KR20090089573A - Method of data transmission using effective subcarrier mapping - Google Patents

Abstract

A data transmission method using an efficient subcarrier wave mapping is provided to efficiently perform a localized mapping and a distributed mapping in all frequency bands at the same time. A logical frame is prepared. A physical frame in which a localized mapping and a distributed mapping are mixed is generated in the same OFDM(Orthogonal Frequency Division Multiplexing) symbol. The generated physical frame is transmitted. The localized mapping(5,6,7) maps adjacent subcarrier waves in the logical frame to adjacent subcarrier waves of the same position of the physical frame. The distributed mapping(1,2,3,4) maps a subcarrier wave of the logical frame to a subcarrier wave of an arbitrary position of the physical frame.

Description

Data transmission method using efficient subcarrier mapping {Method of Data Transmission using Effective Subcarrier Mapping}

The present invention relates to wireless communication, and more particularly, to a data transmission method using efficient subcarrier mapping.

Wireless communication systems are widely used to provide various kinds of communication. For example, voice and / or data are provided by a wireless communication system. Typical wireless communication systems provide multiple users with one or more shared resources. For example, a wireless communication system may use various multiple access schemes such as code division multiple access (CDMA), time division multiple access (TDMA), and frequency division multiple access (FDMA). The Institute of Electrical and Electronics Engineers (IEEE) 802.16 standard provides technologies and protocols to support broadband wireless access. Standardization has been in progress since 1999, and IEEE 802.16-2001 was approved in 2001. This is based on a single carrier physical layer called 'WirelssMAN-SC'.

Hereinafter, downlink means communication from the base station to the terminal, and uplink means communication from the terminal to the base station. In general, the base station allocates radio resources to the terminal. Depending on the amount of data stream to be transmitted, the channel state, and the quality of service (Qos), the size of radio resources allocated to the terminal for downlink or uplink transmission may vary. If the amount of data stream is large, many radio resources must be allocated. However, since the size of radio resources is finite, radio resources should be allocated efficiently.

Radio resources allocated to the terminal may be distributed and allocated in the frequency domain or the time domain. Transmitting data through radio resources distributed in the frequency domain is called frequency diversity. Through frequency diversity, fading of a specific frequency band may be dispersed to increase the reception rate of data. Transmitting data through radio resources distributed in the time domain is called time diversity. Time diversity is to transmit the same data multiple times at a time interval, thereby reducing the influence of fading over time to improve the reception rate of the data.

In general, one base station allocates radio resources to a plurality of terminals and provides a communication service. At this time, each terminal may have a different channel gain. That is, frequency bands having good quality may be different for each terminal. A base station can efficiently schedule terminals having different channel gains to increase data transmission rate, which is referred to as multiuser diversity.

In the radio resource allocation method, a localized allocation method (or a local allocation method) for obtaining a channel selectivity gain by allocating some local frequency domains according to channel conditions, and a frequency domain for all bands There is a distributed allocation scheme to obtain frequency diversity gain by providing an average channel state by assigning.

However, since all subcarriers of each frame belong to one permutation zone, local mapping and distributed mapping cannot be used at the same time. On the other hand, in each frame, a user who desires multi-user diversity gain and a user who desires frequency diversity gain coexist. Therefore, there is a need for a flexible data transmission method capable of pursuing respective gains by applying local mapping to the former and distributed mapping to the latter over the entire frequency band.

The present invention provides a method of transmitting data by efficiently multiplexing localized mapping and distributed mapping, which are methods of subcarrier mapping.

According to an aspect of the present invention, a data transmission method using subcarrier mapping is provided. The method comprises the steps of preparing a logical frame, generating a physical frame in which localized and distributed mappings are mixed on the same OFDM symbol, and generating the generated logical frame. Transmitting the physical frame. The local mapping maps a plurality of adjacent subcarriers in the logical frame to a plurality of adjacent subcarriers in the same position on the physical frame, and the distributed mapping maps the subcarriers in the logical frame to subcarriers at any location on the physical frame. Map it.

