Title of Invention

"METHOD AND APPARATUS FOR TRANSMITTING REFERENCE SIGNALS IN A BROADBAND WIRELESS ACCESS COMMUNICATION SYSTEM"

Abstract ABSTRACT TITLE:METHODS AND APPARATUSES FOR TRANSMITTING REFERENCE SIGNALS IN A BROADBAND WIRELESS ACCESS COMMUNICATION SYSTEM The invention relates to a method for transmitting reference signals in a Broadband Wireless Access (BWA) communication system , the method comprising the steps of transmitting first reference signals (301,303) for identifying a first transmit antenna using a first predetermined number of sub- carriers in a first mini sub-channel, the first reference signals being transmitted through the first transmit antenna, and the first mini sub-channel being occupied by a predetermined time domain and sub-frequency domains of a second predetermined number of sub-carriers; and transmitting second reference signals (305,307) for identifying a second transmit antenna using the first predetermined number of the sub-carriers in a second mini sub-channel, the second reference signals being transmitted through the second transmit antenna, and the second mini sub-channel being occupied by the predetermined time domain and the sub-frequency domains of the second predetermined number of sub-carriers, wherein first sub-carriers, through which the first reference signals are transmitted, include sub-frequency domains different from sub-frequency domains occupied by second sub-carriers, through which the second reference signals are transmitted, wherein transmitting the first reference signals further comprises transmitting null data (302,304) in the first mini sub-channel using sub-carriers including sub-frequency domains, that are identical to the sub- frequency domains occupied by the second sub-carriers , wherein transmitting the second reference signals further comprises transmitting null data (306,308) in the second mini sub-channel using sub-carriers including sub-frequency domains that are identical to the sub-frequency domains occupied by the first sub-carriers.
Full Text

APPARATUS AND METHOD FOR TRANSMITTING PILOT SIGNAL IN
A BWA COMMUNICATION SYSTEM USING TRANSMIT ANTENNAS
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a Broadband Wireless Access
(BWA) communication system, and more particularly to an apparatus and a
method for transmitting pilot signals in a BWA communication system using a
plurality of transmit antennas.
2. Description of the Related Art
In a 4th generation (4G) communication system, which is the next
generation communication system, research is being performed to provide users
with services having various Qualities of Services (QoSs) at a high speed. In
particular, in the current 4G communication system, research is being performed
to support a high speed service for ensuring mobility and QoS in a BWA
communication system, such as a wireless Local Area Network (LAN) system
and a wireless Metropolitan Area Network (MAN) system.
Typical types of 4G communication system are an Institute of Electrical
and Electronics Engineers (IEEE) 802.16a/d communication system and an IEEE
802.16e communication system. The IEEE 802.16a/d communication system and
the IEEE 802.16e communication system utilize an Orthogonal Frequency
Division Multiplexing (OFDM) scheme/an Orthogonal Frequency Division
Multiple Access (OFDMA) scheme that support a broadband transmission
network for a physical channel of the wireless MAN system. The IEEE 802.16a/d
communication system and the IEEE 802.16e communication system transmit
mass storage data at a high speed using the OFDM/OFDMA scheme. The IEEE
802.16a/d communication system considers only a single cell structure and
stationary subscriber stations (SSs), i.e., the system does not accommodate the
mobility of the SSs. However, the IEEE 802.16e communication system
accommodates the mobility of an SS in the IEEE 802.16a communication system.
Herein, an SS having the mobility will be referred to as a Mobile Station (MS).

FIG. 1 is a diagram illustrating a conventional mini sub-channel structure
of an IEEE 802.16d communication system using a Single Input Single Output
(SISO) scheme. Because the IEEE 802.16d communication system uses the
OFDMA scheme, the IEEE 802.16d communication system uses a plurality of
sub-carriers and a plurality of sub-channels each of which comprises at least
one sub-carrier.
Referring to FIG. 1, a horizontal axis represents a time domain, a vertical
axis represents a frequency domain, and one block occupied by the time domain
and the frequency domain represents a tone, i.e., a sub-carrier. Herein, a
frequency domain occupied by the sub-carrier will be referred to as a 'sub-
frequency domain'. It is noted that the tone is used together with the sub-carrier
for convenience of description.
One mini sub-channel 101 comprises a predetermined number of tones,
e.g., 18 tones. When the SISO scheme is used, the mini sub-channel 101
comprises a predetermined number of pilot tones, e.g., two pilot tones 102 and
103, for a channel estimation. The remaining tones excluding the pilot tones 102
and 103 represent data tones.
As illustrated in FIG. 1, the pilot tones 102 and 103 are located in central
positions of the mini sub-channel 101 for the channel estimation. For example, a
transmitter, e.g., a Base Station (BS), transmits the pilot tones 102 and 103, so
that a receiver, e.g., an MS or plurality of MSs, can estimate radio channel
conditions on the downlink.
Because the mini sub-channel 101 comprises the two pilot tones 102
and 103, a ratio of pilot tones with respect to the total tones is 1/9.
As described above, the MSs estimate radio channel conditions using the
pilot tones transmitted from the BS and demodulate received data according to
the estimated radio channel conditions. Accordingly, estimating the radio channel
conditions has a great influence on the entire system performance.
The sub-channel, which is a basic unit of data transmission in the IEEE

802.16d communication system, comprises three mini sub-channels.
Accordingly, it is possible to transmit a symbol including 48 tones through one
sub-channel.
The IEEE 802.16d communication system supports a multiple antenna
scheme. In the multiple antenna scheme, a BS transmits signals through a
plurality of transmit antennas. The multiple antenna scheme may be classified
into a Multiple Input Multiple Output (MIMO) scheme and a Multiple Input
Single Output (MISO) scheme according to the number of receive antennas used
by MSs.
It is generally known that the multiple antenna scheme has number of
advantages. For example, the multiple antenna scheme transmits signals through a
plurality of transmit antennas, so that the transmitted signals have a plurality of
transmit paths. Therefore, it is possible to acquire transmit antenna diversity gain.
Further, the multiple antenna scheme transmits signals through a plurality of
transmit antennas, so that the transmitted signals have a plurality of transmit
spaces. Therefore, it is possible to acquire spatial diversity gain by using a Spatial
Multiplexing (SM) scheme.
When the multiple antenna scheme is used as described above, it is
possible to acquire the transmit antenna diversity gain and the spatial diversity
gain. Accordingly, the multiple antenna scheme is used for efficiently transmitting
information data. However, even though the multiple antenna scheme is used, the
transmit antenna diversity gain and the spatial diversity gain may be varied
according to actual radio channel conditions.
Further, when the multiple antenna scheme is used as described above,
the MS must precisely estimate radio channel conditions from each of the
transmit antennas to the receive antenna of the MS in order to demodulate the
signals transmitted from the BS through each of the transmit antennas because it
is possible to acquire the transmit antenna diversity gain and the spatial diversity
gain only through the precise estimation of the radio channel conditions. In the
conventional wireless communication system, the radio channel conditions are
estimated using pilot signals.

