A method for detecting a random access preamble sequence based on 5G NR

Abstract

The application provides a 5G NR-based random access preamble sequence detection method, and belongs to the technical field of preamble sequence detection, and comprises the following steps: extracting a PRACH frequency domain signal; eliminating the phase difference between subcarriers and the phase difference between symbols of the PRACH frequency domain signal; performing inverse compensation on a phase rotation factor of the PRACH frequency domain signal; eliminating the Doppler frequency shift and phase noise between symbols of the PRACH frequency domain signal; performing multi-symbol coherent combination of the PRACH receiving signal and a local root sequence, so as to ensure the multi-symbol combination gain of the PRACH signal; and performing preamble sequence detection by using peak value searching; the method has low implementation complexity, can improve the detection performance of the random access preamble sequence in high-frequency wireless communication, and reduces the missed detection rate.

Description

Technical Field

[0001] This invention belongs to the field of preamble sequence detection technology, specifically relating to a random access preamble sequence detection method based on 5G NR. Background Technology

[0002] The 3GPP specification supports three cyclic shift generation methods for generating the PRACH preamble sequence for the random access channel: unrestricted set, restricted set A, and restricted set B. Restricted set A and restricted set B are used to generate random access preamble sequences supporting high-speed mobile scenarios. In high-speed scenarios, Doppler shift causes energy drift in the correlation peak. Peak detection requires merging the main search window and the secondary search window. A schematic diagram of the correlation peak energy drift caused by Doppler shift is shown below. Figure 2 In the diagram, the first peak from the left is the primary peak, and the other two are secondary peaks. Constraint set A requires merging one secondary search window, while constraint set B requires merging two secondary search windows. Constraint set B supports higher movement speeds, up to 500 km / h. However, the peak search process for merging primary and secondary search windows has high implementation complexity.

[0003] Chinese patent application CN202011463845.6 discloses a random access detection method that reuses the uplink service channel reception time-domain processing, avoiding the need for additional time-domain processing of the access channel and reducing implementation complexity to some extent. However, this patent does not consider the Doppler frequency shift problem caused by high-speed movement. When the Doppler frequency shift is large, it can easily lead to false detections and missed detections, making it only applicable to non-high-speed movement scenarios. Furthermore, the detection method provided by this patent does not eliminate the phase difference introduced by different symbols during CP removal before symbol combining, resulting in the loss of some combining gain brought by multi-symbol data combining.

[0004] In high-frequency wireless communication, to eliminate phase noise, the 3GPP standard defines Phase-tracking Reference Signals (PTRS). At the base station, PTRS and Demodulation Reference Signals (DMRS) can be used together to cancel phase noise in uplink traffic channels. For random access channels, different PRACH sequences are repeatedly transmitted over multiple symbols; for example, PRACH format B4 is repeated over 12 symbols. Utilizing the characteristic of repeated transmission of random access signals, phase noise cancellation can be performed during random access preamble detection to maximize the multi-symbol data combining gain. Currently, published patents do not consider phase noise cancellation. Summary of the Invention

[0005] To overcome the shortcomings of the existing technology, the present invention provides a random access preamble sequence detection method based on 5G NR.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for detecting random access preamble sequences based on 5G NR, comprising:

[0008] Acquire the PRACH frequency domain signal;

[0009] Eliminate the phase difference between subcarriers and symbols of the PRACH frequency domain signal;

[0010] Inverse compensation is performed on the phase rotation factor of the PRACH frequency domain signal;

[0011] Eliminate Doppler frequency shift and phase noise between PRACH frequency domain signal symbols;

[0012] The PRACH frequency domain signal is coherently combined with the local root sequence using multiple symbols.

[0013] Using peak search, a preamble sequence is detected in the PRACH frequency domain signal after four steps: eliminating phase differences between subcarriers and symbols of the PRACH frequency domain signal, inversely compensating for the phase rotation factor of the PRACH frequency domain signal, eliminating Doppler frequency shift and phase noise between symbols of the PRACH frequency domain signal, and performing multi-symbol coherent merging of the PRACH frequency domain signal with the local root sequence.

