Indian Patents
Title of Invention

METHOD FOR UPLINK TRANSMISSION IN OFDM(A) SYSTEM
Abstract A method for uplink transmission in an OFDMA system is provided. The subcarrier transmission method includes arranging 4 pilot REs at different positions of a frequency axis in a basic unit when the basic unit includes 4 subcarriers on the frequency axis and 6 OFDM(A) symbols in a time axis, arranging data REs at remaining positions of the basic unit, and transmitting the basic unit to a receiving end.
Full Text METHOD FOR UPLINK TRANSMISSION IN OFDM (A) SYSTEM
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a wireless
communication system, and more particularly, to a method for
uplink transmission in an OFDM(A) wireless communication
system.
Discussion of the Related Art
A current IEEE 802.16e system uses a tile and pilot
structure as shown in FIG. 1 as an uplink Partial Usage of
Subchannel (PUSC) structure. One transmit antenna is
considered in the structure of FIG. 1. This uplink PUSC
basic unit structure has a pilot overhead of 33.33%. In Fig.
1, the pilot and data subcarriers refer to resource elements
(REs) allocated for pilot and data respectively. Each RE
represents a time-freauency resource defined by one OFDM(A)
symbol and one subcarrier. In the following description, the
terms "pilot subcarrier" and "data subcarrier" can be
interchanged with the terms "pilot RE" and "data RE"
respectively.
Since only one transmit antenna is considered in the
uplink tile structure used in the current IEEE 802.16e system,
the uplink PUSC basic unit structure has a pilot overhead of
33.33%. Thus, the ratio of pilot overhead to data is
significant. Such pilot overhead reduces link throughput,
causing a reduction in system performance. When an extended
basic unit is employed as in IEEE 802.16m, one issue is to
reduce pilot overhead.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a
method for uplink transmission in an OFDM(A) system that
substantially obviates one or more problems due to
limitations and disadvantages of the related art.
An object of the present invention is to provide an
uplink transmission method which can reduce pilot overhead
and guarantee channel estimation performance even when the
size of a basic unit for uplink has been extended in a time
axis.
Another object of the present invention is to provide an
uplink transmission method which guarantees backward
compatibility for an IEEE 802.16e system.
Additional advantages, objects, and features of the
invention will be set forth in part in the description which
follows and in part will become apparent to those having
ordinary skill in the art upon examination of the following
or may be learned from practice of the invention. The
objectives and other advantages of the invention may be
realized and attained by the structure particularly pointed
out in the written description and claims hereof as well as
the appended drawings.
In legacy IEEE 802.16e system, an uplink PUSC tile
contains four contiguous subcarriers by three contiguous
OFDM(A) symbols. The legacy IEEE 802.16e system applies
permutation to distribute the uplink PUSC tiles within the
corresponding frequency band in the procedure of mapping the
uplink PUSC tiles to physical subcarriers. In particular,
the permutation method configures every three OFDM(A) symbols
to have the same logical tile index, whereby the uplink PUSC
tiles can be spread within corresponding frequency band.
Such permutation method could be easily modified for an
extended tile structure by configuring multiplies of three
OFDM(A) symbols, e.g. six, nine or twelve OFDM(A) symbols,
which is contiguous in time domain and is within the same
physical frequency band to have the same logical tile index.
As such, the permutation method of the legacy IEEE 802.16e
system could be extended to distribute radio resource in
units of multiplies of three OFDM(A) symbols. Therefore it
is preferable that IEEE 802.16m system under discussion forms
uplink tile with four subcarrier by multiplies of three
OFDM(A) symbols in case of supporting the legacy IEEE 802.16e
system via frequency division multiplexing (FDM).
In IEEE 802.16m system under discussion, basic frame
structure includes a 20ms superframe supporting 5 MHz,8.75
MHz 10 MHz, or 20 MHz bandwidth. Each superframe is divided
into four equally-sized 5 ms radio frames and begins with the
superframe header (SFH). Each 5 ms radio frame further
consists of eight subframes. A subframe shall be assigned
for either DL or UL transmission. There are three types of
subframes depending on the size of cyclic prefix, i.e.
subframe consisting of five, six or seven OFDM(A) symbols.
The subframe carries smaller resource units with various
types/sizes. The basic frame structure is applied to FDD and
TDD duplexing schemes.
In one aspect of the present invention, a method of
transmitting a basic unit in uplink is provided, the method
comprising: arranging 4 pilot REs at different positions of a
frequency axis in a basic unit when the basic unit contains 4
subcarriers by 6 or more OFDM (A) symbols; arranging data REs
at remaining positions of the basic unit; and transmitting
the basic unit to a receiving end. The receiving end
includes a base station (BS).
In the step of arranging the 4 pilot REs, the 4 pilot
REs may be arranged in pair such that two pilot REs of each
pair are arranged at the same position on the time axis.
In the step of arranging the 4 pilot REs, two or more
pilot REs among the 4 pilot REs may be arranged at edge
positions of the basic unit.
In another aspect of the present invention, a method of
transmitting a basic unit in uplink is provided, the method
comprising: arranging 4 pilot REs in pairs such that two
pilot REs of each pair are arranged at the same position of a
frequency axis in a basic unit when the basic unit contains 4
subcarriers by 6 or more OFDM(A) symbols; arranging data REs
at remaining positions of the basic unit; and transmitting
the basic unit to a receiving end.
In the step of arranging the 4 pilot REs, the 4 pilot
REs may be arranged at different positions on the time axis.
In the step of arranging the 4 pilot REs, the 4 pilot
REs may be arranged in pairs such that two pilot REs of each
pair are arranged at the same position on the time axis.
In the step of arranging the 4 pilot REs, two or more
pilot REs among the 4 pilot REs may be arranged at edge
positions of the basic unit.
In the step of arranging the 4 pilot REs, two or more
pilot REs among the 4 pilot REs may be arranged at non-edge
positions of the basic unit.
In another aspect of the present invention, a method of
transmitting a basic unit in uplink is provided, the method
comprising: arranging 3 pilot REs at different positions on a
time axis in a basic unit when the basic unit contains 4
subcarriers by 5 or more OFDM(A) symbols; arranging data REs
at remaining positions of the basic unit, and transmitting
the basic unit to a receiving end.
In the step of arranging the 3 pilot REs, a pair of
pilot REs among the 3 pilot REs may be arranged at the same
position on the frequency axis and the remaining pilot RE may
be arranged at a position, different from that of the pair of
pilot REs, on the frequency axis.
In the step of arranging the 3 pilot REs, the pair of
pilot REs and the remaining pilot REs may be arranged at most
distant positions on the frequency axis.
In another aspect of the present invention, a method of
transmitting a basic unit in uplink is provided, the method
comprising: arranging 6 pilot REs over all positions in . a
frequency axis of a basic unit when the basic unit contains 4
subcarriers by 9 or more OFDM(A) symbols; arranging data REs
at remaining positions of the basic unit; and transmitting
the basic unit to a receiving end.
In another aspect of the present invention, a method of
transmitting a basic unit in uplink is provided, the method
comprising: arranging 6 pilot REs at both ends of a frequency
axis of a basic unit when the basic unit contains 4
subcarriers by 9 or more OFDM (A) symbols; arranging data REs
at remaining positions of the basic unit; and transmitting
the basic unit to a receiving end.
In another aspect of the present invention, a method of
transmitting a basic unit in uplink is provided, the method
comprising: arranging 2 pilot REs at different positions in a
frequency axis and a time axis in a basic unit when the basic
unit contains 4 subcarriers by 6 OFDM(A) symbols; arranging
data REs at remaining positions of the basic unit; and
transmitting the basic unit to a receiving end.
In another aspect of the present invention, a method of
transmitting a basic unit in uplink is provided, the method
comprising: arranging 4 pilot REs at different positions in a
frequency axis and a time axis in a basic unit when the basic
unit contains 4 subcarriers by 12 OFDM(A) symbols; arranging
data REs at remaining positions of the basic unit; and
transmitting the basic unit to a receiving end.
In another aspect of the present invention, a method of
transmitting a basic unit in uplink by a mobile station (MS)
in an Orthogonal Frequency Division Multiple Access (OFDMA)
wireless communication system is provided, the method
comprising: forming the basic unit which size is 4
subcarriers by 6 OFDMA symbols, the basic unit containing a
plurality of pilot and data resource elements (REs);
configuring the pilot REs for single antenna in the basic
unit at intervals of 3 subcarriers in a frequency axis and at
intervals of 1 or 4 OFDMA symbols in a time axis; and
transmitting the basic unit in uplink, wherein the RE is a
time-frequency resource defined by one OFDMA symbol and one
subcarrier, wherein the pilot and data REs are arranged in
the basic unit as in Pattern Table 1 expressed as follows:

where "P" indicates the pilot RE, "-" indicates the data
RE, "s" indicates an OFDMA symbol index, and "SC" indicates a
subcarrier index.
Alternatively, a method of uplink transmitting a
subframe containg a plurality of basic units by a mobile
station (MS) in an Orthogonal Frequency Division Multiple
Access (OFDMA) wireless communication system is provided, the
method comprising: forming each basic unit which size is 4
subcarriers by 6 OFDMA symbols, the each basic unit
containing a plurality of pilot and data resource elements
(REs); configuring the pilot REs for single antenna in the
each basic unit at intervals of 3 subcarriers in a frequency
axis and at intervals of 1 or 4 OFDMA symbols in a time axis;
and transmitting the subframe in uplink, wherein the RE is a
time-frequency resource defined by one OFDMA symbol and one
subcarrier, wherein the pilot and data REs are arranged in
the each basic unit as in Pattern Table 1 expressed as
follows:

where "P" indicates the pilot RE, "-" indicates the data
RE, "s" indicates an OFDMA symbol index, and "SC" indicates a
subcarrier index.
The subframe contains 6 OFDM(A) symbols. In case that
the subframe contains 5 or 7 OFDM(A) symbols depending on the
cyclic prefix size, the above Pattern Table 1 may be modified
accordingly by excluding or adding one OFDM(A) symbol in such
a manner that the modified Pattern Table still maintains
allowable channel estimation ability.
The basic unit may be an uplink tile. In particular,
the basic unit may be an uplink partial usage of subchannel
(PUSC) tile. The basic unit may be an uplink IEEE 802.16m
partial usage of subchannel (PUSC) tile. The basic unit may
be distributed Resource Unit(DRU) for 16m PUSC
A certain number of the basic units may form a larger
resource unit. The certain number of the basic units includes
six basic units. The larger resource unit includes a
localized resource unit or a distributed resource unit. In
this case, the basic units forming each larger resource unit
may be contiguous in the frequency domain. Alternatively,
the basic units forming each larger resource unit may be
distributed in the frequency domain.
Locations of the pilot REs may be cyclically shifted in
the frequency domain or in the time domain.
The Pilot REs may be power boosted with power of data
REs in the same OFDMA symbol.
The method may further comprise mapping pilot and data
symbols to corresponding pilot and data REs, respectively.
The pilot and data symbols may be in the type of complex
value representing amplitude and phase. For example, the
data symbol may include a complex value representing
amplitude and phase of modulated data.
The pilot REs may be used for dedicated pilot.
In another aspect of the present invention, a method of
transmitting a basic unit in uplink by a mobile station (MS)
in an Orthogonal Frequency Division Multiple Access (OFDMA)
wireless communication system is provided, the method
comprising: forming the basic unit which size is 4
subcarriers by 6 OFDMA symbols, the basic unit containing a
plurality of pilot and data resource elements (REs);
configuring the pilot REs for multiple antennas in the basic
unit at intervals of 3 subcarriers in a frequency axis and at
intervals of 5 OFDMA symbols in a time axis; and transmitting
the basic unit in uplink, wherein the RE is a time-frequency
resource defined by one OFDMA symbol and one subcarrier,
wherein the pilot and data REs are arranged in the basic unit
as in Pattern Table 2 expressed as follows:

where "P0" and "P1" indicate respective pilot REs for
antenna ports 0 and 1, '-" indicates the data RE, "s"
indicates an OFDMA symbol index, and "SC" indicates a
subcarrier index.
Alternatively, a method of uplink transmitting a
subframe containg a plurality of basic units by a mobile
station (MS) in an Orthogonal Frequency Division Multiple
Access (OFDMA) wireless communication system is provided, the
method comprising; forming each basic unit which size is 4
subcarriers by 6 OFDMA symbols, the each basic unit
containing a plurality of pilot and data resource elements
(REs); configuring the pilot REs for multiple antennas in the
each basic unit at intervals of 3 subcarriers in a frequency
axis and at intervals of 5 OFDMA symbols in a time axis; and
transmitting the subframe in uplink, wherein the RE is a
time-frequency resource defined by one OFDMA symbol and one
subcarrier, wherein the pilot and data REs are arranged in
the each basic unit as in Pattern Table 2 expressed as
follows:
[Pattern Table 2]

where "P0" and "P1" indicate respective pilot REs for
antenna ports 0 and 1, "-" indicates the data RE, "s"
indicates an OFDMA symbol index, and "SC" indicates a
subcarrier index.
The subframe contains 6 OFDM(A) symbols. In case that
the subframe contains 5 or 7 OFDM(A) symbols depending on the
cyclic prefix size, the above Pattern Table 1 may be modified
accordingly by excluding or adding one OFDM(A) symbol in such
a manner that the modified Pattern Table still maintains
allowable channel estimation ability.
The basic unit may be an uplink tile. In particular,
the basic unit may be an uplink partial usage of subchannel
(PUSC) tile. The basic unit may be an uplink IEEE 802.15m
partial usage of subchannel (PUSC) tile. The basic unit may
be distributed Resource Unit(DRU) for 16m PUSC
A certain number of the basic units may form a larger
resource unit. The certain number of the basic units
includes six basic units. The larger resource unit includes
a localized resource unit or a distributed resource unit. In
this case, the basic units forming each larger resource unit
may be contiguous in the frequency domain. Alternatively,
the basic units formaing each larger resource unit may be
distributed in the frequency domain.
The antenna port 0 and the antenna port 1 may be
replaced with each other. Locations of the pilot REs may be
cyclically shifted in the frequency domain or in the time
domain.
The Pilot REs may be power boosted with power of data
REs in the same OFDMA symbol.
The method may further comprise mapping pilot and data
symbols to corresponding pilot and data REs, respectively.
The pilot and data symbols may be in the type of conjugate
value representing amplitude and phase. For example, the
data symbol may include a conjugate value representing
amplitude and phase of modulated data.
The pilot REs may be used for dedicated pilot.
Transmit diversity scheme or spatial multiplexing (SM)
may be independently applied to the each basic unit. The
transmit diversity scheme includes space time block code
(STBC), space frequency block code (SFBC), cyclic delay
diversity (CDD) or any combination thereor.
The sequential orders of the steps exemplified in the
above various aspects of the present invention are up to
implementation issues. Therefore the steps of the present
invention could be carried out in various order depending
manufactures unless the order is mentioned in particular.
According to the embodiments of the present invention,
it is possible to reduce pilot overhead of the OFDM(A) system
even when each basic unit for uplink has been extended on the
time axis.
In addition, since the time interval and the frequency
interval of pilot REs in the basic unit are maintained
uniform or pilot REs are distributed to facilitate channel
estimation, it is possible to guarantee the performance of
channel estimation and to improve system performance.
Further, it is possible to guarantee backward
compatibility to the legacy uplink PUSC structure of IEEE
802.16e.
It is to be understood that both the foregoing general
description and the following detailed description of the
present invention are exemplary and explanatory and are
intended to provide further explanation of the invention as
claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are included to provide
a further understanding of the invention and are incorporated
in and constitute a part of this application, illustrate
embodiment (s) of the invention and together with the
description serve to explain the principle of the invention.
In the drawings:
FIG. 1 illustrates a conventional IEEE 802.16e tile and
pilot structure.
FIG. 2A illustrates an example wherein 1Tx or 1 stream
pilots are allocated when each basic unit includes 4
subcarriers x 3 OFDM(A) symbols according to an embodiment of
the present invention.
FIGs. 2B and 2C illustrate an example wherein 2Tx or 2
streams and 4Tx or 4 streams pilot REs are allocated when the
size of a basic unit has been extended to 4 subcarriers x 6
OFDM(A) symbols according to another embodiment of the
present invention.
FIG. 3A illustrates an example wherein 1Tx or 1 stream
pilots are allocated when each basic unit includes 4
subcarriers x 3 OFDM(A) symbols according to another
embodiment of the present invention.
FIGs. 3B and 3C illustrate an example wherein 2Tx or 2
streams and 4Tx or 4 streams pilots are allocated when the
size of a basic unit has been extended to 4 subcarriers x 6
OFDM(A) symbols according to another embodiment of the
present invention.
FIG. 4A illustrates an example wherein 1Tx or 1 stream
pilots are allocated when each basic unit includes 4
subcarriers x 3 OFDM(A) symbols according to another
embodiment of the present invention.
FIGs. 4B and 4C illustrate an example wherein 2Tx or 2
streams and 4Tx or 4 streams pilots are allocated when the
size of a basic unit has been extended to 4 subcarriers x 6
OFDM(A) symbols according to another embodiment of the
present invention.
FIGs. 5A-5C illustrate an example wherein 1Tx or 1
stream, 2Tx or 2 streams, and 4Tx or 4 streams pilots are
allocated when each basic unit includes 4 subcarriers x 6
OFDM(A) symbols according to another embodiment of the
present invention.
FIGs. 6A-6C illustrate an example wherein 1Tx or 1
stream, 2Tx or 2 streams, and 4Tx or 4 streams pilots are
allocated when each basic unit includes 4 subcarriers x 6
OFDM(A) symbols according to another embodiment of the
present invention.
FIGs. 7A-7C illustrate an example wherein 1Tx or 1
stream, 2Tx or 2 streams, and 4Tx or 4 streams pilots are
allocated when each basic unit includes 4 subcarriers x 6
OFDM(A) symbols according to another embodiment of the
present invention.
FIGs. 8A-8C illustrate an example wherein wherein 1Tx or
1 stream, 2Tx or 2 streams, and 4Tx or 4 streams pilots are
allocated when each basic unit includes 4 subcarriers x 6
OFDM(A) symbols according to another embodiment of the
present invention.
FIGs. 9A-9C illustrates an example wherein 1Tx or 1
stream, 2Tx or 2 streams, and 4Tx or 4 streams pilots are
allocated when each basic unit includes 4 subcarriers x 6
OFDM(A) symbols according to an embodiment of the present
invention.
FIGs. 10-13 illustrate an example wherein 1Tx or 1
stream pilots are allocated when each basic unit includes 4
subcarriers x 9 OFDM(A) symbols according to another
embodiment of the present invention,
FIGs. 14A-14C illustrates simulation results on channel
estimation in case of one stream transmission.
FIGs, 15A-15C illustrates simulation results on channel
estimation in case of two streams transmission.
FIG. 16 is a block diagram of a base station that can be
applied to an embodiment of the present invention.
FIG. 17 is a block diagram of a terminal that can be
applied to an embodiment of the present invention.
FIG. 18 illustrates a block diagram of a transmitter
that can be applied to an embodiment of the present invention.
FIG. 19 is a block diagram of a receiver that can be
applied to an embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Reference will now be made in detail to the preferred
embodiments of the present invention, examples of which are
illustrated in the accompanying drawings. Wherever possible,
the same reference numbers will be used throughout the
drawings to refer to the same or like parts.
The embodiments of the present invention provide a basic
unit and a pilot structure which can reduce pilot overhead in
uplink in an OFDM (A) system and can also guarantee high
performance of channel estimation. In the embodiments of the
present invention, pilot REs are allocated on the time axis
in each basic unit taking into consideration coherent time so
as to enable channel estimation that is robust to the low
speed and high speed cases in the time domain in the basic
unit. In addition, pilot REs are allocated on the frequency
axis in each basic unit taking into consideration coherent
bandwidth so as to achieve channel estimation that is robust
to various delay spread in the frequency domain. The
embodiments of the present invention also provide a basic
unit and a pilot structure which can improve channel
estimation performance using pilots of consecutive basic
units which are allocated in the time/frequency axis.
FIG. 2A illustrates an example wherein 1Tx or 1 stream
pilots are allocated when each basic unit includes 4
subcarriers x 3 OFDM(A) symbols according to an embodiment of
the present invention. In each 4x3 basic unit, two pilot REs
are arranged and pilot overhead is 16.57%. 4x3 basic units
can be consecutively allocated on the frequency axis or the
time axis.
If two pilot REs are used per 4x3 basic unit, it is
possible to reduce pilot overhead to half of that of the
conventional IEEE 802.16e uplink PUSC structure. In order to
guarantee robust channel estimation performance for both the
low speed user case and high speed user case, it is
preferable to arrange pilot REs in a 4x3 basic unit in a
distributed manner at both ends (i.e., the first and third
symbols) on the time axis in the 4x3 basic unit. In addition,
in order to guarantee robust channel estimation performance
taking into consideration frequency selectivity in channel
estimation on the frequency axis, it is preferable to
allocate pilot REs to both ends (i.e., the first and fourth
subcarriers) on the frequency axis in a 4x3 basic unit.
It can be seen from the left side of FIG. 2A that, in
each 4x3 basic unit, pilot REs are located at a subcarrier
index of "0" when s=0 and at a subcarrier index of "3" when
s=2. Here, the subcarrier index is an integer of no less
than 0, which increases from top to bottom and OFDM(A) symbol
index "s" is an integer of no less than 0, which increases
from left to right.
It can also be seen from the right side of FIG. 2A that,
in each 4x3 basic unit, pilot REs are located at a subcarrier
index of "3" when s=0 and at a subcarrier index of "0" when
s=2. The locations of the pilot REs can be cyclically
shifted along the time axis or the frequency axis. These
pilot patterns are summarized in the following tables.
[TABLE 1]
In Tables 1 and 2, "P" indicates the pilot RE, '-"
indicates the data RE, "s" indicates an OFDM (A) symbol index
in the basic unit, and "SC" indicates a subcarrier index in
the basic unit.
FIGs, 2B and 2C illustrate an example wherein 2Tx or 2
streams and 4Tx or 4 streams pilot REs are allocated when the
size of a basic unit has been extended to 4 subcarriers x 6
OFDM(A) symbols according to another embodiment of the
present invention. Pilot patterns of FIGs. 2B and 2C are
extended versions of the pilot pattern of FIG. 2A according
to multiple antennas.
As shown in FIG. 2B, in the 4x6 basic unit, two 2Tx or 2
streams pilot REs are arranged for each antenna port and
total pilot overhead is 16.57%, 4x6 basic units can be
consecutively allocated on the frequency axis or the time
axis. Pilot REs for the antenna port 0 are located at a
subcarrier index of "0" when s=0 and at a subcarrier index of
"3" when s=5. Pilot REs for the antenna port 1 are located
at a subcarrier index of '3" when s=2 and at a subcarrier
index of "0" when s=3. In another example, pilot REs for the
antenna port 0 are located at a subcarrier index of "3" when
s=0 and at a subcarrier index of "0" when s=5. Pilot REs for
the antenna port 1 are located at a subcarrier index of '"'0"
when s=2 and at a subcarrier index of "3" when s=3. The
antenna ports 0 and 1 may be switched with each other. That
is, the antenna ports 0 and 1 may be replaced with each other.
For example. Pilot REs for the antenna port 0 are located at
a subcarrier index of "3" when s=2 and at a subcarrier index
of "0" when s=3. And Pilot REs for the antenna port 1 are
located at a subcarrier index of '0" when s=0 and at a
subcarrier index of "3" when s=5.
The locations of the pilot REs can be cyclically shifted
along the time axis or the frequency axis. These pilot
patterns are summarized in the following tables.