However, when the transmit antennas are used as described above,
transmit paths experienced by the signals transmitted through each of the transmit
antennas may be varied. Therefore, radio channels experienced by the signals
transmitted through each of the transmit antennas may also be varied. Accordingly,
it is possible to achieve the precise radio channel estimation only when the
precise identification of the transmit antennas is possible. In addition, it is
possible to precisely demodulate received signals through the precise radio
channel estimation. More specifically, because pilot signals are used for the radio
channel estimation differently from general information data, the identification of
the transmit antennas becomes more and more important.
In order to identify the transmit antennas, the mini sub-channel 101 must
transmit pilot signals through each of the transmit antennas at different positions.
However, in order to transmit the pilot signals through each of the transmit
antennas, it is necessary to reduce the amount of transmittable data. As a result, as
the number of the transmit antennas increases, the amount of transmittable data
reduces.
For example, when one transmit antenna is used, one mini sub-channel
101 uses only two pilot tones 102 and 103 and can transmit data using the remaining tones, i.e., the data tones, as described in FIG. 1. However, when two
transmit antennas, i.e., a first and a second transmit antenna, are used, it is
impossible to transmit data through the second transmit antenna in a tone
identical to the tone transmitting pilot signals through the first transmit antenna.
As described above, the amount of transmittable data is reduced as the number of
the transmit antennas increases, thereby decreasing the total system transmission
capacity. Consequently, the entire system quality may deteriorate.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been designed to solve the above
and other problems occurring in the prior art. It is an object of the present
invention to provide an apparatus and a method for transmitting pilot signals in a
BWA communication system using a plurality of transmit antennas.

It is an object of the present invention to provide an apparatus and a
method for transmitting pilot signals using a Convolutional Turbo Coding (CTC)
scheme in a BWA communication system using transmit antennas.
In order to accomplish the above and other objects, according to an aspect
of the present, there is provided a method for transmitting reference signals in a
Broadband Wireless Access (BWA) communication system including a first
transmit antenna, a second transmit antenna, and a plurality of sub-carriers, each
of the sub-carriers occupying a sub-frequency domain. The method comprises the
steps of transmitting reference signals for identifying the first transmit antenna
through a second predetermined number of sub-carriers in a first mini sub
channel, the first mini sub-channel being transmitted through the first transmit
antenna and occupied by a predetermined time domain and sub-frequency
domains of a first predetermined number of sub-carriers; and transmitting
reference signals for identifying the second transmit antenna through the second
predetermined number of the sub-carriers in a second mini sub-channel, the
second mini sub-channel being transmitted through the second transmit antenna
and occupied by the time domain and the sub-frequency domains of the first
predetermined number of sub-carriers.
According to another aspect of the present, there is provided a method for
transmitting reference signals in a Broadband Wireless Access (BWA)
communication system including a first transmit antenna, a second transmit
antenna, and a plurality of sub-carriers, each of the sub-carriers occupying a sub-
frequency domain. The method comprises the steps of generating coded symbols
by coding information data to be transmitted according to a first predetermined
coding scheme; generating coded symbols to be transmitted through the first
transmit antenna and coded symbols to be transmitted through the second transmit
antenna by coding the coded symbols according to a second predetermined
coding scheme; inserting reference signals for identifying the first transmit
antenna into a second predetermined number of sub-carriers in a first mini sub-
channel, the first mini sub-channel being transmitted through the first transmit
antenna and occupied by a predetermined time domain and sub-frequency
domains of a first predetermined number of sub-carriers; inserting reference
signals for identifying the second transmit antenna into the second predetermined

number of the sub-carriers in a second mini sub-channel, the second mini sub-
channel being transmitted through the second transmit antenna and occupied by
the time domain and the sub-frequency domains of the first predetermined
number of sub-carriers; inserting null data into sub-carriers including sub-
frequency domains, which are identical to the sub-frequency domains of the sub-
carriers for transmitting the reference signals for identifying the second transmit
antenna from among sub-carriers excluding the sub-carriers, which transmit the
reference signals for identifying the first transmit antenna, in the first mini sub-
channel; inserting null data into sub-carriers including sub-frequency domains,
which are identical to the sub-frequency domains of the sub-carriers for
transmitting the reference signals for identifying the first transmit antenna from
among sub-carriers excluding the sub-carriers, which transmit the reference
signals for identifying the second transmit antenna, in the second mini sub-
channel; inserting the coded symbols to be transmitted through the first transmit
antenna into sub-carriers using a truncation scheme, which exclude the sub-
carriers including the reference signals and the null data in the first mini sub-
channel; inserting the coded symbols to be transmitted through the second
transmit antenna into sub-carriers using the truncation scheme, which exclude the
sub-carriers including the reference signals and the null data in the second mini
sub-channel; processing signals of the first mini sub-channel to transmit the
processed signals through the first transmit antenna; and processing signals of the
second mini sub-channel to transmit the processed signals through the second
transmit antenna.
According to further another aspect of the present, there is provided an
apparatus for transmitting reference signals in a Broadband Wireless Access
(BWA) communication system using a first transmit antenna, a second transmit
antenna, and a plurality of sub-carriers, each of the sub-carriers occupying a sub-
frequency domain. The apparatus comprises a first transmitter for transmitting
reference signals for identifying the first transmit antenna through a second
predetermined number of sub-carriers in a first mini sub-channel, the first mini
sub-channel being transmitted through the first transmit antenna and occupied by
a predetermined time domain and sub-frequency domains of a first predetermined
number of sub-carriers; and a second transmitter for transmitting reference signals
for identifying the second transmit antenna through the second predetermined

