WO2012130090A1

WO2012130090A1 - Ofdm-based method and system for transmitting data

Info

Publication number: WO2012130090A1
Application number: PCT/CN2012/072874
Authority: WO
Inventors: 鲍东山; 曾勇波; 雷俊; 王竞; 姚惠娟; 闫志刚
Original assignee: 北京新岸线无线技术有限公司
Priority date: 2011-03-25
Filing date: 2012-03-23
Publication date: 2012-10-04
Also published as: CN103444146B; CN102790742A; CN102594763A; CN103444146A

Abstract

Disclosed is an OFDM-based method for transmitting data, for use in a short-to-mid range wireless communication system uplink data transmission. An available frequency band of the system is equally divided into N number of basic frequency sub-bands. The method comprises: an transmitting station using a single frequency sub-band or a combination of M number of frequency sub-bands to transmit data to a receiving station, where M = 2n; the transmitting station using fs or M*fs as the baseband sample sampling rate; the receiving station receiving within the available frequency band the data transmitted by the one or multiple transmitting stations; and the receiving station using N*fs as the baseband sample sampling rate. Also provided in the present invention is an OFDM-based system for transmitting data. In the present invention, the OFDM-based technology and employment of the combination of frequency sub-bands allow for the transmitting station and the receiving station in a wireless communication system to have different bandwidth configurations, thus allowing for employment of a lower configuration by the transmitting station to reduce hardware costs, and for employment of a higher configuration by the receiving station to improve efficiencies such as frequency spectrum utilization rate and throughput, also allowing for multiple user stations to communicate simultaneously with an access point.

Description

Data transmission method and system based on OFDM

The application date of this application is March 25, 2011, and the application number is 201110074380.X. The invention name is the priority of a prior application of an OFDM-based data transmission method and system, and all the contents of the prior application have been It is embodied in this application.

Technical field

The present invention relates to the field of wireless communication technologies, and in particular, to an OFDM-based data transmission method and system.

Background technique

In the wireless office i or network WLAN technology based on the 802.11 series of standards, multi-user transmission is implemented by Carrier Sense Multiple Access (CSMA), that is, multiple station STAs cannot access at the same time. A point AP can only be accessed in a time-sharing manner, even if the AP has a free spectrum resource STA. For example, in an 802. l ln system, an AP can occupy 40 MHz of bandwidth resources and can be divided into two 20 MHz subbands. The STA can only communicate with the AP using the entire 40 MHz bandwidth or one of the 20 MHz subbands, but the two support 20 MHz bandwidth. The STA cannot occupy one of the 20MHz subbands and communicate with the AP at the same time. It can only communicate with the AP in the 40MHz bandwidth on the main channel in different time periods, and the 20MHz slave channel is idle, which causes the waste of the frequency resources. .

Orthogonal Frequency Division Multiple Access (OFDM) is a multiple access method used in mobile communication systems. Multiple mobile terminals (MSs) occupy different subcarrier groups in the available bandwidth. The base station (BS) communicates at the same time to improve spectrum utilization.

In an existing WLAN, the STA must communicate with the AP in the same bandwidth configuration. For example, in an 802.lin system, the STA and the AP communicate with either a 40 MHz bandwidth or a 20 MHz bandwidth. If the AP supports 40 MHz bandwidth in a WLAN network and there are two 20 MHz STAs, the AP can only use the 20 MHz bandwidth configuration to communicate with the STAs that have reached the primary channel resources, thus causing a waste of 20 MHz resources. In the future WLAN technology, the bandwidth available to the AP may reach 80 MHz or more. If the above bandwidth configuration scheme is continued, more spectrum resources will be wasted.

