CN115955291B - Method and equipment for reducing NBIOT network cell search false detection probability - Google Patents
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Abstract
The invention discloses a method and equipment for reducing the false detection probability of NBIOT network cell search, and belongs to the field of wireless communication. Comprising the following steps: detecting a primary synchronization signal NPSS; performing coarse synchronization on NBIOT cell search detection, and determining coarse symbol synchronization points; performing fine synchronization on NBIOT cell search detection, and determining a fine symbol synchronization point; and detecting the secondary synchronization signal NSSS to obtain the current physical cell identifier. The method also comprises the step of judging the residual decimal frequency offset estimated in the fine synchronization process and the peak-to-average ratio of the relevant power estimated by the integer frequency offset in the fine synchronization process. The invention can reduce the false detection probability of the accurate synchronization to a certain extent.
Description
Technical Field
The invention relates to the field of wireless communication, in particular to a method and equipment for reducing the false detection probability of NBIOT network cell search.
Background
Cell search is a very critical procedure that enables a user equipment UE to establish synchronization with a base station for communication. The cell search typically includes a coarse synchronization stage for finding coarse synchronization positions in the subframes and a fine synchronization (fine stage) for finding fine synchronization positions at the chip level.
NPSS and NSSS are downlink synchronization obtained between UE and NB-IOT network, primary synchronization signal NPSS is transmitted based on specific subframes of 10ms repetition interval and secondary synchronization signal NSSS is transmitted in specific subframes of 20ms repetition interval. The UE can calculate a cell identifier (NB-IOT PCI) from the detected NPSS and NSSS.
However, in the process of fine synchronization of cell search, the existing NBIOT chip generally only makes threshold judgment of NPSS related peak power, and does not even make any threshold judgment. Under the condition of low signal to noise ratio, the fluctuation of the judgment quantity is greatly influenced by noise, so that the judgment result is unreliable, the accuracy of the accurate synchronization point is rapidly reduced, the false detection probability of NSSS detection is further increased, and even a product cannot be accessed. Meanwhile, in the process of fine synchronization, fractional frequency offset estimation and integer frequency offset estimation are generally carried out, and the robustness of the residual fractional frequency offset is not considered, so that the false detection probability is high.
Therefore, how to provide a method and apparatus for reducing the probability of cell search false detection of an NBIOT network is a problem that needs to be solved by those skilled in the art.
Disclosure of Invention
In view of the above, the present invention provides a method and apparatus for reducing the probability of false detection of cell search in an NBIOT network, which are used for solving the problems in the prior art.
In order to achieve the above object, the present invention provides the following technical solutions:
in one aspect, the invention provides a method for reducing the false detection probability of NBIOT network cell search, which comprises the following steps:
detecting a primary synchronization signal NPSS;
performing coarse synchronization on NBIOT cell search detection, and determining coarse symbol synchronization points;
performing fine synchronization on NBIOT cell search detection, and determining a fine symbol synchronization point;
and detecting the secondary synchronization signal NSSS to obtain the current physical cell identifier.
Preferably, the performing coarse synchronization on the NBIOT cell search detection, determining a coarse symbol synchronization point, includes:
performing NBIOT cell search related detection;
estimating the decimal frequency multiplication offset after coarse synchronization;
and judging whether the result of the rough synchronization can pass through a rough synchronization threshold judgment, if so, determining a rough symbol synchronization point, and if not, performing re-search if the cell search is false.
Preferably, the determining the fine symbol synchronization point by performing fine synchronization on the NBIOT cell search detection includes:
receiving a coarse symbol synchronization point from the coarse synchronization and a fractional frequency offset,
based on a coarse symbol synchronization point, compensating the fine synchronization by using a decimal frequency offset value, and carrying out threshold judgment on the residual decimal frequency offset estimated in the fine synchronization process;
and judging an integer frequency offset result, and compensating the precise frequency offset according to the judgment result.
