CN106792837A - A kind of up-downgoing changing method of TD LTE systems - Google Patents

Abstract

The invention discloses an uplink and downlink switching method of a TD-LTE system. The invention realizes the ratio of uplink and downlink subframes and special subframes of TD-LTE signals step by step through the joint detection method of envelope detection and CP detection. The length of the DwPTS is detected in order to obtain the uplink and downlink ratio information of the TD-LTE signal, and the uplink and downlink switching points are searched by counting to realize accurate uplink and downlink switching. The present invention solves the accuracy problem of envelope detection while realizing the search of the uplink and downlink switching points, has low complexity and is easy to implement in engineering.

Description

A TD-LTE system uplink and downlink switching method

technical field

The invention relates to the field of wireless communication, in particular to an uplink and downlink switching method of a TD-LTE system.

Background technique

As people's demand for broadband mobile communication data services continues to increase, the LTE (Long Term Evolution) system has been widely deployed and is still in the process of development. According to different duplex modes, the LTE system is further divided into a time-division duplex TD-LTE system and a frequency-division duplex FDD-LTE system. In the TD-LTE system, the uplink and downlink work in the same frequency band, and the uplink and downlink are distinguished by time division multiplexing. One of the obvious advantages of the TDD system compared to the FDD system is that the TDD system can flexibly set the ratio of uplink and downlink subframes to meet the needs of different scenarios such as uplink and downlink traffic, coverage, capacity, and coexistence of adjacent frequencies.

The radio frame in the TD-LTE system has a frame length of 10ms and includes 10 equal-length subframes, each of which includes 14 OFDM symbols. The subframe types include downlink transmission subframes, uplink transmission subframes and special subframes, and the ratio configuration of uplink and downlink subframes in a TD-LTE signal frame is shown in Table 1. In Table 1, the downlink transmission subframe is represented by 'D'; the uplink transmission subframe is represented by 'U'; the special subframe is represented by 'S'. The special subframe includes three special time slots, DwPTS, GP, and UpPTS, respectively representing downlink pilot time slots, guard intervals, and uplink pilot time slots. TD-LTE supports 7 types of uplink and downlink subframe configurations, as shown in Table 1; TD-LTE also supports 9 special subframe configurations, as shown in Table 2. When the ratio of DwPTS:GP:UpPTS in a special subframe is 10:3:1, the frame structure is shown in FIG. 1 .

Table 1: TD-LTE signal frame uplink and downlink subframe ratio configuration

Table 2: Special subframe configuration in TD-LTE signal frame

The uplink and downlink switching of the TD-LTE system needs to obtain the uplink and downlink subframe ratio information of the above TD-LTE signal frame and the DwPTS length information in the special subframe, and then calculate the position of the uplink and downlink switching point. Usually, the user terminal needs to decipher the system information SIB1 to obtain the uplink and downlink subframe ratio. The terminal first needs to complete the synchronization of PSCH and SSCH, and then obtains PHICH related information by demodulating PBCH, and then addresses PDCCH to resolve SIB1 on PDSCH to obtain the TDD time slot format of the current cell. The complexity of this method of demodulating the system information SIB is too high. Another method of envelope detection is proposed because of its low complexity. The envelope detection method judges the time slot format of the TDD frame by performing power statistics on the data. Although this envelope detection method has low complexity, it cannot guarantee the switching position accuracy.

Contents of the invention

Purpose of the invention: In order to solve the technical problems of obtaining the uplink and downlink subframe ratio information of the TD-LTE signal frame and the DwPTS length information in the special subframe in the prior art, the steps are cumbersome and the position accuracy is low. The present invention proposes a TD-LTE The uplink and downlink switching method of the system. This TD-LTE system uplink and downlink switching method solves the accuracy problem of envelope detection through the joint detection method of envelope detection and CP detection, and provides a TD-LTE with low cost and low implementation complexity while ensuring synchronization accuracy Uplink and downlink switching methods.

