WO2012136105A1

WO2012136105A1 - Orthogonal frequency division multiplexing technology-based method and device for transmitting and receiving data

Info

Publication number: WO2012136105A1
Application number: PCT/CN2012/072836
Authority: WO
Inventors: 任大孟; 耿鹏; 李�杰; 张玉婷
Original assignee: 中兴通讯股份有限公司; 李明明
Priority date: 2011-04-07
Filing date: 2012-03-22
Publication date: 2012-10-11
Also published as: CN102790736B; CN102790736A

Abstract

Disclosed are an OFDM technology-based method and device for transmitting and receiving data. In the method, when transmitting data, a maximum sampling rate supported by a data transmission system is determined on the basis of the number of antennae in the data transmission system, of the data width, and of the optical fiber transmission capacity of the data transmission system; the maximum length of an IFFT/FFT is determined on the basis of the maximum sampling rate determined; a value is selected within the interval between the number of sub-carriers and the maximum length as length information of the IFFT/FFT; and the IFFT and the FFT are performed on the basis of the length information. This allows for effectively reduced sampling rate for the system, thus ensuring that the data transmission speed of the optical fiber does not exceed the transmission capacity of the optical fiber, and achieving the goal of conserving equipment costs.

Description

Data transmission and reception method and device based on orthogonal frequency division multiplexing technology

The present invention relates to the field of wireless communication technologies, and in particular, to an orthogonal frequency division multiplexing

(Method and apparatus for transmitting and receiving data of Orthogonal Frequency Division Multiplexing, OFDM) technology. Background technique

With the continuous development of mobile cellular technology, broadband technology and multimedia technology, voice services and low-speed data services have been unable to meet the needs of users. Therefore, in order to better serve users, a variety of value-added services have been developed, such as multimedia multimedia messaging, games, mobile video, television services, etc. These broadband services are generally transmitted through high-speed transmission technology OFDM technology.

The key to adopting OFDM technology is modulation and demodulation, and modulation and demodulation are implemented by inverse Fourier transform and Fourier transform, respectively. In order to reduce the computational complexity of modulation and demodulation in OFDM systems, Inverse Fast Fourier Transform (IFFT) and Fast Fourier Transform (FFT) are used instead of Fourier Inverse. Inverse Discrete Fourier Transform (IDFT) and Discrete Fourier Transform (DFT), and usually the length N of the IFFT/FFT is 2 ⁿ (n is a positive integer).

When using OFDM technology, if the number of subcarriers M is smaller than the length N of the IFFT/FFT, when performing IFFT/FFT at point N, it is necessary to supplement N-M 0s in the frequency domain, and then perform N points.

IFFT/FFT. If f is the subcarrier spacing at this time, the relationship between the sampling rate of the OFDM system and N is as shown in the formula (1). It can be seen from equation (1) that the sampling rate of the OFDM system is proportional to the length of the IFFT/FFT. Therefore, the use of IFFT/FFT in the OFDM system reduces the computational complexity of modulation and demodulation, but increases the system sampling rate. For example, for a Long Term Evolution (LTE) system with a bandwidth of 20 MHz, the number of subcarriers is 1200, and the length of the IFFT/FFT is 2048. Compared to the IDFT/DFT with a length of 1200, the IFFT/FFT with a length of 2048 is used to make the system sample rate. Increased by 70.67%.

For a base station system using a distributed structure in which the baseband portion and the radio frequency portion are connected by optical fibers, an excessive system sampling rate may cause the OFDM baseband data rate transmitted on the optical fiber connecting the baseband portion and the radio frequency portion to exceed the transmission of the optical fiber. capacity.

In order to prevent the data rate transmitted on the fiber from exceeding the transmission capacity of the fiber, the number of fibers can be increased or the data bit width can be reduced. However, increasing the number of fibers increases equipment and maintenance costs, while reducing the data width reduces system performance. Summary of the invention

In view of this, the embodiments of the present invention provide a data transmission and reception method and apparatus based on OFDM technology, which are used to solve the data transmission in a base station of a distributed structure, and the data rate transmitted on the optical fiber may exceed the transmission capacity of the optical fiber. The problem.

