Method and apparatus for phase offset estimation and compensation for PRACH with large frequency offset

Abstract

Embodiments relate to methods and apparatus for phase offset estimation and compensation for physical random access channels (PRACHs) with large frequency offsets. In some embodiments, a method for physical random access channel (PRACH) preamble detection is presented. The method may comprise the steps of: receiving a PRACH preamble having a plurality of repetitive sequences, wherein each sequence comprises a plurality of elements on a plurality of antennas; selectively correlating a plurality of repetitive units in the plurality of repetitive sequences according to the amplitudes of the elements so as to perform phase offset estimation on the plurality of repetitive units; performing phase compensation on the plurality of repetitive units according to the estimated phase offset; performing sequence merging on the plurality of repetitive units; and performing sequence detection on the combined repetitive units.

Description

Technical Field

[0001] The present invention relates to the field of communications, and in particular, to a method and apparatus for phase offset estimation and compensation for a Physical Random Access Channel (PRACH) with a large frequency offset. Background Art

[0002] A PRACH preamble is a special sequence used for synchronization and identification in a wireless communication system. In Long Term Evolution (LTE) and 5th Generation Mobile Communication Technology (5G) systems, the PRACH preamble plays an important role in the random access process.

[0003] The PRACH preamble usually has multiple repeated sequences to improve coverage and anti-interference capabilities and support beam scanning. For example, there are 12 repeated sequences in format B4 (short sequence) and 4 repeated sequences in format 3 (long sequence). For example, a Zadoff-Chu (ZC) sequence with a symbol length of 139, 839, 569, or 1149 can be used as the PRACH sequence.

[0004] FIG. 1 shows an example of a decoding method 100 for a PRACH preamble. The signal can be received on multiple antennas, and the signal received on each antenna can include multiple sequences, such as 12 sequences, and each sequence can include multiple symbols. In the example method 100 of FIG. 1, a downsampling step 110, a serial-to-parallel conversion step 120, a correlation step 130, and a signal combining step 140 can be sequentially performed on the received signal. The signal combining step 140 can include sequence combining and antenna combining. Then, a detection step 150 can be performed on the combined sequences to determine the matching sequence by comparing with a local sequence.

[0005] That is to say, in the method 100 of FIG. 1, the sequences in the received signal are correlated in step 130 and then combined in step 140. Since the received signal has multiple sequences (such as 12 sequences) and is not combined, performing correlation processing on all 12 sequences will result in huge complexity both in the time domain and the frequency domain. Therefore, an improved method is to perform sequence combining first and then correlation, as shown in FIG. 2.

[0006] FIG2 shows an example of another decoding method 200 for a PRACH preamble. Compared with FIG1, FIG2 adds a sequence merging step 225 between the serial-to-parallel conversion step 120 and the correlation step 130. For example, in step 225, all 12 sequences may be merged into one sequence, thereby reducing the complexity of the correlation step 130. Then, in step 240, antenna merging may be performed. The method 200 in FIG2 may improve the decoding and detection of the PRACH preamble by reducing the complexity. However, there are still some problems.

[0007] In non-terrestrial networks (NTN), due to high mobility, the mismatch of carrier frequency offset (CFO) between transmitter and receiver may be larger than that of terrestrial networks. For example, in NTN networks relayed by satellites (or satellite networks), due to the high mobility of satellites (especially low-orbit satellites), Doppler shift will cause CFO mismatch between transmitter and receiver. Similar problems may also exist in mobile networks related to high-speed trains (HST), which is considered to be one of the important vertical fields in 5G applications. Due to the rapid movement of trains and mobile devices on trains, there is a very large CFO. Prior information about satellite orbits or trains cannot effectively mitigate the impact of CFO. After CFO pre-compensation, there is still a non-negligible residual CFO.

[0008] At the transmitting end, these sequences originally transmit the same signal, but if there is a large CFO, different sequences will have different phase offsets at the receiving end. Figure 3 shows the phase offsets of different sequences of the received signal. For example, as shown in Figure 3, the first sequence (sequence 0) can be considered to be phase-aligned, but the subsequent sequences may have phase offsets caused by CFO. The phase offset can be accumulated over time, that is, the phase offset of each symbol may be greater than the previous symbol. The slope of the phase offset may be CFO. That is, the phase offset of sequence 1 is ΔΦ, the phase offset of sequence 2 is 2ΔΦ, and so on. Phase offset may be detrimental to the sequence merging introduced in step 225 of Figure 2, because if the phase offset between sequences or symbols is 180 degrees (or π), they will cancel each other. Therefore, the detection performance may be poor.