In Tables 3 and 4, "P0" and "P1" indicate respective
pilot REs for the antenna ports 0 and 1, "-" indicates the
data RE, "s" indicates an OFDM (A) symbol index in the basic
unit, and "SC" indicates a subcarrier index in the basic unit.
As shown in FIG. 2C, in the 4x6 basic unit, two 4Tx or 4
streams pilot REs are arranged for each antenna port and
total pilot overhead is 33.34%. 4x6 basic units can be
consecutively allocated on the frequency axis or the time
axis. Pilot REs for the antenna port 0 are located at a
subcarrier index of "0" when s=0 and at a subcarrier index of
"3" when s=5. Pilot REs for the antenna port 1 are located
at a subcarrier index of "3" when s=2 and at a subcarrier
index of "0" when s=3. Pilot REs for the antenna port 2 are
located at a subcarrier index of "3" when s=0 and at a
subcarrier index of "0" when s=5. Pilot REs for the antenna
port 3 are located at a subcarrier index of "0" when s=2 and
at a subcarrier index of "3" when s=3. In another example,
pilot REs for the antenna port 0 are located at a subcarrier
index of "3" when s=0 and at a subcarrier index of "0" when
s=5. Pilot REs for the antenna port 1 are located at a
subcarrier index of '0" when s=2 and at a subcarrier index of
"3" when s=3. Pilot REs for the antenna port 2 are located
at a subcarrier index of "0" when s=0 and at a subcarrier
index of "S" when s=5. Pilot REs for the antenna port 3 are
located at a subcarrier index of "3" when s=2 and at a
subcarrier index of "0" when s=3. The antenna ports may be
switched with each other. The locations of the pilot REs can
be cyclically shifted along the time axis or the frequency
axis. These pilot patterns are summarized in the following
tables.

In Tables 5 and 6, "P0" to "P3" indicate respective
pilot REs for the antenna ports 0 to 3, "-" indicates the
data RE, "s" indicates an OFDM (A) symbol index in the basic
unit, and "SC" indicates a subcarrier index in the basic unit.
FIG. 3A illustrates an example wherein 1Tx or 1 stream
pilots are allocated when each basic unit includes 4
subcarriers x 3 OFDM(A) symbols according to another
embodiment of the present invention. In each 4x3 basic unit,
two pilots are arranged and pilot overhead is 15.67%. 4x3
basic units can be consecutively allocated on the frequency
axis or the time axis.
If two pilot REs are used per 4x3 basic unit, it is
possible to reduce pilot overhead to half of that of the
conventional IEEE 802.16e uplink PUSC structure. In addition,
in order to guarantee robust channel estimation performance
taking into consideration frequency selectivity in channel
estimation on the frequency axis, it is preferable to
allocate pilots to a 4x3 basic unit at both ends (i.e., the
first and fourth subcarriers) on the frequency axis in the
4x3 basic unit. It can be seen from FIG. 3A that, in each
4x3 basic unit, pilot REs are located at a subcarrier index
of "0" and at a subcarrier index of "3" when s=1. The
locations of the pilot REs can be cyclically shifted along
the time axis or the frequency axis. These pilot patterns
are summerized in the following table.

In Table 7, "P" indicates the pilot RE, "-" indicates
the data RE, "s" Indicates an OFDM (A) symbol index in the
basic unit, and 'SC" indicates a subcarrier index in the
basic unit.
FIGs. 3B and 3C illustrate an example wherein 2Tx or 2
streams and 4Tx or 4 streams pilots are allocated when the
size of a basic unit has been extended to 4 subcarriers x 6
OFDM(A) symbols according to another embodiment of the
present invention. Pilot patterns of FIGs. 3B and 3C are
extended versions of the pilot pattern of FIG. 3A according
to multiple antennas.
As shown in FIG. 3B, in the 4x6 basic unit, two 2Tx or 2
streams pilot REs are arranged for each antenna port and
total pilot overhead is 16.67%. 4x6 basic units can be
consecutively allocated on the frequency axis or the time
axis. Pilot REs for the antenna port 0 are located at a
subcarrier index of "0" when s=1 and at a subcarrier index of
"3" when s=4. Pilot REs for the antenna port 1 are located
at a subcarrier index of "3" when s=1 and at a subcarrier
index of "0" when s=4. The antenna ports may be switched
with each other. The locations of the pilot REs can be
cyclically shifted along the time axis or the frequency axis.
These pilot patterns are summarized in the following table.

In Table 8, "P0" and "P1" indicate respective pilot REs
for the antenna ports 0 and 1, "-" indicates the data RE, "s"
indicates an OFDM(A) symbol index in the basic unit, and "SC"
indicates a subcarrier index in the basic unit.
As shown in FIG. 3C, in the 4x6 basic unit, two 4Tx or 4
streams pilot REs are arranged for each antenna port and
total pilot overhead is 33.34%. 4x6 basic units can be
consecutively allocated on the frequency axis or the time
axis. Pilot REs for the antenna port 0 are located at a
subcarrier index of "0" when s=1 and at a subcarrier index of
"3" when s=4. Pilot REs for the antenna port 1 are located
at a subcarrier index of '3" when s=1 and at a subcarrier
index of "0" when s=4. Pilot REs for the antenna port 2 are
located at a subcarrier index of "1" when s=1 and at a
subcarrier index of "2" when s=4. Pilot REs for the antenna
port 3 are located at a subcarrier index of "2" when s=1 and
at a subcarrier index of "1" when s=4. The antenna ports may
be switched with each other. The locations of the pilot REs
can be cyclically shifted along the time axis or the
frequency axis. These pilot patterns are summarized in the
following table.

In Table 9, "P0" to 'P3" indicate respective pilot REs
for the antenna ports 0 to 3, "-" indicates the data RE, "s"
indicates an OFDM(A) symbol index in the basic unit, and "SC"
indicates a subcarrier index in the basic unit.
FIG. 4A illustrates an example wherein 1Tx or 1 stream
pilots are allocated when each basic unit includes 4
subcarriers x 3 OFDM(A) symbols according to another
embodiment of the present invention. In each 4x3 basic unit,
two pilots are arranged and pilot overhead is 16.67%. 4x3
basic units can be consecutively allocated on the frequency
axis or the time axis.
If two pilot REs are used per 4x3 basic unit, it is
possible to reduce pilot overhead to half of that of the
conventional IEEE 802.16e uplink PUSC structure. In order to
guarantee robust channel estimation performance for both the
low speed user case and high speed user case, it is
preferable to arrange pilots adjacent to each other on the
time axis in a 4x3 basic unit. In addition, in order to
guarantee robust channel estimation performance taking into
consideration frequency selectivity in channel estimation on
the frequency axis, it is preferable to allocate pilots to a
4x3 basic unit at both ends (i.e., the first and fourth
subcarriers) on the frequency axis in the 4x3 basic unit.
Pilot REs are located at a subcarrier index of "0" when s=1
and at a subcarrier index of "3" when s=2. In another
example, pilot REs are located at a subcarrier index of "0"
when s=0 and at a subcarrier index of "3" when s=1. The
locations of the pilot REs can be cyclically shifted along
the time axis or the frequency axis. These pilot patterns
are summarized in the following tables.


In Tables 10 and 11, "P" indicates the pilot RE, '-"
indicates the data RE, 's" indicates an OFDM (A) symbol index
in the basic unit, and 'SC" indicates a subcarrier index in
the basic unit.
FIGs. 4B and 4C illustrate an example wherein 2Tx or 2
streams and 4Tx or 4 streams pilots are allocated when the
size of a basic unit has been extended to 4 subcarriers x 6
OFDM(A) symbols according to another embodiment of the
present invention. Pilot patterns of FIGs. 4B and 4C are
extended versions of the pilot pattern of FIG. 4A according
to multiple antennas.
As shown in FIG. 4B, in the 4x6 basic unit, two 2Tx or 2
streams pilot REs are arranged for each antenna port and
total pilot overhead is 16.67%. 4x6 basic units can be
consecutively allocated on the frequency axis or the time
axis. Pilot REs for the antenna port 0 are located at a
subcarrier index of "0" when s=1 and at a subcarrier index of
"3" when s=5. Pilot REs for the antenna port 1 are located
at a subcarrier index of "3" when s=2 and at a subcarrier
index of "0" when s=4. In another example, pilot REs for the
antenna port 0 are located at a subcarrier index of "0" when
s=0 and at a subcarrier index of "3" when s=4. Pilot REs for
the antenna port 1 are located at a subcarrier index of "3"
when s=1 and at a subcarrier index of "0" when s=3. The
antenna ports may be switched with each other. The locations
of the pilot REs can be cyclically shifted along the time
axis or the frequency axis. These pilot patterns are
summarized in the following tables.

