WO2007059706A1

WO2007059706A1 - A method and device for dft-spread ofdm

Info

Publication number: WO2007059706A1
Application number: PCT/CN2006/003141
Authority: WO
Inventors: Xuezhi Yang
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2005-11-24
Filing date: 2006-11-22
Publication date: 2007-05-31
Also published as: CN1972267A

Abstract

A method and device for DFT-Spread OFDM include: The main sub-carrier group of a cell transmit user data to the user which are in the boundary of the cell, and the main sub-carrier group and/or the minor sub-carrier group of cell transmit user data to the user which are not in the boundary of cell; wherein the main sub-carrier group of the cell is allocated from the multiple sub-carrier group of DFT-Spread OFDM access system, and the main sub-carrier groups of the respective adjacent cells are different each other, the minor sub-carrier groups of a cell are the predetermined sub-carrier groups other than the main sub-carrier group of the cell. The frequency band of the different sun-carrier group are not overlap each other, or the frequency band of the different sun-carrier group are partially overlap. By the main sub-carrier group of cell transmit user data to the user which are in the boundary of cell, it effectively solves the problem about the interfere of the adjacent cell boundary; by the main sub-carrier group and/or the minor sub-carrier group of cell transmit user data to the user which are not in the boundary of cell, allowing that the multiplexing factor of DFT-Spread OFDM access system is 1; thereby lowering the interfere of cell boundary, improving the availability of multiple cell frequency-spectrum.

Description

Discrete Fourier transform spread spectrum orthogonal frequency division multiplexing method and device

The present invention relates to the field of network communication technologies, and in particular, to a discrete Fourier transform spread spectrum orthogonal frequency division multiplexing method and a discrete Fourier transform spread spectrum orthogonal frequency division multiplexing device. Background of the invention

Next-generation mobile communication technologies need to support a wide range of services such as voice, data, audio, video, and images. In order for next-generation communication systems to support the above-mentioned multiple services, next-generation mobile communication systems must be required to support more advanced data rates and more.频谱 Spectrum efficiency, complete QOS guarantee mechanism, and provide better mobility support and seamless network coverage, thus achieving the goal of providing communication services to users anytime and anywhere.

The second generation mobile communication uses GSM (Global System for Mobile Communications) TDMA (Time Division Multiple Access) and narrowband IS-95 CDMA (Code Division Multiple Access) system as the main access technologies, and third generation mobile communication with UMTS (Universal Mobile Communication System) Continued) WCDMA (Wideband CDMA) is the primary access technology.

Since the 1990s, multi-carrier technology has become a hotspot technology for broadband wireless communication. The basic idea is to divide the wideband carrier into multiple subcarriers and transmit data simultaneously on multiple subcarriers. Multi-carrier technology can take many forms, such as OFDMA (Orthogonal Frequency Division Multiple Access), MC-CDMA (Multi-Carrier Code Division Multiple Access), MC-DS-CDMA (Multi-Carrier Direct Spread Code Division Multiple Access), Time-frequency domain two-dimensional expansion and a variety of extension techniques based on this.

QFDM (Orthogonal Frequency Division Multiplexing) technology is a relatively representative technology among multi-carrier technologies. OFDM technology divides a given channel into many orthogonal sub-channels in the frequency domain, and allows partial sub-carrier spectrum overlap. The data signals can be separated from the aliased subcarriers as long as the subcarriers are orthogonal to each other.

Because OFDM technology is a multi-carrier parallel transmission technology, the PAR (peak-to-average ratio) of the signal is much larger than that of the single-carrier transmission system. Therefore, the hardware of the OFDM communication system will be greatly stressed, such as D/. The effective word length of the A converter, the effective word length of the A/D converter, the linear dynamic range of the power amplifier, and so on. In order to effectively reduce the peak-to-average ratio of the ^:signal signal, especially in order to reduce the hardware pressure of the UE (user terminal), some novel transmission technologies have emerged in recent years, such as DFT-Spread OFDM (Discrete Fourier Transform Spread Spectrum Orthogonal Frequency) Sub-multiplexing), IFDMA (Interleaved Frequency Division Multiple Access), etc.

The access method and access device based on the IFDMA access system are as shown in FIG.