[0009] Patent document CN108040366A proposes a random access preamble signal detection method based on frequency offset correction, including: calculating available time-frequency resources, generating 64 preamble sequences, and randomly selecting one preamble sequence as the transmitted preamble sequence; finding a subframe, where the current is the PRACH time domain subframe; estimating the Doppler frequency offset value according to relevant parameters by the maximum likelihood (ML) criterion as the frequency offset compensation; performing cyclic prefix cancellation, decimation filtering and Fourier transform on the processed signal; performing frequency domain correlation between the preamble sequence and the local ZC root sequence; performing inverse fast Fourier transform, modulus square and multi-antenna combination on the frequency domain correlation sequence, calculating the power delay spectrum energy (PDP), and comparing the power delay spectrum energy (PDP) with the detection thresholds A and B to obtain the preamble sequence number ID and the time advance (TA). However, the method of CFO first and then decimation in CN108040366A may be more difficult to directly process the undecimated signal, and storing the undecimated signal will increase the storage overhead. The particular problem of CN108040366A may be that it assumes a known time offset and depends on the accuracy of the signal-to-noise ratio (SNR) estimation.

[0010] Patent document CN112887241A proposes a frequency offset estimation method and device, a communication device and a storage medium. The method includes: when it is detected that there is an access signal in the PRACH signal transmitted by the signal transmitter, obtaining the main peak and the secondary peak of the PRACH signal, where the PRACH signal is composed of a preset number of identical pilot sequences; determining the first frequency offset according to the peak value of the main peak and the peak value of the secondary peak; performing frequency offset compensation on the PRACH signal according to the first frequency offset to obtain a compensated sequence after frequency offset compensation; calculating the frequency offset between the compensated sequence and the pilot sequence to obtain the second frequency offset, and estimating the time delay of the access signal according to the second frequency offset. Patent documents US9491024B2, WO2010040264A1, WO2013172748A1 (US20150139098A1) propose related post-CFO methods similar to those in CN112887241A. However, the post-CFO method in CN112887241A cannot be used for the considered situation, that is, estimating the phase offset before correlation, and the peak value can only be obtained after correlation. The particular problem existing in CN112887241A may be that the PRACH format is modified, so it is not suitable for the PRACH format specified by the 3rd Generation Partnership Project (3GPP), and it may be very complex. Summary of the Invention

[0011] It can be seen that for PRACH reception in the case of a large CFO, if the sequences are combined after correlation (Figure 1), it may result in huge complexity; while if the sequences are combined before correlation (Figure 2), it may lead to poor detection performance. Therefore, the aim is to propose a new algorithm for CFO estimation / compensation before early combining and achieve a good balance between complexity and detection performance.

[0012] In view of the above, embodiments of the present invention propose a method and apparatus for phase offset estimation and compensation for a physical random access channel (PRACH) with a large frequency offset.

[0013] In some embodiments, a method for PRACH preamble detection is proposed. The method may at least include the following steps: receiving a PRACH preamble having a plurality of repeated sequences, where each sequence includes a plurality of elements on a plurality of antennas; selectively correlating a plurality of repeating units in the plurality of repeated sequences according to the amplitudes of the elements, thereby performing phase offset estimation on the plurality of repeating units; performing phase compensation on the plurality of repeating units according to the estimated phase offset; performing sequence combining on the plurality of repeating units; and performing sequence detection on the combined plurality of repeating units.

[0014] In some embodiments, a PRACH receiver in a wireless communication system is proposed. The PRACH receiver may include a memory storing machine-readable instructions; and a processor for executing the machine-readable instructions. When the processor executes the machine-readable instructions, it configures the PRACH receiver to: receive a PRACH preamble having a plurality of repeated sequences, where each sequence includes a plurality of elements on a plurality of antennas; selectively correlate a plurality of repeating units in the plurality of repeated sequences according to the amplitudes of the elements, thereby performing phase offset estimation on the plurality of repeating units; perform phase compensation on the plurality of repeating units based on the estimated phase offset; perform sequence combining on the plurality of repeating units; and perform sequence detection on the combined plurality of repeating units.

[0015] In some embodiments, a computer-readable product is proposed, including computer-readable code that, when run on a device, causes the device to execute the above method.

