U.S. Patent
Apr. 8' 2014
US 8,693,568 B2
Sheet 1 0f 8
moH
mHH
H.
HOH
U.S. l)atent
Apr. 8' 2014
Sheet 2 0f8
US 8,693,568 B2
RECEIVE COMMON PILOT SIGNAL AND
DEDICATED PILOT SIGNAL
ESTIMATE CORRELATION FUNCTION OF COMMON
PILO? CHANNEL BASED ON COMMON PILOT
???203
ESTIMATE CORRELATION FUNCTION OF VIRTUAL
CHANNEL BASED ON CORRELATION FUNCTION OF
COMMON PILO? CHANNEL AND TRANSFORMATION
FORMULA
FIG_2
U.S. l)atent
Apr. 8' 2014
Sheet 3 0f8
US 8,693,568 B2
300
301
303
COMMON PILOT
RECEIVING
I>
ANTENNA
??'
PILOT SIGNAL
CHANNEL
RECEPTION UNIT ?'
STATISTICS
ESTIMATION UNIT
TRANSFORMATION
FORMULA
VIRTUAL CHANNEL
??>
STATISTICS
SELECTION UNIT
ESTIMATION UNIT
305
307
FIG.3
U.S. Patent
Apr. 8' 2014
Sheet 4 0f8
US 8,693,568 B2
SET INITIAL PATTERN
(dt? df):(dt0? df_0)
DETERMINE
WHETHER SYSTEM TRANSMISSION
RATE INCREASES?
TRANSMIT OPTIMUM
DEDICATED PILOT PATTERN
FIG.4
401
?
405
???407
U.S. Patent
Apr. 8' 2014
US 8,693,568 B2
Sheet 5 0f 8
?
501
503
RECEIVING
INITIAL PATTERN
MSE
ANTENNA
DETER???ATION
` COMPARISON UNIT
FINAL PATTERN
FEEDBACK UNIT
SYSTEM
TRANSMISSION
RATE COMPARISON
UNIT
507
FIG(5
505
U.S. Patent
?>
RECEIVING
ANTENNA
Apr. 8' 2014
US 8,693,568 B2
Sheet 7 0f 8
701
703
LS ESTIMATION
UNIT
COVARIANCE
CALCULATION UNIT
“
"
AMMSE
1NTERPOLATION
FILTER COEFFICIENT
AMMSE
INTER????TI
CALCULATION UNIT
705
FIG.7
707
ON
U.S. Patent
Apr. 8' 2014
Sheet 8 0f8
US 8,693,568 B2
301
COMMON PILO?
[>—— RECEIVING
ANTENNA
PILOT SIGNAL
CHANNEL
RECEPTION UNIT
STATISTICS
k
? ??303
ESTIMATION UNIT
I
*?
TRANSFORMATION
FORMULA
=
SELECTION UNIT
VIRTUAL CHANNEL
STATISTICS
'?
ESTIMATION UNIT
??L
?
501
INITIAL PATTERN
DETERMINATION
MSE
?' COMPARISON UNIT '?
UNIT
507
/
?
/???? FINAL PATTERN
FEEDBACK UNIT
?
?
`
SYSTEM
TRANSMISSION ?
RATE COMPARISON
UNIT
??L
LS ESTIMATION
??
UNIT
?
COVARIANCE
'?
? CALCULATION UNIT
701
AMMSE
INTERPOLATION
AMMSE
705'? FILTER COEFFICIENT ?' INTER????TION
CALCULATION UNIT
FIG.8
??707
US 8,693,S68 B2
1
2
METHOD AND APPARATUS FOR
ESTIMATING CHANNEL USING DEDICATED
PILOT SIGNAL IN 0FDM-BASED WIRELESS
COMMUNICATION SYSTEM
(e.g., near the Cell b0undary). It also may not be able t0
minimize the Pilot Signaling 0Verhead because it Cannot 0Pti
mally detennine the Pilot Pattern according to the channel
environment.
The use Of a dedicated Pilot signal considered in the 4G
Wireless C0mmunicati0n Systems is Very effective in 10W?