[0014] Among them, the signal P after eliminating the Doppler frequency shift between PRACH frequency domain signal symbols l (k) is:

[0015] P l (k)=P1 l (k)*exp(j*(l-l1)*α doppler )

[0016]

[0017] In the formula, P1 l (k) is the PRACH frequency domain signal before eliminating Doppler frequency shift, α doppler Here, L is the Doppler frequency shift estimate, l is the symbol index within the current time slot where the PRACH signal is transmitted, angle() is the phase angle function, and L... RA The length of the PRACH leader sequence, l i+1 -l i =1, (k) is the PRACH frequency domain signal before eliminating Doppler shift.

[0018] Furthermore, the PRACH frequency domain signal after eliminating the phase differences between subcarriers and symbols of the PRACH frequency domain signal is as follows:

[0019] Y l (k)=X l (k)*exp(j*2*pi*(k-1+delta_k)*CP_diff l / FFTSize)

[0020] Among them, Y l (k) is the PRACH frequency domain signal to eliminate inter-carrier and inter-symbol phase differences, X l (k) is the PRACH frequency domain signal without eliminating the phase difference between subcarriers and symbols, delta_k is the offset between the PRACH signal subcarrier position and the zero-frequency subcarrier position, and FFTSize is the number of FFT points of the current system bandwidth.

[0021] In the formula,

[0022]

[0023] Among them, CP_diff l N represents the total number of sampling periods at the current system sampling rate. CP,PRACH N is the CP length of the PRACH signal. CP,PUSCH,s l0 is the CP length of the PUSCH signal for symbol s, and l0 is the starting symbol index of the PRACH signal.

[0024] Furthermore, the PRACH frequency domain signal after inverse compensation of the phase rotation factor of the PRACH frequency domain signal is as follows:

[0025] When l is greater than 0, the PRACH frequency domain signal after inverse compensation phase rotation factor is:

[0026] When l equals 0, the PRACH frequency domain signal after inverse compensation phase rotation factor is:

[0027] P1 l (k)=Y l (k)*exp(j*2*pi*f0*N CP,PUSCH,l＝0 *T s_current )

[0028] Among them, P1 l Yl(k) is the PRACH frequency domain signal after the inverse compensation phase rotation factor, Yl(k) is the PRACH frequency domain signal before the inverse compensation phase rotation factor, and f0 is the cell carrier frequency; N u,PUSCH,s T is the effective data length of PUSCH. s_current It is the sampling period of the current system sampling rate.

[0029] Furthermore, the signal after eliminating phase noise between PRACH frequency domain signal symbols is:

[0030] P2 l (k)=P l (k)*exp(j*α PN,l )

[0031] Among them, P2 l (k) is the PRACH frequency domain signal after eliminating inter-symbol phase noise, α PN，l This is the phase noise estimate;

[0032] In the formula,

[0033]

[0034] Furthermore, the signal used for multi-symbol coherent merging of the PRACH received signal and the local root sequence is:

[0035]

[0036] Where Corr is the merged PRACH signal, LocRootSeq(k) is the local root sequence frequency domain data, and N is the smallest positive integer greater than the length of the PRACH preamble sequence and a power of 2.

[0037] The random access preamble sequence detection method based on 5G NR provided by this invention has the following beneficial effects:

[0038] This invention addresses the issues of high computational complexity and the impact of phase noise on the gain of multi-symbol data merging in existing technologies. It utilizes an algorithm to eliminate Doppler shift and phase noise, obtaining a PRACH frequency domain signal free of Doppler shift and phase noise, which is then used to detect the preamble sequence. This method enables the detection of random access preamble sequences in high-speed mobile scenarios without the use of a restriction set. It boasts low implementation complexity, improves the detection performance of random access preamble sequences in high-frequency wireless communication, and reduces the false negative rate. Attached Figure Description

[0039] To more clearly illustrate the embodiments and design schemes of the present invention, the accompanying drawings required for this embodiment will be briefly described below. The drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a schematic diagram of a random access preamble sequence detection method based on 5G NR according to an embodiment of the present invention.

[0041] Figure 2This is a schematic diagram of the correlation peak energy drift caused by Doppler frequency shift in an embodiment of the present invention.

