KR101526969B1 - Method for transmitting pilot sub-carrier for uplink on OFDM system - Google Patents

Abstract

A pilot subcarrier transmission method for uplink is disclosed. A method for transmitting a pilot subcarrier for uplink according to an embodiment of the present invention includes allocating two pilot subcarriers at the same position on a time axis while maximally spacing the frequency axis of the base unit and transmitting data subcarriers And transmitting the basic unit to a receiving end. According to embodiments of the present invention, the performance of a system can be improved by reducing a pilot overhead of an OFDM system by applying a pilot structure capable of achieving optimal channel estimation performance with a minimum pilot in an uplink channel, / Frequency interval can be maintained at a constant interval to guarantee the performance of channel estimation. In case of using a plurality of transmit antennas in the uplink, a case where a single transmit antenna is used, It has the effect of enabling support.

OFDM, pilot sub-carrier, pilot overhead, pilot structure, MIMO, pilot allocation

Description

[0001] The present invention relates to a method of transmitting pilot subcarriers for an uplink in an OFDM system,

The present invention relates to a pilot structure of an OFDM system, and more particularly to a base unit and a pilot structure capable of lowering a pilot overhead in an uplink and ensuring an excellent channel estimation.

The current IEEE 802.16e system includes a tile and pilot structure as shown in FIG. 1 as an uplink PUSC (Partial Usage of SubChannel) structure.

1 shows a case where one transmitting antenna is considered. The basic unit structure of this uplink PUSC has a pilot overhead of 33.33%.

The uplink tile structure used in the current IEEE 802.16e system has a pilot overhead of 33.33% per transmit antenna considering only one transmit antenna. This results in a significant overhead of pilot versus data used in conventional OFDM systems. This pilot overhead reduces link throughput, resulting in degraded performance of the system.

According to an aspect of the present invention, there is provided a method of transmitting a pilot subcarrier for an uplink, which can realize an optimal channel estimation performance with a minimum pilot in an uplink channel.

According to an aspect of the present invention, there is provided a method of transmitting pilot subcarriers for an uplink, the method comprising the steps of: allocating two pilot subcarriers at the same position on a time axis, Arranging data subcarriers in a remaining position of the unit, and transmitting the basic unit to a receiving end.

According to another aspect of the present invention, there is provided a method of transmitting pilot subcarriers for an uplink according to an embodiment of the present invention, which includes arranging two pilot subcarriers at different positions on a time axis of a base unit, And transmitting the basic unit to a receiving end.

Preferably, in the process of arranging the pilot subcarriers, the two pilot subcarriers may be arranged at different positions on the frequency axis and the time axis.

Preferably, in the process of arranging the pilot subcarriers, the two pilot subcarriers may be disposed at positions that are spaced apart from each other by a maximum distance along the frequency axis and the time axis.

According to another aspect of the present invention, there is provided a method of transmitting pilot subcarriers for uplink, the method comprising: arranging three pilot subcarriers at different positions along a time axis of a base unit; Arranging data subcarriers, and transmitting the base unit to a receiving end.

Preferably, in the process of arranging the pilot subcarriers, one of the three pilot subcarriers is located at the same position on the frequency axis, and the remaining pilot subcarriers are located on the same frequency axis as the positions of the pair of pilot subcarriers. Position.

Preferably, in the process of arranging the pilot subcarriers, the pair of pilot subcarriers and the remaining pilot subcarriers may be disposed at positions that are maximally spaced from each other in the frequency axis.

According to another aspect of the present invention, there is provided a method of transmitting pilot subcarriers for uplink, comprising the steps of: receiving pilot subcarriers for a first antenna and pilot signals for a second antenna, Arranging subcarriers symmetrically with respect to each other, arranging data subcarriers in a remaining position of the base unit, and transmitting the pilot subcarriers to a receiving end via corresponding antennas.

Preferably, the pilot subcarrier for the first antenna and the pilot subcarrier for the second antenna may be arranged at a position excluding the subcarrier position of the edge of the base unit in the process of arranging the pilot subcarrier.

Preferably, the pilot subcarrier for the first antenna and the pilot subcarrier for the second antenna are located at a maximum spacing along the frequency axis in the process of arranging the pilot subcarriers.

