The present invention relates to a receiver of a Multiple Input Multiple Output (MIMO) system, QR decomposition apparatus and method used in the receiver, and a multi-dimensional detection apparatus and method used in the receiver; and, more particularly, to an MIMO receiver for reducing delay in a multi-dimensional receiving process by repeatedly processing predetermined columns and simultaneously processing symbol detection in parallel when QR decomposition is performed in a receiver of Orthogonal Frequency Division Multiplexing (OFDM) MIMO system, a QR decomposition apparatus and method used in the receiver, and multi-dimensional detection apparatus and method used in the receiver.
This work was supported by the IT R&D program of MIC/IITA [2006-S-002-02, “IMT-Advanced Radio Transmission Technology with Low Mobility”].
Wireless communication systems are required to be capable of transmitting a large amount of high-quality multimedia data using limited frequency. As a method for transmitting a large amount of data using a limited frequency, a Multiple Input Multiple Output (MIMO) system was introduced. The MIMO system forms a plurality of independent fading channels using multiple antennas at receiving and transmitting ends and transmits different signals through each of multiple transmission antennas, thereby significantly increasing a data transmission rate. Accordingly, the MIMO system can transmit a great deal of data without expansion of a frequency.
However, the MIMO system has a shortcoming that the MIMO system is weak to inter-symbol interference (ISI) and frequency selective fading. In order to overcome the shortcoming, an orthogonal frequency division multiplexing (OFDM) scheme was used. The OFDM scheme is the most proper modulation scheme for transmitting data at a high speed. The OFDM scheme transmits one data row through a subcarrier having a low data transmission rate.
A channel environment for wireless communication has multiple paths due to obstacles such as a building. In a wireless channel environment having multi-paths, delay spread occurs due to the multiple paths. If delay spray time is longer than a symbol transmission interval, inter-symbol interference (ISI) is caused. In this case, frequency selective fading occurs in a frequency domain. In case of using a single carrier, an equalizer is used to remove the ISI. However, complexity of the equalizer increases as a data transmission rate increases.
The shortcomings of the MIMO system can be attenuated using an orthogonal frequency division multiplexing (OFDM) technology. In order to overcome the shortcomings of the MIMO system while maintain the advantages of the MIMO system, an OFDM technology was applied to an MIMO system having N transmission antennas and N reception antennas. That is, an MIMO-OFDM system was introduced.
Referring to
Referring to
The MIMO receiver 110 generally uses a decision feedback equalizer (DFE), zero forcing (ZF), minimum mean square error estimation (MMSE), and bell labs layered space-time (BLAST). As described above, the MIMO receiver has a problem of low performance although the MIMO receiver has a comparative simple structure compared to maximum likelihood detection (MLD).
Technical Problem
An embodiment of the present invention is directed to providing a Multiple Input Multiple Output (MIMO) receiver for reducing delay in a multi-dimensional receiving process by repeatedly processing predetermined columns and simultaneously processing symbol detection in parallel when QR decomposition is performed in a receiver of Orthogonal Frequency Division Multiplexing (OFDM) MIMO system, a QR decomposition apparatus and method used in the receiver, and a multi-dimensional detection apparatus and method used in the receiver.
Other objects and advantages of the present invention can be understood by the following description, and become apparent with reference to the embodiments of the present invention. Also, it is obvious to those skilled in the art of the present invention that the objects and advantages of the present invention can be realized by the means as claimed and combinations thereof.
Technical Solution
In accordance with an aspect of the present invention, there is provided a receiver of a Multiple Input Multiple Output (MIMO) system, including: a QR decomposing unit for performing a QR decomposing operation in cycles 1 to nT-n−1, and performing a column exchanging operation in cycles nT-n to nT as QR decomposition where n and T are an integer number; and a multi-dimensional detecting unit for receiving a first R matrix Ry and a second R matrix Rz from the QR decomposing unit, calculating a first distance value for detecting an mth symbol for the first R matrix and a second distance value for detecting an mth symbol for the second R matrix, and simultaneously detecting an mth symbol and an (m−1)th symbol using the first distance value and the second distance value.