In Figure 1, at the transmitting end, the user's data is first subjected to data grouping, such as every Q data symbols are grouped into one IFDMA symbol period. Then, performing time domain compression and time domain repetition on the Q data symbols, and adding The guard interval is used to overcome interference between symbols caused by multipath channels. After the user's data symbols are frequency modulated and shaped filtered, they are modulated and transmitted. At the receiving end, after the received signal is subjected to carrier demodulation and waveform matching filtering, the user frequency is demodulated, and the guard interval is removed, and finally, signal detection is performed.

The IFDMA-based access system is a special case based on the DFT-Spread OFDM access system, that is, the IFDMA-based access system is also a DFT-Spread OFDM access system.

As can be seen from the above description of Fig. 1, the frequency modulation based on the IFDMA access system corresponds to each user, that is, different users correspond to different frequency modulations, thereby implementing frequency division multiple access. The interleaved frequency division multiple access scheme can be considered as a single-carrier signal transmission scheme, which can effectively reduce the peak-to-average ratio of the signal at the transmitting end, but the method can cause boundary interference of adjacent cells.

The access method and access device based on the DFT-Spread OFDM access system are as shown in FIG. 2. In Figure 2, at the transmitting end, the user's data is subjected to DFT/FFT (Discrete Fourier Transform or Fast Fourier Transform) operation after serial-to-parallel conversion, and the frequency is mapped to different subcarriers, after IDFT/IFFT (inverse discrete Fourier) After the transform or inverse fast Fourier transform operation, the user's data is subjected to parallel-to-serial conversion, and a guard interval is added to overcome the intersymbol interference caused by the multipath channel. Then, the user's data symbols are subjected to shaping and filtering, and then subjected to carrier modulation. And launch. At the receiving end, after the received signal is subjected to carrier demodulation and waveform matching filtering, the guard interval is removed and signal detection is performed.

The discrete Fourier transform spread spectrum orthogonal frequency division multiplexing scheme, like the interleaved frequency division multiple access scheme, can be considered as a single carrier signal transmission scheme, which can effectively reduce the peak-to-average ratio of the signal at the transmitting end, however, This method also causes boundary interference of neighboring cells.

In the multi-cell cellular system, in order to reduce the boundary interference of the neighboring cells, an effective multi-cell networking scheme may be adopted to implement frequency division multiplexing access, that is, each adjacent cell corresponds to a different frequency band, that is, a frequency is adopted. The way the packet network is. The networking scheme effectively reduces the boundary interference of neighboring cells, and also reduces the spectrum utilization efficiency of the multi-cell system. Summary of the invention

The discrete Fourier transform spread spectrum orthogonal frequency division multiplexing method and device provided by the embodiments of the present invention use the soft frequency multiplexing method of the primary subcarrier group and the secondary subcarrier group to reduce the boundary interference of the cell and improve the utilization of the multi-cell spectrum. effectiveness.

To achieve the above objective, a discrete Fourier transform spread spectrum orthogonal frequency division multiplexing method provided by an embodiment of the present invention includes: Transmitting user data for a user at a cell boundary by using a primary subcarrier group of the cell, and transmitting user data for a user at a non-cell boundary by using a primary subcarrier group and/or a secondary subcarrier group of the cell;

Wherein: the primary subcarrier group of the cell is allocated from multiple subcarrier groups of the discrete Fourier transform spread spectrum orthogonal frequency division multiplexing access system, and the primary subcarrier groups of each neighboring cell are different from each other, and the secondary subcarrier of the cell The group is a predetermined subcarrier group other than the primary subcarrier group of the cell.

The embodiment of the present invention further provides a discrete Fourier transform spread spectrum orthogonal frequency division multiplexing device, including: a transmitting unit: transmitting user data for a user at a cell boundary through a primary subcarrier group of a cell, and adopting a secondary subcarrier group of the cell And/or a primary subcarrier group transmitting user data for users at non-cell boundaries;

