RU2446602C1 - Method for transmission via uplink in ofdm(a)-system - Google Patents

Abstract

FIELD: information technology.

SUBSTANCE: method for subcarrier transmission includes placement of 4 RE for pilot signals in various positions of frequency axis in basic unit, in which case basic unit comprises 4 subcarriers on frequency axis and 6 OFDM(A)-symbols on time axis, RE placement for data in remaining positions of basic unit, and basic unit transmission to receiving end.

EFFECT: lower amount of service information during transmission of pilot signals.

15 cl, 39 dwg, 53 tbl

Description

State of the art

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.

Description of the Related Art

The current IEEE 802.16e system uses a mosaic pattern of pilot signals, as shown in FIG. 1, as a structure based on partial use of a subchannel (PUSC) in an uplink. One transmit antenna is considered in the structure of FIG. 1. This structure of the base units of the PUSC in the uplink has an amount of overhead when transmitting pilot signals at 33.33%. In FIG. 1, pilot data subcarriers and subcarriers are referred to as resource elements (REs) allocated to pilot signals and data, respectively. Each RE represents a time-frequency resource defined by one OFDM (A) symbol and one subcarrier. In the following description, the terms “pilot subcarrier” and “data subcarrier” can be used interchangeably with the terms “RE for pilot” and “RE for data”, respectively.

Since only one transmit antenna is considered in the uplink tile pattern used in the current IEEE 802.16e system, the structure of the PUSC base units in the uplink has an overhead amount of 33.33% pilot transmission. Thus, the ratio of the amount of overhead when transmitting pilot signals to data is significant. Such an amount of overhead when transmitting pilot signals reduces the throughput of the communication line, which leads to a decrease in system performance. When an extended base unit is used, as in IEEE 802.16m, one task is to reduce the amount of overhead when transmitting pilot signals.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a method for uplink transmission in an OFDM (A) system, which substantially eliminates one or more problems due to limitations and disadvantages of the prior art.

An object of the present invention is to provide an uplink transmission method that can reduce the amount of overhead when transmitting pilot signals and guarantee channel estimation performance even when the size of the base unit for the uplink is extended on the time axis.

Another objective of the present invention is to provide an uplink transmission method that guarantees backward compatibility for an IEEE 802.16e system.

Additional advantages, objects, and features of the invention are set forth in part in the following description and in part should be apparent to those skilled in the art upon examination of the following, or may be learned from the practice of the invention. The objectives and other advantages of the invention can be realized and achieved through the structure, in particular, disclosed in the written description and claims, as well as in the accompanying drawings.

In the existing IEEE 802.16e system, the uplink PUSC tile contains four adjacent subcarriers into three adjacent OFDM (A) characters. The existing IEEE 802.16e system applies permutation to distribute uplink PUSC tiles within the corresponding frequency band in the mapping of uplink PUSC tiles into 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 scattered within the corresponding frequency band.

Such a permutation method can be easily modified for an expanded mosaic structure by configuring multiple of three OFDM (A) symbols, for example six, nine, or twelve OFDM (A) symbols, which are adjacent in the time domain and are within the same physical frequency bands, so as to have the same logical index of the mosaic fragment. Essentially, the permutation method of an existing IEEE 802.16e system can be extended to distribute radio resources in units of multiple of three OFDM (A) characters. Therefore, it is preferable that the IEEE 802.16m system under consideration forms an uplink mosaic fragment with four subcarriers of a multiple of three OFDM (A) symbols if the existing IEEE 802.16e system is supported via frequency division multiplexing (FDM).

In this IEEE 802.16m system, the basic frame structure includes a 20 ms superframe supporting 5 MHz, 8.75 MHz, 20 MHz, or 10 MHz bandwidth. Each superframe is divided into four 5 ms radio frames of the same size and begins with the superframe header (SFH). Each 5 ms radio frame additionally consists of eight subframes. A subframe shall be assigned for DL or UL transmission. There are three types of subframes depending on the size of the cyclic prefix, i.e. subframe consisting of five, six or seven OFDM (A) characters. A subframe carries smaller units of resources with different types / sizes. The basic frame structure applies to FDD and TDD duplex schemes.

In one aspect of the present invention, there is provided a method for transmitting a base unit in an uplink, the method comprising: placing 4 REs for pilot signals at different positions of the frequency axis in a base unit, when the base unit contains 4 subcarriers of 6 or more OFDM (A) - characters placing the RE for the data in the remaining positions of the base unit and transferring the base unit to the receiving end. The receiving end includes a base station (BS).

In the step of placing 4 REs for the pilot signals, 4 REs for the pilot signals can be paired so that two REs for the pilot signals of each pair are placed at the same position on the time axis.

At the stage of placing 4 REs for the pilot signals, two or more REs for the pilot signals from 4 REs for the pilot signals can be located at the boundary positions of the base unit.

In another aspect of the present invention, there is provided a method for transmitting a base unit in an uplink, the method comprising: placing 4 REs for pilot signals in pairs such that two REs for the pilot signals of each pair are placed at the same frequency axis position in the base unit when the base unit contains 4 subcarriers of 6 or more OFDM (A) -characters; placing the RE for the data in the remaining positions of the base unit and transferring the base unit to the receiving end.

In the step of placing 4 REs for the pilot signals, 4 REs for the pilot signals can be placed at different positions on the time axis.

In the step of placing 4 REs for pilot signals, 4 REs for pilot signals can be placed in pairs so that two REs for the pilot signals of each pair are placed at the same position on the time axis.

At the stage of placing 4 REs for pilot signals, two or more REs for pilot signals from 4 REs for pilot signals can be located at the boundary positions of the base unit.

At the stage of placing 4 REs for the pilot signals, two or more REs for the pilot signals from 4 REs for the pilot signals can be placed at non-boundary positions of the base unit.

In another aspect of the present invention, there is provided a method of transmitting an uplink base unit, the method comprising: placing 3 REs for pilot signals at different positions on the time axis in the base unit, when the base unit accommodates 4 subcarriers of 6 or more OFDM (A) -characters; placing the RE for the data in the remaining positions of the base unit and transmitting the base unit to the receiving end.

In the placement step of 3 REs for pilot signals, a pair of REs for pilot signals from 3 REs for pilot signals can be placed at the same position on the frequency axis and the remaining REs for pilot signals can be placed at a position different from the position of the RE pair for pilot signals on the frequency axis.

At the placement stage 3 RE for the pilot signals, the pair of REs for the pilot signals and the remaining REs for the pilot signals can be placed at the most distant positions on the frequency axis.

In another aspect of the present invention, there is provided a method for transmitting a base unit in an uplink, the method comprising: placing 6 REs for pilot signals at all positions on the frequency axis of the base unit, when the base unit contains 4 subcarriers of 9 or more OFDM (A) - characters placing the RE for the data in the remaining positions of the base unit and transferring the base unit to the receiving end.

In another aspect of the present invention, there is provided a method for transmitting a base unit in an uplink, the method comprising: placing 6 REs for pilot signals at both ends of the frequency axis of the base unit, when the base unit accommodates 4 subcarriers of 9 or more OFDM (A) symbols ; placing the RE for the data in the remaining positions of the base unit and transferring the base unit to the receiving end.

In another aspect of the present invention, there is provided a method for transmitting a base unit in an uplink, the method comprising: placing 2 REs for pilot signals at different positions on a frequency axis and a time axis in a base unit when the base unit accommodates 4 subcarriers in 6 OFDM (A ) -characters; placing the RE for the data in the remaining positions of the base unit and transferring the base unit to the receiving end.

In another aspect of the present invention, there is provided a method for transmitting an uplink base unit, the method comprising: placing 4 REs for pilot signals at different positions on the frequency axis and the time axis in the base unit, when the base unit accommodates 4 subcarriers in 12 OFDM (A ) -characters; placing the RE for the data in the remaining positions of the base unit and transferring the base unit to the receiving end.

In another aspect of the present invention, there is provided a method for transmitting an uplink base unit by a mobile station (MS) in an orthogonal frequency division multiple access (OFDMA) wireless communication system, the method comprising: generating a base unit of 4 subcarriers by 6 in size OFDMA symbols, the base unit contains a plurality of resource elements (RE) for pilot signals and data; configuring the REs for the pilot signals for one antenna in the base unit at intervals of 3 subcarriers on the frequency axis and at intervals of 1 or 4 OFDMA symbols on the time axis; and transmitting the base unit in the uplink, wherein the RE is a time-frequency resource specified by one OFDMA symbol and one subcarrier, wherein the REs for the pilot signals and data are placed in the base unit, as in table 1 of patterns, expressed as follows way:

Table 1 Patterns s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 P - - - P - SC = 1 - - - - - - SC = 2 - - - - - - SC = 3 - P - - - P where "P" indicates RE for pilot signals,
"-" indicates RE for data,
"s" indicates the index of the OFDMA symbol, and
"SC" indicates the subcarrier index.

Alternatively, there is provided a method for uplink transmission of a subframe containing a plurality of base units by a mobile station (MS) in an orthogonal frequency division multiple access (OFDMA) wireless communication system, the method comprising: generating each base unit whose size is 4 subcarriers of 6 OFDMA symbols, each base unit contains a plurality of resource elements (RE) for pilot signals and data; configuring REs for pilot signals for one antenna in each base unit with 3 subcarrier intervals on the frequency axis and 1 or 4 OFDMA symbol intervals on the time axis; and transmitting a subframe in the uplink, wherein RE is a time-frequency resource specified by one OFDMA symbol and one subcarrier, wherein REs for the pilot signals and data are located in each base unit, as in table 1 of patterns, expressed as follows way:

Table 1 Patterns s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 P - - - P - SC = 1 - - - - - - SC = 2 - - - - - - SC = 3 - P - - - P where "P" indicates RE for pilot signals,
"-" indicates RE for data,
"s" indicates the index of the OFDMA symbol, and
"SC" indicates the subcarrier index.

The subframe accommodates 6 OFDM (A) symbols. If the subframe accommodates 5 or 7 OFDM (A) -characters depending on the size of the cyclic prefix, the above pattern table 1 can be modified accordingly by deleting or adding one OFDM (A) -character so that the modified pattern table by - still supports the feasible channel rating capability.

The base unit may be a mosaic fragment in the uplink. In particular, the base unit may be a mosaic fragment based on the partial use of the subchannel (PUSC) in the uplink. The base unit may be a mosaic fragment based on the partial use of the subchannel (PUSC) in the uplink according to IEEE 802.16m. The base unit may be a distributed resource unit (DRU) for 16m PUSC. A certain number of base units can form a larger unit of resources. A certain number of base units includes six base units. A larger unit of resources includes a localized unit of resources or a distributed unit of resources. In this case, the basic units that form each larger unit of resources may be adjacent in the frequency domain. Alternatively, the base units forming each larger unit of resources may be allocated in the frequency domain.

The RE locations for the pilot signals may cyclically shift in the frequency domain or in the time domain.

REs for pilot signals may be power amplified with RE powers for data in the same OFDMA symbol.

The method may further comprise mapping the pilot symbols and data symbols to respective REs for the pilot signals and data, respectively. Pilot and data symbols may be of the type of complex value representing amplitude and phase. For example, a data symbol may include a complex value representing the amplitude and phase of the modulated data.

REs for pilots may be used for dedicated pilots.