According to an aspect of the embodiments of the present invention, the present invention provides a data transmission method based on OFDM technology, where the method includes:

Mapping the frequency domain to be transmitted data to the input of the inverse fast Fourier transform IFFT;

The IFFT processing is performed according to the length information of the IFFT, wherein the determining process of the length information of the IFFT includes: determining a maximum sampling rate supported by the data transmission system according to the number of antennas of the data transmission system, the data bit width, and the optical fiber transmission capacity of the data transmission system. Determining a maximum length of the IFFT according to the determined maximum sampling rate, and selecting a value in the interval determined by the number of subcarriers and the maximum length as the length information of the IFFT;

The length of the cyclic prefix is determined according to the stored length information of the IFFT, and the cyclic prefix of the length is added to the IFFT processed data to obtain OFDM time domain baseband data and transmitted. Further, determining the maximum length of the IFFT includes:

Determining the product of the number of antennas of the data transmission system and the data bit width;

The maximum sampling rate supported by the data transmission system is determined based on the fiber transmission capacity of the data transmission system and the quotient of the product.

According to the quotient of the maximum sampling rate supported by the data transmission system and the system subcarrier spacing,

The maximum length of the IFFT.

Further, the selecting a value in the interval determined by the number of subcarriers and the maximum length, as the length information of the IFFT, specifically includes:

In the interval in which the number of subcarriers and the maximum length are determined, a value suitable for the base 2, base 3, base 4, or mixed base IFFT operation is selected;

The IFFT computational complexity of each value is compared, and then the least calculated value is selected as the length information of the IFFT. According to another aspect of the embodiments of the present invention, the present invention provides a data receiving method based on Orthogonal Frequency Division Multiplexing (OFDM) OFDM technology, the method comprising:

Determining the length of the cyclic prefix according to the length information of the fast Fourier transform FFT, and removing the cyclic prefix of the length from the received data, wherein the determining process of the length information of the FFT includes: according to the number of data transmission system antennas, the data bit width And the optical fiber transmission capacity of the data transmission system, determining the maximum sampling rate supported by the data transmission system, determining the maximum length of the FFT according to the determined maximum sampling rate, and selecting the value in the interval determined by the number of subcarriers and the maximum length as the length of the FFT Information

The FFT processing is performed on the received data from which the cyclic prefix is removed, based on the length information of the FFT. Further, determining the maximum length of the FFT includes:

Determining a maximum sampling rate supported by the data transmission system based on the fiber transmission capacity of the data transmission system and the quotient of the product; According to the quotient of the maximum sampling rate supported by the data transmission system and the system subcarrier spacing,

The maximum length of the FFT.

Further, the value is selected in the interval in which the number of subcarriers and the maximum length are determined, and the length information of the FFT includes:

In the interval in which the number of subcarriers and the maximum length are determined, a value suitable for performing the base 2, base 3, base 4, or mixed base FFT operation is selected;

The FFT computation complexity of each value is compared, and then the value with the smallest amount of calculation is selected as the length information of the FFT. According to another aspect of the embodiments of the present invention, the present invention provides a data transmitting apparatus based on Orthogonal Frequency Division Multiplexing (OFDM) technology, where the apparatus includes:

a mapping module, configured to map data to be sent to the IFFT processing module;

An IFFT processing module, configured to perform IFFT processing on the data to be sent according to the length information of the IFFT, wherein the determining process of the length information of the IFFT includes: according to the number of antennas of the data transmission system, the data bit width, and the optical fiber transmission capacity of the data transmission system, Determining a maximum sampling rate supported by the data transmission system, determining a maximum length of the IFFT according to the determined maximum sampling rate, and selecting a value in the interval determined by the number of subcarriers and the maximum length as the length information of the IFFT;

a cyclic prefix adding module, configured to determine a length of the cyclic prefix according to the length information of the IFFT, and add a cyclic prefix of the length in the IFFT processed data to obtain OFDM time domain baseband data;