'where: the primary subcarrier group of the cell is allocated from multiple subcarrier groups of the discrete Fourier transform spread spectrum orthogonal frequency division multiplexing access system, and the primary subcarrier groups of the neighboring cells are different from each other, and the secondary of the cell The subcarrier group is a predetermined subcarrier group other than the primary subcarrier group of the cell. According to the description of the foregoing technical solution, the embodiment of the present invention divides a predetermined frequency band into a plurality of subcarrier groups whose frequencies do not overlap or partially overlap, so that main subcarrier groups of different neighboring cells are different from each other, and the multiplexing device utilizes the primary sub-carrier. The carrier group transmits the user data for the user at the cell boundary, which effectively solves the problem of the neighboring cell boundary interference. The embodiment of the present invention uses a predetermined subcarrier group other than the primary subcarrier group in the predetermined frequency band as the secondary subcarrier of the cell. The multiplexing device transmits the user data to the user at the non-cell boundary by using the secondary subcarrier group and/or the primary subcarrier group, so that the multiplexing factor of the discrete Fourier transform spread spectrum orthogonal frequency division multiplexing access system is 1; Therefore, the technical solution provided by the invention achieves the purpose of reducing cell boundary interference and improving multi-cell spectrum utilization efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

1 is a schematic diagram of an access method and an access device based on an IFDMA access system in the prior art;

2 is a schematic diagram of an access method and an access device of a DFT Spread OFDM access system according to the prior art; FIG. 3 is a schematic diagram of a discrete Fourier transform spread spectrum orthogonal frequency division multiplexing access method according to an embodiment of the present invention; Is a schematic diagram of a discrete Fourier transform spread spectrum orthogonal frequency division multiplexing access device according to an embodiment of the present invention. Mode for carrying out the invention

In an embodiment of the present invention, a discrete Fourier transform spread spectrum orthogonal frequency division multiplexing access system is provided with a plurality of subcarrier groups. Each of the neighboring cells is allocated a subcarrier group different from each other, and the mutually different subcarrier groups allocated by the neighboring cells are used as the primary subcarrier group of the cell. Each cell is also configured with a secondary subcarrier group, and the secondary subcarrier group of one cell is: a predetermined subcarrier group of all subcarrier groups except the primary subcarrier group of the cell. Scheduled sub-load here The wave group may be all subcarrier groups except the primary subcarrier group of the cell in all subcarrier groups, or may be a partial subcarrier group other than the primary subcarrier group of the cell in all subcarrier groups. When the user data needs to be transmitted, the discrete Fourier transform spread spectrum orthogonal frequency division multiplexing access device transmits user data to the user at the boundary of the cell through the primary subcarrier group of the cell, and passes through the primary subcarrier group and/or the secondary subgroup of the cell. The carrier group transmits user data for users at non-cell boundaries.

The technical solutions provided by the embodiments of the present invention are further described below.

The embodiment of the present invention provides a single-frequency cell networking scheme applicable to the DFT-Spread OFDM access system and the IFDMA access system, and the discrete Fourier transform spread spectrum orthogonal frequency division multiplexing (DFFT) mentioned in the embodiment of the present invention includes - DFT -Spread OFDM and IFDMA, the basic implementation principle is as follows: All subcarriers in a predetermined frequency band in the access system, such as all subcarriers in a frequency band, are divided into multiple subcarrier groups, the number of subcarrier groups and adjacent The number of cells corresponds to each other. The frequency bands included in different subcarrier groups may not overlap each other or may partially overlap. Each of the neighboring cells selects one of the subcarrier groups as the primary subcarrier group of the current cell, and the selected subcarrier groups of the neighboring cells should be different, that is, the frequency bands of the primary subcarrier groups of different neighboring cells are different or different adjacent. The frequency bands of the primary subcarrier group of the cell are only partially identical. All or part of the frequency bands except the primary subcarrier group in all frequency bands of the access system are used as the secondary subcarrier group of the current cell. The above networking mode implements soft frequency multiplexing.

After the primary subcarrier group and the secondary subcarrier group are set for each neighboring cell, the multiplexed access device should transmit the user data to the user at the boundary of the cell through the primary subcarrier group, and pass the secondary subcarrier group or the primary subcarrier. The group, or the secondary subcarrier group and the primary subcarrier group transmit data of the user for the user who is not in the boundary of the current cell, and the transmission power of the primary subcarrier group should be higher than the transmission power of the secondary subcarrier group, so that although the neighboring cells are between The high transmit power is used to transmit the user's data to the user at the cell boundary. However, since the frequency bands of the primary subcarrier groups between adjacent cells are completely different, or only some of the frequency bands are the same, the neighboring cells are effectively reduced. Boundary interference. Since the secondary subcarrier group of each neighboring cell is all frequency bands except the primary subcarrier group, the frequency reuse factor of the access system is 1, and the spectrum utilization efficiency of the multicell is improved.