In another aspect of the present invention, there is provided a method of transmitting an uplink base unit by a mobile station (MS) in an orthogonal frequency division multiple access (OFDMA) wireless communication system, the method comprising: generating a base unit of 4 subcarriers by 6 in size OFDMA symbols, the base unit contains a plurality of resource elements (RE) for pilot signals and data; configuring REs for pilots for multiple antennas in a base unit with 3 subcarrier intervals on the frequency axis and 5 OFDMA symbol intervals on the time axis; and transmitting the base unit in the uplink, wherein the RE is a time-frequency resource specified by one OFDMA symbol and one subcarrier, wherein the REs for the pilot signals and data are placed in the base unit, as in table 2 of patterns, expressed as follows way:

Table 2 Patterns s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 P0 - - - - P1 SC = 1 - - - - - - SC = 2 - - - - - - SC = 3 P1 - - - - P0 where "P0" and "P1" indicate the corresponding REs for the pilot signals for antenna ports 0 and 1,
"-" indicates RE for data,
"s" indicates the index of the OFDMA symbol, and
"SC" indicates the subcarrier index.

Alternatively, there is provided a method for uplink transmission of a subframe containing a plurality of base units by a mobile station (MS) in an orthogonal frequency division multiple access (OFDMA) wireless communication system, the method comprising: generating each base unit whose size is 4 subcarriers of 6 OFDMA symbols, each base unit contains a plurality of resource elements (RE) for pilot signals and data; configuring REs for pilots for multiple antennas in each base unit with 3 subcarrier intervals on the frequency axis and 5 OFDMA symbol intervals on the time axis; and transmission of a subframe in the uplink, wherein RE is a time-frequency resource specified by one OFDMA symbol and one subcarrier, wherein REs for the pilot signals and data are located in each base unit, as in table 2 of patterns, expressed as follows way:

Table 2 Patterns s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 P0 - - - - P1 SC = 1 - - - - - - SC = 2 - - - - - - SC = 3 P1 - - - - P0 where "P0" and "P1" indicate the corresponding REs for the pilot signals for antenna ports 0 and 1,
"-" indicates RE for data,
"s" indicates the index of the OFDMA symbol, and
"SC" indicates the subcarrier index.

The subframe accommodates 6 OFDM (A) symbols. If the subframe accommodates 5 or 7 OFDM (A) -characters depending on the size of the cyclic prefix, the above pattern table 1 can be modified accordingly by deleting or adding one OFDM (A) -character so that the modified pattern table by - still supports the feasible channel rating capability.

The base unit may be a mosaic fragment in the uplink. In particular, the base unit may be a mosaic fragment based on the partial use of the subchannel (PUSC) in the uplink. The base unit may be a mosaic fragment based on the partial use of the subchannel (PUSC) in the uplink according to IEEE 802.16m. The base unit may be a distributed resource unit (DRU) for 16m PUSC. A certain number of base units can form a larger unit of resources. A certain number of base units includes six base units. A larger unit of resources includes a localized unit of resources or a distributed unit of resources. In this case, the basic units that form each larger unit of resources may be adjacent in the frequency domain. Alternatively, the base units forming each larger unit of resources may be allocated in the frequency domain.

Antenna port 0 and antenna port 1 can be replaced by each other. the RE locations for the pilot signals may cyclically shift in the frequency domain or in the time domain.

REs for pilot signals may be power amplified with RE powers for data in the same OFDMA symbol.

The method may further comprise mapping the pilot symbols and data symbols to respective REs for the pilot signals and data, respectively. Pilot and data symbols may be of a conjugate value type representing amplitude and phase. For example, the data symbol may include a conjugate value representing the amplitude and phase of the modulated data.

REs for pilots may be used for dedicated pilots.

The transmission diversity scheme or spatial multiplexing (SM) can be independently applied to each base unit. The transmit diversity scheme includes a space time block code (STBC), a space frequency block code (SFBC), cyclic delay diversity (CDD), or any combination of the above.

The execution order of the steps illustrated in the above various aspects of the present invention depends on the implementation objectives. Therefore, the steps of the present invention can be performed in a different order depending on the product, unless the order is specifically mentioned.

According to embodiments of the present invention, it is possible to reduce the amount of overhead when transmitting the pilot signals of the OFDM (A) system, even when each base unit for the uplink is extended on the time axis.

In addition, since the time interval and the frequency interval RE for the pilots in the base unit are kept universal, or the REs for the pilots are allocated to simplify channel estimation, it is possible to guarantee channel estimation performance and improve system performance.

Additionally, backward compatibility with the existing PUSC structure in the IEEE 802.16e uplink can be guaranteed.

It should be understood that the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide an additional explanation of the invention according to the claims.

Brief Description of the Drawings

The accompanying drawings, which are included in order to provide an additional understanding of the invention, are included in the application materials and form 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 traditional mosaic pattern of IEEE 802.16e pilot signals.

FIG. 2A illustrates an example in which pilot signals in 1Tx or 1 stream are allocated when each base unit includes 4 subcarriers × 3 OFDM (A) symbol according to an embodiment of the present invention.

FIG. 2B and 2C illustrate an example in which REs for pilots in 2Tx or 2 streams and in 4Tx or 4 streams are allocated when the base unit size is expanded to 4 subcarriers × 6 OFDM (A) symbols according to another embodiment of the present invention.

FIG. 3A illustrates an example in which pilot signals in 1Tx or 1 stream are allocated when each base unit includes 4 subcarriers × 3 of an OFDM (A) symbol according to another embodiment of the present invention.

FIG. 3B and 3C illustrate an example in which pilots in 2Tx or 2 streams and 4Tx or 4 streams are allocated when the base unit size is expanded to 4 subcarriers × 6 OFDM (A) symbols according to another embodiment of the present invention.

FIG. 4A illustrates an example in which pilot signals in 1Tx or 1 stream are allocated when each base unit includes 4 subcarriers × 3 of an OFDM (A) symbol according to another embodiment of the present invention.

FIG. 4B and 4C illustrate an example in which pilots in 2Tx or 2 streams and in 4Tx or 4 streams are allocated when the base unit size is expanded to 4 subcarriers × 6 OFDM (A) symbols according to another embodiment of the present invention.

FIG. 5A-5C illustrate an example in which pilot signals in 1Tx or 1 stream, in 2Tx or 2 streams, and in 4Tx or 4 streams are allocated when each base unit includes 4 subcarriers × 6 OFDM (A) symbols according to another embodiment of the present invention.

FIG. 6A-6C illustrate an example in which pilot signals in 1Tx or 1 stream, in 2Tx or 2 streams, and in 4Tx or 4 streams are allocated when each base unit includes 4 subcarriers × 6 OFDM (A) symbols according to another embodiment of the present invention.

FIG. 7A-7C illustrate an example in which pilot signals in 1Tx or 1 stream, in 2Tx or 2 streams, and in 4Tx or 4 streams are allocated when each base unit includes 4 subcarriers × 6 OFDM (A) symbols according to another embodiment of the present invention.

FIG. 8A-8C illustrate an example in which pilot signals in 1Tx or 1 stream, in 2Tx or 2 streams, and in 4Tx or 4 streams are allocated when each base unit includes 4 subcarriers × 6 OFDM (A) symbols according to another embodiment of the present invention.

FIG. 9A-9C illustrate an example in which pilot signals in 1Tx or 1 stream, in 2Tx or 2 flows, and in 4Tx or 4 streams are allocated when each base unit includes 4 subcarriers × 6 OFDM (A) symbols according to an embodiment of the present inventions.

FIG. 10-13 illustrate an example in which pilot signals in 1Tx or 1 stream are allocated when each base unit includes 4 subcarriers × 9 OFDM (A) symbols according to another embodiment of the present invention.

FIG. 14A-14C illustrate simulation results for channel estimation in the case of transmission in a single stream.

FIG. 15A-15C illustrate simulation results for channel estimation in the case of transmission in two streams.

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 may 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

The following is a detailed description of preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals are used in the drawings to refer to the same or similar elements.

Embodiments of the present invention provide a base unit and pilot structure that allows for reduced overhead when transmitting uplink pilots in an OFDM (A) system and also ensures high channel estimation performance. In embodiments of the present invention, pilot REs are allocated on a time axis in each base unit based on coherent time to provide a channel estimate that is reliable for cases of low speed and high speed in the time domain in the base unit. In addition, REs for the pilot signals are allocated on the frequency axis in each base unit, taking into account the coherent bandwidth, in order to estimate the channel, which is reliable for various delay spreads in the frequency domain. Embodiments of the present invention also provide a base unit and pilot structure that can improve channel estimation performance using consecutive base unit pilot signals that are allocated on a time-frequency axis.

FIG. 2A illustrates an example in which pilot signals in 1Tx or 1 stream are allocated when each base unit includes 4 subcarriers × 3 of an OFDM (A) symbol according to an embodiment of the present invention. In each 4 × 3 base unit, two REs for pilot signals are placed, and the amount of overhead when transmitting pilot signals is 16.67%. 4 × 3 base units can be sequentially allocated on the frequency axis or time axis.

If two REs for pilots are used per 4 × 3 base unit, pilot overhead can be reduced to half the size of a traditional uplink PUSC structure according to IEEE 802.16e. In order to guarantee reliable channel estimation performance for both the low speed user case and the high speed user case, it is preferable to place the REs for the pilot signals in the 4 × 3 base unit in a distributed manner from both ends (i.e., the first and third characters) on the time axis in the base unit 4 × 3. In addition, in order to guarantee reliable channel estimation performance with regard to frequency selectivity in channel estimation on the frequency axis, it is preferable to allocate REs for the pilot signals to both ends (i.e., the first and fourth subcarriers) on the frequency axis in a 4 × 3 base unit.

It can be seen on the left side of FIG. 2A that, in each 4 × 3 base unit, the pilot REs are located at the subcarrier index “0” when s = 0, and at the subcarrier index “3” when s = 2. Here, the subcarrier index is an integer of not less than 0, which increases from top to bottom, and the OFDM (A) symbol index “s” is an integer of not less than 0, which increases from left to right.

You can also see on the right side of FIG. 2A that, in each 4 × 3 base unit, the pilot REs are located at the subcarrier index “3” when s = 0, and at the subcarrier index “0” when s = 2. The RE locations for the pilot signals may cyclically shift along a time axis or a frequency axis. These pilot patterns are summarized in the following tables.

Table 1 s = 0 s = 1 s = 2 SC = 0 P - - SC = 1 - - - SC = 2 - - - SC = 3 - - P

table 2 s = 0 s = 1 s = 2 SC = 0 - - P SC = 1 - - - SC = 2 - - - SC = 3 P - -

In Tables 1 and 2, “P” indicates RE for pilot signals, “-” indicates RE for data, “s” indicates an OFDM (A) symbol index in a base unit, and “SC” indicates a subcarrier index in a base unit.

FIG. 2B and 2C illustrate an example in which REs for pilots in 2Tx or 2 streams and in 4Tx or 4 streams are allocated when the base unit size is expanded to 4 subcarriers × 6 OFDM (A) symbols according to another embodiment of the present invention. The pilot patterns of FIG. 2B and 2C are extended versions of the pilot pattern of FIG. 2A according to a plurality of antennas.

