CN114630438B - A Prach detection method in NR5G - Google Patents
A Prach detection method in NR5G Download PDFInfo
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- CN114630438B CN114630438B CN202210382106.7A CN202210382106A CN114630438B CN 114630438 B CN114630438 B CN 114630438B CN 202210382106 A CN202210382106 A CN 202210382106A CN 114630438 B CN114630438 B CN 114630438B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/20—Control channels or signalling for resource management
- H04W72/21—Control channels or signalling for resource management in the uplink direction of a wireless link, i.e. towards the network
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/04—Wireless resource allocation
- H04W72/044—Wireless resource allocation based on the type of the allocated resource
- H04W72/0446—Resources in time domain, e.g. slots or frames
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/04—Wireless resource allocation
- H04W72/044—Wireless resource allocation based on the type of the allocated resource
- H04W72/0453—Resources in frequency domain, e.g. a carrier in FDMA
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Abstract
本发明公开了一种NR5G中的Prach检测方法，涉及通信技术领域，包括：根据基站本地生成根序列以及Prach的频域数据通过共轭相乘计算得到频域乘积；将所述频域乘积经过IFFT，得到时域相关值；基于时域相关值计算得到天线平均功率；设定判定阈值，根据天线平均功率和判定阈值筛选有效天线；将有效天线合并，得到合并的功率延时谱；根据功率延时谱计算得到检测门限；基于检测门限进行Preamble检测判决。本发明对天线平均功率进行了计算，基于天线平均功率和判定阈值可筛选有效天线，筛除了无效天线，仅将有效天线合并，并进行Prach检测，减小了随机接入虚检概率。
The present invention discloses a Prach detection method in NR5G, which relates to the field of communication technology, including: obtaining a frequency domain product by conjugate multiplication based on the frequency domain data of the root sequence generated locally by the base station and Prach; obtaining a time domain correlation value by passing the frequency domain product through IFFT; obtaining the antenna average power based on the time domain correlation value; setting a judgment threshold, screening effective antennas according to the antenna average power and the judgment threshold; merging effective antennas to obtain a combined power delay spectrum; calculating a detection threshold based on the power delay spectrum; and performing Preamble detection judgment based on the detection threshold. The present invention calculates the antenna average power, and can screen effective antennas based on the antenna average power and the judgment threshold, screen out invalid antennas, only merge effective antennas, and perform Prach detection, thereby reducing the probability of false detection of random access.
Description
Technical Field
The invention relates to the technical field of communication, in particular to a Prach detection method in NR 5G.
Background
In NR-5G, the UE performs downlink synchronization by receiving SSB issued by the base station, then obtains Prach time-frequency resource information through SIB1 information, and sends random access, where the base station extracts Prach time-frequency resources on slot (Prach Occasion slot) possibly sent by Prach, then performs Prach demodulation, and if the Preamble is resolved, it indicates that msg1 of the UE is received, and then issues RAR (Random Access Response) through msg 2.
For Prach demodulation, the base station, as a receiver, generates locally a set of base sequences, and the Prach sequence sent by the UE can be expressed as (3 gpp protocol 38.211, 6.3.3.1):
xu,v(n)＝xu((n+Cv)modLRA)
Where u represents the root sequence number, L RA is Prach sequence length (long format sequence is 839, short format is 139), C v is cyclic shift value, e represents exponent exp, n takes on the value range of 0 to L RA -1;
Wherein n is in the range of 0 to L RA -1, and m is in the range of 0 to L RA -1;
Prach sequences are generated from root sequences (root sequences), where the root sequences are
Where u represents the root sequence number, L RA is Prach in sequence length (839 in long format and 139 in short format), and i ranges from 0 to L RA -1;
wherein, the UE and the base station both know the information of C v, the root sequence number u, the Prach length L RA and the like. Because Prach sequences have strong autocorrelation characteristics, the base station performs frequency domain conjugate multiplication operation on the root sequences and the extracted data on Prach slot, converts the root sequences into time domains through IFFT to obtain time domain correlation values, finds out time domain correlation peaks, judges whether Prach signals of UE exist currently or not through a judgment threshold, and judges preamble Id. Wherein the decision threshold is related to the format (Fomat) of Prach, the number of Prach sequence repetitions and the number of antennas of the base station receiver. The current frequency domain processing procedure of detecting the Preamble by the base station is shown in fig. 1, when the number of receiving antennas of the base station is greater than 1, the detection of Prach adopts an antenna combination mode, and the threshold value of the detection threshold is different under the condition of different receiving antennas due to the relation between the threshold value of the detection threshold and the number of antennas. If no UE transmits Prach signals at this time, the noise power of the receiving antenna is inconsistent due to external interference or internal interference of the RRU, and the power difference between the antennas is large, at this time, if the antenna combining detection is performed, there is a possibility of Prach false detection.