In Tables 12 and 13, "P0" and "P1" indicate respective
pilot REs for the antenna ports 0 and 1, "-" indicates the
data RE, "s" indicates an OFDM (A) symbol index in the basic
unit, and "SC" indicates a subcarrier index in the basic unit.
As shown in FIG. 4C, in the 4x6 basic unit, two 4Tx or 4
streams pilot REs are arranged for each antenna port and
total pilot overhead is 33.34%. 4x6 basic units can be
consecutively allocated on the frequency axis or the time
axis. Pilot REs for the antenna port 0 are located at a
subcarrier index of "0" when s=1 and at a subcarrier index of
"3" when s=5. Pilot REs for the antenna port 1 are located
at a subcarrier index of "3" when s=2 and at a subcarrier
index of "0" when s=4. Pilot REs for the antenna port 2 are
located at a subcarrier index of "0" when s=0 and at a
subcarrier index of "3" when s=4. Pilot REs for the antenna
port 3 are located at a subcarrier index of "3" when s=1 and
at a subcarrier index of "0" when s=3. In another example,
pilot REs for the antenna port 0 are located at a subcarrier
index of "0" when s=0 and at a subcarrier index of "3" when
s=4. Pilot REs for the antenna port 1 are located at a
subcarrier index of "3" when s=1 and at a subcarrier index of
'"0" when s=3. Pilot REs for the antenna port 2 are located
at a subcarrier index of "0" when s=1 and at a subcarrier
index of "3" when s=5. Pilot REs for the antenna port 3 are
located at a subcarrier index of "3" when s=2 and at a
subcarrier index of "0" when s=4. The antenna ports may be
switched with each other. The locations of the pilot REs can
be cyclically shifted along the time axis or the frequency
axis. These pilot patterns are summarized in the following
tables.

In Tables 14 and 15, "P0" to "P3" indicate respective
pilot REs for the antenna ports 0 to 3, "-" indicates the
data RE, "s" indicates an OFDM (A) symbol index in the basic
unit, and "SC" indicates a subcarrier index in the basic unit.
FIGs. 5A-5C illustrate an example wherein 1Tx or 1
stream, 2Tx or 2 streams, and 4Tx or 4 streams pilots are
allocated when each basic unit includes 4 subcarriers x 6
OFDM(A) symbols according to another embodiment of the
present invention. 4x6 basic units can be consecutively
allocated on the frequency axis or the time axis.
As shown in FIG. 5A, pilot REs are located at a
subcarrier index of "0" when s=0, at a subcarrier index of
"2" when s=1, at a subcarrier index of "1" when s=4, and at a
subcarrier index of "3" when s=5. In another example, pilot
REs are located at a subcarrier index of "3" when s=0, at a
subcarrier index of "1" when s=1, at a subcarrier index of
"2" when s=4, and at a subcarrier index of "0" when s=5. In
another example, pilot REs are located at a subcarrier index
of "1" when s=0, at a subcarrier index of "3" when s=2, at a
subcarrier index of "0" when s=3, and at a subcarrier index
of "2" when s=5. In another example, pilot REs are located
at a subcarrier index of "2" when s=0, at a subcarrier index
of "0" when s=2, at a subcarrier index of "3" when s=3, and
at a subcarrier index of "1" when s=5. The locations of the
pilot REs can be cyclically shifted along the time axis or
the frequency axis. These pilot patterns are summarized in
the following tables.

In Tables 16 to 19, "P" indicates the pilot RE, "-"
indicates the data RE, "s" indicates an OFDM (A) symbol index
in the basic unit, and "SC" indicates a subcarrier index in
the basic unit.
As shown in FIG. 5B, in the 4x6 basic unit, two 2Tx or 2
1 streams pilot REs are arranged for each antenna port and
total pilot overhead is 16.67%. Pilot REs for the antenna
port 0 are located at a subcarrier index of "0" when s=0 and
at a subcarrier index of "3" when s=5. Pilot REs for the
antenna port 1 are located at a subcarrier index of "2" when
s=1 and at a subcarrier index of "1" when s=4. In another
example, pilot REs for the antenna port 0 are located at a
subcarrier index of "3" when s=0 and at a subcarrier index of
"0" when s=5. Pilot REs for the antenna port 1 are located
at a subcarrier index of "1" when s=1 and at a subcarrier
index of "2" when s=4. In another example, pilot REs for the
antenna port 0 are located at a subcarrier index of "1" when
s=0 and at a subcarrier index of "2" when s=5. Pilot REs for
the antenna port 1 are located at a subcarrier index of "3"
when s=2 and at a subcarrier index of "0" when s=3. In
another example, pilot REs for the antenna port 0 are located
at a subcarrier index of "2" when s=0 and at a subcarrier
index of "1" when s=5. Pilot REs for the antenna port 1 are
located at a subcarrier index of "0" when s=2 and at a
subcarrier index of "3" when s=3. The antenna ports may be
switched with each other. The locations of the pilot REs can
be cyclically shifted along the time axis or the frequency
axis. These pilot patterns are summarized in the following
tables.


In Tables 20 to 23, "P0" and "P1" indicate respective
pilot REs for the antenna ports 0 and 1, "-" indicates the
data RE, "s" indicates an OFDM (A) symbol index in the basic
unit, and "SC" indicates a subcarrier index in the basic unit.
As shown in FIG. 5C, in the 4x6 basic unit, two 4Tx or 4
streams pilot REs are arranged for each antenna port and
total pilot overhead is 33.34%. Pilot REs for the antenna
port 0 are located at a subcarrier index of "0" when s=0 and
at a subcarrier index of "3" when s=5. Pilot REs for the
antenna port 1 are located at a subcarrier index of "2" when
s=1 and at a subcarrier index of "1" when s=4. Pilot REs for
the antenna port 2 are located at a subcarrier index of "3"
when s=0 and at a subcarrier index of "0" when s=5. Pilot
REs for the antenna port 3 are located at a subcarrier index
of "1" when s=1 and at a subcarrier index of "2" when s=4.
In another example, pilot REs for the antenna port 0 are
located at a subcarrier index of "3" when s=0 and at a
subcarrier index of "0" when s=5. Pilot REs for the antenna
port 1 are located at a subcarrier index of "1" when s=1 and
at a subcarrier index of "2" when s=4. Pilot REs for the
antenna port 2 are located at a subcarrier index of "0" when
s=0 and at a subcarrier index of "3" when s=5. Pilot REs for
the antenna port 3 are located at a subcarrier index of "2"
when s=1 and at a subcarrier index of "1" when s=4.
In another example, pilot REs for the antenna port 0 are
located at a subcarrier index of "1" when s=0 and at a
subcarrier index of "2" when s=5. Pilot REs for the antenna
port 1 are located at a subcarrier index of "3" when s=2 and
at a subcarrier index of "0" when s=3. Pilot REs for the
antenna port 2 are located at a subcarrier index of "2" when
s=0 and at a subcarrier index of "1" when s=5. Pilot REs for
the antenna port 3 are located at a subcarrier index of "0"
when s=2 and at a subcarrier index of "3" when s=3. In
another example, pilot REs for the antenna port 0 are located
at a subcarrier index of "2" when s=0 and at a subcarrier
index of "1" when s=5. Pilot REs for the antenna port 1 are
located at a subcarrier index of "0" when s=2 and at a
subcarrier index of "3" when s=3. Pilot REs for the antenna
port 2 are located at a subcarrier index of "1" when s=0 and
at a subcarrier index of "2" when s=5. Pilot REs for the
antenna port 3 are located at a subcarrier index of "3" when
s=2 and at a subcarrier index of "0" when s=3. The antenna
ports may be switched with each other. The locations of the
pilot REs can be cyclically shifted along the time axis or
the frequency axis. These pilot patterns are summarized in
the following tables.

In Tables 24 to 27, "P0" to "P3" indicate respective
pilot REs for the antenna ports 0 to 3, "-" indicates the
data RE, "s" indicates an OFDM (A) symbol index in the basic
unit, and "SC" indicates a subcarrier index in the basic unit.
FIGs. 6A-6C illustrate an example wherein 1Tx or 1
stream, 2Tx or 2 streams, and 4Tx or 4 streams pilots are
allocated when each basic' unit includes 4 subcarriers x 6
OFDM(A) symbols according to another embodiment of the
present invention. 4x6 basic units can be consecutively
allocated on the frequency axis or the time axis.
As shown in FIG. 6A, pilot REs are located at a
subcarrier index of "0" and at a subcarrier index of "2" when
s=1 and are located at a subcarrier index of "1" and at a
subcarrier index of "3" when s=4. In another example, pilot
REs are located at a subcarrier index of "1" and at a
subcarrier index of "3" when s=1 and are located at a
subcarrier index of "0" and at a subcarrier index of "2" when
5=4. The locations of the pilot REs can be cyclically
shifted along the time axis or the frequency axis. These
pilot patterns are summarized in the following tables.

In Tables 28 and 29, "P" indicates the pilot RE, "-"
indicates the data RE, "s" indicates an OFDM (A) symbol index
in the basic unit, and "SC" indicates a subcarrier index in
the basic unit.
As shown in FIG. 6B, in the 4x6 basic unit, two 2Tx or 2
streams pilot REs are arranged for each antenna port and
total pilot overhead is 16.67%. Pilot REs for the antenna
port 0 are located at a subcarrier index of "0" when s=1 and
at a subcarrier index of "3" when s=4. Pilot REs for the
antenna port 1 are located at a subcarrier index of "2" when
s=1 and at a subcarrier index of "1" when s=4. In another
example, pilot REs for the antenna port 0 are located at a
subcarrier index of "3" when s=1 and at a subcarrier index of
"0" when s=4. Pilot REs for the antenna port 1 are located
at a subcarrier index of "1" when s=1 and at a subcarrier
index of "2" when s=4. The antenna ports may be switched
with each other. The locations of the pilot RSs can be
cyclically shifted along the time axis or the frequency axis.
These pilot patterns are summarized in the following tables.

