KR20090089762A - Method for transmitting consecutive pilot sub-carrier on ofdm system - Google Patents

Abstract

A method for transmitting a consecutive pilot subcarrier wave in an OFDM system is provided to improve performance of a system by maintaining a time interval and a frequency interval into a fixed interval. A pilot subcarrier wave is transmitted through a consecutive base unit of an uplink. Four pilot subcarrier waves are arranged in a different position of a frequency axis in the base unit. Data subcarrier waves are arranged in a rest position of the base unit. The base unit is transmitted to a receiving end. The base unit is formed as a unit of four subcarrier waves into the frequency axis, and is formed as an OFDM symbol unit more than six into the time axis. Each pair of the four pilot subcarrier waves is arranged in the same position of the time axis.

Description

Method for transmitting consecutive pilot sub-carrier on OFDM system

The present invention proposes a basic unit and a pilot structure for a structure capable of lowering pilot overhead in uplink using an OFDM system and ensuring excellent performance for channel estimation.

The current IEEE 802.16e system includes a tile and pilot structure as shown in FIG. 1 as an uplink partial usage of subchannel (PUSC) structure. 1 is a case where one transmitting antenna is considered. This uplink PUSC basic unit structure 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% in the case of one transmission antenna considering only one transmission antenna. Therefore, the overhead of pilot versus data used in a conventional OFDM system is quite large. This pilot overhead reduces link throughput resulting in system degradation. In particular, when the basic unit is extended, such as IEEE 802.16m, reducing the overhead of the pilot is an issue.

An object of the present invention is to provide a continuous pilot subcarrier transmission method that can reduce the pilot overhead and ensure channel estimation performance even when the base unit of the uplink is extended on the time axis.

In order to achieve the above technical problem, in the continuous pilot subcarrier transmission method according to an embodiment of the present invention, when the base unit is composed of four subcarrier units on the frequency axis and six or more OFDM symbol units on the time axis, the basic Disposing four pilot subcarriers at different positions of the frequency axis in the unit, disposing data subcarriers at the remaining positions of the base unit, and transmitting the base unit to a receiving end.

Preferably, in the process of arranging the pilot subcarriers, the four pilot subcarriers may be arranged in pairs at the same position on the time axis.

Preferably, in the process of arranging the pilot subcarriers, at least two pilot subcarriers of the four pilot subcarriers may be arranged at positions of edges of the base unit.

Or, in order to achieve the above technical problem, the continuous pilot subcarrier transmission method according to an embodiment of the present invention when the base unit is composed of four subcarrier units on the frequency axis and six or more OFDM symbol units on the time axis, And placing four pilot subcarriers in the same position on a frequency axis in pairs in the base unit, placing data subcarriers in the remaining positions of the base unit, and transmitting the base unit to a receiving end.

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

Preferably, in the process of arranging the pilot subcarriers, the four pilot subcarriers may be arranged in pairs at the same position on the time axis.

Preferably, in the process of arranging the pilot subcarriers, at least two pilot subcarriers of the four pilot subcarriers may be arranged at positions of edges of the base unit.

Preferably, in the process of arranging the pilot subcarriers, the four pilot subcarriers may be disposed at positions except edges of the base unit.

In order to achieve the above technical problem, the continuous pilot subcarrier transmission method according to another embodiment of the present invention, if the base unit is composed of four subcarrier units on the frequency axis and six or more OFDM symbol units on the time axis, Disposing three pilot subcarriers at different positions of the time axis in the unit, disposing data subcarriers at the remaining positions of the base unit, and transmitting the base unit to a receiving end.

Preferably, in the process of arranging the pilot subcarriers, a pair of pilot subcarriers of the three pilot subcarriers are arranged at the same position on a frequency axis, and the remaining pilot subcarriers are located at different positions on the frequency axis with the pair of pilot subcarriers. Can be placed.

Preferably, in the process of arranging the pilot subcarriers, the pair of pilot subcarriers and the remaining pilot subcarriers may be arranged at positions spaced apart from each other at the maximum frequency axis.

In order to achieve the above technical problem, in the continuous pilot subcarrier transmission method according to another embodiment of the present invention, if the base unit is composed of four subcarrier units on the frequency axis and nine or more OFDM symbol units on the time axis, Arranging six pilot subcarriers to occupy all positions on the frequency axis of the base unit, arranging data subcarriers at the remaining positions of the base unit, and transmitting the base unit to a receiving end.

Or, in order to achieve the above technical problem, the continuous pilot subcarrier transmission method according to another embodiment of the present invention when the base unit is composed of four subcarrier units on the frequency axis and nine or more OFDM symbol units on the time axis And disposing six pilot subcarriers at both ends of the base unit on a frequency axis, disposing data subcarriers at the remaining positions of the base unit, and transmitting the base unit to a receiving end.

On the other hand, in order to achieve the above technical problem, in the continuous pilot subcarrier transmission method according to another embodiment of the present invention when the base unit is composed of four subcarrier units on the frequency axis and six OFDM symbol units on the time axis, Disposing two pilot subcarriers at different positions on a frequency axis and a time axis at the base unit, disposing data subcarriers at the remaining positions of the base unit, and transmitting the base unit to a receiving end.

On the other hand, in order to achieve the above technical problem, the continuous pilot subcarrier transmission method according to another embodiment of the present invention when the base unit is composed of four subcarrier units on the frequency axis and 12 OFDM symbol units on the time axis, Placing four pilot subcarriers in different positions on the frequency axis and time axis in the base unit, and placing data subcarriers in the remaining positions of the base unit. Transmitting the base unit to a receiving end.

According to embodiments of the present invention, even when the base unit of the uplink is extended on the time axis, the channel estimation is reduced by reducing the pilot overhead of the OFDM system, maintaining the time interval and the frequency interval at a constant interval, or by distributing the channel for easy channel estimation. The performance of the system is guaranteed, and the performance of the system can be improved.

