CN102158933B - Method and device for frequency band search in TDD-LTE system - Google Patents

Abstract

The invention discloses a method for frequency band search in a TDD-LTE system and a frequency band search device for a terminal/subscriber unit in the TDD-LTE system. The method includes: a signal acquisition step: acquiring base station-specific signals on a search frequency band; a strength estimation step: estimating the strength of each base station-specific signal; a comparison step: comparing the strength of the base station-specific signal with a predetermined first A threshold is compared; the frequency band determination step: when the strength is greater than the predetermined first threshold, select the frequency band where the base station-specific signal with the strength greater than the predetermined first threshold is located as the frequency band to be accessed; the frequency band switching step: when When the strength is less than the predetermined first threshold, the search frequency band is switched, and the above steps are re-executed for the switched frequency band.

Description

Method and device for frequency band search in TDD-LTE system

technical field

The present invention generally relates to wireless communication systems, and more particularly, to a method and apparatus for frequency band search in a TDD-LTE (Time Division Duplex-Long Term Evolution) system.

Background technique

With the rapid development of mobile communication technology, the wireless communication system presents a trend of mobility, broadband and IP, and the competition in the mobile communication market is becoming increasingly fierce. In order to meet the challenges from traditional and emerging wireless broadband access technologies such as WiMAX and Wi-Fi, and to improve the competitiveness of the third-generation mobile communication system (3G) in the broadband wireless access market, 3GPP launched the Universal Mobile Telecommunications System (UMTS) terrestrial Research on long-term evolution (LTE) technology for radio access (UTRA) to realize the smooth transition from 3G technology to super three-generation mobile communication system (B3G) and fourth-generation mobile communication system 4G. The improvement goals of LTE are to achieve higher data rate, shorter delay, lower cost, higher system capacity and improved coverage.

The LTE system defines two modes of frequency division duplex (FDD) and time division duplex (TDD) at the same time. The 3GPP RAN1 meeting unified the two frame structures of LTE TDD. The integration of TDD frame structure makes LTE TDD technology receive extensive attention.

In a wireless communication system, a user equipment UE needs to perform frequency band search when it is turned on, so as to find a suitable cell or frequency band for access, so that downlink data can be received by the cell or frequency band and reliably decoded. For the next generation wireless communication system, such as the LTE system, since there are multiple working frequency bands, how to correctly find a suitable frequency band for access is a key issue.

Contents of the invention

A brief overview of the invention is given below in order to provide a basic understanding of some aspects of the invention. It should be understood that this summary is not an exhaustive overview of the invention. It is not intended to identify key or critical parts of the invention nor to delineate the scope of the invention. Its purpose is merely to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later.

According to one aspect of the present invention, there is provided a method for frequency band search in a TDD-LTE system, comprising: signal acquisition step: acquiring base station-specific signals on the search frequency band; strength estimation step: estimating each base station-specific signal The strength of the signal; the comparison step: comparing the strength of the base station-specific signal with a predetermined first threshold; the frequency band determination step: when the strength is greater than the predetermined first threshold, select the strength greater than the predetermined first threshold The frequency band where the base station-specific signal is located is used as the frequency band to be accessed; frequency band switching step: when the strength is less than a predetermined first threshold, switch the search frequency band, and re-execute the above steps for the switched frequency band.

According to another aspect of the present invention, there is provided a frequency band search device for a terminal/subscriber unit in a TDD-LTE system, comprising: a signal obtaining device configured to obtain a base station-specific signal on a search frequency band; Strength estimating means configured to estimate the strength of each base station-specific signal; comparing means configured to compare the strength of the base station-specific signal with a predetermined first threshold; access band determining means , which is configured to select the frequency band where the base station-specific signal whose strength is greater than the predetermined first threshold is located as the frequency band to be accessed when the strength is greater than the predetermined first threshold; the frequency band switching device is configured to use When the strength is less than a predetermined first threshold, switch the search frequency band.

Through the solution according to the present invention, the interference caused by the near-far effect can be reliably eliminated when the user equipment searches for the frequency band to be accessed, thereby obtaining the best synchronization performance and link quality, and improving the communication quality.

These and other advantages of the present invention will be more apparent through the following detailed description of the preferred embodiments of the present invention with reference to the accompanying drawings.

Description of drawings

The present invention can be better understood by referring to the following description given in conjunction with the accompanying drawings, wherein the same or similar reference numerals are used throughout to designate the same or similar parts. The accompanying drawings, together with the following detailed description, are incorporated in and form a part of this specification, and serve to further illustrate preferred embodiments of the invention and explain the principles and advantages of the invention. In the attached picture:

Figure 1 shows a typical scene with near-remote effect.