According to another aspect of the present invention, there is provided a method for transmitting pilot subcarriers for uplink, the method comprising: receiving pilot subcarriers for a first antenna and pilot subcarriers for a first antenna at different positions on a time axis of the base unit; 2 antennas symmetrically to each other, arranging data subcarriers in the remaining positions of the basic unit, and transmitting the pilot subcarriers to the receiving end via corresponding antennas while transmitting the basic unit.

Preferably, the pilot subcarrier for the first antenna and the pilot subcarrier for the second antenna are arranged at positions which are spaced apart from each other by a maximum frequency axis or a time axis in the process of arranging the pilot subcarriers.

According to another aspect of the present invention, there is provided a method of transmitting pilot subcarriers for uplink, the method comprising: arranging two pilot subcarriers for a first antenna at different positions on a time axis of the base unit; A pilot subcarrier for a second antenna is arranged at a subcarrier position on a frequency axis that is symmetric with the position of the pilot subcarrier for the first antenna in the basic unit, data subcarriers are arranged at the remaining positions of the basic unit, And transmitting the pilot subcarriers to the receiver through the corresponding antennas while transmitting the pilot subcarriers.

Preferably, the pilot subcarrier for the first antenna is located at a position where the pilot subcarriers for the first antenna are spaced apart from each other by a maximum distance in the process of disposing the pilot subcarrier for the first antenna.

According to embodiments of the present invention, the performance of a system can be improved by reducing a pilot overhead of an OFDM system by applying a pilot structure capable of achieving optimal channel estimation performance with a minimum pilot in an uplink channel, / Frequency interval can be maintained at a constant interval to guarantee the performance of channel estimation. In case of using a plurality of transmit antennas in the uplink, a case where a single transmit antenna is used, It has the effect of enabling support.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. However, the following embodiments of the present invention may be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below.

Embodiments of the present invention provide a basic unit and pilot structure for a structure capable of lowering pilot overhead and guaranteeing superior performance for channel estimation in an uplink when an OFDM system is used.

In the embodiments of the present invention, the coherent time is considered in order to enable robust channel estimation in the case of low speed or high speed in the time domain in the base unit, . In the frequency domain, pilot subcarriers are allocated on the frequency axis in order to enable robust channel estimation by various delay spreads and considering a coherent bandwidth. It also provides a possible basic unit and pilot structure that can improve channel estimation using pilots in successive base units when consecutive base units are allocated on the time / frequency axis.

2 to 7 show an example in which one pilot is arranged in the basic unit.

In the structures of FIGS. 2 to 7, the pilot overhead is 8.3%, and the pilot overhead can be reduced to 1/4 compared with the conventional IEEE 802.16e uplink PUSC structure using one pilot subcarrier per basic unit. Further, in terms of robustly channel estimating the entire data subcarriers belonging to the base unit with one pilot subcarrier per basic unit to a low-speed user case and a high-speed user case, 2 and 3 in which the pilot is located in the middle of the time axis (symbol 1) in the unit structure is preferable. Also, in order to guarantee robust channel estimation performance in consideration of frequency selectivity in channel estimation on the frequency axis, as shown in FIGS. 2, 5 and 6, the center part of the frequency domain, that is, It is preferable to allocate pilots at the third frequency location.

2 to 7 can be expressed as shown in Equation (1).

GK + subcarrier_offset

G denotes a subcarrier interval between two pilots in one OFDM symbol. K is an index (K = {0, 1, 2, ...) with respect to the number of pilots in one OFDM symbol. Subcarrier_offset denotes a subcarrier interval from the first subcarrier to the assigned pilot position in a unit of a base unit. K has an integer value of 0 or more.

2 to 7 are for the case where G is 4 in Equation (1).

According to the above equation, the left arrangement of FIG. 2 is when Subcarrier_offset = 1 and s = 1, and the right arrangement of FIG. 2 is when Subcarrier_offset = 2 and s = 1. Where s = [OFDM symbol index] mod 3, and the OFDM symbol index has an integer value of zero or more.

The left arrangement in FIG. 3 is when Subcarrier_offset = 0 and s = 1, and the right arrangement in FIG. 3 is when Subcarrier_offset = 3 and s = 1. Where s = [OFDM symbol index] mod 3, and the OFDM symbol index has an integer value of zero or more.

2 to 3 can be regarded as a case where pilots are allocated only to odd OFDM symbol indexes.

The left arrangement in Fig. 4 is when Subcarrier_offset = 3 and s = 0, and the right arrangement in Fig. 4 is when Subcarrier_offset = 0 and s = 2. Where s = [OFDM symbol index] mod 3, and the OFDM symbol index has an integer value of zero or more.

