US 20060212774Al
(19) United States
(12) Patent Application Publication (10) Pub. No.: US 2006/0212774 A1
Lee et al.
(43) Pub. Date:
(54) APPARATUS AND METHOD FOR
(30)
Sep. 21, 2006
Foreign Application Priority Data
TRANSMISSION WHICH ENCODING A
MESSAGE WITH SPACE-TIME TUBO CODE
Mar. 8, 2005
USING FEEDBACK BIT IN MOBILE
COMMUNICATION SYSTEM
(KR) .......................... .. 10-2005-0019227
Publication Classi?cation
(75) Inventors: Jae Hong Lee, Seoul (KR); Chi Hoon
(51)
Int. Cl.
H03M 13/00
(52)
U.S.C1. ............................................................ ..714/755
Yoo, Anyang-si (KR)
(2006.01)
Correspondence Address:
MCDERMOTT WILL & EMERY LLP
(57)
600 13TH STREET, N.W.
WASHINGTON, DC 20005-3096 (US)
ABSTRACT
An apparatus and a method for transmission encoding a
message With space-time turbo code using feedback infor
mation of the channel gain or the phase in digital mobile
(73) Assignee: SEOUL NATIONAL UNIVERSITY
INDUSTRY FOUNDATION
_
_
_
_
_
communication system having a plurality of transmit anten
(21) App1_ NO;
11/368,609
(22)
Mar. 7, 2006
Filed:
nas are disclosed. The space-time turbo code using the
feedback scheme has better performance than that of the
conventional.
Input
: Systematlc
Bits
BI ts
1st BS0
Encoder
\
110 ~
Even-Odd
Inter Ieaver
121
2st HSC
Encoder
\
/\
punctu'er
r
\J\
150
131
Puncturer
Del nter leaver
\
122
\
132
_
p
140
Punctured
Parity Blts
Patent Application Publication Sep. 21, 2006 Sheet 1 0f 5
US 2006/0212774 A1
FIG. 1
Input
I
Bits
_ systematlc
"
1st RSO
Encoder
Even-Odd
/\
P“"°“"°'
\
110.\_
‘
_
Y
121
_
lnterleaver
v\
‘
.
131
._
_
Bits
Punctured
Parity Bits
150
_
_
Puncturer
\
Del Mar leaver
\
122
»
\
132
'
140
FIG. 2
I
pNmbeairjl‘z?e!dty
l
0.0-
'
0.5
.
weightingv factor- ljaf‘z ‘
15.101
Patent Application Publication Sep. 21, 2006 Sheet 2 0f 5
US 2006/0212774 A1
FIG. 3
100
200
2
lnput__
‘
300
\Alternator
_,
,
/
I
~
501
Systematic
B“
Bits
\
7
.
.
/
Space-Time
‘
Turbo Encoder
3|
|
M3332,
Punctured
-
T\502
'
Parity Bit
T
Feedback
Bits
FIG. 4
(
Stat
)
Encode a message with
space-time turbo code
i
~ $110
.
Receive a feedback bit ref lect ing the ~ S120
channel gain from receive terminal
l
Select a transmit antenna wi th larger _
channel gain according to the feedback bit
N 8130
T
Transmit a systemat ic bit the selected antenna ‘N 8140
and a punctured par i ty bit through another antenna
(1i)
Patent Application Publication Sep. 21, 2006 Sheet 3 0f 5
US 2006/0212774 A1
FIG. 5
.
‘Constellation
‘m:
Rotation
1/-J'.' :\
Re
'-
q.
{
D. Iransmiited symbols
Mm
./
> ‘i
i
iReceivedisymhdls
_i
.
,><->~
.*
;f
- ‘
Re
k,_, J
x
n
FIG. 6
100
2
mput
300
1
401‘ \
‘ 7\5o1
Systemat lc
Bits __.._
x
Bit
5
I x
Space-Time
slgnal
Tur b0 Enc0d er
Mapper
Punctured
.
/"
V\
x
_
502
K
Parity an
X
.