According to another aspect of the present invention, a data transmission method using subcarrier mapping is provided. The method includes selecting at least one local region in a logical frame, the plurality of distributed subcarriers belonging to a plurality of contiguous local subcarriers and a non-local region in the local region. Allocating the local subcarriers separated from the local area to the same position as the local area of the logical frame on the physical frame, and the distributed subcarriers incorporated into the local area on the non-local area on the physical frame. And mapping to the location of the local subcarrier deviated from the data, and transmitting the physical frame.

Local and distributed mapping can be efficiently performed in all frequency bands at the same time. In local mapping, the existing permutation scheme for the distributed mapping (or allocation) can be used without regard to the offset and size of the mapping.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Like numbers refer to like elements throughout.

1 is a block diagram illustrating a wireless communication system. Wireless communication systems are widely deployed to provide various communication services such as voice and packet data.

Referring to FIG. 1, a wireless communication system includes a user equipment (UE) 10 and a base station 20 (BS). The terminal 10 may be fixed or mobile and may be called by other terms such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), and a wireless device. The base station 20 generally refers to a fixed station that communicates with the terminal 10, and in other terms, such as a Node-B, a Base Transceiver System, or an Access Point. Can be called. One or more cells may exist in one base station 20.

Hereinafter, downlink (DL) means communication from the base station 20 to the terminal 10, and uplink (UL) means communication from the terminal 10 to the base station 20. In downlink, the transmitter may be part of the base station 20 and the receiver may be part of the terminal 10. In uplink, the transmitter may be part of the terminal 10 and the receiver may be part of the base station 20.

The wireless communication system may be an Orthogonal Frequency Division Multiplexing (OFDM) / Orthogonal Frequency Division Multiple Access (OFDMA) based system. OFDM uses multiple orthogonal subcarriers. OFDM uses orthogonality between inverse fast fourier transforms (IFFTs) and fast fourier transforms (FFTs). At the transmitter, data is transmitted by performing an IFFT. The receiver performs FFT on the received signal to recover the original data. The transmitter uses an IFFT to combine multiple subcarriers, and the receiver uses a corresponding FFT to separate multiple subcarriers.

2 shows an example of a logical frame structure. A frame is a sequence of data for a fixed time used by physical specifications. This may be referred to section 8.4.4.2 of the IEEE standard 802.16-2004 "Part 16: Air Interface for Fixed Broadband Wireless Access Systems" (hereafter reference 1).

Referring to FIG. 2, the frame includes a downlink (DL) frame and an uplink (UL) frame. Time Division Duplex is a scheme in which uplink and downlink transmissions share the same frequency but occur at different times. The downlink frame is temporally ahead of the uplink frame. The downlink frame starts with a preamble, a frame control header (FCH), a downlink (DL) -MAP, an uplink (MAP) -MAP, and a burst region. A guard time for distinguishing the uplink frame and the downlink frame is inserted in the middle part (between the downlink frame and the uplink frame) and the last part (after the uplink frame) of the frame. A transmit / receive transition gap (TGT) is a gap between a downlink burst and a subsequent uplink burst. A receive / transmit transition gap (RTG) is a gap between an uplink burst and a subsequent downlink burst.

The preamble is used for initial synchronization, cell search, frequency offset, and channel estimation between the base station and the terminal. The FCH includes the length of the DL-MAP message and the coding scheme information of the DL-MAP.

DL-MAP is an area where a DL-MAP message is transmitted. The DL-MAP message defines the connection of the downlink channel. The DL-MAP message includes a configuration change count of the downlink channel descriptor (DDC) and a base station identifier (ID). DCD describes a downlink burst profile applied to the current map. The downlink burst profile refers to a characteristic of a downlink physical channel, and the DCD is periodically transmitted by the base station through a DCD message.

The UL-MAP is an area in which the UL-MAP message is transmitted. The UL-MAP message defines the access of an uplink channel. The UL-MAP message includes a configuration change count of an uplink channel descriptor (UCD) and a valid start time of uplink allocation defined by UL-MAP. UCD describes an uplink burst profile. The uplink burst profile refers to characteristics of an uplink physical channel, and the UCD is periodically transmitted by the base station through a UCD message.