number of the sub-carriers in a second mini sub-channel, the second mini sub-
channel being transmitted through the second transmit antenna and occupied by
the time domain and the sub-frequency domains of the first predetermined
number of sub-carriers.
According to still another aspect of the present, there is provided an
apparatus for transmitting reference signals in a Broadband Wireless Access
(BWA) communication system using a first transmit antenna, a second transmit
antenna, and a plurality of sub-carriers, each of the sub-carriers occupying a sub-
frequency domain. The apparatus comprises a first coder for generating coded
symbols by coding information data to be transmitted according to a first
predetermined coding scheme; a second coder for coding the coded symbols
according to a second predetermined coding scheme in order to generating coded
symbols to be transmitted through the first transmit antenna and coded symbols to
be transmitted through the second transmit antenna; a first reference signal sub-
carrier inserter for inserting reference signals for identifying the first transmit
antenna into a second predetermined number of sub-carriers in a first mini sub-
channel, the first mini sub-channel being transmitted through the first transmit
antenna and occupied by a predetermined time domain and sub-frequency
domains of a first predetermined number of sub-carriers; a first sub-carrier
mapper for inserting null data into sub-carriers including sub-frequency domains,
which are identical to sub-frequency domains of the sub-carriers for transmitting
the reference signals for identifying the second transmit antenna from among sub-
carriers excluding the sub-carriers, which transmit the reference signals for
identifying the first transmit antenna, in the first mini sub-channel, and inserting
the coded symbols to be transmitted through the first transmit antenna into sub-
carriers using a truncation scheme, which exclude the sub-carriers including the
reference signals and the null data in the first mini sub-channel; a second
reference signal sub-carrier inserter for inserting reference signals for identifying
the second transmit antenna into the second predetermined number of the sub-
carriers in a second mini sub-channel, the second mini sub-channel being
transmitted through the second transmit antenna and occupied by the time domain
and the sub-frequency domains of the first predetermined number of sub-carriers;
a second sub-carrier mapper for inserting null data into sub-carriers including
sub-frequency domains, which are identical to sub-frequency domains of the sub-

carriers for transmitting the reference signals for identifying the first transmit
antenna from among sub-carriers excluding the sub-carriers, which transmit the
reference signals for identifying the second transmit antenna, in the second mini
sub-channel, and inserting the coded symbols to be transmitted through the
second transmit antenna into sub-carriers using the truncation scheme, which
exclude the sub-carriers including the reference signals and the null data in the
second mini sub-channel; a first transmitter for processing signals of the first mini
sub-channel and transmitting the processed signals through the first transmit
antenna; and a second transmitter for processing signals of the second mini sub-
channel and transmitting the processed signals through the second transmit
antenna.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects, features, and advantages of the present
invention will be more apparent from the following detailed description taken in
conjunction with the accompanying drawings in which:
FIG. 1 is a diagram illustrating a conventional mini sub-channel structure
in an IEEE 802.16d communication system using a SISO scheme;
FIG. 2 is a diagram schematically illustrating a data transmission
operation of a transmitter using a plurality of transmit antennas in an IEEE
802.16e communication system according to an embodiment of the present
invention;
FIG. 3 is a diagram illustrating a mini sub-channel structure in an IEEE
802.16e communication system using a plurality of transmit antennas according
to an embodiment of the present invention;
FIG. 4 is a diagram illustrating a CTC coder in an IEEE 802.16e
communication system according to an embodiment of the present invention;
FIG. 5 is a diagram illustrating an interleaving operation for a systematic
symbol stream and a parity symbol stream output from a CTC coder in an IEEE
802.16e communication system according to an embodiment of the present
invention;
FIG. 6 is a block diagram illustrating a transmitter in an IEEE 802.16e
communication system according to an embodiment of the present invention; and
FIG. 7 is a flow diagram illustrating an insertion operation of pilot sub-

carriers performed by the first pilot sub-carrier inserter and the second pilot sub-
carrier inserter of FIG. 6.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Preferred embodiments of the present invention will be described in
detail herein below with reference to the accompanying drawings. In the
following description, particular items are shown, but these are provided for
helping the general understanding of the present invention. Accordingly, it will be
understood by those skilled in the art that the present invention can be embodied
even without these particular items.
In the following description of the present invention, a detailed
description of known functions and configurations incorporated herein will be
omitted when it may obscure the subject matter of the present invention.
The present invention proposes an apparatus and a method for
transmitting pilot signals, which are reference signals, in a Broadband Wireless
Access (BWA) communication system using a plurality of transmit antennas.
More specifically, the present invention proposes an apparatus and a method for
transmitting pilot signals using a Convolutional Turbo Coding (CTC) scheme in a
BWA communication system using a plurality of transmit antennas.
As one example, the present application describes an Institute of
Electrical and Electronics Engineers (IEEE) 802.16e communication system for
convenience of description, but a scheme proposed by the present invention can
also be applied to other communication systems. The IEEE 802.16e
communication system uses an Orthogonal Frequency Division Multiplexing
(OFDM) scheme/an Orthogonal Frequency Division Multiple Access (OFDMA)
scheme in order to support a broadband transmission network for a physical
channel of the wireless Metropolitan Area Network (MAN) system.
FIG. 2 is a diagram schematically illustrating a data transmission
operation of a transmitter using a plurality of transmit antennas in the IEEE
802.16e communication system according to an embodiment of the present

invention.
Referring to FIG. 2, it is assumed that a transmitter, e.g., a Base Station
(BS) 200, uses a plurality of transmit antennas, e.g., two transmit antennas, i.e.,
a first transmit antenna(ANT#l) 201 and a second transmit antenna(ANT#2) 202.
The first transmit antenna 201 and the second transmit antenna 202
simultaneously transmit data. The data transmitted through the first transmit
antenna 201 and the second transmit antenna 202 may be varied according to a
coding scheme used by the BS 200.
Table 1 below shows transmission data according to transmission timing
when the BS 200 uses a Space Time Block Code (STBC) coding scheme.