\
\
402
Feedback
Bits
Patent Application Publication Sep. 21, 2006 Sheet 4 0f 5
US 2006/0212774 A1
FIG. 7
(
Stat '
)
Encode a message with
spacert Ime turbo code
i
~ $210
.. _
Receive a feedback bit ref iect ing
the phase di fference of the
~ $220
channel gain from receive terminal
Rotate the constel lat ion corresponding to ,the systemait ic bit
and the punctured par ity bit respect iveiy so ‘that phase
~ $230
di fference of the channel gain according to feedback bit is largest
FIG. 8
100
1
'
200\ Alternator
Systematic
"9"‘ _Bits
300
)
4m\
x
an
‘
\
\
>
‘
\ ,q
Space-Time
Turbo Encoder
Egg:
a
x
I
\
Punctured
\
Parity Bit
x
\
.
Feedback
Bits
a
402
Patent Application Publication Sep. 21, 2006 Sheet 5 0f 5
US 2006/0212774 A1
FIG. 9
.....J_.
.
..
BER
b
2
4
6_
8
10
EblNO
FIG. 10
BER
.12
14
16.
Sep. 21, 2006
US 2006/0212774 A1
APPARATUS AND METHOD FOR TRANSMISSION
WHICH ENCODING A MESSAGE WITH
SPACE-TIME TUBO CODE USING FEEDBACK BIT
IN MOBILE COMMUNICATION SYSTEM
CROSS-REFERENCE TO RELATED
APPLICATIONS
[0001] This application claims priority to and the bene?t
of Korean Patent Application No. 10-2005-0019227, ?led
Mar. 8, 2005, the contents of Which are hereby incorporated
herein by reference in their entirety.
BACKGROUND OF THE INVENTION
[0002]
1. Field of the Invention
[0003] The present invention relates to an apparatus and a
method for transmission Which encoding a message With
space-time turbo code using feedback information of the
channel gain or the phase in digital mobile communication
system having a plurality of transmit antennas.
turbo code and generating a systematic bit and a punctured
parity bit; receiving a feedback bit re?ecting information of
the channel gain of the plurality of transmit antennas from
receive antenna; selecting a transmit antenna With the largest
channel gain of the plurality of transmit antennas according
to the feedback bit; and transmitting the systematic bit
through the selected transmit antenna and the punctured
parity bit through one of the other antennas.
[0011] In another embodiment, a method for transmission
encoding a message With space-time turbo code in digital
mobile communication system having a plurality of transmit
antennas, comprising: encoding the message for communi
cation With space-time turbo code and generating a system
atic bit and a punctured parity bit; receiving a feedback bit
re?ecting phase difference information of the channel gain
of the plurality of transmit antennas from receive antenna;
and rotating a constellation corresponding to the systematic
bit and the punctured parity bit respectively so that phase
difference of the channel gain according to a feedback bit
Would be at its largest.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] 2. Description of the Related Art
[0005] Recently, the space-time turbo code, a combination
of the space-time code and the turbo code, has been Widely
studied. The space-time turbo code provides the robust error
correcting performance over the various time-varying chan
nels as it has both the spatial diversity gain of the space-time
code and the poWerful coding gain of the turbo code.
[0006]
In the most researches for the space-time turbo
code, assume that the transmitter does not knoW the Channel
State Information (CSI). If the transmitter has knoWledge of
the CSI by using a proper feedback scheme, the performance
of the space-time turbo code can be improved. The diagonal
Weighting scheme With quantized feedback information has
been proposed for the space-time block code to improve its
performance. HoWever, the diagonal Weighting scheme is
not applicable for the space-time turbo code as it does not
distinguish betWeen the systematic bits and parity bits.
SUMMARY OF THE INVENTION
[0007] The present invention provides feedback schemes
Which can improve the performance of a space-time turbo
code With a plurality of transmit antennas by using the
quantized feedback. One is an antenna altering (AA) scheme
in Which the systematic bits are alWays transmitted through
the antenna With larger channel gain. The other is a quan
tized phase feedback (QPF) scheme Which rotates the signal
constellation according to the feedback information of the
channel phase.
[0008] The space-time turbo code using the feedback
scheme of the present invention has better performance than
that of the conventional invention.
[0009]
The purpose of the present invention provides an
apparatus and a method for transmission encoding a mes
sage With space-time turbo code using feedback information
of the channel gain or the phase in digital mobile commu
nication system having a plurality of transmit antennas.
[0010] A method for transmission encoding a message
With space-time turbo code in digital mobile communication
system having a plurality of transmit antennas, comprising:
encoding the message for communication With space-time
[0012] The accompanying draWings, together With the
speci?cation, illustrate certain exemplary embodiments of
the present invention and serve to explain the principles of
the present invention.