The left arrangement of FIG. 5 is when Subcarrier_offset = 2 and s = 0, and the right arrangement of FIG. 5 is when Subcarrier_offset = 1 and s = 2. Where s = [OFDM symbol index] mod 3, and the OFDM symbol index has an integer value of zero or more.

The left arrangement in Fig. 6 is when Subcarrier_offset = 1 and s = 0, and the right arrangement in Fig. 6 is when Subcarrier_offset = 2 and s = 2. Where s = [OFDM symbol index] mod 3, and the OFDM symbol index has an integer value of zero or more.

The left arrangement in Fig. 7 is when Subcarrier_offset = 0 and s = 0, and the right arrangement in Fig. 7 is when Subcarrier_offset = 3 and s = 2. Where s = [OFDM symbol index] mod 3, and the OFDM symbol index has an integer value of zero or more.

On the other hand, when consecutive resources on the frequency axis and the time axis are used, that is, when the basic units are continuously allocated in the frequency domain and when the basic units are consecutively allocated for a certain OFDM symbol, In the case of performing channel estimation using all of the pilots, it is appropriate to allocate pilots as shown in FIG. 4 or FIG.

8 to 13 show an example in which two pilots are arranged in a basic unit according to an embodiment of the present invention.

8 to 13, the pilot overhead is 16.67%, and the pilot overhead can be reduced to 1/2 as compared with the existing IEEE 802.16e uplink PUSC structure using two pilot subcarriers per basic unit. Also, in the case where the data subcarriers of the base unit have two pilot subcarriers per basic unit and channel estimation is performed robustly to the low-speed user case and the high-speed user case, it is preferable that the coherent time is dispersed over the time axis . That is, as shown in FIG. 9 and FIG. 11 to FIG. 13, one pilot may be allocated to the symbol 0 and one pilot may be allocated to the symbol 2. In this case, the pilots are placed at positions that are spaced apart from each other by a maximum distance along the time axis of the base unit.

In order to guarantee a robust channel estimation performance in consideration of a coherent band due to a delay spread in channel estimation on the frequency axis, as shown in FIGS. 8, 9 and 10, It is preferable to allocate one pilot subcarrier and allocate one pilot at the fourth frequency position. In this case, the pilots are disposed at positions that are spaced apart from each other by a maximum distance along the frequency axis of the base unit.

The arrangement of FIG. 8 and FIG. 10 can be expressed as shown in Equation (2).

3K - 2 * floor (K / 2)

K denotes a subcarrier index in one OFDM symbol, and subcarrier_offset denotes a subcarrier interval from the first subcarrier to the assigned pilot position in units of a base unit. K has an integer value of 0 or more.

FIG. 8 shows a case where s = 1, that is, a pilot is allocated only in an odd number OFDM symbol index.

The left arrangement in FIG. 10 corresponds to when s = 2, and the right arrangement in FIG. 10 corresponds to when s = 0.

9, 11, 12 and 13 can be expressed as Equation (1), where G is 4 in Equation (1), and pilots are allocated only to even-numbered OFDM symbol indexes.

The left arrangement in Fig. 9 is when Subcarrier_offset = 0, s = 0, or Subcarrier_offset = 3 and s = 2. The right arrangement in Fig. 9 is when Subcarrier_offset = 3, s = 0, or Subcarrier_offset = 0 and s = 2. Where s = [OFDM symbol index] mod 3, and the OFDM symbol index has an integer value of zero or more.

The left arrangement in FIG. 11 is when Subcarrier_offset = 2, s = 0, or Subcarrier_offset = 0 and s = 2. The right arrangement in Fig. 11 is when Subcarrier_offset = 0, s = 0, or Subcarrier_offset = 2 and s = 2. Where s = [OFDM symbol index] mod 3, and the OFDM symbol index has an integer value of zero or more.

The left arrangement in FIG. 12 is when Subcarrier_offset = 3, s = 0, or Subcarrier_offset = 1 and s = 2. The right arrangement in Fig. 12 is when Subcarrier_offset = 1, s = 0, or Subcarrier_offset = 3 and s = 2. Where s = [OFDM symbol index] mod 3, and the OFDM symbol index has an integer value of zero or more.