In the 0FDMA mechanism, although multiple terminals can occupy different subcarriers and simultaneously communicate with the base station, the receiving end and the transmitting end need to support the same bandwidth configuration, that is, the inverse fast Fourier transform (IFFT) module of the transmitting end. The number of FFT points of the FFT and Fast Fourier Transform must be the same. In addition, the multiple access mode of uplink orthogonal frequency division multiple access (OFDM) access to 0FDMA has higher requirements for synchronization. Multiple times in the time domain The signal transmitted by the terminal (MS) needs to arrive at the base station (BS) at the same time without causing inter-symbol interference and inter-user interference; in the frequency domain, due to the different carrier crystal frequency accuracy of multiple MS transmitters, and the BS carrier crystal frequency The deviation is also different, so the frequency offset of the signals arriving at each MS of the BS is also different, and the OFDM modulation itself is sensitive to the frequency offset, and the frequency offset from each MS signal must be corrected to correctly demodulate, otherwise it will cause multiple users. Disturb. Therefore, in the 0FDMA system, time synchronization and frequency synchronization are key issues that require complex synchronization algorithms. In a wireless local area network system, if the multiple access method using OFDM is used to improve the efficiency of the frequency, the equipment cost will increase.

Summary of the invention

The present invention provides a data transmission method and system based on Orthogonal Frequency Division Multiplexing (OFDM), which can realize multiple communication stations simultaneously communicating with a receiving station, and has low complexity, which can improve spectrum utilization and system throughput. The invention provides an OFDM-based data transmission method, which is used for uplink data transmission in a medium- and short-range wireless communication system, and divides the available frequency band of the system into N basic sub-bands in advance, and the method includes:

The transmitting station transmits data to the receiving station using a single sub-band or a combination of M sub-bands, where M = 2 ⁿ , n = 0, 1, 2, . . . , JL M < N, N, M are positive integers; The baseband sample sampling rate fs or M*fs; the receiving station receives data transmitted from one or more transmitting stations in the available frequency band; and the receiving station uses the baseband sample sampling rate as N*fs. The present invention provides a data transmission system based on Orthogonal Frequency Division Multiplexing (OFDM) for short-range wireless communication. The available frequency band of the system is divided into N basic sub-bands, and the system includes: at least two transmitting stations, Data is transmitted to the receiving station using a single sub-band and/or M sub-band combination, respectively, where M = 2 ⁿ , n = 0, 1, 2, . . . , and M < N, N, M are positive integers; The base station sample sampling rate fs or M*fs is used at the launch site;

The receiving station receives data transmitted from the transmitting stations within the available frequency band; the sampling rate of the baseband samples used is N*fs.

Preferably, the transmitting station includes: a subcarrier generating unit, configured to set a virtual subcarrier at both ends of the subbands to set a guard band at an edge of the subband.

In summary, the technical solution provided by the present invention, based on the combination of the OFDM technology and the sub-band, allows the transmitting station STA and the receiving station AP in the wireless communication system to have different bandwidth configurations, and the transmitting station STA can use a lower configuration to reduce the configuration. The hardware implementation cost, the receiving site AP can use a higher configuration to improve efficiency: spectrum utilization, throughput, etc., and can achieve multiple STAs to communicate with the AP at the same time. In addition, a guard band, that is, a virtual carrier, is added at the edge of the subband, and subbands can be avoided. For the interference, each sub-band can be separately shaped and filtered, and the receiving end only needs to perform matched filtering on the entire frequency band, and does not need multiple baseband receivers to match the filtering for different sub-bands; the cyclic prefix (CP) is extended, and the time is reduced. Synchronization requirements. The sampling rate of the baseband sample at the receiving end is N times the sampling rate of the basic subband sample, ensuring that the IFFT/FFT module of the N1 point is required only in the basic subband, and the IFFT/FFT module of the N2=N*N1 point is used at the receiving end, and Multiple parallel N1 point IFFT/FFT modules are not required to demodulate information for each sub-band. This can improve spectrum utilization and system throughput, and enable multiple STAs to communicate with the AP at the same time without increasing the cost of the system and user site equipment.

