Apparatus and method for estimating channel in ofdm/ofdma based wireless communication system

Abstract

A channel estimation apparatus of the present invention includes a preamble channel operation unit for carrying out an operation on pilot channel estimation values of pilots, which are transmitted from a transmitting antenna that transmits a preamble, as an improved pilot channel estimation value by employing a preamble channel estimation value based on a preamble included in received signals respectively received by a plurality of receiving antennas, a first channel estimation unit for estimating a channel for each of the receiving antennas through interpolation of a symbol axis and a frequency axis employing the improved pilot channel estimation value, and a second channel estimation unit for estimating a channel for each of the receiving antennas through interpolation of a symbol axis and a frequency axis employing pilot channel estimation values of pilots transmitted from the same transmitting antenna, of pilots transmitted from a transmitting antenna that does not transmit the preamble, of a plurality of transmitting antennas.

1 . A channel estimation apparatus in a Multiple Input Multiple Output (MIMO) wireless communication system supporting OFDM or OFDMA, the channel estimation apparatus comprising:
 a first channel operation unit for carrying out an operation on pilot channel estimation values of pilots, which are transmitted from a transmitting antenna that transmits a preamble, as an improved pilot channel estimation value with respect to each of a plurality of receiving antennas by employing a preamble channel estimation value based on the preamble included in received signals received by the plurality of receiving antennas, respectively;   a first channel estimation unit for estimating a channel for each of the receiving antennas through interpolation of a symbol axis and a frequency axis employing the improved pilot channel estimation value; and   a second channel estimation unit for estimating a channel for each of the receiving antennas through interpolation of a symbol axis and a frequency axis employing pilot channel estimation values of pilots transmitted from the same transmitting antenna, of pilots transmitted from a transmitting antenna that does not transmit the preamble, of a plurality of transmitting antennas.   
     
     
         2 . The channel estimation apparatus according to  claim 1 , wherein the first channel operation unit carries out an operation on the pilot channel estimation value as an improved pilot channel estimation value by employing the preamble channel estimation value only when the preamble channel estimation value and the pilot channel estimation values of the pilots transmitted from the transmitting antenna that transmits the preamble are located at the same frequency. 
     
     
         3 . The channel estimation apparatus according to  claim 2 , wherein the improved pilot channel estimation value is decided according to the following Equation.
     H ( a,s )= W 1( a,s )× H _pre( a, s )+ W 2( a, s )× H _pil( a,s )  [Equation]   (“H” indicates the improved pilot channel estimation value, “W 1 ” indicates a preamble weight value, “H_pre” indicates the preamble channel estimation value, “W 2 ” indicates a pilot weight value, “H_pil” indicates the pilot channel estimation values of the pilots transmitted from the transmitting antenna, “a” indicates a subcarrier index, and “s” indicates a symbol index).   
     
     
         4 . The channel estimation apparatus according to  claim 3 , wherein the preamble weight value and the pilot weight value are decided according to the following Equation.
                 W                 1     =     1     2         symbol                 offset     +   2     2                 [   Equation   ]                 W 2=1− W 1   (symbol offset is symbol offset based on a preamble)   
     
     
         5 . The channel estimation apparatus according to  claim 1 , wherein the first channel estimation unit comprises:
 a first symbol index channel estimation unit for estimating a channel of the symbol axis with respect to each of the receiving antennas through interpolation of the symbol axis employing the improved pilot channel estimation value with respect to each of the receiving antennas; and   a first frequency axis channel estimation unit for estimating a channel of the frequency axis with respect to each of the receiving antennas through interpolation of the frequency axis employing a channel estimation value estimated as the symbol axis with respect to each of the receiving antennas.   
     
     
         6 .- 8 . (canceled) 
     
     
         9 . The channel estimation apparatus according to  claim 1 , wherein the second channel estimation unit comprises:
 a second symbol index channel estimation unit for estimating a channel of the symbol axis with respect to each of the receiving antennas through interpolation of the symbol axis employing the pilot channel estimation values of the pilots transmitted from the same transmitting antenna; and   a second frequency axis channel estimation unit for estimating a channel of the frequency axis with respect to each of the receiving antennas through interpolation of the frequency axis employing a channel estimation value estimated as the symbol axis with respect to each of the receiving antennas.   
     