SINR environments mainly due t0 the impr0vement of trans
CROSS REFERENCE T0 RELATED
APPLICATION
mit P0Wer gain from the beamf0rming and the reducti0n Of
the Pilot signaling 0Verhead. H0Wever, it may not be easy t0
This application is a continuati0n-in-Pan of PCT Interna
tional Applicati0n N0. PCT/KR2010/00840l, Hled on NOV'
25, 2010, Which Claimed PriOth t0 Korean Apphcati0n NO.
estimate the statistical Characteristics Of the Vinual Channel
because the dedicated Pi10t signal is allocated t0 a SPeCiHC
10-2009-0114509, med on NOV. 25, 2009, the entire disc10
user using a small amount 0fresource. AS a C0nsequence, the
SuTes Of Which are inc0rporated by reference as a Pan Of this
use Of statistical estimati0n techniques (e.g., the minimum
mean squared estimati0n (MMSE)) may not be applicable t0
the Channel estimati0n With the use Of dedicated Pilot signal,
applicati0n.
BACKGROUND 0F THE INVENTION
Which may limit the exploitati0n Ofthe dedicated Pilot signal
in the channel estimation.
1. Field of the Invention
The Present invention relates t0 a method and apparatus for
Channel estimati0n using a dedicated Pilot Signal in an
SUMMARY 0F THE INVENTION
20
onhogona1 frequency diVisi0n multiplexing (0FDM)-based
In order t0 0Verc0me the ab0Ve-described limitati0ns in the
Wireless C0mmunicati0n system using multi-antenna trans
use 0fdedicated Pilot signal, the Present invention Pr0poses a
method and apparatus Which Can estimate the statistical Char
mission techniques.
2. Deschpti0n Of the Related Art
AI1 0FDM Wireless C0mmunicati0n system With multi
acteristics of the Vinual channel, generated by the transmit
25
input multi-0utput (MIM()) techniques can increase the chan
nel Capacity using a spatial muhiplexing technique and
impr0Ve the reliability Of data transmissi0n using a diversity
technique. Accurate Channel estimati0n at the receiver is
indispensable t0 maximize the Perf0nnance Of a MIMO
OFDM-based Wireless C0mmunicati0n system. The channel
30
Charactehstics Of the VilTual Channel, While improving the
Pilot transmit P0Wer and the reducti0n 0fpilot Signaling 0Ver
onhog0nally allocated t0 eacl1transmit antenna in the down
link Of a MIMO OFDM-based Wireless C0mmunicati0n sys
head.
35
signaling 0Verhead because the amount Of C0mmon Pi10t sig
nal increases in linear Prop0rtion to the number of transmit
antennas. Ifthe MIMO System uses the same amount of Pilot
signaling 0Verhead as the Single antenna system, it Can use
reduced Pilot signal for each antenna, yielding P00r Channel
40
estimati0n (i.e., increase Of the mean square error (MSE) in
channel estimati0n) in 10W signa]-to-interference Plus n0ise
P0Wer rati0 (SINR) Channel environments.
In order t0 alleviate this Pr0blem, the f0urth-generati0n
(4G) Wireless C0mmunicati0n Systems, Such as IEEE
be Possible t0 noticeably impr0Ve the Channel estimati0n
accuTacy in 10W SINR environments by employing an 0Pti
mum channe1 estimati0n technique With the use Of statistical
inf0rmati0n is 0?en estimated using C0mmon Pilot Signal
tem. H0Wever, this technique may Suffer from high Pilot
beamf0rming, using the statistical Characteristics 0fthe C0m
mon Pilot channel, detennine the dedicated Pilot Patten1 t0
maximize the system transmissi0n rate, and estimate the Vir
tual channel from the dedicated Pilot signa1. As a result, it can
45
802.16m and 3GPP LTE, Consider the use Of a dedicated (Or
In order t0 acc0mplish the said obj ect, the Present invention
Pr0viding a method and apparatus for the Channel estimati0n
using dedicated Pilot signal in an 0FDM-based Wireless com
municati0n system With transmit beamf0nning includes the
steP and the unit for the estimati0n Of the statistical Charac
telistics of the Vinual channel, Which is generated by the
transmit beamf0rming, using the statistical Characteristics Of
the common Pilot channel; the steP and the unit for the deter
minati0n Of the dedicated Pilot signal Pattem using the esti
mated statistical Characte? stics 0fthe Virtual Channel; and the
steP and the unit for the channe1 estimati0n using the dedi
Cated Pilot signal.