In Tables 30 and 31, "P0" and "P1" indicate respective
pilot REs for the antenna ports 0 and 1, "-" indicates the
data RE, "s" indicates an OFDM (A) symbol index in the basic
unit, and "SC" indicates a subcarrier index in the basic unit.
As shown in FIG. 6C, in the 4x6 basic unit, two 4Tx or 4
streams pilot REs are arranged for each antenna port and
total pilot overhead is 33.34%. Pilot REs for the antenna
port 0 are located at a subcarrier index of "0" when 3=1 and
at a subcarrier index of "3" when s=4. Pilot REs for the
antenna port 1 are located at a subcarrier index of "2" when
3=1 and at a subcarrier index of "1" when s=4. Pilot REs for
the antenna port 2 are located at a subcarrier index of "1"
when s=1 and at a subcarrier index of "2" when s=4. Pilot
REs for the antenna port 3 are located at a subcarrier index
of "3" when s=1 and at a subcarrier index of "0" when s=4.
In another example, pilot REs for the antenna port 0 are
located at a subcarrier index of "3" when s=1 and at a
subcarrier index of "0" when s=4. Pilot REs for the antenna
port 1 are located at a subcarrier index of "1" when s=1 and
at a subcarrier index of "2" when s=4. Pilot REs for the
antenna port 2 are located at a subcarrier index of "2" when
s=1 and at a subcarrier index of "1" when s=4. Pilot REs for
the antenna port 3 are located at a subcarrier index of "0"
when s=1 and at a subcarrier index of "3" when s=4. The
antenna ports may be switched with each other. The locations
of the pilot REs can be cyclically shifted along the time
axis or the frequency axis. These pilot patterns are
summarized in the following tables.


In Tables 32 and 33, "P0" to "P3" indicate respective
pilot REs for the antenna ports 0 to 3, "-" indicates the
data RE, "s" indicates an OFDM (A) symbol index in the basic
unit, and "SC" indicates a subcarrier index in the basic unit.
FIGs. 7A-7C illustrate an example wherein 1Tx or 1
stream, 2Tx or 2 streams, and 4Tx or 4 streams pilots are
allocated when each basic unit includes 4 subcarriers x 6
OFDM(A) symbols according to another embodiment of the
present invention. 4x6 basic units can be consecutively
allocated on the frequency axis or the time axis.
As shown in FIG. 7A, pilot REs are located at a
subcarrier index of "1" when s=1, at a subcarrier index of
"3" when s=2, at a subcarrier index of "0" when s=3, and at a
subcarrier index of "2" when s=4. In another example, pilot
REs are located at a subcarrier index of "2" when s=1, at a
subcarrier index of "0" when s=2, at a subcarrier index of
"3" when s=3, and at a subcarrier index of "1" when s=4. The
locations of the pilot REs can be cyclically shifted along
the time axis or the frequency axis. These pilot patterns
are summarized in the following tables.


In Tables 34 and 35, "P" indicates the pilot RE, '-"
indicates the data RE, "s" indicates an OFDM (A) symbol index
in the basic unit, and "SC" indicates a subcarrier index in
the basic unit.
As shown in FIG. 7B, in the 4x6 basic unit, two 2Tx or 2
streams pilot REs are arranged for each antenna port and
total pilot overhead is 16.67%. Pilot REs for the antenna
port 0 are located at a subcarrier index of "1" when s=1 and
at a subcarrier index of "2" when s=4. Pilot REs for the
antenna port 1 are located at a subcarrier index of "3" when
s=2 and at a subcarrier index of "0" when s=3. In another
example, pilot REs for the antenna port 0 are located at a
subcarrier index of "2" when s=1 and at a subcarrier index of
"1" when s=4. Pilot REs for the antenna port 1 are located
at a subcarrier index of "0" when s=2 and at a subcarrier
index of "3" when s=3. The antenna ports may be switched
with each other. The locations of the pilot REs can be
cyclically shifted along the time axis or the frequency axis.
These pilot patterns are summarized in the following tables.


In Tables 36 to 37, "P0" and 'P1" indicate respective
pilot REs for the antenna ports 0 and 1, '-" indicates the
data RE, 's" indicates an OFDM (A) symbol index in the basic
unit, and 'SC" indicates a subcarrier index in the basic unit.
As shown in FIG. 7C, in the 4x6 basic unit, two 4Tx or 4
streams pilot REs are arranged for each antenna port and
total pilot overhead is 33.34%. Pilot REs for the antenna
port 0 are located at a subcarrier index of "1" when 3=1 and
at a subcarrier index of "2" when s=4. Pilot REs for the
antenna port 1 are located at a subcarrier index of "3" when
s=2 and at a subcarrier index of "0" when s=3. Pilot REs for
the antenna port 2 are located at a subcarrier index of "2"
when s=1 and at a subcarrier index of "1" when s=4. Pilot
REs for the antenna port 3 are located at a subcarrier index
of "0" when s=2 and at a subcarrier index of "3" when s=3.
In another example, pilot REs for the antenna port 0 are
located at a subcarrier index of "2" when s=1 and at a
subcarrier index of "1" when s=4, Pilot REs for the antenna
port 1 are located at a subcarrier index of "0" when s=2 and
at a subcarrier index of "3" when s=3. Pilot REs for the
antenna port 2 are located at a subcarrier index of "1" when
s=1 and at a subcarrier index of "2" when s=4, Pilot REs for
the antenna port 3 are located at a subcarrier index of "3"
when s=2 and at a subcarrier index of "0" when s=3. The
antenna ports may be switched with each other. The locations
of the pilot REs can be cyclically shifted along the time
axis or the frequency axis. These pilot patterns are
summarized in the following tables.

In Tables 38 and 39, "P0" to "P3" indicate respective
pilot REs for the antenna ports 0 to 3, "-" indicates the
data RE, "s" indicates an OFDM (A) symbol index in the basic
unit, and "SC" indicates a subcarrier index in the basic unit.
FIGs. 8A-8C illustrate an example wherein 1Tx or 1
stream, 2Tx or 2 streams, and 4Tx or 4 streams pilots are
allocated when each basic unit includes 4 subcarriers x 6
OFDM(A) symbols according to another embodiment of the
present invention. 4x5 basic units can be consecutively
allocated on the frequency axis or the time axis.
As shown in FIG. 8A, if two pilot REs are used per 4x6
basic unit, it is possible to reduce pilot overhead to half
of that of the conventional IEEE 802.16e uplink PUSC
structure. In order to guarantee robust channel estimation
performance for the low speed user case, it is preferable to
arrange pilots in a 4x6 basic unit in a distributed manner at
both ends on the time axis in the 4x6 basic unit. In
addition, in order to guarantee robust channel estimation
performance taking into consideration frequency selectivity
in channel estimation on the frequency axis, it is preferable
to allocate pilots to a 4x5 basic unit at both ends (i.e.,
the first and fourth subcarriers) on the frequency axis in
the 4x6 basic unit. In each 4x6 basic unit, pilot REs are
located at a subcarrier index of "0" and at a subcarrier
index of "3" when s=0 and are located at a subcarrier index
of "0" and at a subcarrier index of "3" when s=5. The
locations of the pilot REs can be cyclically shifted along
the time axis or the frequency axis. These pilot patterns
are summarized in the following table.

In Table 40, "P" indicates the pilot RE, '-" indicates
the data RE, "s" indicates an OFDM(A) symbol index in the
basic unit, and "SC" indicates a subcarrier index in the
basic unit.
As shown in FIG. 8B, in the 4x6 basic unit, two 2Tx or 2
streams pilot REs are arranged for each antenna port and
total pilot overhead is 16.67%. Pilot REs for the antenna
port 0 are located at a subcarrier index of "0" when s=0 and
at a subcarrier index of "3" when s=5. Pilot REs for the
antenna port 1 are located at a subcarrier index of "3" when
s=0 and at a subcarrier index of "0" when s=5. The antenna
ports may be switched with each other. The locations of the
pilot REs can be cyclically shifted along the time axis or
the frequency axis. These pilot patterns are summarized in
the following table.

In Table 41, "P0" and "P1" indicate respective pilot REs
for the antenna ports 0 and 1, "-" indicates the data RE, "s"
indicates an OFDM(A) symbol index in the basic unit, and "SC"
indicates a subcarrier index in the basic unit.
These pilot patterns are especially preferable for
uplink transmission with 2Tx antennas or 2 streams for the
following reasons.
First, in the case of a wireless communication system
which supports Multi-Input Multi-Output (MIMO) technologies,
the pilot patterns of FIG. 8B can efficiently support Space
Time Block Code (STBC) and Space Frequency Block Code (STBC).
To support STBC, subcarriers for transmission of control
information and data, excluding pilots, should constitute an
even number of OFDM(A) symbols on the time axis. Especially,
consecutively allocating paired OFDM(A) symbols in each
subcarrier unit can achieve a further improvement in STBC
performance. This is because that, in STBC, a high gain can
be achieved if channels that paired OFDM(A) symbols in each
subcarrier unit experience are identical or similar.
Referring to FIG. 8B, OFDM(A) symbols in each subcarrier unit,
excluding pilots, are consecutive on the time axis and are
also even in number. To support SFBC, the number of
subcarriers for transmission of control information and data,
excluding pilots, should be even on the frequency axis.
Especially, consecutively allocating paired subcarriers in
each OFDM(A) symbol can achieve a further improvement in SFBC
performance. This is because that, in SFBC, a high gain can
be achieved if channels that paired subcarriers experience
are identical or similar. Referring to FIG. 8B, subcarriers
excluding pilots in each OFDM(A) symbol are consecutive and
are also even in number. The pilot patterns of FIG. 8B can
effectively support the MIMO system.
Second, since pilots for the antenna ports 0 and 1 are
allocated to the same OFDM (A) symbol, it is possible to
improve performance of channel estimation through pilot
boosting. For example, when data and pilots for the antenna
port 0 are transmitted, no pilot REs for the antenna port 1
are transmitted. In this case, power for allocation to the
pilots for the antenna port 1 can be additionally allocated
to the pilots for the antenna port 0. This can improve
performance of channel estimation through pilot boosting.
This also helps in solving the power balancing problem in
uplink transmission with limited available power.
Third, it is possible to perform efficient channel
estimation using as much coherent time and coherent bandwidth
as possible. Specifically, even in an environment in which
channel delay spread is significant, channels almost never
change or only slightly change in 4 consecutive subcarrier
units. Unless the terminal is in motion at high speed,
channel change is not great in 6 or less consecutive OFDM (A)
symbols. In addition, even when the speed of the terminal is
increased such that it experiences a high-speed channel, the
channel linearly changes in 6 or less consecutive OFDM(A)
symbols. Referring to FIG. 8B, 2 pilots for each of the
antenna ports 0 and 1 are located at both diagonal ends of a
4x6 basic unit. This utilizes as much coherent time and
coherent bandwidth as possible, thereby achieving efficient
channel estimation.
Fourth, since pilots are allocated to each 4x6 basic
unit at edges thereof, it is possible to prevent degradation
of channel estimation performance due to extrapolation during
channel estimation.
As shown in FIG. 8C, in the 4x6 basic unit, two 4Tx or 4
streams pilot REs are arranged for each antenna port and
total pilot overhead is 33.34%. Pilot REs for the antenna
port 0 are located at a subcarrier index of "0" when s=0 and
at a subcarrier index of "3" when s=5. Pilot REs for the
antenna port 1 are located at a subcarrier index of "3" when
s=0 and at a subcarrier index of "0" when s=5. Pilot REs for
the antenna port 2 are located at a subcarrier index of "1"
when s=0 and at a subcarrier index of "2" when s=5. Pilot
REs for the antenna port 3 are located at a subcarrier index
of "2" when s=0 and at a subcarrier index of "1" when s=5.
The antenna ports may be switched with each other. The
locations of the pilot REs can be cyclically shifted along
the time axis or the frequency axis. These pilot patterns
are summarized in the following table.

