CN102594745B - Synchronization method for single carrier frequency domain equalization system and realization circuit thereof - Google Patents

Abstract

The invention discloses a synchronization method in a single-carrier frequency domain equalization system, which includes a multiplexing technology based on training words and a bit synchronization method. The method adds three training words at the frame header, which are used to complete various synchronization and channel estimation algorithms, thereby reducing the burden of the frame header and improving the effective transmission rate of data; the present invention proposes a bit synchronization algorithm, The algorithm is divided into initial synchronization and precise synchronization. After the initial synchronization range is determined, the precise synchronization algorithm is used to find the precise synchronization position within this range. There will be no other peaks in the position, and it has a more accurate bit synchronization position judgment ability, and also has higher work efficiency.

Description

Synchronization Method and Realization Circuit in Single Carrier Frequency Domain Equalization System

technical field

The present invention relates to the field of wireless communication, such as wireless sensor network, broadband wireless communication system, etc., and in particular to a synchronization method based on Single Carrier System with Frequency Domain Equalization (SC-FDE) technology.

Background technique

Wireless communication has experienced rapid development from analog communication to digital communication, from FDMA to CDMA, and is an industry with the fastest technology update and the largest market capacity. With the development of wireless communication today, more and more services have put forward higher and higher requirements for data transmission rate, and the severe shortage of spectrum resources has increasingly become a bottleneck restricting the development of wireless communication. Although the second-generation mobile communication can be thousands of times faster than the existing transmission rate, it still cannot meet the requirements of future multimedia communication. Therefore, how to fully develop and utilize limited spectrum resources and improve spectrum utilization has become one of the hotspots in wireless communication technology research today. While improving the utilization rate of frequency potential, it is also an important issue to ensure the reliability of transmission. Future wireless communication applications have higher requirements on the application environment, which requires new wireless communication technologies to adapt to harsher channels and overcome various adverse effects.

Wireless communication technology is used in many different systems, such as wireless sensor network, broadband wireless communication system and so on. Wireless sensor network (WSN) is a brand-new information acquisition platform, which can monitor and collect information of various detection objects in the network distribution area in real time, and send the information to the gateway node to realize complex target detection within the specified range. It has the characteristics of rapid deployment and strong invulnerability, and has broad application prospects. With the development of wireless sensor networks, high-speed data transmission becomes very necessary, especially the transmission of burst data packets, which needs to meet the application requirements of flexible deployment of sensor networks, low cost, and small size. In addition, broadband wireless digital communication is also the development frontier of current wireless communication technology, and has broad application prospects in future comprehensive services such as voice, video, data and multimedia.

The representative research on the bit synchronization of single-carrier frequency domain equalization is "Frequency Domain Equalization for Single-Carrier Broadband Wireless Systems "paper, the paper proposes single-carrier frequency domain equalization (SC-FDE) technology, which can be flexibly used in wireless sensor networks, broadband wireless communication and other systems, and it has a low The peak-to-average ratio and sensitivity to phase noise reduce the power consumption and cost of analog devices such as power amplifiers; and under the propagation conditions of time delay spread, the SC-FDE system can obtain performance similar to that of the OFDM system; at the same time, the SC-FDE system -The structure of the transmitting end of the FDE system is simple, which reduces the power consumption of the transmitting end. Therefore, the SC-FDE system can be widely used in wireless communication systems. Afterwards, some literatures appeared one after another, discussing each key technology in SC-FDE system deeply.

In SC-FDE system, synchronization is an extremely critical step. SC-FDE systems are very sensitive to synchronization errors (especially bit synchronization errors). For the phase deviation of the sampling clock, after being transformed into the frequency domain by FFT, it is equivalent to the phase rotation of each symbol, which is multiplicative interference, which can be corrected by frequency domain equalization; the frequency deviation of the sampling clock is transformed into the frequency domain It is equivalent to the introduction of inter-carrier interference, which cannot be compensated by frequency domain equalization. Moreover, the signal after IFFT transformation back to the time domain also has bit synchronization errors, which greatly interferes with the decision. In addition, the frequency offset (frequency offset) of the sampling clock will also cause timing drift of the signal, which will affect the synchronization performance. Therefore, the synchronization module of the SC-FDE system, especially the bit synchronization module, is one of the key technologies of the whole system design.

