CN102938751A - Method and device for windowing time domains of time domain synchronization orthogonal frequency division multiplexing system - Google Patents

Abstract

The invention discloses a time-domain windowing method and device for a time-domain synchronous OFDM system. The method includes: combining the training sequence with the corresponding inverse discrete Fourier transform data block according to the system transmission parameters Generate a time-domain synchronous OFDM system signal frame, define the current frame as this frame, and define its previous and subsequent signal frames as the previous frame and subsequent frame in turn; generate the cyclic suffix of this frame and copy it to the data of this frame After the block; W/2 symbols before the training sequence of this frame and the W/2 symbols of the cyclic suffix are subjected to time-domain windowing processing, wherein W is the window length; The W/2 symbols are sequentially added in the time domain to the W/2 symbols of the cyclic suffix of the previous frame after the windowing process in the time domain. The implementation process of the invention is simple and the complexity is low. While increasing the transmission rate in the designated frequency band, the invention can also improve the flexibility, effectiveness and reliability of signal transmission, and improve the spectrum efficiency.

Description

Time Domain Windowing Method and Device for Time Domain Synchronous Orthogonal Frequency Division Multiplexing System

technical field

The present invention relates to the technical field of digital signal transmission, in particular to a time domain windowing method and a device thereof for a time domain synchronous orthogonal frequency division multiplexing (Time Domain Synchronous OFDM, TDS-OFDM) system.

Background technique

At present, the main problem to be solved by broadband wireless communication technology is how to reliably increase the transmission rate within a limited bandwidth. For limited spectrum resources, it is necessary to further improve the spectrum efficiency. Requirements for 15bit/Hz and 30bit/Hz. Orthogonal Frequency Division Multiplexing (OFDM: Orthogonal Frequency Division Multiplexing) technology is widely used due to its high spectral efficiency and excellent ability to resist multipath fading, and is considered to be one of the most promising transmission technologies at present.

However, for a block transmission system, although the duration of a data block is much longer than the duration of a single symbol, there is still a non-negligible IBI (Inter Block Interference) between time domain data blocks under a large delay extension channel. , inter-block interference). An effective method for the block transmission system in the prior art to resist IBI is to add GI (Guard Interval, Guard Interval) between time domain data blocks. When the maximum multipath delay of the channel does not exceed the length of GI, the time domain data There is no interference between blocks. According to different types of GI filling content, there are a variety of GI filling technologies, including CP (Cyclic Prefix, cyclic prefix) filling technology, ZP (Zero Padding, zero filling) technology, and TS (Training Sequence, training sequence) filling technology etc. Among them, CP filling technology has been successfully applied to IEEE802.11a wireless local area network, terrestrial digital video broadcasting (Digital Video Broadcasting-Terrestrial, DVB-T) and its second generation standard DVB-T2 system and IEEE1901 and G.hn broadband power line communication system, Its frame structure is shown in Figure 1; the method based on PN (Pseudo-random Noise, pseudorandom noise) sequence filling is a special case of TS filling technology, which belongs to an important feature of the TDS-OFDM system. This technology has been successfully applied to the ground in China In the digital television transmission standard (Digital Television Multimedia Broadcast, DTMB), its frame structure is shown in Figure 2.

In broadband communication, some frequency bands are reserved for services such as amateur radio, remote control, and aerospace communication, so they cannot be interfered by strong electromagnetic radiation; however, some communications that rely on transmission media, such as PLC (Power Line Communication, Power line communication) cannot be completely shielded from the outside world, and some signals will be coupled out; in order to reduce the interference of the coupled signals to the above-mentioned important services, the reserved frequency band is generally notched. In an OFDM-based transmission system, there are generally two common notch methods: the first is to send a complete OFDM symbol, relying on a notched filter (Notched Filter, which can be implemented using IIR or FIR), but the fixed parameter notch The wave filter cannot be well adapted to the situation where the environment is changeable and the uncertainty is strong, such as the communication environment of PLC. The second is to directly turn off some subcarriers around the corresponding frequency band in OFDM, but at this time, the subcarriers need to be rolled off quickly in the frequency domain to reduce interference as much as possible and improve system spectrum utilization.