Fig. 2 shows a schematic diagram of power measurement in the prior art.

Fig. 3 shows a flowchart of a method for frequency band search according to an embodiment of the present invention.

Fig. 4 shows a schematic diagram of cell planning for primary synchronization signals with different values of i.

Fig. 5 shows a flowchart of a method for frequency band search according to another embodiment of the present invention.

Fig. 6 shows a schematic structural diagram of a frequency band search device according to an embodiment of the present invention.

Fig. 7 shows a schematic structural diagram of a frequency band search device according to another embodiment of the present invention.

Detailed ways

Exemplary embodiments of the present invention will be described below with reference to the accompanying drawings. In the interest of clarity and conciseness, not all features of an actual implementation are described in this specification. It should be understood, however, that in developing any such practical embodiment, many implementation-specific decisions must be made in order to achieve the developer's specific goals, such as meeting those constraints related to the system and business, and those Restrictions may vary from implementation to implementation. Moreover, it should also be understood that development work, while potentially complex and time-consuming, would at least be a routine undertaking for those skilled in the art having the benefit of this disclosure.

Here, it should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only the device structure and/or processing steps closely related to the solution according to the present invention are shown in the drawings, and the Other details not relevant to the present invention are described.

The inventor noticed that in the TDD-LTE system, frequency band search is a relatively complicated problem, because there is a so-called near-far effect in the TDD-LTE system. Fig. 1 schematically shows a typical scenario that a user equipment may encounter when performing frequency band search in a TDD-LTE system.

A typical scene with near-remote effect is shown in FIG. 1 . From Figure 1, we can see three cells, Cell 1, Cell 2 and Cell 3, which work on different frequency bands Band 1, Band 2 and Band 3 respectively. The center frequencies of these three frequency bands are different from each other, as shown in the figure 2 as shown in the figure above. The base station of Cell 1 is closest to the user equipment UE1. Another user equipment UE2 exists in the nearby cell Cell2. A frequency band search method commonly used in the prior art is to measure the signal power received at UE1, and use the frequency band that sends out the maximum signal power as the frequency band to be accessed. However in the scenario shown in Figure 1 problems may result. Normally, since UE1 is closest to the base station of Cell 1, the received power of Band1 should also be the largest. However, due to the presence of UE2, as shown in the lower figure in Figure 2, UE1 will add the signal power from UE2 and the base station of Cell 2, and the total power will be greater than the signal power from the base station of Cell 1, so that UE1 will connect to the cell by mistake. Entering Band 2, UE1 cannot obtain the best synchronization performance and link quality, which affects the communication effect.

first embodiment

The inventor has noticed that in the prior art, an important reason for the UE to perform wrong access is interference noise, which may come from other user equipments or other noise sources. Since this interference noise is not distinguished from the signal sent by the base station in the prior art, the power of the interference noise is simply added to the power of the useful signal sent by the base station when the user equipment performs a frequency band search, which easily leads to Misjudgment of the frequency band to be accessed.

The inventor noticed that if the unique signal sent by the base station can be used when the user equipment searches for the frequency band, and the unique signal is different from the noise signal, the influence of the noise can be eliminated when judging the frequency band to be accessed.

Therefore, according to an embodiment of the present invention, a method for frequency band search is proposed. Fig. 3 shows a flowchart of the method.

As shown in Figure 3, the method includes:

S310: Obtain a base station-specific signal on a search frequency band;

S330: Estimate the strength of each base station-specific signal;

S350: Comparing the strength of the base station-specific signal with a predetermined first threshold;

S370: When the intensity is greater than the predetermined first threshold, select the frequency band where the base station-specific signal with the intensity greater than the predetermined first threshold is located as the frequency band to be accessed.

S390: When the strength is less than the predetermined first threshold, change the search frequency band, and re-execute step S310 for the changed frequency band.

Since a base station-specific signal is used in the above method, and interference noise does not have such a signal, judging the frequency band to be accessed based on the signal strength eliminates the influence of interference noise, and more accurate access can be achieved. Improve system performance.

The applicant further researched and found that in the TDD-LTE system, the downlink signal sent by the base station always includes signals specific to the base station, such as PSS (Primary Synchronization) signal and SSS (Secondary Synchronization) signal. The following uses the PSS signal as an example for description. It should be pointed out that the following content is also applicable to the SSS signal.

The following briefly introduces the PSS signal.