The left arrangement in Fig. 13 is when Subcarrier_offset = 2, s = 0, or Subcarrier_offset = 1 and s = 2. The right arrangement in Fig. 13 is when Subcarrier_offset = 1, s = 0, or Subcarrier_offset = 2 and s = 2. Where s = [OFDM symbol index] mod 3, and the OFDM symbol index has an integer value of zero or more.

On the other hand, when consecutive resources on the frequency axis and the time axis, that is, basic units are continuously allocated in the frequency domain or base units are continuously allocated during certain OFDM symbols, all of the pilots of the continuously allocated base units are used, If the estimation is carried out, the structures of Figs. 8 to 13 are all appropriate.

Further, when the basic unit is continuously allocated in the frequency axis, the structure of Fig. 8 can be somewhat modified. That is, the pilot of the first frequency position may be moved to the second frequency position or the pilot of the fourth frequency position may be moved to the third frequency position in order to maintain the frequency interval between pilots in FIG. This deformed structure is repeatedly applied to successive basic units.

Figs. 14 to 16 show an example in which three pilots are arranged in a basic unit according to another embodiment of the present invention.

14 to 16 show a structure in which one pair of three pilot subcarriers is arranged at the same position on the frequency axis and the remaining pilot subcarriers are arranged at positions on the frequency axis different from the positions of the pair of pilot subcarriers.

14 to 16, the pilot overhead is reduced to 3/4 as compared with the conventional IEEE 802.16e uplink PUSC structure using 3 pilot subcarriers per base unit. Further, in terms of robustly channel estimating the entire data subcarriers belonging to the basic unit using the three pilot subcarriers per basic unit with respect to the low-speed user case and the high-speed user case, the coherent time of the basic unit structure is maximized It is preferable to arrange one pilot subcarrier for every symbol in a form distributed over the time axis. That is, it is appropriate to allocate one pilot at the position of the symbol 0, one pilot at the position of the symbol 1, and one pilot at the position of the symbol 2.

In order to ensure robust channel estimation performance in consideration of the coherent band due to delay spread in the channel estimation on the frequency axis, as shown in FIG. 14, the first frequency position and the fourth frequency position It is preferable to assign a pilot to the pilot.

14, 15, and 16 can be expressed as Equation (1), where G is 4 in Equation (1), and one pilot is allocated to all OFDM symbol indexes.

The left arrangement in Fig. 14 is when Subcarrier_offset = 0, s = 0, 2, Subcarrier_offset = 3, s = 1. The right arrangement in Fig. 14 is when Subcarrier_offset = 3, s = 0, 2, or Subcarrier_offset = 0, s = 1. Where s = [OFDM symbol index] mod 3, and the OFDM symbol index has an integer value of zero or more.

The left arrangement in FIG. 15 is when Subcarrier_offset = 2, s = 0, 2, or Subcarrier_offset = 0, s = 1. The right arrangement in Fig. 15 is when Subcarrier_offset = 3, s = 0, 2, or Subcarrier_offset = 1 and s = 1. Where s = [OFDM symbol index] mod 3, and the OFDM symbol index has an integer value of zero or more.

The left arrangement in Fig. 16 is when Subcarrier_offset = 0, s = 0, 2, Subcarrier_offset = 2, s = 1. The right arrangement in Fig. 16 is when Subcarrier_offset = 1, s = 0, 2, Subcarrier_offset = 3, s = 1. Where s = [OFDM symbol index] mod 3, and the OFDM symbol index has an integer value of zero or more.

On the other hand, when consecutive resources on the frequency axis and the time axis, that is, basic units are continuously allocated in the frequency domain or base units are continuously allocated during certain OFDM symbols, all of the pilots of the continuously allocated base units are used, If the estimation is carried out, the structures of Figs. 14 to 16 are all appropriate.

The base units and pilot structures of FIGS. 2-16 may be repeatedly applied in the time / frequency domain within a frame or subframe. Further, when the basic unit is repeatedly allocated in the time / frequency domain, any one of the two basic unit structures in a symmetric relationship is arranged in an even slot, and an odd slot ) Can be designed so that the same time interval / frequency spacing is maintained in units of two slots.

Hereinafter, a basic unit and a pilot structure for a case where there are two uplink transmission antennas in a case where a plurality of transmission antennas are used in the uplink will be described. It is desirable to construct a pilot structure while maintaining commonality with a single transmit antenna for a case where there are a plurality of transmit antennas. It is also desirable to design so that the time interval and the frequency interval between pilots in successive basic units are maintained when the basic unit is repeated in the time / frequency domain for each antenna.

