KR101208510B1 - / Method for radio resource allocation in OFDM/OFDMA system - Google Patents

Abstract

The present invention relates to a subcarrier allocation method in a multi-carrier system, and more particularly, to a communication method that can be easily scheduled by efficiently allocating a specific frequency time resource.

According to the present invention, a radio resource allocation method includes a plurality of subcarriers adjacent to each other in a frequency domain in a communication system for transmitting an OFDM signal in an OFDM subframe unit including at least one OFDM symbol. Constructing at least one distributed chunk comprising at least one zone chunk and a plurality of subcarriers that are not adjacent to each other in the frequency domain; And multiplexing the at least one zone chunk and the at least one distributed chunk in a time division multiplexing (TDM) scheme and assigning the at least one zone chunk to the OFDM subframe. The number of data symbols transmitted through is characterized in that the same.

OFDM, OFDMA, Scheduling, Chunk, Subcarrier, Zone, Distributed

Description

Radio resource allocation method in OPDM / OFFDMA system {Method for radio resource allocation in OFDM / OFDMA system}

1 is a block diagram of a downlink transceiver of OFDMA according to the present invention and the prior art.

FIG. 2 is a diagram illustrating a method of allocating a chunk, which is a basic unit for allocating the subcarriers, to a specific user.

FIG. 3 is a diagram illustrating a structure of a chunk used for distribution allocation and zone allocation used in an embodiment of the present invention.

FIG. 4 illustrates an example of multiplexing chunks according to the variance allocation method and chunks according to the zonal allocation method in one OFDM subframe according to an embodiment of the present invention.

FIG. 5 is another example of multiplexing chunks according to the variance allocation method and chunks according to the zone allocation method in one OFDM subframe according to an embodiment of the present invention.

6 is a diagram illustrating a method of transmitting control information on the scheduling task performed by a transmitting end to a receiving end according to an embodiment of the present invention.

The present invention relates to a subcarrier allocation method in a multi-carrier system, and more particularly, to a communication method that can be easily scheduled by efficiently allocating a specific frequency time resource.

Hereinafter, orthogonal frequency division multiplexing (OFDM) according to the prior art will be described. The basic principle of OFDM is to divide a high-rate data stream into a large number of low-rate data streams, which are transmitted simultaneously using multiple carriers. Each of the plurality of carriers is called a subcarrier. Since orthogonality exists between the multiple carriers of the OFDM, the frequency components of the carriers can be detected at the receiving end even if they overlap each other. The high data rate data stream is converted into a plurality of low data rate data streams through a serial to parallel converter, and each subcarrier is included in the parallel data streams. After multiplying, the respective data strings are summed and sent to the receiving end.

A plurality of parallel data streams generated by the serial / parallel transform unit may be transmitted to a plurality of subcarriers by an inverse discrete fourier transform (IDFT), and the IDFT is an inverse fast fourier transform (IFFT). Can be implemented efficiently.

Since the symbol duration of the low carrier subcarrier is increased, relative signal dispersion in time due to multipath delay spread is reduced. Inter-symbol interference can be reduced by inserting a guard interval longer than the delay spread of the channel between OFDM symbols. In addition, if a part of the OFDM signal is copied to the guard interval and placed at the beginning of the symbol, the OFDM symbol may be cyclically extended to protect the symbol.

Hereinafter, orthogonal frequency division multiple access (OFDMA) according to the prior art will be described. OFDMA refers to a multiple access method for realizing multiple access by providing each user with a part of subcarriers available in a system using OFDM as a modulation method. OFDMA provides each user with a frequency resource called a subcarrier, and each frequency resource is provided to a plurality of users independently of each other so that they do not overlap each other. After all, frequency resources are allocated mutually exclusive.

Hereinafter, a general OFDMA transceiver will be described. 1 is a block diagram of a downlink transceiver of OFDMA according to the present invention and the prior art.

The transmitter performs constellation mapping on a bit stream for a plurality of users by quadrature phase shift keying (QPSK) or 16 quadrature amplitude modulation (QAM).

That is, the bit stream is mapped to a specific data symbol, and the data symbol is converted into parallel data symbols through an S / P converter. By the serial / parallel conversion operation, the data symbols are converted into parallel symbols equal to the number Nu (n) of subcarriers assigned to each user n. As shown in FIG. 1, the bit stream for user 1 is converted into as many parallel symbols as Nu (1), which is the number of subcarriers allocated to user 1. Subcarriers allocated to each user n may or may not be identical to each other. Accordingly, the data symbols of the respective users may be converted into parallel symbols of the same or unequal size Nu (n).

The data symbols for a specific user converted in parallel are mapped to Nu (n) subcarriers assigned to a specific nth user among all Nc subcarriers, and the remaining Nc- (Nu ( n)) subcarriers are mapped to data symbols of other users. By a symbol to subcarrier mapping module for mapping a symbol to a carrier, zero padding is assigned to a subcarrier to which a user is not assigned. The output of the symbol to subcarrier mapping module is input to an Nc-point inverse fast fourier transform (IFFT) module.

The output of the IFFT module is transmitted after parallel to serial convert is performed after a cyclic prefix is added to reduce inter-symbol interference (ISI).