user SPeCiHC) Pilot signal. In an MIMO System Which
employs a transmit beamforming technique, the data signal is
transmitted through a Vinual Channel Which is generated by
muhiplying the Channel With the beam Weight Vect0r for the
transmit beamf0rming. The dedicated Pilot Signal is also
BRIEF DESCRIPTION 0F THE DRAWINGS
50
channel infonnati0n using a dedicated Pilot signal in a Wire
less C0mmunicati0n System, acc0rding t0 an emb0diment Of
transmitted by means 0ftransmit beamf0rming With the same
beam Weight identical as that Of data Signal. The use Of dedi
Cated Pilot Signal is effective in 10W-SINR environments (e.g"
near the cell boundary) mainly because Of the reducti0n Of
FIG. 1 is a diagram Showing the schematic Con?gu?atiOn Of
a transmitter and a receiver Which adaptively estimate the
the Present inventi0n;
55
FIG. 2 is a diagram Showing a method Of estimating the
Pilot signaling 0Verhead and the effect Of beamf0rming gain
statistical Charactelistics Of a Vinual Channel in a Wireless
as Well.
C0mmunicati0n System t0 Which transmit beamf0nning tech
niques haVe been applied, according t0 an emb0diment ofthe
The Statistical Characteristics Of the Virtual Channel are
different from those 0findividual antenna Channel. More0ver,
the amount 0fresource allocated t0 the dedicated Pilot signal
Present inventi0n;
60
the Statistical Charactelistics Of the Virtual Channel from the
received dedicated Pilot signal. C0nventi0nal technologies
often emp10ys a linear interp01ati0n (LI) technique because Of
the simplicity (i.e., it does n0t require the Statistical Charac
teristics of the Vinual Channel). H0Wever, the LI technique
may be Vulnerable t0 the Presence Of interference and n0ise
FIG. 3 is a diagram Showing the detailed C0anurati0n Of
the correlation function estimation unit included in the unit to
estimate statistical characteristics of the Vinual channel of
is Very small. AS a C0nsequence, it may not be easy t0 estimate
FIG. 1;
65
FIG. 4 is a diagram Showing the method for the detenni
nation of dedicated Pilot Pattem in a Wireless c0mmunication
system With transmit beamf0nning, according t0 an emb0di
ment Of the Present invention;
US 8,693,S68 B2
3
4
FIG. 5 is a diagram Showing detailed Con?guratiOn Of the
dedicated Pilot Pattern detenninati0n unit included in the unit
for estimating statistical characteristics ofthe Vinual channel
Of FIG. 1;
FIG. 6 is a diagram showing the AMMSE interp01ation
E{'} is the expectation 0Perator, and the supersclipt * den0tes
the C0mplex C0njugate 0Perat0r. The C0rrelati0n functi0n Of
the Virtual Channel Can be deHned by the f0110wing Equation
4;
S
Pr0cess for the estimation Of Vinual Channel in a Wireless
communicati0n system With transmit beamforming accord
FIG. 1 is a diagram Showing the schematic Con?gu?atiOn Of
ing t0 an emb0diment Of the Present invention;
FIG. 7 is a diagram Showing the Con?gu?atiOn Of the
AMMSE interp01ati0n unit for the estimation 0fvinual Chan
nel as an example 0fthe Virtual Channel interp01ati0n unit 132
0f FIG. 1; and
FIG. 8 is a diagram showing the 0Verall Con?guratiOn Ofthe
a transceiver Which estimates the Channel using dedicated
Pilot signal in a Wireless C0mmunicati0n system, according t0
an emb0diment of the Present invention.
The transmitter 101 includes a signal transmission unit 111
and a beamforming unit 112. The transmission unit 111 trans
mits data and dedicated Pilot signal having a unique Pattem.
The beamf0rming unit 112 generates transmit signal by
applying the beam Weight t0 the data and dedicated Pilot
signal, and transmits it through Nr transmit antennas.
channel estimator in a receiver of a Wireless C0mmunicati0n
system With transmit beamf0rming, according t0 an emb0di
ment of the Present invention.