[0016] The embodiments propose a new algorithm for CFO estimation / compensation before early combining and have a good balance between complexity and detection performance. For example, the embodiments may have a low missed detection rate (MDR), where MDR represents that the PRACH has been transmitted but not detected (i.e., missed detection); the embodiments may also have a low false alarm rate (FAR), where FAR represents that the PRACH has not been transmitted, but the receiver erroneously detects the PRACH (i.e., false alarm). Brief Description of the Drawings

[0017] The drawings are incorporated into the present disclosure and form a part of the specification, showing various embodiments of the present disclosure, and are further used together with the specification to explain the principles of the present disclosure and enable those skilled in the relevant art to manufacture and use the embodiments of the present disclosure. In the drawings, the same reference numerals denote the same or functionally similar elements, where:

[0018] FIG. 1 shows an example of a method for decoding a PRACH preamble;

[0019] FIG. 2 shows another example of a method for decoding a PRACH preamble;

[0020] FIG. 3 shows the phase offsets of different sequences of received signals;

[0021] Figure 4 shows an example of a method for decoding a PRACH preamble according to an embodiment of the present invention;

[0022] Figure 5 shows the amplitude variation of the non-downsampled signal;

[0023] Figure 6 shows an example of a method for estimating phase offset according to an embodiment of the present invention;

[0024] Figure 7 shows an example of a method for compensating phase offset according to an embodiment of the present invention;

[0025] Figure 8 shows an example of a PRACH receiver according to an embodiment of the present invention;

[0026] Figure 9 shows an example of a computer-implemented device according to an embodiment of the present invention. Detailed Description of the Embodiments

[0027] Embodiments of the present invention will be described in detail below with reference to the drawings, in which the embodiments are shown. However, these embodiments of the present invention can be embodied in many different forms and should not be construed as limited to the embodiments described herein. The elements in the drawings are not necessarily drawn to scale with each other.

[0028] Reference to "an embodiment" or "embodiments" means that a particular feature, structure, or characteristic related to the embodiment is included in at least one embodiment. Thus, the phrase "in an embodiment" appearing throughout the specification does not necessarily refer to the same embodiment.

[0029] The singular forms “a,” “an,” and “the” as used in the specification and the appended claims also include the plural forms unless the context clearly dictates otherwise. Further, it should be understood that the term “and / or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[0030] In this specification and the claims, a list of items joined by “at least one” or “one or more” can refer to any combination of the listed terms. For example, the phrase “at least one of A, B, or C” can mean A; B; C; A and B; A and C; B and C; or A, B, and C.

[0031] Figure 4 An example of a method for decoding a PRACH preamble showing an embodiment of the present invention is presented. In Figure 4 comparison with FIG. 2, method 400 may further include a phase offset estimation step 421 and a phase offset compensation step 422. Note that the phase offset estimation step 421 and the phase offset compensation step 422 can be combined into one phase offset estimation and compensation step.

[0032] In Figure 4 the example method 400, the received signal can be sequentially subjected to a downsampling step 110, a serial-to-parallel conversion step 120, a phase offset estimation step 421, a phase offset compensation step 422, a sequence combining step 225, a correlation step 130, an antenna combining step 240, and a detection step 150.

[0033] In one example, the method is implemented on a non-terrestrial network (NTN) PRACH receiver, such as a receiver for a high-speed railway or satellite system.

[0034] In one example, prior to the phase offset estimation step 421 and the phase offset compensation step 422, there can be a pre-compensation step in which the sequence (i.e., the repeating unit) can be pre-compensated based on satellite orbit information. Then the remaining (or residual) phase offset is estimated and compensated in the phase offset estimation step 421 and the phase offset compensation step 422, respectively.

[0035] The PRACH preamble signal can be received on multiple antennas, and the signal received on each antenna can include multiple sequences, such as 12 sequences, and each sequence can include multiple symbols.

[0036] The multiple antennas can be represented as i = 1, 2, …, I, where I is the maximum number of antennas considered;

[0037] The multiple sequences can be represented as s = 1, 2, …, S, where S is the maximum number of sequences considered;

[0038] Multiple symbols in each sequence can be sampled into multiple samples, which can be expressed as n = 1, 2, …, N, where N is the maximum number of samples considered.

[0039] For example, the PRACH receiver may receive a total of 12 sequences, and these 12 sequences can be repeated sequences. That is, they are the same at the transmitting end. For example, to reduce the computational complexity, the proposed method can consider only 6 sequences. These 6 sequences can also be referred to as “repetition”.

[0040] In one example, the multiple sequences (i.e., sequence repetition units) used in the calculation can be all of the multiple repeated sequences (e.g., all 12 sequences), or a part of the multiple repeated sequences (e.g., 6 sequences out of all 12 sequences). From the perspective of the signal, the multiple sequences (i.e., sequence repetition units) used in the calculation can be all or part of the preamble signals received on multiple antennas.

[0041] Then, the received sequence can be expressed as y(s, n, i); the sequence with a sequence interval received can be expressed as y(s - m, n, i)’, where the sequence distance (or sequence interval) between the sequence y(s - m, n, i)’ and the sequence y(s, n, i) can be m = 1, 2, …, S - 1. For example, the sequence distance (or sequence interval) between sequence 10 and sequence 11 is 1.