A general OFDMA transmitting apparatus may form one OFDM symbol through the above-described steps. The OFDM symbol corresponds to a bit stream for at least one user. A general OFDMA transmitting apparatus may transmit data in an OFDM subframe unit including a specific number of OFDM symbols. The size of OFDM symbols included in the OFDM subframe may be the same or grouped into OFDM symbols having a specific size. For example, if the OFDM subframe includes four OFDM symbols, and the sizes of the four OFDM symbols are the same, the four OFDM symbols are sequentially transmitted. The OFDMA transmitting apparatus transmits data in units of the OFDM subframe, and may include data symbols corresponding to bit streams for a specific user in a specific frequency-time domain. In conclusion, a person skilled in the art can arrange data symbols corresponding to bit streams for a specific user in a specific frequency-time domain within the OFDM subframe using the above-described OFDMA transmitting apparatus. have.

The OFDMA receiving apparatus according to the prior art is configured in the inverse of the above-described transmitting apparatus. The received data symbol is inputted to a module that performs symbol to subcarrier mapping after the serial / parallel conversion and the Nc-point FFT. The receiving end decodes a symbol of a subcarrier allocated to the receiving end by the mapping module.

Resource allocation according to OFDMA is described as follows. In the entire frequency band, specific frequency resources (subcarriers) are assigned only to specific users. Thus, the frequency resource is not shared to other users. More specifically, in allocating frequency resources to users in the implementation of OFDMA, in order for each user to receive them, allocation information of subcarriers must be transmitted from the base station to the terminal. Since transmitting the allocation information for all the subcarriers, respectively, is an excessive amount of information, it is preferable to allocate a plurality of subcarriers in chunks to the user in order to reduce the amount of information.

FIG. 2 is a diagram illustrating a method of allocating a chunk, which is a basic unit for allocating the subcarriers, to a specific user. As shown, the method of allocating the chunks may be divided into a distributed allocation method and a localized allocation method. Each illustrated arrow represents a chunk comprising a plurality of subcarriers.

The distributed allocation of FIG. 2 is a method of allocating all chunks among all the chunks to a user when allocating them to the entire system. By assigning chunks over the entire band to specific users, gains from diversity in the frequency domain can be obtained.

Zone allocation in FIG. 2 is a method of allocating chunks of adjacent bands to a specific user in all frequency bands applied to a communication system.

The prior art assigns chunks to users in a particular way, sending data to multiple users.

The present invention has been proposed to improve the prior art, and an object of the present invention is to provide a communication method that can be easily scheduled by efficiently allocating a specific frequency time resource.

Summary of the Invention

According to the present invention, a radio resource allocation method includes a plurality of subcarriers adjacent to each other in a frequency domain in a communication system for transmitting an OFDM signal in an OFDM subframe unit including at least one OFDM symbol. Constructing at least one distributed chunk comprising at least one zone chunk and a plurality of subcarriers that are not adjacent to each other in the frequency domain; And multiplexing the at least one zone chunk and the at least one distributed chunk in a time division multiplexing (TDM) scheme and assigning the at least one zone chunk to the OFDM subframe. The number of data symbols transmitted by each of the zone chunks and the distributed chunks may be constant.

Work of invention Example

Specific operations, features, and effects of the present invention will be further embodied by one embodiment of the present invention described below.

 FIG. 3 is a diagram illustrating a structure of a chunk used for distribution allocation and zone allocation used in an embodiment of the present invention. Hereinafter, with reference to FIG. 3, the structure of the chunk used by a present Example is demonstrated.

As described above, the chunk represents a set of a plurality of subcarriers. There is no limit to the number of subcarriers included in the chunk. In addition, the subcarriers included in the chunk may be configured in various patterns. For example, subcarriers included in the chunk may be concatenated. That is, when the subcarriers are indexed by integers such as 0, 1, 2, 3, etc., if the first chunk includes 0, 1, 2, 3 subcarriers, the second chunk is 4, 5, 6 It may include seven subcarriers. In addition, the subcarriers included in the chunk may be dispersed without being connected. For example, the first chunk may include the 0, 4, 9, 14 subcarriers, and the second chunk may include the second, 6, 11, 17 subcarriers.

The chunk is assigned to a specific user; at least one chunk is assigned to one user. For example, chunks 1,2 and 3 may be assigned to user 1 and chunks 4 and 5 to user 2. One chunk may also be assigned to multiple users. That is, when data is transmitted in a broadcast form at the transmitting end, a specific chunk is allocated to a plurality of users. For example, chunks 1, 2 can be assigned to users 1 and 2, and chunk 3 can be assigned to user 3. Once one chunk is formed, all of the subcarriers included in the chunk are assigned to a particular user. For example, if chunk 1 includes first, second, third, and fourth subcarriers, all of the first, second, third, and fourth subcarriers are assigned to at least one user.

If the transmitting end and the receiving end know the information about the subcarriers included in the chunk together, the transmitting end transmits an index indicating a specific chunk to the receiving end, and the receiving side receives the index information so that the specific chunk can identify which subcarrier. You can see if it does. In other words, if the index information indicating the chunk allocated to a specific receiver is transmitted, the receiver may know the subcarrier allocated to itself through the index information. Through the above-described operation, the transmitting end can efficiently transmit allocation information for a plurality of subcarriers through small size signaling.

As shown in FIG. 2, a method of allocating chunks to specific users is largely divided into distributed allocation and localized allocation. More preferably, the subcarrier pattern included in the chunk used in the present embodiment is determined by a method of allocating the chunk to the user. For example, when allocating the chunks to a user according to the distributed allocation method, the chunks preferably include subcarriers distributed to each other. This is because the distributed allocation method has an advantage of allocating chunks over the entire frequency domain to a specific user, thereby obtaining a gain in frequency diversity.