[0042] Figure 3 This is a schematic diagram of the correlation peaks after Doppler frequency shift elimination in an embodiment of the present invention. Detailed Implementation

[0043] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0044] Example:

[0045] This invention provides a method for detecting random access preamble sequences based on 5G NR, specifically as follows: Figure 1 As shown, the process includes: acquiring the PRACH frequency domain signal; eliminating phase differences between subcarriers and symbols of the PRACH frequency domain signal; inverse compensation of the phase rotation factor of the PRACH frequency domain signal; eliminating Doppler shift and phase noise between symbols of the PRACH frequency domain signal; performing multi-symbol coherent merging of the PRACH frequency domain signal and the local root sequence; and using peak search, performing preamble sequence detection on the PRACH frequency domain signal processed by the four steps of eliminating phase differences between subcarriers and symbols of the PRACH frequency domain signal, inverse compensation of the phase rotation factor of the PRACH frequency domain signal, eliminating Doppler shift and phase noise between symbols of the PRACH frequency domain signal, and performing multi-symbol coherent merging of the PRACH frequency domain signal and the local root sequence.

[0046] The signal P after eliminating the Doppler frequency shift between PRACH frequency domain signal symbols l (k) is:

[0047] P l (k)=P1 l (k)*exp(j*(l-l1)*α doppler )

[0048] Among them, P1 l (k) is the PRACH frequency domain signal before eliminating Doppler frequency shift, α doppler Here, l is the Doppler frequency shift estimate, and l is the symbol index within the current time slot where the PRACH signal is transmitted.

[0049] In the formula,

[0050]

[0051] Where angle() is the phase angle function, L RA The length of the PRACH leader sequence, l i+1-l i =1, (k) is the PRACH frequency domain signal before eliminating Doppler shift.

[0052] The following are specific embodiments of the present invention:

[0053] In the 3GPP specification, the system bandwidth is set to 100MHz, the PRACHformatB4 preamble sequence length is 139, occupying 12 RBs, the starting RB index is 1, the subcarrier spacing is 30KHz, the uplink service channel subcarrier spacing is 30KHz, the Doppler frequency shift is 2500Hz, the PreambleID is 0, and the delay is 64 times the current system sampling rate.

[0054] Step 1: Perform CP removal, phase rotation factor compensation, and FFT transform processing on the multiplexed uplink service channel. Extract the PRACH frequency domain signal based on the PRACH frequency domain resource location, denoted as X. l (k). Where l is the symbol index in the current time slot where the PRACH signal is transmitted, l = {2,...,13}; k = 1,...,L RA L RA It is the length of the PRACH leader sequence, which is 139.

[0055] Step 2: Eliminate the phase difference between subcarriers and symbols caused by CP removal.

[0056] Y l (k)=X l (k)*exp(j*2*pi*(k-1+delta_k)*CP_diff l / FFTSize)

[0057] Where delta_k is the offset between the PRACH signal subcarrier position and the zero-frequency subcarrier position, which is equal to -1624; The unit is the sampling period of the current system sampling rate, N. CP,PRACH The CP length of the PRACH signal is 1936; N CP,PUSCH,s 1 is the CP length of the PUSCH signal for symbol s, which is 288; l0 is the starting symbol index of the PRACH signal, which is 2; FFTSize is the number of FFT points of the current system bandwidth, which is 4096.

[0058] Step 3: Phase rotation factor inverse compensation.

[0059] The starting symbol index of PRACH is 2, therefore:

[0060]

[0061] Where f0 is the cell carrier frequency; Nu,PUSCH,s This is the effective data length of PUSCH; T s_current This is the sampling period of the current system sampling rate, with a value of 1 / (4096*30000) seconds;

[0062] Step 4: Doppler frequency shift or phase noise measurement and compensation.

[0063] Let the symbol indices of the transmitted PRACH be l0, l1, l2, ..., l N ={2,3,4,...,13}, a total of N=12 symbols are repeatedly transmitted. Calculate symbol l. i With l i+1 The phase difference between them is 0 < i < N-1.

[0064] For the Doppler phase shift caused by high-speed movement:

[0065]

[0066]

[0067] Step 5: Calculate the correlation

[0068] Let the frequency domain data of the local root sequence be LocRootSeq(k), k={1,2,3,...,L RA}. Calculate the condition that satisfies l0 < l < l N The correlation between the PRACH receive signal on symbol l of the condition and the local root sequence is performed, and multi-symbol coherent combining is carried out:

[0069]

[0070] Where N is the smallest positive integer that is greater than the length of the PRACH leader sequence and is an integer power of 2, N = 256.