In the LTE system, there are three kinds of PSS signals, which are expressed as Zadoff-Chu sequences with different parameters in the frequency domain. The PSS signal can be represented by the following formula:

$\mathrm{<span\; class="notranslate">\; PSS</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\left\{\begin{array}{cc}{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j</span>}\frac{\mathrm{<span\; class="notranslate">\; \&pi;in</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; 63</span>}}}& \mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0,1</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">\; 30</span>}\\ {\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j</span>}\frac{\mathrm{<span\; class="notranslate">\; \&pi;i</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; 63</span>}}}& \mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 31,32</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">\; 61</span>}\end{array}\right.<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>$

The parameter i can take 25, 29 or 34.

The sequence (with a length of 62) will be mapped to 62 subcarriers near the center carrier in the frequency domain, and 5 zeros will be added on both sides, occupying 72 subcarriers in total. In the TDD system, after IFFT (inverse fast Fourier transform), the OFDM symbol including the PSS will be placed on the third OFDM symbol of subframe #1 and subframe #6. Since the duration of the subframe is 1 ms, the transmission period of the PSS is 5 ms.

For a more detailed description of the PSS and SSS signals, refer to the 3GPP standard TS36.211v8.7.0, which will not be further described here.

As schematically shown in FIG. 4 , in practical applications, PSS signals used by adjacent base stations may have different i values through cell planning. When the user equipment determines that the power of the PSS signal from the first base station is the largest, since the interference noise does not have a PSS signal, it can be more accurately determined that the frequency band of the first base station is a better candidate frequency band, and the frequency band of the interference noise is excluded. Influence.

The following assumes that the method shown in FIG. 3 adopts the PSS signal as the signal specific to the base station for specific description.

Before implementing the method shown in FIG. 3, a copy PSS(i,n) of the PSS signal has been stored in the user equipment, wherein for the LTE system i=0,1,2; n=0,1,2, ..., 127. In addition, an initial center frequency has been obtained in the user equipment, and the initial center frequency may be input from the outside, or may be a pre-set frequency.

In step S310, the user equipment acquires a sample signal from the base station, where the sample signal includes a PSS signal. Since in the TDD LTE standard there must be PSS signals corresponding to 128 sample points in each half frame (corresponding to 9600 sample points). Preferably, the length of the sample signal is not less than 9600+128 sample points. Particularly preferably, the length of the sample signal is 9600+128 sample points, so as to estimate the strength of the PSS signal included in the sample signal. In the following, the length of the sample signal is 9600+128 for description.

In step S330, the intensity of the PSS signal in each sample signal is estimated. The strength of the PSS signal in the sample signal can be estimated by using the correlation value in the time domain between the copy PSS(i,n) of the PSS signal stored in the user equipment and the sample signal.

Assuming that the sample signal is r, the correlation value C(i, m) between the sample signal and the PSS copy can be calculated by the following formula:

$\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{<span\; class="notranslate">\; |</span>\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; 127</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\mathrm{<span\; class="notranslate">\; r</span>}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span>}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; PSS</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Where C(i, m) represents the correlation value between 128 sample points and the PSS copy PSS(i, n) after the mth sample point in the sample signal, m=0, 1, 2,..., 9599, r(n+m) ^* represents the conjugate of the corresponding sample point in the sample signal. It should be understood that other correlation operations can be used to obtain the strength estimate (correlation value here) of the PSS signal.

Since each sample signal from different base stations must contain the PSS signal, the corresponding i and the determined starting point m can be found for each sample signal through (2), and the copy PSS corresponding to the value of i ( i, n) and m, the maximum correlation value C _max (i, m) can be obtained. Those skilled in the art can easily know that, when the maximum correlation value is obtained, the sample point where the m value is located is the starting point of the PSS signal in the sample signal. Therefore, in this way, the correlation value between the PSS signal in the sample signal and the copy of the PSS signal stored in the user equipment is obtained, and also the estimated value of the PSS signal strength in the corresponding sample signal is obtained.

In step S350, a maximum PSS signal strength estimate is determined, and the maximum PSS signal strength estimate is compared with a predetermined first threshold. If the maximum PSS signal strength value is greater than the first threshold, it means that the signal strength of the frequency band where the PSS signal with the largest estimated strength value is acceptable, so in step S370, the frequency band where the PSS signal with the largest estimated strength value is located is taken as the desired frequency band. Access frequency band. If the maximum PSS signal strength value is smaller than the first threshold, it means that the signal strength of the frequency band where the PSS signal with the largest strength value is located is too weak, so step S390 is executed.

In step S390, the frequency of the oscillator in the user equipment is switched, so that sample signals are acquired on another frequency band. Subsequently, step S310 is re-executed.