In addition, when allocating the chunk to a user according to the zone allocation method, the chunk preferably includes a concatenated subcarrier. This is because the zone allocation method is a method of allocating chunks of bands adjacent to each other to all frequency bands applied to a communication system to a specific user. The zone allocation method may obtain a user diversity effect by improving the SINR characteristic of each user by allocating a frequency region having a good channel state to the user. That is, since the channels for a particular first user and a second user are different, the quality of data transmitted by a particular frequency domain will be different for the first and second users. In this case, the chunk corresponding to the continuous frequency domain showing the good quality for the first user is allocated to the first user, and the chunk corresponding to the continuous frequency domain showing the good quality for the second user. By assigning to the second user, a user diversity effect can be obtained.

When the method of allocating the chunk to the user is a zone allocation method, the chunk Chunk_L illustrated in FIG. 3 includes a concatenated subcarrier. In addition, when the method of allocating the chunk to the user is a distributed allocation method, the chunk Chunk_D is composed of distributed subcarriers.

In the case of the zone allocation method, subcarriers 201 to 208 are included in Chunk_L1 210. As described above, the Chunk_L1 preferably includes the subcarriers of the 201 to 208 to be connected. In the distributed allocation method, subcarriers 301 to 308 are included in Chunk_D1 310. In addition, 311 to 318 subcarriers are included in Chunk_D2 320. As described above, the Chunk_D1 includes 301 to 308 subcarriers distributed to each other, and the Chunk_D2 includes 311 to 318 subcarriers distributed to each other.

FIG. 4 illustrates an example of multiplexing chunks according to the variance allocation method and chunks according to the zonal allocation method in one OFDM subframe according to an embodiment of the present invention. As shown, the OFDM sub frame includes seven OFDM symbols. In the example of FIG. 4, the OFDM symbols included in the OFDM subframe are transmitted on 54 subcarriers. In the example of FIG. 4, the first OFDM symbol includes a pilot signal, and the pilot signal may be used for channel estimation and equalization with signal values already known to the transmitting and receiving end. The location of the OFDM symbol is not limited, and may be included in the entire second OFDM symbol, part of a subcarrier for the second OFDM symbol, or may be included in a plurality of OFDM symbols. In the example of FIG. 4, the first OFDM symbol may include control information for the chunk or subcarrier arranged in the OFDM subframe in addition to the pilot signal.

In the example of FIG. 4, a chunk according to the variance allocation method and a chunk according to the zonal allocation method are multiplexed in one OFDM subframe, and a specific OFDM symbol is allocated a chunk according to the variance allocation method and the remaining OFDM symbols For chunks according to the interval allocation method is allocated. That is, chunks according to the variance allocation method are allocated to the second, third and fourth OFDM symbols of FIG. 4, and chunks according to the zonal allocation method are allocated to the fifth, sixth and seventh OFDM symbols. Therefore, in the example of FIG. 4, the chunks according to the above distributed allocation method and the chunks according to the zone allocation method are multiplexed by a TDM (Time Division Multiplexing) method.

As described above, the subcarriers included in the chunks (Chunk_D1, Chunk_D2, Chunk_D3, ..., Chunk_D9) according to the distributed allocation method are preferably distributed with each other, and the chunks (Chunk_L1, Chunk_L2) according to the zone allocation method. , Chunk_L3, ..., Chunk_L9) is preferably connected to the subcarrier.

In the embodiment of Fig. 4, chunks (Chunk_D1, Chunk_D2, Chunk_D3, ..., Chunk_D9 and Chunk_L1, Chunk_L2, Chunk_L3, ..., Chunk_L9) by the distributed allocation method and the zone allocation method are included in each chunk. The number of subcarriers is determined. That is, the Chunk_D1, Chunk_D2, Chunk_D3, ..., Chunk_D9 each include six subcarriers, and each of the Chunk_L1, Chunk_L2, Chunk_L3, ..., Chunk_L9 also includes six subcarriers. The subcarrier is used to transmit one data symbol. Accordingly, Chunk_L1 of FIG. 4 transmits 6 (number of subcarriers) x 3 (number of OFDM symbols) = 18 data symbols.

If the embodiment of FIG. 4 is modified, chunks (Chunk_D1, Chunk_D2, Chunk_D3, ..., Chunk_D9) according to the variance allocation method are arranged for the second and third OFDM symbols, and the fourth, fifth, sixth, seventh, seventh, seventh and seventh OFDM symbols are allocated. If chunks (Chunk_L1, Chunk_L2, Chunk_L3, ..., Chunk_L9) according to the zone allocation method are arranged for OFDM symbols, each of Chunk_D1, Chunk_D2, Chunk_D3, ..., Chunk_D9 has 12 (6 * 2) pieces of data. The symbol may be transmitted, and each of Chunk_L1, Chunk_L2, Chunk_L3, ..., Chunk_L9 may transmit 24 (6 * 4) data symbols.

In the embodiment of FIG. 4, two different distributed allocation methods are multiplexed in one OFDM subframe, and thus, advantages of the two distributed allocation methods may be obtained together. However, the embodiment of FIG. 4 is characterized in that the number of data symbols that can be transmitted by each chunk varies according to the number of OFDM symbols used by the distributed allocation method and the zone allocation method. When the number of data symbols that can be transmitted is changed in this way, scheduling at the transmitting end may be complicated by an increase in the modulation and coding set (MCS) level. That is, scheduling in a general transmitting end may be performed according to a predetermined modulation and coding combination. For example, when the number of data symbols that each chunk can transmit is fixed, M MCS combinations (full modulation and coding combinations) may be possible when scheduling data using the chunks. However, if the number of data each chunk can transmit is changed to two, the total modulation and coding combination may increase to 2M. That is, when the number of data symbols that can be transmitted varies, the modulation and coding set (MCS) level may increase, which may complicate scheduling at the transmitting end.