DRAWINGS

1 is a schematic diagram of a wireless communication system architecture in the prior art;

2 is a block diagram of a multi-band OFDM transmitting end and a receiving end baseband part module according to an embodiment of the present invention; FIG. 3 (a), (b), (c) and (d) are respectively several sub-bands in the embodiment of the present invention; Schematic diagram

Figures 4(a) and 4(b) are schematic diagrams of the other two subbands in Figure 3(b).

detailed description

In view of the deficiencies in the prior art, the present invention proposes a multi-user data transmission scheme for medium and short-range wireless communication, using a multi-user access method similar to orthogonal frequency division multiple access (OFDM), based on OFDM and corresponding The synchronization mechanism divides the available frequency band of the system into N basic sub-bands, and the bandwidth of the transceiver (STA) transceiver may be a frequency band of a basic sub-band or a sub-band combination, and the receiving station (AP) transceiver bandwidth may be according to a specific situation. For N basic subbands, assuming a basic subband of 20 MHz, the receiving station (AP) transceiver bandwidth can be 20 MHz, 40 MHz, 80 MHz, ie 80 MHz bandwidth can be sent and received for STA receivers that only support 20 MHz bandwidth. The signal of the AP, such that the present invention based on the OFDM modulation technique enables multiple STAs to communicate with the AP using different sub-band resources, and reduces the time-frequency synchronization requirements and synchronization accuracy required for the OFDM system. The invention provides an OFDM-based data transmission method, which is used for uplink data transmission in a medium- and short-range wireless communication system, and divides an available frequency band of the system into N basic sub-bands, the method comprising: transmitting a single sub-band or The M subband combinations transmit data to the receiving station, where M=2 ⁿ , n=0, 1, 2, . . . , JL M < N, N, M are positive integers; the transmitting station uses the baseband sample sampling rate fs Or M*fs;

If the baseband portion is processed by an inverse fast Fourier transform IFFT/Fast Fourier Transform FFT, where the baseband sample sample rate is a sample of the input port of the inverse fast Fourier transform IFFT/Fast Fourier Transform FFT module. Sample rate The receiving station receives data transmitted from one or more transmitting stations within the entire frequency band; the receiving station uses a baseband sample sampling rate of N*fs. In the data transmission method provided by the present invention, the baseband portion is processed by an inverse fast Fourier transform IFFT/fast Fourier transform FFT, and the receiving station uses a different FFT length from the transmitting station: if the basic subband uses K point IFFT/FFT module, if the transmitting station occupies M basic sub-bands, the length of the IFFT/FFT module of the transmitting station is M*K point, and the length of the IFFT/FFT module of the receiving station is point. If the transmitting station and the receiving station support the same bandwidth, the number of IFFT/FFT subcarriers and the sampling rate of the transmitting station and the receiving station are the same; if there are multiple transmitting stations in the system, the bandwidth supported by each transmitting station is different, Under the premise of bandwidth configuration requirements, multiple transmitting sites can send data to the receiving site with their respective bandwidth configurations within the bandwidth supported by the receiving site. The data transmission method further includes: setting a guard band at an edge of the subband, specifically: setting a virtual subcarrier at both ends of the subband. In the data transmission method provided by the embodiment of the present invention, when a plurality of transmitting stations transmit data, a carrier frequency offset is respectively set for each transmitting station to determine a carrier center frequency of each transmitting station. In the data transmission method provided by the embodiment of the present invention, when a plurality of transmitting stations transmit data, setting a cyclic prefix CP length T _{eP of} the wireless communication system satisfies the following conditions:

Where 2δ is the two-way propagation delay experienced by the signal from the transmitting station to the maximum allowable coverage radius, ^ multipath delay spread.

In the embodiment of the present invention, the subband broadband is 20 MHz; and / or M = 1, 2, 4; and / or K = 256; and / or the baseband sample sampling rate fs = 20 MHz. In order to make the principles, features, and advantages of the present invention more comprehensible, the present invention will be described in detail with reference to the specific embodiments.

1 is a schematic block diagram of a transmitting end and a receiving end. The embodiment of the present invention relates to only a part of a baseband module in a transmitting end and a receiving end. Therefore, the source, the radio frequency, the sink, and the baseband part shown in FIG. 1 are not involved in the present invention. The module is not mentioned here.