The patent of Huai corporation, publication number CN111328088A, provides a PRACH detection method, which comprises the steps of sequentially detecting frequency domain data of each beam in at least two groups of beams, acquiring the frequency domain data of PRACH corresponding frequency from the frequency domain data of the current detection beam, determining a time domain correlation peak of the PRACH according to the frequency domain data of the PRACH corresponding frequency, determining a first peak value according to the time domain correlation peak of the PRACH, wherein the first peak value is the highest peak value in the time domain correlation peak of the PRACH, sending a random access response message to user equipment when the first peak value is greater than or equal to a first threshold value, using the random access response message for establishing connection between the user equipment and a base station, wherein the detection method is that when the first peak value of each beam in at least two groups of beams is smaller than the first threshold value, and the first peak value of at least two beams in at least two groups of beams is greater than or equal to a second threshold value, performing incoherent combination on the time domain correlation peaks of at least two beams in which the first peak value is greater than or equal to the second threshold value, determining a second peak value according to the incoherent combined time domain correlation peak value, and sending the second peak value to the highest peak value in the incoherent combination time domain correlation peak value to the incoherent combination, and sending the highest peak value to the incoherent peak value to the time domain correlation peak to the incoherent combination to the user equipment, and the random access response message to the user equipment when the first peak value is greater than or equal to the first peak value is greater than the first peak value and than the first peak value. The method is a detection mode for detecting the Preamble, but the relation between the threshold and the beam is not described, and the first threshold and the second threshold are fixed values or updated values calculated by the beam. If only noise exists at this time, and the interference of each beam is large, false detection may be caused.
Patent publication number CN109842945A of large tang mobile communication device, ltd, describes a method for accomplishing Prach detection using FPGA. The method aims to detect the time division multiplexing of resources by using the FPGA, can use a high Ncs (Number of CYCLIC SHIFT) value under a low-density wide coverage scene, increase the time delay redundancy of detection, improve the success rate of detection, can use a low Ncs value under a hot spot high-capacity small coverage scene, shorten the detection duration of the PRACH preamble sequence, increase the Number of random access users, can effectively reduce the consumption of the FPGA resources in the PRACH preamble sequence detection, effectively ensure the capacity of the random access users and the detection success rate, but can bring Prach virtual detection problem under the condition that the interference among antennas is not considered to be different.
Disclosure of Invention
The invention provides a Prach detection method in NR5G, which can reduce the probability of false detection of PRACH detection by a base station.
In order to solve the problems, the technical scheme adopted by the invention is as follows:
the invention provides a Prach detection method in NR5G, which comprises the following steps:
s1, calculating a frequency domain product according to a base station local generation root sequence and PRACH frequency domain data;
s2, performing IFFT on the frequency domain product to obtain a time domain correlation value;
s3, calculating to obtain the average power of the antenna based on the time domain correlation value;
S4, setting a judging threshold value, and screening effective antennas according to the average power of the antennas and the judging threshold value;
s5, combining the effective antennas to obtain a combined power delay spectrum;
S6, calculating according to the power delay spectrum to obtain a detection threshold;
S7, performing Preamble detection judgment based on the detection threshold.
The technical scheme has the technical effects that the average power of the antenna is calculated, the effective antenna can be screened based on the average power of the antenna and the judging threshold value, the ineffective antenna is screened out, only the effective antennas are combined, prach detection is carried out, and the random access false detection probability is reduced.
In a preferred embodiment of the present invention, in step S1, after receiving PRACH time domain data, a base station receiving antenna performs CP removal, FFT removal and demapping on the PRACH time domain data according to a higher layer resource configuration, and extracts the PRACH frequency domain data therefrom.
The technical scheme has the technical effects that Prach frequency domain data are extracted from Prach time domain data, the Prach frequency domain data volume is greatly less than Prach time domain data volume, and demodulation of Preamble Id is facilitated.
In a preferred embodiment of the present invention, in step S3, the calculation formula of the average power of the antenna is as follows:
Wherein, P u (r) is the antenna average power, r is the antenna index, c u (n, r) is the time domain correlation value, where r is the antenna index, n is the index of the time domain correlation value, and Nifft is the number of points of the IFFT.
The technical scheme has the technical effects that the time domain correlation is completed by the IFFT, and the complexity of correlation operation is simplified.
In a preferred embodiment of the present invention, in step S4, the method for screening effective antennas specifically includes:
Finding the maximum antenna average power in the antenna average power;
and calculating the difference value between the maximum antenna average power and the average powers of other antennas, and judging the corresponding antenna with the difference value smaller than the judging threshold value as the effective antenna.
The technical scheme has the technical effects that effective antennas can be rapidly screened to carry out subsequent antenna combination, and the false detection probability of Prach is reduced.
In a preferred embodiment of the present invention, the decision threshold is 6dB.
According to the technical effect of the technical scheme, according to the relation between the Thr threshold factor and the number of the antennas, if the power between the antennas is larger than 6dB, prach false detection probability is larger than 0 through simulation, so that the judgment threshold can well meet the condition of reducing false detection.
In a preferred embodiment of the present invention, in step S5, the power delay spectrum is calculated as follows:
Wherein P 0,u (n) is the power delay spectrum, nant is the number of effective antennas.