Contents of the invention

In order to solve the above-mentioned problems existing in the prior art, the present invention proposes a new bit synchronization method based on single-carrier frequency domain equalization technology, and the specific technical scheme is as follows:

Using a multiplexing technology based on training words, three sets of training sequences are used to realize the synchronization in the single carrier frequency domain equalization (SC-FDE) system. Specifically, the preamble of the frame structure in the SC-FDE system is divided into 3 training sequences TS1, TS2 and TS3;

In the algorithm of synchronization and channel estimation, there are non-data-assisted algorithm and data-assisted algorithm. The non-data-assisted algorithm generally converges slowly, and the algorithm implementation is more complicated. Therefore, this paper adopts the data-assisted algorithm. Algorithm, its convergence speed is faster, suitable for higher rate data transmission. In the data-assisted algorithm, it is generally performed by inserting a training sequence at the frame header position. Each training sequence is composed of different training words, which is a sequence known by both the sending end and the receiving end. Each training word is composed of a unique word (Unique Word, UW), which requires randomness in the time domain and a flat amplitude response in the frequency domain. UW consists of a constant envelope zero autocorrelation (Constant Amplitude and ZeroAutoCorrelation, CAZAC) sequence to fulfill. The training sequence thus formed is less affected by noise and frequency offset, and is very suitable for synchronization and channel estimation algorithms.

The first training sequence TS1 is composed of a series of repeated short training words, which are used for frame arrival detection, coarse sampling synchronization, and coarse frequency offset estimation.

The second training sequence TS2 can be divided into 4 parts, and the length of each part is 1/4 of the length N of the data block. This section is used for bit synchronization.

The third training sequence TS3 consists of two identical training words and is used for fine frequency offset estimation and channel estimation.

In the process of synchronization at the receiving end, first use the TS1 to perform rough sampling synchronization, initially determine the sampling point, and then use the interpolation loop to adjust the sampling clock. So far, the sampling deviation has been corrected; and then through the algorithm based on window energy. Frame arrival detection, when the arrival of valid data is detected, use TS2 to perform bit synchronization, and use TS3 to perform carrier frequency offset estimation (the "carrier" here and the aforementioned and subsequent "frequency offset" are best unified into "frequency offset" from the perspective of terminology carrier frequency offset" or others).

In the process of bit synchronization using TS2, the bit synchronization algorithm based on the training sequence is adopted: the training word structure adopted by TS2 is [A -A -A A], and the algorithm of Schmidl & Cox is used first (can other algorithms be used?) , the first half of the training word and the second half of the training word are correlated, and the size of the sliding window at this time is N/2, and a measurement platform M ₀ is obtained.

Due to the existence of the cyclic prefix, M ₀ has a flat platform. On this platform, judge whether M ₀ is greater than a fixed value. When M ₀ >M _{fixed value} , continue to use the following algorithm to find the bit synchronization peak. The recommended fixed value can be set to 0.5, which is more convenient for hardware implementation.

Then use the improved Minn algorithm to perform cross-correlation calculations on the 4 training words of N/4 length to obtain the measurement platform:

$\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{<span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}$

In the present invention, such a frame structure is concise and concise, suitable for single-carrier frequency domain equalization system, and each training word can realize different functions, in addition, the same training word can be reused in different algorithms, multiplexing technology It can reduce the burden of the frame header and improve the data transmission rate.

The bit synchronization algorithm has a specific one peak value, and there are no other peaks anywhere other than the peak value. Therefore, it is beneficial to accurately judge the bit synchronization. In addition, in the process of bit synchronization, two steps of preliminary synchronization and accurate synchronization can be adopted, which can effectively accelerate the progress of bit synchronization.

Description of drawings

Figure 1 is a block diagram of a single carrier frequency domain equalization (SC-FDE) system.

FIG. 2 is a frame structure of a single-carrier frequency domain equalization system according to an embodiment of the present invention.

Fig. 3 is the structure of the first training sequence in the frame structure of the embodiment of the present invention.

Fig. 4 is the structure of the second training sequence in the frame structure of the embodiment of the present invention.

Fig. 5 is the structure of the third training sequence in the frame structure of the embodiment of the present invention.

FIG. 6 is a block diagram of a synchronization system and a circuit realization block diagram of a bit synchronization module according to an embodiment of the present invention.

FIG. 7 is a simulation diagram of bit synchronization according to an embodiment of the present invention.