Referring to table 1, if data Si and S2 are inputted, the data S] is
transmitted through the first transmit antenna 201 and the data S2 is transmitted
through the second transmit antenna 202 at a timing point t. At a timing point
(t+1), the next transmission time, the data -S2* is transmitted through the first
transmit antenna 201 and the data S1* is transmitted through the second transmit
antenna 202.
As described above, the BS 200 transmits different coded symbols for the
same data through the first transmit antenna 201 and the second transmit antenna
202 using the STBC coding scheme at the different timing points, i.e., the timing
point t and the timing point (t+1), such that an MS can estimate radio channel
conditions according to each transmit antenna.
FIG. 3 is a diagram illustrating a mini sub-channel structure in the IEEE
802.16e communication system using a plurality of transmit antennas according
to an embodiment of the present invention. The mini sub-channel structure of FIG.

3 illustrates a mini sub-channel structure when the BS uses the two transmit
antennas as described in FIG. 2. In order to estimate radio channel conditions of
each of the two transmit antennas, specific pilot signals must be transmitted
according to each transmit antenna. However, if pilot tones for identifying the two
transmit antennas are added to the mini sub-channel structure, when a Single
Input Single Output (SISO) scheme as described in FIG. 1 in the prior art is used,
a ratio of the pilot tones with respect to the total tones increases. As indicated
above, it is noted that the tone is used together with the sub-carrier for
convenience of description.
Because data throughput deteriorates as the ratio of the pilot tones with
respect to the total tones increases, the present invention punctures a
predetermined number of data tones and inserts pilot tones into positions of the
punctured data tones, in order to add the pilot tones for identifying the transmit
antennas, while preventing a data rate from deteriorating. Hereinafter, an
operation for puncturing the data tones and inserting the pilot tones into the
positions of the punctured data tones will be described.
Referring to FIG. 3, a scheme for mapping a tone to a mini sub-channel
transmitted through the first transmit antenna and a scheme for mapping a tone to
a mini sub-channel transmitted through the second transmit antenna are different.
The mini sub-channel transmitted through the first transmit antenna comprises
two pilot tones 301 and 303. Herein, data should not be transmitted through tones
306 and 308 in the mini sub-channel transmitted through the second transmit
antenna 202, which are located in the same positions as those in which the pilot
tones 301 and 303 exist.
The mini sub-channel transmitted through the second transmit antenna
comprises two pilot tones 305 and 307. Herein, data should not be transmitted
through tones 302 and 304 in the mini sub-channel transmitted through the first
transmit antenna 201, which are located in the same positions as those in which
the pilot tones 305 and 307 exist.
When the pilot tones and the data tones are constructed in this way, it is
possible to estimate channel conditions experienced by signals transmitted

through each of the transmit antennas. However, if mini sub-channel signals are
transmitted in this way when multiple transmit antennas are used, data
transmission efficiency may deteriorate and it is difficult to reliably transmit
information data because the coded information data, i.e., the coded symbols,
must be punctured, as described in the prior art.
Accordingly, the present invention encodes information data using a CTC
encoding scheme, and enables a parity symbol, which is a coded symbol
corresponding to a parity from among the coded symbols, to be located in a tone
corresponding to a pilot tone transmitting pilot signals through a different
transmit antenna instead of a corresponding transmit antenna, such that the parity
symbol is truncated instead of a data symbol. Further, a null tone is inserted into a
position from which the data symbol has been truncated. That is, null data is
transmitted through a tone of the position from which the data symbol has been
truncated.
FIG. 4 is a diagram illustrating a CTC encoder in the IEEE 802.16e
communication system according to an embodiment of the present invention.
Herein, it is assumed that the CTC coder has a coding rate of 1/3 (R = 1/3).
Referring to FIG. 4, when information data streams A and B are input, the
CTC encoder outputs the information data streams A and B (401). The
information data streams A and B output from the CTC encoder comprise
systematic symbols.
After receiving the information data streams A and B, the CTC encoder
interleaves the received information data streams A and B through a CTC
interleaver 410 and outputs the interleaved signals to a constituent encoder 420.
The CTC interleaver 410 is connected to a switch 430 that enables the interleaved
signals to be sequentially output through the constituent encoder 420 as two pairs
of parity symbols. When the constituent encoder 420 encodes the information
data streams A and B, the switch 430 performs a switching operation to input the
signals output from the CTC interleaver 410 to the constituent encoder 420.
FIG. 4 illustrates the two pairs of parity symbols (Y1 W1 and (Y2, W2)

sequentially output from the constituent encoder 420. Accordingly, the coding rate
R of 1/3 is actually satisfied.
The constituent encoder 420 comprises five adders, i.e., a first adder
421, a second adder 423, a third adder 425, a fourth adder 427, and a fifth adder
428, and three delayers, i.e., a first delayer 422, a second delayer 424, and a third
delayer 426. Signals Y1 and Y2 are sequentially output from the fourth adder 427,
and signals W1 and W2 are sequentially output from the fifth adder 428, thereby
generating the two pairs of parity symbols (Y1, W1) and (Y2, W2)(402).
The symbols coded through the CTC encoder in this way are interleaved
again, which will be described in more detail with reference to FIG. 5.
FIG. 5 is a diagram schematically illustrating an interleaving operation for
the systematic symbol stream and the parity symbol stream output from the CTC
encoder in the IEEE 802.16e communication system according to an embodiment
of the present invention. Referring to FIG. 5, an AB sub-block 500 is obtained by
connecting, in serial, two systematic symbol streams, i.e., a systematic symbol
stream A and a systematic symbol stream B. A Y1 sub-block 501 is a parity
symbol stream Y1, a Y2 sub-block 502 is a parity symbol stream Y2, a W1 sub-
block 503 is a parity symbol stream W1, and a W2 sub-block 504 is a parity
symbol stream W2. The Y1 sub-block 501 and the Y2 sub-block 502 represent
symbol streams output from the fourth adder 427 as described in FIG. 4, and the
W1sub-block 503 and the fifth adder 428 as described in FIG. 4. These symbol streams output as
described above are interleaved by the following scheme:
(1) the symbols comprised in a systematic part are interleaved in the
systematic part;
(2) the parity symbols are interleaved between the parity symbol streams
output from the same adder; and
(3) in the interleaving between parity symbols, the parity symbols are
arranged in such a manner that they are alternately taken one-by-one from the two
parity symbol streams.
That is, the AB sub-block 500 is interleaved in a sub-block interleaver