[0042] According to the above representation, for a given sequence interval m, one method to estimate ΔΦ(m) can be:

[0043] where ΔΦ(m) refers to ΔΦ calculated through the sequence interval m (as shown in Figure 3), and does not refer to the estimated phase offset of sequence m. In fact, the estimated phase offset of sequences s = 1, 2, …, S should be s * ΔΦ.

[0044] As shown in Equation (1), two sequences, namely the sequence y(s - m, b, i)’ and the sequence y(s, n, i), are correlated through conjugate multiplication. Then, the correlation value is converted into an angle to obtain the phase offset of the sequence interval m, and then the phase offset of the sequence interval m is divided by m to obtain the normalized phase offset ΔΦ(m), that is, the phase offset of a single sequence interval (i.e., the phase offset between two adjacent sequences).

[0045] In one example, performing phase offset estimation includes calculating the correlation phase of two repetition units, for the combination of two repetition units, as shown in the calculation of “angle()” in Equation (1).

[0046] If equation (1) holds for all possible values of m, such as m = 1, 2, … S - 1, then the final ΔΦ can be:

[0047] As shown in equation (2), for each value of m, such as m = 1, 2, … S - 1, the merging of two sequences, namely sequence y(s - m, n, i)' and sequence y(s, n, i), is performed by conjugate multiplication for correlation. Then, each correlation value is converted to an angle to obtain the phase shift for sequence interval m. Then, each phase shift for sequence interval m is divided by m to obtain the normalized phase shift ΔΦ(m), which is the phase shift for a single sequence interval (i.e., the phase shift between two adjacent sequences). Then, the average of the m ΔΦ(m) values can be taken to form the final ΔΦ.

[0048] Depending on whether m = 1, the two sequences in the merging may be adjacent repeating units or non - adjacent repeating units. For adjacent repeating units, m = 1.

[0049] It should be noted that normalization and averaging can be regarded as a single calculation, namely weighted averaging. That is, in equation (2), for all mergings used, the estimated phase shift is the weighted average of the relevant phases of two repeating units with respect to the distance between the two repeating units (i.e., sequence interval m).

[0050] In a specific example of equation (2), if there are 12 sequences. Using all possible mergings of any two sequences, then the number of mergings of two sequences may be kinds.

[0051] In one example, all 66 possible mergings are used for the phase shift estimation in step 421, or only a part of the mergings are used for the phase shift estimation.

[0052] In one example, to reduce complexity, a threshold can be set for the sequence interval m, that is, the mergings of two repeating units where the sequence interval m (or sequence distance) is less than or equal to the threshold are all used for the phase shift estimation.

[0053] For example, the threshold can be set to 6. In this way, sequence 1 can be correlated with sequence 7, but not with sequence 8. Then, in step 421, only 51 out of all 66 possible mergings are used for the phase shift estimation.

[0054] Using all 66 possible mergings of sequences (or repeating units) has too high a complexity. The embodiment can further suggest correlating multiple repeating units according to the amplitude of the elements to reduce complexity. Figure 5 Shows the amplitude variation of the non - decimated signal. As Figure 5As shown, there may be amplitude variations in the non-downsampled signal, i.e., some samples may be stronger than others. Here, the term "element" may refer to the samples on the antenna, e.g., 1024 samples on 4 antennas.

[0055] The embodiments believe that stronger samples may result in sample correlation values, i.e., larger correlations may come from dominant elements.

[0056] In one example, larger correlation values can be considered. For example, in the phase offset estimation of step 421, the top k of 51 combinations out of all 66 possible combinations, or the top k of all 66 possible combinations, can be considered.

[0057] In one example, in the phase offset estimation of step 421, the first one of 51 combinations out of all 66 possible combinations, or the first one of all 66 possible combinations, i.e., k = 1, can be considered.

[0058] Figure 6 Shows an example of the phase offset estimation method of the embodiments of the present invention. In Figure 6 the antenna size is not shown. As Figure 6 shown in the upper part of Figure 6 the horizontal axis is the sample axis and the vertical axis is the sequence axis. As

[0059] Note that Figure 6 the sequence lengths shown in

[0060] are only examples, and each sequence may include more or fewer samples. For example, there may be 1024 samples in a sequence.