In the following, a slot is defined as the minimum possible data allocation unit, time and subchannel. The subchannel is a basic unit for dividing frequency resources, and the subchannel includes a plurality of subcarriers. The number of subchannels and the number of OFDM symbols included in one slot differs according to a permutation scheme. Permutation means mapping logical subchannels to physical subcarriers. The permutation scheme in which some subchannels are allocated for data transmission is called Partial Usage of the SubChannels (PUSC), and the permutation scheme in which all subchannels are allocated for data transmission is referred to as all subchannel allocation scheme ( Full Usage of the SubChannels (FUSC).

In downlink, the slot of the FUSC consists of one subchannel and one OFDM symbol, and the slot of the PUSC consists of one subchannel and two OFDM symbols. In the uplink, a slot of a PUSC is composed of one subchannel and three OFDM symbols. On the other hand, the slot of the AMC is composed of one subchannel and three OFDM symbols.

The number of subcarriers included in one subchannel also depends on the permutation scheme (for example, PUSC, FUSC, Band-AMC, Uplink PUSC, Optional PUSC, etc.). In FUSC, a channel contains 48 subcarriers, and in a PUSC, a subchannel contains 24 or 16 subcarriers. A segment refers to at least one subchannel set. The number of subchannels depends on the FFT size and the time-frequency mapping.

In the physical layer, generally two steps are used to map data to physical subcarriers. In a first step, data is mapped to at least one data slot on at least one logical subchannel. In the second step, each logical subchannel is mapped to a physical subcarrier. A set of OFDM symbols in which the same permutation scheme is used is called a permutation zone, and one frame includes at least one permutation region.

FUSC is used for downlink transmission. FUSC is composed of one segment including all subchannel groups. Each subchannel is mapped to a physical subcarrier distributed over the entire physical channel. This mapping changes for each OFDM symbol. A slot consists of one subchannel on one OFDM symbol. O-FUSC differs in how FUSC and pilot are allocated.

PUSC is used for both downlink transmission and uplink transmission. In downlink, each physical channel is divided into a cluster consisting of 14 contiguous subcarriers on 2 OFDM symbols. Physical channels are mapped to six logical groups. Within each group, pilots are assigned to each cluster at fixed locations. In uplink, subcarriers are divided into tiles consisting of four contiguous physical subcarriers on 3 OFDM symbols. The subchannel contains 6 tiles. Pilots are assigned to the edges of each tile. O-PUSC is used only for uplink transmission, and a tile consists of three adjacent physical subcarriers on 3 OFDM symbols. The pilot is assigned to the center of the tile.

FIG. 3 is a block diagram of mapping a logical frame of FIG. 2 to a physical frame for each permutation region. FIG.

Referring to FIG. 3, the downlink frame includes eight permutation zones starting from a preamble region. The permutation region including the FCH and DL-MAP immediately after the preamble region is a region mapped to a subcarrier by the PUSC scheme. The FCH is transmitted in an essential channel coding scheme having a channel coding rate 1/2, a 4-time repetition coding scheme, and a QPSK modulation scheme in the PUSC region. The FCH includes a DL_Frame_Prefix, which defines the length of the DL_MAP message immediately transmitted and the repetitive encoding scheme of the DL_MAP message. The other eight permutation regions except for the peramble region including the preamble, the FCH, and the DL-MAP may be applied with different permutation schemes according to cell conditions.

The uplink frame includes a permutation region of the PUSC scheme, an optional PUSC (PUSC) scheme, and a permutation region of the Adaptive Modulation and Coding (AMC) scheme. The uplink frame may have a different permutation scheme applied to each permutation region according to cell conditions.

The scheduler of the base station may change the permutation scheme applied to each permutation region through a zone switch IE of DL_MAP based on the reported channel state. Here, AMC corresponds to localized allocation for channel selectivity gain, and all other permutation methods except AMC are distributed allocation for frequency diversity gain. Corresponds to

4 is a block diagram illustrating a data transmission method according to a mapping method according to an embodiment of the present invention. Herein, it is assumed that the slot structure (or sub channel structure) to which the local mapping and the distributed mapping are applied is the same.