Studies have shown that with proper windowing in the time domain, OFDM subcarriers can roll off rapidly in the frequency domain, while effectively reducing subcarrier sidelobes and improving the spectral efficiency of the system. Therefore, for a digital communication transmission system based on TDS-OFDM frame structure, it is necessary to improve the flexibility, effectiveness and reliability of signal transmission through reasonable frame structure design and appropriate windowing processing, further improve spectrum efficiency, and reduce specific The interference of the transmission signal on the frequency band to the outside world.

Contents of the invention

(1) Technical problems to be solved

The purpose of the present invention is to provide a time domain windowing method and device based on Time Domain Synchronous Orthogonal Frequency Division Multiplexing (TimeDomain Synchronous OFDM, TDS-OFDM) system, so as to improve the spectrum efficiency of the system.

(2) Technical solution

In order to solve the above problems, the invention provides a time-domain windowing method of a time-domain synchronous OFDM system, comprising the following steps:

S1. According to the system transmission parameters, the training sequence and the corresponding inverse discrete Fourier transform data block are combined to generate a time-domain synchronous OFDM system signal frame, and the current time-domain synchronous OFDM signal frame is generated Defined as this frame, the previous and subsequent signal frames are defined as the previous frame and the subsequent frame in turn;

S2. Generate the cyclic suffix of this frame, and copy it after the data block of this frame;

S3. Perform time-domain windowing processing on the first W/2 symbols of the training sequence of this frame and the last W/2 symbols of the cyclic suffix, where W is the window length;

S4. Add the first W/2 symbols of the training sequence of this frame after time-domain windowing processing to the W/2 symbols of the previous frame cyclic suffix after time-domain windowing processing in the time domain.

Preferably, in the step S1, the training sequence includes m-sequence, Gold sequence, Legendre sequence, Walsh sequence, Golay sequence, cyclic extension or truncation of the above-mentioned sequence, and its discrete Fourier transform domain is the above-mentioned sequence or the above-mentioned A cyclic extension of a sequence or a truncated sequence.

Preferably, the training sequence is two identical known sequences.

Preferably, in the step S2, the cyclic suffix is the first L symbols of the data block of the current frame, and L is a positive integer.

Preferably, in the step S2, the cyclic suffix is the first L symbols of the training sequence, where L is a positive integer.

In the step S3, the time-domain windowing process is as follows: the first W/2 symbols of the training sequence of the current frame are multiplied by the first W/2 coefficients of the corresponding window function in turn, and the post-W/2 coefficients of the cyclic suffix of the current frame The W/2 symbols are sequentially multiplied by the last W/2 coefficients of the corresponding window function.

Further, after the step S4, it also includes:

S5. Perform subsequent processing operations such as shaping filtering, frequency up-conversion, and digital-to-analog conversion on the signal after time-domain windowing processing.

Preferably, the time-domain window function includes a raised cosine roll-off window, a Hamming window, a Hanning window and a Kaiser window.

Preferably, the window length W is constrained by the data block length, training sequence length or cyclic suffix length, which does not exceed 1/16 of the data block length, or does not exceed the time domain training sequence length, or does not exceed the cyclic suffix length twice as much.

The present invention also provides a time-domain windowing device of a time-domain synchronous OFDM system, the device comprising:

A time-domain synchronous OFDM frame generation module is used to generate a time-domain synchronous OFDM system signal frame after combining the training sequence and the corresponding inverse discrete Fourier transform data block according to the system transmission parameters;

The cyclic suffix generation module is connected with the TDOFDM frame generation module, and is used to copy the first L symbols of the data block of this frame or the first L symbols of the training sequence of this frame to the data block of the current frame Afterwards, the cyclic suffix of this frame is generated, and L is a positive integer;

The time-domain windowing module is connected with the cyclic suffix generation module, and is used to perform time-domain windowing processing on the W/2 symbols before the training sequence of this frame and the W/2 symbols of the cyclic suffix of this frame, and W is the window length ;

The time domain superposition module is connected with the described time domain windowing module, and is used to process the first W/2 symbols of the training sequence of this frame after the time domain windowing process and the previous frame cyclic suffix after the time domain windowing process. W/2 symbols are sequentially added in the time domain;

The subsequent processing module is connected with the time domain superposition module, and is used for performing subsequent processing operations such as shaping filtering, frequency up-conversion and digital-to-analog conversion on the signal processed by time domain windowing.