[0061] In one example, for Figure 6 each of the 8 elements in the sequence shown in Figure 6 there can be 4 elements in a column of

[0062] For example, for sample 1 (element 1) which can be referred to as "a specific position of multiple repeating units", there are 4 elements in the first column. Figure 6Shown as a column), the dominant elements that are dominant will be selected. For the position (n, i) (i.e., the specific sample n on the specific antenna i), the dominant elements s1, s2 can be expressed as s1(n, i), s2(n, i), (s1 < s2) having the two largest In one example, the dominant elements may have the largest magnitude, that is, they are the dominant elements in terms of magnitude.

[0063] It should be noted that in this example, the two dominant elements with the largest magnitude are used for correlation, that is, the correlation is the correlation between a combination including the two dominant elements. However, this example is not limited to this. In another example, three dominant elements with the largest magnitude can be used for correlation, that is, there are three correlations, and each correlation is the correlation between a combination including two of the three dominant elements.

[0064] In one example, multiple elements at specific positions in multiple repeating units are compared, and the two dominant elements with the largest magnitude are selected from the multiple elements. For example, the dominant elements at position 1 ( Figure 6 in the first column) may be in sequences 1 and 4, the dominant elements at position 2 ( Figure 6 in the second column) may be in sequences 1 and 3, the dominant elements at position 3 ( Figure 6 in the third column) may be in sequences 1 and 2, the dominant elements at position 4 ( Figure 6 in the fourth column) may be in sequences 1 and 4, the dominant elements at position 5 ( Figure 6 in the fifth column) may be in sequences 2 and 4, the dominant elements at position 6 ( Figure 6 in the sixth column) may be in sequences 1 and 3, the dominant elements at position 7 ( Figure 6 in the seventh column) may be in sequences 3 and 4, the dominant elements at position 8 ( Figure 8 in the eighth column) may be in sequences 1 and 3.

[0065] In one example, the two repeating units where the two dominant elements at a specific position are located are correlated. To correlate the dominant elements, in one example, the distance (i.e., the sequence interval m) between the dominant elements at each position can be calculated. For example, for positions 1 - 8, m = {3, 2, 1, 3, 2, 2, 1, 2}. For each position (n, i), the sequences with the same sequence interval m can be correlated.

[0066] For example, as Figure 6As shown at the bottom, for positions 1 and 4 where m = 3, sequence 1 can be correlated with sequence 4; for positions 2, 5, 6, and 8 where m = 2, sequence 1 can be correlated with sequence 3, and sequence 2 can be correlated with sequence 4; for positions 3 and 7 where m = 1, sequence 1 can be correlated with sequence 2, sequence 2 can be correlated with sequence 3, and sequence 2 can be correlated with sequence 4.

[0067] That is to say, equation (2) may become the following equation (3), where the dominant elements for each position are correlated. where G(m) = {(n,i) with s2(n,i) - s1(n,i) == m} Equation (3)

[0068] In Figure 6 and in the example shown in equation (3), the phase offsets obtained from the correlation operation can be weighted-averaged to obtain the final ΔΦ.

[0069] Compared with equation (1), for equation (3), for each position in the sequence, the correlation can be performed only once. Therefore, equation (3) can be regarded as a single correlation in terms of position. Thus, the complexity of phase offset estimation can be significantly reduced, especially for sequences with a large number of samples (such as 1149 samples). Through equation (3), the elements with the greatest influence and the strongest noise immunity can be captured while reducing the complexity.

[0070] It should be noted that some further improvements to equation (1) or equation (2) can also be applied to equation (3). For example, a threshold for the sequence interval m can be set, that is, each merge including two repeating units with a sequence interval m (or sequence distance) less than or equal to the threshold is used for phase offset estimation.

[0071] Depending on whether m = 1, the two sequences in the merge can be adjacent repeating units or non-adjacent repeating units. For adjacent repeating units, m = 1.

[0072] Figure 7 Shows an example of the phase offset compensation method according to an embodiment of the present invention. In Figure 7 the example, according to the estimated phase offset ΔΦ, all elements within a repeating unit are compensated with a constant value.

[0073] For example, as Figure 7 shown, for the s-th sequence, y(s,n,i) is updated as follows: y update (s,n,i) = y(s,n,i) * exp(j * ΔΦ * (s - 1)) Equation (4)

[0074] For example, in one example ( Figure 7 compensation scheme 1 in), sequence 0 is regarded as the first sequence. Then, for all symbols in the subsequent sequence 1, the phase offset compensation is the same, i.e., ΔΦ; for all symbols in the subsequent sequence 2, the phase offset compensation is the same, i.e., 2*ΔΦ, and so on.

[0075] In addition, in another method ( Figure 7 compensation scheme 2 in), symbols in the same sequence can be compensated with different phase offsets, that is, the phase offset compensation for the first symbol is less than that for the last symbol. In this way, the phase offset compensation can be linear, as Figure 7 shown.