In accordance with another aspect of the present invention, there is provide a QR decomposition apparatus used in a receiver of a Multiple Input Multiple Output (MIMO) system, including: a norm calculating unit for calculating a vector size norm for a channel input; a Q column calculating unit for calculating a column value of an unitary matrix Q using the channel input and √{square root over (norm)}; a R row calculating unit for calculating a row value of an upper triangular matrix R by receiving the channel input, the output of the Q column calculating unit, and the 1/√{square root over (norm)}; a Q update calculating unit for receiving the channel input, the output of the R column calculating unit, and the output of the Q row calculating unit, and outputting a Q update matrix value; a norm update calculating unit for receiving the output of the norm calculating unit and the output of the R row calculating unit and outputs a norm update matrix value; and a column exchanging unit for column-exchanging a norm value, a Q column value, and a R row value in cycles nT-n to nT where n and T are a natural number, wherein the Q column calculating unit, the R row calculating unit, the Q update calculating unit, and the norm update calculating unit perform calculation using the column-exchanged norm value, the column-exchanged Q column value, and the column-exchanged R row value.
In accordance with another embodiment of the present invention, there is provided a QR decomposition method in a receiver of a Multiple Input Multiple Output (MIMO) system, including the steps of: a) calculating a vector size norm for a channel input; b) calculating a column value of an unitary matrix Q using the channel input and √{square root over (norm)}; c) calculating a row value of an upper triangular matrix R by receiving the channel input, the Q column value, and the 1/√{square root over (norm)}; d) calculating a Q update matrix value using the channel input, the R column value, and the Q row value; e) calculating a norm update matrix value using the norm value and the R matrix value; and f) column-exchanging a norm value, a Q column value, and a R row value in cycles nT-n to nT where n and T are a natural number, and performing additional QR calculation using the column-exchanged norm value, the column-exchanged Q column value, and the column-exchanged R row value.
In accordance with another embodiment of the present invention, there is provided a multi-dimensional detecting apparatus used in a receiver of a Multiple Input Multiple Output (MIMO) system, including: a symbol detecting unit for receiving a first R matrix Ry and a second R matrix Rz from a QR decomposing apparatus as a QR decomposition result of cycles 1 to nT-n−1 and a QR decomposition result additionally calculated through column exchanging, calculating a first distance value for detecting an mth symbol for the first R matrix and a second distance value for detecting an mth symbol for the second R matrix, and simultaneously detecting an mth symbol and an (m−1)th symbol using the first distance value and the second distance value.
In accordance with another embodiment of the present invention, there is provided a multi-dimensional detecting method used in a receiver of a Multiple Input Multiple Output (MIMO) system, including the steps of: a) generating symbols; b) receiving a first R matrix Ry and a second R matrix Rz from a QR decomposing apparatus as a QR decomposition result of cycles 1 to nT-n−1 and a QR decomposition result additionally calculated through column exchanging, receiving the generated symbols, calculating a first distance value for detecting an mth symbol for the first R matrix and a second distance value for detecting an mth symbol for the second R matrix; and c) simultaneously detecting an mth symbol and an (m−1)th symbol using the first distance value and the second distance value.
Advantageous Effects
According to the present invention, a processing delay time can be reduced in a multi-dimensional receiving process by repeatedly processing predetermined columns and simultaneously processing symbol detection in parallel when QR decomposition is performed in a receiver of an MIMO system.
The advantages, features and aspects of the invention will become apparent from the following description of the embodiments with reference to the accompanying drawings, which is set forth hereinafter.
Referring to
The plurality of QAM mappers 202 are sequentially connected to the plurality of IFFTs 203, the CP adders 204, and the DAC & RF units 205, respectively. Since the operations of the QAM mappers 202, the IFFTs 203, the CP adders 204, and the DAC and RF units 205 are identical to those of constituent elements shown in
Referring to
The MIMO receiver and decoder 304 are a multi-dimensional receiver and decoder that demodulate the received symbols from the plurality of FFTs 303.
If it is assumed that the receiver includes M transmission antennas and N receipt antennas, a received signal vector z can be expressed as Eq. 1 in a sub carrier after FFT.
z=Hs+n Eq. 1
In Eq. 1, the received signal vector Z can be expressed as
a channel H can be expressed as
and a transmission symbol s can be expressed as
The channel H can be expressed as H=QR after QR decomposition. Here, R denotes an upper triangular matrix. Since the MIMO system includes N antennas for receiving a signal and M antennas for transmitting a signal, the upper triangular matrix R can be expressed as follow.