Hereinafter, with reference to the drawings will be described a preferred embodiment of the present invention. However, embodiments of the present invention illustrated below may be modified in 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 in uplink of an OFDM system and ensuring excellent performance for channel estimation. In the embodiments of the present invention, the pilot subcarriers are allocated on the time axis in consideration of the coherent time to enable robust channel estimation in the time domain in the base unit in the time domain. In addition, in the frequency domain, a pilot subcarrier is allocated on the frequency axis in consideration of coherent bandwidth so that robust channel estimation is possible due to various delay spreads. In addition, when a continuous base unit is allocated on the time / frequency axis, a base unit and a pilot structure that can improve channel estimation performance using pilots of the continuous base units are provided.

2 to 6 show an example in which two pilots are arranged in the base unit.

2 to 6 show a case where consecutive basic units are allocated in four subcarrier multiples on the frequency axis and multiples of three on the time axis, with pilot overhead of 16.67%.

When two pilot subcarriers are used per base unit as shown in FIG. 2, the pilot overhead can be reduced to 1/2 compared to the conventional IEEE 802.16e uplink PUSC structure. Also, in the position of robustly estimating data subcarriers of the base unit for a low speed user case and a high speed user case using two pilot subcarriers per base unit, FIGS. 2 and FIG. As shown in Fig. 4, it is appropriate to distribute pilots at both ends of the time axis in the base unit, that is, the first and third symbols.

In addition, in order to ensure robust channel estimation performance in consideration of frequency selectivity in channel estimation on the frequency axis, pilots are first and fourth positions in the frequency domain, as shown in FIGS. 2, 3, and 5. It is preferable to assign.

3A and 3B may be expressed as Equation 1 below.

3K-2 * floor (K / 2)

K is the index (K = {0,1,2, ...) with respect to the number of pilots in one OFDM symbol.

3A and 3B illustrate a case in which pilots are allocated only when s = 1, that is, only an odd OFDM symbol index.

2, 4, 5, 6, 7, and 8b may be expressed as in Equation 2.

4K + subcarrier_offset

K is an index (K = {0,1,2, ...) regarding the number of pilots in one OFDM symbol, and subcarrier_offset means a subcarrier interval from an initial subcarrier to an allocated pilot position in a basic unit unit.

The left figure of FIG. 2 shows subcarrier_offset = 0 when s = 0, Subcarrier_offset = 3 when s = 2, the right figure of FIG. 2 shows subcarrier_offset = 0 when s = 0 and subcarrier_offset = 3. . Where s = [OFDM symbol index] mod 3 and the OFDM symbol index is {0,1,2, ...}.

In FIG. 4, the first picture on the left side is a case where subcarrier_offset = 0 when s = 0 and subcarrier offset = 2 when s = 2. The second figure from the left shows that subcarrier_offset = 2 when s = 0 and subcarrier_offset = 0 when s = 2. The third figure from the left shows that subcarrier_offset = 1 when s = 0 and subcarrier_offset = 3 when s = 2. The rightmost figure shows the case where subcarrier_offset = 3 when s = 0 and subcarrier_offset = 1 when s = 2. Where s = [OFDM symbol index] mod 3 and the OFDM symbol index is {0,1,2, ...}.

5 shows a case in which subcarrier_offset = 0 when s = 1 and subcarrier_offset = 3 when s = 2. 5 shows a case where subcarrier_offset = 0 when s = 0 and subcarrier_offset = 3 when s = 1. Where s = [OFDM symbol index] mod 3 and the OFDM symbol index is {0,1,2, ...}.

The first picture on the left side of FIG. 6 is a case where subcarrier_offset = 1 when s = 0 and subcarrier offset = 3 when s = 1. 6 shows a case where subcarrier_offset = 1 when s = 1 and subcarrier_offset = 3 when s = 2. 6 shows a case where subcarrier_offset = 0 when s = 0 and subcarrier_offset = 2 when s = 1. 6 shows a case in which subcarrier_offset = 0 when s = 1 and subcarrier_offset = 2 when s = 2. Where s = [OFDM symbol index] mod 3 and the OFDM symbol index is {0,1,2, ...}.

On the other hand, considering the case where the consecutive resources on the frequency axis and the time axis, that is, the base unit is continuously allocated to the frequency domain or the base unit is continuously allocated during a certain OFDM symbol, that is, used for the continuous base unit In the case of performing channel estimation using all pilots, a method of allocating different frequency positions and different OFDM symbol positions as shown in FIG. 6 may be sufficiently considered.

7 to 10b illustrate an example in which four pilots are arranged in a base unit according to an embodiment of the present invention.

7 to 10B illustrate a case in which consecutive basic units are allocated in units of multiples of 4 OFDM on the frequency axis and 6 OFDM on the time axis.

7, 8A, 8B and 10A show a structure in which four pilot subcarriers are arranged at different positions of the frequency axis in the base unit. In particular, FIGS. 7, 8A, 8B and 10A are structures that cannot be generated by repetition of the pilot structures shown in FIGS. 2 to 6. 9A, 9B and 10B show a structure in which four pilot subcarriers are arranged in pairs at the same position on the frequency axis in a base unit.

The first picture on the left of FIG. 7 is subcarrier_offset = 0 when s = 0, subcarrier offset = 2 when s = 1, subcarrier_offset = 1 when s = 4, and subcarrier offset = 3 when s = 5. to be. In the second figure from the left of FIG. 7, subcarrier_offset = 3 when s = 0, subcarrier offset = 1 when s = 1, subcarrier_offset = 2 when s = 4, and subcarrier offset = 0 when s = 5. to be. 7 shows a case where subcarrier_offset = 1 when s = 0, subcarrier_offset = 3 when s = 2, subcarrier_offset = 0 when s = 3, and subcarrier_offset = 2 when s = 5. . 7 shows a case in which the subcarrier_offset = 2 when s = 0, the subcarrier_offset = 0 when s = 2, the subcarrier_offset = 3 when s = 3, and the subcarrier_offset = 1 when s = 5. Where s = [OFDM symbol index] mod 6 and OFDM symbol index is {0,1,2, ...}.

8A may be expressed as Equation 3 below.

GK + subcarrier_offset

K is an index (K = {0,1,2, ...) regarding the number of pilots in one OFDM symbol, where G means a subcarrier interval between two pilots in one OFDM symbol. Equation 2 is a subset of Equation 3.