The inventor noticed that usually after performing the above method on all frequency bands by switching the oscillator frequency in the user equipment, the frequency band to be accessed by the user equipment can be determined by using an appropriate first threshold. However, in some extreme cases, the maximum PSS signal strength values determined by the user equipment on all frequency bands may be less than the first threshold, then preferably a second threshold can be set at this time, if the maximum PSS signal strength value is greater than the second threshold, Then directly use the frequency band where the maximum PSS signal strength value is located as the frequency band to be accessed, and if the maximum PSS signal strength value is less than the second threshold, prompt the user that there is no frequency band to access.

Through the method proposed by the above-mentioned embodiments of the present invention, advantageously only the signal from the base station is considered for frequency band access, and the influence of interference noise from other user equipments, for example, is avoided to a large extent.

second embodiment

The inventor noticed that although the correlation value can be directly used as the signal strength of the PSS signal to judge as in the second embodiment above, the judgment result may be affected because the received sample signal may contain an uplink interference signal.

According to an improved solution of the present invention, the normalized correlation value can be used to estimate the signal strength of the PSS signal.

，可以通过下式来得到：The normalized correlation value is denoted as

, can be obtained by the following formula:

$\stackrel{<span\; class="notranslate">\; ~</span>}{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

in: $N\left(m\right)=\underset{\mathrm{no}=0}{\overset{127}{\mathrm{\&Sigma;}}}{\left|r(\mathrm{no}+m)\right|}^2---\left(4\right)$

之后，类似于上面描述的方法那样同样可以设置相应的阈值并进行判断，对此不再进一步描述。Get normalized correlation values

Afterwards, similar to the method described above, corresponding thresholds can also be set and judged, which will not be further described.

By using the normalized correlation value to estimate the signal strength of the PSS signal, the influence of the uplink interference signal is advantageously overcome.

，确定这些强度估计中的最大强度估计Preferably, for these intensity estimates obtained

, to determine the maximum intensity estimate among these intensity estimates

$\stackrel{<span\; class="notranslate">\; ~</span>}{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; max</span>}}<span\; class="notranslate">\; \{</span>\stackrel{<span\; class="notranslate">\; ~</span>}{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \}</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

，计算使用最大强度估计

的对应主同步序列PSS(i₀)获得的强度估计

，m＝0，1，2，...，9599的峰均比M。For maximum intensity estimation

, calculated using the maximum intensity estimate

The intensity estimate obtained from the corresponding primary synchronization sequence PSS(i ₀ )

, m=0, 1, 2, ..., the peak-to-average ratio M of 9599.

For example, the peak-to-average ratio M may be the ratio of the maximum intensity estimate to the mean of other intensity estimates obtained using the same PSS sequence in the intensity estimate and the maximum intensity estimate. specifically,

$\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\frac{\stackrel{<span\; class="notranslate">\; ~</span>}{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}{\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 9600</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; \&NotEqual;</span>{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{\overset{\mathrm{<span\; class="notranslate">\; 9599</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\stackrel{<span\; class="notranslate">\; ~</span>}{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

Alternatively, the peak-to-average ratio M may be the ratio of the maximum intensity estimate to the mean of all intensity estimates obtained with the same PSS sequence. specifically,

$\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\frac{\stackrel{<span\; class="notranslate">\; ~</span>}{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}{\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 9600</span>}}\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; 9599</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\stackrel{<span\; class="notranslate">\; ~</span>}{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

It should be understood that the peak-to-average ratio M can be calculated according to other definitions.

After the peak-to-average ratio M is obtained, a corresponding threshold can also be set and judged similarly to the method described above, which will not be further described.

By using the peak-to-average ratio M to estimate the signal strength of the PSS signal, the influence of the uplink interference signal is advantageously overcome, and the accuracy of the frequency band search can be further improved.

third embodiment

In order to further improve the estimation accuracy of the PSS signal, preferably, the above method according to the present invention can be executed multiple times in each frequency band, and the frequency band to be accessed is determined according to the results of multiple executions.

Fig. 5 shows a flow chart of a method for searching a frequency band using a PSS signal according to an embodiment of the present invention.

As can be seen from FIG. 5 , the method further includes step S360 on the basis of the method shown in FIG. 3 : judging whether the number of acquisitions of all sample signals in the current search frequency band is greater than a predetermined third threshold, if less than The third threshold, execute step S310 again to obtain the sample signal _rk from the current search frequency band again, and if it is greater than the third threshold, execute step S370 to switch the search frequency band so as to perform detection on other frequency bands.

After performing the sample signal acquisition step on the same frequency band multiple times, the signal strength of the PSS signal can be estimated by:

1) In the case of directly using the correlation value to estimate the signal strength of the PSS signal, the correlation value can be calculated for the kth repetition:

${\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{<span\; class="notranslate">\; |</span>\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; 127</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span>}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; PSS</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

C _k (i, m) represents the correlation result between the i-th main synchronization sequence and the subsequence starting from the m-th sample in the k-th sample sequence, where * means conjugation, m=0, 1, 2, . . . , 9599.