And a sending module, configured to send OFDM time domain baseband data obtained by adding a cyclic prefix. Further, the device further includes:

a determining module, configured to determine a product of a number of data transmission system antennas and a data bit width; determining a maximum sampling rate supported by the data transmission system according to a fiber transmission capacity of the data transmission system and a quotient of the product, according to the data transmission system supporting The quotient of the maximum sampling rate and the system subcarrier spacing determines the maximum length of the IFFT. Further, the device further includes:

a selection module, configured to select a value suitable for the base 2, base 3, base 4, or mixed base IFFT operation in the interval in which the number of subcarriers and the maximum length are determined; compare the IFFT calculation complexity of each value, and then The value with the smallest amount of calculation is selected as the length information of the IFFT. According to another aspect of the embodiments of the present invention, the present invention provides a data receiving apparatus based on Orthogonal Frequency Division Multiplexing (OFDM) technology, the apparatus comprising:

a cyclic prefix removal module, configured to determine a length of a cyclic prefix according to length information of a fast Fourier transform FFT, and remove a cyclic prefix of the length from the received data, where the determining process of the length information of the FFT includes: The number of system antennas, the data bit width, and the fiber transmission capacity of the data transmission system, determine the maximum sampling rate supported by the data transmission system, determine the maximum length of the FFT according to the determined maximum sampling rate, and determine the number of subcarriers and the maximum length. Select the value as the length information of the FFT;

The FFT processing module is configured to perform FFT processing on the received data of the cyclic prefix removal according to the length information of the FFT.

Further, the device further includes:

a determining module, configured to determine a product of a number of data transmission system antennas and a data bit width; determining a maximum sampling rate supported by the data transmission system according to a fiber transmission capacity of the data transmission system and a quotient of the product, according to the data transmission system supporting The quotient of the maximum sample rate and the system subcarrier spacing determines the maximum length of the FFT.

Further, the device further includes:

a selection module, configured to select a value suitable for performing a base 2, base 3, base 4, or mixed base FFT operation in the interval in which the number of subcarriers and the maximum length are determined; compare FFT computational complexity of each value, and then The value with the smallest amount of calculation is selected as the length information of the FFT.

In the embodiment of the present invention, the selected data of the IFFT/FFT is used to perform IFFT and FFT on the transmitted data, thereby effectively reducing the sampling rate, and ensuring that the data rate transmitted on the optical fiber does not exceed the optical speed. The transmission capacity of the fiber achieves the goal of cost saving. DRAWINGS

FIG. 1 is a schematic diagram of a data transmission process based on OFDM technology according to an embodiment of the present invention; FIG. 2 is a schematic structural diagram of a data transmission apparatus based on OFDM technology according to an embodiment of the present invention;

3 is a data receiving process based on OFDM technology according to an embodiment of the present invention; FIG. 4 is a schematic structural diagram of a data receiving device based on OFDM technology according to an embodiment of the present invention. detailed description

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments in order to make the present invention. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

FIG. 1 is a data transmission process based on an OFDM downsampling rate technology according to an embodiment of the present invention, where the process includes the following steps:

S101: Map the received frequency domain to be transmitted data to the input end of the inverse fast Fourier transform IFFT.

Specifically, in the embodiment of the present invention, when the frequency domain to be transmitted data is mapped to the input end of the IFFT, it is determined that the number of the IFFT input end is 0 in the frequency domain according to the current number of subcarriers and the length information of the IFFT. When the current number of subcarriers is M, and the length information of the IFFT is N, the NM zeros need to be supplemented in the frequency domain.

S102: Perform IFFT processing according to the length information of the IFFT, where the determining process of the length information of the IFFT includes: determining, according to the number of antennas of the data transmission system, the data bit width, and the optical fiber transmission capacity of the data transmission system, the data transmission system supports Maximum sampling rate, according to the determined maximum sampling rate, determining the maximum length of the IFFT, determining the number of subcarriers and the maximum length The value is selected in the interval as the length information of the IFFT.