     
         10 .- 11 . (canceled) 
     
     
         12 . The channel estimation apparatus according to  claim 1 , wherein the pilot has a symbol structure related to downlink Partial Usage of Sub-Channel (PUSC) mode. 
     
     
         13 .- 14 . (canceled) 
     
     
         15 . A channel estimation apparatus in a MIMO wireless communication system supporting OFDM or OFDMA, the channel estimation apparatus comprising:
 a first channel estimation unit for estimating a channel for each of a plurality of receiving antennas through interpolation of a symbol axis and a frequency axis employing pilot channel estimation values of pilots transmitted from a transmitting antenna, which transmits a preamble included in received signals received by the respective receiving antennas;   a first channel operation unit for estimating an improved channel with respect to each of the receiving antennas through operation of the estimated channel estimation value and a preamble channel estimation value of the preamble; and   a second channel estimation unit for estimating a channel for each of the receiving antennas through interpolation of a symbol axis and a frequency axis employing pilot channel estimation values of pilots transmitted from the same transmitting antenna, of pilots transmitted from a transmitting antenna that does not transmit the preamble, of a plurality of transmitting antennas.   
     
     
         16 . The channel estimation apparatus according to  claim 15 , wherein the first channel estimation unit comprises:
 a first symbol index channel estimation unit for estimating a channel of the symbol axis with respect to each of the receiving antennas through interpolation of the symbol axis employing the pilot channel estimation values of the pilots; and   a first frequency axis channel estimation unit for estimating a channel of the frequency axis with respect to each of the receiving antennas through interpolation of the frequency axis employing channel estimation values estimated along the symbol axis with respect to each of the receiving antennas.   
     
     
         17 .- 19 . (canceled) 
     
     
         20 . The channel estimation apparatus according to  claim 15 , wherein the second channel estimation unit comprises:
 a second symbol index channel estimation unit for estimating a channel of the symbol axis with respect to each of the receiving antennas through interpolation of the symbol axis employing the pilot channel estimation values of the pilots transmitted from the same transmitting antenna; and   a second frequency axis channel estimation unit for estimating a channel of the frequency axis with respect to each of the receiving antennas through interpolation of the frequency axis employing a channel estimation value estimated as the symbol axis with respect to each of the receiving antennas.   
     
     
         21 .- 22 . (canceled) 
     
     
         23 . The channel estimation apparatus according to  claim 15 , wherein the first channel operation unit estimates the improved channel by employing the preamble channel estimation value only when the preamble channel estimation value and the estimated channel estimation value are located the same frequency. 
     
     
         24 . The channel estimation apparatus according to  claim 23 , wherein the improved channel estimation value is decided according to the following Equation.
     H 1( a, s )= W 3( a, s )× H _pre( a, s )+ W 4( a, s )× H _pil1( a, s )  [Equation]   (“H 1 ” indicates the improved channel estimation value, “W 3 ” indicates a preamble weight value, “H_pre” indicates the preamble channel estimation value, “W 4 ” indicates the estimated channel weight value, “H_pil” indicates the estimated channel estimation value, “a” indicates a subcarrier index, and “s” indicates the symbol index).   
     
     
         25 . The channel estimation apparatus according to  claim 24 , wherein the preamble weight value and the estimated channel weight value are decided according to the following Equation.
                 W                 3     =     1     2         symbol                 offset     +   2     2                 [   Equation   ]                 W 4=1 −W 3   (symbol offset is symbol offset on the basis of a preamble).   
     
     
         26 .- 28 . (canceled) 
     
     
         29 . A channel estimation apparatus in a MIMO wireless communication system supporting OFDM or OFDMA, the channel estimation apparatus comprising:
 a first channel operation unit for carrying out an operation on pilot channel estimation values of pilots as improved pilot channel estimation values by employing a preamble channel estimation value of a preamble, of the preamble and the pilots included in a first received signal received from a first transmitting antenna through a first receiving antenna;   a first channel estimation unit for estimating a channel with respect to the first received signal through interpolation of a symbol axis and a frequency axis employing the improved pilot channel estimation value; and   a second channel estimation unit for estimating a channel with respect to a second received signal, received from a second transmitting antenna through the first receiving antenna, through interpolation of a symbol axis and a frequency axis employing pilot channel estimation values based on pilots included in the second received signal.   
     