Q denotes a Unitary matrix (QHQ=I). Since the channel matrix H is N×M, the unitary matrix Q is N×N and the upper triangular matrix R is N×M. The unitary matrix Q can be expressed as follow.
After QR decomposition, a received signal can be expressed as Eq. 2.
Eq. 2 can be simplified as follow.
The MIMO receiver according to the present embodiment includes a QR decomposition unit, a multi-dimensional detector (MDD), an inverse matrix and weight calculator, an interference remover, and a weight zero forcing (WZF) unit.
The QR decomposition unit calculates the unitary matrix Q, the upper triangular matrix R, and a vector size (norm) from the received signal vector z during a long training field (LTF) period. The QR decomposition unit stores the calculated unitary matrix Q and the upper triangular matrix R, vector sizes (norm) for each element of the unitary matrix Q. Here, the normi is equivalent to ∥qi∥2.
A signal field detector performs detection for a signal field from an output vector of the QR decomposing unit in a SIG interval. The inverse matrix and weight calculator calculates an inverse matrix of the upper triangular matrix R during first two symbol intervals among symbols for receiving data symbols using the calculated upper triangular matrix R and the vector size (1/√{square root over (norm)}). The multi-dimensional detector MDD calculates a log likelihood ratio (LLR) through multiple detections using the output vector y and the upper triangular matrix value of the QR decomposition. The calculated LLR value is inputted to a channel decoder, and used to demodulate the signal.
The interference remover receives the data stream demodulated by the channel decoder, generates symbols corresponding to a data stream demodulated through symbol mapping, and removes interference from the output vector, which is the QR decomposition result, using the generated symbol. The WZF unit performs zero-forcing using the interference removed output vector and the inverse matrix of the upper triangular matrix R. The channel decoder receives the LLR value outputted from the WZF unit and uses the LLR value to demodulate signals.
Referring to
The norm calculator 401 calculates a vector size norm. The norm calculator 401 receives a channel input after Fast Fourier Transform (FFT) and calculates the vector size norm for qi through normi=∥qi∥2. The channel input delay 402 delays the channel input qi in order to use it for calculating a column value of a Q matrix and a row value of an R matrix. The output of the norm calculator 401 is inputted to each of the lookup table ROMs 403 and 404, respectively. Each of the ROMs 403 and 404 outputs and √{square root over (norm)} and 1/√{square root over (norm)} corresponding to the inputted vector size norm through calculation ri,j=√{square root over (norm)}. Also, the output of the norm calculator 401 is delayed by the norm delay 405 for updating a norm value to be used in a following step.
The Q column calculator 406 receives the value outputted from the ROM 403 and the delayed qi from the channel input delay 402, and outputs a Q column value by performing calculation qi:=qi/ri,j. Since the Q column value calculated by the Q column calculator 406 is the result of a QR matrix used for multiple antennas receiving decoding, the Q column value is stored in the Q output memory 407. The calculated Q column value qi from the Q column calculator 406 is inputted to the Q column delay 408 and delayed to be used for Q matrix update to be used in a next step.
The R row calculator 409 receives the calculated Q column value from the Q column calculator 406, the delayed channel input from the channel input delay 402, and 1/√{square root over (norm)} from the ROM 404, and calculates a R row value through calculation ri,j=qiH×qk. The value 1/√{square root over (norm)} outputted from the ROM 404 is used as a diagonal value of an R row. Since the R row value (ri,j) calculated by the R row calculator 409 is the first row value of the R matrix in the QR decomposition, the R row value (ri,j) is stored in the R output memory 410.
The Q update calculator 411 receives the delayed value from the channel input delay 402, the delayed Q column value from the Q column delay, and the R row value from the R row calculator and updates a Q value through calculation qk=qk−ri,j×qi.
The norm update calculator 412 receives the delayed norm value from the norm delay 405, and the R row value from the R row calculator, and updates the norm value through calculation normk:=normk−ri,k2.
The above described processes are the QR decomposition procedure when Nt=1. QR decomposition values from the second antenna to an Nth antenna in the multiple antenna wireless communication system are calculated through the same QR decomposition procedure that is described above. Therefore, the output value of the Q update calculator 411 is inputted to the Q update delay at a next cycle and the output value of the norm update calculator 412 is inputted to lookup table ROMs, respectively, at a next cycle for calculating √{square root over (norm)} and 1/√{square root over (norm)}. As described above, the QR decomposition procedure is repeated as many as the number of multiple antennas.