Determine the maximum length of the IFFT, including:

Determining a maximum sampling rate supported by the data transmission system based on the fiber transmission capacity of the data transmission system and the quotient of the product;

The maximum length of the IFFT is determined based on the quotient of the maximum sampling rate supported by the data transmission system and the system subcarrier spacing.

The value is selected in the interval determined by the number of subcarriers and the maximum length, and the length information of the IFFT includes:

In the section where the number of subcarriers and the maximum length are determined, the value that minimizes the IFFT calculation complexity is selected as the length information of the IFFT.

Specifically, when selecting the value that makes the IFFT calculation complexity the lowest as the length information of the IFFT, the method includes: selecting an IFFT suitable for performing the base 2, the base 3, the base 4, or the mixed base in the section where the number of subcarriers and the maximum length are determined. The numerical value of the operation; the IFFT calculation complexity of each value is compared, and then the value with the smallest calculation amount is selected as the length information of the IFFT.

S103: Determine a length of the cyclic prefix according to the length information of the IFFT, add a cyclic prefix of the length to the data after the IFFT processing, and obtain OFDM time domain baseband data and send the data.

In the embodiment of the present invention, in order to reduce the system sampling rate, the data rate transmitted on the base station fiber of the distributed structure does not exceed the transmission capacity of the optical fiber, that is, when data transmission is performed, there is no need to increase the number of optical fibers due to an excessive system sampling rate. In the embodiment of the present invention, when determining the length information of the IFFT, it is not limited to selecting the length information suitable for the base 2 or base 4 IFFT operation, and may also select an IFFT operation suitable for the base 3 or the hybrid base. Length information.

When determining the length information of the IFFT/FFT, it is necessary to ensure that the sampling rate of the system can meet the requirements, and the length information of the IFFT/FFT can minimize the computational complexity. In determining the length information of the IFFT/FFT in the embodiment of the present invention, the transmission capacity of the optical fiber can be comprehensively considered. Factors such as data bit width and number of subcarriers.

The data transmission and reception method provided in the embodiment of the present invention may be performed based on a base station, and the data transmission system may be a base station. Indoor baseband processing unit in base station of distributed structure

(Building Base Band Unit, BBU) and Radio Remote Unit (RRU) are connected by optical fiber. The transmission capacity of each fiber of the connection is v, that is, the transmission capacity of each fiber of the data transmission system is V. The data bit width is W, and the number of antennas of the base station is Tx, that is, the number of antennas of the data transmission system is Tx, and the maximum sampling rate supported by the data transmission system is = ^/(2 * ). After determining the maximum sampling rate supported by the data transmission system, based on the maximum sampling rate and the number of subcarriers, the maximum length of the IFFT/FFT can be determined as N Lf (/ L*) represents downward whole). After determining the maximum length of the IFFT/FFT, since the current number of subcarriers M is determined, and it is considered that the ^ is greater than or equal to the number M of subcarriers, the number of antennas or the number of optical fibers of the data transmission system needs to be renewed. Configuration. Therefore, the interval [ _M , determined by the number of subcarriers M and ax is determined. According to the interval composed of the number of subcarriers M and W, one of the intervals is selected to make the IFFT/FFT calculation complexity minimum value, and the value is used as the length information of the IFFT/FFT.

When the value is selected and the value is used as the length information of the IFFT/FFT, it is necessary to select the value N which makes the IFFT/FFT calculation complexity the lowest, as the length information of the IFFT/FFT, and therefore in the determined interval in the embodiment of the present invention. When selecting the minimum value of the IFFT/FFT calculation complexity as the length information of the IFFT/FFT, first select the values suitable for the IFFT/FFT operation of the base 2, base 3, base 4 or mixed basis, and compare the IFFT/ of these values. The FFT calculates the complexity, and then selects the one with the smallest amount of calculation as the length information of the IFFT/FFT.

In the embodiment of the present invention, the LTE system has a bandwidth of 20 MHz, the number of subcarriers is 1200, the subcarrier spacing is 15 KMz, the number of antennas of the data transmission system is 8, and the data bit width is 16 bits. The transmission capacity of the root fiber is 7Gbps, which can determine the maximum supported by the data transmission system.