作为相应的PSS信号PSS(i，n)的强度估计。应当理解，也可以利用其它相关运算来得到强度估计。For PSS(i, n), the maximum correlation value C _{k, max} (i, m) for each i value (i=0, 1, 2) can be calculated separately, and the average value after K repetitions

as the intensity estimate of the corresponding PSS signal PSS(i,n). It should be understood that other correlation operations may also be utilized to obtain intensity estimates.

，其中2) In the case of using the normalized correlation value to estimate the signal strength of the PSS signal, for each C _k (i, m), estimate the strength of the corresponding sample signal of C _k (i, m) according to the strength and N _k (m) normalizes the intensity estimate C _k (i,m) to obtain a normalized intensity estimate

,in

${\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; 127</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 9</span>}<span\; class="notranslate">\; )</span>$

${\stackrel{<span\; class="notranslate">\; ~</span>}{\mathrm{<span\; class="notranslate">\; C</span>}}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 10</span>}<span\; class="notranslate">\; )</span>$

and using the mean of the normalized intensity estimates

$\stackrel{<span\; class="notranslate">\; ~</span>}{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; K</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\stackrel{<span\; class="notranslate">\; ~</span>}{\mathrm{<span\; class="notranslate">\; C</span>}}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 11</span>}<span\; class="notranslate">\; )</span>$

to estimate the strength of the corresponding PSS signal.

，确定这些强度估计中的最大强度估计(这里为归一化的相关值)3) In the case of using the peak-to-average ratio to estimate the signal strength of the PSS signal, it can be estimated based on the strength obtained above

, to determine the largest intensity estimate among these intensity estimates (here the normalized correlation value)

$\stackrel{<span\; class="notranslate">\; ~</span>}{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; max</span>}}<span\; class="notranslate">\; \{</span>\stackrel{<span\; class="notranslate">\; ~</span>}{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \}</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 12</span>}<span\; class="notranslate">\; )</span>$

，计算使用最大强度估计的对应主同步序列PSS(i₀)获得的强度估计

，m＝0，1，2，...，9599的峰均比M。and for the maximum intensity estimate

, calculated using the maximum intensity estimate The intensity estimate obtained from the corresponding primary synchronization sequence PSS(i ₀ )

, m=0, 1, 2, ..., the peak-to-average ratio M of 9599.

For example, the peak-to-average ratio M may be the ratio of the maximum intensity estimate to the mean of other intensity estimates obtained using the same master synchronization sequence in the intensity estimate and the maximum intensity estimate. specifically,

$\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\frac{\stackrel{<span\; class="notranslate">\; ~</span>}{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}{\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 9600</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; \&NotEqual;</span>{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{\overset{\mathrm{<span\; class="notranslate">\; 5990</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\stackrel{<span\; class="notranslate">\; ~</span>}{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 13</span>}<span\; class="notranslate">\; )</span>$

For example, the peak-to-average ratio M may be the ratio of the maximum intensity estimate to the mean of all intensity estimates obtained with the same master synchronization sequence. specifically,

$\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\frac{\stackrel{<span\; class="notranslate">\; ~</span>}{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>}{\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 9600</span>}}\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; 9599</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\stackrel{<span\; class="notranslate">\; ~</span>}{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 14</span>}<span\; class="notranslate">\; )</span>$

It should be understood that the peak-to-average ratio M can be calculated according to other definitions.

Since the method of this embodiment is executed multiple times for each frequency band, and the frequency band to be accessed is determined according to the results of multiple executions, the influence of other Gaussian noises in the communication system is further eliminated, and the accuracy of judgment is improved.

It should be noted that, according to the foregoing first to third embodiments, those skilled in the art can easily apply the corresponding method to the SSS signal. Since the SSS signal has more types than the PSS signal, the computational overhead is greater, but the principle is exactly the same as the method described above, and will not be further described here.

Fourth embodiment

Therefore, according to an embodiment of the present invention, a frequency band search device for a terminal/subscriber unit in a TDD-LTE system is proposed. FIG. 6 shows a schematic structural diagram of the frequency band search device.

As shown in Figure 6, the frequency band search device 600 includes:

a signal obtaining means 610, which is configured to obtain a base station-specific signal on the search frequency band;

strength estimating means 630 configured to estimate the strength of each base station-specific signal;

comparing means 650 configured to compare the strength of the base station specific signal with a predetermined first threshold;

The access frequency band determining means 670 is configured to, when the strength is greater than the predetermined first threshold, select the frequency band where the base station-specific signal with strength greater than the predetermined first threshold is located as the frequency band to be accessed. as well as

Frequency band switching means 690 configured to change the search frequency band when the strength is less than a predetermined first threshold.