510. The Y1 sub-block 501 and the Y2 sub-block 502 are interleaved in a sub-
block interleaver 511 and a sub-block interleaver 512. The W1 sub-block 503 and
the W2 sub-block 504 are interleaved in a sub-block interleaver 513 and a sub-
block interleaver 514.
The symbol streams interleaved by the interleaving scheme as described
above are generated as a systematic symbol stream or parity symbol streams. That
is, the AB sub-block 500 is interleaved so as to be generated as a final systematic
symbol stream 530. The Y1 sub-block 501 and the Y2 sub-block 502 are
interleaved so as to be generated as a parity symbol stream 531. The W1 sub-block
503 and the W2 sub-block 504 are interleaved so as to be generated as another
parity symbol stream 532. Accordingly, the final coding rate is 1/3.
When the symbol streams are transmitted, the symbol streams are
transmitted in an order as illustrated in FIG. 5. That is, the systematic symbol
stream 530 is transmitted for the first time and the parity symbol stream 532 is
transmitted for the last time. The CTC encoder as described above has a
characteristic in which it transmits a symbol stream, which represents the most
important information, i.e., important information having the highest priority, for
the first time. Accordingly, when using the CTC encoder, the CTC encoder has a
better coding performance when the puncture is performed for the last symbols
output from the CTC encoder than when randomly puncturing data. That is,
when the CTC encoder is used, data should not be randomly punctured. It is
necessary to remove data from the last symbols output from the CTC encoder to
improve the coding performance.
FIG. 6 is a block diagram illustrating a transmitter in the IEEE 802.16e
communication system according to an embodiment of the present invention. The
transmitter comprises a CTC encoder 601, a modulator 602, an STBC encoder
603, a first pilot sub-carrier inserter 604-1, a second pilot sub-carrier inserter 604-
2, a first sub-carrier mapper 605-1, a second sub-carrier mapper 605-2, a first
Inverse Fast Fourier Transform (IFFT) unit 606-1, a second IFFT unit 606-2, a
first filter 607-1, a second filter 607-2, a first Digital-to-Analog Converter (DAC)
608-1, a second DAC 608-2, a first Radio Frequency (RF) processor 609-1, a
second RF processor 609-2, a first transmit antenna ANT#1, and a second

transmit antenna ANT#2.
If information data streams to be transmitted to the transmitter are input,
the information data streams are transferred to the CTC encoder 601. The CTC
encoder 601 codes the information data streams using a CTC encoding scheme
and outputs the coded symbol streams to the modulator 602. The modulator 602
inputs the coded symbol streams output from the CTC encoder 601, modulates
the input symbol streams using a predetermined modulation scheme, e.g., a
Quadrature Phase Shift Keying (QPSK) scheme, and outputs the modulated
symbol streams to the STBC encoder 603.
The STBC encoder 603 inputs the signals output from the modulator 602
and encodes the input signals using the STBC scheme. The STBC encoder 603
outputs a coded symbol stream, which is to be transmitted through the first
transmit antenna, to the first pilot sub-carrier inserter 604-1, and outputs a coded
symbol stream, which is to be transmitted through the second transmit antenna, to
the second pilot sub-carrier inserter 604-2.
The first pilot sub-carrier inserter 604-1 inputs the signals output from the
STBC encoder 603, inserts pilot sub-carriers to be transmitted through the first
transmit antenna, and outputs signals including the pilot sub-carriers to the first
sub-carrier mapper 605-1. The first pilot sub-carrier inserter 604-1 constructs a
mini sub-channel as described in FIG. 3. Because this operation has been
described in detail with reference FIG. 3 above, a detailed description will be
omitted here.
The first sub-carrier mapper 605-1 maps the signals output from the first
pilot sub-carrier inserter 604-1 according to the types of a sub-carrier to be
applied to the transmitter, and outputs the mapped signals to the first IFFT unit
606-1. The first IFFT unit 606-1 performs an IFFT for the signals output from the
first sub-carrier mapper 605-1 in order to generate signals on a time domain, and
outputs the generated signals to the first filter 607-1.
The first filter 607-1 inputs and filters the signals output from the first
IFFT unit 606-1 and outputs the filtered signals to the first DAC 608-1. The first

DAC 608-1 converts the signals output from the first filter 607-1 into analog
signals and outputs the analog signals to the first RF processor 609-1. The first
RF processor 609-1, including a front end unit, etc., RF-processes the analog
signals output from the first DAC 608-1, and transmits the processed signals
through the first transmit antenna.
The second pilot sub-carrier inserter 604-2 inputs the signals output from
the STBC encoder 603, inserts pilot sub-carriers to be transmitted through the
second transmit antenna, and outputs signals including the pilot sub-carriers to the
second sub-carrier mapper 605-2. The second pilot sub-carrier inserter 604-2
constructs a mini sub-channel as described in FIG. 3. As indicated above, because
this operation has been described in detail in FIG. 3, a detailed description will be
omitted here.
The second sub-carrier mapper 605-2 maps the signals output from the
second pilot sub-carrier inserter 604-2 according to the types of a sub-carrier to be
applied to the transmitter, and outputs the mapped signals to the second IFFT unit
606-2. The second IFFT unit 606-2 performs an IFFT for the signals output from
the second sub-carrier mapper 605-2 in order to generate signals on a time
domain, and outputs the generated signals to the second filter 607-2.
The second filter 607-2 inputs and filters the signals output from the
second IFFT unit 606-2 and outputs the filtered signals to the second DAC 608-2.
The second DAC 608-2 converts the signals output from the second filter 607-2
into analog signals and outputs the analog signals to the second RF processor
609-2. The second RF processor 609-2, including a front end unit, etc., RF-
processes the analog signals output from the second DAC 608-2, and transmits
the processed signals through the second transmit antenna.
FIG. 7 is a flow diagram illustrating an insertion operation of the pilot
sub-carriers performed by the first pilot sub-carrier inserter 604-1 and the second
pilot sub-carrier inserter 604-2. However, for convenience of description, the
insertion operation will only be described with reference to the operation of the
first pilot sub-carrier inserter 604-1.