Hereinafter, the embodiment of FIG. 5 is an improvement of the embodiment of FIG. 4 described above. In the embodiment of FIG. 5, when allocating a frequency-time resource in units of chunks, the distributed allocation method and the zone allocation method are used together, but the data symbols of the chunk according to the distributed allocation method are transmitted. The number is fixed and the number of data symbols transmitted by the chunk according to the zone allocation method is fixed.

Hereinafter, a method of allocating the chunks according to the embodiment of FIG. 5 will be described. First, the number of data symbols that can be transmitted through a chunk by the distributed allocation method and the zone allocation method is referred to as D _D and D _L , respectively. In addition, the number of OFDM symbols in which chunks are transmitted by the distributed allocation method and the zone allocation method is referred to as O _D and O _L , respectively. In addition, the number of subcarriers included in the chunk by the distributed allocation method and the zone allocation method is referred to as S _D and S _L , respectively. In this case, it has the same relationship as in Equation 1 below.

In the embodiment of FIG. 4, since the distributed allocation method and the zone allocation method divide the entire OFDM symbols in a specific OFDM subframe, the number of OFDM symbols used by the distributed allocation method and the zone allocation method is O _D , O _L. This may vary for each OFDM subframe.

However, the embodiment of FIG. 5 follows the following equation 2 in allocating S _D and S _L to keep D _D and D _L constant.

5 has a feature in that the number of subcarriers included in a chunk depends on the number of OFDM symbols to which the chunk is transmitted. That is, in the embodiment of FIG. 5, both the number of subcarriers used for chunks and the number of OFDM symbols used for transmitting the chunks are variable.

Hereinafter, this embodiment will be described with reference to FIG. 5.

5 shows four OFDM subframes, wherein the four OFDM subframes include seven OFDM symbols. In the example of FIG. 5, OFDM symbols included in the OFDM subframe are transmitted on 54 subcarriers. For convenience of explanation, the 54 subcarriers will be described as being divided into '# 1 subcarriers' to '# 54 subcarriers'.

In the example of FIG. 5, the first OFDM symbol includes a pilot signal, and the pilot signal may be used for channel estimation and equalization with signal values already known to the transmitting and receiving end. The location of the OFDM symbol is not limited, and may be included in the entire second OFDM symbol, part of a subcarrier for the second OFDM symbol, or may be included in a plurality of OFDM symbols. In the example of FIG. 5, the first OFDM symbol may include control information for the chunk or subcarrier arranged in the OFDM subframe in addition to the pilot signal.

In the example of FIG. 5, the second to seventh OFDM symbols of the seven OFDM symbols are used for data transmission. In addition, the D _D and D _L is set to 36.

5 shows chunks (Chunk_D1, Chunk_D2, Chunk_D3, ..., Chunk_D9) using up to nine of the above distributed allocation methods and chunks (Chunk_L1, Chunk_L2, Chunk_L3, ..., based on up to nine zone allocation methods). Chunk_L9).

In FIG. 5, there are nine chunks 600 in total by the distributed allocation method. 5 shows four frame patterns, and the second, third, and fourth frame patterns include chunks according to the above distributed allocation method. Each frame pattern represents an example in which the embodiment of FIG. 5 is modified, and the number of the frame patterns is not limited. In the example of FIG. 5, four frame patterns are determined, and the frame pattern can be represented by 2 bits of information. For example, the first frame pattern may be represented by 00, the second frame pattern may be represented by 01, the third frame pattern may be represented by 10, and the fourth frame pattern may be represented by 11. The transmitting end may select the frame pattern and transmit data to the receiving end. For example, the first OFDM subframe may transmit a subframe according to the second frame pattern, and the next OFDM subframe may transmit a subframe according to the third frame pattern. The embodiment of Figure 5 proposes a method for transmitting and receiving data by determining the frame pattern as described above to reduce the control information transmitted between the transmitting and receiving end. However, this proposal is only a preferred embodiment of the present invention, and the present invention is not limited by the number or type of such frame patterns. Accordingly, the transmitting end according to the present invention may transmit user data to the receiving end by multiplexing the chunks according to the above-described distributed allocation method or zone allocation method, without determining a frame pattern or changing a predetermined frame pattern. .

5 illustrates a subcarrier 700 included in a specific chunk by the method of FIG. The subcarrier 700 included in each chunk indicates a subcarrier included in each chunk according to the example of FIG. 4. Referring to 700, when the Chunk_D1 510 is generated according to the example of FIG. 4, the Chunk_D1 510 includes subcarriers 411, 412, 413, 414, 415, and 416. However, when the Chunk_D1 510 is generated according to the example of FIG. 5, the Chunk_D1 510 may include subcarriers 611, 612, 613, ..., 627, and 628 (second frame). For patterns). In addition, the Chunk_D1 510 may include subcarriers 711, 712, 713,..., 718, and 719 (for a third frame pattern). In addition, the Chunk_D1 510 may include subcarriers 811, 812, 813,..., 816 (for a fourth frame pattern). Such a chunk construction method is described in more detail below.