(3) Beneficial effects

Based on the time domain windowing method and device of the solution of the present invention, the communication system can obtain higher spectrum efficiency. The invention has simple implementation process and low complexity, and can be effectively used in complex wireless transmission channel environments.

Description of drawings

FIG. 1 is a schematic diagram of a CP-OFDM frame structure in the prior art;

Fig. 2 is a kind of schematic diagram of TDS-OFDM frame structure in the prior art;

Fig. 3 is a flow chart of the inventive method;

Fig. 4 is a kind of frame structure diagram based on TDS-OFDM that the present invention proposes;

Fig. 5 is a schematic diagram of a frame structure windowing method based on TDS-OFDM proposed by the present invention;

6 is a schematic diagram of a method for generating a frame cyclic suffix in Embodiments 1 and 3 of the present invention;

FIG. 7 is a schematic diagram of a method for generating a frame cyclic suffix in Embodiments 2 and 4 of the present invention;

FIG. 8 is a schematic diagram of a method for superimposing adjacent frames according to an embodiment of the present invention;

Fig. 9 is a spectrum efficiency effect diagram of a frame structure windowing method based on TDS-OFDM proposed by the present invention;

Fig. 10 is a structural diagram of the device of the present invention.

Detailed ways

The specific implementation manners of the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

Fig. 3 is the flowchart of the inventive method, specifically comprises the following steps:

S1. According to the system transmission parameters, the training sequence and the corresponding inverse discrete Fourier transform data block are combined to generate a time-domain synchronous OFDM system signal frame, and the current time-domain synchronous OFDM signal frame is generated Defined as this frame, the previous and subsequent signal frames are defined as the previous frame and the subsequent frame in turn;

S2. Generate the cyclic suffix of this frame, and copy it after the data block of this frame;

S3. Perform time-domain windowing processing on the first W/2 symbols of the training sequence of this frame and the last W/2 symbols of the cyclic suffix, where W is the window length;

S4. Add the first W/2 symbols of the training sequence of this frame after time-domain windowing processing to the W/2 symbols of the previous frame cyclic suffix after time-domain windowing processing in the time domain.

Preferably, in the step S1, the training sequence includes m-sequence, Gold sequence, Legendre sequence, Walsh sequence, Golay sequence, cyclic extension or truncation of the above-mentioned sequence, and its discrete Fourier transform domain is the above-mentioned sequence or the above-mentioned A cyclic extension of a sequence or a truncated sequence.

Preferably, the training sequence is two identical known sequences.

Preferably, in the step S2, the cyclic suffix is the first L symbols of the data block of the current frame, and L is a positive integer.

Preferably, in the step S2, the cyclic suffix is the first L symbols of the training sequence, where L is a positive integer.

In the step S3, the time-domain windowing process is as follows: the first W/2 symbols of the training sequence of the current frame are multiplied by the first W/2 coefficients of the corresponding window function in turn, and the post-W/2 coefficients of the cyclic suffix of the current frame The W/2 symbols are sequentially multiplied by the last W/2 coefficients of the corresponding window function.

Further, after the step S4, it also includes:

S5. Perform subsequent processing operations such as shaping filtering, frequency up-conversion, and digital-to-analog conversion on the signal after time-domain windowing processing.

Preferably, the time-domain window function includes a raised cosine roll-off window, a Hamming window, a Hanning window and a Kaiser window.

Preferably, the window length W is constrained by the data block length, training sequence length or cyclic suffix length, which does not exceed 1/16 of the data block length, or does not exceed the time domain training sequence length, or does not exceed the cyclic suffix length twice as much.