Technical scheme: in order to realize above-mentioned technical effect, the technical scheme that the present invention proposes is:

A method for uplink and downlink switching of a TD-LTE system, the method comprising the following steps:

Step S1, perform power statistics on the received data of any wireless frame length in the TD-LTE system in units of subframes, and determine the uplink and downlink subframe ratio of the wireless frame;

Step S2, calculating the DwPTS length in the special subframe of the wireless frame;

Step S3, calculating the switch point position from downlink to uplink in the wireless frame, including the initial switch point position and the general switch point position, and completing the downlink to uplink switch point position on the initial switch point position and the general switch point position Link switching; where,

The formula for calculating the position of the initial switch point from the downlink to the uplink is:

In the formula, Indicates the downlink to uplink initial switching point position, Represents the symbol timing position obtained through primary synchronization detection, N represents the length of an OFDM symbol, N _CP represents the length of the CP, and n _DwPTS represents the number of DwPTS symbols in the special subframe;

The formula for calculating the position of the general switching point from the downlink to the uplink is:

In the formula, Indicates the downlink to uplink general switching point location; Indicates the previous uplink-to-downlink switch point position of the current downlink-to-uplink general switch point; n _DwSubFr indicates the downlink subframe between the special subframe and the previous uplink subframe in the radio frame number of frames;

S4. According to the initial switch point position and general switch point position from downlink to uplink obtained in step S3, calculate the switch point position from uplink to downlink in the wireless frame, and Complete the switch from the uplink to the downlink at the switching point position of the link; the calculation formula of the switching point position from the uplink to the downlink is:

In the formula, Indicates the initial switch point position from uplink to downlink, Indicates the general switching point position from uplink to downlink; _nUpSubFr indicates the number of uplink subframes between a special subframe and a downlink subframe after the special subframe in the radio frame.

Further, the calculation of the DwPTS length in the special subframe of the wireless frame in the step S2 includes the following steps:

Step S2-1, in the special subframe, perform power value statistics in units of OFDM symbols, and preliminarily determine the length of the DwPTS;

Step S2-2, perform OFDM symbol CP detection at the boundary of the preliminary judgment result obtained in step S2-1, and further accurately determine the length of the DwPTS;

Step S2-3, accumulating the detection results of M times of OFDM symbol CP detection, if the DwPTS length in the special subframe is the same in the N detection results, it is determined that the DwPTS length in the special subframe is obtained successfully; otherwise, return to step S2-1 ; M is the number of detections of the preset OFDM symbol CP detection.

Beneficial effects: Compared with the method of demodulating the SIB to obtain the position of the uplink and downlink switching points, the present invention has lower cost, lower complexity, and is easier for engineering implementation; compared with the method of determining the position of the uplink and downlink switching points by envelope detection, the accuracy higher. The TD-LTE uplink and downlink switching method of the present invention is a TD-LTE uplink and downlink switching method with simple implementation, low implementation cost and the ability to ensure the position accuracy of the switching point.

Description of drawings

Fig. 1 is a schematic diagram of a TD-LTE frame structure;

Fig. 2 is a schematic flow chart of an embodiment of the present invention;

FIG. 3 is a schematic flow diagram of determining the length of DwPTS in a special subframe through joint detection of envelope detection and CP detection in an embodiment of the present invention;

Figure 4 is a schematic diagram of the timing position of the TD-LTE primary synchronization symbol;

Fig. 5 is a schematic diagram of the position of the TD-LTE uplink and downlink switching points.

detailed description

The present invention will be further explained below in conjunction with the accompanying drawings.

As shown in Figure 2, it is a flowchart of an embodiment of the present invention, and this embodiment includes the following steps:

Step S1, perform power statistics on the received data with a length of one wireless frame in units of subframes, and determine the ratio of uplink and downlink subframes of the wireless frame.

Step S2, through the joint detection method of envelope detection and CP detection, determine the length of the DwPTS in the special subframe, the specific steps are:

Step S2-1, in the special subframe, perform power value statistics in units of OFDM symbols, and preliminarily determine the length of the DwPTS;

Step S2-2, performing OFDM symbol CP detection at the preliminary judgment boundary obtained in step S2-1, to more accurately determine the length of the DwPTS;

Step S2-3, accumulating M valid detection results, if the DwPTS length in the special subframe detected by these M times is consistent, it is considered that the DwPTS length in the special subframe has been obtained successfully; otherwise, return to step S2-1 and repeat step S2- 1 to S2-3.

Step S3, when the system is switching from downlink to uplink for the first time, the initial switching point position from downlink to uplink is obtained according to the calculation method of initial switching point position from downlink to uplink, After the system completes the first downlink-to-uplink handover, the position of the general handover point from the downlink to the uplink is obtained according to the general handover point position calculation method from the downlink to the uplink, and the The handover from downlink to uplink is done at the initial handover point and the general handover point.

The search for the initial switch point from downlink to uplink is based on the TD-LTE signal uplink and downlink ratio obtained in step S1 and the DwPTS length in the special subframe obtained in step S2.