Because the frequency band search device 600 uses a signal specific to the base station, but the interference noise does not have such a signal, so judging the frequency band to be accessed according to the signal strength eliminates the influence of the interference noise, and more accurate access can be achieved. Improve system performance.

The applicant further researched and found that in the TDD-LTE system, the downlink signal sent by the base station always includes signals specific to the base station, such as PSS (Primary Synchronization) signal and SSS (Secondary Synchronization) signal. Therefore, the frequency band search apparatus 600 can use the PSS signal or the SSS signal as a base station-specific signal to perform frequency band search.

In the following, it is assumed that the PSS signal is used as a base station-specific signal in the frequency band search apparatus 600 for specific description.

Before the frequency band search apparatus 600 performs the frequency band search, a copy PSS(i, n) of the PSS signal has been stored in the user equipment, wherein for the LTE system, i=0,1,2; n=0,1,2,. . . , 127. In addition, an initial center frequency has been obtained in the user equipment, and the initial center frequency may be input from the outside, or may be a pre-set frequency.

First, the signal acquiring device 610 acquires a sample signal from a base station, where the sample signal includes a PSS signal. Since in the TDD LTE standard there must be PSS signals corresponding to 128 sample points in each half frame (corresponding to 9600 sample points). Preferably, the length of the sample signal is not less than 9600+128 sample points. Particularly preferably, the length of the sample signal is 9600+128 sample points, so as to estimate the strength of the PSS signal included in the sample signal. In the following, the length of the sample signal is 9600+128 for description.

Then the intensity estimating means 630 estimates the intensity of the PSS signal in each sample signal. The strength of the PSS signal in the sample signal can be estimated by using the correlation value in the time domain between the copy PSS(i,n) of the PSS signal stored in the user equipment and the sample signal.

Assuming that the sample signal is r, the correlation value C(i, m) between the sample signal and the PSS copy can be calculated by the following formula:

$\mathrm{<span\; class="notranslate">\; C</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{<span\; class="notranslate">\; |</span>\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; 127</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\mathrm{<span\; class="notranslate">\; r</span>}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span>}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; PSS</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Where C(i, m) represents the correlation value between 128 sample points and the PSS copy PSS(i, n) after the mth sample point in the sample signal, m=0, 1, 2,..., 9599, r(n+m) ^* represents the conjugate of the corresponding sample point in the sample signal. It should be understood that other correlation operations may be utilized to obtain a strength estimate of the PSS signal.

Since each sample signal from different base stations must contain the PSS signal, the corresponding i and the determined starting point m can be found for each sample signal through (2), and the copy PSS corresponding to the value of i ( i, n) and m, the maximum correlation value C _max (i, m) can be obtained. Those skilled in the art can easily know that, when the maximum correlation value is obtained, the sample point where the m value is located is the starting point of the PSS signal in the sample signal. Therefore, in this way, the correlation value between the PSS signal in the sample signal and the copy of the PSS signal stored in the user equipment is obtained, and the corresponding PSS signal strength value in the sample signal is also obtained.

The comparing means 650 then determines a maximum PSS signal strength estimate and compares the maximum PSS signal strength estimate with a predetermined first threshold. If the estimated maximum PSS signal strength value is greater than the first threshold, it means that the signal strength of the frequency band where the PSS signal with the largest estimated strength value is located is acceptable. frequency band as the frequency band to be accessed. If the maximum estimated PSS signal strength value is less than the first threshold, it indicates that the signal strength of the frequency band where the PSS signal with the largest estimated strength value is located is too weak. Therefore, the frequency band switching means 690 switches the frequency of the oscillator in the user equipment, so that in another Obtain sample signals on the frequency band. Subsequently, the band search process is re-executed.

The inventor noticed that usually after performing the above method on all frequency bands by switching the oscillator frequency in the user equipment, the frequency band to be accessed by the user equipment can be determined by using an appropriate first threshold. However, in some extreme cases, the maximum PSS signal strength values determined by the user equipment on all frequency bands may be less than the first threshold, then preferably a second threshold can be set at this time, if the maximum PSS signal strength value is greater than the second threshold, The frequency band where the maximum PSS signal strength value is located is directly used as the frequency band to be accessed, otherwise the user is prompted that there is no frequency band to be accessed.

With the frequency band search apparatus 600 proposed according to the above-mentioned embodiments of the present invention, advantageously only the signal from the base station is considered for frequency band access, and influences such as interference noise from other user equipments are avoided to a large extent.