In Table 42, "P0" to "P3" indicate respective pilot REs
for the antenna ports 0 to 3, "-" indicates the data RE, "s"
indicates an OFDM(A) symbol index in the basic unit, and "SC"
indicates a subcarrier index in the basic unit.
FIGs. 9A-9C illustrates an example wherein 1Tx or 1
stream, 2Tx or 2 streams, and 4Tx or 4 streams pilots are
allocated when each basic unit includes 4 subcarriers x 6
OFDM(A) symbols according to an embodiment of the present
invention. 4x6 basic units can be consecutively allocated on
the frequency axis or the time axis.
As shown in FIG. 9A, pilot REs are located at a
subcarrier index of "0" when s=0, at a subcarrier index of
"3" when s=1, at a subcarrier index of "0" when s=4, and at a
subcarrier index of "3" when s=5. In another example, pilot
REs are located at a subcarrier index of "3" when s=0, at a
subcarrier index of "0" when s=1, at a subcarrier index of
"3" when s=4, and at a subcarrier index of "0" when s=5. The
locations of the pilot REs can be cyclically shifted along
the time axis or the frequency axis. These pilot patterns
are summarized in the following tables.

In Tables 43 and 44, "P" indicates the pilot RE, "-"
indicates the data RE, "s" indicates an OFDM(A) symbol index
in the basic unit, and "SC" indicates a subcarrier index in
the basic unit.
These pilot patterns are especially preferable for
uplink transmission with a 1Tx antenna or 1 stream for the
following reasons.
First, the pilot patterns have a structure suitable for
achieving a channel estimation gain through pilot boosting.
In the case of the pilot patterns of FIG. 9A, pilot REs are
located at different OFDM(A) symbols on the time axis.
Accordingly, when pilot REs and data REs are simultaneously
transmitted or pilot REs alone are transmitted, it is
possible to improve channel estimation performance through
pilot boosting effects. That is, a portion of power for
allocation to data REs can be allocated to pilot REs, thereby
achieving a performance gain through pilot boosting. However,
in the case where a number of pilots for a single antenna are
allocated to the same OFDM(A) symbol, the performance
improvement is not great since limited power of data REs is
distributed over a number of pilots. Specifically, in the
case of the pilot patterns of FIG. 9A, a portion of power for
allocation to 3 data REs in one OFDM (A) symbol is allocated
to pilot REs, thereby achieving a performance gain through
pilot boosting. However, in the case where 2 pilot REs are
included in one OFDM (A) symbol, power for use in 2 data REs
is allocated to 2 pilot REs and therefore the improvement of
performance through pilot boosting is small, compared to when
one pilot RE is included in one OFDM(A) symbol. Especially,
taking into consideration the fact that uplink power is
limited, the use of one pilot RE in one OFDM (A) symbol helps
in solving the power balancing problem.
Second, it is possible to perform efficient channel
estimation using as much coherent time and coherent bandwidth
as possible. Specifically, even when channel delay spread is
significant, the coherent bandwidth is 4 or more subcarriers
and thus the channel almost never changes or only slightly
changes in 4 consecutive subcarriers. In addition, even when
the speed of the terminal is increased such that it
experiences a high-speed channel, the coherent time is 3 or
more OFDM(A) symbols and thus the channel changes in units of
3 or more OFDM(A) symbols (i.e., the channel almost never
changes in 3 consecutive OFDM(A) symbols). In the pilot
patterns of FIG. 9A, pilots are arranged such that the pilot
spacing is maximized on the frequency axis and the time axis.
Specifically, the pilot spacing is 3 subcarriers on the
frequency axis and is 1 and 3 OFDM (A) symbols on the time
axis. Accordingly, as much coherent time and coherent
bandwidth can be utilized as possible, thereby improving
channel estimation performance.
As shown in FIG. 9B, in the 4x6 basic unit, two 2Tx or 2
streams pilot REs are arranged for each antenna port and
total pilot overhead is 15.67%. Pilot REs for the antenna
port 0 are located at a subcarrier index of "0" when s=0 and
at a subcarrier index of '3" when s=5. Pilot REs for the
antenna port 1 are located at a subcarrier index of "3" when
s=1 and at a subcarrier index of "0" when s=4. In another
example, pilot REs for the antenna port 0 are located at a
subcarrier index of "3" when s=0 and at a subcarrier index of
"0" when s=5. Pilot REs for the antenna port 1 are located
at a subcarrier index of "0" when s=1 and at a subcarrier
index of "3" when s=4. The antenna ports may be switched
with each other. The locations of the pilot RBs can be
cyclically shifted along the time axis or the frequency axis.
These pilot patterns are summarized in the following tables.

In Tables 45 and 46, "P0" and "P1" indicate respective
pilot REs for the antenna ports 0 and 1, "-" indicates the
data RE, "s" indicates an OFDM (A) symbol index in the basic
unit, and "SC" indicates a subcarrier index in the basic unit.
As shown in FIG. 9C, in the 4x6 basic unit, two 4Tx or 4
streams pilot REs are arranged for each antenna port and
total pilot overhead is 33.34%. Pilot REs for the antenna
port 0 are located at a subcarrier index of "0" when s=0 and
at a subcarrier index of "3" when s=5. Pilot REs for the
antenna port 1 are located at a subcarrier index of "3" when
s=1 and at a subcarrier index of "0" when s=4. Pilot REs for
the antenna port 2 are located at a subcarrier index of "3"
when s=0 and at a subcarrier index of "0" when s=5. Pilot
REs for the antenna port 3 are. located at a subcarrier index
of "0" when s=1 and at a subcarrier index of "3" when s=4.
In another example, pilot REs for the antenna port 0 are
located at a subcarrier index of '"3" when s=0 and at a
subcarrier index of "0" when s=5. Pilot REs for the antenna
port 1 are located at a subcarrier index of "0" when s=1 and
at a subcarrier index of "3" when s=4. Pilot REs for the
antenna port 2 are located at a subcarrier index of "0" when
s=0 and at a subcarrier index of "3" when s=5. Pilot REs for
the antenna port 3 are located at a subcarrier index of "3"
when s=1 and at a subcarrier index of "0" when s=4. The
antenna ports may be switched with each other. The locations
of the pilot REs can be cyclically shifted along the time
axis or the frequency axis. These pilot patterns are
summarized in the following tables.

In Tables 47 and 48, "P0" to "P3" indicate respective
pilot REs for the antenna ports 0 to 3, "-" indicates the
data RE, "s" indicates an OFDM (A) symbol index in the basic
unit, and "SC" indicates a subcarrier index in the basic unit.
FIG. 10 illustrates an example wherein 1Tx or 1 stream
pilots are allocated when each basic unit includes 4
subcarriers x 9 OFDM(A) symbols according to another
embodiment of the present invention. Pilots are located at
both ends of each 4x9 basic unit on the frequency axis and
are arranged at the same time intervals. Here, pilot
overhead is 16.67%. 4x9 basic units can be consecutively
allocated on the frequency axis or the time axis. Although
FIG. 10 is illustrated for pilots for a single antenna, the
pilot pattern of FIG. 10 can also be applied to multiple
antennas in a manner similar to that illustrated in FIGs. 2
to 9.
Specifically, pilot REs are located at a subcarrier
index of "0" and at a subcarrier index of "3" when s=0, at a
subcarrier index of "0" and at a subcarrier index of "3" when
s=4, and at a subcarrier index of "0" and at a subcarrier
index of "3" when s=8. The locations of the pilot REs can be
cyclically shifted along the time axis or the frequency axis.
These pilot patterns are summarized in the following table.

In Table 49, "P" indicates the pilot RE, "-" indicates
the data RE, "s" indicates an OFDM (A) symbol index in the
basic unit, and "SC" indicates a subcarrier index in the
basic unit.
FIG. 11 illustrates an example wherein 1Tx or 1 stream
pilots are allocated when each basic unit includes 4
subcarriers x 9 OFDM(A) symbols according to another
embodiment of the present invention. Pilot REs are designed
such that they are arranged at intervals of 2 OFDM(A) symbols
on the time axis so as to achieve greater robustness in the
high speed case than in the low speed case. Here, pilot
overhead is 11.11%. 4x9 basic units can be consecutively
allocated on the frequency axis or the time axis. Although
FIG. 11 is illustrated for pilots for a single antenna, the
pilot pattern of FIG. 11 can also be applied to multiple
antennas in a manner similar to that illustrated in FIGs. 2
to 9.
Specifically, pilot REs are located at a subcarrier
index of "0" when s=1, at a subcarrier index of "3" when s=3,
at a subcarrier index of "0" when s=5, and at a subcarrier
index of "3" when s=7. In another example, pilot REs are
located at a subcarrier index of "3" when s=1, at a
subcarrier index of "0" when s=3, at a subcarrier index of
"3" when s=5, and at a subcarrier index of "0" when s=7. The
locations of the pilot REs can be cyclically shifted along
the time axis or the frequency axis. These pilot patterns
are summarized in the following table.

In Tables 50 and 51, "P" indicates the pilot RE, "-"
indicates the data RE, 's" indicates an OFDM (A) symbol index
in the basic unit, and "SC" indicates a subcarrier index in
the basic unit.
FIG. 12 illustrates an example wherein 1Tx or 1 stream
pilots are allocated when each basic unit includes 4
subcarriers x 9 OFDM(A) symbols according to another
embodiment of the present invention. Pilot REs are designed
such that they are arranged at intervals of 2 OFDM(A) symbols
on the time axis so as to achieve greater robustness in the
high speed case than in the low speed case. In addition,
pilots are designed such that they are arranged at all
positions on the frequency axis, thereby achieving greater
robustness to channel delay spread. Here, pilot overhead is
11,11%. 4x9 basic units can be consecutively allocated on
the frequency axis or the time axis. Although FIG, 12 is
illustrated for pilots for a single antenna, the pilot
pattern of FIG. 12 can also be applied to multiple antennas
in a manner similar to that illustrated in FIGs. 2 to 9.
Specifically, pilot REs are located at a subcarrier
index of "1" when s=1, at a subcarrier index of "3" when s=3,
at a subcarrier index of "0" when s=5, and at a subcarrier
index of "2" when s=7. In another example, pilot REs are
located at a subcarrier index of "2" when s=1, at a
subcarrier index of "0" when s=3, at a subcarrier index of
"3" when s=5, and at a subcarrier index of "1" when s=7. The
locations of the pilot REs can be cyclically shifted along
the time axis or the frequency axis. These pilot patterns
are summarized in the following table.