In FIG. 8A, the G value is 2, and the first figure on the left side of FIG. 8A is subcarrier_offset = 0 when s = 1 and subcarrier_offset = 1 when s = 4. The second figure on the left of FIG. 8A shows subcarrier_offset = 1 when s = 1 and subcarrier_offset = 0 when s = 4. Where s = [OFDM symbol index] mod 6 and OFDM symbol index is {0,1,2, ...}.

The first picture on the left side of FIG. 8B shows a case where subcarrier_offset = 1 when s = 1, subcarrier_offset = 3 when s = 2, subcarrier_offset = 0 when s = 3, and subcarrier_offset = 2 when s = 4. 8b shows a subcarrier_offset = 2 when s = 1, subcarrier_offset = 0 when s = 2, subcarrier_offset = 3 when s = 3, and subcarrier_offset = 1 when s = 4. Where s = [OFDM symbol index] mod 6 and OFDM symbol index is {0,1,2, ...}.

9A may be expressed as Equation 1 below.

In FIG. 9A, the pilot subcarriers are allocated only when s = 0 and 5. Where s = [OFDM symbol index] mod 6 and OFDM symbol index is {0,1,2, ...}.

9B, 10A, and 10B may be expressed by Equation 2. Equation 2 is a special case for the case where the G value is 4 in Equation 3.

The first picture on the left of FIG. 9B is subcarrier_offset = 0 when s = 0, subcarrier_offset = 3 when s = 1, subcarrier_offset = 0 when s = 4, and subcarrier_offset = 3 when s = 5. 9b shows subcarrier_offset = 3 when s = 0, subcarrier_offset = 0 when s = 1, subcarrier_offset = 3 when s = 4, and subcarrier_offset = 0 when s = 5. Where s = [OFDM symbol index] mod 6 and OFDM symbol index is {0,1,2, ...}.

The first picture on the left side of FIG. 10A shows subcarrier_offset = 0 when s = 0, subcarrier_offset = 2 when s = 2, subcarrier_offset = 1 when s = 3, and subcarrier_offset = 3 when s = 5. The second figure on the left side of FIG. 10B shows subcarrier_offset = 3 when s = 0, subcarrier_offset = 1 when s = 2, subcarrier_offset = 2 when s = 3, and subcarrier_offset = 0 when s = 5. Where s = [OFDM symbol index] mod 6 and OFDM symbol index is {0,1,2, ...}.

The first figure on the left side of FIG. 10B shows subcarrier_offset = 1 when s = 0, subcarrier_offset = 2 when s = 2, subcarrier_offset = 1 when s = 3, and subcarrier_offset = 2 when s = 5. The second figure on the left side of FIG. 10B shows subcarrier_offset = 2 when s = 0, subcarrier_offset = 1 when s = 2, subcarrier_offset = 2 when s = 3, and subcarrier_offset = 1 when s = 5. Where s = [OFDM symbol index] mod 6 and OFDM symbol index is {0,1,2, ...}.

On the other hand, Figures 8a and 9a is a structure suitable for a low-speed user case, Figure 10b is a structure that is suitable for a higher speed than the case of a low speed, and more suitable for a case where the delay spread is larger than a case where the delay spread is small .

According to the pilot structure of Figures 7-10B, the pilot overhead is 16.67%.

11 to 15 illustrate an example in which six pilots are arranged in a base unit according to another embodiment of the present invention.

11 to 15 show a case where consecutive base units are allocated in units of multiples of 9 OFDM symbols on a frequency axis and 4 subcarriers on a frequency axis, and pilot overhead is 16.67%.

FIG. 11 is a structure in which six pilot subcarriers are arranged to maintain the same time interval at frequency positions at both ends of the base unit in the frequency axis. FIG. 13 is designed to be more robust in the case of high speed than low speed by arranging pilot subcarriers at intervals of 2 OFDM symbols on a time axis. 12, 14, and 15 are structures in which six pilot subcarriers are arranged to occupy all positions on the frequency axis of the base unit.

11 is expressed as in Equation 1.

11 illustrates a case in which pilots are allocated only when s = 0, 4, 8, that is, when s is a multiple of four. Where s = [OFDM symbol index] mod 9 and OFDM symbol index is {0, 1, 2, ...}.

12, 13, 14, and 15, the position index of the pilot subcarrier is expressed as in Equation 4. Equation 3 is for the special case of Equation 4.

3K-2 * floor (K / 2) + subcarrier_offset

K is an index (K = {0,1,2, ...) regarding the number of pilots in one OFDM symbol, and subcarrier_offset means a subcarrier interval from an initial subcarrier to an allocated pilot position in a basic unit unit.

The first picture on the left of FIG. 12 is subcarrier_offset = 0 when s = 1, subcarrier_offset = 1 when s = 3, subcarrier_offset = 2 when s = 5, and subcarrier_offset = 0 when s = 7. The second figure from the left of FIG. 12 is subcarrier_offset = 0 when s = 1, subcarrier_offset = 0 when s = 3, subcarrier_offset = 1 when s = 5, and subcarrier_offset = 0 when s = 7. Where s = [OFDM symbol index] mod 9 and OFDM symbol index is {0, 1, 2, ...}.

The first picture on the left of FIG. 13 is subcarrier_offset = 0 when s = 1, subcarrier_offset = 0 when s = 3, subcarrier_offset = 3 when s = 5, and subcarrier_offset = 0 when s = 7. The second figure from the left of FIG. 13 is subcarrier_offset = 0 when s = 1, subcarrier_offset = 0 when s = 3, subcarrier_offset = 0 when s = 5, and subcarrier_offset = 0 when s = 7. Where s = [OFDM symbol index] mod 9 and OFDM symbol index is {0, 1, 2, ...}.

The first picture on the left of FIG. 14 is subcarrier_offset = 0 when s = 0, subcarrier_offset = 1 when s = 2, subcarrier_offset = 2 when s = 6, and subcarrier_offset = 0 when s = 8. The second figure on the left of FIG. 14 shows subcarrier_offset = 0 when s = 0, subcarrier_offset = 2 when s = 2, subcarrier_offset = 1 when s = 6, and subcarrier_offset = 0 when s = 8. Where s = [OFDM symbol index] mod 9 and OFDM symbol index is {0, 1, 2, ...}.