FIGS. 17 to 22 illustrate examples in which the pilot structure of FIG. 2 to FIG. 7 is applied to multiple antennas.

17 to 22 show a pilot structure for two transmission antennas, in which one pilot sub-carrier for Tx ant1 and one pilot for the second antenna are arranged at different positions on the time axis of the basic unit, (Pilot sub-carrier for Tx ant2) are arranged symmetrically with respect to each other. Where the pilot for the first antenna may be repositioned with the pilot for the second antenna.

17-22 illustrate the use of one pilot subcarrier per base unit in a single transmit antenna, keeping the pilot overhead per antenna at 8.33% and reducing the overall pilot overhead to 16.67%

The pilot subcarriers arranged in this manner are transmitted to the receiving end via the corresponding antenna at the time of transmission of the base unit. In addition, data is not transmitted through the second antenna to the resource that transmits the pilot subcarrier for the first antenna. Conversely, for the resource that transmits the pilot subcarrier for the second antenna, no data is transmitted through the first antenna.

17 shows a structure in which pilots are arranged in the middle of the time axis and the frequency axis. FIGS. 18, 19 and 22 show a structure in which pilots are arranged at positions that are spaced apart from each other by a maximum distance along the frequency axis. FIGS. 19, 20, 21, and 22 show a structure in which pilots are disposed at positions that are spaced apart from each other at a maximum along the time axis.

In the case of FIGS. 17 to 21, pilot values are assigned according to the antenna indexes in the case of a G value of 4 in the same manner as in Equation (1).

The left arrangement in FIG. 17 is when Subcarrier_offset = 1 and s = 1 for the first antenna, or when Subcarrier_offset = 2 and s = 1 for the second antenna. The right arrangement in Fig. 17 is when Subcarrier_offset = 2 and s = 1 for the first antenna or Subcarrier_offset = 1 and s = 1 for the second antenna. Where s = [OFDM symbol index] mod 3, and the OFDM symbol index has an integer value of zero or more.

The left arrangement in FIG. 18 is when Subcarrier_offset = 0, s = 1 for the first antenna, or Subcarrier_offset = 3 and s = 1 for the second antenna. The right arrangement in FIG. 18 is when Subcarrier_offset = 3 and s = 1 for the first antenna, or when Subcarrier_offset = 0 and s = 1 for the second antenna. Where s = [OFDM symbol index] mod 3, and the OFDM symbol index has an integer value of zero or more.

The left arrangement in FIG. 19 is when Subcarrier_offset = 3 and s = 0 for the first antenna, or when Subcarrier_offset = 0 and s = 2 for the second antenna. The right arrangement in Fig. 19 is when Subcarrier_offset = 0 and s = 2 for the first antenna, and Subcarrier_offset = 3 and s = 0 for the second antenna. Where s = [OFDM symbol index] mod 3, and the OFDM symbol index has an integer value of zero or more.

The left arrangement in FIG. 20 is when Subcarrier_offset = 2 and s = 0 for the first antenna, or when Subcarrier_offset = 1 and s = 2 for the second antenna. 20 is when Subcarrier_offset = 1 and s = 2 for the first antenna, or when Subcarrier_offset = 2 and s = 0 for the second antenna. Where s = [OFDM symbol index] mod 3, and the OFDM symbol index has an integer value of zero or more.

The left arrangement in FIG. 21 is when Subcarrier_offset = 1 and s = 0 for the first antenna, or when Subcarrier_offset = 2 and s = 2 for the second antenna. The right arrangement in FIG. 21 is when Subcarrier_offset = 2 and s = 2 for the first antenna, or when Subcarrier_offset = 1 and s = 0 for the second antenna. Where s = [OFDM symbol index] mod 3, and the OFDM symbol index has an integer value of zero or more.

The left arrangement in FIG. 22 is when Subcarrier_offset = 0 and s = 0 for the first antenna, or when Subcarrier_offset = 3 and s = 2 for the second antenna. The right arrangement in FIG. 22 is when Subcarrier_offset = 3 and s = 2 for the first antenna, or when Subcarrier_offset = 0 and s = 0 for the second antenna. Where s = [OFDM symbol index] mod 3, and the OFDM symbol index has an integer value of zero or more.