[0013] FIG. 1 is a block diagram illustrating an encoder of
the space-time turbo code With parallel concatenation of tWo
recursive systematic convolutional (RSC) encoders sepa
rated by an even-odd interleaver.
[0014]
FIG. 2 is a diagram illustrating a normalized BER
of the space-time turbo code With the diagonal Weighting
scheme.
[0015] FIG. 3 is a diagram illustrating a transmitter of the
space-time turbo code With an antenna altering scheme.
[0016] FIG. 4 is a How chart encoding the space-time
turbo code With the antenna altering scheme.
[0017] FIG. 5 is a diagram illustrating a constellation of
the transmitted and received symbols in a noiseless fading
channel.
[0018]
FIG. 6 is a diagram illustrating a transmitter of the
space-time turbo code With a quantized phase feedback.
[0019] FIG. 7 is a How chart encoding the space-time
turbo code With the quantized phase feedback.
[0020] FIG. 8 is a diagram illustrating a transmitter of the
space-time turbo code With a combined scheme.
[0021] FIG. 9 is a graph illustrating a performance of the
BPSK space-time turbo codes With feedback scheme in
accordance With an exemplary embodiment of the present
invention in a quasi-static Rayleigh fading.
[0022] FIG. 10 is a graph illustrating a performance of the
QPSK space-time turbo codes With feedback scheme in
accordance With an exemplary embodiment of the present
invention in a quasi-static Rayleigh fading.
DETAILED DESCRIPTION
[0023]
The present invention Will noW be described more
fully hereinafter With reference to the accompanying draW
ings.
Sep. 21, 2006
US 2006/0212774 A1
[0024] Consider a space-time turbo code for tWo transmit
antennas. FIG. 1 is a block diagram illustrating an encoder
of the space-time turbo code With parallel concatenation of
tWo recursive systematic convolutional (RSC) encoders 121,
122 separated by an even-odd interleaver. Referring to FIG.
1, the encoder has tWo outputs: systematic bits and punc
tured parity bits. The systematic bits are same as input bits
and the punctured parity bits are generated from modulo-2
addition 150 of the outputs of the ?rst RSC encoder 121 and
the second RSC encoder 122 the codeWord of the space-time
Where, X0 and X6 are not both Zero.
[0033] HoWever, the space-time turbo code With the code
Word matrix in equation (4) does not achieve full antenna
diversity because of puncturing and suboptimal decoding,
Which degrades its performance. To achieve full antenna
diversity, rotated construction Was proposed for the space
time turbo code With rotated construction is given by equa
tion (6).
turbo code is given by equation (1).
Equation (6)
Cu
[0034]
[0025]
[0026]
encoder,
[0027]
[0028]
Where, X(D) is input bits With code length l,
G(D) is the generator polynominal of the RSC
It is knoWn by simulation that antenna diversity can
be achieved by using rotated construction.
[0035] The space-time turbo code using quantiZed feed
back With tWo transmit antennas is described as folloWs.
rc(.) is the bit permuter, and
[0036] The performance of an orthogonal space-time
6e(.) denotes puncturing operation Which replaces
bits in odd position With Zero.
block code With tWo transmit antennas is improved by using
a diagonal Weighting scheme. In the diagonal Weighting
[0029] Assuming that l is even, let X0 and X6 denote the
tWo antennas With ]a]2 and l—]a]2, respectively, Where a is the
odd and even information bit vectors With length l/ 2, respec
Weighting factor.
scheme, the transmitter adjusts transmit poWer by Weighting
tively.
[0037]
[0030]
The odd and even generator matrices are given by
equation (2) and
scheme.
g0 g2
O
80
Go :
I
FIG. 2 is a diagram illustrating a normaliZed BER
of the space-time turbo code With the diagonal Weighting
8H
'
Equation (2)
814
'.
O
0
go
[0038] Referring to FIG. 2, It is shoWn that the space-time
turbo code With the diagonal Weighting scheme has the
loWest BER at ]a]2=0.5. The space-time turbo code With
Weights of ]a]2=l—]a]2=0.5 is same as the original space-time
turbo code With unWeighted transmit poWer. Hence, the
diagonal Weighting scheme does not improve the perfor
mance of the space-time turbo code.
and
g1 g3
8H
O
81
8H
:
'
GE :
O
-
O
Equation (3)
[0039] To improve its performance by using quantiZed
feedback information, We propose neW feedback schemes:
antenna altering (AA), quantiZed phase feedback (QPF), and
:
combined AA and QPF.
g1
[0040] Hereinafter, Antenna Altering (AA) Will be
described in detail.