The first picture on the left of FIG. 15 is subcarrier_offset = 0 when s = 0, subcarrier_offset = 1 when s = 3, subcarrier_offset = 2 when s = 5, and subcarrier_offset = 0 when s = 8. The second figure from the left of FIG. 15 is subcarrier_offset = 0 when s = 0, subcarrier_offset = 0 when s = 3, subcarrier_offset = 1 when s = 5, and subcarrier_offset = 0 when s = 8. Where s = [OFDM symbol index] mod 9 and OFDM symbol index is {0, 1, 2, ...}.

16 illustrates an example in which eight pilots are arranged in a base unit according to another embodiment of the present invention.

16 is expressed as in Equation 1.

The upper left picture of FIG. 16 shows a case of assigning pilot only when s = 0, 4, 7, and 11, and the right picture of FIG. 16 shows a case of assigning pilot only when s = 0, 3, 8, and 11. 16 shows a case in which pilots are allocated only when s = 2, 4, 7, and 9. Where s = [OFDM symbol index] mod 12 and the OFDM symbol index is {0,1,2, ...}.

16 shows a case in which a basic unit is allocated in units of 4 subcarriers and 12 OFDM symbols, and pilot overhead is 12.5%. The example structure of FIG. 16 is appropriate for the low speed case.

17 to 19 illustrate an example in which three pilots are arranged in a base unit according to another embodiment of the present invention.

17 to 19 may be expressed by Equation 2.

The first picture on the left of FIG. 17 is subcarrier_offset = 0 when s = 0, subcarrier_offset = 3 when s = 2, and subcarrier_offset = 0 when s = 4. 17 shows a subcarrier_offset = 3 when s = 0, a subcarrier_offset = 0 when s = 2, and a subcarrier_offset = 3 when s = 4. 17 shows a subcarrier_offset = 0 when s = 1, a subcarrier_offset = 0 when s = 3, and a subcarrier_offset = 0 when s = 5. The fourth figure from the left of FIG. 17 is subcarrier_offset = 3 when s = 1, subcarrier_offset = 0 when s = 3, and subcarrier_offset = 3 when s = 5. Where s = [OFDM symbol index] mod 6 and OFDM symbol index is {0,1,2, ...}.

In the upper left of FIG. 18, the first picture is subcarrier_offset = 0 when s = 0, subcarrier_offset = 2 when s = 2, and subcarrier_offset = 0 when s = 4. The second figure in the upper left of FIG. 18 is subcarrier_offset = 1 when s = 0, subcarrier_offset = 3 when s = 2, and subcarrier_offset = 1 when s = 4. The third figure in the upper left of FIG. 18 is subcarrier_offset = 0 when s = 1, subcarrier_offset = 2 when s = 3, and subcarrier_offset = 0 when s = 5. The fourth figure in the upper left of FIG. 18 is subcarrier_offset = 1 when s = 1, subcarrier_offset = 3 when s = 3, and subcarrier_offset = 1 when s = 5.

In the lower left of FIG. 18, the first picture is subcarrier_offset = 3 when s = 0, subcarrier_offset = 1 when s = 2, and subcarrier_offset = 3 when s = 4. In the lower left of FIG. 18, the second figure shows subcarrier_offset = 2 when s = 0, subcarrier_offset = 0 when s = 2, and subcarrier_offset = 2 when s = 4. In the lower left of FIG. 18, the third figure shows subcarrier_offset = 3 when s = 1, subcarrier_offset = 1 when s = 3, and subcarrier_offset = 3 when s = 5. In the lower left of FIG. 18, the fourth figure shows subcarrier_offset = 2 when s = 1, subcarrier_offset = 0 when s = 3, and subcarrier_offset = 2 when s = 5. Where s = [OFDM symbol index] mod 6 and OFDM symbol index is {0,1,2, ...}.

The first picture on the left of FIG. 19 is subcarrier_offset = 1 when s = 0, subcarrier_offset = 2 when s = 2, and subcarrier_offset = 1 when s = 4. The second figure on the left side of FIG. 19 shows subcarrier_offset = 2 when s = 0, subcarrier_offset = 1 when s = 2, and subcarrier_offset = 2 when s = 4. The third figure on the left of FIG. 19 is subcarrier_offset = 1 when s = 1, subcarrier_offset = 2 when s = 3, and subcarrier_offset = 1 when s = 5. The fourth figure from the left of FIG. 19 is subcarrier_offset = 2 when s = 1, subcarrier_offset = 1 when s = 3, and subcarrier_offset = 2 when s = 5. Where s = [OFDM symbol index] mod 6 and OFDM symbol index is {0,1,2, ...}.

17 to 19 illustrate a case in which a base unit is allocated in units of 4 subcarriers and 6 OFDM symbols, and in which 3 pilot subcarriers are arranged at different positions on a time axis in the base unit, the pilot overhead is 12.5%. do.

17 to 19, when using three pilot subcarriers per base unit, it is possible to reduce the pilot overhead to 3/8 compared to the conventional IEEE 802.16e uplink PUSC structure. In addition, it is preferable to arrange the data subcarriers of the base unit in a robust channel estimation for the low speed user case and the high speed user case with three pilot subcarriers per base unit. Do. In other words, it is appropriate to distribute pilots in symbols 1, 3, 5 or symbols 2, 4, 6 positions.

In addition, in order to ensure robust channel estimation performance in consideration of frequency selectivity, it is preferable to allocate pilots to first and fourth positions in the frequency domain as shown in FIG. 17.

On the other hand, when considering the case that the continuous resource on the frequency axis and time axis, that is, the base unit is continuously allocated to the frequency domain or continuously allocated during a certain OFDM symbol, that is, the base unit is continuously allocated When the channel estimation is performed using all pilots of P, any structures of FIGS. 17 to 19 may be considered.

20 to 25 illustrate an example in which six pilots are arranged in a base unit according to another embodiment of the present invention.

20 to 25 may be represented by Equation 2.

The first figure on the left of FIG. 20 shows subcarrier_offset = 0 when s = 0, subcarrier_offset = 3 when s = 2, subcarrier_offset = 0 when s = 4, and subcarrier_offset = 3 and s = 8 days when s = 6. When subcarrier_offset = 0 and s = 10, subcarrier_offset = 3. The second figure from the left of FIG. 20 shows subcarrier_offset = 3 when s = 0, subcarrier_offset = 0 when s = 2, subcarrier_offset = 3 when s = 4, and subcarrier_offset = 0 and s = 8 when s = 6. When subcarrier_offset = 3 and s = 10, subcarrier_offset = 0. Where s = [OFDM symbol index] mod 12 and the OFDM symbol index is {0,1,2, ...}.