Example 1

Embodiment 1 specifically describes the workflow of a frame structure windowing method with a multi-frame structure and based on continuous TDS-OFDM. The frame structure in this embodiment is shown in Figure 4, and the windowing method is shown in Figure 5, wherein N1 represents the length of the first segment of the training sequence, N2 represents the length of the second segment of the training sequence, and N represents the time domain The length of the data block.

In the OFDM system, the training sequence filled in the guard interval and the OFDM data block form a signal frame, and the training sequence filled between the data blocks consists of two identical sequences in this embodiment. The frame structure windowing method specifically includes the following steps:

S1. According to the system transmission parameters, the training sequence and the corresponding inverse discrete Fourier transform data block are combined to generate a time-domain synchronous OFDM system signal frame, and the current time-domain synchronous OFDM signal frame is generated Defined as this frame, the previous and subsequent signal frames are defined as the previous frame and the subsequent frame in turn;

The training sequence used in this embodiment consists of two identical sequences. Among them, the discrete Fourier transform domain of each sequence is an m-sequence with a length of 256, that is, N1=N2=256. This sequence is an 8-order m-sequence implemented by a Fibonacci-type linear feedback shift register (LFSR). Its characteristic polynomial is defined as x ⁸ +x ⁶ +x ⁵ +x+1. Then the above m-sequence is converted into a time-domain sequence of length 256 by IDFT (Inverse Discrete Fourier Transform) with a length of 256. Then two identical time-domain sequences are combined to form a training sequence with a total length of 512.

In this embodiment, 4096 data symbols are transmitted in each frame, that is, N=4096. While generating the training sequence, generate the data bits to be transmitted in this frame, go through FEC (Forward Error Coding, forward error correction coding) and interleaving, and then perform constellation mapping to obtain 4096 transmission data symbols in this frame, and obtain the length after IDFT 4096 blocks of time domain data.

In the time domain, the TDS-OFDM system signal frame of this frame is generated after the training sequence is placed before the time domain data block and combined.

S2. Generate the cyclic suffix of this frame, and copy it after the data block of this frame;

In this embodiment, preferably, the parameter L is selected as 32, and the first 32 symbols of the data block of this frame are copied to the data block of this frame to generate a cyclic suffix of this frame, as shown in FIG. 6 . In this way, the total length of this frame becomes 256×2+4096+32=4640.

S3. Perform time-domain windowing processing on the first W/2 symbols of the training sequence of this frame and the last W/2 symbols of the cyclic suffix, where W is the window length;

In this embodiment, in order to better reduce the out-of-band power and improve the spectral efficiency while taking into account the transmission rate, preferably, a Caesar window with a beta parameter of 10 is used as the window function of the windowing process, and the window length is W, and W is affected by the data block length . Constraints on the training sequence length and the cyclic suffix length constraint. In this embodiment, W is 64.

The process of windowing in the time domain is as follows: multiply the first 32 symbols of this frame (the first 32 symbols of the training sequence of this frame) by the first 32 coefficients of the window, and multiply the last 32 symbols of this frame (the first 32 symbols of the cyclic suffix The last 32 symbols) are multiplied by the last 32 coefficients of the window respectively.

S4. Add the first W/2 symbols of the training sequence of this frame after time-domain windowing processing to the W/2 symbols of the previous frame cyclic suffix after time-domain windowing processing in the time domain.

In this embodiment, due to the frame structure of the continuous system, a certain transmission efficiency can be obtained by partial superposition of adjacent frames: the first 32 symbols of the training sequence of this frame after time-domain windowing processing and the previous frame cycle The 32 symbols of the suffix processed by windowing in the time domain are aligned and added sequentially in the time domain, as shown in Figure 8; correspondingly, the last 32 symbols of the frame cyclic suffix processed by windowing are combined with the training sequence of the rear frame The first 32 symbols after time-domain windowing are aligned and sequentially added in the time domain. After such processing, the decrease in transmission efficiency caused by time-domain windowing can be offset to a certain extent, so that the equivalent number of actual transmission symbols per frame is 256×2+4096=4608. Figure 9 shows the comparison of spectrum effects after windowing processing and without windowing processing.

