METHOD AND APPARATUS FOR DATA CODED SYMBOL MAPPING BASED ON CHANNEL ESTIMATION IN A FREQUENCY DIVISION MULTIPLE ACCESS SYSTEM

[Technical Field]

The present invention relates to a wireless communication system employing a frequency division multiple access scheme, including an Orthogonal Frequency Division Multiple Access (hereinafter referred to as "OFDMA") wireless communication system and a Single Carrier Frequency Division Multiple Access (hereinafter referred to as "SC-FDMA") wireless communication system, and more particularly to a method and an apparatus for mapping coded symbols according to channel estimation performance and transmitting the mapped symbols.

[Background Art]

The UMTS (Universal Mobile Telecommunication Service) system is a 3 ^rd generation asynchronous mobile communication system which is based on European mobile communication systems, that is, the GSM (Global System for Mobile Communications) and the GPRS (General Packet Radio Services), and employs a wideband Code Division Multiple Access (hereinafter referred to as "CDMA") scheme.

The 3GPP (3 ^rd Generation Partnership Project) responsible for standardization of the UMTS is currently discussing a Long Term Evolution (hereinafter referred to as "LTE") system as the next generation mobile communication system in the UMTS. The LTE system is technology for providing high-speed packet-based communication at a speed of lOOMbps.

Further, in recent mobile communication systems, research has been actively conducted on an Orthogonal Frequency Division Multiplexing (hereinafter referred to as "OFDM") scheme which is useful for high-speed data transmission over a radio channel or an SC-FDMA scheme which is a transmission scheme similar to the OFDM scheme.

[Disclosure] [Technical Problem]

In the above-mentioned next generation mobile communication systems meant to provide high-speed packet data by using the OFDM scheme or the SC- FDMA scheme, there is a need to provide a concrete transmission method for ensuring the reliability of transmission data.

Further, it is necessary to propose a more concrete way to allocate highspeed data, that is, coded symbols to corresponding frequencies in a wireless communication system. Accordingly, the present invention has been made to solve the above- mentioned problems occurring in the prior art, and the present invention provides a method and an apparatus for mapping symbols, into which information data is coded, to radio resources and transmitting the mapped symbols in a wireless communication system. Further, the present invention provides a reception method and a reception apparatus for demapping coded symbols received over radio resources and decoding the demapped symbols into information data in a wireless communication system.

Further, the present invention provides a method and an apparatus for mapping symbols, into which information data is coded, to radio resources in order from a radio resource having the highest channel estimation performance to a radio resource having the lowest channel estimation performance and transmitting the mapped symbols in a wireless communication system using a time division multiplexing pilot. Further, the present invention provides a reception method and a reception apparatus for demapping transmitted coded symbols in order of how close radio resources, to which the coded symbols are mapped, are to a time division multiplexing pilot and decoding the demapped symbols in a wireless communication system using the time division multiplexing pilot. Further, the present invention provides a method and an apparatus for improving data transmission performance in a wireless communication system using a frequency division multiplexing pilot or a time division multiplexing pilot

by transmitting a relatively more important data symbol over a resource located in such a manner as to have higher channel estimation performance and transmitting a relatively less important data symbol over a resource located in such a manner as to have lower channel estimation performance, in consideration of the fact that the channel estimation performances of resources carrying packet data other than the pilot vary with the position of a resource carrying the pilot.

[Technical solution]

In accordance with an aspect of the present invention, there is provided a method for mapping coded data symbols based on channel estimation in a frequency division multiple access system, the method including the steps of: coding packet information data and carrying out rate matching to thereby output coded symbols divided into systematic bits and parity bits; interleaving the systematic bits and the parity bits respectively to thereby generate a bit stream arranged in order of the systematic bits and the parity bits; mapping the generated bit stream onto a subframe of a radio frame in order starting from a long block which is located in such a manner as to have highest channel estimation performance, under control of a mapping sequence control signal; and multiplexing the mapped bit stream with a coded Transport Format (TF) control information signal after the mapping, and transmitting the multiplexed bit stream and TF control information signal to a receiver through a transmitter unit.