First, the entire frequency band of the system is equally divided into N basic sub-bands for use by STA sites in the system.

In this embodiment, the entire bandwidth of the system is W=80 MHz, which is equally divided into N=4 basic sub-bands, each basic sub-band bandwidth B=20 MHz, assuming that each basic sub-band can only be used by one transmitting station STA. Separately occupied, and one STA can transmit data to the AP using one or more basic sub-bands. STA supports 20MHz, 40MHz and 80MHz bandwidth, AP supports 20MHz, 40MHz and 80MHz Bandwidth, when the AP has 80MHz bandwidth receiving capability, it can simultaneously receive data transmitted in any subband combination. Figure 2 shows a block diagram of the baseband part of the four 20MHz bandwidth stations STA1 ~ STA4 when the different sub-bands are used to transmit data to an 80MHz bandwidth AP.

As shown in Figure 2, four STAs transmit data to the AP, which is represented by STA1 ~ STA4. Each STA occupies a basic sub-band, that is, 20MHz bandwidth, and XI ~ X4 represent data from the corresponding STA. Only modules that are closely related to IFFT/FFT when implementing multi-band OFDM transmission are shown in Figure 2. Others do not affect or affect modules in a complete transceiver, such as coding, constellation point mapping, stream parsing, channel estimation, ΜΠ10 Detection, decoding, etc. will not be described here. The sub-band division in the embodiment of the present invention is as shown in Fig. 3 (a).

Figure 3 is a schematic diagram of the equivalent baseband of the subband division. For convenience, the negative frequency used in the 802. l ln standard can be used as the phase difference; the frequency of the negative frequency is shifted to the positive frequency, but the two are essentially There is no difference. The AP uses a bandwidth of 80 MHz in the [-40 MHz, 40 MHz] band, and the center frequency f0=0. Only the case of the STA single antenna is illustrated in FIG. 3, and the same applies to the case where the STA and the AP are multi-antenna exclusive sub-bands and the plurality of STAs share the sub-band by space division multiplexing. Figure 3 (a) is a schematic diagram of the frequency bands occupied by the four STAs in Figure 2, where fO = 0, STAl uses the [-40MHz, - 20MHz] frequency band, the center frequency fl = -30MHz, STA2 uses [-20MHz , 0MHz] frequency band, center frequency f 2=- 10MHz, STA3 uses [0MHz, 20MHz] frequency band, center frequency f3=10MHz, STA4 uses [20MHz, 40MHz] frequency band, center frequency f4=30MHz. The signal model of the sub-band division shown in Fig. 3 (a) is described below. To transmit four 20MHz signals in parallel, each signal can be separated in the frequency domain to ensure orthogonality, that is, respectively modulated to non-overlapping frequency bands. The number of subcarriers Nfft (the number of points of the IFFT/FFT transform), the sample interval T _{s ,} and the correspondence between the sample frequencies f _s are as follows:

Tu represents the duration of the OFDM symbol. The baseband signal center frequency = 0, and when the subcarrier spacing is = 7SA25 kHz, the number of subcarriers used in this embodiment is Nfft (the number of IFFT/FFT transform points), the sample interval T _{s ,} and the sample frequency f _s The correspondence is shown in Table 1. Table 1