Fig. 8 is a schematic structural diagram of a data buffer module.

specific implementation plan

A synchronization method in a single carrier frequency domain equalization (SC-FDE) system, which divides the preamble of the frame structure in the single carrier frequency domain equalization system into three training sequences TS1, TS2 and TS3;

Each training sequence is composed of different training words, which is a sequence known by both the sending end and the receiving end. It is less affected by noise and frequency offset, that is, frequency offset, and is suitable for synchronization and channel estimation algorithms;

The first training sequence TS1 is composed of a series of repeated short training words UW, which is used for frame arrival detection, coarse sampling synchronization and coarse carrier frequency offset estimation; the second training sequence TS2 is used for bit synchronization; the third training sequence TS3 consists of two identical training words for fine carrier frequency offset estimation;

In the synchronization process of the receiving end of the SC-FDE system, three steps are used to realize: 1) First, use TS1 to perform rough sampling synchronization, and initially determine the sampling point; then use the interpolation loop to adjust the sampling clock; and then perform frame arrival Detection; 2) When valid data is detected, use TS2 to perform bit synchronization; 3) Then use TS1 to perform coarse carrier frequency offset estimation, and use TS3 to perform fine carrier frequency offset estimation.

In step 1), TS1 performs coarse sampling synchronization: use the cross-correlation characteristics of repeated short training words to generate several peaks, and compare the size of each peak to find the position of the largest peak, where the autocorrelation property is the strongest, that is It is the initially determined sampling synchronization point; TS1 performs frame arrival detection: an algorithm based on window energy is used.

In step 2), the second training sequence TS2 column is split into 4 parts, and the length of each part of the training word is 1/4 of the data block length N of the frame structure in the SC-FDE system, and the training of TS2 is obtained by splitting The word structure is [A -A -A A].

In step 2), the process of bit synchronization using TS2 adopts a bit synchronization algorithm based on the training sequence, and the steps are as follows:

a) Using Sehmidl & Cox's algorithm, divide TS2 into two parts, namely [A -A] and [-A A]; if the length of the training sequence is N, then the length of each part in the two parts is N/2; the two parts of the training word for correlation calculation;

The correlation values for the two parts are:

$P_0\left(d\right)=\underset{m=0}{\overset{L-1}{\mathrm{\&Sigma;}}}r(d+m)*r(d+m+L),$ Among them, L=N/2;

The energy of the second part of TS2 training word [-A A] is:

${\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{<span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ;</span>$

At this time, the size of the sliding window is N/2, and a measurement platform M ₀ is obtained:

${\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; ;</span>$

b) Use the measurement platform M ₀ obtained in step a) to obtain the range that needs to be further searched:

Because of the existence of the cyclic prefix, M ₀ has a flat platform. On this platform, it is judged whether M ₀ is greater than a certain fixed value M _{fixed value} . When M ₀ >M _{fixed value} , continue to use the following steps 2.3) to find bit sync peak;

c) Use the improved Minn algorithm to perform cross-correlation operations on the 4 training words A, -A, -A and A of N/4 length, and consider the influence of the peak value after filtering out the edge, the cross-correlation algorithm used is as follows :

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; *</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; 4</span>}}\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; *</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 4</span>}}\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; *</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; *</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 4</span>}}\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; 4</span>}}\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span>$

from that we get:

P(d)＝P ₁ (d)+P ₂ (d)-P ₃ (d)-P ₄ (d)

$\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{<span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}$

Finally, the metrics platform is derived:

$\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{<span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; .</span>$

For simplicity of hardware implementation, the fixed value M _{is fixed at} 0.5.

Step 3) in, TS3 is made up of two identical long training words, and total length is set as N, then the length of each long training word is N/2, is used for fine carrier frequency offset estimation; In the whole carrier frequency offset estimation In the process, the last two short training words of TS1 are used for coarse carrier frequency offset estimation, and the TS3 training sequence is used for fine carrier frequency offset estimation.

Specifically in this example, the present invention will be further described below in conjunction with the accompanying drawings.

Figure 1 is a block diagram of a single carrier frequency domain equalization (SC-FDE) system. SC-FDE's single-carrier transmission mode is different from other traditional single-carrier transmissions. It sends modulated high-speed single-carrier signals. The receiving end uses FFT and IFFT transformations to achieve frequency domain equalization, which is actually for the received signals. Frequency domain analysis. This technology is based on the inspiration of OFDM, and adopts frequency domain equalization to greatly reduce the complexity of time domain equalization and improve system performance. The technical proposal of the present invention is used for the synchronization part of the system.

The frame structure of the single-carrier frequency domain equalization system in this example is shown in Figure 2, which includes a preamble and a data block. The preamble is divided into 3 training sequences:

The first training sequence TS1 is composed of a series of repeated short training words UW, as shown in FIG. 3 .