In accordance with another aspect of the present invention, there is provided a method for receiving coded data symbols based on channel estimation in a frequency division multiple access system, the method including the steps of: demultiplexing a received radio resource signal into a TF control-related signal and a packet data-related signal, and then decoding the TF control-related signal into TF control information; demultiplexing the packet data-related signal based on control information regarding a coding rate and mapping sequence control information, which are derived from the TF control information, to thereby separately output systematic bits and parity bits mapped onto a subframe of a radio frame in order from a long block having highest channel estimation performance to a long block having lowest channel estimation performance; and

deinterleaving the output systematic bits and the parity bits respectively and then performing channel decoding to thereby acquire packet information data.

[Advantageous Effects] According to the present invention, the following advantageous effects can be obtained:

In a system using frequency division multiplexing or time division multiplexing, when a pilot is carried by a specific radio resource allocated thereto, the positions of radio resources to which packet data is allocated can be determined in consideration of the reliability of the packet data. That is, mapping of radio resources carrying packet data can be variably conducted.

Important coded symbols, that is, systematic bits, are mapped to radio resources ensuring the reliability of channel estimation performance, and thus the overall transmission performance can be improved. Relatively less important coded symbols, that is, parity bits, are mapped to radio resources which may be neglected to some extent in terms of the reliability of channel estimation performance, so that limited radio resources can be efficiently used.

The reliability of important coded symbols, that is, the systematic bits, is ensured, and thus the channel estimation performance for the whole transmission packet data can also be ensured.

[Brief Description of the Drawings]

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a block diagram illustrating the structure of a transmitter in an OFDM system to which the present invention is applied;

FIG. 2 is a block diagram illustrating the structure of a transmitter in an SC-FDMA system to which the present invention is applied;

FIG. 3 is a block diagram illustrating in detail a mapping operation in the SC-FDMA system to which the present invention is applied;

FIG. 4 is a view illustrating an operation of frequency division multiplexing a pilot signal according to the present invention;

FIG. 5 is a view illustrating an operation of time division multiplexing a pilot signal according to the present invention; FIG. 6 is a view illustrating the formats of an uplink transmission frame and a subframe in an LTE system according to the present invention;

FIG. 7 is a flowchart illustrating the operation of a transmitter according to an exemplary embodiment of the present invention;

FIG. 8 is a view illustrating the structure of a transmitter according to an exemplary embodiment of the present invention;

FIG. 9 is a flowchart illustrating the operation of a receiver according to an exemplary embodiment of the present invention; and

FIG. 10 is a view illustrating the structure of a receiver according to an exemplary embodiment of the present invention.

[Best Mode] [Mode for Invention]

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same elements will be designated by the same reference numerals although they are shown in different drawings. Further, in the following description, only parts necessary for understanding operations of the present invention will described, and a detailed description of known functions and configurations incorporated herein will be omitted so as not to make the subject matter of the present invention rather unclear.

The present invention provides a way to map radio resources in such a manner as to ensure the reliability of packet data to be transmitted, that is, coded symbols, in a wireless communication system to which frequency division multiplexing and time division multiplexing are applied. Further, the present invention provides a way to map packet data to radio resources while varying positions of the radio resources according to a pilot resource, the position of which is determined, in a wireless communication

system using a frequency division multiplexing pilot or a time division multiplexing pilot.

Further, the present invention provides a way to map systematic bits and parity bits to radio resources having different reliabilities in consideration of the position of a radio resource allocated to a pilot in a wireless communication system using a frequency division multiplexing pilot or a time division multiplexing pilot.

Further, the present invention provides a way to sequentially map systematic bits and parity bits in order from a radio resource having the highest channel estimation performance to a radio resource having the lowest channel estimation performance in consideration of the fact that channel estimation performance varies with the position of a radio resource allocated to a pilot.

In the following description, by way of example, a case where time division multiplexing is conducted and a pilot is transmitted will be described based on an LTE system under standardization by the 3GPP which is the standardization organization for 3 ^rd generation mobile communication.

The LTE system uses a time division multiplexing pilot for uplink transmission in a SC-FDMA scheme.

FIG. 1 schematically illustrates the structure of a transmitter in an OFDM system to which the present invention is applied.

Referring to FIG. 1, the OFDM transmitter 101 includes an encoder 101, a modulator 102, a serial -to-parallel converter 102, an Inverse Fast Fourier Transform (hereinafter referred to as "IFFT") block 104, a parallel-to-serial converter 105 and a Cyclic Prefix (hereinafter referred to as "CP") inserter 106. A given stream of information bits is input into the encoder 101, that is, a channel encoding block, which in turn conducts channel encoding. In general, a convolution encoder, a turbo encoder, an LDPC (Low density Parity Check) or a zigzag encoder is used as the encoder 101.

