting a second part sequence in accordance with the cell identifier; generating a reference signal of a frequency domain using the first part sequence and the second part sequence; converting the reference signal of the frequency domain to a reference signal of a time domain through an Inverse Fast Fourier Transform operation and transmitting the reference signal of the time domain in a predetermined reference signal transmission interval.

Claims

1. A method for transmitting a reference signal for identification of each cell in a communication system including a plurality of cells each of which is identified by a cell identifier, the method comprising the steps of:

in response to input of the cell identifier, generating, by a block code encoder, a block code corresponding to the cell identifier using a predetermined block code generator matrix;

generating a first part sequence by interleaving, by an interleaver, the block code according to at least one interleaving scheme and performing, by an adder, an exclusive OR operation on the interleaved block code;

selecting a second part sequence corresponding to the cell identifier and from among predetermined sequences considering Peak-to-Average Power Ratio (PAPR) reduction;

generating, by a combiner, a reference signal of a frequency domain by using the first part sequence and the second part sequence;

converting, by a transmitter, the reference signal of the frequency domain to a reference signal of a time domain through an Inverse Fast Fourier Transform (IFFT) operation; and

transmitting, by the transmitter, the reference signal of the time domain in a over a reference signal transmission interval,

wherein the reference signal of the frequency domain is defined by;

2. The method as claimed in claim 1, wherein the step of converting the reference signal comprises the steps of:

inserting null data into sub-carriers corresponding to DC components and intersubcarrier interference eliminating components from among N sub-carriers;

inserting elements of the reference signal into M sub-carriers other than the sub-carriers into which the null data is inserted from among the N sub-carriers; and

performing an IFFI operation on a signal including the reference signal elements and the M sub-carriers and then transmitting the signal.

3. The method as claimed in claim 2, wherein inserting elements of the reference signal is performed in consideration of a predetermined offset that is set to have a specific value for each of the cells and sectors.

4. The method as claimed in claim 1, wherein the setup sequence is defined by:

5. The method as claimed in claim 4, wherein the block code generator matrix is defined as

6. The method as claimed in claim 5, wherein the interleaving scheme is defined by Π

(r) as shown;

7. An apparatus for transmitting a reference signal for identification of each cell in a communication system including a plurality of cells each of which is identified by a cell identifier, the apparatus comprising:

a block code encoder which, in response to input of the cell identifier, generates a block code corresponding to the cell identifier by using a predetermined block code generator matrix;

an interleaver for interleaving the block code according to at least one interleaving scheme;

an adder for performing an exclusive OR operation on the interleaved block code, thereby generating a first part sequence;

a combiner for generating a reference signal of a frequency domain by using the first part sequence and a second part sequence which is selected corresponding to the cell identifier and from among predetermined sequences; and

a transmitter for converting the reference signal of the frequency domain to a reference signal of a time domain through an Inverse Fast Fourier Transform (IFFT) and, operation and then transmitting the reference signal of the time domain over a reference signal transmission interval,

where the reference signal of the frequency domain is defined by;

8. The apparatus as claimed in claim 7, wherein the block code generator matrix includes b number of sub-blocks, each of which includes c number of Walsh bases and d number of mask sequences, and the b sub-blocks including a first sub-block to a b-th sub-block have a relation of cyclic shift between each other, so as to maximize a minimum distance of the block code generated by using the block code generator matrix.

9. The apparatus as claimed in claim 8, wherein the interleaver divides the block code into the b sub-blocks and interleaves the b sub-blocks according to b number of interleaving schemes differently set for the b sub-blocks.

10. The apparatus as claimed in claim 7, wherein the transmitter comprises:

an Inverse Fast Fourier Transform (IFFT) unit for inserting null data into sub-carriers corresponding to DC components and intersubcarrier interference eliminating components from among N sub-carriers, inserting elements of the reference signal into M sub-carriers other than the sub-carriers into which the null data is inserted from among the N sub-carriers, and then performing an IFFT operation on a signal including the reference signal of the frequency domain elements and the M sub-carriers; and

a Radio Frequency (RF) processor for processing and transmitting the IFFT-processed signal.

11. The apparatus as claimed in claim 7, wherein the transmitter comprises:

an IFFT unit for inserting null data into sub-carriers corresponding to DC components and intersubcarrier interference eliminating components from among N sub-carriers, inserting elements of the reference signal into M sub-carriers other than the sub-carriers into which the null data is inserted from among the N sub-carriers, in consideration of a predetermined offset, and then performing an IFFT operation on a signal including the reference signal of the frequency domain elements and the M sub-carriers and then transmitting the signal; and

a Radio Frequency (RF) processor for processing and transmitting the IFFT-processed signal.