The sample frequency fs in Table 1 is the lowest sample rate, and the adjustable value is greater than the value shown in Table 1. In this embodiment, the center frequencies of the four signals are respectively 30 MHz, f ₂ = -10 MHz, and f ₃ = 10 MHz. f = 30MHz, which occupies a continuous 80MHz channel. The subcarrier offset value corresponding to each signal center frequency is divided into ¹ J: - 384A, -128A, 128A, 384A. Referring to FIG. 2 and FIG. 3( a ), in this embodiment, the data of each STA first passes the IFFT transform of Nfftl=256 points (the number of subcarriers), and the sampling interval of the baseband samples (the sampling interval of the input sample points of the IFFT module) ) is 50 ns, and then passes D/A (D/A part contains low-pass filtering), then the frequency shift is performed, and the center frequency is divided into another 'J is fl ~f4, where fl=f0-30, f2=f0-10 , f3=f0+10, f4=f0+30 _{: The} unit is MHz. It is processed by other baseband processing, RF channel and channel, and received by the AP. The data received by the AP is also processed by the RF channel and other modules of the baseband. AP The baseband sample point sampling interval is 12.5 ns. After FFT transformation of Nfft2=1024 points, the data of different STAs can be taken out from the corresponding frequency band for subsequent processing. Regardless of time deviation, frequency deviation, and spurious noise, it is assumed that the receiving baseband receives continuous signals of different carrier frequencies as follows:

η ^( = ^{ XX _k exp(y 2^: - 3 S4)AFt) + ^ Y _n Qxp(j2 (n- )AFt)

k=-m

+ ∑ X _k Qxp(j2 (k + m)AFt) + ^ Y _n Qxp(j2 (n + 3M)AFt)

=-m =-m

r{n)[__ _nT (k-3S4)AFnT _s )+ 3⁄4 X _n x _V (j2 (n- )AFnT _s )

+ ^ Y _k exp(j2 (k + m)AFnT _s )+ ^ Z _n exp(j2^(n + 3M)AFnT _s ) 1 ί

=— 1 exp( 7'2π A: 'AFnT _s )+ ^ X _n , _+m exp(j2 n' AFnT _s )

N

For 80MHz

For r (nM, 1024-point FFT transform can demodulate the signals W, X, Y, Ζ.

In order to ensure the signal period is consistent, the sampling rate of the input data of the FFT module is different for signals of different bandwidths. In the 20MHz bandwidth, the 256-point FFT should have a sampling period of 50ns; in the 80MHz bandwidth, the 1024-point FFT has a sampling period of 12.5ns. In the embodiment of the present invention, the sub-bands are combined for use by each station. For example, two sub-bands may be combined for one use, or all sub-bands may be combined into one frequency band for use. The sub-band combination in this embodiment is shown in Figure 3 (b), Figure 3 (c) and Figure 3 (d).

Figure 3(b) shows two STAs with 20MHz bandwidth sharing 80MHz with a 40MHz bandwidth STA. The sub-band division of the spectrum is shown, and the center frequencies of the three sub-bands are respectively fl=- 30 MHz, f 2=0, and f3=30 MHz. In addition, Figure 3 (b) has two variants, as shown in Figure 4. Figure 3 (c) shows the sub-band division of two 80MHz bandwidth STAs sharing 80MHz frequency. The center frequencies of the two sub-bands are fl=- 20MHz and f2=20.

Figure 3 (d) shows an 80MHz bandwidth STA occupying all 80MHz frequency subbands, and the subband center frequency is fl=0. Figure 3 (b) shows the case where two 20MHz bandwidth STAs share a 80MHz spectrum with a 40MHz bandwidth STA. The frequency band distribution can also be changed, as shown in Figure 4. When the AP is configured for 40MHz or 80MHz bandwidth, it is allowed to have a free basic subband or a basic subband combination in its frequency. If the transmitting station and the receiving station support the same bandwidth, the number of IFFT/FFT subcarriers and the sampling rate of the transmitting station STA and the receiving station are the same; if there are multiple transmitting stations in the system, the bandwidth supported by each transmitting station is different, Under the premise of meeting the bandwidth configuration requirements, multiple transmitting stations can send data to the receiving station with their respective bandwidth configurations within the bandwidth supported by the receiving station.

If the available bandwidth of the system bandwidth is 40MHz, the Bay' J AP supports 40MHz, the STA supports 20MHz or 40MHz, and the AP supports two STAs for simultaneous transmission. If the available bandwidth of the system is 20MHz, the frequency band can be further divided. Each STA uses a part of resources in the frequency band, but the center frequency of each STA is the same as that of the AP, and no additional frequency shift (central frequency offset) .