In this embodiment, after superposition processing is performed on adjacent frames, shaping filtering, digital up-conversion and digital-to-analog conversion are performed in sequence, and the signal is sent out.

Example 2

Embodiment 2 specifically describes the working process of a frame structure windowing method with a multi-frame structure and based on continuous TDS-OFDM. The frame structure in this embodiment is shown in FIG. 4 , the windowing method is shown in FIG. 5 , and the description of each parameter is the same as that in Embodiment 1.

In the OFDM system, the training sequence filled in the guard interval and the OFDM data block form a signal frame, and the training sequence filled between the data blocks consists of two sequences of different lengths in this embodiment. The frame structure windowing method specifically includes the following steps:

S1. According to the system transmission parameters, the training sequence and the corresponding inverse discrete Fourier transform data block are combined to generate a time-domain synchronous OFDM system signal frame, and the current time-domain synchronous OFDM signal frame is generated Defined as this frame, the previous and subsequent signal frames are defined as the previous frame and the subsequent frame in turn;

The training sequence used in this embodiment consists of two sequences with different lengths. Among them, the first sequence is the cyclic extension of the second sequence, the second sequence is an m sequence with a length of 255, and the first sequence is a sequence composed of the last 165 symbols of the second sequence, that is, N1=165, N2=255. Then the two time-domain sequences are combined to form a training sequence with a total length of 420.

In this embodiment, 3072 data symbols are transmitted in each frame, that is, N=3072. While generating the training sequence, generate the data bits to be transmitted in this frame, go through FEC and interleaving, and then perform constellation mapping to obtain 3072 transmission data symbols in this frame, and obtain a time-domain data block with a length of 3072 after IDFT.

In the time domain, the TDS-OFDM system signal frame of this frame is generated after the training sequence is placed before the time domain data block and combined.

S2. Generate the cyclic suffix of this frame, and copy it after the data block of this frame;

In this embodiment, preferably, the parameter L is selected as 64, and the first 64 symbols of the training sequence of the frame are copied to the data block of the frame to generate the cyclic suffix of the frame, as shown in FIG. 7 . In this way, the total length of this frame becomes 165+255+3072+64=3556.

S3. Perform time-domain windowing processing on the first W/2 symbols of the training sequence of this frame and the last W/2 symbols of the cyclic suffix, where W is the window length;

In this embodiment, in order to better reduce the out-of-band power and improve the spectral efficiency while taking into account the transmission rate, preferably, a Hamming window is used as the window function of the windowing process, and the window length is W, and W is constrained by the length of the data block. More than 1/16 of the data block length, in this embodiment, W is 64.

The process of windowing in the time domain is as follows: multiply the first 32 symbols of this frame (the first 32 symbols of the training sequence of this frame) by the first 32 coefficients of the window, and multiply the last 32 symbols of this frame (the first 32 symbols of the cyclic suffix The last 32 symbols) are multiplied by the last 32 coefficients of the window respectively.

S4. Add the first W/2 symbols of the training sequence of this frame after time-domain windowing processing to the W/2 symbols of the previous frame cyclic suffix after time-domain windowing processing in the time domain.

In this embodiment, due to the frame structure of the continuous system, a certain transmission efficiency can be obtained by partial superposition of adjacent frames: the first 32 symbols of the training sequence of this frame after time-domain windowing processing and the previous frame cycle The 32 symbols of the suffix processed by windowing in the time domain are aligned and added sequentially in the time domain, as shown in Figure 8; correspondingly, the last 32 symbols of the frame cyclic suffix processed by windowing are combined with the training sequence of the rear frame The first 32 symbols after time-domain windowing are aligned and sequentially added in the time domain. After such processing, the decrease in transmission efficiency caused by time-domain windowing can be offset to a certain extent, so that the equivalent number of actual transmission symbols per frame is 165+255+3072=3492.

In this embodiment, after superposition processing is performed on adjacent frames, shaping filtering, digital-to-analog conversion, and analog up-conversion are performed in sequence, and the signals are sent out.