The IFFT/FFT length is 1867, so the number of subcarriers M and ^ is [1200, 1867]. A value is selected in the interval, and the value is used as the length information of the IFFT/FFT. For example, the selected value is 1536, and the 1536 is 3 times 2 ⁹ , and the length information of the IFFT/FFT is 1536.

When the length information of the IFFT/FFT is 1536, the determined sampling rate is 23.04 MHz, and the sampling rate is significantly lower than the sampling rate 30.72 MHz determined in the prior art, which is the sampling rate in the prior art. 3/4

Based on the foregoing method for data transmission, an embodiment of the present invention provides a data transmitting apparatus based on an OFDM downsampling rate technique. As shown in FIG. 2, the transmitting apparatus includes:

The mapping module 21 is configured to map the received frequency domain to be transmitted data to an input end of the fast Fourier inverter to the IFFT;

The IFFT processing module 22 is configured to perform IFFT processing according to the length information of the IFFT. The determining process of the length information of the IFFT includes: determining, according to the number of antennas of the data transmission system, the data bit width, and the optical fiber transmission capacity of the data transmission system. The maximum sampling rate supported by the data transmission system determines the maximum length of the IFFT according to the determined maximum sampling rate, and selects the value in the interval determined by the number of subcarriers and the maximum length as the length information of the IFFT;

The cyclic prefix adding module 23 is configured to determine a length of the cyclic prefix according to the length information of the IFFT, and add a cyclic prefix of the length in the IFFT processed data to obtain OFDM time domain baseband data;

The sending module 24 is configured to send the OFDM time domain baseband data obtained after adding the cyclic prefix. The transmitting device further includes:

a determining module 25, configured to determine a product of a number of data transmission system antennas and a data bit width; determining a maximum sampling rate supported by the data transmission system according to a fiber transmission capacity of the data transmission system and a quotient of the product; according to the data transmission system support Maximum sampling rate and system subcarrier The quotient of the interval, determines the maximum length of the IFFT.

a selection module 26, configured to select a value suitable for performing an IFFT operation such as a base 2, a base 3, a base 4, or a mixed base in the interval in which the number of subcarriers and the maximum length are determined; and compare the IFFT calculation complexity of each value, Then, the value with the smallest amount of calculation is selected as the length of the IFFT. The transmitting device can be located in the base station of the distributed structure, and the base station further includes a bit-level processing module, a digital-to-analog converter (DAC) module, and a radio frequency ( Radio Frequency,

RF) module and antenna. The bit-level processing module is configured to process the data to be transmitted through bit level processing such as channel coding, and send the processed data to the mapping module. The mapping module performs symbol mapping on the processed data to form a phase shift keying (PSK) symbol or a Quadrature Amplitude Modulation (QAM) symbol, and then performs serial-parallel conversion to form parallel modulation symbols, and then After the mapping module fills in the frequency domain, the frequency domain data is mapped to the input end of the IFFT, and the IFFT processing is performed by the IFFT processing module, and then the parallel frequency domain data is converted into the serial time domain data through the parallel and serial conversion module. The cyclic prefix is added by Cyclic Prefix (CP), and a cyclic prefix is added to the data to form OFDM baseband discrete data. After the OFDM baseband discrete data is formed, the discrete data is converted into baseband analog data by a digital-to-analog converter (DAC) module, and then converted, filtered, power amplifier, etc. by a radio frequency (RF) module. Processing, the processed data is transmitted through the antenna.

FIG. 3 is a data receiving process based on an OFDM downsampling rate technology according to an embodiment of the present invention, where the process includes the following steps:

S301: Determine a length of the cyclic prefix according to the length information of the FFT, and remove a cyclic prefix of the length from the received data, where the determining process of the length information of the FFT includes: according to the number of antennas of the data transmission system, the data bit width, and the data transmission The fiber transmission capacity of the system determines the maximum sampling rate supported by the data transmission system, determines the maximum length of the FFT according to the determined maximum sampling rate, and selects the value in the interval determined by the number of subcarriers and the maximum length as the FFT Length information.