Referring to Figure 4, first prepare a logical frame. The vertical axis of the first logical frame may consist of subcarriers ordered from index 0 to 31 from the top to the bottom, and the horizontal axis may include at least one OFDM symbol as a time axis. Here, the index given on the frequency axis may be a plurality of subcarrier units or may be a resource element or a resource block. In the following description, it is assumed that an index is indexed on a subcarrier basis for convenience. Resource blocks residing on a logical frame may be mapped to subcarriers of a physical frame, which include local mapping and distributed mapping.

Localized mapping refers to a fixed mapping of a plurality of adjacent subcarriers in a logical frame to a plurality of adjacent subcarriers at the same position on a physical frame, and distributed mapping A subcarrier of a logical frame is distributedly mapped to a subcarrier of an arbitrary position on a physical frame. Local mapping may be called local allocation, and distributed mapping may be called distributed allocation.

Local mapping is a method used to increase the channel selectivity gain and may be used when adaptive modulation and coding (AMC) is applied. On the other hand, distributed mapping is a method used to increase the frequency diversity gain, and may be used when PUSC or FUSC is applied.

The transmitter may select a plurality of adjacent subcarriers to which local mapping is applied in the logical frame. The plurality of adjacent subcarriers selected form a constant region or section, which is called a local region. That is, the local area is selected by the transmitter. The local area may be called a local mapping area. A plurality of adjacent subcarriers included in the local area are called local subcarriers. That is, a local subcarrier is a subcarrier to which local mapping is applied. In the first local area, there are local subcarriers corresponding to the indices 5 through 7, In the second local area, there are local subcarriers corresponding to indices 13 through 16, and in the third local area, there are local subcarriers corresponding to indexes 27 and 28. . These local subcarriers are all fixedly mapped to physical frames at the same location. Depending on how the local subcarrier is selected, the size and position of the local region may vary.

On the other hand, unlike local subcarriers, subcarriers not included in the local region are called distributed subcarriers. That is, a distributed subcarrier is a subcarrier to which distributed mapping is applied, not local mapping. The distributed subcarriers are included in a region other than the local region (hereinafter referred to as a non-local region) and are subcarriers corresponding to indexes 0 to 4, 8 to 12, 17 to 26, and 29 to 31.

As such, the logical frame may be divided into a local area and a non-local area. The local area and the non-local area may be one or plural. The second logical frame is a frame according to the result of totally distributing the local subcarriers and the distributed subcarriers listed in the index order on the first logical frame. This dispersion can be called discributed permutation. The distributed permutation may be performed over all bands or over some bands. Local subcarriers that existed in the local region in the first logical frame are scattered and moved to other local or non-local regions in the second logical frame by dispersion.

Referring to the second logical frame that is the result of the variance in the first logical frame, the first local area is filled with distributed subcarriers with indices 9, 17, and 25. In addition, the second local area is filled with the distributed subcarriers corresponding to the indexes 11, 19, and 4 and the local subcarriers with the index 27 belonging to the third local area. Finally, the third local region is filled with a distributed subcarrier having an index of 30 and a local subcarrier having an index of 7 belonging to the first local region.

On the other hand, the third logical frame is a frame showing the state of returning a plurality of local subcarriers (temporary subcarriers in FIG. 4) temporarily separated from the local area to the local area in the first logical frame. That is, after the local subcarriers belonging to the first to third local regions in the first logical frame temporarily deviate from the local region by distribution, the subcarriers belonging to the local subcarriers to which they originally belonged among the local regions in the third logical frame are returned. To return. For example, a local subcarrier of index 27 belonging to a third local region in a first logical frame is incorporated into a second local region of another local region by distribution, but the local subcarrier of index 27 is originally returned in the third logical frame. Return to the position of the subcarrier corresponding to the original index in the local area third local area.

This is an implementation problem and may use a method of forcibly overwriting local subcarriers in the local area in order to return the local subcarriers to each original local area. In this case, distributed subcarriers or other local subcarriers discarded by overwriting are stored separately.

On the other hand, as the temporary subcarriers return to the original local region, the distributed subcarriers corresponding to the indexes 9, 17, 25, 11, 19, 4, and 30 that were incorporated into the local region of the second logical frame by distribution Move to the location of the dislodged local subcarrier. That is, the distributed subcarriers move back to the position where the local subcarriers deviated in the second logical frame.