Referring to FIG. 7, in step 701, the first pilot sub-carrier inserter 604-1
inputs the signals output from the STBC encoder 603 and performs a data
truncation according to the structure of a mini sub-channel to be transmitted
through the first transmit antenna. The data truncation is performed for parity
symbols, instead of systematic symbols, by using the characteristics of the CTC
encoding scheme in order to prevent performance deterioration, as described
above. Further, in the data truncation, it is inevitably necessary to consider
insertion of pilot signals and sub-carriers that cannot transmit data due to
transmission of the pilot signals through another transmit antenna, i.e., the second
transmit antenna.
In step 702, the first pilot sub-carrier inserter 604-1 inserts pilot signals to
be transmitted through the first transmit antenna into a corresponding pilot sub-
carrier. The insertion of the pilot signals is performed for a sub-carrier without
data as described above. In step 703, the first pilot sub-carrier inserter 604-1
rearranges symbols, including the pilot signals, from which data is truncated, and
outputs the symbols to the first sub-carrier mapper 605-1. Thereafter, the
procedure ends.
Herein, the symbols are rearranged to represent the mini sub-channel
structure.
According to the present invention, as described above, when an IEEE
802.16e communication system uses a plurality of transmit antennas, pilot signals
for identifying the transmit antennas are transmitted, such that the estimation
performance for radio channel conditions can be maximized. Further, a data
truncation scheme is used when the pilot signals for identifying the transmit
antennas are transmitted, so that estimation for radio channel conditions can be
performed, which can minimize system capacity reduction, while maintaining a
data rate.
While the present invention has been shown and described with reference
to certain preferred embodiments thereof, it will be understood by those skilled in
the art that various changes in form and details may be made therein without
departing from the spirit and scope of the present invention as defined by the

appended claims.

We Claim:
1. A method for transmitting reference signals in a Broadband Wireless
Access (BWA) communication system , the method comprising the steps
of:
transmitting first reference signals (301,303) for identifying a first
transmit antenna using a first predetermined number of sub-carriers in
a first mini sub-channel, the first reference signals being transmitted
through the first transmit antenna, and the first mini sub-channel
being occupied by a predetermined time domain and sub-frequency
domains of a second predetermined number of sub-carriers; and
transmitting second reference signals (305,307) for identifying a
second transmit antenna using the first predetermined number of the
sub-carriers in a second mini sub-channel, the second reference
signals being transmitted through the second transmit antenna, and

the second mini sub-channel being occupied by the predetermined time
domain and the sub-frequency domains of the second predetermined
number of sub-carriers,
wherein first sub-carriers, through which the first reference signals are
transmitted, include sub-frequency domains different from sub-frequency
domains occupied by second sub-carriers, through which the second
reference signals are transmitted,
wherein transmitting the first reference signals further comprises
transmitting null data (302,304) in the first mini sub-channel using sub-
carriers including sub-frequency domains, that are identical to the sub-
frequency domains occupied by the second sub-carriers ,
wherein transmitting the second reference signals further comprises
transmitting null data (306,308) in the second mini sub-channel using
sub-carriers including sub-frequency domains that are identical to the sub-
frequency domains occupied by the first sub-carriers .

2. The method as claimed in claim 1, comprising transmitting information
data in the first mini sub-channel using remaining sub-carriers excluding
sub-carriers including the sub-frequency domains that are identical to
the sub-frequency domains occupied by the second sub-carriers, among
sub-carriers excluding the first sub-carriers in the first mini sub-channel.
3. The method as claimed in claim 1, comprising transmitting information
data in the second mini sub-channel using remaining sub-carriers
excluding sub-carriers including the sub-frequency domains that are
identical to the sub-frequency domains occupied by the first sub-
carriers, among sub-carriers excluding the second sub-carriers in the
second mini sub-channel.
4. The method as claimed in claim 1, wherein transmitting the first
reference signals comprises transmitting first coded symbols through the
first transmit antenna,
wherein transmitting the second reference signals further comprises
transmitting second coded symbols through the second transmit antenna,

wherein the first coded symbols and the second coded symbols are generated
by coding third coded symbols according to a first coding scheme, the third
coded symbols being generated by coding information data to be transmitted
according to a second coding scheme,
wherein the first coded symbols inserted into sub-carriers truncated
according to a truncation scheme, which exclude sub-carriers including the
first reference signals and the null data in the first mini sub-channel, and
wherein the second coded symbols inserted into sub-carriers truncated
according to the truncation scheme, which exclude sub-carriers including the
second reference signals and the null data in the second mini sub-channel.
5. The method as claimed in claim 4, wherein the first and second
reference signals are inserted into sub-carriers that were previously
allocated to data tones before truncation by using the truncation
scheme, and
wherein the first coded symbols and the second coded symbols include
systematic symbols (401) and parity symbols (402), and only the parity
symbols are truncated according to the truncation scheme.