As shown in FIG. 2B, in a 4 × 6 base unit, two REs for pilot signals in 2Tx or 2 streams are allocated for each antenna port, and the total amount of overhead when transmitting pilot signals is 16.67%. 4x6 base units can be sequentially allocated on the frequency axis or time axis. REs for the pilot signals for antenna port 0 are located at the subcarrier index “0” when s = 0, and at the index of the subcarrier “3” when s = 5. REs for the pilot signals for antenna port 1 are located at the subcarrier index “3” when s = 2, and at the index of the subcarrier “0” when s = 3. In another example, the REs for the pilot signals for antenna port 0 are located at the subcarrier index “3” when s = 0, and at the index of the subcarrier “0” when s = 5. REs for the pilot signals for antenna port 1 are located at the subcarrier index “0” when s = 2, and at the index of the subcarrier “3” when s = 3. Antenna ports 0 and 1 can switch among themselves. Thus, the antenna ports 0 and 1 can be replaced by each other. For example, the REs for the pilot signals for antenna port 0 are located at the subcarrier index “3” when s = 2, and at the index of the subcarrier “0” when s = 3. And the REs for the pilot signals for antenna port 1 are located at the subcarrier index “0” when s = 0, and at the index of the subcarrier “3” when s = 5.

The RE locations for the pilot signals may cyclically shift along a time axis or a frequency axis. These pilot patterns are summarized in the following tables.

Table 3 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 P0 - - P1 - - SC = 1 - - - - - - SC = 2 - - - - - - SC = 3 - - P1 - - P0

Table 4 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 - - P1 - - P0 SC = 1 - - - - - - SC = 2 - - - - - - SC = 3 P0 - - P1 - -

In Tables 3 and 4, “P0” and “P1” indicate the corresponding REs for the pilot signals for antenna ports 0 and 1, “-” indicates the REs for the data, “s” indicates the index of the OFDM (A) symbol in the base unit, and “ SC "indicates the subcarrier index in the base unit.

As shown in FIG. 2C, in a 4 × 6 base unit, two REs for pilots in 4Tx or 4 streams are allocated for each antenna port, and the total amount of overhead when transmitting pilots is 33.34%. 4x6 base units can be sequentially allocated on the frequency axis or time axis. REs for the pilot signals for antenna port 0 are located at the subcarrier index “0” when s = 0, and at the index of the subcarrier “3” when s = 5. REs for the pilot signals for antenna port 1 are located at the subcarrier index “3” when s = 2, and at the index of the subcarrier “0” when s = 3. REs for the pilot signals for antenna port 2 are located at the subcarrier index “3” when s = 0, and at the subcarrier index “0” when s = 5. REs for the pilot signals for antenna port 3 are located at the subcarrier index “0” when s = 2, and at the index of the subcarrier “3” when s = 3. In another example, the REs for the pilot signals for the antenna port (s) 0 are located at the subcarrier index “3” when s = 0, and at the subcarrier index “0” when s = 5. REs for the pilot signals for antenna port 1 are located at the subcarrier index “0” when s = 2, and at the index of the subcarrier “3” when s = 3. REs for the pilot signals for antenna port 2 are located at the subcarrier index “0” when s = 0, and at the index of the subcarrier “3” when s = 5. REs for the pilot signals for antenna port 3 are located at a subcarrier index of "3" when s = 2, and at a subcarrier index of "0" when s = 3. Antenna ports can switch among themselves. The RE locations for the pilot signals may cyclically shift along a time axis or a frequency axis. These pilot patterns are summarized in the following tables.

Table 5 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 P0 - P3 P1 - P2 SC = 1 - - - - - - SC = 2 - - - - - - SC = 3 P2 - P1 P3 P0

Table 6 one s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 P2 - P1 P3 - P0 SC = 1 - - - - - - SC = 2 - - - - - - SC = 3 P0 - P3 P1 - P2

In Tables 5 and 6, “P0” - “P3” indicate the corresponding REs for the pilot signals for antenna ports 0-3, “-” indicates the REs for the data, “s” indicates the OFDM (A) symbol index in the base unit, and “ SC "indicates the subcarrier index in the base unit.

FIG. 3A illustrates an example in which pilot signals in 1Tx or 1 stream are allocated when each base unit includes 4 subcarriers × 3 of an OFDM (A) symbol according to another embodiment of the present invention. In each 4 × 3 base unit, two pilot signals are placed, and the amount of overhead when transmitting pilot signals is 16.67%. 4 × 3 base units can be sequentially allocated on the frequency axis or time axis.

If two REs for pilots are used per 4 × 3 base unit, pilot overhead can be reduced to half the size of a traditional uplink PUSC structure according to IEEE 802.16e. In addition, in order to guarantee reliable channel estimation performance with regard to frequency selectivity in channel estimation on the frequency axis, it is preferable to allocate pilot signals to a 4 × 3 base unit at both ends (i.e., the first and fourth subcarriers) on the frequency axis in a 4 × base unit 3. It can be seen in FIG. 3A that, in each 4 × 3 base unit, the pilot REs are located at a subcarrier index of “0” and at a subcarrier index of “3” when s = 1. The RE locations for the pilot signals may cyclically shift along a time axis or a frequency axis. These pilot patterns are summarized in the following table.

Table 7 s = 0 s = 1 s = 2 SC = 0 - P - SC = 1 - - - SC = 2 - - - SC = 3 - P -

In Table 7, “P” indicates RE for pilot signals, “-” indicates RE for data, “s” indicates an OFDM (A) symbol index in a base unit, and “SC” indicates a subcarrier index in a base unit.

FIG. 3B and 3C illustrate an example in which pilots in 2Tx or 2 streams and 4Tx or 4 streams are allocated when the base unit size is expanded to 4 subcarriers × 6 OFDM (A) symbols according to another embodiment of the present invention. The pilot patterns of FIG. 3B and 3C are extended versions of the pilot pattern of FIG. 3A according to a plurality of antennas.

As shown in FIG. 3B, in a 4 × 6 base unit, two REs for pilot signals in 2Tx or 2 streams are placed for each antenna port, and the total amount of overhead when transmitting pilot signals is 16.67%. 4x6 base units can be sequentially allocated on the frequency axis or time axis. REs for the pilot signals for antenna port 0 are located at the subcarrier index “0” when s = 1, and at the index of the subcarrier “3” when s = 4. REs for the pilot signals for antenna port 1 are located at a subcarrier index of "3" when s = 1, and at a subcarrier index of "0" when s = 4. Antenna ports can switch among themselves. The RE locations for the pilot signals may cyclically shift along a time axis or a frequency axis. These pilot patterns are summarized in the following table.

Table 8 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 - P0 - - P1 - SC = 1 - - - - - - SC = 2 - - - - - - SC = 3 - P1 - - P0 -

In Table 8, “P0” and “P1” indicate the corresponding REs for the pilot signals for antenna ports 0 and 1, “-” indicates the REs for the data, “s” indicates the index of the OFDM (A) symbol in the base unit, and “SC” indicates the subcarrier index in the base unit.

As shown in FIG. 3C, in a 4 × 6 base unit, two REs for pilots in 4Tx or 4 streams are allocated for each antenna port, and the total amount of overhead when transmitting pilots is 33.34%. 4 × 6 base units can be sequentially allocated on the frequency axis or time axis. REs for the pilot signals for antenna port 0 are located at the subcarrier index “0” when s = 1, and at the index of the subcarrier “3” when s = 4. REs for the pilot signals for antenna port 1 are located at a subcarrier index of "3" when s = 1, and at a subcarrier index of "0" when s = 4. REs for the pilot signals for antenna port 2 are located at the subcarrier index “1” when s = 1, and at the index of the subcarrier “2” when s = 4. REs for the pilot signals for antenna port 3 are located at the subcarrier index “2” when s = 1, and at the index of the subcarrier “1” when s = 4. Antenna ports can switch among themselves. The RE locations for the pilot signals may cyclically shift along a time axis or a frequency axis. These pilot patterns are summarized in the following table.

Table 9 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 - P0 - - P1 - SC = 1 - P2 - - P3 - SC = 2 - P3 - - P2 - SC = 3 - P1 - - P0 -

In Table 9, “P0” - “P3” indicate the corresponding REs for the pilot signals for antenna ports 0-3, “-” indicates the REs for the data, “s” indicates the OFDM (A) -code index in the base unit, and “SC” indicates the subcarrier index in the base unit.

FIG. 4A illustrates an example in which pilot signals in 1Tx or 1 stream are allocated when each base unit includes 4 subcarriers × 3 of an OFDM (A) symbol according to another embodiment of the present invention. In each 4 × 3 base unit, two pilot signals are placed, and the amount of overhead when transmitting pilot signals is 16.67%. 4 × 3 base units can be sequentially allocated on the frequency axis or time axis.

If two REs for pilots are used per 4 × 3 base unit, pilot overhead can be reduced to half the size of a traditional uplink PUSC structure according to IEEE 802.16e. In order to guarantee reliable channel estimation performance for both the low speed user case and the high speed user case, it is preferable to place the pilot signals next to each other on the time axis in a 4 × 3 base unit. In addition, in order to guarantee reliable channel estimation performance with regard to frequency selectivity in channel estimation on the frequency axis, it is preferable to allocate pilot signals to a 4 × 3 base unit at both ends (i.e., the first and fourth subcarriers) on the frequency axis in a 4 × base unit 3. REs for the pilot signals are located at the subcarrier index “0” when s = 1, and at the index of the subcarrier “3” when s = 2. In another example, the REs for the pilot signals are located at the subcarrier index “0” when s = 0, and at the subcarrier index “3” when s = 1. The RE locations for the pilot signals may cyclically shift along a time axis or a frequency axis. These pilot patterns are summarized in the following tables.

Table 10 s = 0 s = 1 s = 2 SC = 0 - P - SC = 1 - - - SC = 2 - - - SC = 3 - - P

Table 11 s = 0 s = 1 s = 2 SC = 0 P - - SC = 1 - - - SC = 2 - - - SC = 3 - R -

In Tables 10 and 11, “P” indicates RE for pilot signals, “-” indicates RE for data, “s” indicates an OFDM (A) symbol index in a base unit, and “SC” indicates a subcarrier index in a base unit.

FIG. 4B and 4C illustrate an example in which pilots in 2Tx or 2 streams and in 4Tx or 4 streams are allocated when the base unit size is expanded to 4 subcarriers × 6 OFDM (A) symbols according to another embodiment of the present invention. The pilot patterns of FIG. 4B and 4C are extended versions of the pilot pattern of FIG. 4A according to a plurality of antennas.

As shown in FIG. 4B, in a 4 × 6 base unit, two REs for pilot signals in 2Tx or 2 streams are placed for each antenna port, and the total amount of overhead when transmitting pilot signals is 16.67%. 4 × 6 base units can be sequentially allocated on the frequency axis or time axis. REs for the pilot signals for antenna port 0 are located at the subcarrier index “0” when s = 1, and at the index of the subcarrier “3” when s = 5. REs for the pilot signals for 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, the REs for the pilot signals for antenna port 0 are located at the subcarrier index “0” when s = 0, and at the index of the subcarrier “3” when s = 4. REs for the pilot signals for antenna port 1 are located at a subcarrier index of "3" when s = 1, and at a subcarrier index of "0" when s = 3. Antenna ports can switch among themselves. The RE locations for the pilot signals may cyclically shift along a time axis or a frequency axis. These pilot patterns are summarized in the following tables.

Table 12 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 - P0 - - P1 - SC = 1 - - - - - - SC = 2 - - - - - - SC = 3 - - P1 - - P0

Table 13 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 P0 - - P1 - - SC = 1 - - - - - - SC = 2 - - - - - - SC = 3 - P1 - - P0 -

In Tables 12 and 13, “P0” and “P1” indicate the corresponding REs for the pilot signals for antenna ports 0 and 1, “-” indicates the REs for the data, “s” indicates the index of the OFDM (A) symbol in the base unit, and “ SC "indicates the subcarrier index in the base unit.