Here, comparing the relationship between the first logical frame and the physical frame before the dispersion is performed, all local subcarriers belonging to the local region in the first logical frame are consequently mapped to subcarriers of the same position on the physical frame. That is, the resulting mapped location is fixed. Meanwhile, distributed subcarriers belonging to a non-local region in a first logical frame are mapped to positions of arbitrary subcarriers on a physical frame. Therefore, the physical frame is generated by mixing local mapping and distributed mapping on the same OFDM symbol (or on the time axis). That is, various permutation schemes (PUSC, FUSC, AMC, etc.) are not limited in time and are limited in physical frame, and different permutation schemes may be applied to different subcarriers in the same OFDM symbol and the same frequency band in time. .

The transmitter transmits data by transmitting the mixed physical frames generated as described above to the receiver.

As such, local mapping (or allocation) can be used for existing distributed mapping (or allocation) without regard to the offset and size of the mapping, which should be considered for every transmission time unit (assuming OFDM symbol here). There is an advantage that can be adopted as it is a hydrothermal method. That is, according to the size of the local mapping, it is not necessary to create a distributed mapping sequence as many as in each case, and there is no need to complicatedly modify the distributed mapping permutation scheme for the local mapping.

5 is a block diagram illustrating a data transmission method according to a mapping method according to another example of the present invention.

Referring to FIG. 5, after the distribution is performed as in FIG. 4, distributed subcarriers having indexes 9, 17, 25, 11, 19, 4, and 30 are incorporated into the local region of the third logical frame. However, as local subcarriers return to the local region, the distributed subcarriers are mapped to a non-local region on a physical frame. However, unlike the index order of the distributed subcarriers (9, 17, 25, 11, 19, 4, 30), the order in which the distributed subcarriers are mapped to the physical frame is again permutated to optimize the transmission performance of the cell (cell specific permutation). As a result of permutation, the index order of the distributed subcarriers in which the distributed subcarriers are mapped to the physical frames is 17, 30, 11, 4, 9, 19, and 25.

Looking at the indexes of subcarriers mapped to physical frames, adjacent local subcarriers with indexes 5, 6, and 7 in the first local region (local mapping region), adjacent local subcarriers with indices 13 through 16 in the second local region, and third In the local region, adjacent local subcarriers of indexes 27 and 28 are mapped. On the other hand, distributed subcarriers having indexes 17, 30, 11, 4, 9, 19, and 25 are mapped in order from the top of the physical frame to a portion where the local subcarriers are located in the original logical frame among the non-local regions.

The transmitter transmits data by transmitting a physical frame generated by the above method.

In the prior art distributed mapping permutation method, there are considerations for minimizing interference of adjacent cells. For example, the FUSC method is set to a pattern in which resource elements are spread at regular intervals over the entire band. The FUSC method shifts the pattern using an offset considering a cell unique number (Cell_ID) to maximize each other. Do not overlap. If the size of resource elements to which distributed mapping is applied is changed due to local mapping, this constant pattern changes from cell to cell, so the number of cases of overlapping with resource elements of adjacent cells using the same permutation method increases.

The present invention can offset the impact on local mapping while maintaining the pattern as much as possible. Accordingly, the present invention efficiently compensates for the disadvantage that the local mapping and the distributed mapping are separated in time and the resource mapping flexibility falls, thereby efficiently performing the local and distributed mapping in all frequency bands at the same time. I could do it.

6 is a block diagram illustrating a data transmission method according to a mapping method according to another embodiment of the present invention.

Referring to FIG. 6, after dispersion is performed, distributed subcarriers corresponding to indexes 9, 17, 25, 11, 19, 4, and 30 of the third logical frame are mapped to a non-local region on a physical frame. The first unit time maps the distributed subcarriers to the physical frames in the index order, and the second unit time maps the distributed subcarriers again to the physical frames. The index order of the distributed subcarriers distributed in the second unit time is 19, 4, 30, 9, 17, 25, and 11. The transmitter transmits data by transmitting a physical frame generated by the above method. By dispersing the distributed subcarriers not only on the frequency axis but also on the time axis, intercell interference cancellation and cell transmission performance can be optimized.