Where, gi (i=0, 1, . . . , l-l) is the ith coefficient of G(D).
[0031]
Since the column permutation of the codeWord
matrix does not change its rank property, the column per
mutated codeWord of a space-time turbo is given by equa
tion (4).
Equation (4)
Cu
Where, PO and P6 are the odd and even permutation matrices
[0041]
Consider a state transition from state s to state s' at
symbol time t in the component decoder. For the received
signal yt at symbol time t, the branch metric of the transition
(s, s') is given by equation (7).
my“ 5. s’) = 2 Po. Is. 5’. map, ls. SW5’ IS)
Equation (7)
Pt
Where, Pt denotes the parity bit.
corresponding to permutation of odd and even bits by rc(.),
[0042] Assume that ct=a and pt=b are the systematic and
respectively.
parity bits corresponding to the transition (s, s') at symbol
[0032] To become full rank, the codeWord matrix in equa
tion (4) must meet the folloWing suf?cient condition given
by equation (5).
time t, respectively. As the puncturer 131, 132 in FIG. 1
replaces bits of odd position With Zeros, the parity bits
generated by the ?rst RSC encoder 121 are not included in
the received symbols at odd symbol time. Then, the parity
bit at odd symbol time is independent of the state transition
Sep. 21, 2006
US 2006/0212774 A1
(s, s'). the branch metric at even and odd symbol time are
[0050]
given by equation (8a) and equation (8b) respectively.
ing the information of the channel gain.
y‘(K,S,S')=P(Y'/c‘=a,p‘=b)P(c‘=a), l=even
Table 1 shoWs an example of feedback bit re?ect
Equation (8a)
TABLE 1
and
Comparison
of channel gain
Equation (8b)
710/1, 5, 5,) :
2
Po. | c, = a. mm = a).
memo
Feedback bit
131] 5 1321
0
‘all < 1321
1
[0051] After selecting the transmit antenna for the sys
[0043] From equation (8a) and (8b), the probability of the
systematic bit is involved in computing the branch metric at
every symbol time While that of the parity bit is involved in
it at even symbol time. Thus, the reliability of systematic bits
is more important than that of parity bits in decoding of the
space-time turbo code. If systematic bits are transmitted
through the antenna With smaller channel gain, the perfor
mance of the space-time turbo code degrades.
[0044] To mitigate the performance degradation, We pro
pose an antenna altering (AA) scheme. The AA scheme
alWays transmits the systematic bits through the antenna
With larger channel gain according to matrix With the AA
scheme is given by equation (9).
tematic bit and the punctured parity bit, the systematic bit
and the punctured parity bit is mapping to corresponding
constellation according to an signal mapper 300 and transmit
through the antennas 501 and 502.
[0052] FIG. 4 is a How chart of method of encoding the
space-time turbo code With the antenna altering scheme.
[0053] Referring to FIG. 4, at step S110, encoding a
message for communication With space-time turbo code and
generating a systematic bit and a punctured parity bit. At
step S120, receiving a feedback bit re?ecting the informa
tion of the channel gain of a plurality of transmit antennas
from receive antenna. At step S130, selecting a transmit
antenna With larger channel gain of the plurality of transmit
antennas according to the feedback bit. At step S140,
transmitting the systematic bit through the selected antenna
X2]
CU
XOPO
Equation (9)
[XEGOGBXOGE XOPOGOGBXEPeGE
XEGOGBXOGE XOPOGOGBXEPeGE
[
X"!
XOP’
and transmitting the punctured parity bit through another
antenna.
], otherwise
Where (xi is the complex channel gain from the ith transmit
[0054] Hereinafter, QuantiZed Phase Feedback (QPF) Will
be described in detail.
[0055] FIG. 5 is a diagram illustrating a constellation of
the transmitted and received symbols in a noiseless fading
channel.
antenna to the receive antenna.
[0045] FIG. 3 is a diagram illustrating a transmitter of the
space-time turbo code With an antenna altering scheme.
[0046] Referring to FIG. 3, the transmitter comprise a
space-time turbo encoder 100 encoding input bits corre
sponding to a message With space-time turbo code and
generating a systematic bit and a punctured parity bit; and an
alternator 200 selecting one of the tWo antennas 501 and 502
for the systematic bit and the punctured parity bit and
transmitting the systematic bit and the punctured parity bit
respectively through selected antenna.