In the upper left of FIG. 21, the first figure shows subcarrier_offset = 0 when s = 0, subcarrier_offset = 3 when s = 2, subcarrier_offset = 0 when s = 5, subcarrier_offset = 3 when s = 6, and s = 9. When subcarrier_offset = 0 and s = 11, subcarrier_offset = 3. In the upper left of FIG. 21, the second figure shows subcarrier_offset = 3 when s = 0, subcarrier_offset = 0 when s = 2, subcarrier_offset = 3 when s = 5, and subcarrier_offset = 0 and s = 9 when s = 6. When subcarrier_offset = 3 and when s = 11, subcarrier_offset = 0.

In the lower left of FIG. 21, the first figure shows subcarrier_offset = 0 when s = 1, subcarrier_offset = 3 when s = 3, subcarrier_offset = 0 when s = 5, subcarrier_offset = 3 when s = 7, and s = 9. When subcarrier_offset = 0 and s = 11, subcarrier_offset = 3. In the lower left of FIG. 21, the second figure shows subcarrier_offset = 3 when s = 1, subcarrier_offset = 0 when s = 3, subcarrier_offset = 3 when s = 5, and subcarrier_offset = 0 and s = 9 when s = 7. When subcarrier_offset = 3 and when s = 11, subcarrier_offset = 0. Where s = [OFDM symbol index] mod 12 and the OFDM symbol index is {0,1,2, ...}.

The first figure on the left side of FIG. 22 is subcarrier_offset = 0 when s = 1, subcarrier_offset = 3 when s = 2, subcarrier_offset = 0 when s = 5, subcarrier_offset = 3 and s = 9 days when s = 6. When subcarrier_offset = 0 and s = 10, subcarrier_offset = 3. The second figure from the left of FIG. 22 is subcarrier_offset = 3 when s = 1, subcarrier_offset = 0 when s = 2, subcarrier_offset = 0 when s = 5, and subcarrier_offset = 0 and s = 9 when s = 6. When subcarrier_offset = 3 and s = 10, subcarrier_offset = 0. Where s = [OFDM symbol index] mod 12 and the OFDM symbol index is {0,1,2, ...}.

The first figure on the left of FIG. 23 shows subcarrier_offset = 0 when s = 0, subcarrier_offset = 3 when s = 2, subcarrier_offset = 1 when s = 4, and subcarrier_offset = 2 and s = 9 days when s = 7. When subcarrier_offset = 0 and s = 11, subcarrier_offset = 3. The second figure from the left of FIG. 23 shows subcarrier_offset = 3 when s = 0, subcarrier_offset = 0 when s = 2, subcarrier_offset = 2 when s = 4, and subcarrier_offset = 1 and s = 9 when s = 7. When subcarrier_offset = 3 and s = 11, subcarrier_offset = 0. Where s = [OFDM symbol index] mod 12 and the OFDM symbol index is {0,1,2, ...}.

The first figure on the left side of FIG. 24 is subcarrier_offset = 0 when s = 0, subcarrier_offset = 3 when s = 2, subcarrier_offset = 2 when s = 4, subcarrier_offset = 1 when s = 7, and s = 9 days When subcarrier_offset = 0 and s = 11, subcarrier_offset = 3. The second figure from the left of FIG. 24 shows subcarrier_offset = 3 when s = 0, subcarrier_offset = 0 when s = 2, subcarrier_offset = 1 when s = 4, and subcarrier_offset = 2 and s = 9 days when s = 7. When subcarrier_offset = 3 and s = 11, subcarrier_offset = 0. Where s = [OFDM symbol index] mod 12 and the OFDM symbol index is {0,1,2, ...}.

In the upper left of FIG. 25, the first figure shows subcarrier_offset = 1 when s = 0, subcarrier_offset = 3 when s = 2, subcarrier_offset = 0 when s = 4, subcarrier_offset = 0 when s = 7, and s = 9 When subcarrier_offset = 0 and s = 11, subcarrier_offset = 2. The second figure in the upper left of FIG. 25 is subcarrier_offset = 2 when s = 0, subcarrier_offset = 0 when s = 2, subcarrier_offset = 3 when s = 4, subcarrier_offset = 0 and s = 9 when s = 7. When subcarrier_offset = 3 and when s = 11, subcarrier_offset = 1.

In the lower left of Fig. 25, the first figure shows subcarrier_offset = 1 when s = 0, subcarrier_offset = 3 when s = 3, subcarrier_offset = 0 when s = 4, subcarrier_offset = 3 and s = 8 when s = 7. When subcarrier_offset = 0 and s = 11, subcarrier_offset = 2. In the lower left of FIG. 25, the second figure shows subcarrier_offset = 2 when s = 0, subcarrier_offset = 0 when s = 3, subcarrier_offset = 3 when s = 4, and subcarrier_offset = 0 and s = 8 when s = 7. When subcarrier_offset = 3 and when s = 11, subcarrier_offset = 1.

20 to 25 illustrate a case in which a basic unit is allocated in units of 4 subcarriers and 12 OFDM symbols, and pilot overhead is 12.5%.

20 to 22 show a structure in which six pilot subcarriers are disposed at frequency positions at both ends of the base unit on the frequency axis. 23 to 25 show a structure in which six pilot subcarriers are arranged to occupy all positions on the frequency axis of the base unit.

26A to 30 illustrate an example in which four pilots are arranged in a base unit according to another embodiment of the present invention.

26A to 28C may be expressed by Equation 2.

26a shows subcarrier_offset = 0 when s = 1, subcarrier_offset = 3 when s = 3, subcarrier_offset = 0 when s = 5, and subcarrier_offset = 3 when s = 7. The lower figure of FIG. 26A shows subcarrier_offset = 3 when s = 1, subcarrier_offset = 0 when s = 3, subcarrier_offset = 3 when s = 5, and subcarrier_offset = 0 when s = 7.