Preferably, the determining of the integer multiple frequency offset result, compensating the precision frequency offset according to the determining result, includes:
presetting a candidate integer frequency multiplication offset set, and sequentially compensating the frequency offset value in the set to a received signal;
performing correlation calculation on the compensated signal and the local signal, and recording the obtained correlation power as follows:
the index of the true integer frequency offset in the candidate integer frequency offset set is set as
Then satisfy
；
The index corresponding to the frequency offset value farthest from the true integer frequency offset is set in the candidate integer frequency offset set
The corresponding correlation result is +.>
Then there is the following equation:
equivalent to orthogonalizing the received signal with the local signal:
wherein M is a vector
Length of->
；
For a pair of
Adding constraint conditions to the elements in the formula (I), and calculating to obtain the formula (I)>
；
Setting threshold
The synchronization point is accurate, otherwise, the cell search is false, and the next search is started.
Preferably, the pair of
Adding constraint conditions to the elements in the formula (I), and calculating to obtain the formula (I)>
Comprising:
wherein, will be
All elements in (a) are ordered from small to large and marked as +.>
。
In another aspect, the invention provides an electronic device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, the processor implementing a method of reducing a probability of false detection of cell search of an NBIOT network when executing the computer program.
Compared with the prior art, the invention discloses a method and equipment for reducing the false detection probability of the cell search of the NBIOT network, which are used for finding out a more robust calculated amount as a judgment standard by further calculating the related results of fractional frequency offset and integer frequency offset, and if the judgment is not passed, the secondary synchronization is considered to be invalid, NSSS detection is skipped, and the false detection probability of the fine synchronization is reduced to a certain extent.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only embodiments of the present invention, and that other drawings can be obtained according to the provided drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic flow chart of the method of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
On the one hand, referring to fig. 1, embodiment 1 of the present invention discloses a method for reducing the probability of false detection of cell search of an NBIOT network, which comprises the following steps:
detecting a primary synchronization signal NPSS;
processing the primary synchronization signal NPSS;
performing coarse synchronization on NBIOT cell search detection, and determining coarse symbol synchronization points;
performing fine synchronization on NBIOT cell search detection, and determining a fine symbol synchronization point;
and detecting the secondary synchronization signal NSSS to obtain the current physical cell identifier.
In a specific embodiment, performing coarse synchronization on NBIOT cell search detection, determining a coarse symbol synchronization point includes:
performing NBIOT cell search related detection;
estimating the decimal frequency multiplication offset after coarse synchronization;
and judging whether the result of the rough synchronization can pass through a rough synchronization threshold judgment, if so, determining a rough symbol synchronization point, and if not, performing re-search if the cell search is false.
In a specific embodiment, performing fine synchronization on NBIOT cell search detection, determining a fine symbol synchronization point includes:
receiving a coarse symbol synchronization point from coarse synchronization and a decimal frequency multiplication offset estimated after coarse synchronization;
based on a coarse symbol synchronization point, compensating the fine synchronization by using a decimal frequency offset value, and carrying out threshold judgment on the residual decimal frequency offset estimated in the fine synchronization process;
and carrying out judgment on the integer frequency offset result, compensating the precise frequency offset according to the judgment result, and determining a precise symbol synchronization point.
Specifically, in cell search of NBIOT, the key steps are that coarse synchronization is firstly performed, and coarse synchronization points under lower sampling rate (generally 240 KHz) are found; and then fine synchronization is carried out, so as to find a fine synchronization point at a higher sampling rate (1.92 MHz). The coarse synchronization and the fine synchronization are processed aiming at a main synchronization signal NPSS; and finally, detecting NSSS to obtain the cell PCI under the current precise synchronization point.
Specifically, NPSS and NSSS acquire downlink synchronization between UE and NB-IOT network, and primary synchronization signal NPSS is transmitted based on a specific subframe of 10ms repetition interval and secondary synchronization signal NSSS is transmitted in a specific subframe of 20ms repetition interval. The UE can calculate a cell identification number (NB-IOT PCI) from the detected NPSS and NSSS.