In Fig. 5, the maximum number of chunks by the zone allocation method is nine. For example, the Chunk_L1 includes # 1 subcarriers to # 6 subcarriers among 54 subcarriers.

First, the first frame pattern of FIG. 5 will be described. The first frame pattern is a case in which only a chunk according to the zone allocation method is used in an OFDM subframe, where O _D = 0 and O _L = 6. The S _D and S _L is preferably determined by Equation 2, where S _L = D _L / O _L = 36/6. As shown, the chunks (Chunk_L1, Chunk_L2, Chunk_L3, ..., Chunk_L8, Chunk_L9) according to the zone allocation method included in the first frame pattern include six subcarriers.

Hereinafter, the second frame pattern of FIG. 5 will be described. According to the second frame pattern, the chunk according to the zone allocation method and the chunk according to the distributed allocation method are multiplexed in the TDM scheme in an OFDM subframe. In the case of the second frame pattern, since the second and third OFDM symbols include chunks according to the variance allocation method, the relationship of O _D = 2 is established. In addition, the 4, 5, 6, 7 OFDM symbols because it contains a chunk corresponding to the zone allocation, holds the relationship of the O _L = 4. The S _D and S _L is preferably determined by Equation 2, wherein S _D = D _D / O _D = 36/2 = 18, S _L = D _L / O _L = 36/4 = 9 do. As shown, the chunks included in the second and third OFDM symbols include 3 (= total subcarriers / S _D ) chunks Chunk_D1, Chunk_D2, and Chunk_D3 having 18 (= S _D ) subcarriers. do. For example, the Chunk_D1 510 includes subcarriers 611, 612, 613, 614, ..., 626, 627, and 628. In addition, Chunk_L1 according to the zone allocation method includes # 1 subcarriers to # 9 subcarriers, Chunk_L2 includes # 10 subcarriers to # 18 subcarriers, and Chunk_L6 includes # 49 subcarriers to # 54 subcarriers. Include.

Hereinafter, the first frame pattern and the second frame pattern are compared and described. The first frame pattern includes nine chunks (Chunk_L1, Chunk_L2, Chunk_L3, ..., Chunk_L8, Chunk_L9), each of which contains six subcarriers and transmits 36 data symbols. The second frame pattern includes nine chunks (Chunk_D1, Chunk_D2, Chunk_D3 and Chunk_L1, Chunk_L2, Chunk_L3, Chunk_L4, Chunk_L5, Chunk_L6) and transmits 36 data symbols.

Hereinafter, the third frame pattern of FIG. 5 will be described. According to the third frame pattern, the chunk according to the zone allocation method and the chunk according to the distributed allocation method are multiplexed in the TDM scheme in an OFDM subframe. In the case of the third frame pattern, since the second, third, fourth and fifth OFDM symbols include chunks according to the variance allocation method, the relationship of O _D = 4 is established. In addition, since the sixth and seventh OFDM symbols include a chunk according to the zone allocation method, the relationship of O _L = 2 is established. The S _D and S _L is the desirable bar, the _{S D = D D / O D} = 36/4 = 9, S L = D L / O L = 36/2 = 18 , which is determined by the equation (2) do. As illustrated, the chunks included in the second, 3, 4, and 5 OFDM symbols include (= total subcarriers / S _D ) chunks (Chunk_D1, Chunk_D2, Chunk_D3,) having 9 (= S _D ) subcarriers. Chunk_D4, Chunk_D5, and Chunk_D6). For example, the Chunk_D1 510 includes subcarriers 711, 712, 713, 714, 715, 716, 717, 718, and 719 subcarriers. In addition, Chunk_L1 according to the above zone allocation method includes # 1 subcarriers to # 18 subcarriers, Chunk_L2 includes # 19 subcarriers to # 36 subcarriers, and Chunk_L3 includes # 37 subcarriers to # 54 subcarriers. Include.

Hereinafter, the second frame pattern and the third frame pattern are compared and described. The second frame pattern includes nine chunks (Chunk_D1, Chunk_D2, Chunk_D3 and Chunk_L1, Chunk_L2, Chunk_L3, Chunk_L4, Chunk_L5, Chunk_L6) and transmits 36 data symbols. The third frame pattern includes nine chunks (Chunk_D1, Chunk_D2, Chunk_D3, Chunk_D4, Chunk_D5, Chunk_D6 and Chunk_L1, Chunk_L2, Chunk_L3) and transmits 36 data symbols.

Hereinafter, the fourth frame pattern of FIG. 5 will be described. In case of the fourth frame pattern, only the chunk according to the distributed allocation method is included in the OFDM subframe. In the case of the fourth frame pattern, since the second to seventh OFDM symbols include chunks according to the distributed allocation method, the relationship of O _L = 0 and O _D = 6 is established. The S _D and S _L are preferably determined by Equation 2, where S _D = D _D / O _D = 36/6 = 6 and S _L == 0. As shown, the chunks included in the second to seventh OFDM symbols include 9 (= total subcarriers / S _D ) chunks (Chunk_D1, Chunk_D2, Chunk_D3, Chunk_D4,) having 6 (= S _D ) subcarriers. ..., Chunk_D8, Chunk_D9). For example, the Chunk_D1 510 includes subcarriers 811, 812, 813, 814, 815, and 816 subcarriers.