     
         30 . The channel estimation apparatus according to  claim 29 , further comprising:
 a third channel operation unit for carrying out an operation on a pilot channel estimation value based on pilots included in a third received signal, received from the first transmitting antenna through a second receiving antenna, as an improved pilot channel estimation value by employing a preamble channel estimation value based on a preamble included in the third received signal, of the preamble and the pilots included in the third received signal;   a third channel estimation unit for estimating a channel with respect to the third received signal through interpolation of a symbol axis and a frequency axis by employing the improved pilot channel estimation value of the pilots include in the third received signal; and   a fourth channel estimation unit for estimating a channel with respect to a fourth received signal, received from the second transmitting antenna through the second receiving antenna, through interpolation of a symbol axis and a frequency axis by employing a pilot channel estimation value based on pilots included in a fourth received signal.   
     
     
         31 . A channel estimation apparatus in a MIMO wireless communication system supporting OFDM or OFDMA, the channel estimation apparatus comprising:
 a first channel estimation unit for estimating a channel with respect to a first received signal, taken from a first transmitting antenna through a first receiving antenna, through interpolation of a symbol axis and a frequency axis employing pilot channel estimation values of pilots, of a preamble and the pilots included in the first received signal;   a first channel operation unit for estimating an improved channel with respect to the first received signal through operation of the estimated channel estimation value and a preamble channel estimation value of the preamble; and   a second channel estimation unit for estimating a channel with respect to a second received signal, received from a second transmitting antenna through the first receiving antenna, through interpolation of a symbol axis and a frequency axis employing a pilot channel estimation value based on pilots included in the second received signal.   
     
     
         32 . The channel estimation apparatus according to  claim 31 , further comprising:
 a third channel estimation unit for estimating a channel with respect to a third received signal received from the first transmitting antenna from a second receiving antenna through interpolation of a symbol axis and a frequency axis employing a pilot channel estimation value based on pilots included in the third received signal, of a preamble and the pilots included in the third received signal;   a third channel operation unit for estimating an improved channel with respect to the third received signal through operation of the channel estimation value estimated with respect to the third received signal and a preamble channel estimation value based on the preamble included in the third received signal; and   a forth channel estimation unit for estimating a channel with respect to a forth received signal, received from a second transmitting antenna through the second receiving antenna, through interpolation of a symbol axis and a frequency axis employing a pilot channel estimation value based on pilots included in the forth received signal.   
     
     
         33 .- 34 . (canceled) 
     
     
         35 . A channel estimation apparatus in a wireless communication system supporting OFDM or OFDMA, the channel estimation apparatus comprising:
 a TO estimation unit for estimating time offset using a received signal;   a TO compensation unit for compensating for phase error using the estimated time offset;   a weight value storage unit configured to store predetermined calculated weight values; and   at least one channel estimation unit for estimating a channel of the received signal by employing the product of pilot channel estimation values, with respect to the received signal whose time offset has been compensated for, and the weight values.   
     
     
         36 . (canceled) 
     
     
         37 . The channel estimation apparatus according to  claim 35 , wherein the weight value storage unit is configured to store weight values with respect to pilots having a number decided according to a symbol index and a pilot pattern of a subcluster. 
     
     
         38 . The channel estimation apparatus according to  claim 35 , wherein the weight values are decided according to a relative symbol distance ratio of pilots disposed on the basis of a subcluster. 
     
     
         39 . The channel estimation apparatus according to  claim 35 , wherein a weight value with respect to a pilot disposed close to the subcluster is greater than a weight value with respect to a pilot disposed far from the subcluster. 
     
     
         40 . The channel estimation apparatus according to  claim 35 , wherein the channel estimation unit estimates the channel per subcluster basis. 
     
     
         41 .- 44 . (canceled) 
     
     
         45 . A channel estimation method in a MIMO wireless communication system supporting OFDM or OFDMA, the method comprising the steps of:
 carrying out an operation on pilot channel estimation values of pilots, which are transmitted from a transmitting antenna that transmits a preamble, as an improved pilot channel estimation value with respect to each of a plurality of receiving antennas by employing a preamble channel estimation value based on the preamble included in received signals received by the plurality of receiving antennas, respectively;   estimating a channel for each of the receiving antennas through interpolation of a symbol axis and a frequency axis employing the improved pilot channel estimation value; and   estimating a channel for each of the receiving antennas through interpolation of a symbol axis and a frequency axis employing pilot channel estimation values of pilots transmitted from the same transmitting antenna, of pilots transmitted from a transmitting antenna that does not transmit the preamble, of a plurality of transmitting antennas.   
     