The technical scheme has the technical effects that the antenna with abnormal power is removed, the power time delay spectrum is obtained by only using the antennas with similar power, and the false detection rate of Prach is reduced.
In order to make the above objects, features and advantages of the present invention more comprehensible, embodiments accompanied with figures are described in detail below.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a prior art Prach detection flow chart;
FIG. 2 is a Prach detection flow chart of the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the invention, as presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. 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.
Examples
Referring to fig. 2, the embodiment provides a Prach detection method in NR5G, which is specifically as follows:
1) A time domain correlation value is calculated.
From the fourier transform, the time domain correlation can be obtained by multiplying the frequency domain, and the time domain correlation result is obtained by transforming the product result from the frequency domain to the time domain.
So, carrying out conjugate multiplication operation on PRACH frequency domain data of each antenna and a base station local generation root sequence to obtain a frequency domain product C u (k, r);
Cu(k,r)＝conj(Y(k,r))·Xu(k)
Wherein conj () represents taking conjugate, and the PRACH frequency domain data is marked as Y (k, r), which is obtained by extracting PRACH time domain data after performing CP removal, FFT and demapping according to high-layer resource configuration, wherein the PRACH time domain data is signal data received by a base station receiving antenna.
The base station locally generated root sequence, denoted X u (k), is generated locally according to a higher layer resource configuration for detecting the Preamble Id, where k=0..lra-1, where Lra is the length of the sequence, 839 for format 0. r is an antenna index, which takes on the value 0.. AntLen-1, antlen, which may be 1 or 2 or 4 or 8, depending on the antenna configuration of the base station.
Then, the result of the frequency domain product C u (k, r) is subjected to IFFT to obtain a time domain correlation value C u (n, r);
cu(n,r)＝IFFT(Cu(k,r))·sqrt(Nifft)
Where N ifft is the number of points of the IFFT, if the value is greater than Lra, then zero padding is only needed before transformation. r is the antenna index, and then the effective antenna is selected again for antenna data combination. Sqrt () represents an open root operation.
2) The antenna average power P u (r) is obtained by averaging the squares of the time domain correlation values for each antenna.
3) Find the maximum antenna average power at P u (r) and record as P max, and record the antenna index r0, then calculate the difference between the maximum antenna average power and other antenna average powers:
Pdiff(r)＝Pmax-Pu(r)
If the difference P diff (r) is smaller than or equal to the decision threshold, the antenna corresponding to the antenna average power P u (r) is an effective available antenna, that is, the antenna combination detection PRACH can be used, the antenna index is recorded, the number of the finally selected antennas is counted, if 1 antenna is effective, the effective antenna number is set to 1, if 2 antennas or 3 antennas are effective, the effective antenna number is set to 2, and if 4 antennas or effective, the effective antenna number is set to 4. If the difference P diff (r) is greater than the decision threshold, the combining qualification of the antennas corresponding to the antenna average power P u (r) is removed.
4) Calculating a combined power delay spectrum:
wherein Nant is the number of effective antennas, and r is taken here to exclude the unusable antennas.
5) The detection threshold is calculated as a total of two thresholds, thr u,A and Thr u,B, respectively.
First, calculating:
Thru,A＝Thr·Pu,avg
Wherein, thr is used as a threshold factor, which can be obtained by chi-square distribution calculation, and the value is obtained by combining the number of antennas and the Repeat number of PRACH, and can be read by pre-calculating and storing in the exterior and the interior, and the Thr factor is as follows:
Threshold Table for Different Formats
Then calculate Preamble PowerP u,signal on the basis of the threshold Thr u,A;
Wherein N u,s is the number of P 0,u (N) which is larger than Thr u,A.
6) Thr u,B＝Pu,signal, if P 0,u(n)＞Thru,B, detects a Preamble in the detection window.
From the threshold factor values in the above table, it can be found that, assuming Prach is configured as Format0, the threshold factor for the receiver 1 antenna is 17.5320, the threshold factor for the receiver 2 antenna is 11.7240, and the threshold factor for the receiver 4 antenna is 8.5440. Assuming that the current receiving end of the base station is 2 antennas, but the noise power received by each antenna is inconsistent (interference exists outside the rru radio frequency unit), if the selection of the antennas is not performed, the threshold factor is selected to be the corresponding 2-antenna threshold factor 11.7240, the value of the first threshold Thr u,A is reduced, and false detection is caused.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
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| CN102869027A (en) * | 2012-09-12 | 2013-01-09 | 大唐移动通信设备有限公司 | Method and device for detecting physical random access channel (PRACH) of multi-antenna base station |
| CN111328088A (en) * | 2018-12-17 | 2020-06-23 | 华为技术有限公司 | PRACH detection method and device |
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| CN102869027A (en) * | 2012-09-12 | 2013-01-09 | 大唐移动通信设备有限公司 | Method and device for detecting physical random access channel (PRACH) of multi-antenna base station |
| CN111328088A (en) * | 2018-12-17 | 2020-06-23 | 华为技术有限公司 | PRACH detection method and device |
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