[0071] Step 6: Peak Search

[0072] Peak search yields the Preamble ID and estimated TA value; related peaks are shown below. Figure 3 .

[0073] The superior technical effects of this invention are as follows:

[0074] 1. Without using a restricted set, it can support random access preamble sequence detection in high-speed mobile scenarios, with low implementation complexity and performance metrics for false positives and false negatives meeting the 38.104 protocol benchmark. (Comparison) Figure 2 and Figure 3 Under the same conditions, this scheme eliminates the energy drift caused by Doppler, thereby improving the detection signal-to-noise ratio of the PRACH signal.

[0075] 2. Improve the detection performance of random access preamble sequences in high-frequency wireless communication and reduce the false negative rate.

[0076] The above-described embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited thereto. Any simple changes or equivalent substitutions of the technical solutions that can be obviously obtained by those skilled in the art within the scope of the technology disclosed in the present invention shall fall within the scope of protection of the present invention.

Claims

1. A method for detecting random access preamble sequences based on 5G NR, characterized in that, include: Acquire the PRACH frequency domain signal; Eliminate the phase difference between subcarriers and symbols of the PRACH frequency domain signal; Inverse compensation is performed on the phase rotation factor of the PRACH frequency domain signal; Eliminate Doppler frequency shift and phase noise between PRACH frequency domain signal symbols; The PRACH frequency domain signal is coherently combined with the local root sequence using multiple symbols. Using peak search, a preamble sequence is detected in the PRACH frequency domain signal after four steps: eliminating phase differences between subcarriers and symbols of the PRACH frequency domain signal, inversely compensating for the phase rotation factor of the PRACH frequency domain signal, eliminating Doppler frequency shift and phase noise between symbols of the PRACH frequency domain signal, and performing multi-symbol coherent merging of the PRACH frequency domain signal with the local root sequence. The signal after eliminating the Doppler frequency shift between PRACH frequency domain signal symbols for: In the formula, To eliminate the PRACH frequency domain signal before the Doppler shift, This is an estimate of the Doppler frequency shift. The symbol index within the current time slot where the PRACH signal is transmitted. angle ( ) represents the phase angle function. The length of the PRACH leader sequence. , The first in the PRACH symbol set The PRACH frequency domain signal before Doppler shift elimination The imaginary unit, conj () is the complex conjugate function. The index in the PRACH symbol set; The PRACH frequency domain signal after eliminating the phase differences between subcarriers and symbols of the PRACH frequency domain signal is: in, To eliminate the phase difference between subcarriers and symbols in the PRACH frequency domain signal, For PRACH frequency domain signals that do not eliminate inter-carrier and inter-symbol phase differences, This is the offset between the PRACH signal subcarrier position and the zero-frequency subcarrier position. For the current system bandwidth points, Pi (π) is the mathematical constant of a circle. In the formula, ， in, The total number of sampling periods for the current system sampling rate. The CP length of the PRACH signal. Let be the CP length of the PUSCH signal for symbol s. It is the starting symbol index of the PRACH signal.

2. The method for detecting random access preamble sequences based on 5G NR according to claim 1, characterized in that, The PRACH frequency domain signal after inverse compensation of the phase rotation factor of the PRACH frequency domain signal is: when When the value is greater than 0, the PRACH frequency domain signal after the inverse compensation phase rotation factor is: when When the value is 0, the PRACH frequency domain signal after the inverse compensation phase rotation factor is: in, The PRACH frequency domain signal after inverse compensation phase rotation factor. The PRACH frequency domain signal before the inverse compensation phase rotation factor. For cell carrier frequency; The effective data length of PUSCH It is the sampling period of the current system sampling rate. For the first The CP length of each symbol, is the CP length of the symbol 0, where CP is the cyclic prefix.

3. The method for detecting random access preamble sequences based on 5G NR according to claim 1, characterized in that, The signal after eliminating phase noise between PRACH frequency domain signal symbols is: in, To eliminate inter-symbol phase noise in the PRACH frequency domain signal. This is the phase noise estimate; In the formula, 。 4. The method for detecting random access preamble sequences based on 5G NR according to claim 1, characterized in that, The signal used for multi-symbol coherent merging of the PRACH received signal and the local root sequence is: in, Corr The merged PRACH signal, The local root sequence frequency domain data is given, where N is the smallest positive integer greater than the length of the PRACH preamble sequence and a power of 2.

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