Example 3

Embodiment 3 specifically describes the working process of a frame structure windowing method with a multi-frame structure and based on continuous TDS-OFDM. The frame structure in this embodiment is shown in FIG. 4 , the windowing method is shown in FIG. 5 , and the description of each parameter is the same as that in Embodiment 1.

In the OFDM system, the training sequence filled in the guard interval and the OFDM data block form a signal frame, and the training sequence filled between the data blocks consists of two identical sequences in this embodiment. The frame structure windowing method specifically includes the following steps:

S1. According to the system transmission parameters, the training sequence and the corresponding inverse discrete Fourier transform data block are combined to generate a time-domain synchronous OFDM system signal frame, and the current time-domain synchronous OFDM signal frame is generated Defined as this frame, the previous and subsequent signal frames are defined as the previous frame and the subsequent frame in turn;

The training sequence used in this embodiment consists of two identical sequences. Among them, the discrete Fourier transform domain of each sequence is a Walsh sequence with a length of 512, that is, N1=N2=512. Then, the above-mentioned Walsh sequence is transformed into a time-domain sequence with a length of 512 by IDFT with a length of 512. Then two identical time-domain sequences are combined to form a training sequence with a total length of 1024.

In this embodiment, each frame transmits 8192 data symbols, that is, N=8192. While generating the training sequence, generate the data bits to be transmitted in this frame, go through FEC and interleaving, and then perform constellation mapping to obtain 8192 transmission data symbols in this frame, and obtain a time-domain data block with a length of 8192 after IDFT.

In the time domain, the TDS-OFDM system signal frame of this frame is generated after the training sequence is placed before the time domain data block and combined.

S2. Generate the cyclic suffix of this frame, and copy it after the data block of this frame;

In this embodiment, preferably, the parameter L is selected as 128, and the first 128 symbols of the data block of this frame are copied to the data block of this frame to generate a cyclic suffix of this frame, as shown in FIG. 6 . In this way, the total length of this frame becomes 512×2+8192+128=9344.

S3. Perform time-domain windowing processing on the first W/2 symbols of the training sequence of this frame and the last W/2 symbols of the cyclic suffix, where W is the window length;

In this embodiment, in order to better reduce the out-of-band power and improve the spectral efficiency while taking into account the transmission rate, preferably, the Haining window is used as the window function of the windowing process, and the window length is W. W is constrained by the training length and does not exceed the training The length of the sequence, in this embodiment, W is 128.

The process of windowing in the time domain is as follows: multiply the first 64 symbols of this frame (the first 64 symbols of the training sequence of this frame) by the first 64 coefficients of the window, and multiply the last 64 symbols of this frame (the first 64 symbols of the cyclic suffix The last 64 symbols) are multiplied by the last 64 coefficients of the window respectively.

S4. Add the first W/2 symbols of the training sequence of this frame after time-domain windowing processing to the W/2 symbols of the previous frame cyclic suffix after time-domain windowing processing in the time domain.

In this embodiment, due to the frame structure of the continuous system, a certain transmission efficiency can be obtained by partial superposition of adjacent frames: the first 64 symbols of the training sequence of this frame after time-domain windowing processing and the previous frame cycle The 64 symbols of the suffix after windowing in the time domain are aligned and added sequentially in the time domain, as shown in Figure 8; correspondingly, the last 64 symbols of the frame cyclic suffix after windowing are combined with the training sequence of the rear frame The first 64 symbols after time-domain windowing are aligned and sequentially added in the time domain. After such processing, the decrease in transmission efficiency caused by time-domain windowing can be offset to a certain extent, so that the equivalent number of actual transmission symbols per frame is 512×2+8192+128-64=9280.

In this embodiment, after superposition processing is performed on adjacent frames, shaping filtering, digital up-conversion and digital-to-analog conversion are performed in sequence, and then the signal is sent out.

Example 4

Embodiment 4 specifically describes the workflow of a frame structure windowing method with a multi-frame structure and based on burst TDS-OFDM. The frame structure in this embodiment is shown in FIG. 4 , the windowing method is shown in FIG. 5 , and the description of each parameter is the same as that in Embodiment 1.