The modulator 102 conducts modulation such as QPSK (Quadrature Phase Shift Keying), 8PSK, 16QAM (16-array Quadrature Amplitude Modulation), 64QAM, 256QAM, etc.

Although not illustrated in FIG. 1, a rate matching block for conducting

repetition and puncturing may be additionally interposed between the encoder 101 and the modulator 102. This is intended to ensure the transfer rate of highspeed packet data,

A serial output of the modulator 102 is input into the serial-to-parallel converter 103, which in turn converts the input serial data into parallel data and outputs the converted parallel data.

Output data of the serial-to-parallel converter 103 is input into the IFFT block 104, which in turn conducts IFFT operation on the input data. The IFFT block 104 converts the frequency-domain input data into time-domain output data. The output data of the IFFT block 104 is converted by the parallel-to- serial converter 105, and the CP inserter 106 inserts a CP into output data of the parallel-to-serial converter 105.

In the OFDM system, there is a problem in that the Peak to Average Power Ratio (hereinafter referred to as "PAPR") becomes larger as received input data is subjected to processing in the frequency domain and is transformed into the time domain by the IFFT block 104.

The PAPR is one of the important factors which must be considered in uplink transmission. If the PAPR becomes larger, cell coverage decrease and signal power required by a terminal increases accordingly. That is, in uplink transmission, an effort needs to be made to preferentially reduce the PAPR.

Therefore, in OFDM-based uplink transmission, multiple access of the uplink transmission may be used in a modified form from that of a common OFDM scheme. That is, this modified multiple access scheme proposes a way to efficiently reduce the PAPR by enabling data processing (channel encoding, modulation, etc.) to be conducted in the time domain rather than the frequency domain.

FIG. 2 illustrates the structure of a transmitter in an SC-FDMA system that is another example of an uplink transmission scheme to which the present invention is applied. Referring to FIG. 2, the SC-FDMA transmitter includes an encoder 201, a modulator 202, a serial-to-parallel converter 203, a Fast Fourier Transform (hereinafter referred to as "FFT") block 204, a mapper 205, an IFFT block 206, a

parallel-to-serial converter 207 and a CP inserter 208.

A given stream of information bits is input into the encoder 201 , which in turn conducts channel encoding. The modulator 202 conducts modulation such as QPSK, 8PSK, 16QAM, 64QAM, 256QAM, etc. Of course, a rate matching block may be additionally interposed between the encoder 201 and the modulator 202. A serial output of the modulator 202 is input into the serial-to-parallel converter 203, which in turn converts the input serial data into parallel data.

Output data of the serial-to-parallel converter 203 is input into the FFT block 204, which in turn conducts an FFT operation on the input data. The mapper 205 maps output data of the FFT block 204 to an input of the IFFT block 206. The IFFT block 206 conducts an IFFT operation on output data of the mapper 205. Output data of the IFFT block 206 is converted by the parallel-to- serial converter 207, and the CP inserter 208 inserts a CP into output data of the parallel-to-serial converter 207. FIG. 3 illustrates in detail the mapper in FIG. 2.

Referring to FIG. 3, channel coded or modulated data symbols 301 are input into the FFT block 302. An output of the FFT block 302 is in turn input into the IFFT block 304. At this point of time, the mapper 303 functions to map the output data of the FFT block 302 to the input data of the IFFT block 304. The mapper 303 maps frequency-domain data, converted through the

FFT block 302, to input points of the IFFT block 304 in such a manner that the frequency-domain data can be carried in sub-carriers.

When the output symbols of the FFT block 302 are mapped in sequence to the input points of the IFFT block 304 in the course of the mapping, consecutive sub-carriers on the frequency domain are used. Such a mapping scheme is called LFDMA (Localized Frequency Division Multiple Access).

When the output symbols of the FFT block 302 are mapped to the input points of the IFFT block 304 at regular intervals, equidistant sub-carriers on the frequency domain are used. Such a mapping scheme is called IFDMA (Interleaved Frequency Division Multiple Access) or DFDMA (Distributed

Frequency Division Multiple Access).