Hereinafter, the third frame pattern and the fourth frame pattern are compared and described. The third frame pattern includes nine chunks (Chunk_D1, Chunk_D2, Chunk_D3, Chunk_D4, Chunk_D5, Chunk_D6 and Chunk_L1, Chunk_L2, Chunk_L3) and transmits 36 data symbols. The fourth frame pattern includes nine chunks (Chunk_D1, Chunk_D2, Chunk_D3, Chunk_D4, ..., Chunk_D8, Chunk_D9) and transmits 36 data symbols.

Referring to the frame pattern according to the embodiment of FIG. 5, the chunk according to the zone allocation method or the dispersion allocation method is allocated for each OFDM symbol in the same manner as in FIG. 4. However, the number of data symbols transmitted by each chunk included in the OFDM subframe is the same. That is, the embodiment of FIG. 5 may solve the aforementioned problem of increasing the MCS level.

Hereinafter, a scheduling method for implementing a frame pattern according to the embodiment of FIG. 5 will be described. In order to allocate a chunk as in the subframe structure of FIG. 5 described above, a transmitting end (for example, may be a base station NodeB, etc.) is first used for the distributed allocation method and the zone allocation method. The amount of data symbols to be transmitted through the chunk is determined (S10). In addition, the transmitter determines the number of OFDM symbols for transmitting chunks according to the distributed allocation method and the number of OFDM symbols for transmitting chunks according to the zone allocation method (S20). When the determined amount of data symbols and the number of OFDM symbols are determined, the number of subcarriers used by each chunk is calculated (S30). Preferably, the number of subcarriers is calculated by Equation 2. The transmitting end may arrange the chunk in the OFDM subframe based on the information obtained through S10 to S30 described above. The chunk is used for a specific receiving end (eg, a terminal), and may allocate specific frequency-time resources to the chunk to transmit desired data to the desired receiving end.

Control information on the scheduling task performed by the transmitting end is transmitted to the receiving end. 6 is a diagram illustrating a method of transmitting control information on the scheduling task performed by a transmitting end to a receiving end. 6 relates to a method for transmitting control information when transmitting the chunks according to FIG. 5. Hereinafter, a method of transmitting control information on the scheduling task to the receiving end with reference to FIG. 6 in the transmitting end will be described.

The transmitter of FIG. 6 may use a specific number of frame patterns in forming the OFDM subframe. In the example of FIG. 6, data is transmitted to a receiving end using four frame patterns used in FIG. 5.

The transmitting end performs a scheduling operation, and determines a pattern for the OFDM subframe (S901). In addition, the transmitter configures a map for Chunk_L (chunk according to the zone allocation method) and Chunk_D (chunk according to the distributed allocation method) (S902). The maps for the Chunk_L and Chunk_D indicate which frequency-time resources a particular chunk is transmitted as shown in FIG. 5. That is, by performing the step of constructing the map, it is determined how many subcarriers the chunks Chunk_L and Chunk_D include. For example, using the second frame pattern of FIG. 5, the first OFDM symbol transmits pilot and control information, the second and third OFDM symbols transmit the Chunk_D, and the fourth, fifth, sixth, and seventh OFDM The symbol is determined to transmit the Chunk_L. Therefore, when the transmitter determines the number of subcarriers included in each chunk, the number of data symbols that each chunk can transmit is determined, and thus a map for Chunk_L and Chunk_D can be configured. As described above, each chunk is allocated to at least one receiving end (eg, a UE), and the transmitting end determines which receiving end to allocate the chunk (S903).

As described above, using the pattern for the OFDM subframe is only a preferred embodiment according to the present invention. If the pattern for the OFDM subframe is not used, step S901 is omitted, and In operation S902, an OFDM symbol and a subcarrier on which a specific chunk is transmitted may be determined.

Control information according to the scheduling of S901 to S903 is transmitted to the terminal. However, the control information is more preferably transmitted through a separate path according to the information. When the transmitting end transmits data according to a specific frame pattern, information on the frame pattern is required by all receiving ends. Therefore, the information on the frame pattern is preferably provided through common signaling (S908). If all of the receiving end communicating with the transmitting end acquires the information on the frame pattern, the receiving end is assigned whether it is allocated the chunk according to the zone allocation method or the chunk according to the distributed allocation method. The allocation method information to be notified is received (S904). One bit is sufficient for the allocation scheme information. In addition, the receiving end further receives an index for distinguishing each chunk (S905). For example, the first receiving end receives the allocation scheme information that he has been allocated Chunk_D, and further receives the index information that he has been allocated chunks one to three. In addition, the first receiving end may already know that the OFDM subframe of the second pattern is transmitted through the common signaling. In this case, when the first receiving end receives the allocation method information, the index information, and the information on the frame pattern, the first receiving end may know what chunk is allocated for the first receiving end. That is, the first receiving end may configure a Chunk_D map through the allocation method information, the index information, and the information about the frame pattern (S910). The first receiving end receives and decodes Chunk_D1, Chunk_D2, and Chunk_D3 (S911). If the second receiving end is allocated Chunk_L, data for the second receiving end may be obtained by performing operations S912 to S914 corresponding to S909 to S911. Since the allocation method information and the index information may be determined differently according to each receiving end, the allocation method information and the index information may be transmitted through dedicated signaling.

Instead of selecting the method of transmitting the allocation method information to a specific receiver as described above, the method of displaying the index information may be improved to transmit control information about scheduling to the receiver. Hereinafter, a method of transmitting control information about scheduling to the receiving end without separately transmitting the allocation method information will be described.

If the index of the Chunk_D and the index of the Chunk_L are newly configured so that the indexes do not overlap with each other, and the transmitting end and the receiving end share the new index configuration method, the transmitting end needs to separately transmit the allocation method information. There is no. Through this, it is possible to save the communication resources allocated to transmitting the allocation scheme information.