The second training sequence TS2 can be divided into 4 parts, and the length of each part is 1/4 of the length N of the data block. This part is used for bit synchronization, as shown in Figure 4.

The third training sequence TS3 consists of two identical training words, as shown in Figure 5.

All training sequences TS1, TS2 and TS3 use the aforementioned CAZAC sequence, which has a stable amplitude response and is only autocorrelated at zero point, so it has good autocorrelation characteristics and is very suitable for synchronization and channel estimation.

The present invention includes a multiplexing technology based on training words and a bit synchronization algorithm, which will be described respectively below.

1. The present invention proposes a kind of multiplexing technique based on training words, realizes synchronization with three training words, and specific content is as follows:

In the synchronization process of the receiving end, first use the first training sequence (TS1) for rough sampling synchronization, initially determine the sampling synchronization point, and then use the interpolation loop to adjust the sampling clock. So far, the sampling deviation has been corrected. Then, frame arrival detection is performed through an algorithm based on window energy. When the arrival of valid data is detected, the second training sequence (TS2) is used for bit synchronization, and then TS1 is used for coarse carrier frequency offset estimation, and TS3 is used for fine carrier frequency offset. It is estimated that the circuit structure diagram of the synchronization module is shown in Figure 6.

In this process, TS1 is first used for coarse sampling synchronization. Because the sampling clock adjustment module needs a certain stabilization time, in order to shorten this delay, we use the coarse sampling synchronization module to preliminarily determine the sampling position. In the process of rough sampling clock adjustment, use the correlation characteristics of the preamble sequence to generate several peaks, and compare the size of each peak to find the position of the largest peak, which is the initially determined sampling synchronization point. In the whole sampling synchronization algorithm, rough sampling synchronization is used to first determine the basic range, and then use the loop to track accurately. This method can correct sampling deviation more quickly.

Then, TS1 is used for frame arrival detection. The content is a well-known algorithm based on window energy, which can well obtain the frame arrival time.

Finally, the last 2 short training words of TS1 are used as coarse frequency offset estimation. In the process of frequency offset estimation, in order to ensure the range and accuracy of frequency offset, shorter training words are used for coarse frequency offset estimation to ensure the detection range of frequency offset, while longer training sequences are used for fine frequency offset estimation. partial estimate to ensure its accuracy. Since the short training word is short, the frequency offset estimation range is large, which is just suitable for the detection of coarse frequency offset.

TS2 is used for bit synchronization. In the bit synchronization algorithm that the present invention proposes, used Schmidl & Cox algorithm and improved Minn algorithm, these two kinds of algorithms are different for the structure requirement of training word. However, in the present invention, in order to save the additional information of the frame header, the same training word structure is adopted, and the requirements of the algorithm are met in a multiplexing manner. For the implementation of the specific algorithm, see the second content of the invention.

TS3 is used for fine frequency offset estimation. The training sequence is a long training sequence, and its purpose is to realize fine frequency offset estimation. In addition, in the subsequent channel estimation process, the training sequence is also used for estimation, thereby reducing the burden of the frame header and improving the effective transmission rate of data.

2. The present invention proposes a kind of bit synchronization algorithm based on training sequence, and specific content is as follows:

The training word structure used in this sequence is the training word structure [A -A -A A], as shown in Figure 4.

Step 1: Use the algorithm of Schmidl & Cox to divide the training word TS2 into two parts, the two parts are [A-A] and [-A A]. Assuming that the length of the training sequence is N, the length of each part is N/2. The training words of the two parts are correlated.

Observing the two parts before and after, it is found that the training words in the second part are equivalent to the negative value of the first part, that is to say, in the process of cross-correlating the two parts, there can still be a sharp correlation, the only difference is that P The value of ₀ (d) is negative. And this has no effect when calculating the measurement platform M ₀ later.

The correlation values for the two parts are:

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; )</span>$

Among them, L=N/2

The energy of the second part of the training word is:

${\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{<span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}$

At this time, the size of the sliding window is N/2, and a measurement platform M ₀ is obtained:

${\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}$

Step 2: Use the measurement platform obtained in Step 1 to obtain the scope that needs to be further searched.

Due to the existence of the cyclic prefix, M ₀ has a flat platform. On this platform, it is judged whether M ₀ is greater than a fixed value. When M ₀ >M _{fixed value} , continue to use step 3 to find the bit synchronization peak.