Looking at the indexes of subcarriers mapped to physical frames, adjacent local subcarriers with indexes 5, 6, and 7 in the first local region (local mapping region), adjacent local subcarriers with indices 13 through 16 in the second local region, and third In the local region, adjacent local subcarriers of indexes 27 and 28 are mapped. On the other hand, distributed subcarriers having indexes 17, 30, 11, 4, 9, 19, and 25 are mapped to the portion of the non-local region where the local subcarriers were originally located in the logical frame from the top of the physical frame.

All of the above functions may be performed by a processor such as a microprocessor, a controller, a microcontroller, an application specific integrated circuit (ASIC), or the like according to software or program code coded to perform the function. The design, development and implementation of the code will be apparent to those skilled in the art based on the description of the present invention.

Although the present invention has been described above with reference to the embodiments, it will be apparent to those skilled in the art that the present invention may be modified and changed in various ways without departing from the spirit and scope of the present invention. You will understand. For example, OFDMA symbol offsets, subchannel offsets, slot time offsets, etc. may be given based on a specific point other than the starting point of the preamble or permutation zone, which is assigned whenever a resource region of each frame is allocated. It may be set differently. In addition, the resource zone may be allocated based on the end point of the resource zone as well as the start point of the resource zone. Therefore, the present invention is not limited to the above-described embodiment, and the present invention will include all embodiments within the scope of the following claims.

1 is a block diagram illustrating a wireless communication system.

2 shows an example of a logical frame structure.

FIG. 3 is a block diagram of mapping a logical frame of FIG. 2 to a physical frame for each permutation region. FIG.

4 is a block diagram illustrating a data transmission method according to a mapping method according to an embodiment of the present invention.

5 is a block diagram illustrating a data transmission method according to a mapping method according to another example of the present invention.

6 is a block diagram illustrating a data transmission method according to a mapping method according to another embodiment of the present invention.

Claims (11)

Preparing a logical frame; Generating a physical frame in which localized mapping and distributed mapping are mixed on the same OFDM symbol; And Transmitting the generated physical frame, The local mapping maps a plurality of adjacent subcarriers in the logical frame to a plurality of adjacent subcarriers in the same position on the physical frame, and the distributed mapping maps the subcarriers in the logical frame to subcarriers at any location on the physical frame. Mapping, data transmission method. The method of claim 1, The logical frame is time-divided uplink and downlink. The method of claim 1, The logical frame includes a preamble, a map (MAP) and a burst area, the preamble matches synchronization, the map defines a connection of the burst area, and the burst area is downward A data transmission method comprising link or uplink data. The method of claim 1, The local mapping is a data transmission method, which is a mapping method when AMC (Adaptive Modulation and Coding) is applied. The method of claim 1, The distributed mapping is a mapping method when a PUSC (Partial Usage of SubChannel) is applied. The method of claim 1, The distributed allocation method is a mapping method when a full usage of subchannel (FUSC) is applied. Selecting at least one local region in the logical frame; Distributing a plurality of contiguous local subcarriers in the local region and a plurality of distributed subcarriers belonging to a non-local region in the logical frame; Mapping a local subcarrier deviating from the local area to a same position as a local area of the logical frame on a physical frame; Mapping a distributed subcarrier incorporated into the local region to a location of the local subcarrier separated from the non-local region on the physical frame; And Transmitting the physical frame. The method of claim 7, wherein And said distributed local subcarrier is mapped onto said physical frame at the same location as said location on said logical frame before being distributed. The method of claim 7, wherein And the distributed distributed subcarriers are mapped to the non-local region on the physical frame in the order of movement to the local region by the dispersion. The method of claim 7, wherein The distributed distributed subcarriers are mapped to the non-local region on the physical frame regardless of the order in which the distributed subcarriers are moved to the local region by the dispersion. The method of claim 10, The distributed distributed subcarriers are mapped to the non-local region on the physical frame according to a resource allocation method for reducing inter-cell interference.

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