In Tables 52 and 53, "P" indicates the pilot RE, "-"
indicates the data RE, "s" indicates an OFDM (A) symbol index
in the basic unit, and "SC" indicates a subcarrier index in
the basic unit.
FIG. 13 illustrates an example wherein 1Tx or 1 stream
pilots are allocated when each basic unit includes 4
subcarriers x 9 OFDM(A) symbols according to another
embodiment of the present invention. Pilot REs are designed
such that they are arranged at intervals of 2 OFDM(A) symbols
on the time axis so as to achieve greater robustness in the
high speed case than in the low speed case. In addition,
pilots are designed such that they are arranged at all
positions on the frequency axis, thereby achieving greater
robustness to channel delay spread. Here, pilot overhead is
11.11%. 4x9 basic units can be consecutively allocated on
the frequency axis or the time axis. Although FIG. 13 is
illustrated for pilots for a single antenna, the pilot
pattern of FIG. 13 can also be applied to multiple antennas
in a manner similar to that illustrated in FIGs. 2 to 9.
Specifically, pilot REs are located at a subcarrier
index of "0" when s=0, at a subcarrier index of "3" when s=3,
at a subcarrier index of "0" when s=5, and at a subcarrier
index of "3" when s=8. In another example, pilot REs are
located at a subcarrier index of "3" when s=0, at a
subcarrier index of "0" when s=3, at a subcarrier index of
"3" when s=5, and at a subcarrier index of "0" when s=8. The
locations of the pilot REs can be cyclically shifted along
the time axis or the frequency axis. These pilot patterns
are summarized in the following table.

In Tables 54 and 55, "P" indicates the pilot RE, "-"
indicates the data RE, "s" indicates an OFDM(A) symbol index
in the basic unit, and "SC" indicates a subcarrier index in
the basic unit.
In order to measure the channel estimation ability of
the above pilot patterns xemplified by the present invention,
comparative simulations were carried out in case of one
stream and two streams transmissions.
The pilot pilot pattern used in the comparative
simulation are shown in the following table:
[TABLE 56]

In Table 56, the numbers "1" and "2" in the pilot
patterns indicate pilot REs for a first stream and a second
stream, which correspond to the "P0" and "P1" respectively.
The pilot patterns 1-1 and 1-2 correspond to the pilot
patterns of Fig. 8A (Table 40) and Fig. 9A (Table 43)
respectively. The pilot pattern 1-3 corresponds to two
consecutively arranged pilot pattern of Fig. 3A (Table 7) in
time domain. The pilot pattern 2-1 corresponds to the pilot
patterns of Fig. 8B (Table 41). The pilot patterns 2-2 and
2-3 are pilot patterns specified for comparative purpose.
The simulation parameters are as follows:
- Channel estimation: Two-dimensional Minimum Mean
Square Error (2D MMSE) Channel Estimation
- Receiver: 2 Rx MMSE receiver
- Channel Model: eITU PedB3km/h, VehA120km/h,
VehA350km/h Channel
- Tx antenna spacing; 4 lambda
- Rx antenna spacing; 0.5 lambda
- Pilot boosting: 3dB
- Noise-limited
FIGs. 14A-14C illustrates simulation results on channel
estimation in case of one stream transmission.
In, PedB (Pedestrian B) 3km/h, the three pilot patterns
1-1, 1-2 and 1-3 show similar link throughput performance.
The pilot pattern 1-2 shows the least degradataion in
relative throughput loss performance (Fig. 14A).
In VehA (Vehicular A) 120km/h, the three pilot patterns
1-1, 1-2 and 1-3 show similar link throughput performance.
The pilot pattern 1-2 clearly outperforms the others in
relative throughput loss performance (Fig. 148).
In VehA 350km/h, the pilot pattern 1-2 clearly
outperforms the others in both link throughput performance
and relative throughput loss performance (Fig. 14C).
FIGs. 15A-15C illustrates simulation results on channel
estimation in case of two streams transmission.
In all the conditions PedB 3km/h, VehA 120km/h and VehA
350km/h, the pilot pattern 2-1 clearly outperforms the others
in both link throughput performance and relative throughput
loss performance (Figs. 15A-15C).
FIG. 16 is a block diagram of a base station that can be
applied to an embodiment of the present invention.
As shown in FIG. 16, the base station generally includes
a control system 1602, a baseband processor 1604, transmit
circuitry 1606, receive circuitry 1608, multiple antennas
1510, and a network interface 1612. The receive circuitry
1508 receives a radio signal transmitted from a terminal
through the multiple antennas 1610. Preferably, a low-noise
amplifier and a filter (not shown) amplify the received
signal and remove broadband interference from the signal.
Downconversion and digitization circuitry (not shown)
downconverts the filtered signal to an intermediate or
baseband frequency signal and then digitizes the
downconverted signal into one or more digital streams.
The baseband processor 1504 processes the digital
received signal to extract information or data bits from the
received signal. This processing includes demodulation,
decoding, error correction, or the like. The baseband
processor 1604 generally includes one or more Digital Signal
Processors (DSPs). Thereafter, the received information is
transmitted through a wireless network via a network
interface or is transmitted to another terminal served by the
base station. The network interface 1612 interacts with a
circuit switched network that forms a part of a wireless
network that can be connected to a Public Switched Telephone
Network (PSTN) and a central network controller.
On the transmitting side, the baseband processor 1604
receives digital data, which can represent voice, data, or
control information, from the network interface 1612, and
encodes the data for transmission under control of the
control system 1602. The encoded data is input to the
transmit circuitry 1606. The transmit circuitry 1606
modulates the encoded data using a carrier having a desired
transmission frequency(s) . The amplifier (not shown)
amplifies the modulated carrier signal to a level suitable
for transmission. The amplified signal is transmitted to the
multiple antennas 1610.
FIG. 17 is a block diagram of a terminal that can be
applied to an embodiment of the present invention.
As shown in FIG. 17, the terminal may include a control
system 1702, a baseband processor 1704, transmit circuitry
1706, receive circuitry 1708, multiple antennas 1710, and
user interface circuitry 1712. The receive circuitry 1708
receives a radio signal including information from one or
more base stations through the multiple antennas 1710.
Preferably, a low-noise amplifier and a filter (not shown)
amplify the received signal and remove broadband interference
from the signal. Thereafter, downconversion and digitization
circuitry (not shown) downconverts the filtered signal to an
intermediate or baseband frequency signal and then digitizes
the downconverted signal into one or more digital streams.
The baseband processor 1704 processes the digital received
signal to extract information or data bits from the received
signal. This processing includes operations such as
demodulation, decoding, and error correction. The baseband
processor 1704 generally includes one or more Digital Signal
Processors (DSPs) and Application Specific Integrated
Circuits (ASICs).
On the transmitting side, the baseband processor 1704
receives digital data, which can represent voice, data, or
control information, from the user interface circuitry 1712,
and encodes the data for transmission under control of the
control system 1702. The encoded data is input to the
transmit circuitry 1706. The transmit circuitry 1706
modulates the encoded data using a carrier having a desired
transmission frequency(s). The amplifier (not shown)
amplifies the modulated carrier signal to a level suitable
for transmission. The amplified signal is transmitted to the
multiple antennas 1710.
FIG. 18 illustrates a block diagram of a transmitter
that can be applied to an embodiment of the present invention.
Although the structure of the transmitter of FIG, 18
will be described with reference to a base station, it will
be appreciated by those skilled in the art that the
illustrated structure can be used for both uplink and
downlink transmission. The illustrated transmission
structure is intended to represent, without being limited to,
a variety of multiple access structures including Code
Division Multiple Access (CDMA), Frequency Division Multiple
Access (FDMA), and Orthogonal Frequency Division Multiplexing
(OFDM).
Initially, the network transmits data for transmission
to a terminal to the base station. In the base station, a
data scrambling module 1804 scrambles scheduled data, which
is a bitstream, in a manner reducing a peak to average power
ratio associated with data. A CRC adding module 1806 then
determines and adds a Cyclic Redundancy Check (CRC) checksum
for the scrambled data to the scrambled data. Then, a
channel encoder module 1808 performs channel coding on the
data to allow the terminal to perform recovery and error
correction of the data. The channel coding enables efficient
addition of redundancy to the data. The channel encoder
module 1808 can use turbo encoding technologies.
Then, a mapping module 1814 systematically maps the
processed data bits to a corresponding symbol based on a
selected baseband modulation mode. Here, a Quadrature
Amplitude Modulation (QAM) or Quadrature Phase-Shift Keying
(QPSK) modulation mode can be used. A bit group is mapped to
a symbol representing a position in the amplitude-phase
constellation. Then, a Space-Time Code (STC) encoder module
1818 processes the symbol block. Specifically, the STC
. encoder module 1818 processes the symbol according to a
selected STC encoding mode and provides the same number of N
outputs as the number of the multiple antennas 1610 of the
base station. Each of a plurality of IFFT processing modules
1820 inverse Fourier-transforms a symbol stream output from
the STC encoder module 1818. Then, each of a plurality of
prefix and RS insertion modules 1822 inserts a Cyclic Prefix
(CP) and an RS to the inverse Fourier-transformed signal.
Although RS is exemplified to be inserted after IFFT has been
carried out, RS may be also inserted before IFFT. In this
case, separate RS insertion module may be added before IFFT
processing modules 1820. Then, each, of a plurality of
digital upconversion (DUC) and digital to analog (D/A)
conversion modules 1824 upconverts the processed signal from
the prefix and RS insertion module 1822 to an intermediate
frequency in the digital domain and then converts the
upconverted signal into an analog signal. Then, analog
signals created in this manner are simultaneously modulated,
amplified, and transmitted through a plurality of RP modules
1826 and the multiple antennas 1610.
FIG. 19 is a block diagram of a receiver that can be
applied to an embodiment of the present invention.
Although the structure of the receiver of FIG. 19 will
be described with reference to a terminal, it will be
appreciated by those skilled in the art that the illustrated
structure can be used for both uplink and downlink
transmission. When a transmission signal is received by
multiple antennas 1710, each signal is demodulated and
amplified through a corresponding RF module 1902. For the
sake of convenience, only one of multiple reception paths is
illustrated in FIG. 19. An analog to digital (A/D)
conversion and digital downconversion module (DCC) 1904 then
converts the analog signal into a digital signal for digital
processing and donwnconverts the digital signal. The digital
signal can be provided to and used in an Automatic Gain
Control (AGO module 1906 in order to control amplifier gain
of the RF module 1902 based on the received signal level.
The digital signal is also provided to a synchronization
module 1908. The synchronization module 1908 may include a
coarse sync module 1910 that performs coarse synchronization,
a fine sync module 1912 that performs fine synchronization,
and a frequency offset Doppler/Clock estimation module that
estimates a frequency offset or a Doppler effects value. A
signal output from the synchronization module 1908 is
provided to a frame alignment module 1914 and a frequency
offset Doppler/Clock correction module 1918. A prefix
removal module 1915 removes a CP from the aligned frame.
Then, an FFT module 1922 Fourier-transforms the CP-removed
data. Then, an RS extraction module 1930 extracts an RS
signal spread in the frame and provides the RS signal to a
channel estimation module 1928. Then, a channel
reconstruction module 1926 reconstructs a radio channel using
the channel estimation result. The channel estimation
provides sufficient channel response information to enable an
STC decoder 1932 to decode the symbol according to an STC
encoding method used in the base station and to restore an
estimation corresponding to transmission bits. The symbol
obtained from the received signal and the channel estimation
result of each reception path are provided to the STC decoder
1932. The STC decoder 1932 then performs STC decoding on
each reception path to restore the obtained symbol. The STC
decoder 1932 can implement maximum likelihood decoding (MLD)
for blast-based transmission. The output of the STC decoder
1932 may be a Log-Likelihood Ratio (LLR) for each
transmission bit. A symbol de-interleaver module 1934 then
arranges STC-decoded symbols in the original order. Then, a
de-mapping module 1936 de-maps the symbols into a bitstream
and a bit de-interleaver module 1938 de-interleaves the
bitstream. A rate de-matching module 1940 then processes and
provides the de-interleaved bitstream to a channel decoder
module 1942 to restore scrambled data and a CRC checksum.
Here, the channel decoder module 1942 may use turbo decoding.
A CRC module 1944 then removes the CRC checksum and checks
the scrambled data according to a conventional method. A de-
scrambling module 194 6 then reconstructs the CRC-checked data
into original data 1948.
The above embodiments are provided by combining
components and features of the present invention in specific
forms. The components or features of the present invention
should be considered optional if not explicitly stated
otherwise. The components or features may be implemented
without being combined with other components or features.
The embodiments of the present invention may also be provided
by combining some of the components and/or features. The
order of the operations described above in the embodiments of
the present invention may be changed. Some components or
features of one embodiment may be included in another
embodiment or may be replaced with corresponding components
or features of another embodiment. It will be apparent that
claims which are not explicitly dependent on each other can
be combined to provide an embodiment or new claims can be
added through amendment after this application is filed.
The embodiments of the present invention have been
described focusing mainly on the data communication
relationship between a mobile station (MS) and a Base Station
(B3). Specific operations which have been described as being
performed by the BS may also be performed by an upper node as
needed. That is, it will be apparent to those skilled in the
art that the BS or any other network node may perform various
operations for communication with terminals in a network
including a number of network nodes including BSs. The term
"base station (BS)" may be replaced with another term such as
'fixed station", 'Node B", "eNode B (eNB)", or "access point".
The term "mobile station (MS)" may also be replaced with
another term such as "user equipment (UE)", "terminal", or
"mobile subscriber station (MSS)".
The embodiments of the present invention can be
implemented by hardware, firmware, software, or any
combination thereof. In the case where the present invention
is implemented by hardware, an embodiment of the present
invention may be implemented by one or more application
specific integrated circuits (ASICs), digital signal
processors (DSPs), digital signal processing devices (DSPDs),
programmable logic devices (PLDs), field programmable gate
arrays (FPGAs), processors, controllers, microcontrollers,
microprocessors, or the like.
In the case where the present invention is implemented
by firmware or software, the embodiments of the present
invention may be implemented in the form of modules,
processes, functions, or the like which perform the features
or operations described above. Software code can be stored
in a memory unit so as to be executed by a processor. The
memory unit may be located inside or outside the processor
and can communicate data with the processor through a variety
of known means.
Those skilled in the art will appreciate that the
present invention may be embodied in other specific forms
than those set forth herein without departing from the spirit
of the present invention. The above description is therefore
to be construed in all aspects as illustrative and not
restrictive. The scope of the invention should be determined
by reasonable interpretation of the appended claims and all
changes coming within the equivalency range of the invention
are intended to be embraced in the scope of the invention.
As is apparent from the above description, the present
invention provides a basic unit and a pilot structure that
can reduce pilot overhead in uplink and can also guarantee
excellent channel estimation. The basic unit and the pilot
structure according to the present invention reduce pilot
overhead of an OFDM(A) system, thereby improving system
performance, and keeps uniform time/frequency spacings,
thereby guaranteeing channel estimation performance, and can
be applied to a base station, a terminal, or the like which
are compatible with IEEE 802.16m.
WHAT IS CLAIMED IS:
1. A method of transmitting a basic unit in uplink by
a mobile station (MS) in an Orthogonal Frequency Division
Multiple Access (OFDMA) wireless communication system, the
method comprising:
forming the basic unit which size is 4 subcarriers by 6
OFDMA symbols, the basic unit containing a plurality of pilot
and data resource elements (REs);
configuring the pilot REs for multiple antennas in the
basic unit at intervals of 3 subcarriers in a frequency axis
and at intervals of 5 OFDMA symbols in a time axis; and
transmitting the basic unit in uplink,
wherein the RE is a time-frequency resource defined by
one OFDMA symbo] and one subcarrier,
wherein the pilot and data REs are configured in the
basic unit as in Pattern Table 2 expressed as follows:

where "P0" and "P1" indicate respective pilot REs for
antenna ports 0 and 1, "-" indicates the data RE, "s"
indicates an OFDMA symbol index, and "SC" indicates a
subcarrier index.
2. The method of claim 1, wherein the basic unit is an
uplink tile.
3. The method of claim 1, wherein the basic unit is an
uplink partial usage of subchannel (PUSC) tile.
4. The method of claim 1, wherein a certain number of
the basic units form a larger resource unit.
5. The method of claim 4, wherein the basic units
forming the larger resource unit are contiguous in the
frequency domain.
6. The method of claim 4, wherein the basic units
forming the larger resource unit are distributed in - the
frequency domain.
7. The method of claim 1, wherein the antenna port 0
and the antenna port 1 are replaced with each other.
8. The method of claim 1, wherein locations of the
pilot REs are cyclically shifted in the frequency domain or
in the time domain.
9. The method of claim 1, wherein the Pilot REs are
power boosted with power of data REs in the same OFDMA symbol.
10. The method of claim 1, further comprising mapping
pilot and data symbols to corresponding pilot and data REs,
respectively.
11. The method of claim 1, wherein the pilot REs are
used for dedicated pilot.
12. The method of claim 1, wherein transmit diversity
scheme or spatial multiplexing (SM) is independently applied
to the each basic unit.
13. The method of claim 12, wherein the transmit
diversity scheme includes space time block code (STBC), space
frequency block code (SFBC), cyclic delay diversity (CDD) or
any combination thereor.
14. (New) A mobile station (MS) configured to transmit
a basic unit in uplink in an Orthogonal Frequency Division
Multiple Access (OFDMA) wireless communication system, the MS
comprising:
baseband processor for digital signal processing; and
transmit circuitry for receiving baseband signals from
the baseband processor and transmitting radio signals in the
uplink via a plurality of antennas,
wherein the baseband processor forms the basic unit
which size is 4 subcarriers by 6 OFDMA symbols, the basic
unit containing a plurality of pilot and data resource
elements (REs) ,
wherein the baseband processor configures the pilot REs
for multiple antennas in the basic unit at intervals of 3
subcarriers in a frequency axis and at intervals of 5 OFDMA
symbols in a time axis,
wherein the RE is a time-frequency resource defined by
one OFDMA symbol and one subcarrier, and
wherein the pilot and data REs are configured in the
basic unit as in Pattern Table 2 expressed as follows:

where "P0" and "P1" indicate respective pilot REs for
antenna ports 0 and 1, "-" indicates the data RE, "s"
indicates an OFDMA symbol index, and "SC" indicates a
subcarrier index.
15. (New) The MS of claim 14, wherein the basic unit is
an uplink tile.

A method for uplink transmission in an OFDMA system is provided. The subcarrier transmission method includes
arranging 4 pilot REs at different positions of a frequency axis in a basic unit when the basic unit includes 4 subcarriers on the frequency
axis and 6 OFDM(A) symbols in a time axis, arranging data REs at remaining positions of the basic unit, and transmitting
the basic unit to a receiving end.

Documents:

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Patent Number 271780
Indian Patent Application Number 2753/KOLNP/2010
PG Journal Number 10/2016
Publication Date 04-Mar-2016
Grant Date 04-Mar-2016
Date of Filing 27-Jul-2010
Name of Patentee LG ELECTRONICS INC
Applicant Address 20, YEOUIDO-DONG, YEONGDEUNGPO-GU, SEOUL 150-721 REPUBLIC OF KOREA
Inventors:
# Inventor's Name Inventor's Address
1 NOH, MIN SEOK LG INSTITUTE, HOGYE 1 (IL)-DONG, DONGAN-GU, ANYANG-SI, GYEONGGI-DO 431-080, REPUBLIC OF KOREA
2 KWON, YEONG HYEON LG INSTITUTE, HOGYE 1 (IL)-DONG, DONGAN-GU, ANYANG-SI, GYEONGGI-DO 431-080, REPUBLIC OF KOREA
3 KWAK, JIN SAM LG INSTITUTE, HOGYE 1 (IL)-DONG, DONGAN-GU, ANYANG-SI, GYEONGGI-DO 431-080, REPUBLIC OF KOREA
4 CHOI, JIN SOO LG INSTITUTE, HOGYE 1 (IL)-DONG, DONGAN-GU, ANYANG-SI, GYEONGGI-DO 431-080, REPUBLIC OF KOREA
5 KIM, DONG CHEOL LG INSTITUTE, HOGYE 1 (IL)-DONG, DONGAN-GU, ANYANG-SI, GYEONGGI-DO 431-080, REPUBLIC OF KOREA
6 MOON, SUNG HO LG INSTITUTE, HOGYE 1 (IL)-DONG, DONGAN-GU, ANYANG-SI, GYEONGGI-DO 431-080, REPUBLIC OF KOREA
7 HAN, SEUNG HEE LG INSTITUTE, HOGYE 1 (IL)-DONG, DONGAN-GU, ANYANG-SI, GYEONGGI-DO 431-080, REPUBLIC OF KOREA
8 LEE, HYUN WOO LG INSTITUTE, HOGYE 1 (IL)-DONG, DONGAN-GU, ANYANG-SI, GYEONGGI-DO 431-080, REPUBLIC OF KOREA
PCT International Classification Number H04L 27/26
PCT International Application Number PCT/KR2009/000759
PCT International Filing date 2009-02-18
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 10-2009-0012948 2009-02-17 U.S.A.
2 61/029,574 2008-02-19 U.S.A.
3 10-2008-0044045 2008-05-13 U.S.A.
4 61/095,608 2008-09-09 U.S.A.