26b shows subcarrier_offset = 1 when s = 1, subcarrier_offset = 3 when s = 3, subcarrier_offset = 0 when s = 5, and subcarrier_offset = 2 when s = 7. 26b shows subcarrier_offset = 2 when s = 1, subcarrier_offset = 0 when s = 3, subcarrier_offset = 3 when s = 5, and subcarrier_offset = 1 when s = 7.

27a shows subcarrier_offset = 0 when s = 0, subcarrier_offset = 3 when s = 3, subcarrier_offset = 0 when s = 5, and subcarrier_offset = 3 when s = 8. 27a shows subcarrier_offset = 3 when s = 0, subcarrier_offset = 0 when s = 3, subcarrier_offset = 3 when s = 5, and subcarrier_offset = 0 when s = 8.

The first picture in the upper left of FIG. 27B is subcarrier_offset = 1 when s = 0, subcarrier_offset = 3 when s = 3, subcarrier_offset = 0 when s = 5, and subcarrier_offset = 2 when s = 8. The second figure in the upper left of FIG. 27B is subcarrier_offset = 2 when s = 0, subcarrier_offset = 3 when s = 3, subcarrier_offset = 0 when s = 5, and subcarrier_offset = 1 when s = 8.

In the lower left of FIG. 27B, the first picture shows subcarrier_offset = 2 when s = 0, subcarrier_offset = 0 when s = 3, subcarrier_offset = 3 when s = 5, and subcarrier_offset = 1 when s = 8. In the lower left of FIG. 27B, the second figure shows subcarrier_offset = 1 when s = 0, subcarrier_offset = 0 when s = 3, subcarrier_offset = 3 when s = 5, and subcarrier_offset = 2 when s = 8.

The first picture on the left side of FIG. 28A shows subcarrier_offset = 2 when s = 1, subcarrier_offset = 1 when s = 3, subcarrier_offset = 2 when s = 5, and subcarrier_offset = 1 when s = 7. The second figure from the left of FIG. 28A shows subcarrier_offset = 1 when s = 1, subcarrier_offset = 1 when s = 3, subcarrier_offset = 1 when s = 5, and subcarrier_offset = 2 when s = 7.

FIG. 28B shows subcarrier_offset = 3 when s = 2, subcarrier_offset = 0 when s = 3, subcarrier_offset = 0 when s = 5, and subcarrier_offset = 0 when s = 6.

The first picture on the left of FIG. 28C is subcarrier_offset = 2 when s = 1, subcarrier_offset = 0 when s = 2, subcarrier_offset = 3 when s = 6, and subcarrier_offset = 1 when s = 7. The second figure from the left of FIG. 28C shows subcarrier_offset = 1 when s = 1, subcarrier_offset = 3 when s = 2, subcarrier_offset = 0 when s = 6, and subcarrier_offset = 2 when s = 7.

29 may be represented by Equation 1.

The first picture from the top of FIG. 29 is a case of assigning pilot only when s = 2, 6, and the second picture from the top of FIG. 29 is a case of assigning pilot only when s = 1, 7, and from the top of FIG. The third figure shows the case of assigning pilot only when s = 0, 8.

30 may be represented by Equation 3. In FIG. 30, all G values are two.

The left figure at the top of FIG. 30 shows subcarrier_offset = 0 when s = 2 and subcarrier_offset = 1 when s = 6. The upper right figure of FIG. 30 shows subcarrier_offset = 1 when s = 2 and subcarrier_offset = 0 when s = 6.

In the interruption of FIG. 30, the left figure shows subcarrier_offset = 0 when s = 1 and subcarrier_offset = 1 when s = 7. In the interruption of FIG. 30, the right figure shows subcarrier_offset = 1 when s = 1 and subcarrier_offset = 0 when s = 7.

The lower left figure of FIG. 30 shows subcarrier_offset = 1 when s = 0 and subcarrier_offset = 0 when s = 8. The lower right figure of FIG. 30 shows subcarrier_offset = 0 when s = 0 and subcarrier_offset = 1 when s = 8.

26A to 30 illustrate a case in which a basic unit is allocated in units of 4 subcarriers and 9 OFDM symbols, and the pilot overhead is 11.11%.

26A, 27A, 28B, and 29 show a structure in which four pilot subcarriers are arranged in pairs at the same position on the frequency axis in a base unit. 26B, 27B, 28C, and 30 illustrate a structure in which four pilot subcarriers are arranged at different positions of the frequency axis in the base unit. 27A and 27B show a structure suitable for a high speed user case, and FIGS. 27B, 28C and 30 show a structure suitable for a case where a delay spread is large.

More specifically, when four pilot subcarriers per base unit are used as shown in FIGS. 26A to 30, the pilot overhead can be reduced to 1/3 compared to the existing IEEE 802.16e uplink PUSC structure. In addition, in the position of using 4 pilot subcarriers per base unit for robust channel estimation of the base unit data subcarriers for the low speed user case and the high speed user case, the base unit is spaced at 2 OFDM symbol intervals around the center of the time axis. It is preferable to arrange. For example, as shown in Figs. 26A to 28A, it is appropriate to arrange pilots by distributing them to the second, fourth, sixth, and eighth symbol positions.

In order to guarantee robust channel estimation performance in consideration of frequency selectivity, as shown in FIGS. 26B, 27B, 28C, and 30, each of the first subcarrier position to the fourth subcarrier position can be allocated to allocate pilots to all bands of the frequency domain. It is desirable to allocate and allocate one pilot.

On the other hand, in the case where the base unit is continuously allocated to the frequency domain and the time axis, that is, the frequency domain, or the base unit is continuously allocated during a certain OFDM symbol, that is, the base unit is continuously allocated. In the case of performing channel estimation using all used pilots, the above-described structure or other structures not described above may also be applied.

31 and 32 illustrate an example in which two pilots are arranged in a base unit according to another embodiment of the present invention.

31 and 32 illustrate a case in which a basic unit is allocated in units of 4 subcarriers and 6 OFDM symbols, and the pilot overhead is 8.33%.

31 to 32 may be represented by Equation 2.