The inventor noticed that although the correlation value can be directly used as the signal strength of the PSS signal for judgment, the judgment result may be affected because the received sample signal may contain an uplink interference signal.

Therefore, according to an improved solution of the present invention, the signal strength of the PSS signal can be estimated by using the normalized correlation value, and the signal strength of the PSS signal can also be estimated by using the peak-to-average ratio M. Regarding the use of the normalized correlation value and the peak-to-average ratio, please refer to the description in the method section for details, and will not be repeated here.

By using the peak-to-average ratio M to estimate the signal strength of the PSS signal, the influence of the uplink interference signal is advantageously overcome, and the accuracy of the frequency band search can be further improved.

fifth embodiment

In order to further improve the accuracy of the estimation of the PSS signal, preferably, the frequency band search device 600 according to the present invention can also include an acquisition times judgment device 660, which can make the frequency band search device 600 perform multiple frequency band search processes in each frequency band .

Fig. 7 shows a schematic structural diagram of an improved frequency band search device 700 according to an embodiment of the present invention.

As can be seen from FIG. 7 , on the basis of the structure shown in FIG. 6 , the frequency band search device 600 also includes an acquisition times judging unit 660 configured to judge whether the number of acquisition times of all sample signals in the current search frequency band is greater than a predetermined third threshold, if less than the third threshold, then control the signal acquisition means 610 to obtain the sample signal rk from the current search frequency band again, if greater than the third threshold, then control the frequency band switching means 690 to switch the search frequency band, so that in other detection in the frequency band.

After performing the band search process for the same frequency band multiple times, the frequency band to be accessed may be determined by using an average correlation value, an average normalized value, or a peak-to-average ratio. For this, reference may be made to the content in the method according to the third embodiment, which will not be repeated here.

Since the method of this embodiment is executed multiple times for each frequency band, and the frequency band to be accessed is determined according to the results of multiple executions, the influence of other Gaussian noises in the communication system is further eliminated, and the accuracy of judgment is improved.

It should be noted that, in the frequency band search apparatus 600 according to the present invention, SSS signals can also be used. Since the SSS signal has more types than the PSS signal, the computational overhead is larger, but the principle is exactly the same as the method described above, and will not be further described here.

It is not difficult to see from the above description that according to the embodiments of the present invention, the following solutions are provided:

Additional Note 1. A method for frequency band search in a TDD-LTE system, comprising:

A signal acquisition step: acquiring a base station-specific signal on a search frequency band;

Strength estimation step: estimating the strength of each base station-specific signal;

Comparing step: comparing the strength of the base station specific signal with a predetermined first threshold;

Frequency band determination step: when the strength is greater than a predetermined first threshold, select the frequency band where the base station-specific signal with strength greater than the predetermined first threshold is located as the frequency band to be accessed;

Frequency band switching step: when the strength is less than the predetermined first threshold, switch the search frequency band, and re-execute the above steps for the switched frequency band.

Addendum 2. The method according to addendum 1, wherein the base station specific signal is a primary synchronization signal or a secondary synchronization signal.

Supplement 3. The method according to Supplement 1 or 2, further comprising a step of judging the number of times of acquisition: judging whether the number of times of acquiring all base station-specific signals in the current search frequency band is greater than a predetermined third threshold, if less than the third threshold , then perform the signal acquisition step again, so as to obtain the sample signal from the current search frequency band again, and if it is greater than the third threshold, perform the frequency band switching step to switch the search frequency band.

Supplement 4. The method according to any one of the above supplements, wherein the correlation value in the time domain between the copy of the base station-specific signal stored in the user equipment and the acquired base station-specific signal is used to estimate The strength of the acquired base station specific signal.

Supplement 5. The method according to any one of the above supplements, wherein the strength of the obtained base station-specific signal is estimated by using a normalized correlation value, which is the The stored copy of the base station-specific signal is obtained after normalizing the correlation value in the time domain with the acquired base station-specific signal.

Additional note 6. The method according to any one of the above additional notes, wherein the peak-to-average ratio of normalized correlation values is used to estimate the strength of the acquired base station-specific signal.

Supplementary Note 7. A frequency band search device (600) for a terminal/subscriber unit in a TDD-LTE system, comprising:

signal acquiring means (610) configured to acquire a base station specific signal on a search frequency band;

strength estimating means (630) configured to estimate the strength of each base station specific signal;

comparing means (650) configured to compare the strength of the base station specific signal with a predetermined first threshold;

Access frequency band determining means (670), which is configured to select, as the frequency band to be accessed, the frequency band in which the base station-specific signal whose strength is greater than the predetermined first threshold is located when the strength is greater than the predetermined first threshold;

Frequency band switching means (690), configured to switch the search frequency band when the strength is less than a predetermined first threshold.