Wherein, determining the maximum length of the FFT includes:

The maximum length of the FFT is determined based on the quotient of the maximum sampling rate supported by the data transmission system and the system subcarrier spacing.

The value is selected in the interval determined by the number of subcarriers and the maximum length, and the length information for performing the FFT includes:

Among the sections in which the number of subcarriers and the maximum length are determined, a value that minimizes the complexity of the FFT calculation is selected.

When the specific selection makes the FFT calculation complexity minimum value as the length information of the FFT, in the interval where the number of subcarriers and the maximum length are determined, a value suitable for performing FFT operations such as base 2, base 3, base 4, or mixed basis is selected. ; Compare the FFT computation complexity of each value, and then select the value with the smallest amount of calculation as the length information of the FFT.

S302: Perform FFT processing on the received data with the cyclic prefix removed according to the length information of the FFT.

The process of determining the length information of the FFT is the same as the above process, that is, determining the maximum sampling rate supported by the data transmission system according to the number of antennas of the data transmission system, the data bit width, and the optical fiber transmission capacity of the data transmission system, according to the determined maximum sampling. Rate, determine the maximum length of the FFT, and select the value in the interval determined by the number of subcarriers and the maximum length as the length information of the FFT. Specifically, the maximum sampling rate is determined according to 匪^{= v/} ( ² * ^x * ), and the maximum length of the FFT is determined by the N-leg = Lf dish / /" (L* represents the downward rounding) according to the maximum sampling rate. And select one in the interval [M, consisting of the number of subcarriers M and the dish D to make the FFT calculate the lowest value of complexity, and use this value as the length information of the FFT. When the specific choice is to make the FFT calculation complexity the lowest value as the length information of the FFT, first select the values suitable for the FFT operation of the base 2, base 3, base 4 or mixed basis, compare the FFT computational complexity of these values, and then from The value with the smallest amount of calculation is selected as the length information of the FFT.

Based on the foregoing data receiving method, an embodiment of the present invention provides a data receiving apparatus based on an OFDM downsampling rate technique. As shown in FIG. 4, the receiving apparatus includes:

The cyclic prefix removal module 41 is configured to determine a length of the cyclic prefix according to the length information of the fast Fourier transform FFT, and remove a cyclic prefix of the length from the received data, where the determining process of the length information of the FFT includes: The number of transmission system antennas, the data bit width, and the fiber transmission capacity of the data transmission system, determine the maximum sampling rate supported by the data transmission system, and determine the maximum length of the FFT according to the determined maximum sampling rate, determined by the number of subcarriers and the maximum length. Select a value in the interval as the length information of the FFT;

The FFT processing module 42 is configured to perform FFT processing on the received data of the cyclic prefix to obtain the original data according to the length information of the FFT.

The receiving device further includes:

a determining module 43, configured to determine a product of a number of data transmission system antennas and a data bit width; determining a maximum sampling rate supported by the data transmission system according to a fiber transmission capacity of the data transmission system and a quotient of the product; according to the data transmission system support The maximum sampling rate and the quotient of the system subcarrier spacing determine the maximum length of the FFT.

The receiving device further includes:

The selecting module 44 is configured to select, in the interval determined by the number of subcarriers and the maximum length, a value suitable for performing FFT operations such as base 2, base 3, base 4, or mixed basis; compare FFT computation complexity of each value, Then, the value with the smallest amount of calculation is selected as the length information of the FFT.

The receiving device can be located in a base station of a distributed structure. The base station further includes a radio frequency module, and performs filtering, amplifying, and down-converting the received uplink data sent by the user to form an analog baseband number. According to. The analog baseband signal is converted into digital baseband data by an analog-to-digital conversion (ADC) module. Thereafter, the cyclic prefix removal module removes the cyclic prefix in the data, and converts the serial data into parallel data through a serial-to-parallel conversion module. Then, the data is input to the input end of the FFT processing module, and the FFT processing is performed to form frequency domain data, thereby acquiring user data corresponding to the frequency domain position. Then, after the conversion of the parallel-to-serial conversion module, the parallel data is converted into serial data, and then the demapping process is performed according to the mapping manner agreed with the transmitting device, and the demapped data is subjected to bit-level processing such as channel decoding to obtain a user. The original send data.