Each sub-band occupied by each STA has its own virtual sub-carrier, which is disposed at the edge (both ends) of the sub-band, and is used as a guard band. Each STA only has to do the shaping filtering on the bandwidth it supports, rather than the shaping filter on the entire W. However, the shaping filtering of the entire bandwidth W of the AP allows the AP to flexibly support STAs with different bandwidth configurations. In order to eliminate or minimize the occurrence of Inter-Symbol Interference (ISI) and multi-user, the system needs to design a reasonable synchronization mechanism, specifically, introduce a cyclic prefix (CP, Cycl ic Prefix). ), and the length of the cyclic prefix CP varies with the transmission mode, the frame structure, and the corresponding protocol, and it is necessary to design the length of the cyclic prefix CP in the system that satisfies the requirements. In the embodiment of the present invention, when receiving the downlink frame sent by the receiving station AP, the transmitting station STA may determine a time point t according to the synchronization preamble of the downlink frame. Each STA in their respective estimate calculated on the basis of the time point for uplink transmission time, the CP length of the system design to ensure coverage of the farthest AP STA to the bidirectional propagation delay 2 <5 and multipath delay spread T _m, consider time With the synchronization error, the multipath signals of all STAs can reach the STA within the CP range, and no inter-symbol interference (ISI) and multi-user interference are generated.

In the embodiment of the present invention, when there are multiple transmitting stations transmitting data, setting the cyclic prefix CP length T _{eP of} the wireless communication system needs to meet the following conditions:

> 2δ +τ An embodiment of the present invention further provides an OFDM-based data transmission system, which is used for medium-and short-range wireless communication. The available frequency band of the system is divided into N basic sub-bands, and the system includes: at least two transmitting stations, each using a single The subband and/or M subband combination transmits data to the receiving station, where M=2 ⁿ , n=0, 1, 2, . . . , and M < N, N, M are positive integers; Baseband sample sampling rate fs or M*fs;

The receiving station receives data transmitted from the transmitting stations in the entire frequency band of the system; the sampling rate of the baseband samples used is N*fs. Preferably, the transmitting station includes: a subcarrier generating unit, configured to set a virtual subcarrier at both ends of the subbands to set a guard band at an edge of the subband.

In the embodiment of the present invention, the sub-band broadband is 20 MHz; and/or M=l, 2, 4; and/or K=256; and/or the baseband sample sampling rate fs=20 MHz. If the transmitting station and the receiving station support the same bandwidth, the number of IFFT/FFT subcarriers and the sampling rate of the transmitting station STA and the receiving station are the same; if there are multiple transmitting stations in the system, the bandwidth supported by each transmitting station is different, Under the premise of meeting the bandwidth configuration requirements, multiple transmitting stations can send data to the receiving station with their respective bandwidth configurations within the bandwidth supported by the receiving station.

In summary, the technical solution provided by the present invention, based on the combination of the OFDM technology and the sub-band, allows the transmitting station STA and the receiving station AP in the wireless communication system to have different bandwidth configurations, and the transmitting station STA can use a lower configuration to reduce the configuration. The hardware implementation cost, the receiving site AP can use a higher configuration to improve efficiency: spectrum utilization, throughput, etc., and can achieve multiple STAs to communicate with the AP at the same time. In addition, a guard band, that is, a virtual carrier, is added at the edge of the sub-band, which avoids interference between sub-bands, and each sub-band can be separately shaped and filtered, and the receiving end only needs to perform matched filtering on the entire frequency band, without multiple baseband receiving. The machine performs matched filtering for different sub-bands, and extends the cyclic prefix (CP) to reduce the time synchronization requirement. The sampling rate of the baseband sample at the receiving end is N times the sampling rate of the basic subband sample, ensuring that the IFFT/FFT module of the N1 point is required only in the basic subband, and the IFFT/FFT module of the N2=N*N1 point is used at the receiving end, and Multiple parallel N1 point IFFT/FFT modules are not required to demodulate information for each sub-band. This can improve the spectrum utilization system throughput rate, and enable multiple STAs to communicate with the AP at the same time without increasing the cost of the system and user site equipment.