In the OFDM system, the training sequence filled in the guard interval and the OFDM data block form a signal frame, and the training sequence filled between the data blocks consists of two identical sequences in this embodiment. The frame structure windowing method specifically includes the following steps:

S1. According to the system transmission parameters, the training sequence and the corresponding inverse discrete Fourier transform data block are combined to generate a time-domain synchronous OFDM system signal frame, and the current time-domain synchronous OFDM signal frame is generated Defined as this frame, the previous and subsequent signal frames are defined as the previous frame and the subsequent frame in turn;

The training sequence used in this embodiment consists of two identical sequences. Among them, each sequence is a Legendre sequence with a length of 512, that is, N1=N2=512. Then two identical sequences are combined to form a time-domain training sequence with a total length of 1024.

In this embodiment, each frame transmits 8192 data symbols, that is, N=8192. While generating the training sequence, generate the data bits to be transmitted in this frame, go through FEC and interleaving, and then perform constellation mapping to obtain 8192 transmission data symbols in this frame, and obtain a time-domain data block with a length of 8192 after IDFT.

In the time domain, the TDS-OFDM system signal frame of this frame is generated after combining the time domain training sequence before the time domain data block.

S2. Generate the cyclic suffix of this frame, and copy it after the data block of this frame;

In this embodiment, the parameter L is selected as 64, and the first 64 symbols of the training sequence of the current frame are copied to the data block of the current frame to generate a cyclic suffix of the current frame, as shown in FIG. 7 . In this way, the total length of this frame becomes 512×2+8192+64=9280.

S3. Perform time-domain windowing processing on the first W/2 symbols of the training sequence of this frame and the last W/2 symbols of the cyclic suffix, where W is the window length;

In this embodiment, in order to better reduce the out-of-band power and improve the spectral efficiency while taking into account the transmission rate, preferably, the Hanning window is used as the window function of the windowing process, and the window length is W, and W is constrained by the length of the cyclic suffix. More than twice the length of the cyclic suffix, in this embodiment, W is 32.

The process of windowing in the time domain is as follows: multiply the first 32 symbols of the frame data (the first 32 symbols of the training sequence of the frame) by the first 32 coefficients of the window, and multiply the last 32 symbols of the frame data (data The last 32 symbols of the cyclic suffix) are multiplied by the last 32 coefficients of the window respectively.

S4. Add the first W/2 symbols of the training sequence of this frame after time-domain windowing processing to the W/2 symbols of the previous frame cyclic suffix after time-domain windowing processing in the time domain.

In this embodiment, due to the frame structure of the burst system, there is no adjacent frame for partial superposition, so this step is omitted.

In this embodiment, the frame body is sequentially subjected to shaping filtering, digital-to-analog conversion, and analog up-conversion, and the signal is sent out.

Example 5

Fig. 10 is a structural diagram of the device of the present invention. The present invention also provides a time-domain windowing device for a time-domain synchronous OFDM system, which includes:

Time Domain Synchronous Orthogonal Frequency Division Multiplexing (TDS-OFDM) frame generation module, used to generate Time Domain Synchronous Orthogonal Frequency Division Multiplexing after combining the training sequence and the corresponding inverse discrete Fourier transform data block according to the system transmission parameters Use (TDS-OFDM) system signal frame;

The cyclic suffix generation module is connected with the TDOFDM frame generation module, and is used to copy the first L symbols of the data block of this frame or the first L symbols of the training sequence of this frame to the data block of the current frame Afterwards, the cyclic suffix of this frame is generated, and L is a positive integer;

The time-domain windowing module is connected with the cyclic suffix generation module, and is used to perform time-domain windowing processing on the W/2 symbols before the training sequence of this frame and the W/2 symbols of the cyclic suffix of this frame, and W is the window length ;

The time domain superposition module is connected with the described time domain windowing module, and is used to process the first W/2 symbols of the training sequence of this frame after the time domain windowing process and the previous frame cyclic suffix after the time domain windowing process. W/2 symbols are sequentially added in the time domain;

The subsequent processing module is connected with the time domain superposition module, and is used for performing subsequent processing operations such as shaping filtering, frequency up-conversion and digital-to-analog conversion on the signal processed by time domain windowing.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the present invention, some improvements and replacements can also be made, these improvements and replacements It should also be regarded as the protection scope of the present invention.