The multiplexed access device can transmit different user data through different subcarrier groups by setting different transmit power adjustment coefficients for the transmit power of different user data. The discrete Fourier transform spread spectrum of the embodiment of the present invention is described below with reference to FIG. The orthogonal frequency division multiplexing access method will be described in detail.

In Figure 3, the multiplexed access device needs to transmit data of N users, and each user's data needs to be serial-to-parallel converted, and the serial-converted user data needs to perform DFT or FFT operations; after DFT or FFT operation The data of each user needs to be adjusted according to their respective corresponding transmit power adjustment coefficients; the multiplexed access device can set the transmit power adjustment coefficient corresponding to each user's data according to a predetermined power adjustment policy, and the power adjustment policy The specific content may be various existing strategies, such as the multiplexing access device setting the transmission power adjustment coefficient corresponding to the data of each user according to the path loss, and the like. A specific example of the multiplexed access device adjusting the transmit power of each user's data according to the transmit power adjustment coefficient corresponding to each user's data is: The multiplexed access device will pass

The data of each user after the DFT or FFT operation is multiplied by its corresponding transmit power adjustment coefficient to achieve the transmit power adjustment. The user data after the adjustment of the transmit power is frequency mapped and mapped to the corresponding primary subcarrier group or the secondary subcarrier group. At this time, the adjustment of the transmit power by the transmit power adjustment coefficient should enable the bearer to bear the user data at the cell boundary. The carrier is mapped to the primary subcarrier group, and the carrier carrying the user data at the non-cell boundary is mapped to the secondary subcarrier group or the primary subcarrier group. The frequency mapped signal needs to be IDFT or IFFT transformed. The multiplexed access device performs parallel-to-serial conversion on the IDFT or IFFT transformed signal. The multiplexed access device adds a guard interval to the converted signal; the multiplexed access device performs low-pass filtering, D/A conversion on the signal after adding the guard interval, and then multiplexes the access device to D/A conversion The latter signal is subjected to carrier modulation. Finally, the multiplexed access device transmits the carrier modulated signal to the incident channel.

_.,;. Each user data the user data after the described process of Figure 3, the serial-parallel conversion may be performed to adjust transmit power first, and then re-DFT or FFT operation, i.e. parallel converter are required in accordance with their respective The corresponding transmit power adjustment coefficient is used to adjust the transmit power, and the multiplex access device sets the transmit power adjustment coefficient corresponding to the data of each user according to a predetermined power adjustment policy. A specific example of the multiplexed access device adjusting the transmit power of each user's data according to the transmit power adjustment coefficient corresponding to each user's data is: The multiplexed access device multiplies the data of each user after the DFT or FFT operation. The corresponding transmit power adjustment coefficient is used to achieve the transmit power adjustment. The DFT or FFT operation is performed on each user data adjusted by the transmission power; the multiplexed access device performs frequency mapping on the data of each user after the DFT or FFT operation, and maps to the corresponding primary subcarrier group or the secondary subcarrier group. The other processing is the same as described in FIG.

In the foregoing description of FIG. 3, the user data transmission power adjustment process may also be performed before the serial-to-parallel conversion, that is, the multiplexed access device adjusts the transmit power of each user's data according to the transmit power adjustment coefficient corresponding to each user's data. The user data after the adjustment of the transmission power is further subjected to serial-to-parallel conversion, and then the user data of the serial-to-parallel conversion is subjected to DFT or FFT operation, and the data of each user after DFT or FFT operation is frequency-mapped and mapped to corresponding Primary subcarrier group or secondary subcarrier group. The other processing is the same as described in Figure 3.

The discrete Fourier transform spread spectrum orthogonal frequency division multiplexing access device according to the embodiment of the present invention will be described in detail below with reference to FIG.