The present invention has been disclosed in the above preferred embodiments, but it is not intended to limit the invention, and the present invention may be modified and modified without departing from the spirit and scope of the invention. The scope of protection should be determined by the scope defined by the claims of the present invention.

Claims

Claim

1. An OFDM-based data transmission method for uplink data transmission in a medium- and short-range wireless communication system, characterized in that the available frequency band of the system is equally divided into N basic sub-bands, the method comprising:

The transmitting station transmits data to the receiving station using a single sub-band or a combination of M sub-bands, where M = 2 ⁿ , n = 0, 1, 2, . . . , JL M < N, N, M are positive integers;基 using the baseband sample sampling rate fs or M*fs;

The receiving station receives data transmitted from one or more transmitting stations within the available frequency band; the receiving station uses the baseband sample sampling rate as N*fs.

2. The data transmission method according to claim 1, wherein the baseband portion is processed by an inverse fast Fourier transform IFFT/Fast Fourier Transform FFT, and the receiving station uses a different FFT length from the transmitting station. : If the basic subband uses the K-point IFFT/FFT module, if the transmitting station occupies M basic subbands, the length of the IFFT/FFT module of the transmitting station is M*K, and the length of the IFFT/FFT module of the receiving station is N*K.

3. The data transmission method according to claim 2, wherein if the transmitting station and the receiving station support the same bandwidth, the number of IFFT/FFT subcarriers and the sampling rate of the transmitting station and the receiving station are the same; There are multiple transmitting sites, and each transmitting site supports different bandwidths. Under the premise of meeting the bandwidth configuration requirements, multiple transmitting sites can send data to the receiving site with their respective bandwidth configurations within the bandwidth supported by the receiving site.

4. The data transmission method according to claim 1, further comprising: setting a guard band at an edge of the subband, specifically:

Virtual subcarriers are disposed at both ends of each of the subbands.

5. The data transmission method according to claim 1, wherein when a plurality of transmitting stations transmit data, carrier frequency offsets are respectively set for each transmitting station to determine a carrier center frequency of each transmitting station.

6. The data transmission method according to claim 1, wherein when a plurality of transmitting stations transmit data, setting a cyclic prefix CP length T _{eP of} the wireless communication system satisfies the following conditions:

Where 2δ is the two-way propagation delay experienced by the signal from the transmitting station to the maximum allowable coverage radius, τ„ is the multipath delay spread.

7. The data transmission method according to claim 1, wherein said sub-band broadband is 20 MHz; and/or M = 1, 2, 4; and/or K = 256; and/or baseband samples are as follows. The rate fs = 20 MHz.

8. An OFDM-based data transmission system for medium-and short-range wireless communication, characterized in that the available frequency band of the system is equally divided into N basic sub-bands, the system comprising: at least two transmitting stations, each using a single The subband and/or M subband combination transmits data to the receiving station, where M=2 ⁿ , n=0, 1, 2, . . . , and M < N, N, M are positive integers; Baseband sample sampling rate fs or M*fs;

The data transmission system according to claim 8, wherein the transmitting station comprises: a subcarrier generating unit, configured to set a virtual subcarrier at both ends of the subbands to be in the subband The edge sets the guard band.

10. A data transmission system according to claim 8 or 9, wherein:

The subband bandwidth is 20 MHz; and/or M = 1, 2, 4; and / or K = 256; and / or the baseband sample sample rate f _s = 20 MHz.

11. The data transmission system according to claim 8, wherein if the transmitting station and the receiving station support the same bandwidth, the number of IFFT/FFT subcarriers and the sampling rate of the transmitting station STA and the receiving station are the same; There are multiple transmitting sites in the system. Each transmitting site supports different bandwidths. Under the premise of meeting the bandwidth configuration requirements, multiple transmitting sites can send data to the receiving site with their respective bandwidth configurations within the bandwidth supported by the receiving site.