[0047] The alternator 200 selects transmit antenna With
larger channel gain of the tWo transmit antennas 501 and 502
and transmit the systematic bit through the selected antenna.
[0056] Referring to FIG. 5, Where [3 and [3' are angles
betWeen transmitted signals and betWeen rotated signals,
respectively. It is shoWn that the minimum Euclidean dis
tance betWeen the received symbols increases by rotating the
constellation. The performance of the space-time turbo code
is improved by applying the constellation rotation to the
transmit signals.
[0057]
Consider the QPF scheme With feedback index
ne{0, 1, 2, . . . , 2k_l} Where k is the number offeedback bits.
Suppose that the transmitter rotates the symbols of ith
transmit antenna by a rotation angle 6i(n). Then, the received
signal at symbol time t is given by equation (10)
Equation (10)
[0048] For example, in case lallila2l, the feedback bit “0”
is transmitted to transmitting terminal from receive terminal.
The systematic bit is transmitted through the ?rst transmit
antenna 501 and the punctured parity bit is transmitted
through the second transmit antenna 502.
[0049] On the contrary, in case ]al]<]a2], the feedback bit
“1” is transmitted to transmitting terminal from receive
terminal. The systematic bit is transmitted through the
second transmit antenna 502 and the punctured parity bit is
[0058] Where ES is the symbol energy, (xi is the complex
channel gain for the ith transmit antenna, cit is the transmitted
symbol of the ith antenna at symbol time t, and m is an iid
complex Gaussian noise With Zero mean and variance of
NO/2 per dimension.
transmitted through the second transmit antenna 502. Where
[0059]
(xi is the complex channel gain from the ith transmit antenna
erroneous codeWord e=el1el2e2le22 . . . etlet2 When coded
Assume that the receiver decides in favor of the
to the receive antenna.
Word c=cllcl2c2lc22 . . . ctlct2 is transmitted. If perfect CS1
Sep. 21, 2006
US 2006/0212774 A1
is available at the receiver, conditional pairwise error prob
ability given (X1 and (x1 is bounded as equation (11).
Equation (1 l)
l
[0063] By expanding the exponential term in equation (1 4)
into a Talyor series, A0(n) and SD, n=0, 1, 2, . . . , 2k—l,
minimizing conditional pairWise error probability are
obtained as equation (15).
2
(M0),
,A0(2" -1),s0,
,szkil) =
Equation(l5)
82k
arg
A533
274%)!
k:0
is the squared Euclidian distance betWeen c and e.
[0060] After some derivation, the squared Euclidian dis
tance is given by equation (12).
d2(c, e) = [111 £19101) azelgzm) ]
Z
A11 A12
A21 A22
]
Sn
cos2k(LA12 + a5 + A000) dd
Equation (12)
111‘ [191W
113E192“)
[0064] For simplicity, the rotation angle 01(n) and 02(n)
are set to A0(n) and Zero, respectively.
cos(LA12 + L111 — L112 + 01 (n) — 02(n))
[0065]
In case that the BPSK space-time turbo code adopts
l-bit feedback, the feedback index n is set to 0 and 1 When
the phase difference 4) falls in subset SO and S1, respectively.
Where,
[0066] Then, the optimal rotation angle and disjoint sub
sets minimiZing conditional pairWise error probability are
obtained as equation (16).
and L. denotes the phase of the complex value.
[0061] From equation (11) and (12), conditional pairWise
error probability given given (x1 and (x1 is bounded as
equation (13).
P(C —> ‘3| 111, 112) 5
Equation (13)
Where, ¢=L0t1—0t2 is the phase difference betWeen the
channel gains and A0(n)=01(n)—02(n) is the difference
betWeen the rotation angles.
For BPSK, A12 is real and the optimal rotation angles
become A0(0)=J1:/2 and A0(l)=0, and the disjoint subsets
become S1=[J'|Z/4, 3J1:/4]U[5J1:/4, 775/4] and S2=SlC Where C
denotes the complement set operation.
Let, SO,S1, . . . ,S2k_l denote disjoint subsets of the
[0067] In case of the QPSK space-time turbo code, it is
dif?cult to ?nd the optimal solution of equation (1 5) as LA12
depends on 4). From the fact that the optimal rotation angles
region [0, 275] whose union is the region [0, 275]. When the
in case of BPSK maximiZes the angle betWeen rotated
phase difference 4) falls in a subset Sn, the receiver feeds
signals [3‘, We heuristically obtain the rotation angles and
disjoint subsets for maximum value of [3‘.