Specifically, in the embodiment of the present invention, the base station includes a BBU and an RRU, wherein the BBU and the RRU are connected by an optical fiber, and the interface is an Ir interface. The BBU and the RRU distributed base station are connected by using an optical fiber, which is larger than that of the ordinary base station. Reduce the cost of the feeder and the difficulty of engineering construction.

The following is a detailed description of the process of data transmission and reception in the embodiment of the present invention, in which the length information of the base station IFFT/FFT is 1536 and the number of subcarriers is 1200.

When the base station performs downlink data transmission, the BBU of the base station maps the data to be transmitted in the frequency domain to the IFFT input end, and the data to be transmitted in the first half of the frequency domain is mapped to the last 600 points of the IFFT input end, and the data to be transmitted in the second half of the frequency domain is mapped to the IFFT. The first 600 points of the input, the middle of the IFFT input is 1536-1200 = 336 points are set to 0.

The BBU performs an IFFT transform of 1536 points, and adds a CP to the transformed data to form OFDM time domain baseband data according to the determined CP length, wherein the length of the CP is 3 of the CP length used when performing the IFFT transform of 2048 points. /4. After the OFDM time domain baseband discrete data is formed, the BBU sends the data to the RRU through the Ir interface, and the RRU converts the received base station discrete data into high frequency analog data, and transmits the data to the wireless channel through the antenna.

That is, the bit-level processing module, the symbol mapping module, the serial-parallel conversion, the mapping module, the IFFT processing module, the parallel-serial conversion module, and the cyclic prefix adding module are all located in the BBU, and the DAC module and the radio module are located in the RRU.

After the base station RRU receives the uplink data sent by the user, the RRU pairs the received data. Perform filtering, amplification, down conversion, and ADC processing to obtain OFDM time-domain baseband discrete data with a sampling rate of 23.04 MHz. The RRU then sends the data to the BBU through the Ir interface. After receiving the data, the BBU removes the CP in each OFDM symbol of the data according to the determined CP length. The length of the CP is 3/4 of the length of the CP used when performing the FFT transform of 2048 points. After that, the BBU performs an FFT transformation of 1536 points, and the user data can be acquired in the corresponding frequency domain position, and subsequent processing is performed.

That is, in the base station, the radio frequency module and the analog-to-digital conversion module are located in the RRU, and the cyclic prefix removal module, the serial-to-parallel conversion module, the FFT processing module, and the parallel-to-serial conversion module are located in the BBU.

Embodiments of the present invention provide a data transmission and reception method and apparatus based on OFDM technology, and determine data transmission according to the number of antennas of the data transmission system, the data bit width, and the optical fiber transmission capacity of the data transmission system during data transmission and reception. The maximum sampling rate supported by the system determines the maximum length of the IFFT/FFT according to the determined maximum sampling rate, and selects the value in the interval determined by the number of subcarriers and the maximum length as the length information of the IFFT/FFT, according to the length information. IFFT and FFT can effectively reduce the sampling rate of the system and ensure that the data rate transmitted on the fiber does not exceed the transmission capacity of the fiber, thereby saving equipment costs.

The above description shows and describes a preferred embodiment of the present invention, but as described above, it should be understood that the present invention is not limited to the form disclosed herein, and should not be construed as being Other combinations, modifications, and environments are possible and can be modified by the teachings of the above teachings or related art within the scope of the inventive concept described herein. All changes and modifications made by those skilled in the art are intended to be within the scope of the appended claims. Industrial applicability

The invention can effectively reduce the sampling rate of the system, ensure that the data rate transmitted on the optical fiber does not exceed the transmission capacity of the optical fiber, and achieve the purpose of saving equipment cost.