Specifically, in general, the fractional frequency offset is estimated in the course of coarse synchronization, then the received signal is compensated, the compensated signal is sent to a fine synchronization module, and the residual fractional frequency offset is estimated in the fine synchronization. The conventional algorithm directly compensates the residual fractional frequency offset estimated in the fine synchronization process to the received data without regard to the robustness of the residual fractional frequency offset.
In one embodiment, the residual fraction estimated during the fine synchronization is multiplied byBias threshold decision, residual decimal frequency bias is recorded as
The threshold is->
If (3)
The above is a decision algorithm for fractional frequency offset estimation in the fine synchronization process.
In a specific embodiment, the decision of the integer frequency offset result is performed, and the fine frequency offset is compensated according to the decision result, including:
the common practice of integer frequency offset estimation is to preset a suitable set of candidate integer frequency offsets, sequentially compensate the frequency offset value in the set to the received signal, then perform correlation calculation on the compensated signal and the local signal, and obtain the correlation power to be recorded as
Wherein, the method comprises the steps of, wherein,
Assuming that the index of the true integer multiple frequency offset in the candidate integer multiple frequency offset set is
Then generally satisfy
；
The index corresponding to the frequency offset value farthest from the true integer frequency offset is set in the candidate integer frequency offset set
The corresponding correlation result is +.>
Then there is the following equation:
since the received signal is compensated for an integer multiple of the frequency offset which is not identical to the actual frequency offset, this approach is approximately equivalent to orthogonalizing the received signal and the local signal, so there are
Wherein M is a vector
Is a length of (c).
Due to
Therefore, it can be considered as->
The reference can be used as a reliable decision condition.
In a particular embodiment, due to
Is a maximum and minimum part pair +.>
The mean value of (2) has a larger influence, so take +.>
Data after head and tail pinching to calculate mean value, i.e. +.>
All elements in the Chinese are ordered from small to large and then recorded as
，/>
By setting threshold
If->
If the synchronization point is accurate, otherwise, the cell search is false, and the next search is started.
In one particular embodiment, due to
Is a maximum and minimum part pair +.>
Mean>
Has a greater influence, so will->
All elements in (a) are ordered from small to large and marked as +.>
Then
Pinching the head and removing the tail to obtain the index +.>
Is calculated by the intermediate part value of +.>
。
In particular, the data of the head and tail is removed, the device can be designed by itself during the specific implementation,
but one of them.
On the other hand, embodiment 1 of the invention discloses an electronic device, which comprises a memory, a processor and a computer program stored on the memory and capable of running on the processor, wherein the processor realizes a method for reducing the false detection probability of NBIOT network cell search when executing the computer program
Specifically, if the synchronization timing is inaccurate or the signal-to-noise ratio is high, the estimated fractional frequency offset can be considered to be accurate, and after the fractional frequency offset compensation after the coarse synchronization, the estimated residual fractional frequency offset in the fine synchronization process is close to zero; if the synchronization timing is inaccurate or the signal-to-noise ratio is low, the estimated decimal frequency offset accuracy can be drastically reduced, and at the moment, a larger decimal frequency offset is remained in the fine synchronization data with high probability, and the subsequent NSSS detection is unreliable due to the fact that a larger decimal frequency offset is remained. Therefore, the invention finds a more robust calculated amount to be used as a judgment standard by further calculating the related results of the fractional frequency offset and the integer frequency offset, and considers that the sub-precision synchronization is invalid and skips NSSS detection if the judgment is not passed, thereby reducing the false detection probability of the precision synchronization to a certain extent.
Compared with the prior art, the invention discloses a method and equipment for reducing the false detection probability of NBIOT network cell search, which mainly reduces false detection by 2 decisions: 1. judging the estimated residual decimal frequency offset in the fine synchronization process; 2. and judging the peak-to-average ratio of the related power estimated by the integer frequency offset in the fine synchronization process. By the technical scheme, the false detection probability of the fine synchronization can be reduced to a certain extent.
Example 2
Based on the method for reducing the NBIOT network cell search false detection probability, the gain of the NBIoT chip of a certain manufacturer after adopting the algorithm is analyzed through testing:
test scenario: some outer field of Beijing locks on frequency point 3685, and there is a cell PCI466 under the frequency point, and the signal to noise ratio of the cell is approximately-6.5 db. Cell search was performed 100 times.