In order to decide a 8th symbol and a 7th symbol at the same time in the multi-dimensional detection in the present embodiment, the QR decomposition is improved as shown in Eq. 3 in the present embodiment. That is, an additional partial QR decomposition calculation is performed through column exchanging when the QR decomposition is performed for last two columns. Through the partial QR decomposition calculation, the last two columns of the Q matrix are additionally calculated, and the last two rows of the R matrix are also additionally calculated. The computation amount of the additional calculation performed through such column exchanging is not large, for example, about 4%. Eq. 3 shows the improved QR calculation according to the present embodiment.
As shown in Eq. 3, a Q matrix value and an R matrix value are calculated by performing the normi calculation operation in cycles 1 to nT, performing the √{square root over (norm)} calculation operation, the Q column calculation operation, the R row calculation operation, the Q update operation, and the norm update operation in cycles 1 to nT-2. When QR decomposition is performed at cycles nT-1 and nT, a column of a nT-1 value is exchanged with a column of an nT value for norm, a Q matrix value, and an R matrix value, and the √{square root over (norm)} calculation operation, the Q column calculation operation, the R row calculation operation, the Q update operation, and the norm update operation are performed using the exchanged value. Through such a partial QR decomposition, the last two columns of the Q matrix are additionally calculated, and the last two row of the R matrix are additionally calculated.
The example of the additional QR decomposition calculation can be easily expanded to performing QR decomposition until a cycle nT-n and additionally calculating n columns through column exchanging for the last n columns as shown in Eq. 4.
norm(n
q
(n
−(n−1))zn
=q
n
, q
n
zn
=q
(n
−(n−1))
r
(n
−(n−1))zn
=r
n
, r
n
zn
r
(n
−(n−1))
. . .
norm(n
q
(n
−(n−2))zn1
=q
n
, q
n
zn1
=q
n
−(n−2))
r
(n
−(n−2))zn1
=r
n
, r
n
zn1
=r
(n
−(n−2))
. . .
. . .
norm(n
q
(n
−1)z
=q
n
, q
n
z
=q
(n
−1)
r
(n
−1)z
=r
n
, r
n
z
=r
(n
−1) Eq. 4
If Qy, Ry and Qz, Rz denote a Q matrix and an R matrix respectively when two columns are added, QyHz and QzHz can be expressed like Eq. 5. The last symbols at yy and yz are SM and SM−1, and the last symbols SM and SM−1 can be detected through the multi-dimensional detector.
In case of an 8×8 matrix, the last two columns of the Q matrix and the R matrix are like
A multi-dimensional detection apparatus according to an embodiment of the present invention will be described with reference to
Referring to
The symbol generator 601 generates a symbol having lattice points. For example, in case of 16 QAM, a symbol has 16 lattice points. That is, there are 16 distances existed.
The 7th symbol hard-decision and 8th distance calculator 602 receives a first matrix Ry and a second matrix Rz from the QR decomposition apparatus as a QR decomposition result in cycles 1 to nT-n−1 and additional QR decomposition result calculated through nT-n to nT column exchanging, and receives a symbol generated from the symbol generator 601. The 7th symbol hard decision and 8th symbol distance calculator 602 calculates a updated first receiving signal {tilde over (y)}y by performing a first multiplying operation for multiplying an element of the first R matrix and the 8th symbol from the symbol generator, performing a second multiplying operation for multiplying a constant of Eq. 12 and a first receiving signal yy, and subtracting the result of the first multiplying operation from the result of the second multiplying operation. Here, the 8th element and the 7th element of the updated first receiving signal use the 8th element and the 7th element of the added first R matrix.
The 7th symbol hard decision and 8th symbol distance calculator 602 calculates a second receiving signal {tilde over (y)}z updated by multiplying an R element and a 7th symbol and subtracting the multiplying result from the second receiving signal. Here, the 8th element and the 7th element of the updated second receiving signal use the 8th element and the 7th element of the added second R matrix.
The calculated first and second receiving signals {tilde over (y)}y, {tilde over (y)}z are stored in the y register 606.
The 7th symbol hard decision and 8th symbol distance calculator 602 calculates a distance value of a 8th symbol for detecting a 8th symbol of a first receiving signal and performs hard decision on a 7th symbol of the first receiving signal. The 7th symbol hard decision and 8th symbol distance calculator 602 calculates a distance value of a 8th symbol for detecting a 8th symbol of the second receiving signal and performs hard decision on a 7th symbol of the second receiving signal.