For example, assume that the number of Chunk_D allocated to a specific OFDM subframe is N _D , the number of Chunk_L is N _L , the sum of the two is N _T , the index of Chunk_D is I _D , and the index of Chunk_L is I _L. do. In this case, the I _D has a value from 1 to N _D , and the I _L has a value from 1 to N _L. The index of Chunk_D and the index of Chunk_L are distinguished through an integrated index called I _N. The unified index I _N may include information about the index of the Chunk_D and the index of Chunk_L by various methods. Hereinafter, an example will be described in which one unified index I _N includes both information on the index of Chunk_D and the index of Chunk_L. For example, according to a separate signaling or communication initial setting between the transmitting and receiving end, the transmitting end includes information on the index of the Chunk_D in the front part of the integration index I _N and the Chunk_L in the remaining part. Information about the index of the can be included. That is, in constructing the unified index (I _N ), if the index of Chunk_D is configured as I _N = I _D , and the index of Chunk_L is configured as I _N = I _L + N _D, then when 1 = I _N = N _D , _D = I _N and N _D + 1 = I _N = N _D + N _L is I _L = I _N -N _{D so} that I _D and I _L can be distinguished without allocation method information, respectively.

As another example, the transmitting end may include information about the index of the Chunk_L in the front part of the integration index I _N and include information about the index of the Chunk_D in the remaining part. That is, in constructing the unified index (I _N ), if the index of Chunk_L is configured as I _N = I _L , and the index of Chunk_D is configured as I _N = I _D + N _{L and} is transmitted, 1 at I = I _N = N _{L Since L} = I _N and N _L +1 = I _N = N _L + N _D becomes I _D = I _N -N _L, the receiving end can distinguish the I _D from the I _L without allocation method information.

The unified index is an index including both of the indexes of the indexes of the Chunk_D and the indexes of the Chunk_L without overlapping, and there is no limitation in the method of configuring the unified index. However, as in the above-described examples, it is preferable that the index of Chunk_D and the index of Chunk_L are continuously arranged.

This embodiment omits the step (S904) of transmitting the allocation method information through the above-described method, and improves the step (905) of transmitting the index for distinguishing the chunks, so that the receiving end transmits data of the transmitting end. There is a feature that transmits information that can be decoded.

According to the present embodiment, a specific receiving end (for example, a specific terminal) may be assigned only Chunk_L or Chunk_D, and the Chunk_L and Chunk_D may be assigned and used simultaneously.

The embodiment of FIG. 5 uses a specific number of frame patterns. In constructing the frame patterns, chunks according to the distributed allocation method are preferably arranged in a frequency-time domain adjacent to a pilot signal. For example, in the OFDM subframe of FIG. 5, since the first OFDM symbol includes a pilot signal, it is preferable to place a chunk according to the above distributed allocation method in the second OFDM symbol. The chunk according to the zone allocation method is allocated to the receiving end of the environment in which the channel changes somewhat late, while the chunk according to the distributed allocation method is likely to be allocated mainly to the receiving end in which the channel changes quickly. In addition, when a pilot for channel estimation is included in a specific OFDM symbol, equalization is difficult due to difficult channel estimation for data transmitted through an OFDM symbol far from the OFDM symbol. Accordingly, the embodiment of FIG. 5 preferentially allocates the chunk according to the distributed allocation method to the OFDM symbol after the first OFDM symbol and allocates the chunk according to the zone allocation method after the allocation is completed.

Hereinafter, a subcarrier used by a chunk according to the above distributed allocation method and zone allocation method will be described. It is preferable that subcarriers included in the chunks according to the above-described distributed allocation method used in the embodiments of Figs. 4 and 5 are dispersed among the chunks having indices that are continuous to each other. For example, the fourth frame pattern of FIG. 5 is as follows. First, Chunk_D1 510 includes 811, 812, 813, 814, 815, and 816 subcarriers, and the six subcarriers are # 1, # 10, # 19, # 28, # 37, and # 46 subcarriers, respectively. to be. In addition, Chunk_D2 520 also includes six subcarriers, and the six subcarriers are # 5, # 14, # 23, # 32, # 41, and # 50 subcarriers, respectively. The indices of Chunk_D1 and Chunk_D2 are continuous with each other by 1 and 2, respectively. Subcarriers included in Chunk_D given with consecutive indices are not adjacent to each other. In general, in order to reduce control information transmitted to a receiving end, one receiving end is allocated with chunks having consecutive indexes. For example, it is common to assign chunks with indexes 1, 2, 3, 4, 5, 6 to the first receiving end rather than allocating chunks with indexes 1, 6, 7, 10, 13, 14. . This is because when the chunks having consecutive indexes are allocated to each other, information on the indexes can be reduced. In this case, since the subcarriers included in the Chunk_D received with the continuous indexes are not adjacent to each other, the chunk may include more distributed subcarriers.

As another example, the index may not be allocated continuously so that the chunk according to the distributed allocation method includes the distributed subcarriers. For example, the chunk (Chunk_D1) having index 1 includes # 1, # 5, # 9, # 13, # 17, and # 21 subcarriers, and the chunk (Chunk_D2) having index 2 has # 2, # 6. , # 10, # 14, # 18, # 22 subcarriers, and chunk having index 6 (Chunk_D6 may include # 27, # 31, # 35, # 39, # 43, # 47 subcarriers In this case, when two chunks are allocated to the first receiving end, an index may be allocated in consideration of the subcarriers included in each of the chunks without allocating the Chunk_D1 and Chunk_D2, that is, Chunk_D1 and Chunk_D6. Alternatively, Chunk_D2 and Chunk_D6 may be allocated, in which case, the size of information for each index is increased, but there is an advantage in that the assignment of subcarriers arranged in each chunk is easily performed.