The basic unit and pilot structures of Figs. 17-22 may be repeatedly applied in the time / frequency domain within a frame or subframe. Further, when the basic unit is repeatedly allocated in the time / frequency domain, any one of the two basic unit structures in a symmetrical relationship is arranged in the even-numbered slot and the rest in the odd-numbered slot, So that the same time interval / frequency interval can be maintained.

Figs. 23 to 27 illustrate examples of applying the pilot structures of Figs. 8 to 13 to multiple antennas.

23 to 27 show that two pilot subcarriers for the first antenna are arranged at different positions on the time axis of the base unit and the second subcarrier is located at a subcarrier position on the frequency axis symmetric with the position of the pilot subcarrier for the first antenna in the base unit And the pilot subcarriers for the antenna are arranged. Based on using two pilot subcarriers per base unit in a single transmit antenna, the pilot overhead per antenna can be maintained at 16.67% and the total pilot overhead can be reduced to 33.33%.

In the case of FIGS. 23 to 27, pilot values are assigned according to the antenna indexes in the case of a G value of 4 in the same manner as in Equation (1).

23, subcarrier_offset = 0, s = 0, or subcarrier_offset = 3, s = 2 for the first antenna, Subcarrier_offset = 3, s = 0 or Subcarrier_offset = 0, s = 2 . The right arrangement in Fig. 23 is when Subcarrier_offset = 3, s = 0 or Subcarrier_offset = 0 and s = 2 for the first antenna or Subcarrier_offset = 0, s = 0 or Subcarrier_offset = 3 and s = 2 . Where s = [OFDM symbol index] mod 3, and the OFDM symbol index has an integer value of zero or more.

The left arrangement in FIG. 24 is when subcarrier_offset = 0, s = 2 or subcarrier_offset = 3 and s = 2 for the first antenna, or when Subcarrier_offset = 0, s = 0 or Subcarrier_offset = 3 and s = . 24, subcarrier_offset = 0, s = 2, or subcarrier_offset = 3 and s = 2 for subcarrier_offset = 0, s = 0 or subcarrier_offset = 3 and s = 0 for the first antenna. . Where s = [OFDM symbol index] mod 3, and the OFDM symbol index has an integer value of zero or more.

The left arrangement in FIG. 25 is when subcarrier_offset = 2, s = 0 or subcarrier_offset = 0 and s = 2 for the first antenna or subcarrier_offset = 0, s = 0 or subcarrier_offset = 2 and s = 2 . 25, subcarrier_offset = 2, s = 0, or subcarrier_offset = 0 and s = 2 for subcarrier_offset = 0, s = 0 or subcarrier_offset = 2 and s = 2 for the first antenna. It is time. Where s = [OFDM symbol index] mod 3, and the OFDM symbol index has an integer value of zero or more.

The left arrangement in FIG. 26 is when Subcarrier_offset = 3, s = 0 or Subcarrier_offset = 1 and s = 2 for the first antenna or Subcarrier_offset = 1, s = 0 or Subcarrier_offset = 3 and s = 2 . 26 is a case where Subcarrier_offset = 1, s = 0 or Subcarrier_offset = 3 and s = 2 for the first antenna or Subcarrier_offset = 3, s = 0 or Subcarrier_offset = 1 and s = 2 . Where s = [OFDM symbol index] mod 3, and the OFDM symbol index has an integer value of zero or more.

27, subcarrier_offset = 1, s = 0, or subcarrier_offset = 2, s = 2 for the second antenna, or when Subcarrier_offset = 2, s = 0 or Subcarrier_offset = . 27 is subcarrier_offset = 1, s = 0 or subcarrier_offset = 2, s = 2 for the first antenna, or Subcarrier_offset = 2 and s = 0 for the second antenna, or Subcarrier_offset = 1 and s = 2. Where s = [OFDM symbol index] mod 3, and the OFDM symbol index has an integer value of zero or more.

The basic unit and pilot structures of FIGS. 23-27 may be repeatedly applied in the time / frequency domain within a frame or subframe. Further, when the basic unit is repeatedly allocated in the time / frequency domain, any one of the two basic unit structures in a symmetrical relationship is arranged in the even-numbered slot and the rest in the odd-numbered slot, So that the same time interval / frequency interval can be maintained.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that such modifications are within the technical scope of the present invention. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

The present invention relates to a basic unit and a pilot structure for lowering a pilot overhead in an uplink and ensuring an excellent channel estimation. It is possible to improve the performance of a system by reducing a pilot overhead of an OFDM system, The performance of the channel estimation can be ensured by maintaining the intervals at predetermined intervals. The present invention can be applied to a plurality of transmission antennas, and can be applied to devices such as base stations and terminals having IEEE 802.16e and downward compatibility.