The 6th symbol hard decision and 7th symbol distance calculator 603 updates the updated first receiving signal again by multiplying an element of a first R matrix and the hard decision result of the 7th symbol of the first receiving signal and subtracting the multiplying result from the updated first receiving signal stored in the y register 606. Here, the 7th element of the first receiving signal uses a 7th element of an added first R matrix. Then, the 6th symbol hard decision and 7th symbol distance calculator 603 calculates a distance value of a 7th symbol for detecting a 8th symbol of the first receiving signal and performs hard decision on a 6th symbol of the first receiving signal.
The 6th symbol hard decision and 7th symbol distance calculator 603 updates the updated second receiving signal again by multiplying an element of the second R matrix and the hard decision result of the 7th symbol of the second receiving signal and subtracting the multiplying result from the updated second receiving signal stored in the y register 606.
Here, the 7th element of the updated second receiving signal uses an added 7th element of a second R matrix. And, the 6th symbol hard decision and 7th symbol distance calculator 603 calculates a distance value of a 7th symbol for detecting a 8th symbol of a second receiving signal and performs hard decision on a 6th symbol of the second receiving signal. Then, the updated first receiving signal and the updated second receiving signal are stored in the y register 606.
The 5th symbol hard decision and 6th symbol distance calculator updates the updated first receiving signal again by multiplying an element of a first R matrix and the hard decision result of the 6th symbol of the first receiving signal and subtracting the multiplying result from the updated first receiving signal stored in the y register 606. Then, the 5th symbol hard decision and 6th symbol distance calculator calculates a distance value of a 6th symbol for detecting an 8th symbol of the first receiving signal and performs hard decision on a 5th symbol of the first receiving signal.
The 5th symbol hard decision and 6th symbol distance calculator updates the updated second receiving signal again by multiplying an element of a second R matrix with the hard decision result of the 6th symbol of the second receiving and subtracting the multiplying result from the updated second receiving signal stored in the y resister 606. Then, the 5th symbol hard decision and 6th symbol distance calculator calculates a distance value of a 6th symbol for detecting a 8th symbol of a second receiving signal and performs hard decision for 5th symbol of the second receiving signal. Then, the updated first updated signal and the updated second receiving signal are stored in the y register 606.
By performing the same procedure described above, a 5th symbol distance, a 4th symbol distance, a 3rd symbol distance, a 2nd symbol distance and a 1st symbol distance are calculated for detecting a 8th symbol.
The distance accumulating buffer 607 accumulates the distance values of each symbol element and stores the accumulated distance value for detecting an 8th symbol. The distance values stored in the distance accumulating buffer 607 are transferred to the LLR calculator 609 and the symbol decider 608.
The symbol decider 608 decides a symbol having a minimum value among the distance values calculated for detecting an 8th symbol using a first R matrix as a 8th symbol and decides a symbol having a minimum value among the distance values calculated for detecting a 8th symbol using a second R matrix. The LLR calculator 609 calculates an LLR for a 8th symbol and an LLR for a 7th symbol using the calculated distance values.
The process of deciding the 8th symbol and the 7th symbol can be described as a cycle as follows.
In {tilde over (y)}y,1,8,8,x, a first subscript y is shown as a yy vector in Eq. 5, a second subscript denotes a cycle, a third subscript denotes a symbol number to estimate, a fourth subscript is an element number of a y vector, and a fifth subscript x denotes the number of symbols generated by the symbol generator. The fifth subscript x may be smaller than 4 in case of QPSK, smaller than 16 in case of 16 QAM, and smaller than 64 in case of 64 QAM. In Ey,8,8,x, a first subscript y denotes a subscript y of Eq. 5, a second subscript denotes a symbol number to estimate, a fourth subscript is an element number of a vector for calculating a distance value, and a fourth subscript denotes the number of symbols generated from the symbol generator. In {tilde over (s)}y,8,7,x, a first subscript denotes a subscript y of Eq. 5, a second subscript denotes a symbol number to estimate, a third subscript is an element number of a vector for hard decision, and a fourth subscript is the number of symbols generated from the symbol generator. The first cycle can be expressed as Eq. 6.