In the case of forming the chunk by the distributed allocation method, it is more preferable that frequency hopping is performed in the OFDM symbol or the OFDM subframe unit for the subcarriers included in the chunk. For example, if Chunk_D1 includes # 1, # 5, # 9, # 13, # 17, and # 21 subcarriers, the Chunk_D1 is # 2, # 7, # 12, in the next OFDM symbol or the next OFDM frame. # 17, # 22, # 27 may include the carrier. That is, the subcarrier combination allocated to Chunk_D1 may be changed in order to reduce interference between adjacent cells and increase the frequency diversity effect. Since the hopping pattern varies depending on the number of subcarriers, the hopping pattern may vary according to the number of OFDM symbols in which a chunk including the subcarriers is transmitted. This is because the number of subcarriers included in the chunk changes as the number of OFDM symbols to which the chunk is transmitted varies.

It will be apparent to those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Accordingly, the above detailed description should not be construed as limited in every respect and should be considered as illustrative. The scope of the invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the invention are included in the scope of the invention.

The present invention has the following advantageous effects.

The present invention relates to an improvement of a subcarrier resource allocation scheme of a multi-carrier system. The combination of subcarriers constituting a chunk of a distributed allocation scheme and a zone allocation scheme is different. When used, the distributed allocation scheme has an advantageous effect of efficiently obtaining frequency diversity gain. In addition, the zone allocation scheme has an advantageous effect of obtaining user diversity gain.

Claims (16)

A communication system for transmitting an OFDM signal in units of OFDM subframes including a plurality of OFDM symbols, Configuring at least one distributed chunk including at least one zone chunk comprising a plurality of subcarriers adjacent to each other in a frequency domain and a plurality of subcarriers not adjacent to each other in the frequency domain; And Multiplexing the at least one zone chunk and the at least one distributed chunk in a time division multiplexing (TDM) scheme and assigning them to the OFDM subframe Including but not limited to The number of data symbols transmitted through the zone chunk and the distributed chunk is the same. A radio resource allocation method in an OFDM / OFDMA system, characterized in that. The method of claim 1, The at least one zone chunk is assigned to a plurality of consecutive OFDM symbols. A radio resource allocation method in an OFDM / OFDMA system, characterized in that. The method of claim 1, The at least one distributed chunk is assigned to a plurality of consecutive OFDM symbols. A radio resource allocation method in an OFDM / OFDMA system, characterized in that. The method of claim 1, wherein assigning the chunk to the OFDM subframe comprises: It is a step of multiplexing according to Time Division Multiplexing (TDM) according to a preset frame pattern. A radio resource allocation method in an OFDM / OFDMA system, characterized in that. 5. The method of claim 4, Transmitting information about the frame pattern Radio resource allocation method in an OFDM / OFDM system, characterized in that it further comprises. The method of claim 5, The information about the frame pattern is transmitted in the form of broadcast A radio resource allocation method in an OFDM / OFDMA system, characterized in that. The method of claim 1, The OFDM subframe includes one OFDM symbol including a pilot signal. A radio resource allocation method in an OFDM / OFDMA system, characterized in that. The method of claim 7, wherein The distributed chunk is allocated to a next symbol of an OFDM symbol including the pilot signal. A radio resource allocation method in an OFDM / OFDMA system, characterized in that. The method of claim 1, Assigning the at least one zone chunk and the at least one distributed chunk to at least one receiving end. To include more A radio resource allocation method in an OFDM / OFDMA system, characterized in that. 10. The method of claim 9, Transmitting to the receiving end to which the chunk is allocated an identifier indicating whether the allocated chunk is the zone chunk or the distributed chunk. Radio resource allocation method in an OFDM / OFDM system, characterized in that it further comprises. 10. The method of claim 9, Transmitting continuous index information indicating the allocated chunk to a receiving end to which the chunk is allocated; Radio resource allocation method in an OFDM / OFDM system, characterized in that it further comprises. 12. The method of claim 11, A plurality of subcarriers included in the distributed chunk having the index value, Not adjacent to a plurality of subcarriers included in a chunk having a previous value or a next value of the index value. A radio resource allocation method in an OFDM / OFDMA system, characterized in that. The method of claim 1, The subcarrier included in at least one of the at least one zone chunk and the at least one distributed chunk is changed in the OFDM symbol unit. A radio resource allocation method in an OFDM / OFDMA system, characterized in that. The method of claim 1, Subcarriers included in at least one of the at least one zone chunk and the at least one distributed chunk are changed in units of the OFDM subframe. A radio resource allocation method in an OFDM / OFDMA system, characterized in that. 10. The method of claim 9, Transmitting unified index information including a zone chunk index corresponding to the at least one zone chunk and a distributed chunk index corresponding to the at least one distributed chunk, to the receiving end to which the chunk is allocated; Radio resource allocation method in an OFDM / OFDM system, characterized in that it further comprises. 16. The method of claim 15, The zoned chunk index and the distributed chunk index may be included in the unified index without collapsing each other. A radio resource allocation method in an OFDM / OFDMA system, characterized in that.

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