FIGS. 2 and 3 illustrate a method of implementing SC-FDMA technology

in the frequency domain, and various methods, including a method of implementing the SC-FDMA technology in the time domain, may be applied for implementing the SC-FDMA technology.

As mentioned above, the OFDM or SC-FDMA system can be said to be a system in which radio resources are available in a two-dimensional domain, that is, in the time domain and the frequency domain.

That is, information (data) can be transmitted using resources corresponding to the time and frequency domains, and a pilot, which is information required for channel estimation with respect to information transmission, must also be transmitted within the time-frequency domain.

Time division multiplexing and frequency division multiplexing are used as a typical method of transmitting a pilot, and the method of transmitting a pilot will be described with reference to FIGS. 4 and 5.

FIG. 4 illustrates an operation of frequency division multiplexing a pilot according to the present invention.

Referring to FIG. 4, reference numeral "401" designates the time domain (axis), and reference numeral "402" designates the frequency domain (or sub- carrier domain). Thus, radio resources for transmitting transmission information can be a two-dimensional time-frequency domain. Among the radio resources in FIG. 4, shaded portions designated by reference numerals "403", "404", "405", "406", "407" and "408" are radio resources for carrying a pilot. When the remaining portions designated by reference numeral "409" are radio resources for carrying information other than the pilot, it can be said that a Frequency Division Multiplexing pilot (FDM pilot) is used.

In FIG. 4, a time axis duration 420 represents the minimum transmission unit for information transmission, and the FDM pilot maintains its position at the same frequency (this means the same sub-carrier) during the minimum transmission unit duration 420. However, the position of a frequency at which a pilot is transmitted may vary with the minimum transmission unit duration.

A method of transmitting a pilot only at specific frequencies during the minimum transmission unit duration while maintaining equidistance between the

specific frequencies, as illustrated in FIG. 4, can be referred to as an FDM pilot method. Reference will now be made to how channel estimation is done when the FDM pilot is used, in connection with resources existing within a circle 410.

On the right side of FIG. 4, an enlarged view of the circle area 410 including time-frequency resources is depicted. In this enlarged view, the FDM pilot is transmitted at frequencies designated by reference numerals "411" and "412", respectively. Since a channel estimation value of the FDM pilot differs according to respective frequencies at which the pilot is transmitted, that is, according to respective pilot frequencies, a channel estimation value for a frequency at which the pilot is not located must be sought using the pilot transmitted at different pilot frequencies. For example, for a frequency 413 or 414 adjacent to the pilot frequency 411 or 412, a channel estimation value thereat can be assumed to be the same as that at the pilot frequency 411 or 412.

However, as a frequency moves farther and farther away from the pilot frequencies 411, 412, an actual channel value becomes more and more different from its channel estimation value obtained through the pilot. Nevertheless, in order to evaluate channel estimation values for resources in which all frequencies are located, a channel estimation value in a frequency range, over which the pilot is not transmitted, is sought through a calculation technique, such as interpolation, by using the channel estimation values at the pilot frequencies 411, 412.

That is, channel estimation values for frequencies 415, 416, 417 are sought using an equation whose variables are the channels estimation values at the pilot frequencies 411, 412.

Of course, channel estimation values for the frequencies 413, 414 adjacent to the pilot frequencies 411, 412 may also be sought using the equation whose variables are the channels estimation values at the pilot frequencies 411, 412.

FIG. 5 illustrates an example of a method of time division multiplexing a pilot signal according to the present invention. Referring to FIG. 5, reference numeral "501" designates the time domain, and reference numeral "502" designates the frequency domain. Thus, radio resources for transmitting transmission information can be a two-dimensional

time-frequency domain.

Among the radio resources in FIG. 4, portions designated by reference numerals "503", "504", "505", "506", "507" and "508" are radio resources for carrying a pilot. The remaining portions designated by reference numeral "509" carry information other than the pilot, and thus it can be said that a Time Division

Multiplexing pilot (TDM pilot) is used.

A method of transmitting a pilot only at specific time resources while maintaining equidistance between the specific time resources in this way can be referred to as a TDM pilot method. Reference will now be made to how channel estimation is done when the TDM pilot is used, in connection with resources existing within a circle 510.