As shown in FIG. 4C, in a 4 × 6 base unit, two REs for pilots in 4Tx or 4 streams are allocated for each antenna port, and the total amount of overhead when transmitting pilots is 33.34%. 4 × 6 base units can be sequentially allocated on the frequency axis or time axis. REs for the pilot signals for antenna port 0 are located at the subcarrier index “0” when s = 1, and at the index of the subcarrier “3” when s = 5. REs for the pilot signals for antenna port 1 are located at a subcarrier index of "3" when s = 2, and at a subcarrier index of "0" when s = 4. REs for the pilot signals for antenna port 2 are located at the subcarrier index “0” when s = 0, and at the index of the subcarrier “3” when s = 4. REs for the pilot signals for 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, the REs for the pilot signals for antenna port 0 are located at the subcarrier index “0” when s = 0, and at the index of the subcarrier “3” when s = 4. REs for the pilot signals for antenna port 1 are located at a subcarrier index of "3" when s = 1, and at a subcarrier index of "0" when s = 3. REs for the pilot signals for antenna port 2 are located at the subcarrier index “0” when s = 1, and at the index of the subcarrier “3” when s = 5. REs for the pilot signals for antenna port 3 are located at the subcarrier index “3” when s = 2, and at the index of the subcarrier “0” when s = 4. Antenna ports can switch among themselves. The RE locations for the pilot signals may cyclically shift along a time axis or a frequency axis. These pilot patterns are summarized in the following tables.

Table 14 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 P2 P0 - P3 P1 - SC = 1 - - - - - - SC = 2 - - - - - - SC = 3 - P3 P1 - P2 P0

Table 15 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 P0 P2 - P1 P3 - SC = 1 - - - - - - SC = 2 - - - - - - SC = 3 - P1 P3 - P0 P2

In tables 14 and 15, "P0" - "P3" indicate the corresponding REs for the pilot signals for antenna ports 0-3, "-" indicates the REs for the data, "s" indicates the index of the OFDM (A) symbol in the base unit, and " SC "indicates the subcarrier index in the base unit.

FIG. 5A-5C illustrate an example in which pilot signals in 1Tx or 1 stream, in 2Tx or 2 streams, and in 4Tx or 4 streams are allocated when each base unit includes 4 subcarriers × 6 OFDM (A) symbols according to another embodiment of the present invention. 4 × 6 base units can be sequentially allocated on the frequency axis or time axis.

As shown in FIG. 5A, RE for the pilot signals are arranged at the subcarrier index “0”, when s = 0, at the subcarrier index “2”, when s = 1, at the subcarrier index “1”, when s = 4, and at the subcarrier index “3” when s = 5. In another example, the REs for the pilot signals are located at the subcarrier index “3”, when s = 0, at the subcarrier index “1”, when s = 1, at the subcarrier index “2”, when s = 4, and at the subcarrier index “0 "when s = 5. In another example, the REs for the pilot signals are located at the subcarrier index “1”, when s = 0, at the subcarrier index “3”, when s = 2, at the subcarrier index “0”, when s = 3, and at the subcarrier index “2 "when s = 5. In another example, the REs for the pilot signals are located at the subcarrier index “2”, when s = 0, at the subcarrier index “0”, when s = 2, at the subcarrier index “3”, when s = 3, and at the subcarrier index “1 "when s = 5. The RE locations for the pilot signals may cyclically shift along a time axis or a frequency axis. These pilot patterns are summarized in the following tables.

Table 16 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 P - - - - - SC = 1 - - - - P - SC = 2 - P - - - - SC = 3 - - - - - P

Table 17 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 - - - - - P SC = 1 - P - - - - SC = 2 - - - - P - SC = 3 P - - - - -

Table 18 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 - - - P - - SC = 1 P - - - - - SC = 2 - - - - - P SC = 3 - - P - - -

Table 19 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 - - P - - - SC = 1 - - - - - P SC = 2 P - - - - - SC = 3 - - - P - -

In Tables 16-19, “P” indicates RE for pilots, “-” indicates RE for data, “s” indicates an OFDM (A) symbol index in a base unit, and “SC” indicates a subcarrier index in a base unit.

As shown in FIG. 5B, in a 4 × 6 base unit, two REs for pilot signals in 2Tx or 2 streams are allocated for each antenna port, and the total amount of overhead when transmitting pilot signals is 16.67%. REs for the pilot signals for antenna port 0 are located at the subcarrier index “0” when s = 0, and at the index of the subcarrier “3” when s = 5. REs for the pilot signals for antenna port 1 are located at the subcarrier index “2” when s = 1, and at the index of the subcarrier “1” when s = 4. In another example, the REs for the pilot signals for antenna port 0 are located at the subcarrier index “3” when s = 0, and at the index of the subcarrier “0” when s = 5. REs for the pilot signals for antenna port 1 are located at the subcarrier index “1” when s = 1, and at the index of the subcarrier “2” when s = 4. In another example, the REs for the pilot signals for antenna port 0 are located at the subcarrier index “l” when s = 0, and at the subcarrier index “2” when s = 5. REs for the pilot signals for antenna port 1 are located at the subcarrier index “3” when s = 2, and at the index of the subcarrier “0” when s = 3. In another example, the REs for the pilot signals for antenna port 0 are located at the subcarrier index “2” when s = 0, and at the index of the subcarrier “1” when s = 5. REs for the pilot signals for antenna port 1 are located at the subcarrier index “0” when s = 2, and at the index of the subcarrier “3” when s = 3. Antenna ports can switch among themselves. The RE locations for the pilot signals may cyclically shift along a time axis or a frequency axis. These pilot patterns are summarized in the following tables.

Table 20 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 P0 - - - - - SC = 1 - - - - P1 - SC = 2 - P1 - - - - SC = 3 - - - - - P0

Table 21 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 - - - - - P0 SC = 1 - P1 - - - - SC = 2 - - - - P1 - SC = 3 P0 - - - - -

Table 22 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 - - - P1 - - SC = 1 P0 - - - - - SC = 2 - - - - - P0 SC = 3 - - P1 - - -

Table 23 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 - - P1 - - - SC = 1 - - - - - P0 SC = 2 P0 - - - - - SC = 3 - - - P1 - -

In Tables 20-23, “P0” and “P1” indicate the corresponding REs for the pilot signals for antenna ports 0 and 1, “-” indicates the REs for the data, “s” indicates the index of the OFDM (A) symbol in the base unit, and “ SC "indicates the subcarrier index in the base unit.

As shown in FIG. 5C, in a 4 × 6 base unit, two REs for pilots in 4Tx or 4 streams are allocated for each antenna port, and the total amount of overhead when transmitting pilots is 33.34%. REs for the pilot signals for antenna port 0 are located at the subcarrier index “0” when s = 0, and at the index of the subcarrier “3” when s = 5. REs for the pilot signals for antenna port 1 are located at the subcarrier index “2” when s = 1, and at the index of the subcarrier “1” when s = 4. REs for the pilot signals for antenna port 2 are located at the subcarrier index “3” when s = 0, and at the subcarrier index “0” when s = 5. REs for the pilot signals for antenna port 3 are located at the subcarrier index “1” when s = 1, and at the index of the subcarrier “2” when s = 4. In another example, the REs for the pilot signals for antenna port 0 are located at the subcarrier index “3” when s = 0, and at the index of the subcarrier “0” when s = 5. REs for the pilot signals for antenna port 1 are located at the subcarrier index “1” when s = 1, and at the index of the subcarrier “2” when s = 4. REs for the pilot signals for antenna port 2 are located at the subcarrier index “0” when s = 0, and at the index of the subcarrier “3” when s = 5. REs for the pilot signals for antenna port 3 are located at the subcarrier index “2” when s = 1, and at the index of the subcarrier “1” when s = 4.

In another example, the REs for the pilot signals for antenna port 0 are located at the subcarrier index “1” when s = 0, and at the index of the subcarrier “2” when s = 5. REs for the pilot signals for antenna port 1 are located at the subcarrier index “3” when s = 2, and at the index of the subcarrier “0” when s = 3. REs for the pilot signals for antenna port 2 are located at the subcarrier index “2” when s = 0, and at the index of the subcarrier “1” when s = 5. REs for the pilot signals for antenna port 3 are located at the subcarrier index “0” when s = 2, and at the index of the subcarrier “3” when s = 3. In another example, the REs for the pilot signals for antenna port 0 are located at the subcarrier index “2” when s = 0, and at the index of the subcarrier “1” when s = 5. REs for the pilot signals for antenna port 1 are located at the subcarrier index “0” when s = 2, and at the index of the subcarrier “3” when s = 3. REs for the pilot signals for antenna port 2 are located at the subcarrier index “1” when s = 0, and at the index of the subcarrier “2” when s = 5. REs for the pilot signals for antenna port 3 are located at a subcarrier index of "3" when s = 2, and at a subcarrier index of "0" when s = 3. Antenna ports can switch among themselves. The RE locations for the pilot signals may cyclically shift along a time axis or a frequency axis. These pilot patterns are summarized in the following tables.

Table 24 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 P0 - - - - P2 SC = 1 - P3 - - P1 - SC = 2 - P1 - - P3 - SC = 3 P2 - - - - P0

Table 25 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 P2 - - - - P0 SC = 1 - P1 - - P3 - SC = 2 - P3 - - P1 - SC = 3 P0 - - - - P2

Table 26 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 - - P3 P1 - - SC = 1 P0 - - - - P2 SC = 2 P2 - - - - P0 SC = 3 - - P1 P3 - -

Table 27 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 - - P1 P3 - - SC = 1 P2 - - - - P0 SC = 2 P0 - - - - P2 SC = 3 - - P3 P1 - -

In Tables 24-27, “P0” to “P3” indicate the corresponding REs for the pilot signals for antenna ports 0-3, “-” indicates the REs for the data, “s” indicates the OFDM (A) symbol index in the base unit, and "SC" indicates the subcarrier index in the base unit.

FIG. 6A-6C illustrate an example in which pilot signals in 1Tx or 1 stream, in 2Tx or 2 streams, and in 4Tx or 4 streams are allocated when each base unit includes 4 subcarriers × 6 OFDM (A) symbols according to another embodiment of the present invention. 4 × 6 base units can be sequentially allocated on the frequency axis or time axis.

As shown in FIG. 6A, RE for the pilot signals are arranged at the subcarrier index “0” and at the subcarrier index “2” when s = 1, and are located at the subcarrier index “1” and at the subcarrier index “3” when s = 4. In another example, the REs for the pilot signals are located at the subcarrier index “1” and at the subcarrier index “3” when s = 1, and are located at the subcarrier index “0” and at the subcarrier index “2” when s = 4. The RE locations for the pilot signals may cyclically shift along a time axis or a frequency axis. These pilot patterns are summarized in the following tables.

Table 28 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 - P - - - - SC = 1 - - - - P - SC = 2 - P - - - - SC = 3 - - - - P -

Table 29 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 - - - - P - SC = 1 - P - - - - SC = 2 - - - - P - SC = 3 - P - - - -

In Tables 28 and 29, “P” indicates RE for pilot signals, “-” indicates RE for data, “s” indicates an OFDM (A) symbol index in a base unit, and “SC” indicates a subcarrier index in a base unit.