6. The method as claimed in claim 4, wherein the first coded symbols are
inserted into sub-carriers excluding the sub-carriers including the first
reference signals and the null data in the first mini sub-channel, in a
sequence from a coded symbol representing important information of a
highest priority to remaining coded symbols.
7. The method as claimed in claim 4, wherein the second coded symbols
are inserted into sub-carriers excluding the sub-carriers including the
second reference signals and the null data in the second mini sub-
channel, in a sequence from a coded symbol representing important
information of a highest priority to remaining coded symbols.
8. The method as claimed in claim 4, wherein the second coding scheme
includes a Convolutional Turbo Coding (CTC) scheme.
9. The method as claimed in claim 8, wherein, the first coded symbols
include systematic symbols and parity symbols, and the systematic
symbols

are first inserted when the first coded symbols are sequentially inserted into
sub-carriers excluding the sub-carriers including the first reference signals
and the null data in the first mini sub-channel.
10. The method as claimed in claim 8, wherein, the second coded symbols
include systematic symbols and parity symbols, and the systematic symbols
are first inserted when the second coded symbols are sequentially inserted
into sub-carriers excluding the sub-carriers including the second reference
signals and the null data in the second mini sub-channel.
11.The method as claimed in claim 4, wherein the first coding scheme
includes a Space Time Block Code (STBC) coding scheme.
12. An apparatus for transmitting reference signals in a Broadband Wireless
Access (BWA) communication system, the apparatus comprising:
a first transmitter for transmitting first reference signals (301,303) for
identifying a first transmit antenna using a first predetermined number of
sub-carriers in a first mini sub-channel, the first reference signals being
transmitted through the first transmit antenna, and the first mini sub-channel
being occupied by a predetermined time domain and sub-frequency domains
of a second predetermined number of sub-carriers; and

a second transmitter for transmitting second reference signals (305,307)
for identifying a second transmit antenna using the first predetermined
number of the sub-carriers in a second mini sub-channel, the second
reference signals being transmitted through the second transmit antenna,
and the second mini sub-channel being occupied by the predetermined time
domain and the sub-frequency domains of the second predetermined number
of sub-carriers,
wherein first sub-carriers, through which the first reference signals are
transmitted, include sub-frequency domains different from sub-frequency
domains occupied by second sub-carriers, through which the second
reference signals are transmitted,
wherein the first transmitter transmits null data (302,304) in the first mini
sub-channel using sub-carriers including sub-frequency domains that are
identical to the sub-frequency domains occupied by the second sub-carriers ,
wherein the second transmitter transmits null data (306,308) in the second
mini sub-channel using sub-carriers including sub-frequency domains that are
identical to the sub-frequency domains occupied by the first sub-carriers .
13. The apparatus as claimed in claim 12, wherein the first transmitter
transmits information data in the first mini sub-channel using remaining sub-
carriers excluding sub-carriers including the sub-frequency domains that are
identical to the sub-frequency domains occupied by the second sub-carriers,
among sub-carriers excluding the first sub-carriers in the first mini sub-
channel.

14. The apparatus as claimed in claim 12, wherein the second transmitter
transmits information data in the second mini sub-channel using
remaining sub-carriers excluding sub-carriers including the sub-frequency
domains that are identical to the sub-frequency domains occupied by the
first sub-carriers, among sub-carriers excluding the second sub-carriers in
the second mini sub-channel.
15. The apparatus as claimed in claim 12, comprising :
a first coder (601) for generating third coded symbols by coding
information data to be transmitted according to a first coding scheme;
a second coder (603) for coding the third coded symbols according to a
second coding scheme in order to generate first coded symbols to be
transmitted through the first transmit antenna and second coded symbols to
be transmitted through the second transmit antenna,
wherein the first transmitter transmits the first coded symbols through the
first transmit antenna, and the second transmitter transmits the second
coded symbols through the second transmit antenna,
wherein the first coded symbols inserted into sub-carriers truncated
according to a truncation scheme, which exclude sub-carriers including the
first reference signals and the null data in the first mini sub-channel, and


wherein the second coded symbols inserted into sub-carriers truncated
according to the truncation scheme, which exclude sub-carriers including the
second reference signals and the null data in the second mini sub-channel.
16. The apparatus as claimed in claim 15, wherein the first and second reference
signals are inserted into sub-carriers that were previously allocated to data tones
before truncation by using the truncation scheme, and
wherein the first coded symbols and the second coded symbols include
systematic symbols (401) and parity symbols (402), and only the parity symbols
are truncated according to the truncation scheme.
17.The apparatus as claimed in claim 15, wherein the first coded symbols are
inserted into sub-carriers excluding the sub-carriers including the first reference
signals and the null data in the first mini sub-channel, in a sequence from a
coded symbol representing important information of a highest priority to
remaining coded symbols.
18.The apparatus as claimed in claim 15, wherein the second coded symbols are
inserted into sub-carriers excluding the sub-carriers including the second
reference signals and the null data in the second mini sub-channel, in a
sequence from a coded symbol representing important information of a highest
priority to remaining coded symbols.

19.The apparatus as claimed in claim 15, wherein the first coding scheme
comprises a Convolutional Turbo Coding (CTC) scheme.
20.The apparatus as claimed in claim 19, wherein the first coded symbols
comprise systematic symbols and parity symbols, and the systematic
symbols are first inserted when the first coded symbols are sequentially
inserted into sub-carriers excluding the sub-carriers including the first
reference signals and the null data in the first mini sub-channel.
21.The apparatus as claimed in claim 19, wherein the second coded symbols
include systematic symbols and parity symbols, and the systematic
symbols first inserted when the second coded symbols are sequentially
inserted into sub-carriers excluding the sub-carriers including the second
reference signals and the null data in the second mini sub-channel.
22.The apparatus as claimed in claim 15, wherein the second coding scheme
comprises a Space Time Block Code (STBC) coding scheme.



ABSTRACT
TITLE:METHODS AND APPARATUSES FOR TRANSMITTING REFERENCE
SIGNALS IN A BROADBAND WIRELESS ACCESS COMMUNICATION SYSTEM
The invention relates to a method for transmitting reference signals in a
Broadband Wireless Access (BWA) communication system , the method
comprising the steps of transmitting first reference signals (301,303) for
identifying a first transmit antenna using a first predetermined number of sub-
carriers in a first mini sub-channel, the first reference signals being transmitted
through the first transmit antenna, and the first mini sub-channel being occupied
by a predetermined time domain and sub-frequency domains of a second
predetermined number of sub-carriers; and transmitting second reference
signals (305,307) for identifying a second transmit antenna using the first
predetermined number of the sub-carriers in a second mini sub-channel, the
second reference signals being transmitted through the second transmit antenna,
and the second mini sub-channel being occupied by the predetermined time
domain and the sub-frequency domains of the second predetermined number of
sub-carriers, wherein first sub-carriers, through which the first reference signals
are transmitted, include sub-frequency domains different from sub-frequency
domains occupied by second sub-carriers, through which the second reference
signals are transmitted, wherein transmitting the first reference signals further
comprises transmitting null data (302,304) in the first mini sub-channel using
sub-carriers including sub-frequency domains, that are identical to the sub-
frequency domains occupied by the second sub-carriers , wherein transmitting
the second reference signals further comprises transmitting null data (306,308)
in the second mini sub-channel using sub-carriers including sub-frequency
domains that are identical to the sub-frequency domains occupied by the first
sub-carriers.