On the upper side of FIG. 5, an enlarged view of the circle area 510 including time-frequency resources is depicted. In this enlarged view, the TDM pilot is transmitted at times designated by reference numerals "511" and "512", respectively. Since a channel estimation value of the TDM pilot differs according to respective times at which the pilot is transmitted, that is, respective pilot times, a channel estimation value for a time at which the pilot is not located must be sought using the pilot transmitted at different pilot times.

For example, for a time 513 or 514 adjacent to the pilot time 511 or 512, a channel estimation value thereat can be assumed to be the same as that at the pilot time 511 or 512. However, as a time moves farther and farther away from the pilot times 511, 512, an actual channel value becomes more and more different from its channel estimation value obtained through the pilot.

Nevertheless, in order to evaluate channel estimation values corresponding to all time resources, a channel estimation value in a time range, over which the pilot is not transmitted, is sought through a calculation technique, such as interpolation, by using the channel estimation values at the pilot times 511, 512. That is, channel estimation values for times 515, 516, 517 are sought using an equation whose variables are the channels estimation values at the pilot times 511, 512. Of course, channel estimation values for the times 513,

514 adjacent to the pilot times 511, 512 may also be sought using the equation whose variables are the channels estimation values at the pilot times 511, 512.

As mentioned above, when the FDM pilot or TDM pilot of the prior art is used, a channel estimation value for a frequency or a time resource located between pilot frequencies or pilot times is inferred from channel estimation values sought at the pilot resources (pilot frequencies or pilot times), but an actual channel value may greatly differ from the inferred channel estimation value, depending on how far the frequency or the time resource is away from the pilot resources.

Therefore, there is a difference in the error reliability of data according to the distance between a pilot resource and a resource in which a coded data symbol is located. Since relatively important data may exist in the data symbol, there is a problem in that the overall transmission performance deteriorates when the resource containing the important data is far away from the pilot resource and thus the error reliability of the important data is lowered.

Thereupon, the present invention proposes a way to map coded symbols to frequencies while ensuring the reliability of transmission symbols.

FIG. 6 illustrates the formats of an uplink transmission frame and a subframe in an LTE system according to the present invention.

Referring to FIG. 6, reference numeral "601" designates a radio frame which is the uplink transmission unit, and the radio frame 601 is defined by a length of 10ms.

One radio frame consists of 20 subframes 602, and one subframe 602 has a length of 0.5ms. Further, one subframe 602 consists of 6 long blocks (LB) and two short blocks (SB), and a CP is placed in front of each block. Reference numerals "603", "605", "606", "607", "608" and "610" designate long blocks, and reference numerals "604" and "609" designate short blocks.

The short blocks 604, 609 are resource regions for carrying a pilot. Such an LTE uplink system applies time division multiplexing in which only limited short blocks carry the pilot at regular time intervals.

In the LTE uplink system, two short blocks 604, 609 carry the pilot, and six long blocks 603, 605, 606, 607, 608, 610 carry packet data, that is, information data. In general, channel estimation performance for transmission data differs according to the positions of long blocks allocated to the data. That

is, a long block, which is located closer to the position of a pilot resource in terms of time, has better channel estimation performance. Further, when a plurality of pilots exist, a long block located between the pilots has the best channel estimation performance. For example, long block #3 606 and long block #4 607 are farther away from the positions of pilots than long block #1 603 and long block #6 610, but they have better channel estimation performance because they are located between the pilots.

Therefore, in an exemplary embodiment of the present invention, it may be assumed that long block #2 and long block #5 have the best channel estimation performance, long block #3 and long block #4 have the second best channel estimation performance, and long block #1 and long block #6 have the third best channel estimation performance.

Consequently, in this embodiment of the present invention, systematic bits whose reliability must be best ensured in a coded output are preferentially mapped to long block #2 and long block #5. If systematic bits still exist (remain), these systematic bits are mapped to long block #3 and long block #4. Next, the remaining systematic bits are sequentially mapped to long block #1 and long bock #6. That is, systematic bits requiring ensured high reliability are preferentially mapped to long blocks having high channel estimation performance, and parity bits are mapped to the remaining long blocks.

The order in which systematic bits are mapped may vary according to the types of channels or channel estimation techniques, and thus the order in which systematic bits are mapped, that is, the order of long blocks to which systematic bits are mapped, may be transposed. Accordingly, the present invention provides a method of mapping coded symbols when a TDM pilot is used in a system employing FDM scheme, the method including the steps of: determining the position of a resource for carrying the pilot; comparing the channel estimation performances of resources not carrying the pilot; separating important data symbols from the coded symbols; mapping the important data symbols to resources which are located in such a manner as to have relatively high channel estimation performance; and determining where the mapped data symbols are located and receiving the data

symbols based thereon.