Probability of false detection (search to a cell other than PCI 466) before employing the present inventionAbout 85 percent after the adoption of the invention
) The false detection probability is approximately 40%.
Under the same test environment, a certain NBiot chip abroad is compared, and the false detection probability is about 35%.
The test can prove that the invention can indeed greatly reduce the false detection probability of cell search under low signal to noise ratio.
In the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant points refer to the description of the method section.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (4)
1. The method for reducing the false detection probability of the NBIOT network cell search is characterized by comprising the following steps:
detecting a primary synchronization signal NPSS;
performing coarse synchronization on NBIOT cell search detection, and determining coarse symbol synchronization points;
performing fine synchronization on NBIOT cell search detection, and determining a fine symbol synchronization point;
detecting a secondary synchronization signal NSSS to obtain a current physical cell identifier;
the performing fine synchronization on the NBIOT cell search detection to determine a fine symbol synchronization point includes:
receiving a coarse symbol synchronization point from coarse synchronization and a decimal frequency multiplication offset estimated after coarse synchronization;
based on a coarse symbol synchronization point, compensating the fine synchronization by using a decimal frequency offset value, and carrying out threshold judgment on the residual decimal frequency offset estimated in the fine synchronization process;
and carrying out judgment on the integer frequency offset result, and compensating the precise frequency offset according to the judgment result, wherein the judgment comprises the following steps:
presetting a candidate integer frequency multiplication offset set, and sequentially compensating the frequency offset value in the candidate integer frequency multiplication offset set to a received signal to obtain a compensated received signal;
calculating the compensation receiving signal and the local signal to obtain power which is recorded as:
P[c]＝[P 0 ，P 1 ，...，P c-1 ，]where c=0, 1..c-1, c is the size of the set of candidate integer frequency doubling offsets;
let the index of the true integer multiple frequency offset in the candidate integer multiple frequency offset set be c I Then max (Pc I ])＝max(P[c])>>0；
The index corresponding to the frequency offset value farthest from the true integer frequency offset is c 0 The corresponding result is Pc 0 ]Then there is the following equation:
max(P[c 0 ])＝min([max(P[0])，max(P[1])，...，max(P[C-1])])；
equivalent to orthogonalizing the received signal with the local signal:
wherein M is a vector Pc 0 ]Is a length of (2);
for Pc 0 ]Adding constraint conditions to the elements in the formula, and calculating to obtain
Set up doorLimited Threshold1, if
The precise symbol synchronization point is accurate, otherwise, the cell search is false, and the next search is started.
2. The method for reducing the probability of false detection of an NBIOT network cell search according to claim 1, wherein the performing coarse synchronization on the NBIOT cell search detection to determine a coarse symbol synchronization point comprises:
performing NBIOT cell search detection;
estimating the decimal frequency multiplication offset after coarse synchronization;
and judging whether the result of the rough synchronization can pass through a rough synchronization threshold judgment, if so, determining a rough symbol synchronization point, and if not, performing re-search if the cell search is false.
3. The method for reducing the probability of false detection of cell search in an NBIOT network of claim 1, wherein for P [ c ] 0 ]Adding constraint conditions to the elements in the formula, and calculating to obtain
Comprising the following steps: />
In the formula, pc 0 ]All elements in the sequence from small to large are marked as P 0 [n]，n＝0，1，...，2M，。
4. An electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the processor implements a method of reducing the probability of false detection of a cell search of an NBIOT network as claimed in any of claims 1 to 3 when the computer program is executed by the processor.
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| US10512048B2 (en) * | 2017-07-24 | 2019-12-17 | Ceva D.S.P Ltd. | System and method for radio cell synchronization |
| CN109428848B (en) * | 2017-08-29 | 2021-03-26 | 苏州优尼赛信息科技有限公司 | Method for detecting and estimating fine synchronization of downlink primary synchronization signal in NB-loT system |
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