The receiver 103 includes an estimati0n unit 113 and an
DESCRIPTION 0F THE PREFERRED
EMBODIMENTS
interp01ati0n unit 114. The estimati0n unit 113 estimates the
20
Preferred emb0diments Of the Present invention Will be
descIibed in What follows With reference t0 the accompany
Channel by means Of amne MMSE based on the estimated
statistical Characteristics Of the Vinual Channel.
ing drawings. In the f0110wing desclipti0n, detailed descrip
tions of known ?JnCtiOnS and constructi0ns Which have been
deemed t0 make the gist Ofthe Present invention Vague Will be
0mitted.
A method and apparatus according t0 emb0diments Of the
Present invention Will be descIibed be10W Which, in an
0FDM-based Wireless C0mmunicati0n system With multi
antenna techniques (e.g" C0herent beamf0nning (CBF) Or
eigen-beamf0nning (EBF) technique), estimates the Statisti
Cal CharacteIistics Of Virtual Channel generated by multi-an
25
30
tenna transmissi0n techniques, using the statistical Character
istics Of C0mmon Pilot Channel; detennines the dedicated
Pilot Pattern maximizing the system transmission rate using
35
the estimated statistical Characteristics 0fthe Virtual Channel,
and estimates the Virtual Channel from the dedicated Pilot
Pattem.
A MEMO OFDM-based Wireless C0mmunication system
using dedicated Pilot Signal With Nrtransmit antennas Will be
Considered. Let P"(I1,k) be the dedicated Pilot signal allocated
t0 the n-th 0FDM Symb01 and the k-th Subcarrier in the
Wireless C0mmunicati0n system. When the Wireless commu
nication system transmits the signal by means of beamform
ing With an (Nz??1)-unit norm beam Weight Vector, the
statistical Charactehstics Of Virtual Channel generated by the
beamf0rming unit 112. The interpolati0n unit 132 estimates
the Virtual Channel by interp01ating the estimated Vinual
40
FIG. 2 is a diagram showing the Pr0cess for the estimation
the statistical Characteristics Of the Vinual Channel generated
by the transmit beamf0rming, according t0 an emb0diment Of
the Present invention.
At steP 201, the receiver receives C0mmon Pilot signal and
dedicated Pilot signal as Well. At steP 203, the receiver esti
mates the C0rrelati0n functi0n Of the C0mmon Pilot Channel
from the received Common Pilot signal, by Equation 3 . At steP
205, the receiver estimates the C0rrelati0n ?JnCtiOn Of the
Virtual Channel from the C0rrelation f]?ncti0n Of the Common
Pilot Channel, estimated at steP 203.
The method for the estimation Of the correlati0n ?JnCtiOn
Of the Virtual channel depends on the transmit beamfonning
technique. Ifthe CBF technique according t0 an emb0diment
ofthe Present invention is used, the C0rrelation function ofthe
Virtual Channel Can be estimated using the f0110wing Equation
5
(S)
45
received Pilot Signal Can be represented by Equation 1:
Where H(n,k) is a (1XNT)-unit norm channe1 Vector compris
ing Zer0-mean independently and identicauy distributed
50
(i.i.d.) C0mplex Gaussian random Variables With the same
Variance OH2, and N(n,k) is additive White Gaussian noise
domain, OH2 and OE2 are respectively the VaIiance Of the
Channel and the beam Weight Vect0r, Nr is the number Of
(AWGN) With Valiance ON2. Here, each element Of H(n,k)
transmit antennas, l?(~) is the gamma function, and p is the
n0rmalized correlati0n function 0fthe common Pilot channel,
represents common Pilot Channel and the Vinual Channel due
t0 the beamf0nning Can be represented by the f0110wing
Equation 2:
Where ?n and ?k are respectively the 0FDM Symb01 interval
in the time d0main and the subcarIier interval in the frequency
55
Which is represented by the f0110wing Equation 6:
Let Hz(n'k) be the i-th element ofthe Channel Vector H(I1,k).