[0062]
back the index n to the transmitter so that the rotation angle
is decide as A0(n). By integrating equation (13) over the
subsets Sn, n=0, 1, 2, . . . , 2k—l, conditional pairWise error
probability given [all and [all is bounded as equation (14).
[0068] Table 2 shoWs the feedback index and the differ
ence of the rotation angles corresponding to disjoint subset
SD for both BPSK and QPSK.
TABLE 2
Modulation Disjoint subset Sn
BPSK
7r
3” 5n
7”
[0,2] [TINT
0
Feed-
Rotation
back
Index 11
angle
A0(n)
0.5712
Sep. 21, 2006
US 2006/0212774 A1
alternator 200 selecting one of the two antennas 501 and 502
TABLE 2-continued
Feed-
Rotation
Modulation Disjoint subset Sn
back
Indexn
angle
A6(n)
7r 3n
1
0
0
0-2575
5n 7n
l1’ ZlUlT Tl
QPSK
7r
3n 5
7n 9n
[ -]u[—.— u[—.—]u
8
8
8
UR l37r
—
—
l s ’ s lU
8
l57r
—
8
for the systematic bit and the punctured parity bit and
transmitting the systematic bit and the punctured parity bit
respectively through selected antenna; and a phase rotator
401 and 402 rotating the constellation corresponding to the
systematic bit and the punctured parity bit, respectively.
[0077] The alternator 200 selects transmit antenna with
larger channel gain of the two transmit antennas 501 and 502
through the ?rst feedback bit being transmitted from receive
antenna and transmit the systematic bit through the selected
antenna.
2
s ’ 7r
[0078]
1
O
The phase rotator 401 rotates the constellation so
that the channel gain phase difference between the transmit
antennas 501 and 502 through the second feedback bit being
transmitted from the receive antenna is largest.
[0079] The transmit antennas are altered according to the
feedback bits are always transmitted through the transmit
antenna with larger channel gain. Then, after signal map
[0069]
FIG. 6 is a diagram illustrating a transmitter of the
space-time turbo code with a quantized phase feedback.
ping, the signal of each antenna is rotated the constellation
according to the feedback information of the channel phase.
For example, if both the AA and QPF schemes use the
feedback information of 1 bit, the combined scheme needs
[0070] Referring to FIG. 6, the transmitter comprise a
space-time turbo encoder 100 encoding input bits corre
that of 2 hits.
sponding to a message with space-time turbo code and
generating a systematic bit and a punctured parity bit; and a
phase rotator 401 and 402 rotating the constellation corre
detail.
sponding to the systematic bit and the punctured parity bit,
[0081] The performance of the proposed feedback
[0080]
Hereinafter, simulation results will be described in
respectively.
schemes is evaluated for the space-time turbo code with two
[0071] The constellation corresponding to the systematic
bit and the punctured parity bit by signal mapper 300 is
transmit antennas and one receive antenna in a quasi-static
decided. The phase rotator 401 and 402 rotate the constel
lation so that phase difference of the channel gain between
the two transmit antennas 501 and 502, as shown above table
2, through feedback bit being transmitted from the receive
antenna is largest. The rotated symbol is transmitted through
antennas 501 and 502.
Rayleigh fading channel. Assume that perfect CS1 is avail
able at both the RSC encoders for the BPSK and QPSK
space-time turbo code are given by gb(D)=(1 +D2)/ (1 +D+D2)
and gq(D)=(1+2D+2D2)/(1+3D+2D2+2D3) respectively.
The codelength/is 1024 and the number of iterations is 4.
The space-time turbo code with AA and QPF schemes
adopts the feedback information of 1 bit as in Table 1 and
Table 2. The transmit antenna is selected (AA scheme) or the
constellation is rotated (QPF scheme) according to feedback
[0072] FIG. 7 is a ?ow chart encoding the space-time
turbo code with the quantized phase feedback.
bit per one ?ame (Codelength is 1024).
[0073] Referring to FIG. 7, at step S210, encoding a
message for communication with space-time turbo code and
generating a systematic bit and a punctured parity bit. At
[0082] FIG. 9 is a graph illustrating a performance of the
BPSK space-time turbo codes with feedback scheme in
accordance with an exemplary embodiment of the present
step S220, receiving a feedback bit re?ecting the phase
invention in a quasi-static Rayleigh fading.