As shown in FIG. 6B, in a 4 × 6 base unit, two REs for pilot signals in 2Tx or 2 streams are allocated for each antenna port, and the total amount of overhead when transmitting pilot signals is 16.67%. REs for the pilot signals for antenna port 0 are located at the subcarrier index “0” when s = 1, and at the index of the subcarrier “3” when s = 4. REs for the pilot signals for antenna port 1 are located at the subcarrier index “2” when s = 1, and at the index of the subcarrier “1” when s = 4. In another example, the REs for the pilot signals for antenna port 0 are located at the subcarrier index “3” when s = 1, and at the index of the subcarrier “0” when s = 4. REs for the pilot signals for antenna port 1 are located at the subcarrier index “1” when s = 1, and at the index of the subcarrier “2” when s = 4. Antenna ports can switch among themselves. The RE locations for the pilot signals may cyclically shift along a time axis or a frequency axis. These pilot patterns are summarized in the following tables.

Table 30 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 - P0 - - - - SC = 1 - - - - P1 - SC = 2 - P1 - - - - SC = 3 - - - - P0 -

Table 31 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 - - - - P0 - SC = 1 - P1 - - - - SC = 2 - - - - P1 - SC = 3 - P0 - - - -

In tables 30 and 31, “P0” and “P1” indicate the corresponding REs for the pilot signals for antenna ports 0 and 1, “-” indicates the REs for the data, “s” indicates the index of the OFDM (A) symbol in the base unit, and “ SC "indicates the subcarrier index in the base unit.

As shown in FIG. 6C, in a 4 × 6 base unit, two REs for pilots in 4Tx or 4 streams are allocated for each antenna port, and the total amount of overhead when transmitting pilots is 33.34%. REs for the pilot signals for antenna port 0 are located at the subcarrier index “0” when s = 1, and at the index of the subcarrier “3” when s = 4. REs for the pilot signals for antenna port 1 are located at the subcarrier index “2” when s = 1, and at the index of the subcarrier “1” when s = 4. REs for the pilot signals for antenna port 2 are located at the subcarrier index “1” when s = 1, and at the index of the subcarrier “2” when s = 4. REs for the pilot signals for 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, the REs for the pilot signals for antenna port 0 are located at the subcarrier index “3” when s = 1, and at the index of the subcarrier “0” when s = 4. REs for the pilot signals for antenna port 1 are located at the subcarrier index “1” when s = 1, and at the index of the subcarrier “2” when s = 4. REs for the pilot signals for antenna port 2 are located at the subcarrier index “2” when s = 1, and at the index of the subcarrier “1” when s = 4. REs for the pilot signals for antenna port 3 are located at the subcarrier index “0” when s = 1, and at the index of the subcarrier “3” when s = 4. Antenna ports can switch among themselves. The RE locations for the pilot signals may cyclically shift along a time axis or a frequency axis. These pilot patterns are summarized in the following tables.

Table 32 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 - P0 - - P3 - SC = 1 - P2 - - P1 - SC = 2 - P1 - - P2 - SC = 3 - P3 - - P0 -

Table 33 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 - P3 - - P0 - SC = 1 - P1 - - P2 - SC = 2 - P2 - - P1 - SC = 3 - P0 - - P3 -

In Tables 32 and 33, “P0” - “P3” indicate the corresponding REs for the pilot signals for antenna ports 0-3, “-” indicates the REs for the data, “s” indicates the OFDM (A) symbol index in the base unit, and “ SC "indicates the subcarrier index in the base unit.

FIG. 7A-7C illustrate an example in which pilot signals in 1Tx or 1 stream, in 2Tx or 2 streams, and in 4Tx or 4 streams are allocated when each base unit includes 4 subcarriers × 6 OFDM (A) symbols according to another embodiment of the present invention. 4 × 6 base units can be sequentially allocated on the frequency axis or time axis.

As shown in FIG. 7A, RE for the pilot signals are arranged at the subcarrier index “1”, when s = 1, at the subcarrier index “3”, when s = 2, at the subcarrier index “0”, when s = 3, and at the subcarrier index “2” when s = 4. In another example, the REs for the pilot signals are located at the subcarrier index “2”, when s = 1, at the subcarrier index “0”, when s = 2, at the subcarrier index “3”, when s = 3, and at the subcarrier index “1 "when s = 4. The RE locations for the pilot signals may cyclically shift along a time axis or a frequency axis. These pilot patterns are summarized in the following tables.

Table 34 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 - - - P - - SC = 1 - P - - - - SC = 2 - - - - P - SC = 3 - - P - - -

Table 35 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 - - P - - - SC = 1 - - - - P - SC = 2 - P - - - - SC = 3 - - - P - -

In Tables 34 and 35, “P” indicates RE for pilot signals, “-” indicates RE for data, “s” indicates an OFDM (A) symbol index in a base unit, and “SC” indicates a subcarrier index in a base unit.

As shown in FIG. 7B, in a 4 × 6 base unit, two REs for pilot signals in 2Tx or 2 streams are allocated for each antenna port, and the total amount of overhead when transmitting pilot signals is 16.67%. REs for the pilot signals for antenna port 0 are located at the subcarrier index “1” when s = 1, and at the index of the subcarrier “2” when s = 4. REs for the pilot signals for antenna port 1 are located at the subcarrier index “3” when s = 2, and at the index of the subcarrier “0” when s = 3. In another example, the REs for the pilot signals for antenna port 0 are located at the subcarrier index “2” when s = 1, and at the index of the subcarrier “1” when s = 4. REs for the pilot signals for antenna port 1 are located at the subcarrier index “0” when s = 2, and at the index of the subcarrier “3” when s = 3. Antenna ports can switch among themselves. The RE locations for the pilot signals may cyclically shift along a time axis or a frequency axis. These pilot patterns are summarized in the following tables.

Table 36 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 - - - P1 - - SC = 1 - P0 - - - - SC = 2 - - - - P0 - SC = 3 - - P1 - - -

Table 37 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 - - P1 - - - SC = 1 - - - - P0 - SC = 2 - P0 - - - - SC = 3 - - - P1 - -

In Tables 36-37, “P0” and “P1” indicate the corresponding REs for the pilot signals for antenna ports 0 and 1, “-” indicates the REs for the data, “s” indicates the index of the OFDM (A) symbol in the base unit, and “ SC "indicates the subcarrier index in the base unit.

As shown in FIG. 7C, in a 4 × 6 base unit, two REs for pilots in 4Tx or 4 streams are allocated for each antenna port, and the total amount of overhead when transmitting pilots is 33.34%. REs for the pilot signals for antenna port 0 are located at the subcarrier index “1” when s = 1, and at the index of the subcarrier “2” when s = 4. REs for the pilot signals for antenna port 1 are located at the subcarrier index “3” when s = 2, and at the index of the subcarrier “0” when s = 3. REs for the pilot signals for antenna port 2 are located at the subcarrier index “2” when s = 1, and at the index of the subcarrier “1” when s = 4. REs for the pilot signals for antenna port 3 are located at the subcarrier index “0” when s = 2, and at the index of the subcarrier “3” when s = 3. In another example, the REs for the pilot signals for antenna port 0 are located at the subcarrier index “2” when s = 1, and at the index of the subcarrier “1” when s = 4. REs for the pilot signals for antenna port 1 are located at the subcarrier index “0” when s = 2, and at the index of the subcarrier “3” when s = 3. REs for the pilot signals for antenna port 2 are located at the subcarrier index “1” when s = 1, and at the index of the subcarrier “2” when s = 4. REs for the pilot signals for antenna port 3 are located at a subcarrier index of "3" when s = 2, and at a subcarrier index of "0" when s = 3. Antenna ports can switch among themselves. The RE locations for the pilot signals may cyclically shift along a time axis or a frequency axis. These pilot patterns are summarized in the following tables.

Table 38 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 - - P3 P1 - - SC = 1 - P0 - - P2 - SC = 2 - P2 - - P0 - SC = 3 - - P1 P3 - -

Table 39 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 - - P1 P3 - - SC = 1 - P2 - - P0 - SC = 2 - P0 - - P2 - SC = 3 - - P3 P1 - -

In Tables 38 and 39, “P0” - “P3” indicate the corresponding REs for the pilot signals for antenna ports 0-3, “-” indicates the REs for the data, “s” indicates the OFDM (A) symbol index in the base unit, and “ SC "indicates the subcarrier index in the base unit.

FIG. 8A-8C illustrate an example in which pilot signals in 1Tx or 1 stream, in 2Tx or 2 streams, and in 4Tx or 4 streams are allocated when each base unit includes 4 subcarriers × 6 OFDM (A) symbols according to another embodiment of the present invention. 4 × 6 base units can be sequentially allocated on the frequency axis or time axis.

As shown in FIG. 8A, if two REs for pilot signals are used per 4 × 6 base unit, pilot overhead can be reduced to half the size of a traditional uplink PUSC structure according to IEEE 802.16e. In order to guarantee reliable channel estimation performance for a low speed user case, it is preferable to place the pilot signals in the 4 × 6 base unit in a distributed manner at both ends on the time axis in the 4 × 6 base unit. In addition, in order to guarantee reliable channel estimation performance with regard to frequency selectivity in channel estimation on the frequency axis, it is preferable to allocate pilot signals to a 4 × 6 base unit at both ends (i.e., the first and fourth subcarriers) on the frequency axis in a 4 × base unit 6. In each base unit, 4 × 6 REs for the pilot signals are located at the subcarrier index “0” and at the subcarrier index “3” when s = 0, and are located at the subcarrier index “0” and at the subcarrier index “3” when s = 5. The RE locations for the pilot signals may cyclically shift along a time axis or a frequency axis. These pilot patterns are summarized in the following table.

Table 40 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 P - - - - P SC = 1 - - - - - - SC = 2 - - - - - - SC = 3 P - - - - P

In table 40, “P” indicates RE for pilots, “-” indicates RE for data, “s” indicates an OFDM (A) symbol index in a base unit, and “SC” indicates a subcarrier index in a base unit.

As shown in FIG. 8B, in a 4 × 6 base unit, two REs for pilot signals in 2Tx or 2 streams are allocated for each antenna port, and the total amount of overhead when transmitting pilot signals is 16.67%. REs for the pilot signals for antenna port 0 are located at the subcarrier index “0” when s = 0, and at the index of the subcarrier “3” when s = 5. REs for the pilot signals for antenna port 1 are located at the subcarrier index “3” when s = 0, and at the index of the subcarrier “0” when s = 5. Antenna ports can switch among themselves. The RE locations for the pilot signals may cyclically shift along a time axis or a frequency axis. These pilot patterns are summarized in the following table.

Table 41 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 P0 - - - - P1 SC = 1 - - - - - - SC = 2 - - - - - - SC = 3 P1 - - - - P0

In table 41, “P0” and “P1” indicate the corresponding REs for the pilot signals for antenna ports 0 and 1, “-” indicates the REs for the data, “s” indicates the index of the OFDM (A) symbol in the base unit, and “SC” indicates the subcarrier index in the base unit.

These pilot patterns, in particular, are preferred for uplink transmission with 2Tx antennas or in 2 streams for the following reasons.