     
         46 . The channel estimation method according to  claim 45 , wherein the step of carrying out an operation on pilot channel estimation values of pilots, which are transmitted from a transmitting antenna that transmits a preamble, as an improved pilot channel estimation value with respect to each receiving antennas comprises the step of carrying out an operation on the pilot channel estimation value as an improved pilot channel estimation value by employing the preamble channel estimation value only when the preamble channel estimation value and the pilot channel estimation values of the pilots transmitted from the transmitting antenna that transmits the preamble are located at the same frequency. 
     
     
         47 . The channel estimation method according to  claim 46 , wherein the improved pilot channel estimation value is decided according to the following Equation.
     H ( a,s )= W 1( a,s )× H _pre( a, s )+ W 2( a, s )× H _pil( a,s )  [Equation]   
       (“H” indicates the improved pilot channel estimation value, “W 1 ” indicates a preamble weight, “H_pre” indicates the preamble channel estimation value, “W 2 ” indicates a pilot weight value, “H_pil” indicates the pilot channel estimation values of the pilots transmitted from the transmitting antenna, “a” indicates a subcarrier index, and “s” indicates a symbol index). 
     
     
         48 . The channel estimation method according to  claim 47 , wherein the preamble weight and the pilot weight value are decided according to the following Equation.
                 W                 1     =     1     2         symbol                 offset     +   2     2                 [   Equation   ]                 W 2=1 −W 1   (symbol offset is symbol offset based on a preamble)   
     
     
         49 . The channel estimation method according to  claim 45 , wherein the step of estimating a channel with respect to each of the receiving antennas through interpolation of a symbol axis and a frequency axis employing the improved pilot channel estimation value comprises the steps of:
 estimating a channel of the symbol axis with respect to each of the receiving antennas through interpolation of the symbol axis employing the improved pilot channel estimation value with respect to each of the receiving antennas; and   estimating a channel of the frequency axis with respect to each of the receiving antennas through interpolation of the frequency axis employing a channel estimation value estimated as the symbol axis with respect to each of the receiving antennas.   
     
     
         50 .- 52 . (canceled) 
     
     
         53 . The channel estimation method according to  claim 45 , wherein the step of estimating a channel with respect to each of the receiving antennas through interpolation of a symbol axis and a frequency axis employing pilot channel estimation values of pilots transmitted from the same transmitting antenna comprises the steps of:
 estimating a channel of the symbol axis with respect to each of the receiving antennas through interpolation of the symbol axis employing the pilot channel estimation values of the pilots transmitted from the same transmitting antenna; and   estimating a channel of the frequency axis with respect to each of the receiving antennas through interpolation of the frequency axis employing a channel estimation value estimated as the symbol axis with respect to each of the receiving antennas.   
     
     
         54 .- 55 . (canceled) 
     
     
         56 . The channel estimation method according to  claim 45 , wherein the pilot has a symbol structure related to downlink PUSC mode. 
     
     
         57 .- 58 . (canceled) 
     
     
         59 . A channel estimation method in a MIMO wireless communication system supporting OFDM or OFDMA, the method comprising the steps of:
 estimating a channel for each of a plurality of receiving antennas through interpolation of a symbol axis and a frequency axis employing pilot channel estimation values of pilots transmitted from a transmitting antenna, which transmits a preamble included in received signals received by each of the receiving antennas;   estimating an improved channel with respect to each of the receiving antennas through operation of the estimated channel estimation value and a preamble channel estimation value of the preamble; and   estimating a channel for each of the receiving antennas through interpolation of a symbol axis and a frequency axis employing pilot channel estimation values of pilots transmitted from the same transmitting antenna, of pilots transmitted from a transmitting antenna that does not transmit the preamble, of a plurality of transmitting antennas.   
     