[0076] In one example, if there are 256 symbols in a sequence, then the phase offset compensation for each symbol may be ΔΦ / 256 more than that for the previous symbol.

[0077] Comparison Figure 7 between the two compensation schemes in, the preferred compensation scheme 1 is because its complexity is lower, and the constant part of each sequence has the greatest impact on performance. In addition, compensation scheme 1 is also suitable for a larger CFO. For example, ΔΦ may be greater than 360 degrees (or 2π). At this time, ΔΦ / 256 may be incorrect because the estimated ΔΦ may actually be ΔΦ - 2π. That is to say, although there is no difference between ΔΦ and ΔΦ - 2π for correlation or sequence combination (they can be regarded as the same phase), ΔΦ / 256 and (ΔΦ - 2π) / 256 may be completely different in phase.

[0078] It should be noted that the above-mentioned proposed features can be combined with each other to further improve the balance between complexity and detection performance.

[0079] The performance of different schemes can be compared: the prior art scheme (1) shown in Figure 1; the prior art scheme (2) shown in Figure 2; the proposed scheme (3) using equation (1) or equation (2) (let m = 1) and equation (4); the proposed scheme (3) using equation (3) or equation (4).

[0080] By comparing the missed detection rate (MDR) and false alarm rate (FAR) of schemes (1) to (4) in the case of FR2 B460kHz SCS in the 3GPP standard, the following Table 1 can be obtained. Table 1: Simulated performance of each scheme

[0081] As can be seen from Table 1, the proposed solutions, especially the proposed solution (4), can meet the requirements of 3GPP for the large CFO miss detection rate and can achieve better MDR and FAR performance than the existing technology solutions.

[0082] The complexity of solution (1) in Figure 1 (where merging is performed after correlation) can be given in the following table (in operations). For short sequences, assume there are 12 sequences with 256 symbols each, and for long sequences, assume there are 4 sequences with 1024 symbols each. Table 2: Simulation complexity of the existing technology solution (1) for short sequences For short sequences Each call Call count Subtotal FFT 256*log2(256) 2*12 49152 Multiplication 256 2*12*64 393216 IFFT 256*log2(256) 2*12*64 3145728 Power 256 2*12*64 393216 Merge antennas / sequences 2*12 256*64 393216 Total 4374528 Table 3: Simulation complexity of the existing technology solution (1) for long sequences

[0083] Then, for both short and long sequences, the proposed solution (4) can significantly reduce the complexity, as shown in the following table for example. Table 4: Simulation complexity of the proposed solution (4) for short sequences For short sequences Each call Call count Subtotal Find dominant element 2*256*11*2 11264 Phase estimation 2*256*2+11*3 1057 Compensation 256 11*2 5632 Merge sequences 12 256*2 6144 FFT 256*log2(256) 2 4096 Multiplication 256 2*64 32768 IFFT 256*log2(256) 2*64 262144 Power 256 2*64 32768 Merge antennas 2 256*64 32768 Total 388641 Table 5: Simulation complexity of the proposed solution (4) for long sequences For long sequences Each call Call count Subtotal Find dominant element 2*1024*3*2 12288 Phase estimation 2*1024*2+3*3 4105 Compensation 1024 3*2 6144 Merge sequences 4 1024*2 8192 FFT 1024*log2(1024) 2 20480 Multiplication 2048 2*64 262144 IFFT 2048*log2(2048) 2*64 2883584 Power 2048 2*64 262144 Merge antennas 2 2048*64 262144 Total 3721225

[0084] Comparing solution (1) and solution (4), in terms of complexity, the proposed solution (4) can reduce the complexity of short sequences by 11.26 times and the complexity of long sequences by 3.97 times.

[0085] It should be noted that compared with solution (2) or (3) (which are basically the same in terms of complexity), the proposed solution may slightly increase the complexity, by 6.6% and less than 8.3% for short and long sequences respectively.

[0086] Figure 8 Shows an example PRACH receiver 800 of an embodiment of the present invention. In one embodiment, Figure 8 the example PRACH receiver 800 in can be configured to execute the above method 400.

[0087] In one embodiment, the PRACH receiver 800 may include a processor 801; and a memory 802 connected to the processor 801. The memory 802 may store instructions executable by the processor 801. When the processor 801 executes the instructions, the processor 801 may be configured to execute the above method 400.

[0088] Note that the PRACH receiver 800 can be implemented in the form of hardware, software, firmware, and any combination thereof. For example, the PRACH receiver 800 can include multiple units, circuits, modules, etc., and each unit, circuit, module, etc. can be used to execute one or more steps of the example method 400.