First, in the case of a wireless communication system that supports multi-input and multi-output (MIMO) technologies, the pilot patterns of FIG. 8B can effectively support a space time block code (STBC) and a space frequency block code (STBC). To support STBC, subcarriers for transmitting control information and data, excluding pilot signals, must comprise an even number of OFDM (A) characters on the time axis. In particular, the sequential allocation of paired OFDM (A) -characters in each unit of subcarriers allows to achieve an additional increase in STBC performance. This is because high magnification can be achieved in STBC if the channels that use the paired OFDM (A) symbols in each unit of subcarriers are identical or similar. With reference to FIG. 8B, OFDM (A) symbols in each unit of subcarriers, excluding pilot signals, are sequential on the time axis and are even in number. In order to support SFBC, the number of subcarriers for transmitting control information and data, excluding pilot signals, must be even on the frequency axis. In particular, the sequential allocation of paired subcarriers in each OFDM (A) symbol allows for an additional increase in SFBC performance. This is because a high magnification can be achieved in SFBC if the channels that use the paired subcarriers are identical or similar. With reference to FIG. 8B, the subcarriers, excluding the pilot signals in each OFDM (A) symbol, are sequential and are even in number. The pilot patterns of FIG. 8B can effectively support the MIMO system.

Secondly, since the pilot signals for antenna ports 0 and 1 are allocated to the same OFDM (A) symbol, it is possible to increase the performance of channel estimation through amplification of the pilot signals. For example, when data and pilots for antenna port 0 are transmitted, REs for pilots for antenna port 1 are not transmitted. In this case, the power for allocating pilot signals for antenna port 1 can additionally be allocated to pilot signals for antenna port 0. This allows you to increase the performance of the channel estimation through the amplification of the pilot signals. It also helps in solving the problem of power balancing in uplink transmission with limited available power.

Thirdly, it is possible to perform an efficient channel estimation using the maximum possible amount of coherent time and coherent bandwidth. In particular, even in an environment in which the spread of delays in the channel is significant, the channels almost never change or change only slightly in 4 consecutive units of subcarriers. If the terminal does not move at high speed, the channel change is small in 6 or less consecutive OFDM (A) characters. In addition, even when the terminal speed increases so that it uses a high-speed channel, the channel changes linearly in 6 or less consecutive OFDM (A) -characters. With reference to FIG. 8B, 2 pilot signals for each of the antenna ports 0 and 1 are located at both diagonal ends of the 4 × 6 base unit. They use the maximum possible amount of coherent time and coherent bandwidth, thereby achieving an effective channel estimate.

Fourth, since the pilot signals are allocated to each 4 × 6 base unit at the borders, it is possible to prevent a decrease in channel estimation performance due to extrapolation during channel estimation.

As shown in FIG. 8C, in a 4 × 6 base unit, two REs for pilots in 4Tx or 4 streams are allocated for each antenna port, and the total amount of overhead when transmitting pilots is 33.34%. REs for the pilot signals for antenna port 0 are located at the subcarrier index “0” when s = 0, and at the index of the subcarrier “3” when s = 5. REs for the pilot signals for antenna port 1 are located at the subcarrier index “3” when s = 0, and at the index of the subcarrier “0” when s = 5. REs for the pilot signals for antenna port 2 are located at the subcarrier index “1” when s = 0, and at the index of the subcarrier “2” when s = 5. REs for the pilot signals for antenna port 3 are located at the subcarrier index “2” when s = 0, and at the index of the subcarrier “1” when s = 5. Antenna ports can switch among themselves. The RE locations for the pilot signals may cyclically shift along a time axis or a frequency axis. These pilot patterns are summarized in the following table.

Table 42 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 P0 - - - - P1 SC = 1 P2 - - - - P3 SC = 2 P3 - - - - P2 SC = 3 P1 - - - - P0

In table 42, “P0” - “P3” indicate the corresponding REs for the pilot signals for antenna ports 0-3, “-” indicates the REs for the data, “s” indicates the index of the OFDM (A) symbol in the base unit, and “SC” indicates the subcarrier index in the base unit.

FIG. 9A-9C illustrate an example in which pilot signals in 1Tx or 1 stream, in 2Tx or 2 flows, and in 4Tx or 4 streams are allocated when each base unit includes 4 subcarriers × 6 OFDM (A) symbols according to an embodiment of the present inventions. 4 × 6 base units can be sequentially allocated on the frequency axis or time axis.

As shown in FIG. 9A, RE for the pilot signals are arranged at the subcarrier index “0”, when s = 0, at the index of the subcarrier “3”, when s = 1, at the subcarrier index “0”, when s = 4, and at the subcarrier index “3” when s = 5. In another example, the REs for the pilot signals are located at the subcarrier index “3” when s = 0, at the subcarrier index “0”, when s = 1, at the subcarrier index “3”, when s = 4, and at the subcarrier index “0 "when s = 5. The RE locations for the pilot signals may cyclically shift along a time axis or a frequency axis. These pilot patterns are summarized in the following tables.

Table 43 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 P - - - P - SC = 1 - - - - - - SC = 2 - - - - - - SC = 3 - P - - - P

Table 44 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 - P - - - P SC = 1 - - - - - - SC = 2 - - - - - - SC = 3 P - - - P -

In Tables 43 and 44, “P” indicates RE for pilot signals, “-” indicates RE for data, “s” indicates an OFDM (A) symbol index in a base unit, and “SC” indicates a subcarrier index in a base unit.

These pilot patterns, in particular, are preferred for uplink transmission with a 1Tx antenna or in 1 stream for the following reasons.

First, the pilot patterns have a structure suitable for achieving an increase in the channel estimate through pilot amplification. In the case of the pilot patterns of FIG. 9A REs for the pilot signals are located in different OFDM (A) -characters on the time axis. Accordingly, when REs for pilot signals and REs for data are simultaneously transmitted, or only REs for pilot signals are transmitted, it is possible to improve channel estimation performance through pilot gain effects. Thus, a portion of the power for allocating RE for data can be allocated to REs for pilots, thereby achieving an increase in performance through amplification of pilots. However, if a certain number of pilots for one antenna are allocated to the same OFDM (A) symbol, the performance increase is not large, because the limited RE power for the data is distributed over the number of pilots. In particular, in the case of the pilot patterns of FIG. 9A, a portion of the power for allocating 3 REs for data in one OFDM (A) symbol is allocated REs for pilots, thereby achieving an increase in performance through pilot amplification. However, if 2 REs for pilots are included in a single OFDM (A) symbol, power for use in 2 REs is allocated 2 REs for pilots for data, and therefore, the performance gain through pilot amplification is small compared to when one RE for pilot signals is included in one OFDM (A) symbol. In particular, given that uplink power is limited, using one RE for the pilots in one OFDM (A) symbol helps in solving the problem of power balancing.

Secondly, it is possible to perform an effective channel estimation using the maximum possible amount of coherent time and coherent bandwidth. In particular, even when the delay spread in the channel is significant, the coherent bandwidth is 4 or more subcarriers, and thus the channel almost never changes or changes only slightly in 4 consecutive subcarriers. In addition, even when the terminal speed increases so that it uses a high-speed channel, the coherent time is 3 or more OFDM (A) characters, and thus the channel changes in units of 3 or more OFDM (A) characters (i.e. the channel almost never changes in 3 consecutive OFDM (A) -characters). In the pilot patterns of FIG. 9A, the pilot signals are arranged such that the diversity of the pilot signals is maximized on the frequency axis and the time axis. In particular, the pilot diversity is 3 subcarriers on the frequency axis and is 1 and 3 OFDM (A) -characters on the time axis. Accordingly, the maximum possible amount of coherent time and coherent bandwidth can be used, thereby increasing channel estimation performance.

As shown in FIG. 9B, in a 4 × 6 base unit, two REs for pilot signals in 2Tx or 2 streams are allocated for each antenna port, and the total amount of overhead when transmitting pilot signals is 16.67%. REs for the pilot signals for antenna port 0 are located at the subcarrier index “0” when s = 0, and at the index of the subcarrier “3” when s = 5. REs for the pilot signals for 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, the REs for the pilot signals for antenna port 0 are located at the subcarrier index “3” when s = 0, and at the index of the subcarrier “0” when s = 5. REs for the pilot signals for antenna port 1 are located at the subcarrier index “0” when s = 1, and at the index of the subcarrier “3” when s = 4. Antenna ports can switch among themselves. The RE locations for the pilot signals may cyclically shift along a time axis or a frequency axis. These pilot patterns are summarized in the following tables.

Table 45 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 P0 - - - P1 - SC = 1 - - - - - - SC = 2 - - - - - - SC = 3 - P1 - - - P0

Table 46 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 - P1 - - - P0 SC = 1 - - - - - - SC = 2 - - - - - - SC = 3 P0 - - - P1 -

In Tables 45 and 46, “P0” and “P1” indicate the corresponding REs for the pilot signals for antenna ports 0 and 1, “-” indicates the REs for the data, “s” indicates the index of the OFDM (A) symbol in the base unit, and “ SC "indicates the subcarrier index in the base unit.

As shown in FIG. 9C, in a 4 × 6 base unit, two REs for pilots in 4Tx or 4 streams are allocated for each antenna port, and the total amount of overhead when transmitting pilots is 33.34%. REs for the pilot signals for antenna port 0 are located at the subcarrier index “0” when s = 0, and at the index of the subcarrier “3” when s = 5. REs for the pilot signals for antenna port 1 are located at a subcarrier index of "3" when s = 1, and at a subcarrier index of "0" when s = 4. REs for the pilot signals for antenna port 2 are located at the subcarrier index “3” when s = 0, and at the subcarrier index “0” when s = 5. REs for the pilot signals for antenna port 3 are located at the subcarrier index “0” when s = 1, and at the index of the subcarrier “3” when s = 4. In another example, the REs for the pilot signals for antenna port 0 are located at the subcarrier index “3” when s = 0, and at the index of the subcarrier “0” when s = 5. REs for the pilot signals for antenna port 1 are located at the subcarrier index “0” when s = 1, and at the index of the subcarrier “3” when s = 4. REs for the pilot signals for antenna port 2 are located at the subcarrier index “0” when s = 0, and at the index of the subcarrier “3” when s = 5. REs for the pilot signals for antenna port 3 are located at a subcarrier index of "3" when s = 1, and at a subcarrier index of "0" when s = 4. Antenna ports can switch among themselves. The RE locations for the pilot signals may cyclically shift along a time axis or a frequency axis. These pilot patterns are summarized in the following tables.

Table 47 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 P0 P3 - - P1 P2 SC = 1 - - - - - - SC = 2 - - - - - - SC = 3 P2 P1 - - P3 P0

Table 48 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 P2 P1 - - P3 P0 SC = 1 - - - - - - SC = 2 - - - - - - SC = 3 P0 P3 - - P1 P2

In Tables 47 and 48, “P0” - “P3” indicate the corresponding REs for the pilot signals for antenna ports 0-3, “-” indicates the REs for the data, “s” indicates the OFDM (A) symbol index in the base unit, and “ SC "indicates the subcarrier index in the base unit.

FIG. 10 illustrates an example in which pilot signals in 1Tx or 1 stream are allocated when each base unit includes 4 subcarriers × 9 OFDM (A) symbols according to another embodiment of the present invention. Pilot signals are located at both ends of each 4 × 9 base unit on the frequency axis and are placed at the same time intervals. Here, the amount of overhead when transmitting pilot signals is 16.67%. 4 × 9 base units can be sequentially allocated on the frequency axis or time axis. Although FIG. 10 is illustrated for pilots for one antenna, the pilot pattern of FIG. 10 can also be applied to multiple antennas in a manner similar to that illustrated in FIG. 2-9.