{tilde over (y)}
y,1,8,8,x
=Cy
y,8
−r
y,8,8
s
8,x
{tilde over (y)}
y,1,8,7,x
=Cy
y,7
−r
y,7,8
s
8,x
{tilde over (y)}
y,1,8,6,x
=Cy
y,6
−r
6,8
s
8,x
. . .
{tilde over (y)}
y,1,8,1,x
=Cy
y,1
−r
1,8
s
8,x
E
y,8,8,x
=|{tilde over (y)}
y,1,8,8,x|2
{tilde over (s)}
y,8,7,x=hard decision({tilde over (y)}y,1,8,7,x/ry,7,7)
{tilde over (y)}
z,1,8,8,x
=y
z,8
−r
z,8,8
s
7,x
{tilde over (y)}
z,1,8,7,x
=y
z,7
−r
z,7,8
s
7,x
{tilde over (y)}
z,1,8,6,x
=y
z,7
−r
z,6,7
s
7,x
. . .
{tilde over (y)}
z,1,8,1,x
=y
z,1
−r
1,7
s
7,x
E
z,8,8,x
−|{tilde over (y)}
z,1,8,8,x|2
{tilde over (s)}
z,8,7,x=hard decision({tilde over (y)}z,1,8,7,x/rz,7,7) Eq. 6
A second cycle can be expressed as Eq. 7.
{tilde over (y)}
y,2,8,7,x
={tilde over (y)}
y,1,8,7,x
−r
y,7,7
{tilde over (s)}
y,8,7,x
{tilde over (y)}
y,2,8,6,x
={tilde over (y)}
y,1,8,6,x
−r
6,6
{tilde over (s)}
y,8,7,x
{tilde over (y)}
y,2,8,5,x
={tilde over (y)}
y,1,8,5,x
−r
5,7
{tilde over (s)}
y,8,7,x
. . .
{tilde over (y)}
y,2,8,1,x
={tilde over (y)}
y,1,8,1,x
−r
1,7
{tilde over (s)}
y,8,7,x
E
y,8,7,x
=E
y,8,8,x
+|{tilde over (y)}
y,2,8,7,x|2
{tilde over (s)}
y,8,6,x=hard decision({tilde over (y)}y,2,8,6,x/r6,6)
{tilde over (y)}
z,2,8,7,x
={tilde over (y)}
z,1,8,7,x
−r
z,7,7
{tilde over (s)}
z,8,7,x
{tilde over (y)}
z,2,8,6,x
={tilde over (y)}
z,1,8,6,x
−r
6,8
{tilde over (s)}
z,8,7,x
{tilde over (y)}
z,2,8,5,x
={tilde over (y)}
z,1,8,5,x
−r
5,8
{tilde over (s)}
z,8,7,x
. . .
{tilde over (y)}
z,2,8,1,x
={tilde over (y)}
z,1,8,1,x
−r
1,8
{tilde over (s)}
z,8,7,x
E
z,8,7,x
=E
z,8,8,x
+|{tilde over (y)}
z,2,8,7,x|2
{tilde over (s)}
z,8,6,x=hard decision({tilde over (y)}z,2,8,6,x/r6,6, Eq. 7
A third cycle can be expressed as Eq. 8.
{tilde over (y)}
y,3,8,6,x
={tilde over (y)}
y,2,8,6,x
−r
6,6
{tilde over (s)}
y,8,6,x
{tilde over (y)}
y,3,8,5,x
={tilde over (y)}
y,2,8,5,x
−r
5,6
{tilde over (s)}
y,8,6,x
. . .
{tilde over (y)}
y,3,8,1,x
={tilde over (y)}
y,2,8,1,x
−r
1,6
{tilde over (s)}
y,8,6,x
E
y,8,6,x
=E
y,8,7,x
+|{tilde over (y)}
y,3,8,6,x|2
{tilde over (s)}
y,8,5,x=hard decision({tilde over (y)}y,3,8,5,x/r5,5)
{tilde over (y)}
z,3,8,6,x
={tilde over (y)}
z,2,8,6,x
−r
6,6
{tilde over (s)}
z,8,6,x
{tilde over (y)}
z,3,8,5,x
={tilde over (y)}
z,2,8,5,x
−r
5,6
{tilde over (s)}
z,8,6,x
. . .