The determination of the measurement platform range is related to the signal-to-noise ratio, so the selection of the fixed value is also related to the signal-to-noise ratio. The recommended fixed value can be set to 0.5, which is more convenient for hardware implementation.

Step 3: Use the improved Minn algorithm to perform cross-correlation calculations on the 4 training words of N/4 length, and considering the influence of the peak value after filtering out the edge, the cross-correlation algorithm used is as follows:

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; *</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; 4</span>}}\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; *</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 4</span>}}\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; *</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; *</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 4</span>}}\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; 4</span>}}\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span>$

from that we get:

P(d)＝P ₁ (d)+P ₂ (d)-P ₃ (d)-P ₄ (d)

$\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{<span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}$

Finally, the metrics platform is derived:

$\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{<span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}$

Figure 6 is a block diagram of the circuit implementation of the bit synchronization algorithm, and Figure 7 is a simulation diagram of the bit synchronization algorithm. It can be seen from the figure that the advantage of the present invention is that the bit synchronization algorithm has a specific peak value, and there will be no other peaks in places other than the peak value. Therefore, it is beneficial to accurately judge the bit synchronization. In addition, in the process of bit synchronization, two steps of preliminary synchronization and accurate synchronization can be adopted, which can effectively accelerate the progress of bit synchronization.

Schmidl & Cox algorithm and improved Minn algorithm can adopt prior art to realize among the present invention.

A circuit for realizing the above method, comprising a coarse sampling synchronization module, a frame arrival detection module, a bit synchronization module and a carrier synchronization module; external data sequentially passes through the coarse sampling synchronization module, frame arrival detection module, bit synchronization module and carrier synchronization module Get the synchronized data;

The bit synchronization module includes a data buffer module, an initial bit synchronization module, an accurate synchronization module, a bit synchronization determination module and a control module;

The input data from the frame arrival detection module is processed by the data buffer module to obtain data A, B, r0, r1, r2 and r3; among them, A is the original data, B is the data of A after N/2 delay; r0 is Original data, r1 is the data of r0 after N/4 delay, r2 is the data of r0 after N/2 delay, r3 is the data of r0 after 3N/4 delay;

A and B are sent to the initial synchronization module, and M0 is obtained after processing;

r0, r1, r2 and r3 are passed to the accurate synchronization module, and M is processed;

M0 and M are transmitted to the bit synchronization determination module, and the synchronization position arrival signal is obtained through processing, and the signal is transmitted to the control module, and the output data enable signal is obtained through processing;

The output data enable signal controls the data buffer module, and the data buffer module outputs data to the carrier synchronization module.

The data buffer module is composed of flip-flops, and the initial bit synchronization module, accurate synchronization module, bit synchronization determination module and control module are all implemented by mapping the corresponding algorithm of the method of the present invention into a general digital control circuit.

For the data buffer module:

This module needs to generate data information A, B, r0, r1, r2, r3 after different delays for use by subsequent modules. Among them, A is the original data, B is the data after A has been delayed by N/2; r0 is the original data, r1 is the data after r0 has been delayed by N/4, and r2 is the data after r0 has been delayed by N/2 , r3 is the data of r0 after 3N/4 delay.

Since A and r0 are the same data (original data), and r2 and B are also the same data (data after N/2 delay), the circuit structure diagram of the data buffer module can be as shown in FIG. 8 . In the figure, the D flip-flop is used as a delay unit in this circuit; BitEnable is a bit enable signal.

Claims (5)