In other words, the present invention provides a mapping method in which once the position of a pilot resource is determined, the positions of resources to which packet data is mapped are differently set depending on channel estimation performances of the resources, and then the packet data is mapped to the resources according to the set positions. Reference will now be made to an operation in which a transmitter allocates resources while ensuring the reliability of transmission data according to an exemplary embodiment of the present invention, with reference to FIG. 7. FIG. 7 is a flowchart illustrating the operation of a transmitter according to an exemplary embodiment of the present invention.

Referring to FIG. 7, if the transmitter's operation starts with step 701, the transmitter stores packet data (information data), which is to be transmitted, in step 702. In step 703, the transmitter conducts encoding for the information data according to a predetermined encoding scheme.

In order to transmit the information data, an encoder is used in the present invention, and various types of encoders including a turbo encoder, an LDPC encoder, a zigzag encoder and so forth may be used as the encoder. Such an encoder is characterized in that if information data is input therein, systematic bits corresponding to the same bit stream as the information data and parity bits corresponding to a bit stream related to the information data are output as output information. However, data encoding is not the gist of the present invention, and the present invention is not limited to these encoders which are mentioned merely by way of example. According as encoding for the input information data is conducted in step

703, systematic bits and parity bits are dividedly output, and the transmitter separately stores the systematic bits and the parity bits in step 704.

Among the systematic bits and the parity bits, importance is attached to the systematic bits. This is because when systematic bits are transmitted while their error reliability is raised or their error rate is lowered, the overall transmission performance can be improved as compared with when parity bits are transmitted while their error reliability is raised or their error rate is lowered.

That is, if systematic bits are transmitted in such a manner as to have a lower error rate than that of parity bits through the capability of an encoder outputting the systematic bits and the parity bits, the overall packet error rate can be lowered and thus the overall transmission performance can be improved under the same conditions.

The transmitter interleaves the divided systematic and parity bits, respectively in step 705, and stores respective coded symbols of the interleaved data as one bit stream in step 706.

In step 707, the stored bit stream is mapped to long blocks in such order that channel estimation performance, that is, reliability can be ensured. In other words, according to fixed mapping sequence, the bit stream is mapped to the long blocks in order from a long block adjacent to a pilot resource and thus having the highest channel estimation to a long block having the lowest channel estimation performance. The systematic bits are located in the head portion of the bit stream, and the parity bits are located in the tail portion of the bit stream. Thus, the systematic bits whose reliability must be ensured are mapped to resources having higher channel estimation performance, that is, long blocks having higher channel estimation performance. To this end, the bit stream is mapped from its head portion to its tail portion according to the mapping sequence starting from the long block having the highest channel estimation performance.

For example, the bit stream may be mapped to the long blocks in order of long block #2, long block #5, long block #3, long block #4, long block #1 and long block #6. That is, the systematic bits whose reliability must be ensured and the parity bits are allocated in that order to long block #2, long block #5, long block #3, long block #4, long block #1 and long block #6.

The transmitter transmits the long blocks in step 708, and terminates the transmission operation in step 709.

FIG. 8 illustrates the structure of a transmitter according to an exemplary embodiment of the present invention. Referring to FIG. 8, information data 801 to be transmitted is encoded in an encoder 802, and is output in the form of coded symbols divided into systematic bits 803 and parity bits 804. In addition to encoding, the encoder 802

may conduct bit rate matching for matching the input bit rate to the output bit rate.

The systematic bits 803 and the parity bits 804 are independently interleaved through interleavers 805, 806. A bit collection unit 807 collects the interleaved systematic and parity bits, and arranges them in order of the systematic bits and the parity bits.

A mapping unit 810 maps a bit stream, which is output from the bit collection unit 807, to radio resources, that is, long blocks, according to fixed mapping sequence. Under the control of a control signal 809 from a mapping sequence controller unit 808, the mapping is carried out in order from a long block having the highest channel estimation performance to a long block having the lowest channel estimation performance.