[0089] In one embodiment, the PRACH receiver 800 can be implemented in a network node of a Radio Access Network (RAN). Examples of network nodes include, but are not limited to, access points (APs) (e.g., wireless access points), base stations (BSs) (e.g., wireless base stations, Node B, evolved Node B (eNB), and NR Node B (gNB)), O-RAN nodes, or components of O-RAN nodes (e.g., O-RU, O-DU, O-CU).

[0090] Figure 9 An example of a computer-implemented apparatus 900 according to an embodiment of the present invention is shown. In one embodiment, the apparatus 900 can be configured as the above-described PRACH receiver as Figure 8 shown.

[0091] In one embodiment, the apparatus 900 can include, but is not limited to, at least one processor, such as a central processing unit (CPU) 901, a computer-readable medium 902, and a memory 903. The memory 903 can include volatile (e.g., random access memory RAM) and / or non-volatile memory (e.g., hard disk or flash memory). In one embodiment, the computer-readable medium 902 can be configured to store a computer program and / or instructions that, when executed by the processor 901, cause the processor 901 to execute any one of the above methods 400.

[0092] In one embodiment, the computer-readable medium 902 (such as a non-transitory computer-readable medium) can be stored in the memory 903. In another embodiment, the computer program can be stored in a remote location, such as a computer program product 904 (which can also be embodied as a computer-readable medium), and accessed by the processor 901 through a carrier 905.

[0093] The computer-readable medium 902 and / or the computer program product 904 may be distributed and / or stored on a removable computer-readable medium, such as a floppy disk, a CD (compact disc), a DVD (digital video disc), a flash memory, or a similar removable storage medium (such as a compact flash, an SD (secure digital), a memory stick, a mini SD card, an MMC (multimedia card), a smart media), an HD-DVD (high definition DVD) or a Blu-ray DVD, a USB (universal serial bus)-based removable storage medium, a magnetic tape medium, an optical storage medium, a magneto-optical medium, a magnetic bubble memory, or propagated as a propagated signal through a network (such as Ethernet, ATM, ISDN, PSTN, X.25, the Internet, a local area network (LAN), or a similar network capable of transmitting data packets to an infrastructure node).

[0094] The present disclosure further presents the following examples.

[0095] Example 1. A method for physical random access channel (PRACH) preamble detection, comprising: - receiving a PRACH preamble having a plurality of repeated sequences, wherein each sequence includes a plurality of elements on a plurality of antennas; - selectively correlating a plurality of repeating units in the plurality of repeated sequences according to the amplitudes of the elements, so as to estimate a phase shift of the plurality of repeating units; - performing phase compensation on the plurality of repeating units according to the estimated phase shift; - performing sequence merging on the plurality of repeating units; and - performing sequence detection on the merged plurality of repeating units.

[0096] Example 2. The method according to claim 1, wherein a plurality of elements respectively located at specific positions of the plurality of repeating units are compared to select two dominant elements that are dominant in amplitude from the plurality of elements; and wherein, for the specific position, correlation is performed on two repeating units where the two dominant elements are respectively located.

[0097] Example 3. The method according to claim 2, wherein the two repeating units are non-adjacent repeating units.

[0098] Example 4. The method according to Example 1, wherein the plurality of repeating units are all or part of the plurality of repeated sequences, or all or part of the preamble signals received on the plurality of antennas.

[0099] Example 5. The method according to Example 2, wherein all possible combinations or partial possible combinations of any two of the plurality of repeating units are used for phase offset estimation, or, each combination of two repeating units having a distance less than or equal to a threshold is used for phase offset estimation.

[0100] Example 6. The method according to Example 5, wherein performing phase offset estimation includes, for a combination including the two repeating units, calculating the relative phase of the two repeating units.

[0101] Example 7. The method according to Example 6, wherein for all used combinations, the estimated phase offset is a weighted average of the relative phase of the two repeating units with respect to the distance between the two repeating units.

[0102] Example 8. The method according to Example 1, wherein for a specific position of the plurality of repeating units, all possible combinations of any two of the plurality of repeating units are correlated to select k combinations with the top k correlation values; wherein the k correlation values are used for phase offset estimation.

[0103] Example 9. The method according to Example 1, wherein in phase compensation, according to the estimated phase offset, all elements within a repeating unit are compensated with a constant value.

[0104] Example 10. The method according to Example 1, wherein the method is implemented on a non-terrestrial network (NTN) PRACH receiver; and wherein the method further includes: - Before performing phase offset estimation, pre-compensating the plurality of repeating units according to satellite orbit information.