Documents:

03449-kolnp-2006 abstract.pdf

03449-kolnp-2006 claims.pdf

03449-kolnp-2006 correspondence others.pdf

03449-kolnp-2006 description(complete).pdf

03449-kolnp-2006 drawings.pdf

03449-kolnp-2006 form-1.pdf

03449-kolnp-2006 form-2.pdf

03449-kolnp-2006 form-3.pdf

03449-kolnp-2006 form-5.pdf

03449-kolnp-2006 gpa.pdf

03449-kolnp-2006 international publication.pdf

03449-kolnp-2006 international search authority report.pdf

03449-kolnp-2006 pct others document.pdf

03449-kolnp-2006 pct request form.pdf

03449-kolnp-2006-correspondence-1.1.pdf

03449-kolnp-2006-form-18.pdf

3449-KOLNP-2006-(26-03-2012)-CORRESPONDENCE.pdf

3449-KOLNP-2006-ABSTRACT-1.1.pdf

3449-KOLNP-2006-ABSTRACT.pdf

3449-KOLNP-2006-AMANDED CLAIMS-1.1.pdf

3449-KOLNP-2006-AMANDED CLAIMS.pdf

3449-KOLNP-2006-CORRESPONDENCE 1.3.pdf

3449-KOLNP-2006-CORRESPONDENCE-1.1.pdf

3449-KOLNP-2006-CORRESPONDENCE-1.2.pdf

3449-KOLNP-2006-CORRESPONDENCE.pdf

3449-KOLNP-2006-DESCRIPTION (COMPLETE)-1.1.pdf

3449-KOLNP-2006-DESCRIPTION (COMPLETE).pdf

3449-KOLNP-2006-DRAWINGS.pdf

3449-KOLNP-2006-ENGLISH TRANSLATION.pdf

3449-KOLNP-2006-EXAMINATION REPORT REPLY RECIEVED.pdf

3449-KOLNP-2006-EXAMINATION REPORT.pdf

3449-KOLNP-2006-FORM 1.pdf

3449-KOLNP-2006-FORM 18.pdf

3449-KOLNP-2006-FORM 2-1.1.pdf

3449-KOLNP-2006-FORM 2.pdf

3449-KOLNP-2006-FORM 3 1.1.pdf

3449-KOLNP-2006-FORM 3 1.3.pdf

3449-KOLNP-2006-FORM 3-1.2.pdf

3449-KOLNP-2006-FORM 5.pdf

3449-KOLNP-2006-GPA.pdf

3449-KOLNP-2006-GRANTED-ABSTRACT.pdf

3449-KOLNP-2006-GRANTED-CLAIMS.pdf

3449-KOLNP-2006-GRANTED-DESCRIPTION (COMPLETE).pdf

3449-KOLNP-2006-GRANTED-DRAWINGS.pdf

3449-KOLNP-2006-GRANTED-FORM 1.pdf

3449-KOLNP-2006-GRANTED-FORM 2.pdf

3449-KOLNP-2006-GRANTED-SPECIFICATION.pdf

3449-KOLNP-2006-OTHERS 1.1.pdf

3449-KOLNP-2006-OTHERS 1.4.pdf

3449-KOLNP-2006-OTHERS-1.2.pdf

3449-KOLNP-2006-OTHERS-1.3.pdf

3449-KOLNP-2006-PETITION UNDER RULE 137-1.1.pdf

3449-KOLNP-2006-PETITION UNDER RULE 137.pdf

3449-KOLNP-2006-REPLY TO EXAMINATION REPORT 1.1.pdf

abstract-03449-kolnp-2006.jpg


Patent Number 253072
Indian Patent Application Number 3449/KOLNP/2006
PG Journal Number 26/2012
Publication Date 29-Jun-2012
Grant Date 22-Jun-2012
Date of Filing 21-Nov-2006
Name of Patentee SAMSUNG ELECTRONICS CO.LTD.
Applicant Address 416, MAETAN-DONG, YEONGTONG-GU SUWON-SI, GYEONGGI-DO
Inventors:
# Inventor's Name Inventor's Address
1 Jeong-Tae OH #104-407, Samick APT., Pungdeokcheon-dong, Yongin-si, Gyeonggi-do,
2 Kyun-Byoung KO #506-701, Baengmamaeul 5-danji APT., Madu 1-dong, ilsan-gu, Goyang-si, Gyeonggi-do
3 Seung-Joo MAENG #704-1504, Jeongdeunmaeul Hanjin 7-danji APT., Jeongja-dong, Bundang-gu, Seongnam-si, Gyeonggi-do
4 Jae-Ho JEON #121-1003, Park Town Samick APT., 54, Sunae-dong, Bundang-gu, Seongnam-si, Gyeonggi-do
5 Pan-Yuh JOO #104-1002, Yehyeonmaeul Hyundai Home Town, Seocheon-ri, Giheung-eup, Yongin-si, Gyeonggi-do
6 Chan-Byoung CHAE #104-1701, Byucksan APT., Jeji 2-dong, Dongdaemun-gu, Seoul
7 Hong-Sil JEONG 1251-3, Maetan-dong, Yeongtong-gu, Suwon-si, Gyeonggi-do
8 Sung-Ryul YUN #307, 1253-3, Maetan 3-dong, Yeongtong-gu, Suwon-si, Gyeonggi-do
9 Won-Il ROH #112-904, Sin LG 1-cha Village, Sinbong-dong, Yongin-si, Gyeonggi-do,
PCT International Classification Number H04J 11/00
PCT International Application Number PCT/KR05/002183
PCT International Filing date 2005-07-07
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 52787/2004 2004-07-07 Republic of Korea