In particular, the REs for the pilot signals are located at the subcarrier index “0” and at the subcarrier index “3” when s = 0, at the subcarrier index “0” and at the subcarrier index “3”, when s = 4, and at the subcarrier index “0” and with the subcarrier index “3” when s = 8. The RE locations for the pilot signals may cyclically shift along a time axis or a frequency axis. These pilot patterns are summarized in the following table.

Table 49 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 s = 6 s = 7 s = 8 SC = 0 P - - - P - - - P SC = 1 - - - - - - - - - SC = 2 - - - - - - - - - SC = 3 P - - - P - - - P

In table 49, “P” indicates RE for pilots, “-” indicates RE for data, “s” indicates an OFDM (A) symbol index in a base unit, and “SC” indicates a subcarrier index in a base unit.

FIG. 11 illustrates an example in which pilot signals in 1Tx or 1 stream are allocated when each base unit includes 4 subcarriers × 9 OFDM (A) symbols according to another embodiment of the present invention. The REs for the pilot signals are designed to be spaced at 2 OFDM (A) characters on the time axis in order to achieve greater reliability in the case of high speed than in the case of low speed. Here, the amount of overhead when transmitting pilot signals is 11.11%. 4 × 9 base units can be sequentially allocated on the frequency axis or time axis. Although FIG. 11 is illustrated for pilots for one antenna, the pilot pattern of FIG. 11 can also be applied to multiple antennas in a manner similar to that illustrated in FIG. 2-9.

In particular, the REs for the pilot signals are located at the subcarrier index “0”, when s = 1, at the subcarrier index “3”, when s = 3, at the subcarrier index “0”, when s = 5, and at the subcarrier index “3 "when s = 7. In another example, the REs for the pilot signals are located at the subcarrier index “3”, when s = 1, at the subcarrier index “0”, when s = 3, at the subcarrier index “3”, when s = 5, and at the subcarrier index “0 "when s = 7. The RE locations for the pilot signals may cyclically shift along a time axis or a frequency axis. These pilot patterns are summarized in the following table.

Table 50 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 s = 6 s = 7 s = 8 SC = 0 - P - - - P - - - SC = 1 - - - - - - - - - SC = 2 - - - - - - - - - SC = 3 - - - P - - - P -

Table 51 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 s = 6 s = 7 s = 8 SC = 0 - - - P - - - P - SC = 1 - - - - - - - - - SC = 2 - - - - - - - - SC = 3 - P - - P - - -

In Tables 50 and 51, “P” indicates RE for pilot signals, “-” indicates RE for data, “s” indicates an OFDM (A) symbol index in a base unit, and “SC” indicates a subcarrier index in a base unit.

FIG. 12 illustrates an example in which pilot signals in 1Tx or 1 stream are allocated when each base unit includes 4 subcarriers × 9 OFDM (A) symbols according to another embodiment of the present invention. The REs for the pilot signals are designed to be spaced at 2 OFDM (A) characters on the time axis in order to achieve greater reliability in the case of high speed than in the case of low speed. In addition, the pilot signals are designed so that they are placed in all positions on the frequency axis, thereby achieving greater reliability in the spread of delays in the channel. Here, the amount of overhead when transmitting pilot signals is 11.11%. 4 × 9 base units can be sequentially allocated on the frequency axis or time axis. Although FIG. 12 is illustrated for pilots for one antenna, the pilot pattern of FIG. 12 can also be applied to multiple antennas in a manner similar to that illustrated in FIG. 2-9.

In particular, the REs for the pilot signals are located at the subcarrier index “1”, when s = 1, at the subcarrier index “3”, when s = 3, at the subcarrier index “0”, when s = 5, and at the subcarrier index “2 "when s = 7. In another example, the REs for the pilot signals are located at the subcarrier index “2”, when s = 1, at the subcarrier index “0”, when s = 3, at the subcarrier index “3”, when s = 5, and at the subcarrier index “1 "when s = 7. The RE locations for the pilot signals may cyclically shift along a time axis or a frequency axis. These pilot patterns are summarized in the following table.

Table 52 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 s = 6 s = 7 s = 8 SC = 0 - - - - - P - - - SC = 1 - P - - - - - - - SC = 2 - - - - - - - P - SC = 3 - - - P - - - - -

Table 53 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 s = 6 s = 7 s = 8 SC = 0 - - - P - - - - - SC = 1 - - - - - - - P - SC = 2 - P - - - - - - - SC = 3 - - - - - P - - -

In Tables 52 and 53, “P” indicates RE for pilots, “-” indicates RE for data, “s” indicates an OFDM (A) symbol index in a base unit, and “SC” indicates a subcarrier index in a base unit.

FIG. 13 illustrates an example in which pilot signals in 1Tx or 1 stream are allocated when each base unit includes 4 subcarriers × 9 OFDM (A) symbols according to another embodiment of the present invention. The REs for the pilot signals are designed to be spaced at 2 OFDM (A) characters on the time axis in order to achieve greater reliability in the case of high speed than in the case of low speed. In addition, the pilot signals are designed so that they are placed in all positions on the frequency axis, thereby achieving greater reliability in the spread of delays in the channel. Here, the amount of overhead when transmitting pilot signals is 11.11%. 4 × 9 base units can be sequentially allocated on the frequency axis or time axis. Although FIG. 13 is illustrated for pilots for one antenna, the pilot pattern of FIG. 13 can also be applied to multiple antennas in a manner similar to that illustrated in FIG. 2-9.

In particular, the REs for the pilot signals are located at the subcarrier index “0”, when s = 0, at the subcarrier index “3”, when s = 3, at the subcarrier index “0”, when s = 5, and at the subcarrier index “3 "when s = 8. In another example, the REs for the pilot signals are located at the subcarrier index “3”, when s = 0, at the subcarrier index “0”, when s = 3, at the subcarrier index “3”, when s = 5, and at the subcarrier index “0 "when s = 8. The RE locations for the pilot signals may cyclically shift along a time axis or a frequency axis. These pilot patterns are summarized in the following table.

Table 54 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 s = 6 s = 7 s = 8 SC = 0 P - - - - P - - - SC = 1 - - - - - - - - - SC = 2 - - - - - - - - - SC = 3 - - - P - - - - P

Table 55 s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 s = 6 s = 7 s = 8 SC = 0 - - - P - - - - P SC = 1 - - - - - - - - - S02 - - - - - - - - - S03 P - - - - P - - -

In Tables 54 and 55, “P” indicates RE for pilot signals, “-” indicates RE for data, “s” indicates an OFDM (A) symbol index in a base unit, and “SC” indicates a subcarrier index in a base unit.

In order to measure the channel estimation capability of the above pilot patterns illustrated in accordance with the present invention, comparative simulations are performed for transmissions in one stream and two streams.

The pilot pattern used in the comparative simulation is shown in the following table:

Table 56 Single thread case The case of two threads Option Template Pilot signaling overhead Option Template Pilot signaling overhead 1-1

16.7% 2-1

16.7% 1-2

16.7% 2-2

25% 1-3

16.7% 2-3

33%

In Table 56, the numbers “1” and “2” in the pilot patterns indicate REs for the pilots for the first stream and the second stream, which correspond to “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. Pilot pattern 1-3 corresponds to two consecutively placed pilot patterns of FIG. 3A (table 7) in the time domain. The pilot pattern 2-1 corresponds to the pilot patterns of FIG. 8B (table 41). Pilot patterns 2-2 and 2-3 are pilot patterns indicated for comparison.

The simulation conditions are as follows:

Channel estimation: channel estimation based on two-dimensional minimum mean square error (two-dimensional MMSE)

- Receiver: 2 Rx MMSE receiver

- Channel model: eITU PedB channel 3 km / h, VehA 120 km / h, VehA 350 km / h

- Spacing between Tx antennas: 4 lambdas

- Spacing between Rx antennas: 0.5 lambda

- Pilot gain: 3 dB

- Noise limited

FIG. 14A-14C illustrate simulation results for channel estimation in the case of transmission in a single stream.

At PedB (pedestrian B) 3 km / h, the three pilot patterns 1-1, 1-2 and 1-3 show the same bandwidth. Pilot pattern 1-2 shows the smallest decrease in relative throughput loss performance (FIG. 14A).

At VehA (vehicle A) 120 km / h, the three pilot patterns 1-1, 1-2 and 1-3 show the same bandwidth. The pilot pattern 1-2 is clearly superior to others in relative throughput loss performance (FIG. 14B).

At VehA 350 km / h, the pilot pattern 1-2 is clearly superior to others in both communication bandwidth and relative throughput loss performance (FIG. 14C).

FIG. 15A-15C illustrate simulation results for channel estimation in the case of transmission in two streams.

In all conditions, PedB 3 km / h, VehA 120 km / h and VehA 350 km / h, the pilot signal pattern 2-1, of course, is superior to others in terms of both the throughput of the communication line and the relative throughput loss performance (Fig. 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 signal processor 1604, a transmitting circuit 1606, a receiving circuitry 1608, a plurality of antennas 1610, and a network interface 1612. A receiving circuitry 1608 receives a radio signal transmitted from a terminal through a plurality of antennas 1610. Preferably, a low noise amplifier and a filter (not shown) amplify the received signal and remove broadband interference from the signal. A down-conversion and digitization circuit (not shown) down-converts the filtered signal into a signal in the intermediate or fundamental frequency band and then digitizes the down-converted signal into one or more digital streams.

The baseband signal processor 1604 processes the digitally received signal to extract information bits or data bits from the received signal. This processing includes demodulation, decoding, error correction, etc. The baseband signal processor 1604 generally includes one or more digital signal processors (DSPs). After that, the received information is transmitted via a wireless network via a network interface or transmitted to another terminal serviced by a base station. The network interface 1612 communicates with a circuit-switched network, which is part of a wireless network that can connect to a public switched telephone network (PSTN) and a central network controller.

On the transmitting side, the baseband signal processor 1604 receives digital data, which may represent speech, data, or control information, from the network interface 1612 and encodes the data for transmission under the control of the control system 1602. The encoded data is input into the transmit circuit 1606. The transmit circuit 1606 modulates the encoded data using a carrier having the desired transmit frequency (s). An amplifier (not shown) amplifies the modulated carrier signal to a level suitable for transmission. The amplified signal is transmitted to 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 signal processor 1704, a transmit circuit 1706, a receive circuit 1708, multiple antennas 1710, and a user interface circuit 1712. A receiving circuit 1708 receives a radio signal including information from one or more base stations via a plurality of antennas 1710. Preferably, a low noise amplifier and filter (not shown) amplify the received signal and remove broadband interference from the signal. After that, the down-conversion and digitization circuit (not shown) down-converts the filtered signal into a signal in the intermediate or fundamental frequency band and then digitizes the down-converted signal into one or more digital streams. The baseband signal processor 1704 processes the digitally received signal to extract information bits or data bits from the received signal. This processing includes operations such as demodulation, decoding, and error correction. The baseband signal processor 1704 generally includes one or more digital signal processors (DSPs) and specialized integrated circuits (ASICs).

On the transmitting side, the baseband signal processor 1704 receives digital data, which may represent speech, data, or control information, from the user interface circuit 1712 and encodes the data for transmission under the control of the control system 1702. The encoded data is input into the transmission circuit 1706. The transmission circuit 1706 modulates the encoded data using a carrier having the desired transmission frequency (s). An amplifier (not shown) amplifies the modulated carrier signal to a level suitable for transmission. The amplified signal is transmitted to multiple antennas 1710.