The multiplexing device in Figure 4 is a multiplexed access device. The multiplexed access device needs to transmit data of N users, and the serial-to-parallel converter performs serial-to-parallel conversion on each user's data; the user data outputted by the serial-to-parallel converter is sent to the DFT or FFT. The converter performs DFT or FFT operation; the power control unit and the power threshold control logic of the multiplexed access device adjust the transmit power of each user's data after DFT or FFT operation according to their respective transmit power adjustment coefficients; power threshold The control logic sets the transmit power adjustment coefficient corresponding to the data of each user according to a predetermined power adjustment policy, and the power control unit adjusts the transmit power of each user data according to the transmit power adjustment coefficient corresponding to the data of each user set by the power threshold control logic. For example, the power control unit multiplies the data of each user after the DFT or FFT operation by its corresponding transmit power adjustment coefficient to perform the transmit power adjustment. The frequency mapping unit performs frequency mapping on each user data adjusted by the transmission power, and maps each user data to a corresponding primary subcarrier group or a secondary subcarrier group. At this time, the frequency mapping unit should enable the user data of the bearer at the cell boundary. The carrier is mapped to the primary subcarrier group, so that the carrier carrying the user data at the non-cell boundary is mapped to the secondary subcarrier group or the primary subcarrier group.

The IDFT/IFFT converter performs IDFT or IFFT conversion on the frequency mapped signal. The signal output from the IDFT/IFFT converter is fed to the parallel-to-serial converter for parallel-to-serial conversion. The parallel-serial converter sends the parallel-serialized signal to the add-protection interval module, and the guard interval module adds a guard interval to the parallel-converted signal; the signal after adding the guard interval is sent to the low-pass filter for low-pass The filtered and low-pass filtered signal is sent to the D/A converter for D/A conversion. Then, the D/A converted signal is sent to the carrier adjustment module for carrier modulation. Finally, the carrier-modulated signal is sent to the transmit channel. . '

The above frequency mapping unit, IDFT/IFFT converter, parallel to serial converter, add protection interval module, low pass filter, D/A converter, and carrier adjustment module are specific implementations of the transmission submodule.

In the above description of FIG. 4, the user data outputted by the serial-to-parallel converter can also be adjusted first, and then DFT or FFT operation, that is, each user data output by the serial-to-parallel converter needs to be corresponding according to its respective The transmit power adjustment coefficient is used to adjust the transmit power, and the power threshold control logic sets the transmit power adjustment coefficient corresponding to the data of each user according to a predetermined power adjustment policy, and the power control unit transmits the data corresponding to each user according to the power threshold control logic. The power adjustment coefficient adjusts the transmission power of each user's data output by the serial-to-parallel converter. For example, the power control unit multiplies the serial-to-converted data of each user by its corresponding transmission power adjustment coefficient to perform transmission power adjustment. The DFT or FFT converter performs DFT or FFT operation on each user data output by the power control unit; the frequency mapping unit performs frequency mapping on the data of each user output by the DFT or the FFT converter, and maps to the corresponding primary subcarrier group or subcarrier group. The other processing is the same as described in Figure 4.

In the above description of FIG. 4, the user data transmission power adjustment process may also be performed before the serial-to-parallel conversion, that is, the data of each user according to the transmission power adjustment coefficient corresponding to the data of each user set by the power threshold control logic. Performing transmit power adjustment, the serial-to-parallel converter performs serial-to-parallel conversion on the user data after the transmit power adjustment, and then the DFT or FFT converter performs DFT or FFT operation on each user data output by the serial-to-parallel converter. The frequency mapping unit performs frequency mapping on the data of each user output by the DFT or the FFT converter, and maps to the corresponding primary subcarrier group or secondary subcarrier group. Other processing procedures are the same as those described in FIG.

While the invention has been described by the embodiments of the present invention, it will be understood that The invention is also applicable to other multiplexing processes, and the claims of the present invention include such variations and modifications.

Claims

Rights request

A discrete Fourier transform spread spectrum orthogonal frequency division multiplexing method, comprising: transmitting a user data to a user at a cell boundary through a primary subcarrier group of a cell, and passing through a primary subcarrier group and/or a pair of the cell The subcarrier group transmits user data for users at non-cell boundaries;

2. The method according to claim 1, wherein the frequency bands of different subcarrier groups do not overlap each other, or the frequency bands of different subcarrier groups partially overlap.