{tilde over (y)}
z,3,8,1,x
={tilde over (y)}
z,2,8,1,x
−r
1,6
{tilde over (s)}
z,8,6,x
E
z,8,6,x
=E
z,8,7,x
+|{tilde over (y)}
z,3,8,6,x|2
{tilde over (s)}
z,8,5,x=hard decision({tilde over (y)}z,3,8,5,x/r5,5) Eq. 8
The same procedure is repeated from a fourth cycle to a seventh cycle.
Then, a 8th cycle is performed like Eq. 9.
{tilde over (y)}
y,8,8,1,x
={tilde over (y)}
y,7,8,1,x
−r
1,1
{tilde over (s)}
y,8,1,x
E
y,8,1,x
=E
y,8,2,x
+|{tilde over (y)}
y,8,8,1,x|2
{tilde over (y)}
z,8,8,1,x
={tilde over (y)}
z,7,8,1,x
−r
1,1
{tilde over (s)}
z,8,1,x
E
z,8,1,x
=E
z,8,2,x
+|{tilde over (y)}
z,8,8,1,x|2 Eq. 9
Finally, an 8th symbol and a 7th symbol having a minimum value are selected at a 9th cycle as shown in Eq. 10.
min(Dy,8,1,x)=>{tilde over (s)}8
min(Dz,8,1,x)=>{tilde over (s)}7 Eq. 10
The calculation of the LLRs of the 7th symbol and the 8th symbol can be expressed as Eq. 11 in p=(b0b1b2b3). Eq. 11 shows the LLR calculation for 16 QAM.
ρk0=min(Ek,1,0,Ek,1,1,Ek,1,2,Ek,1,3,Ek,1,4,Ek,1,5,Ek,1,6,Ek,1,7)−−min(Ek,1,8,Ek,1,9,Ek,1,10,Ek,1,11,Ek,1,12,Ek,1,13,Ek,1,14,Ek,1,15)
ρk1=min(Ek,1,0,Ek,1,1,Ek,1,2,Ek,1,3,Ek,1,8,Ek,1,9,Ek,1,10,Ek,1,11)−min(Ek,1,4,Ek,1,5,Ek,1,6,Ek,1,7,Ek,1,12,Ek,1,13Ek,1,14,Ek,1,15)
ρk2=min(Ek,1,0,Ek,1,4,Ek,1,8,Ek,1,12,Ek,1,1,Ek,1,5,Ek,1,9,Ek,1,13)−min(Ek,1,2,Ek,1,6,Ek,1,10,Ek,1,14,Ek,1,3,Ek,1,1,7,Ek,1,11,EEk,1,15)
ρk3=min(Ek,1,0Ek,1,4,Ek,1,8,Ek,1,12,Ek,1,2,Ek,1,6,Ek,1,10,Ek,1,14)−min(Ek,1,1,Ek,1,5,Ek,1,9,Ek,1,13,Ek,1,3,Ek,1,7,Ek,1,11,Ek,1,15) Eq, 11
In Eq. 11, k denotes a symbol number, and k is 8 and 7 (k=7, k=8).
In the present embodiment, the multiplication is performed using a bit shifter and an adder instead of using a calculator having a complicated computation structure. That is, a shift and adder 701 performs a shift and add operation on a 5th column of an R matrix as much as symbols generated according to a symbol generation scheme of Eq. 12. For example, since ⅞ which is a symbol candidate group of 64 QAM is ‘ 4/8+ 2/8+⅛’, the shift and adder can be used to obtain a multiplying operation instead of a calculator such as a multiplier.
Referring to
As described above, a hardware structure of an MIMO receiver can become simple because a shifter and an adder are used for detecting a 8th symbol and a 7th symbol instead of using a complicated calculator such as a multiplier.
The present application contains subject matter related to Korean Patent Application No. 2007-0132492, filed in the Korean Intellectual Property Office on Dec. 17, 2007, the entire contents of which is incorporated herein by reference.
The above described method according to the present invention can be embodied as a program and stored on a computer readable recording medium. The computer readable recording medium is any data storage device that can store data which can be thereafter read by the computer system. The computer readable recording medium includes a read-only memory (ROM), a random-access memory (RAM), a CD-ROM, a floppy disk, a hard disk and an optical magnetic disk.
While the present invention has been described with respect to the specific embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.
Number | Date | Country | Kind |
---|---|---|---|
10-2007-0132492 | Dec 2007 | KR | national |