The first picture on the left of FIG. 31 is subcarrier_offset = 0 when s = 1 and subcarrier_offset = 3 when s = 4. The second figure on the left of FIG. 31 shows subcarrier_offset = 3 when s = 1 and subcarrier_offset = 0 when s = 4. The third figure on the left of FIG. 31 shows subcarrier_offset = 0 when s = 1 and subcarrier_offset = 2 when s = 4. The fourth figure from the left of FIG. 31 is subcarrier_offset = 2 when s = 1 and subcarrier_offset = 0 when s = 4. The fifth figure from the left of FIG. 31 is subcarrier_offset = 1 when s = 1, the subcarrier_offset = 3 when s = 4, and the sixth figure from the left of FIG. 31 is subcarrier_offset = 3 when s = 1 and s = When 4, subcarrier_offset = 1.

The first picture in the upper left of FIG. 32 is subcarrier_offset = 0 when s = 0 and subcarrier_offset = 3 when s = 3. The second picture in the upper left of FIG. 32 is subcarrier_offset = 3 when s = 0 and subcarrier_offset = 0 when s = 3. The third figure in the upper left of FIG. 32 is subcarrier_offset = 0 when s = 0 and subcarrier_offset = 2 when s = 3. The fourth figure in the upper left of FIG. 32 is subcarrier_offset = 2 when s = 0 and subcarrier_offset = 0 when s = 3. The fifth figure in the upper left of FIG. 32 is subcarrier_offset = 1 when s = 0 and subcarrier_offset = 3 when s = 3. The sixth figure in the upper left of FIG. 32 is subcarrier_offset = 3 when s = 0 and subcarrier_offset = 1 when s = 3.

The first picture on the left side of the middle of FIG. 32 is subcarrier_offset = 0 when s = 2 and subcarrier_offset = 3 when s = 5. The second figure from the left side of the middle of FIG. 32 is subcarrier_offset = 3 when s = 2 and subcarrier_offset = 0 when s = 5. The third figure from the left side of the middle of FIG. 32 is subcarrier_offset = 0 when s = 2 and subcarrier_offset = 2 when s = 5. The fourth figure from the left side of the middle of FIG. 32 is subcarrier_offset = 2 when s = 2 and subcarrier_offset = 0 when s = 5. The fifth figure from the left side of the middle of FIG. 32 is subcarrier_offset = 1 when s = 2 and subcarrier_offset = 3 when s = 5. The sixth figure from the left side of the middle of FIG. 32 is subcarrier_offset = 3 when s = 2 and subcarrier_offset = 1 when s = 5.

The first picture in the lower left of FIG. 32 is subcarrier_offset = 1 when s = 1 and subcarrier_offset = 2 when s = 4. The second picture in the lower left of FIG. 32 is subcarrier_offset = 2 when s = 1 and subcarrier_offset = 1 when s = 4.

Using two pilot subcarriers per base unit as shown in FIG. 31 and FIG. 32, the pilot overhead can be reduced to 1/4 compared to the conventional IEEE 802.16e uplink PUSC structure. In addition, in terms of robust channel estimation for the low speed user case and the high speed user case with one pilot subcarrier per base unit, as shown in FIG. It is appropriate to place the pilot at the position of the symbol and the fifth symbol.

In addition, in order to ensure robust channel estimation performance in consideration of frequency selectivity, it is preferable to allocate pilots to first and fourth positions in the frequency domain. Alternatively, pilots can be assigned to the first and third, second and fourth positions in the frequency domain for the same purpose.

On the other hand, when considering that the base unit is continuously allocated to the frequency axis and the time axis, that is, the base unit is continuously allocated to the frequency domain or continuously during a certain OFDM symbol, that is, the base unit is continuously allocated When channel estimation is performed using all pilots, the above-described structure or a structure for allocating pilots to other frequency positions and other OFDM symbol positions may be applied.

33 and 34 illustrate an example in which four pilots are arranged in a base unit according to another embodiment of the present invention.

33 and 34 illustrate a case in which a basic unit is allocated in units of 4 subcarriers and 12 OFDM symbols, and the pilot overhead is 8.33%.

33 and 34 may be represented by equation (2).

33 shows subcarrier_offset = 0 when s = 1, subcarrier_offset = 2 when s = 4, subcarrier_offset = 1 when s = 7, and subcarrier_offset = 3 when s = 10. 33 shows subcarrier_offset = 3 when s = 1, subcarrier_offset = 1 when s = 4, subcarrier_offset = 2 when s = 7, and subcarrier_offset = 0 when s = 10.

33 shows a subcarrier_offset = 0 when s = 0, subcarrier_offset = 2 when s = 3, subcarrier_offset = 1 when s = 6, and subcarrier_offset = 3 when s = 9. 33 shows subcarrier_offset = 3 when s = 0, subcarrier_offset = 1 when s = 3, subcarrier_offset = 2 when s = 6, and subcarrier_offset = 0 when s = 9.

The lower left diagram of FIG. 33 shows subcarrier_offset = 0 when s = 2, subcarrier_offset = 2 when s = 5, subcarrier_offset = 1 when s = 8, and subcarrier_offset = 3 when s = 11. 33 shows a subcarrier_offset = 3 when s = 2, subcarrier_offset = 1 when s = 5, subcarrier_offset = 2 when s = 8, and subcarrier_offset = 0 when s = 11.

34 shows subcarrier_offset = 0 when s = 0, subcarrier_offset = 1 when s = 3, subcarrier_offset = 2 when s = 6, and subcarrier_offset = 3 when s = 9. 34 shows subcarrier_offset = 3 when s = 0, subcarrier_offset = 2 when s = 3, subcarrier_offset = 1 when s = 6, and subcarrier_offset = 0 when s = 9.

34 shows subcarrier_offset = 0 when s = 1, subcarrier_offset = 1 when s = 4, subcarrier_offset = 2 when s = 7, and subcarrier_offset = 3 when s = 10. 34 shows subcarrier_offset = 3 when s = 1, subcarrier_offset = 2 when s = 4, subcarrier_offset = 1 when s = 7, and subcarrier_offset = 0 when s = 10.

34 shows subcarrier_offset = 0 when s = 2, subcarrier_offset = 1 when s = 5, subcarrier_offset = 2 when s = 8, and subcarrier_offset = 3 when s = 11. The lower right figure of FIG. 34 shows subcarrier_offset = 3 when s = 2, subcarrier_offset = 2 when s = 5, subcarrier_offset = 1 when s = 8, and subcarrier_offset = 0 when s = 11.