Supplement 8. The frequency band search device (600) according to Supplement 7, wherein the base station specific signal is a primary synchronization signal or a secondary synchronization signal.

Supplementary Note 9. The frequency band search device (600) according to Supplementary Note 7 or 8, further comprising acquisition times judging means (660), which is configured to judge whether the number of times of acquiring all base station-specific signals in the current search frequency band is greater than a predetermined third threshold, if less than the third threshold, execute the signal acquisition step again, so as to obtain sample signals from the current search frequency band again, and control the frequency band switching device to switch the search frequency band if greater than the third threshold.

Supplement 10. The frequency band search device (600) according to any one of Supplements 7 to 9, wherein the strength estimation device (630) uses the copy of the base station-specific signal stored in the user equipment and the acquired specific The strength of the acquired base station-specific signal is estimated based on the correlation value of the base station-specific signal in the time domain.

Supplementary Note 11. The frequency band search device (600) according to any one of Supplementary Notes 7 to 9, wherein the strength estimation device (630) uses a normalized correlation value to estimate the strength of the acquired base station-specific signal , the normalized correlation value is obtained after normalizing a copy of the base station-specific signal stored in the user equipment and the obtained correlation value of the base station-specific signal in the time domain.

Supplement 12 The frequency band search device (600) according to any one of Supplements 7 to 9, wherein the strength estimation device (630) uses the peak-to-average ratio of the normalized correlation value to estimate the obtained base-station-specific The strength of the signal.

Claims (8)

1. A method for frequency band search in a TDD-LTE system, comprising: Signal acquisition step: acquiring a base station-specific signal on the search frequency band; Strength estimation step: estimate the strength of each base station-specific signal; Comparing step: comparing the strength of the base station-specific signal with a predetermined first threshold; Frequency band determination step: when the strength is greater than the predetermined first threshold, select the frequency band where the base station-specific signal with the strength greater than the predetermined first threshold is located as the frequency band to be accessed; Frequency band switching step: when the strength is less than the predetermined first threshold, switch the search frequency band, and re-execute the above steps for the switched frequency band, wherein the strength of the acquired base-station-specific signal is estimated using a normalized correlation value that combines a copy of the base-station-specific signal stored in the user equipment with the acquired base-station-specific signal obtained after normalizing the correlation values in the time domain. the 2. The method of claim 1, wherein the base station specific signal is a primary synchronization signal or a secondary synchronization signal. the 3. The method according to claim 1 or 2, further comprising a step of judging the number of times of acquisition: judging whether the number of times of acquiring all base station-specific signals in the current search frequency band is greater than a predetermined third threshold, if less than the third threshold, then Executing the signal acquiring step again, so as to obtain the sample signal from the current search frequency band again, and performing the frequency band switching step to switch the search frequency band if it is greater than the third threshold. the 4. The method according to claim 1 or 2, wherein the peak-to-average ratio of the normalized correlation values is used to estimate the strength of the acquired base station-specific signal. the 5. A frequency band search device (600) for a terminal/subscriber unit in a TDD-LTE system, comprising: signal acquisition means (610), which is configured to acquire a base station-specific signal on the search frequency band; strength estimating means (630), which is configured to estimate the strength of each base station-specific signal; Comparing means (650) configured to compare the strength of the base station specific signal with a predetermined first threshold; Access frequency band determining means (670), which is configured to select, as the frequency band to be accessed, the frequency band in which the base station-specific signal whose strength is greater than the predetermined first threshold is located when the strength is greater than the predetermined first threshold; frequency band switching means (690), which is configured to switch the search frequency band when the strength is less than a predetermined first threshold, Wherein the strength estimating means (630) estimates the strength of the acquired base station-specific signal using a normalized correlation value, which is a copy of the base station-specific signal stored in the user equipment and the acquired The base station-specific signals are obtained after normalizing the correlation values in the time domain. the 6. The frequency band search device (600) according to claim 5, wherein the base station specific signal is a primary synchronization signal or a secondary synchronization signal. the 7. The frequency band search device (600) according to claim 5 or 6, further comprising acquisition times judging means (660), which is configured to judge whether the number of times of acquiring all base station-specific signals in the current search frequency band is greater than a predetermined number of times If the determined third threshold is smaller than the third threshold, the signal acquisition step is performed again to obtain sample signals from the current search frequency band again, and if it is greater than the third threshold, the frequency band switching device is controlled to switch the search frequency band. the 8. The frequency band search device (600) according to claim 5 or 6, wherein the strength estimating device (630) uses the peak-to-average ratio of the normalized correlation values to estimate the strength of the acquired base station-specific signal. the

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