Calculation method of initial switching point position from downlink to uplink:

Calculate symbol timing position obtained from master sync detection For the time interval to the initial switching point position of downlink switching to uplink, set the counter to start counting from the symbol timing position obtained by the master synchronization detection until the initial switching point of downlink switching to uplink. Note that the symbol timing position obtained by master sync detection is The length of an OFDM symbol (FFT size) is N, the CP length is N _Cp , the number of DwPTS symbols in a special subframe is n _DwPTS , and the switch point position from downlink to uplink is Their calculation relationship is shown in formula 1:

Calculation method of the general switching point position for switching from downlink to uplink:

Write down the position of the general switching point from uplink to uplink as The previous uplink to downlink switching point position is The number of DE downlink subframes between the special subframe in the TD-LTE signal frame and the uplink subframe before the special subframe is n _DwSubFr , and the FFT size of a subframe is 30720 sampling points, then the general switching from uplink to downlink The point position calculation formula is shown in formula 2:

Step S4, counting from the switch point from the downlink to the uplink, calculating the switch point from the uplink to the downlink, and completing the switch from the uplink to the downlink at the switch point.

The calculation of the switching point from the uplink to the downlink is based on the TD-LTE signal uplink and downlink ratio obtained in step S1, the DwPTS length in the special subframe obtained in step S2, and the downlink to uplink switch obtained in step S3. The switch point position of the road. The switch point position for each uplink to downlink switch is calculated as follows:

Here, record the position of the previous downlink to uplink switching point as The position of the uplink to downlink switching point is The number of uplink subframes between the special subframe in the TD-LTE signal frame and the downlink subframe after the special subframe is n _UpSubFr , the FFT size of a subframe is 30720 sampling points, and the position of the switching point from uplink to downlink is calculated The formula is shown below:

In the formula, Indicates the initial switch point position from uplink to downlink, Indicates the general switching point position from uplink to downlink; _nUpSubFr indicates the number of uplink subframes between a special subframe and a downlink subframe after the special subframe in the radio frame.

Set the counter to the previous downlink-to-uplink switchpoint from the currently searched uplink-to-downlink switchpoint Start counting until the

As shown in Figure 3, the specific steps for determining the length of DwPTS in a special subframe by the joint detection method of envelope detection and CP detection in S2 include:

Step S2-1, in the special subframe, perform power value statistics in units of OFDM symbols, and preliminarily determine the length of the DwPTS;

Step S2-2, performing OFDM symbol CP detection at the preliminary judgment boundary obtained in step S2-1, to more accurately determine the length of the DwPTS;

Step S2-3: Accumulate valid detection results for N times. If the results of the DwPTS length in the special subframe detected by the N times are consistent, it is considered that the DwPTS length in the special subframe has been obtained successfully; otherwise, return to step S2-1 and repeat steps S2-1 to S2-3.

The method for calculating the position of the uplink and downlink switching points will be explained in detail below according to FIG. 4 and FIG. 5 .

Figure 4 shows a schematic diagram of the TD-LTE primary synchronization symbol timing position, and the symbol timing position obtained by the primary synchronization detection It is located after the third CP of the DwPTS in the special subframe.

Figure 5 is a schematic diagram of the location of the TD-LTE uplink and downlink switching points, and the location of the switching point from the uplink to the downlink And its corresponding initial switch point position from downlink to uplink Located after the end of DwPTS in the same special subframe, and The distance is N+(n _DwPTS -3)·(N _CP +N), where the length of one OFDM symbol (FFT size) is N, the CP length is N _CP , and the number of DwPTS symbols in the special subframe is n _DwPTS .

Downlink to uplink switch point Interval 30720 n _UpSubFr +[30720-n _DwPTS (N _CP +N)], where n _UpSubFr is the number of uplink subframes, 30720 is the FFT size of a subframe, [30720-n _DwPTS (N _CP +N )] represents the sum of the lengths of GP and UpPTS in a special subframe. The same method can be obtained from Calculate the next switch position

In actual application, the uplink and downlink switching points searched by the TD-LTE uplink and downlink switching method of the present invention can properly delay a plurality of FFT sample points to ensure complete reception of uplink and downlink signals.