According to an exemplary embodiment of the present invention, a long block, which is located closer to the position of a pilot resource in terms of time, has better channel estimation performance. More specially, when a plurality of pilots are time division multiplexed and transmitted, and the plurality of pilots are allocated to fixed specific short blocks, respectively, long blocks located between the short blocks provide the best channel estimation performance. Thus, the systematic bits of the bit stream, whose reliability must be ensured, are sequentially mapped to the long blocks, starting from a long block close to the short blocks and capable of ensuring the highest reliability.

As an example, the mapping sequence controller unit 808 controls the mapping unit 810 to map the bit stream to the resources in order of long block #2, long block #5, long block #3, long block #4, long block #1 and long block #6, according to how good channel estimation performances thereof are.

Further, the order in which the bit stream is mapped to the long blocks may vary according to channel situations of a radio environment (i.e., the channel conditions of resources) or channel estimation techniques, and may be differently set according to whether or not any part of the bit stream is retransmitted. Reference will now be made in detail to how the bit collection unit 807 and the bit mapping unit 810 operate.

If the systematic bits and the parity bits are input into the bit collection

unit 807, the bit collection unit 807 multiplexes them in such a manner that all the systematic bits are arranged ahead and the remaining parity bits are arranged following the systematic bits, and outputs the bit stream including the arranged systematic and parity bits. That is, the systematic bits are input first and the parity bits are input next into the bit mapping unit 810.

Thereafter, the bit mapping unit 810 divides the bit stream into six temporary blocks having the same size. When an input bit stream does not correspond to a multiple of 6, additional bits may be added so that the input bit stream corresponds to a multiple of 6. The reason why the bit stream is divided into the six temporary blocks is that the number of the temporary blocks must be equal to that of long blocks currently carrying data within one subframe. Thus, if the number of long blocks belonging to one subframe changes, the number of temporary blocks must also change in such a manner as to be equal to the number of the long blocks. Hereinafter, data divided into the six temporary blocks will be denominated BLl, BL2, BL3, BL4, BL5 and BL6.

The bit mapping unit 810 newly arranges the six temporary blocks through interleaving between the temporary blocks, that is, transposes the temporary blocks according to the sequence for ensuring the reliability of the data.

To this end, the mapping sequence controller unit 808 must specify a mapping pattern such that input data entering first can go to a place where channel estimation performance is best, as described through FIG. 6.

For example, if the channel estimation performance of a long block is set in order of long block #2, long block #5, long block #3, long block #4, long block #1 and long block #6, based on the positions of pilots as illustrated in FIG. 6, the bit mapping unit 810 interleaves the six blocks in such a manner that they can be output in order of BL5, BLl, BL3, BL4, BL2 and BL6.

Subsequently, the interleaved bit stream is sequentially mapped to resources allocated to the transmitter. An output from the interleaving process is mapped first to the first long block, and fills all frequency bands corresponding to the first long block. The output continually fills all frequency bands

corresponding to the second long block, and then sequentially fills those corresponding to the third, fourth, fifth and sixth long blocks.

Therefore, according to the present invention, mapping is done such that the higher the reliability of a bit must be, the better the channel estimation performance of a long block carrying the bit is. The mapping pattern, that is, an interleaving pattern between the temporary blocks, varies with the position of a pilot resource.

That is, the bit mapping unit 810 interleaves an input bit stream in such a manner that a bit input ahead of others, that is, a bit whose reliability must be ensured, is mapped to a place located closest to a pilot resource. Of course, the mapping pattern must be able to vary with the position of a pilot resource.

After the mapping is completed, a multiplexer 811 multiplexes the bit stream, to which radio resources are allocated, together with a coded signal of TF control information 812, and transmits them to a receiver through a transmitter unit 814.

FIG. 9 is a flowchart illustrating the operation of a receiver according to an exemplary embodiment of the present invention.

Referring to FIG. 9, if the receiver's operation starts with step 901, the receiver receives a radio signal through a radio processor unit in step 902. In step 903, the receiver decodes TF control information, which defines the transfer format of transmitted packet data, from the received radio signal. Thus, the receiver acquires the coding rate of packet data to be received.

In step 904, the receiver ascertains the ratio between systematic bits and parity bits from a specific resource of the received radio signal, based on the acquired coding rate. That is, the receiver separates the amount of systematic bits from the amount of parity bits.