3. The method according to claim 1 or 2, wherein the method comprises:

Setting a transmit power adjustment coefficient for each user data that needs to be transmitted according to a power adjustment strategy;

Transmitting the transmit power adjustment coefficients to adjust different user data transmission powers, and mapping the user data after adjusting the transmit power to the primary subcarrier group and/or the secondary subcarrier group;

User data is transmitted to the user through the subcarrier group and/or the subcarrier group.

The method of claim 3, wherein the adjusting the transmit power and mapping comprises: performing a discrete Fourier transform or a fast Fourier transform on the user data after the serial-to-parallel conversion;

Adjusting the transmit power of the user data after the discrete Fourier transform or the fast Fourier transform according to the respective transmit power adjustment coefficients, and mapping the user data after adjusting the transmit power to the primary subcarrier group and/or the secondary subcarrier group.

The method according to claim 3, wherein: the process of adjusting transmit power and mapping comprises: adjusting transmit power of user data according to each transmit power adjustment coefficient, and performing string data of power adjustment And converting, converting the serial-converted user data into a discrete Fourier transform or a fast Fourier transform, and mapping the user data to the primary subcarrier group and/or the secondary subcarrier group; or adjusting the string according to the respective transmit power adjustment coefficients The transmit power of the converted user data is subjected to discrete Fourier transform or fast Fourier transform of the power adjusted user data, and mapped to the primary subcarrier group and/or the secondary subcarrier group.

The method according to claim 3, wherein the step of transmitting user data for the user by using the subcarrier group and/or the subcarrier group comprises:

The user data mapped to different subcarrier groups is subjected to inverse discrete Fourier transform or inverse fast Fourier transform, parallel-serial conversion, and transmitted after low-pass filtering, D/A conversion, and carrier modulation.

The method of claim 6, wherein the method further comprises:

A guard interval is added to the parallel-converted user data.

8. A discrete Fourier transform spread spectrum orthogonal frequency division multiplexing device, characterized in that a transmitting unit: transmitting user data for a user at a cell boundary by using a primary subcarrier group of the cell, and transmitting user data for a user at a non-cell boundary by using a secondary subcarrier group and/or a primary subcarrier group of the cell;

The device according to claim 8, wherein the transmitting unit comprises: power threshold control logic: setting a transmit power adjustment coefficient for each user data that needs to be transmitted according to a power adjustment policy;

a transmitting module: adjusting transmit power of different user data according to each transmit power adjustment coefficient, and mapping to a primary subcarrier group and/or a secondary subcarrier group, and then, by using the subcarrier group and/or the subcarrier group The user transmits user data.

The device according to claim 9, wherein the transmitting module comprises: a serial-to-parallel converter for serial-to-parallel conversion of user data, and a DFT/FFT for performing discrete Fourier DFT or fast Fourier FFT transform on user data. a converter, a power control unit that adjusts a transmit power of the user data according to a transmit power adjustment coefficient, a transmit submodule that maps the user data to the primary subcarrier group and/or the secondary subcarrier group and transmits the same;

The process of transmitting the user data by the transmitting module is: the serial-to-parallel converter serially converts the user data received by the serial-to-parallel converter, and the DFT/FFT converter performs DFT or FFT conversion on the serial-converted user data, and the power control unit The transmit power adjustment coefficient adjusts the transmit power of the DFT or FFT-transformed user data, and the transmit sub-module maps the user data after adjusting the transmit power to the primary subcarrier group and/or the secondary subcarrier group, and transmits; or

The process of transmitting the user data by the transmitting module is: the power control unit adjusts the transmit power of the user data according to the received transmit power adjustment coefficient, and the serial-to-parallel converter performs serial-to-parallel conversion of the power-adjusted user data, DFT/FFT The converter performs DFT or FFT transformation on the serial-converted user data, and the transmitting sub-module maps the DFT or FFT-transformed user data to the primary subcarrier group and/or the secondary subcarrier group, and transmits; or

The process of transmitting the user data by the transmitting module is: the serial-to-parallel converter serially converts the user data received by the serial-to-parallel converter, and the serial-to-parallel converter adjusts the transmit power of the serialized and converted user data according to the transmit power adjustment coefficient, DFT The /FFT converter performs DFT or FFT transformation on the serial-to-converted user data, and the transmitting sub-module maps the DFT or FFT-transformed user data to the primary subcarrier group and/or the secondary subcarrier group, and transmits.