Figure 1 illustrates a conventional IEEE 802.16e tile and pilot structure.

2 to 7 show an example in which one pilot is arranged in the basic unit.

8 to 13 show an example in which two pilots are arranged in a basic unit according to an embodiment of the present invention.

Figs. 14 to 16 show an example in which three pilots are arranged in a basic unit according to another embodiment of the present invention.

17 to 22 show an example of applying the pilot structure of FIG. 2 to FIG. 7 to multiple antennas according to another embodiment of the present invention.

23 to 27 show an example of applying the pilot structure of Figs. 8 to 13 to multiple antennas according to another embodiment of the present invention.

Claims (14)

delete delete delete delete A method for transmitting pilot subcarriers through an uplink base unit allocated on four subcarrier units on a frequency axis and three OFDM symbol units on a time axis, Wherein three pilot subcarriers are arranged at different positions on the time axis of the base unit, a pair of pilot subcarriers of the three pilot subcarriers are arranged at the same position on the frequency axis, and the remaining pilot subcarriers are allocated to the pair of pilot subcarriers At a position of a frequency axis different from the position of the frequency axis; Placing data subcarriers in remaining positions of the base unit; And Transmitting the basic unit to a receiving end And transmitting the pilot subcarrier for the uplink. delete 6. The method of claim 5, Wherein the pair of pilot subcarriers and the remaining pilot subcarriers are located at positions that are spaced apart from each other by a maximum distance along a frequency axis. A method for transmitting a pilot subcarrier through an uplink base unit allocated in units of four subcarriers on a frequency axis and three OFDM symbols on a time axis in a transmitter having a first antenna and a second antenna, Arranging one pilot subcarrier for the first antenna and one pilot subcarrier for the second antenna to be symmetrical to each other at the same position on the time axis of the base unit; Placing data subcarriers in remaining positions of the base unit; And And transmitting the pilot subcarriers to a receiving end via corresponding antennas And transmitting the pilot subcarrier for the uplink. 9. The method of claim 8, The step of arranging the pilot sub- And arranging the pilot subcarrier for the first antenna and the pilot subcarrier for the second antenna at a position excluding the subcarrier position of the edge of the basic unit. 9. The method of claim 8, The step of arranging the pilot sub- Wherein the pilot subcarrier for the first antenna and the pilot subcarrier for the second antenna are located at positions that are spaced apart from each other by a maximum distance along the frequency axis. A method for transmitting a pilot subcarrier through an uplink base unit allocated in units of four subcarriers on a frequency axis and three OFDM symbols on a time axis in a transmitter having a first antenna and a second antenna, Arranging one pilot subcarrier for the first antenna and one pilot subcarrier for the second antenna to be symmetrical to each other at different positions on the time axis of the base unit; Placing data subcarriers in remaining positions of the base unit; And And transmitting the pilot subcarriers to a receiving end via a corresponding antenna while transmitting the base unit And transmitting the pilot subcarrier for the uplink. 12. The method of claim 11, The step of arranging the pilot sub- Wherein the pilot subcarrier for the first antenna and the pilot subcarrier for the second antenna are located at positions which are spaced apart from each other by a maximum distance along the frequency axis or the time axis. A method for transmitting a pilot subcarrier through an uplink base unit allocated in units of four subcarriers on a frequency axis and three OFDM symbols on a time axis in a transmitter having a first antenna and a second antenna, Arranging two pilot subcarriers for the first antenna at different positions on the time axis of the base unit; Arranging a pilot subcarrier for a second antenna at a subcarrier position in a frequency axis symmetric with a position of the pilot subcarrier for the first antenna in the base unit; Placing data subcarriers in remaining positions of the base unit; And And transmitting the pilot subcarriers to the receiving end via the corresponding antenna while transmitting the base unit And transmitting the pilot subcarrier for the uplink. 14. The method of claim 13, The step of arranging the pilot subcarriers for the first antenna comprises: And arranging the pilot subcarriers for the first antenna at positions where the pilot subcarriers for the first antenna are spaced apart from each other by a maximum distance along the time axis.

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