FIG. 18 illustrates a block diagram of a transmitter that may be applied to an embodiment of the present invention.

Although the transmitter structure of FIG. 18 is described with respect to a base station, those skilled in the art will appreciate that the illustrated structure can be used for both uplink and downlink transmissions. The illustrated transmission structure is intended to represent, without limitation, multiple 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 the terminal at the base station. At the base station, a data scrambling module 1804 scrambles the scheduled data, which is a bitstream, thereby reducing the ratio of peak power to average power associated with the data. CRC add-on module 1806 then determines and adds a cyclic redundancy check (CRC) checksum for the scrambled data to the scrambled data. Then, the channel encoder module 1808 performs channel coding for the data to enable the terminal to perform data error recovery and correction. Channel coding provides the ability to effectively add redundancy to data. Channel encoder module 1808 may utilize turbo coding techniques.

Then, the display unit 1814 systematically maps the processed data bits to the corresponding symbol based on the selected modulation mode in the fundamental band. Here the quadrature amplitude modulation (QAM) or quadrature phase shift keying (QPSK) mode can be used. A group of bits is mapped to a symbol representing a position in the amplitude-phase constellation. Then, the space-time code (STC) encoder module 1818 processes the symbol block. In particular, the STC encoder module 1818 processes the symbol according to the selected STC encoding mode and provides the same number N of pins as the number of multiple base station antennas 1610. Each of the plurality of IFFT processing units 1820 performs the inverse Fourier transform for the symbol stream output from the STC encoder unit 1818. Then, each of the plurality of prefix and RS insertion units 1822 inserts a cyclic prefix (CP) and RS into the inverse Fourier transform signal. Although RS is illustrated to be inserted after the IFFT is performed, RS can also be inserted before the IFFT. In this case, a separate RS insertion module may be added before the IFFT processing modules 1820. Then, each of the plurality of frequency upconverting (DUC) and digital to analog (D / A) conversion units 1824 upconverts the processed signal from the prefix and RS insertion unit 1822 to an intermediate frequency in the digital domain and then converts the upconverted signal to analog signal. Then, the analog signals created in this way are simultaneously modulated, amplified and transmitted through a plurality of RF modules 1826 and a plurality of antennas 1610.

FIG. 19 is a block diagram of a receiver that can be applied to an embodiment of the present invention.

Although the receiver structure of FIG. 19 is described with respect to a terminal, those skilled in the art will appreciate that the illustrated structure can be used for both uplink and downlink transmissions. When a transmitted signal is received by a plurality of antennas 1710, each signal is demodulated and amplified through a corresponding RF module 1902. For convenience, only one of the plurality of reception paths is illustrated in FIG. 19. The analog-to-digital (A / D) conversion and digital down-conversion (DCC) module 1904 then converts the analog signal to a digital signal for digital processing and down-converts the digital signal. A digital signal may be provided and used in the automatic gain control (AGC) module 1906 to adjust the gain of the amplifier of the RF module 1902 based on the level of the received signal.

A digital signal is also provided to synchronization module 1908. Synchronization module 1908 may include a coarse synchronization module 1910 that performs coarse synchronization, an accurate synchronization module 1912 that performs accurate synchronization, and a synchronization and Doppler frequency shift estimator that estimates frequency shift or Doppler effects value. The signal output from the synchronization module 1908 is provided to the frame synchronization module 1914 and the synchronization correction and Doppler frequency shift module 1918. The prefix removal module 1916 removes the CP from the synchronized frame.

Then, the FFT module 1922 performs Fourier transform on the data with the remote CP. Then, the RS extraction module 1930 extracts the spread of RS signals in the frame and provides the RS signal to the channel estimator 1928. Then, the channel recovery module 1926 restores the radio channel using the channel estimation result. The channel estimate provides sufficient channel response information to enable the STC decoder 1932 to decode the symbol according to the STC encoding method used in the base station and restore the estimate corresponding to the transmitted bits. The symbol obtained from the received signal and the channel estimation result of each receive path are provided to the STC decoder 1932. The STC decoder 1932 then performs STC decoding for each receive path to recover the received symbol. The STC decoder 1932 may implement maximum likelihood (MLD) decoding for transmission in bitwise blocks. The output of the STC decoder 1932 may be a log-likelihood ratio (LLR) for each transmitted bit. The symbol deinterleaving module 1934 then places the STC-decoded symbols in the original order. Then, the reverse mapping unit 1936 maps the symbols back to the bitstream, and the reverse bit interleaving unit 1938 deinterleaves the bitstream. The bit rate mismatch unit 1940 then processes and provides the de-interleaved bit stream to the channel decoder unit 1942 to recover the scrambled data and the CRC checksum. Here, the channel decoder module 1942 may use turbo decoding.

The CRC module 1944 then removes the CRC checksum and checks the scrambled data according to a conventional method. The descrambling module 1946 then restores the data after the CRC control to the original data 1948.

The above described embodiments are provided by combining the components and features of the present invention in specific forms. The components or features of the present invention should be considered optional unless otherwise indicated. Components or features may be implemented without combining with other components or features. Embodiments of the present invention may also be provided by combining some of the components and / or features. The order of operations described above in embodiments of the present invention may vary. Some components or features of one embodiment may be included in another embodiment, or may be replaced by corresponding components or features of another embodiment. It should be obvious that claims that are not explicitly dependent on each other may be combined to provide an embodiment, or new claims may be added through a change after this application has been filed.

Embodiments of the present invention are described with a focus on the relationship of data exchange between a mobile station (MS) and a base station (BS). Specific operations, which are described as being performed by the BS, can also be performed by the upper node as necessary. Thus, it will be apparent to those skilled in the art that a BS or any other network node can perform various operations to communicate with terminals in a network including a certain number of network nodes including a BS. The term "base station (BS)" may be replaced by another term, for example, "fixed station", "node B", "advanced node B (eNB)" or "access point". The term “mobile station (MS)” may also be replaced by another term, for example, “user equipment (UE)”, “terminal” or “mobile subscriber station (MSS)”.

Embodiments of the present invention may be implemented by hardware, firmware, software, or any combination of the above. If the present invention is implemented by hardware, an embodiment of the present invention can be implemented by one or more specialized integrated circuits (ASIC), digital signal processors (DSP), digital signal processing devices (DSPD), programmable logic devices (PLD), Field Programmable Gate Arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, etc.

In the event that the present invention is implemented by firmware or software, embodiments of the present invention may be implemented in the form of modules, processes, functions, and the like that perform the features or operations described above. The program code may be stored in a memory device so as to be executed by a processor. The storage device may be located inside or outside the processor and can communicate with the processor through a variety of known means.

Specialists in the art should take into account that the present invention may be practiced in specific forms other than those set forth herein without departing from the gist of the present invention. The above description, therefore, should be considered in all aspects as illustrative and not restrictive. The scope of the invention should be determined by reasonably interpreting the appended claims, and all changes within the scope of the equivalence of the invention are intended to be encompassed within the scope of the invention.

As is apparent from the above description, the present invention provides a base unit and pilot structure that can reduce the amount of overhead when transmitting uplink pilots and also ensures excellent channel estimation. The structure of the base units and pilot signals according to the present invention reduces the amount of overhead when transmitting the pilot signals of the OFDM (A) system, thereby increasing system performance and preserves universal time-frequency diversity, thereby guaranteeing channel estimation performance, and can be applied to the base stations, terminal, etc. that are compatible with IEEE 802.16m.

Claims (15)

1. A method for transmitting a base unit in an uplink by a mobile station (MS) in an orthogonal frequency division multiple access (OFDMA) wireless communication system, the method comprises the steps of:
- form a basic unit, the size of which is 4 subcarriers of 6 OFDMA symbols, the basic unit contains a lot of resource elements (RE) for pilot signals and data;
- configure REs for the pilot signals for multiple antennas in the base unit with 3 subcarrier intervals on the frequency axis and 5 OFDMA symbol intervals on the time axis; and
- transmit the base unit in the uplink,
- wherein RE is a time-frequency resource specified by one OFDMA symbol and one subcarrier,
- while RE for the pilot signals and data is configured in the basic unit, as in Table 2 of the patterns, expressed as follows:
Table 2 Patterns s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 P0 - - - - P1 SC = 1 - - - - - - SC = 2 - - - - - - SC = 3 P1 - - - - P0
- where "P0" and "P1" indicate the corresponding REs for the pilot signals for antenna ports 0 and 1,
"-" indicates RE for data,
"s" indicates the index of the OFDMA symbol, and
"SC" indicates the subcarrier index. 2. The method according to claim 1, in which the base unit is a mosaic fragment in the uplink. 3. The method according to claim 1, in which the base unit is a mosaic fragment based on the partial use of the subchannel (PUSC) in the uplink. 4. The method according to claim 1, in which a certain number of base units forms a larger unit of resources. 5. The method according to claim 4, in which the base units forming a larger unit of resources are adjacent in the frequency domain. 6. The method according to claim 4, in which the base units forming a larger unit of resources are distributed in the frequency domain. 7. The method according to claim 1, in which the antenna port 0 and antenna port 1 are replaced by each other. 8. The method of claim 1, wherein the RE locations for the pilot signals are cyclically shifted in the frequency domain or in the time domain. 9. The method of claim 1, wherein the REs for the pilot signals are power amplified with a RE power for data in the same OFDMA symbol. 10. The method of claim 1, further comprising mapping the pilot and data symbols to respective REs for the pilot and data, respectively. 11. The method according to claim 1, in which the RE for the pilot signals are used for dedicated pilot signals. 12. The method of claim 1, wherein the transmit diversity scheme or spatial multiplexing (SM) is independently applied to each base unit. 13. The method of claim 12, wherein the transmit diversity scheme includes a space time block code (STBC), a space frequency block code (SFBC), cyclic delay diversity (CDD), or any combination of the above. 14. A mobile station (MS) configured to transmit an uplink base unit in an orthogonal frequency division multiple access (OFDMA) wireless communication system, the MS comprises:
- an unmodulated signal processor for processing digital signals; and
- a transmitting circuit for receiving unmodulated signals from an unmodulated signal processor and transmitting radio signals in an uplink through multiple antennas,
- while the processor of unmodulated signals forms a basic unit, the size of which is 4 subcarriers of 6 OFDMA symbols, the basic unit contains a lot of resource elements (RE) for pilot signals and data,
- while the processor of unmodulated signals configures the RE for the pilot signals for multiple antennas in the base unit with intervals of 3 subcarriers on the frequency axis and at intervals of 5 OFDMA symbols on the time axis,
- wherein RE is a time-frequency resource defined by one OFDMA symbol and one subcarrier, and
- while RE for the pilot signals and data is configured in the basic unit, as in Table 2 of the patterns, expressed as follows:
Table 2 Patterns s = 0 s = 1 s = 2 s = 3 s = 4 s = 5 SC = 0 P0 - - - - P1 SC = 1 - - - - - - SC = 2 - - - - - - SC = 3 P1 - - - - P0
- where "P0" and "P1" indicate the corresponding REs for the pilot signals for antenna ports 0 and 1,
"-" indicates RE for data,
"s" indicates the index of the OFDMA symbol, and
"SC" indicates the subcarrier index. 15. MS according to 14, in which the base unit is a mosaic fragment in the uplink.

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