[0083] Referring to FIG. 9, the space-time turbo codes
with the proposed AA, QPF and combined schemes have the
difference information of the channel gain of a plurality of
transmit antennas from receive antenna. At step S230,
rotating the constellation corresponding to the systematic bit
and the punctured parity bit respectively so that phase
difference of the channel gain according to feedback bit is
largest.
SNR gains of about 1.2 dB, 2 dB and 3 dB, respectively, over
the conventional space-time turbo code at BER of 10_2. the
AA scheme has lower BER than the QPF scheme as the
minimum Euclidian distance by rotating constellation does
[0074] The proposed AA and QPF schemes obtain the
independent performance gains from the feedback informa
tion of the channel gain and phase, respectively. To improve
not signi?cantly increase for BPSK.
the performance further with the feedback information of
both the channel gain and phase, we combine the AA scheme
with the QPF scheme.
accordance with an exemplary embodiment of the present
[0075] FIG. 8 is a diagram illustrating a transmitter of the
space-time turbo code with a combined scheme.
[0076] Referring to FIG. 8, the transmitter comprise a
space-time turbo encoder 100 encoding input bits corre
sponding to a message with space-time turbo code and
generating a systematic bit and a punctured parity hit; an
[0084] FIG. 10 is a graph illustrating a performance of the
QPSK space-time turbo codes with feedback scheme in
invention in a quasi-static Rayleigh fading.
[0085] Referring to FIG. 10, the proposed schemes have
still better performance than the conventional scheme for
QPSK. However, the QPF scheme out performs the AA
scheme at relatively high SNR. It is because the gain of
antenna altering decreases as SNR increases.
[0086] The AA scheme improves the reliability of the
systematic bits by altering the antennas according to the
Sep. 21, 2006
US 2006/0212774 A1
feedback information of the channel gain. The QPF scheme
increases the minimum Euclidian distance by rotating the
constellation according to the feedback information of the
channel phase. From simulation results, the AA and QPF
schemes have better performance than the conventional
scheme and the combined scheme achieves the SNR gains of
up 3 dB and 2 dB at BER 10-2 for BPSK and QPSK,
respectively. Thus, the AA and QPF of the present invention
have better performance than the conventional scheme.
[0087]
It Will be apparent to those skilled in the art that
various modi?cations and variation can be made in the
present invention Without departing from the spirit or scope
of the invention. Thus, it is intended that the present inven
6. The method for transmission of claim 5, Wherein the
feedback bit is 1 bit and has the information of the channel
gain of the tWo transmit antennas is re?ected in the feedback
bit.
7. An apparatus for transmission encoding a message With
space-time turbo code in digital mobile communication
system having a plurality of transmit antennas, comprising:
a space-time turbo encoder encoding input bit correspond
ing to the message With space-time turbo code and
generating a systematic bit and a punctured parity bit;
and
a phase rotator rotating a constellation corresponding to
tion cover the modi?cations and variations of this invention
the systematic bit and the punctured parity bit respec
provided they come Within the scope of the appended claims
and their equivalents.
tively,
Wherein the phase rotator rotates the constellation so that
phase difference of the channel gain betWeen the plu
What is claimed is:
1. An apparatus for transmission encoding a message With
space-time turbo code in digital mobile communication
system having a plurality of transmit antennas, comprising:
a space-time turbo encoder encoding input bit correspond
ing to the message With space-time turbo code and
generating a systematic bit and a punctured parity bit;
and
an alternator selecting one of the plurality of transmit
antennas for the systematic bit and the punctured parity
bit and transmitting the systematic bit and the punc
tured parity bit respectively through the selected
antenna,
Wherein the alternator selects a transmit antenna With
larger channel gain of the plurality of transmit antennas
according to feedback bit being transmitted from
receive antenna and transmit the systematic bit through
the selected antenna.
2. The apparatus for transmission of claim 1, Wherein the
number of the transmit antennas in the digital mobile
communication system is tWo.
3. The apparatus for transmission of claim 2, Wherein the
feedback bit is 1 bit and the information of the channel gain
of the tWo transmit antennas is re?ected in the feedback bit.