Claims (10)

1. a time domain windowing method of time domain synchronous OFDM system, is characterized in that, comprises the following steps: S1. According to the system transmission parameters, the training sequence and the corresponding inverse discrete Fourier transform data block are combined to generate a time-domain synchronous OFDM system signal frame, and the current time-domain synchronous OFDM signal frame is generated Defined as this frame, the previous and subsequent signal frames are defined as the previous frame and the subsequent frame in turn; S2. Generate the cyclic suffix of this frame, and copy it after the data block of this frame; S3. Perform time-domain windowing processing on the first W/2 symbols of the training sequence of this frame and the last W/2 symbols of the cyclic suffix, where W is the window length; S4. Add the first W/2 symbols of the training sequence of this frame after time-domain windowing processing to the W/2 symbols of the previous frame cyclic suffix after time-domain windowing processing in the time domain. 2. the method for claim 1 is characterized in that, in described step S1, described training sequence comprises m sequence, Gold sequence, Legendre sequence, Walsh sequence, Golay sequence, the cyclic extension or truncation of above-mentioned sequence, and Its discrete Fourier transform domain is the above sequence or a cyclically extended or truncated sequence of the above sequence. 3. The method according to claim 1, wherein the training sequence is two identical known sequences. 4. The method according to claim 1, wherein in the step S2, the cyclic suffix is the first L symbols of the data block of the current frame, and L is a positive integer. 5. The method according to claim 1, wherein in the step S2, the cyclic suffix is the first L symbols of the training sequence, and L is a positive integer. 6. The method according to claim 1, characterized in that, in the step S3, the time-domain windowing process is: the W/2 symbols before the training sequence of the frame are multiplied by the corresponding window function successively For the first W/2 coefficients, the last W/2 symbols of the cyclic suffix of the current frame are multiplied by the last W/2 coefficients of the corresponding window function in turn. 7. The method according to claim 1, further comprising after the step S4: S5. Perform subsequent processing operations such as shaping filtering, frequency up-conversion, and digital-to-analog conversion on the signal after time-domain windowing processing. 8. The method according to claim 1 or 6, wherein the time domain window function comprises a raised cosine roll-off window, a Hamming window, a Hanning window and a Kaiser window. 9. The method according to claim 1 or 6, wherein the window length W is constrained by the data block length, training sequence length or cyclic suffix length, and it does not exceed 1/16 of the data block length, or Not exceeding the length of the time-domain training sequence, or not exceeding twice the length of the cyclic suffix. 10. A time-domain windowing device of a time-domain synchronous OFDM system, characterized in that the device comprises: A time-domain synchronous OFDM frame generation module is used to generate a time-domain synchronous OFDM system signal frame after combining the training sequence and the corresponding inverse discrete Fourier transform data block according to the system transmission parameters; The cyclic suffix generation module is connected with the TDOFDM frame generation module, and is used to copy the first L symbols of the data block of this frame or the first L symbols of the training sequence of this frame to the data block of the current frame Afterwards, the cyclic suffix of this frame is generated, and L is a positive integer; The time-domain windowing module is connected with the cyclic suffix generation module, and is used to perform time-domain windowing processing on the W/2 symbols before the training sequence of this frame and the W/2 symbols of the cyclic suffix of this frame, and W is the window length ; The time domain superposition module is connected with the described time domain windowing module, and is used to process the first W/2 symbols of the training sequence of this frame after the time domain windowing process and the previous frame cyclic suffix after the time domain windowing process. W/2 symbols are sequentially added in the time domain; The subsequent processing module is connected with the time domain superposition module, and is used for performing subsequent processing operations such as shaping filtering, frequency up-conversion and digital-to-analog conversion on the signal processed by time domain windowing.

Images