Assuming that the Channel is a Wide sense stationary Pr0cess,
the C0rrelati0n ?JnCtiOn Of the C0mmon Pilot Channel Can be
60
If the EBF technique according t0 an0ther emb0diment of
the Present invention is used, the correlati0n ?JnCtiOn Of the
Virtual Channel Can be estimated using the f0110wing Equation
deHned by the fonowing Equation 3;
65
Where ?n and ?k are the 0FDM Symb01 interval in the time
d0main and the subcarIier interval in the frequency domain,
7
US 8,693,S68 B2
8
7
At steP 601, the Virtual Channel is estimated from the
received dedicated Pilot signal by means of the least square
Compa?ng the average MSE With the use of t?VO Pilot
Pattems (dr+?dr,d?? and (dr,d/+?d??, the neW Pilot Pattem
(d""gw,d?"?) is selected by the f0110wing Equation 202
(LS) method, acc0rding t0 Equation 17.
At steP 603, the crOSS-C0Valiance Vector and the aut0
C0Variance matlix are Calculated using the statistical Charac
telistics 0fthe Virtual Channel estimated at steP 205 0f FIG. 2
and the 0Ptimum dedicated Pilot Pattem detennined at steP
407 0f FIG. 4.
At steP 405, the system transmissi0n rate With the use Of
At step 603, When a dedicated Pilot signal is transmitted at
the n'-th 0FDM Symb01 and the k'-th SubcarIier using dedi
Cated Pi10tpattem (dr'0P”d??,) determined at steP 407 0fFIG.
4, the CrOSS-C0Valiance Vector and the aut0-C0Variance matlix
dedicated Pilot Pattem (dpd'? and (d""gw,d?"?) Selected at
steP 403 is C0mpared by the f0110wing Equati0n 21. If the
deHned by Equation 10 Can be Calculated by the fonowing
for the estimation of the virtual channel in resource region S
system transmissi0n rate is increased With the use Of the neW
Pi10tpattem, retu?nS t0 SteP 403 While replacing the dedicated
Pilot Pattem With the neW dedicated Pilot Pattem and 0ther
Wise, Pr0ceeds t0 SteP 407 Without Change Of the dedicated
Pilot Pattem?
20
pz)z?
Where T(d”d? is the system transmissi0n rate taking int0
account of the signaling 0Verhead for the dedicated Pilot
At steP 605, from the cross-C0VaIiance Vector and the aut0
COVariance matlix calculated by Equati0ns 23 and 24, the taP
coemcient Ofthe AMMSE interp01ati0n mter minimizing the
MSE is detennined by the f0110wing Equati0n 252
25
At steP 607, the Virtual channel in resource region s is
estimated by means of AMMES interp01ati0n With the taP
Signaling and the MSE, giVen by Equation 22;
Coe??Cient determined at steP 605, by Equation 26:
30
FIG. 7 is a diagram showing the detailed C0anurati0n Of
the AMMSE interpolation unit as an example of the virtual
Channel interp01ati0n unit 132 0f FIG. 1.
The Virtual Channel AMMSE interp01ati0n unit 700
Here Y is the average SNR Value.
At steP 407, the 0Ptimum dedicated Pilot Pattem
35
includes an LS estimati0n unit 7 01, a C0Variance Calculati0n
(dr'0Pr,d?oP,) is transmined t0 the transmitter, Which is deter
unit 703, an AMMSE interpolation Hlter coechient calcula
mined by repeatedly Pr0cessing StePs 403 and 405.
tion unit 7 05, and an AMMSE interpolation unit 7 07 . The
FIG. 5 is a diagram Showing the detailed C0anurati0n Of
the dedicated Pilot Pattem determinati0n unit included in the
unit that estimates the statistical charactelistics of the Vinual
received dedicated Pilot signal is used to estimate the Vinual
Channel by means of the LS method at the LS estimati0n unit
40
Channel Of FIG. 1.
The C0Variance Calculati0n unit 703 Calculates the CrOSS
C0Variance Vector and aut0-C0Variance matlix used for the
The dedicated Pi10tpattem detenninati0n unit 500 includes
aninitia1 Pattern detenninati0n unit 501, an MSE C0mpaHson
unit 503, a system transmission rate compalison unit 505, and
a Hnal Pattem feedback unit 507.
The initial Pattern determinati0n unit 501 determines the
initial dedicated Pi10tpattem by Equati0n 9. The MSE C0m
Parison unit 503 Selects a Pi10tpatternyielding a smaller MSE
With the use Of t?VO Pilot Pattenls; One Whose Pilot spacing is
increased by One unit in the time d0main and the 0ther one
7 01, by Equati0n 17?