If the amounts of bits for specific information data are determined, respectively, in step 905, the receiver acquires systematic bits from a received subframe, to which the determined amount of systematic bits are allocated, according to mapping sequence set in such a manner as to ensure channel estimation performance. That is, the receiver sequentially acquires systematic bits from long blocks in order from a long block closest to a short block to which

a pilot is allocated and thus having the highest channel estimation performance to a long block having the lowest channel estimation performance, and stores the acquired systematic blocks. The receiver stores the remaining bits, which are included in the sub frame according to the mapping sequence, as parity bits. The mapping sequence is the same as the sequence in which radio resources are allocated based on their channel estimation performance, for example, the sequence of long block #2, long block #5, long block #3, long block #4, long block #1 and long block #6.

Subsequently, in step 906, the receiver deinterleaves the separately stored systematic and parity bits through at least one deinterleaving, respectively.

The deinterleaved bits are decoded into information data in step 907. The decoded information data is stored in step 908, and the receiver ends its operation in step 909.

FIG. 10 illustrates the structure of a receiver according to an exemplary embodiment of the present invention.

Referring to FIG. 10, a receiver unit 1002 receives a signal carried by any radio resource 1001.

A first demultiplexer 1003 the received signal into a TF control information-related signal and a packet data-related signal. A decoder 1004 decodes the TF control information-related signal to thereby acquire TF control information 1005.

Among the TF control information, control information 1006 regarding the coding rate of packet data is applied to a second demultiplexer 1007, which in turn divides the packet data-related information into systematic bits and parity bits by using the control information 1006, and demultiplexes the systematic bits 1012 and the parity bits 1013 under the control of a mapping sequence control signal 1009 from a mapping sequence controller unit 1008.

Reference will now be made in detail to how the two demultiplexers 1003, 1007 operate. The demultiplexer 1003 outputs the received signal in order of long blocks. Here, the output signal is output in unit of all frequency bands included in one long block.

That is, the demultiplexer 1003 outputs first a signal received through all frequency bands included in the first long block, and then sequentially outputs signals received through all frequency bands included in the second, third, fourth, fifth and sixth long blocks. Subsequently, the demultiplexer 1007 divides an input bit stream into six temporary blocks having the same size. The reason why the input bit stream is divided into the six temporary blocks is that the number of the temporary blocks must be equal to that of long blocks currently carrying data within one subframe. Thus, if the number of long blocks belonging to one subframe changes, the number of temporary blocks must also change in such a manner as to be equal to the number of the long blocks. Hereinafter, data divided into the six temporary blocks will be denominated BLl, BL2, BL3, BL4, BL5 and BL6.

The demultiplexer 1007 newly arranges the six temporary blocks according to the mapping sequence between the temporary blocks. To this end, the mapping sequence controller unit 1008 must specify a mapping pattern reverse to the mapping pattern applied to a transmitter.

For example, if the channel estimation performance of a long block is set in order of long block #2, long block #5, long block #3, long block #4, long block #1 and long block #6, based on the positions of pilots as illustrated in FIG. 6, the demultiplexer 1007 applies a mapping pattern to the six blocks, that is, transposes the temporary blocks, in such a manner that they can be output in order of BL2, BL5, BL3, BL4, BLl and BL6.

After the temporary blocks are transposed through interleaving according to the mapping pattern, the preceding bit stream 1012 of a newly arranged bit stream, which corresponds to the given number of systematic bits, is output as a systematic bit stream to a deinterleaver 1010. The remaining bit stream 1013 of the newly arranged bit stream, which follows the bit stream corresponding to the number of the systematic bits, is output as parity bits to the deinterleaver 1011.

The demultiplexed systematic and parity bits 1012, 1013 are deinterleaved in the deinterleavers 1010, 1011, respectively, and then are input into a decoder 1014. The decoder 1014 decodes the input deinterleaved systematic and parity bits to thereby acquire information data 1015.

Here, since the decoder 1014 have acquired the coding rate of the information data by using the TF control information 1005 acquired through the decoder 1004, it may also conduct inverse rate matching under the control of the coding rate information 1016. Although exemplary embodiments of the present invention have been described in connection with the case where resources are allocated using time division multiplexing, it is possible to apply the present invention to a frequency division multiplexing system in the same manner.

[Industrial Applicability]

Although several preferred embodiments of the present invention have been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.