12. The apparatus as claimed in claim 11, wherein the offset is set to have a specific value for each of the cells and sectors.

13. The apparatus as claimed in claim 7, wherein the setup sequence is defined by:

14. The apparatus as claimed in claim 13, wherein the block code generator matrix is expressed as

15. The apparatus as claimed in claim 14, wherein the interleaving scheme is defined as Π

(r) as shown;

16. A method for receiving a reference signal for identification of each cell in a communication system including a plurality of cells each of which is identified by a cell identifier, the method comprising:

extracting, by a reference signal extractor, the reference signal from a received signal which has been converted through a Fast Fourier Transform (FFT) operation;

dividing, by an adder, the reference signal into a predetermined number of intervals and performing an exclusive OR (XOR) operation on the divided intervals;

deinterleaving, by a deinterleaver, the XOR-processed signal according to at least one deinterleaving scheme;

dividing, by a sub-block divider, the deinterleaved signal into sub-block signals in accordance with a predetermined block code generator matrix;

performing, by a block code decoder, an Inverse Fast Hadamard Transform (IFHT) using mask sequences generated according to control of each of the sub-block signals;

generating, by a combiner, a combined signal by combining the IFHT-processed signals for each of the sub-block signals; and

determining, by a comparison selector, a cell identifier corresponding to a block code having a maximum correlation value from among the combined signals as a final cell identifier,

wherein the reference signal of the frequency domain is defined by;

17. The method as claimed in claim 16, wherein, in the step of extracting, the reference signal is extracted by eliminating a predetermined sequence from a signal received through M sub-carriers other than sub-carriers corresponding to DC components and intersubcarrier interference eliminating components from among N sub-carriers.

18. The method as claimed in claim 17, wherein the eliminating is performed in consideration of a predetermined offset that is set to have a specific value for each of the cells and sectors.

19. The method as claimed in claim 16, wherein the setup sequence is defined by:

20. The method as claimed in claim 19, wherein the block code generator matrix is defined as:

21. The method as claimed in claim 20, wherein the deinterleaving scheme is defined to correspond to an interleaving scheme Π

(r) as shown in;

22. The method as claimed in claim 21, wherein the setup sequence is set to have a minimum Peak to Average Power Ratio (PAPR) for the reference signal.

23. An apparatus for receiving a reference signal for identification of each cell in a communication system including a plurality of cells each of which is identified by a cell identifier, the apparatus comprising:

a Fast Fourier Transform (FFT) unit for performing an FFT operation on a received signal;

a reference signal extractor for extracting the reference signal from the FFT-processed signal;

an adder for dividing the reference signal into a predetermined number of intervals and performing an exclusive OR (XOR) operation on the divided intervals;

a deinterleaver for deinterleaving the XOR-processed signal according to at least one deinterleaving scheme;

a sub-block divider for dividing the deinterleaved signal into sub-block signals in accordance with a predetermined block code generator matrix;

a block code decoder for performing an Inverse Fast Hadamard Transform (IFHT) using mask sequences generated according to control of each of the sub-block signals;

a combiner for generating a combined signal by combining the IFHT-processed signals for each of the sub-block signals; and

a comparison selector for determining a cell identifier corresponding to a block code having a maximum correlation value from among the combined signals as a final cell identifier,

wherein the reference signal of the frequency domain is defined by;

24. The apparatus as claimed in claim 23, wherein the reference signal extractor extracts the reference signal by eliminating a predetermined sequence from a signal received through M sub-carriers other than sub-carriers corresponding to DC components and intersubcarrier interference eliminating components from among N sub-carriers.

25. The apparatus as claimed in claim 24, wherein the eliminating is performed in consideration of a predetermined offset that is set to have a specific value for each of the cells and sectors.

26. The apparatus as claimed in claim 23, wherein the setup sequence is defined by:

27. The apparatus as claimed in claim 23, wherein the block code generator matrix is defined as:

28. The apparatus as claimed in claim 27, wherein the deinterleaving scheme corresponds to an interleaving scheme Π

(r) as shown in;

29. The apparatus as claimed in claim 28, wherein the setup sequence is set to have a minimum Peak to Average Power Ratio (PAPR) for the reference signal.