AMMSE interp01ati0n by Equati0ns 23 and 24, using the
Statistical Charactelistics Of the Vinual Channel estimated at
45
steP 205 and the 0Ptimum dedicated Pi10tpattem determined
at steP 407 .
The AMMSE interp01ati0n Hlter coechient calculati0n
unit 7 05 determines the coechient of the AMMSE interpo
1ation Hlter using the results ofthe C0Variance calculation unit
Whose Pilot spacing is increased by One unit in the frequency
domain, acc0rding t0 Equation 20.
703, by Equation 25. The AMMSE interpolation unit 707
interp01ates the Virtual Channel using the coemcient Of the
AMMSE interpolation Hlter detennined by the AMMSE
The system transmissi0n rate compalison unit 505 Com
Pares the system transmission rate With the use ofthe existing
tion 26.
Pilot Patten1 and neW Pilot Patten1 detennined by Equation
50
interp01ation Hlter coechient calculation unit 705, by Equa
55
FIG. 8 is a diagram showing the 0Verall Con?gu?atiOn ofthe
21 . Ifthe system transmission rate is increased, it replaces the
receiver in a Wireless C0mmunicati0n system With transmit
Pilot Pattem With the neW Pilot Pattem and transfers it t0 the
beamforming, according to an embodiment of the Present
invention.
The receiver includes the unit for the estimati0n Of Statis
tical Characteristics Of the Vinual Channel, including the C0r
relati0n functi0n estimati0n unit 300 0f FIG. 3 and the 0Pti
mum dedicated Pi10tpattem determinati0n unit 500 0fFIG. 5,
MSE C0mparison unit 503, and repeats the Previous Pr0cess.
If the system transmissi0n rate is not increased, it uses the
existing Pi10tpattem as the 0Ptimum One and transfers it t0 the
60
Hnal Pattem feedback unit 507 . The Hnal Pattem feedback
unit 507 transfers the 0Ptimum dedicated Pi10tpatten1t0 the
transmitter.
FIG. 6 is a diagram Showing a method 0fAMMSE inter
Polation for the estimation ofthe Viltual channel in a Wireless
C0mmunicati0n system With transmit beamf0nning, accord
ing t0 an emb0diment Of the Present inventi0n.
and the AMMSE interpolati0n unit 7 00 0f FIG. 7 .
Common Pilot signal received from the Pilot signal recep
65
tion unit 301 is used by the C0mmon Pilot Channel Statistics
estimati0n unit 303 t0 estimate the C0rrelati0n function 0fthe
C0mmon Pilot Channel.
US 8,693,S68 B2
14
13
12. The apparatus Of Claim 11, Wherein the Virtual Channel
statistical Charactehstics estimati0n unit estimates statistical
characteIistics of the Virtual Channel generated by a multi
antenna transmissi0n technique using the estimated statistical
Charactehstics Of C0mmon Pi10tchannel.
13. The apparatus Of Claim 12, Wherein if a CBF transmis
sion technique is used, a correlati0n ?JnCtiOn Of the Vinual
Channel is estimated by a f0110wing Equation 5;
Where Y is an average SNR, ?MSE2(dr,d/) is the MSE by
AMMSE interp01ati0n With use 0fdedicated Pi10tpattem and
(d"d??, and me and OHW2 are an average gain and a VaIiance Of
the Vinual channel, respectively, and if a CBF or EBF multi
antenna technique is employed, the Variance Of the Vinual
Channel is Calculated by a f0110wing Equation 13 0r 14,
respectively,
Where An and Ak are respectively the 0FDM symbol interval
in a time domain and a subcarrier interval in a frequency
domain, on and OE2 are respectively a Variance 0fthe Chan
nel and the beam Weight Vect0r, Nr is a number Of transmit
antennas, r(') is a gatnma ?Jnction, and p is a normahzed
C0rrelation f]?ncti0n Of the Common Pilot Channel.