Claims

Claim

A data transmission method based on orthogonal frequency division multiplexing (OFDM) technology, the method comprising: mapping frequency domain to-be-transmitted data to an input end of an inverse fast Fourier transform IFFT;

The length of the cyclic prefix is determined according to the saved length information of the IFFT, and the cyclic prefix of the length is added to the IFFT processed data to obtain OFDM time domain baseband data and transmitted.

2. The method according to claim 1, wherein the determining the maximum length of the IFFT comprises: determining a product of a number of data transmission system antennas and a data bit width;

The method according to claim 1 or 2, wherein the selecting a value in the interval determined by the number of subcarriers and the maximum length, as the length information of the IFFT, specifically includes:

The IFFT computational complexity of each value is compared, and then the least calculated value is selected as the length information of the IFFT.

4. A data receiving method based on orthogonal frequency division multiplexing (OFDM) technology, comprising: determining a length of a cyclic prefix according to a length information of a fast Fourier transform FFT, and removing a cyclic prefix of the length from the received data, where The process of determining the length information of the FFT includes: Determining the maximum sampling rate supported by the data transmission system according to the number of antennas of the data transmission system, the data bit width, and the optical fiber transmission capacity of the data transmission system, determining the maximum length of the FFT according to the determined maximum sampling rate, determining the number of subcarriers and the maximum length Select the value in the interval as the length information of the FFT;

The FFT processing is performed on the received data from which the cyclic prefix is removed, based on the length information of the FFT.

5. The method of claim 4, wherein determining the maximum length of the FFT comprises: determining a product of a number of data transmission system antennas and a data bit width;

The maximum length of the FFT.

The method according to claim 4 or 5, wherein the selecting a value in the interval in which the number of subcarriers and the maximum length are determined, as the length information of the FFT, includes:

The FFT computation complexity of each value is compared, and then the value with the smallest amount of calculation is selected as the length information of the FFT.

A data transmitting apparatus based on Orthogonal Frequency Division Multiplexing (OFDM) technology, the apparatus comprising: a mapping module, configured to map data to be transmitted to an IFFT processing module;

a cyclic prefix adding module, configured to determine the length of the cyclic prefix according to the length information of the IFFT, And adding a cyclic prefix of the length in the IFFT processed data to obtain OFDM time domain baseband data;

And a sending module, configured to send OFDM time domain baseband data obtained by adding a cyclic prefix.

The transmitting device according to claim 7, wherein the device further comprises:

a determining module, configured to determine a product of a number of data transmission system antennas and a data bit width; determining a maximum sampling rate supported by the data transmission system according to a fiber transmission capacity of the data transmission system and a quotient of the product, according to the data transmission system supporting The quotient of the maximum sampling rate and the system subcarrier spacing determines the maximum length of the IFFT.

The transmitting device according to claim 7 or 8, wherein the device further comprises: a selecting module, configured to select, in the interval determined by the number of subcarriers and the maximum length, base 2, base 3, The value of the base 4 or mixed base IFFT operation; compare the IFFT computational complexity of each value, and then select the value with the smallest amount of calculation as the length information of the IFFT.

10. A data receiving apparatus based on Orthogonal Frequency Division Multiplexing (OFDM) technology, the apparatus comprising:

The receiving device according to claim 10, wherein the device further comprises: a determining module, configured to determine a product of a number of data transmission system antennas and a data bit width; according to the optical fiber transmission capacity of the data transmission system and the product Business, determine the data transmission system The maximum sampling rate, based on the maximum sampling rate supported by the data transmission system and the quotient of the system subcarrier spacing, determines the maximum length of the FFT.

The receiving device according to claim 10 or 11, wherein the device further comprises: a selecting module, configured to select, in the interval determined by the number of subcarriers and the maximum length, base 2, base 3, The value of the base 4 or mixed-base FFT operation; compares the FFT computational complexity of each value, and then selects the smallest calculated value as the length information of the FFT.

A base station, the base station comprising the transmitting device according to any one of claims 1 to 9, and the receiving device according to any one of claims 10 to 12.