30. A method for transmitting a reference signal for identification of each cell through at least one transmit antenna in a communication system including a plurality of cells each of which is identified by a cell identifier, the method comprising:

receiving a cell identifier;

generating, by a block code encoder, a block code corresponding to the cell identifier by using a predetermined block code generator matrix;

selecting a Walsh code corresponding to the cell identifier from among predetermined Walsh codes, and repeating the selected Walsh code a predetermined number of times;

interleaving, by an interleaver, the block code according to at least one interleaving scheme and performing, by an adder, an exclusive OR operation on the interleaved block code and the repeated Walsh code, thereby generating a first part sequence;

selecting a second part sequence corresponding to the cell identifier from among predetermined sequences;

generating, by a combiner, a reference signal of a frequency domain by using the first part sequence and the second part sequence; and

converting, by a transmitter, the reference signal of the frequency domain to a reference signal of a time domain through an Inverse Fast Fourier Transform (IFFT) operation and then transmitting the reference signal of the time domain in a predetermined reference signal transmission interval,

wherein the reference signal of the frequency domain is defined by;

31. The method as claimed in claim 30, wherein the block code generator matrix includes b number of sub-blocks, each of which includes c number of Walsh bases and d number of mask sequences.

32. The method as claimed in claim 31, wherein the b sub-blocks including a first sub-block to a b-th sub-block have a relation of cyclic shift between each other, so as to maximize the minimum distance of the block code generated by using the block code generator matrix.

33. The method as claimed in claim 31, wherein the step of interleaving comprises the steps of:

dividing the block code into the b sub-blocks; and

interleaving the b sub-blocks according to b number of interleaving schemes differently set for the b sub-blocks.

34. The method as claimed in claim 33, wherein the step of converting comprises the steps of:

inserting null data into sub-carriers corresponding to DC components and intersubcarrier interference eliminating components from among N sub-carriers;

inserting elements of the reference signal into M sub-carriers other than the sub-carriers into which the null data is inserted from among the N sub-carriers; and

performing an Inverse Fast Fourier Transform (IFFT) operation on a signal including the reference signal elements and the M sub-carriers.

35. The method as claimed in claim 33, wherein the step of converting comprises the steps of:

inserting null data into sub-carriers corresponding to DC components and intersubcarrier interference eliminating components from among N sub-carriers;

inserting elements of the reference signal into M sub-carriers other than the sub-carriers into which the null data is inserted from among the N sub-carriers, in consideration of a predetermined offset; and

performing an IFFT operation on a signal including the reference signal elements and the M sub-carriers and then transmitting the signal.

36. The method as claimed in claim 35, wherein the offset is set to have a specific value for each of the cells and sectors.

37. The method as claimed in claim 30, wherein the setup sequence is defined by:

38. The method as claimed in claim 37, wherein R(r) is defined by an equation,

39. The method as claimed in claim 38, wherein the block code generator matrix is defined as:

40. The method as claimed in claim 38, wherein the interleaving scheme is defined by Π

(r) as shown in;

41. The method as claimed in claim 38, wherein T(k) has one of values as expressed in:

42. The method as claimed in claim 38, wherein q_IDcell[m] has one of values as expressed in:

43. The method as claimed in claim 38, wherein the interleaving scheme is defined by Π

(r) as shown in;

44. The method as claimed in claim 37, wherein R(r) is defined:

45. The method as claimed in claim 44, wherein the block code generator matrix is defined as:

46. The method as claimed in claim 44, wherein T(k) has one of values as expressed in:

47. The method as claimed in claim 44, wherein q_IDcell[m] has one of values as expressed in:

48. The method as claimed in claim 37, wherein R(r) is defined by:

49. The method as claimed in claim 48, wherein the block code generator matrix is defined as:

50. The method as claimed in claim 48, wherein the interleaving scheme is defined by Π

(r) as shown in;

51. The method as claimed in claim 48, wherein T(k) has one of values as expressed in:

52. The method as claimed in claim 48, wherein q_IDcell[m] has one of values as expressed in:

53. A method for providing a pilot symbol for base station identification in a Multiple-Input Multiple-Output (MIMO) communication system having one or more transmit antennas, the method comprising:

generating, by a pilot signal generator, the pilot symbol,

wherein the pilot symbol is comprised of a first sequence having a good cell identification characteristic and a second sequence for reducing a peak-to-average power ratio (PAPR) for all of pilot symbols,

wherein when the number of the transmit antennas is two and an FFT operation point has a value of 128, the first sequence R(r) is determined by

54. The method of claim 53, wherein the first sequence is created by block-coding information to be transmitted from a base station to a mobile station.

55. The method of claim 54, wherein the information to be transmitted from the base station to the mobile station is a cell identifier (ID).

56. The method of claim 53, wherein the second sequence is created from a predetermined reference table taking the first sequence into account.

57. The method of claim 53, wherein the pilot symbol for base station identification is determined by the following equation in which the first sequence and the second sequence are reflected,