14. The apparatus Of Claim 12, Wherein if an EBF trans
mission technique is used, the correlati0n ?JnCtiOn Of the
Virtual Channel is estimated by a f0110wing Equation 7;
and a C0rresp0nding average Channel gain Can be Calculated
by a f0110wing Equation 18 0r 19, respectively,
(l9)
30
Where An and Ak are respectively the 0FDM symbol interval
in a time domain and a subcarlier interVal in the frequency
17. The apparatus Of Claim 11, Wherein a Pr0cess Of deter
domain, p is a n0rmahzed C0rrelati0n ?JnCtiOn Ofthe C0mmon
mining the 0Ptimum dedicated Pilot Pattem by repeating a
Pilot Channel, and ??? is a maximum eigenvalue Of a SPatial
C0rrelation matlix Of the Channel, 0btained by eigenvalue
Process of minimizing the MSE With respect to the Pilot
signal density and a Pr0cess 0fmaximizing the system trans
mission rate in considerati0n Of the Pilot signal signaling
0Verhead and Channel estimati0n MSE is Perfonned by
sequentially repeated Processing as in a f0110wing
dec0mpositi0n.
15. The apparatus Of Claim 11, Wherein the Pr0cess Of
minimizing the MSE With respect t0 the Pilot signal density
selects a dedicated Pilot Pattem d""?, (i??…?W yielding a
smaller MSE from t?VO dedicated Pilot Patterns Whose Pilot
Signaling SPace is increased by ?dr in a time domain Or by ?d/
Equation Z7:
in a frequency domain, as in a f0110wing Equation 20:
45
50
Where dr is an 0FDM Symbol interval of the dedicated Pilot
Pattem in the time domain, (i?? a SubcarIier interval Of the
dedicated Pi10tpatterninthe frequency domain, ?dr is a erd
unit for spacing at the dedicated Pilot signal in the time
domain, ?d/is a erd unit for spacing of the dedicated Pilot
Finalization
signal in the frequency domain, and ?^?'SE2(d'+?d”d?? and
…MSE2(d”d/+?d? are the MSE by AMMSE interp01ati0n With
use Of dedicated Pilot Pattem (d'+?d”d? and (d"d/+?d?
respectively.
16. The apparatus Of Claim 11, Wherein the Pr0cess Of
maximizing the system transmissi0n rate in considerati0n Of
the Pilot Signaling 0Verhead and Channel estimati0n MSE
updates the dedicated Pilot Pattem SO as t0 increase a trans
60
Where dr is an 0FDM Symbol interval of the dedicated Pilot
Pattem in a time domain, d/ is a subcarrier interval of the
dedicated Pi10tpattern in a frequency domain, ?dr is a erd
unit for spacing of the dedicated Pilot signal in the time
domain, ?d/is a erd unit for spacing of the dedicated Pilot
signal iI1the frequency domain, (d"o,d?o) is an initial dedi
Cated Pi10tpattern, (dr'"gw,d?"gW) is an updated dedicated Pilot
mission rate Of the dedicated Pilot Pattem 0btained from the
dedicated Pilot signal Pattem detenninati0n unit, as in f0HOW
Patten1 Which minimizes the MSE With respect to the Pilot
ing Equations 21 and 22;
tem Hnany detennined.
density, and (dr'0P”d??') is the 0Ptimum dedicated Pi10tpat
US 8,693,S68 B2
15
16
18. The apparatus ofclaim 11, Wherein the transmission of
the 0Ptimum dedicated Pilot Pattem to the transmitter com
Plises a n0tiHcati0n Of the 0Ptimum dedicated Pilot Pattem
determined by the optimum dedicated Pilot Pattem detenni
nation unit to the transmitter and the transmission of dedi
cated Pilot signal by the transmitter according to the optimum
dedicated Pilot Pattem.
19. The apparatus of claim 11, Wherein the Virtual channel
interpolati0n unit estimates the Vinual Channel, generated by
a beaInfonning technique, using the received dedicated Pilot
0
signal and then estimates a whole virtual channel by interpo
lating the estimated Vinual channel by AMMSE interpola
tion.
20. The apparatus of claim 19, Wherein the estimation of
the whole virtual channel by interpolating the estimated vir
tual Channel by AMMSE interp01ati0n is Perf0nned using an
AMMSE interp01ati0n technique Which C0mpensates for an
average gain Ofthe Virtual Channel, as in a fonowing Equation
S
262
20
where ^W is the tap coechient of an AMMSE interpolation
Hlter, H?(d??”d??') is the Vinual Channel estimated from
the received dedicated Pilot signal, and me is the average
gain of the Virtual channel.