     
         60 . The channel estimation method according to  claim 59 , wherein the step of estimating a channel with respect to each of the receiving antennas through interpolation of a symbol axis and a frequency axis employing pilot channel estimation values of pilots transmitted from a transmitting antenna that transmits the preamble comprises the steps of:
 estimating a channel of the symbol axis with respect to each of the receiving antennas through interpolation of the symbol axis employing the pilot channel estimation values of the pilots; and   estimating a channel of the frequency axis with respect to each of the receiving antennas through interpolation of the frequency axis employing a channel estimation value estimated as the symbol axis with respect to each of the receiving antennas.   
     
     
         61 .- 63 . (canceled) 
     
     
         64 . The channel estimation method according to  claim 59 , wherein the step of estimating a channel with respect to each of the receiving antennas through interpolation of a symbol axis and a frequency axis employing pilot channel estimation values of pilots transmitted from the same transmitting antenna comprises the steps of:
 estimating a channel of the symbol axis with respect to each of the receiving antennas through interpolation of the symbol axis employing the pilot channel estimation values of the pilots transmitted from the same transmitting antenna; and   estimating a channel of the frequency axis with respect to each of the receiving antennas through interpolation of the frequency axis employing a channel estimation value estimated as the symbol axis with respect to each of the receiving antennas.   
     
     
         65 .- 67 . (canceled) 
     
     
         68 . The channel estimation method according to  claim 59 , wherein the improved channel estimation value is decided according to the following Equation.
     H 1( a, s )= W 3( a, s )× H _pre( a, s )+ W 4( a, s )× H _pil1( a, s )  [Equation]   
       (“H 1 ” indicates the improved channel estimation value, “W 3 ” indicates a preamble weight value, “H_pre” indicates the preamble channel estimation value, “W 4 ” indicates the estimated channel weight value, “H_pil” indicates the estimated channel estimation value, “a” indicates a subcarrier index, and “s” indicates the symbol index). 
     
     
         69 . The channel estimation method according to  claim 68 , wherein the preamble weight value and the estimated channel weight value are decided according to the following Equation.
                 W                 3     =     1     2         symbol                 offset     +   2     2                 [   Equation   ]                 W 4=1 −W 3   (symbol offset is symbol offset on the basis of a preamble).   
     
     
         70 . A channel estimation method in a MIMO wireless communication system supporting OFDM or OFDMA, the channel estimation method comprising the steps of:
 estimating a channel of a symbol axis with respect to each of a plurality of receiving antennas through interpolation of a symbol axis employing pilot channel estimation values of pilots transmitted from the same transmitting antenna, of pilots transmitted from a plurality of transmitting antennas; and   estimating a channel of a frequency axis with respect to each of the receiving antennas through interpolation of the frequency axis employing the channel estimation value estimated as the symbol axis with respect to each of the receiving antennas.   
     
     
         71 . The channel estimation method according to  claim 70 , wherein the step of estimating a channel of the symbol axis with respect to each of a plurality of receiving antennas comprises copying a pilot channel estimation value located at the nearest symbol index, of the pilot channel estimation values of the pilots transmitted from the same transmitting antenna, to a channel not located between the pilot channel estimation values of the pilots transmitted from the same transmitting antenna. 
     
     
         72 . The channel estimation method according to  claim 70 , wherein the step of estimating a channel of the frequency axis with respect to each of a plurality of receiving antennas comprises copying the nearest channel estimation value of the channel estimation values, estimated as the symbol axis, to a channel not located between the channel estimation values estimated as the symbol axis. 
     
     
         73 .- 83 . (canceled) 
     
     
         84 . A channel estimation method in a wireless communication system supporting OFDM or OFDMA, the method comprising the steps of:
 (a) finding a pilot channel estimation value with respect to a pilot obtained in a subcarrier frequency allocation unit; and   (b) estimating a channel by employing weight values, which are predetermined based on at least one of interpolation on a time axis, interpolation on a frequency axis and an moving average, and the pilot channel estimation value.   
     
     
         85 . The channel estimation method according to  claim 84 , wherein in the subcarrier frequency allocation unit, the channel is estimated based on a subcarrier frequency allocation subunit divided into a plurality of subcarriers in an index direction of a subcarrier. 
     
     
         86 . The channel estimation method according to  claim 84 , wherein the weight value is a weight value with respect to pilots having a number, which is decided according to a symbol index and a pilot pattern of the subcarrier frequency allocation subunit, and is previously calculated.