33 and 34 illustrate a structure in which four pilot subcarriers are arranged at different positions on a frequency axis and a time axis in a base unit. 33 and 34 are structures capable of maintaining a pilot time interval even when a basic unit is allocated continuously on the time axis.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and variations may be made therefrom. And, such modifications should be considered to be within the technical protection scope of the present invention. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

The present invention relates to a basic unit and a pilot structure capable of lowering pilot overhead in uplink and ensuring excellent channel estimation. The present invention can improve performance of a system by reducing pilot overhead of an OFDM system. It is possible to ensure the performance of channel estimation by maintaining the interval at a constant interval, it can be applied to devices such as base stations, terminals and the like that is compatible with IEEE 802.16m.

1 shows a tile and pilot structure of a conventional IEEE 802.16e.

2 to 6 show an example in which two pilots are arranged in the base unit.

7 to 10B illustrate an example in which four pilots are arranged in a base unit according to an embodiment of the present invention when the base unit is allocated in units of 4 subcarriers and 6 OFDM symbols.

11 to 15 illustrate an example in which six pilots are arranged in a base unit according to another embodiment of the present invention when the base unit is allocated in units of 4 subcarriers and 9 OFDM symbols.

FIG. 16 illustrates an example in which eight pilots are arranged in a base unit according to another embodiment of the present invention when the base unit is allocated in units of 4 subcarriers and 12 OFDM symbols.

17 to 19 illustrate an example in which three pilots are arranged in a base unit according to another embodiment of the present invention when the base unit is allocated in units of 4 subcarriers and 6 OFDM symbols.

20 to 25 illustrate an example in which 6 pilots are arranged in a base unit according to another embodiment of the present invention when the base unit is allocated in units of 4 subcarriers and 12 OFDM symbols.

26A to 30 illustrate an example in which four pilots are arranged in a base unit according to another embodiment of the present invention when the base unit is allocated in units of 4 subcarriers and 9 OFDM symbols.

31 and 32 illustrate an example in which two pilots are arranged in a base unit according to another embodiment of the present invention when the base unit is allocated in units of 4 subcarriers and 6 OFDM symbols.

33 and 34 illustrate an example in which four pilots are arranged in a base unit according to another embodiment of the present invention when the base unit is allocated in units of 4 subcarriers and 12 OFDM symbols.

Claims (15)

In the method for transmitting a pilot subcarrier through a continuous base unit of the uplink, Placing four pilot subcarriers at different locations on a frequency axis in the base unit; Placing data subcarriers at the remaining position of the base unit; And Transmitting the base unit to a receiving end; And the base unit is composed of four subcarrier units on the frequency axis and six or more OFDM symbol units on the time axis. The method of claim 1, Deploying the pilot subcarrier, And placing the four pilot subcarriers in pairs at the same position on the time axis. The method of claim 1, Deploying the pilot subcarrier, And disposing at least two pilot subcarriers of the four pilot subcarriers at positions of the edges of the base unit. In the method for transmitting a pilot subcarrier through a continuous base unit of the uplink, Placing four pilot subcarriers in pairs at the same position on the frequency axis in the base unit; Placing data subcarriers at the remaining position of the base unit; And Transmitting the base unit to a receiving end; And the base unit is composed of four subcarrier units on the frequency axis and six or more OFDM symbol units on the time axis. The method of claim 4, wherein Deploying the pilot subcarrier, And disposing the four pilot subcarriers at different positions on a time axis. The method of claim 4, wherein Deploying the pilot subcarrier, And arranging the four pilot subcarriers in pairs at the same position on the time axis. The method of claim 4, wherein Deploying the pilot subcarrier, And disposing at least two pilot subcarriers of the four pilot subcarriers at positions of the edges of the base unit. The method of claim 4, wherein Deploying the pilot subcarrier, And disposing the four pilot subcarriers at positions excluding edges of the base unit. In the method for transmitting a pilot subcarrier through a continuous base unit of the uplink, Placing three pilot subcarriers at different locations on the time axis in the base unit; Placing data subcarriers at the remaining position of the base unit; And Transmitting the base unit to a receiving end; And the base unit is composed of four subcarrier units on the frequency axis and six or more OFDM symbol units on the time axis. The method of claim 9, Deploying the pilot subcarrier, And arranging a pair of pilot subcarriers of the three pilot subcarriers at the same position on the frequency axis and disposing the remaining pilot subcarriers at different positions on the frequency axis with the pair of pilot subcarriers. Transmission method. The method of claim 10, Deploying the pilot subcarrier, And disposing the pair of pilot subcarriers and the remaining pilot subcarriers at positions spaced at a maximum distance from a frequency axis. In the method for transmitting a pilot subcarrier through a continuous base unit of the uplink, Placing six pilot subcarriers to occupy all positions on the frequency axis of the base unit; Placing data subcarriers at the remaining position of the base unit; And Transmitting the base unit to a receiving end; And the base unit is composed of four subcarrier units on the frequency axis and nine or more OFDM symbol units on the time axis. In the method for transmitting a pilot subcarrier through a continuous base unit of the uplink, Placing six pilot subcarriers at both ends of the base unit on a frequency axis; Placing data subcarriers at the remaining position of the base unit; And Transmitting the base unit to a receiving end; And the base unit is composed of four subcarrier units on the frequency axis and nine or more OFDM symbol units on the time axis. In the method for transmitting a pilot subcarrier through a continuous base unit of the uplink, Placing two pilot subcarriers at different positions on a frequency axis and a time axis in the base unit; Placing data subcarriers at the remaining position of the base unit; And Transmitting the base unit to a receiving end; And the base unit is composed of four subcarrier units on the frequency axis and six OFDM symbol units on the time axis. In the method for transmitting a pilot subcarrier through a continuous base unit of the uplink, Placing four pilot subcarriers at different positions on a frequency axis and a time axis in the base unit; Placing data subcarriers at the remaining position of the base unit; And Transmitting the base unit to a receiving end; And wherein the base unit is composed of four subcarrier units on the frequency axis and 12 OFDM symbol units on the time axis.

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