1. The synchronization method in the single carrier frequency domain equalization (SC-FDE) system is characterized in that the preamble of the frame structure in the single carrier frequency domain equalization system is divided into 3 training sequences TS1, TS2 and TS3; Each training sequence is composed of different training words, which is a sequence known by both the sending end and the receiving end. It is less affected by noise and frequency offset, that is, frequency offset, and is suitable for synchronization and channel estimation algorithms; The first training sequence TS1 is composed of a series of repeated short training words UW, which is used for frame arrival detection, coarse sampling synchronization and coarse carrier frequency offset estimation; the second training sequence TS2 is used for bit synchronization; the third training sequence TS3 consists of two identical training words for fine carrier frequency offset estimation; In the synchronization process of the receiving end of the SC-FDE system, three steps are used to realize: 1) First, use TS1 to perform rough sampling synchronization, and initially determine the sampling point; then use the interpolation loop to adjust the sampling clock; and then perform frame arrival Detection; 2) When the arrival of valid data is detected, use TS2 to perform bit synchronization; 3) Then use TS1 to perform coarse carrier frequency offset estimation, and use TS3 to perform fine carrier frequency offset estimation; In the step 2), the second training sequence TS2 column is split into 4 parts, and the length of each part of the training word is 1/4 of the data block length N of the frame structure in the SC-FDE system, and TS2 is obtained by splitting The training word structure is [A–A–A A]; Described step 2) in, utilize TS2 to carry out the process of bit synchronization and adopt the bit synchronization algorithm based on the training sequence, the steps are as follows: a) Using Schmidl&Cox's algorithm, divide TS2 into two parts, namely [A–A] and [–A A]; if the length of the training sequence is N, then the length of each part in the front and back two parts is N/ 2; The training words of the two parts are used for correlation calculation; The correlation values for the two parts are: $P_0\left(d\right)=\underset{m=0}{\overset{L-1}{\mathrm{\&Sigma;}}}r{(d+m)}^{*}r(d+m+L),$ Among them, L=N/2; The energy of the training word [–A A] in the second part of TS2 is: ${\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{<span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ;</span>$ At this time, the size of the sliding window is N/2, and a measurement platform M ₀ is obtained: ${\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; ;</span>$ b) Use the measurement platform M ₀ obtained in step a) to obtain the range that needs to be further searched: Because of the existence of the cyclic prefix, M ₀ has a flat platform. On this platform, it is judged whether M ₀ is greater than a certain fixed value M _{fixed value} . When M ₀ >M _{fixed value} , continue to use the following steps c) to find bit sync peak; c) Use the improved Minn algorithm to perform cross-correlation operations on the 4 training words A, –A, –A, and A of N/4 length, and consider the influence of the peak value after filtering out the edge, the cross-correlation algorithm used is as follows : ${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; 4</span>}}\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span>$ ${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 4</span>}}\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span>$ ${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span>$ ${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; r</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 4</span>}}\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; 4</span>}}\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span>$ from that we get: P(d)＝P ₁ (d)+P ₂ (d)-P ₃ (d)-P ₄ (d) $\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{<span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}$ Finally, the metrics platform is derived: $\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{<span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; .</span>$ 2. the synchronization method in the single-carrier frequency domain equalization system according to claim 1, is characterized in that in described step 1), TS1 carries out coarse sampling synchronization: utilize the cross-correlation characteristic of repeated short training word to produce several peak values , and compare the size of each peak value to find the position of the largest peak value. The autocorrelation characteristic at the largest peak value is the strongest, which is the initially determined sampling synchronization point; TS1 performs frame arrival detection: an algorithm based on window energy is used. 3. The synchronization method in the single-carrier frequency domain equalization system according to claim 1, wherein the fixed value M _is 0.5 for the sake of simplicity in hardware implementation. 4. the synchronization method in the single-carrier frequency domain equalization system according to claim 1, is characterized in that described step 3) in, TS3 is made up of two identical long training words, and total length is set as N, then each The length of the long training word is N/2, which is used for fine carrier frequency offset estimation; In the whole process of carrier frequency offset estimation, the last two short training words of TS1 are used for coarse carrier frequency offset estimation, and TS3 training sequence is used for fine carrier frequency offset estimation. 5. A circuit for realizing any one of claims 1 to 4, characterized in that it comprises a coarse sampling synchronization module, a frame arrival detection module, a bit synchronization module and a carrier synchronization module; external data passes through the coarse sampling synchronization module successively , The frame arrival detection module, the bit synchronization module and the carrier synchronization module obtain the synchronized data; The bit synchronization module includes a data buffer module, an initial bit synchronization module, an accurate synchronization module, a bit synchronization determination module and a control module; The input data from the frame arrival detection module is processed by the data buffer module to obtain data A, B, r0, r1, r2 and r3; among them, A is the original data, B is the data of A after N/2 delay; r0 is Original data, r1 is the data of r0 after N/4 delay, r2 is the data of r0 after N/2 delay, r3 is the data of r0 after 3N/4 delay; A and B are sent to the initial synchronization module, and M0 is obtained after processing; r0, r1, r2 and r3 are passed to the accurate synchronization module, and M is processed; M0 and M are transmitted to the bit synchronization determination module, and the synchronization position arrival signal is obtained through processing, and the signal is transmitted to the control module, and the output data enable signal is obtained through processing; The output data enable signal controls the data buffer module, and the data buffer module outputs data to the carrier synchronization module.