*
*
*
*
*
25
USOO8693568B2
(12) United States Patent
(10) Patent N0.:
Lee et al.
(54)
(45) l)ate 0f Patent:
METHOD AND APPARATUS FOR
(56)
ESTIMATING CHANNEL USING DEDICATED
PILOT SIGNAL IN 0FDM-BASED WIRELESS
C0MMUNICATI0N SYSTEM
(75) Inventors: Y0ng-Hwan Lee, Seoul (KR); Han-Jun
Park, Seoul (KR); Keon-W00k Lee,
Seoul (KR)
N0tice;
Subject t0 any disclaimer, the term Ofthis
Patent is extended or adjusted under 35
U.S.C. 154(b) by 0 days.
ZOO8/0153446 Al
2008/0225993 Al
2009/004IISO A1*
6/2008 Isaac et al'
9/2008 Malladj et al'
2/2009
Tsai et al'
"""""""""" " 37S/267
KR
1020090ll9995 A
Wo
Wo 2006/0882S2
Wo
Wo 2009/094135 A2
Wo PCT/KR2010/00840l
Wo
Wo 201 l/06S764 A2
Wo
Wo 201 l/06S764 A3
3/20ll
8/2006
7/2009
ll/2009
3/20ll
3/20ll
* cited by examiner
Pri0r Publicati0n Data
US 2013/OOS4177 A1
U.S. PATENT DOCUMENTS
Hongzhong Yan at a1" “Dedicated Reference Signal Based Channel
Estimati0n using Weighted Averaging Scheme in 0FDM Systems", 5
Pages, IEEE 2010, 0ttawa, Ontari0, Canada,
May 24, 2012
(65)
References Cited
OTHER PUBLICATIONS
(21) APP1.N0.: 13/479,939
(22) Filed:
Apr. 8' 2014
FOREIGN PATENT DOCUMENTS
(73) Assignee: SNU R&DB F0undati0n,Seou1(KR)
(*)
US 8,693,568 B2
Feb. 7, 2013
(57)
Related U_S. Apphcati0n Data
(63) C0ntinuati0n-in-Pan
Of
ABSTRACT
The invention relates to a method for channel estimation
apphcati0n
NO.
PCT/KR2010/ 008401 , Hled on NOV. 25, 2010.
using a dedicated Pilot signal in an 0FDM-based communi
cation system With multi-antenna transmission techniques.
The receiver estimates the statistical charactenstics of a vir
tual channel generated by beaInfonning by exploiting the
(30)
F0reign Apphcati0n Pri0rity Data
NOV.25,2009
statistica1 charactelistics of common Pilot channel, deter
(KR) ...................... ..10-2OO9-Oll4509
mum Pattem by means 0fAMMSE interpolation. The inven
tion minimizes the channel estimation error by exploiting the
(51) Int_Cl_
(2006'Ol)
??? 7/?2
(52) U_S.Cl_
USPC
(58)
mines the optimum dedicated Pilot Pattem, and estimates the
Channel from dedicated Pilot signal transmitted in an 0Pti
......... .. 375/267;375/260…375/299;375/347…
statistical Characteristics 0fthe Virtual Channel, and 0Ptimany
determines the dedicated Pilot Pattem according to the 0Pera
tion enviromnent to maximize the transmission Performance
in tenns Of the Pilot signaling 0Verhead and the Channel
375/349
estimation elTor. In Panicular, the invention is Very effective
USPC ........................ .. 375/267, 260, 299, 347, 349
in 10W signa]-to-interference Plus noise Power ratio (SINR)
0Perati0n environments.
20 Claims, 8 Drawing Sheets
Field 0f Classi?cati0n Search
See applicati0n me for C0mplete search hist0ry.
FREQUENCY AXIS
L
111
112
113
114
SIGNAL
TRANSM?SSION UNf?
BEAMFORMING UNTT
ESHMAHON UNr?
INTERPOLATION UNT?
TRANSMr?ER
1?1
?? l
RECEIVER
103
?