The above descriptions only express several implementations of the present invention, and the descriptions thereof are relatively specific and detailed, but should not be construed as limiting the patent scope of the present invention. It should be pointed out that those skilled in the art can make some improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims (2)

1. a method for switching between uplink and downlink of TD-LTE system, is characterized in that, comprises the following steps: Step S1, perform power statistics on the received data of any wireless frame length in the TD-LTE system in units of subframes, and determine the uplink and downlink subframe ratio of the wireless frame; Step S2, calculating the DwPTS length in the special subframe of the wireless frame; Step S3, calculating the switch point position from downlink to uplink in the wireless frame, including the initial switch point position and the general switch point position, and completing the downlink to uplink switch point position on the initial switch point position and the general switch point position Link switching; where, The formula for calculating the position of the initial switch point from the downlink to the uplink is: ${\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}}_{\mathrm{<span\; class="notranslate">\; D.</span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; u</span>}}^{\mathrm{<span\; class="notranslate">\; I</span>}\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; t</span>}\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; =</span>{\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; D.</span>}\mathrm{<span\; class="notranslate">\; w</span>}\mathrm{<span\; class="notranslate">\; P</span>}\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$ In the formula, Indicates the downlink to uplink initial switching point position, Represents the symbol timing position obtained through primary synchronization detection, N represents the length of an OFDM symbol, N _CP represents the length of the CP, and n _DwPTS represents the number of DwPTS symbols in the special subframe; The formula for calculating the position of the general switching point from the downlink to the uplink is: ${\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}}_{\mathrm{<span\; class="notranslate">\; D.</span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; u</span>}}<span\; class="notranslate">\; =</span>{\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}}_{\mathrm{<span\; class="notranslate">\; u</span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; D.</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 30720</span>}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; D.</span>}\mathrm{<span\; class="notranslate">\; w</span>}\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; u</span>}\mathrm{<span\; class="notranslate">\; b</span>}\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; D.</span>}\mathrm{<span\; class="notranslate">\; w</span>}\mathrm{<span\; class="notranslate">\; P</span>}\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$ In the formula, Indicates the downlink to uplink general switching point location; Indicates the previous uplink-to-downlink switch point position of the current downlink-to-uplink general switch point; n _DwSubFr indicates the downlink subframe between the special subframe and the previous uplink subframe in the radio frame number of frames; S4. According to the initial downlink-to-uplink switching point position and general switching point position obtained in step S3, calculate the uplink-downlink switching point position in the wireless frame, and Complete the switching from the uplink to the downlink at the switching point position of the link; the calculation formula of the switching point position from the uplink to the downlink is: ${\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}}_{\mathrm{<span\; class="notranslate">\; D.</span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; u</span>}}^{\mathrm{<span\; class="notranslate">\; I</span>}\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; t</span>}\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; =</span>{\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}}_{\mathrm{<span\; class="notranslate">\; D.</span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; u</span>}}^{\mathrm{<span\; class="notranslate">\; I</span>}\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; t</span>}\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 30720</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; u</span>}\mathrm{<span\; class="notranslate">\; p</span>}\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; u</span>}\mathrm{<span\; class="notranslate">\; b</span>}\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; \&lsqb;</span>\mathrm{<span\; class="notranslate">\; 30720</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; D.</span>}\mathrm{<span\; class="notranslate">\; w</span>}\mathrm{<span\; class="notranslate">\; P</span>}\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&rsqb;</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$ ${\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}}_{\mathrm{<span\; class="notranslate">\; u</span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; D.</span>}}<span\; class="notranslate">\; =</span>{\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; t</span>}}}_{\mathrm{<span\; class="notranslate">\; D.</span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; u</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 30720</span>}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; u</span>}\mathrm{<span\; class="notranslate">\; p</span>}\mathrm{<span\; class="notranslate">\; S</span>}\mathrm{<span\; class="notranslate">\; u</span>}\mathrm{<span\; class="notranslate">\; b</span>}\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; \&lsqb;</span>\mathrm{<span\; class="notranslate">\; 30720</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; D.</span>}\mathrm{<span\; class="notranslate">\; w</span>}\mathrm{<span\; class="notranslate">\; P</span>}\mathrm{<span\; class="notranslate">\; T</span>}\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&rsqb;</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$ In the formula, Indicates the initial switch point position from uplink to downlink, Indicates the general switching point position from uplink to downlink; _nUpSubFr indicates the number of uplink subframes between a special subframe and a downlink subframe after the special subframe in the radio frame. 2. the uplink and downlink switching method of a kind of TD-LTE system according to claim 1, it is characterized in that, the DwPTS length in the special subframe that calculates described radio frame comprises the following steps in the described step S2: Step S2-1, in the special subframe, perform power value statistics in units of OFDM symbols, and preliminarily determine the length of the DwPTS; Step S2-2, perform OFDM symbol CP detection at the boundary of the preliminary judgment result obtained in step S2-1, and further accurately determine the length of the DwPTS; Step S2-3, accumulating the detection results of M times of OFDM symbol CP detection, if the DwPTS length in the special subframe is the same in the N detection results, it is determined that the DwPTS length in the special subframe is obtained successfully; otherwise, return to step S2-1 ; M is the number of detections of the preset OFDM symbol CP detection.