4. A method for transmission encoding a message With
space-time turbo code in digital mobile communication
system having a plurality of transmit antennas, comprising:
encoding the message for communication With space-time
turbo code and generating a systematic bit and a
punctured parity bit;
receiving a feedback bit re?ecting information of the
channel gain of the plurality of transmit antennas from
receive antenna;
selecting a transmit antenna With the largest channel gain
of the plurality of transmit antennas according to the
feedback bit; and
transmitting the systematic bit through the selected trans
mit antenna and the punctured parity bit through one of
the other antennas.
5. The method for transmission of claim 4, Wherein the
number of the transmit antennas in the digital mobile
communication system is tWo.
rality of transmit antennas according to a feedback bit
being transmitted from the receive antenna Would be at
its largest.
8. The apparatus for transmission of claim 7, Wherein the
number of the transmit antennas in the digital mobile
communication system is tWo.
9. The apparatus for transmission of claim 8, Wherein the
feedback bit is 1 bit and the phase difference information of
the channel gain of the tWo transmit antennas is re?ected in
the feedback bit.
10. A method for transmission encoding a message With
space-time turbo code in digital mobile communication
system having a plurality of transmit antennas, comprising:
encoding the message for communication With space-time
turbo code and generating a systematic bit and a
punctured parity bit;
receiving a feedback bit re?ecting phase difference infor
mation of the channel gain of the plurality of transmit
antennas from receive antenna; and
rotating a constellation corresponding to the systematic
bit and the punctured parity bit respectively so that
phase difference of the channel gain according to a
feedback bit Would be at its largest.
11. The method for transmission of claim 10, Wherein the
number of the transmit antennas in the digital mobile
communication system is tWo.
12. The method for transmission of claim 11, Wherein the
feedback bit is 1 bit and the phase difference information of
the channel gain of the tWo transmit antennas is re?ected in
the feedback bit.
13. An apparatus for transmission encoding a message
With space-time turbo code in digital mobile communication
system having a plurality of transmit antennas, comprising:
a space-time turbo encoder encoding input bit correspond
ing to the message With space-time turbo code and
generating a systematic bit and a punctured parity bit;
and
an alternator selecting one of the plurality of transmit
antennas for the systematic bit and the punctured parity
bit and transmitting the systematic bit and the punc
tured parity bit respectively through the selected
antenna; and
US 2006/0212774 A1
a phase rotator rotating a constellation corresponding to
the systematic bit and the punctured parity bit respec
tively,
Wherein the alternator selects a transmit antenna With
larger channel gain of the plurality of transmit antennas
according to a ?rst feedback bit being transmitted from
receive antenna and transmit the systematic bit through
the selected antenna, and
Wherein the phase rotator rotates the constellation so that
phase difference of the channel gain betWeen the plu
rality of transmit antennas according to a second feed
back bit being transmitted from the receive antenna
Would is at its largest.
14. The apparatus for transmission of claim 13, Wherein
the number of the transmit antennas in the digital mobile
communication system is tWo.
15. The apparatus for transmission of claim 14, Wherein
the ?rst feedback bit is 1 bit and the information of the
channel gain of the tWo transmit antennas is re?ected in the
feedback bit, and
the second feedback bit is 1 bit and the phase information
of the channel gain of the tWo transmit antennas is
re?ected in the feedback bit.
16. A method for transmission encoding a message With
space-time turbo code in digital mobile communication
system having a plurality of transmit antennas, comprising:
encoding the message for communication With space-time
turbo code and generating a systematic bit and a
punctured parity bit;
Sep. 21, 2006
receiving a ?rst feedback bit re?ecting information of the
channel gain of the plurality of transmit antennas from
receive antenna;
selecting a transmit antenna With the largest channel gain
of the plurality of transmit antennas according to the
?rst feedback bit;
allocating the systematic bit being transmitted through the
selected transmit antenna and the punctured parity bit
being transmitted through one of the other antennas;
receiving a second feedback bit re?ecting phase differ
ence information of the channel gain of the plurality of
transmit antennas from receive antenna; and
rotating a constellation corresponding to the systematic
bit and the punctured parity bit respectively so that
phase difference of the channel gain according to the
second feedback bit Would is at its largest.
17. The method for transmission of claim 16, Wherein the
number of the transmit antennas in the digital mobile
communication system is tWo.
18. The method for transmission of claim 17, Wherein the
?rst feedback bit is 1 bit and the information of the channel
gain of the tWo
-transmit antennas is re?ected in the feedback bit, and
the second feedback bit is 1 bit and the phase difference
information of the channel gain of the tWo transmit
antennas is re?ected in the feedback bit.