[0105] Example 11. A PRACH receiver in a wireless communication system, the PRACH receiver comprising: a memory storing machine-readable instructions; and a processor for executing the machine-readable instructions such that when the processor executes the machine-readable instructions, the PRACH receiver is configured to: - Receive a PRACH preamble having a plurality of repeating sequences, wherein each sequence includes a plurality of elements on a plurality of antennas; - Selectively correlate the plurality of repeating units in the plurality of repeating sequences according to the amplitudes of the elements, thereby performing phase offset estimation on the plurality of repeating units; - Perform phase compensation on the plurality of repeating units according to the estimated phase offset; - Perform sequence combination on the plurality of repeating units; and - Perform sequence detection on the combined plurality of repeating units.

[0106] Example 12. The PRACH receiver according to Example 11, wherein, a plurality of elements respectively located at specific positions of a plurality of repeating units are compared, and two dominant elements that are dominant in amplitude are selected from the plurality of elements; wherein, for a specific position, correlation is performed on two repeating units where the two dominant elements are respectively located.

[0107] Example 13. The PRACH receiver according to Example 12, wherein the two repeating units are non - adjacent repeating units.

[0108] Example 14. The PRACH receiver according to Example 11, wherein the plurality of repeating units are all or part of a plurality of repeating sequences, or all or part of the preamble signals received on a plurality of antennas.

[0109] Example 15. The PRACH receiver according to Example 12, wherein all possible combinations or partial possible combinations of any two repeating units among the plurality of repeating units are used for phase offset estimation, or combinations of two repeating units with a distance less than or equal to a threshold are used for phase offset estimation.

[0110] Example 16. The PRACH receiver according to Example 15, wherein the phase offset estimation includes: for a combination including two repeating units, calculating the phase of the correlation between the two repeating units.

[0111] Example 17. The PRACH receiver according to Example 16, wherein for all used combinations, the estimated phase offset is a weighted average of the phase of the correlation between the two repeating units with respect to the distance between the two repeating units.

[0112] Example 18. The PRACH receiver according to Example 11, wherein for a specific position of the plurality of repeating units, all possible combinations of any two repeating units among the plurality of repeating units are correlated to select k combinations with the top k correlation values; wherein the k correlation values are used for phase offset estimation.

[0113] Example 19. The PRACH receiver according to Example 11, wherein in phase compensation, according to the estimated phase offset, all elements within a repeating unit are compensated with a constant value.

[0114] Example 20. A computer - readable product, comprising computer - readable code that, when run on a device, causes the device to execute any one of the above - mentioned methods.

[0115] It should be recognized that the principles of the present disclosure are not limited to the described embodiments, but can be modified and changed without departing from the scope of the appended claims. The above embodiments may include only a subset of these features, different orders of these features, different combinations of these features, and / or more features in addition to the explicitly listed features. Therefore, the scope of the embodiments should be determined with reference to the appended claims and the scope of all equivalents given by these claims.

Claims

1. A method for detecting a physical random access channel (PRACH) preamble, comprising: - receiving a PRACH preamble having multiple repeating sequences, wherein each sequence comprises multiple elements on multiple antennas; - selectively correlating a plurality of repeating units in the plurality of repeating sequences according to the amplitude of the element, thereby estimating a phase offset of the plurality of repeating units; - performing phase compensation on the plurality of repeating units according to the estimated phase offset; - performing sequence merging on the plurality of repeating units; as well as - Perform sequence detection on the combined multiple repeat units.

2. The method according to claim 1, in, comparing a plurality of elements respectively located at specific positions of the plurality of repeating units, and selecting two dominant elements that are dominant in amplitude from the plurality of elements; Wherein, for the specific position, the two repeating units where the two dominant elements are respectively located are correlated. The method according to claim 2 , wherein the two repeating units are non-adjacent repeating units. 4 . The method according to claim 1 , wherein the plurality of repetition units are all or part of the plurality of repetition sequences, or are all or part of the preamble signals received on the plurality of antennas.

5. The method according to claim 2, wherein all possible combinations or partial possible combinations of any two repeating units among the multiple repeating units are used for the phase offset estimation, or the combination of two repeating units whose distance is less than or equal to a threshold is used for the phase offset estimation.

6. The method of claim 5, wherein performing phase offset estimation comprises: For a merge including the two repeating units, the phases of the correlation of the two repeating units are calculated.

7. The method of claim 6, wherein for all used combinations, the estimated phase offset is a weighted average of the relative phases of the two repeating units relative to the distance of the two repeating units.

8. The method according to claim 1, wherein for a specific position in the plurality of repeating units, all possible combinations of any two repeating units in the plurality of repeating units are correlated to select k combinations with the highest top k correlation values; in, The k correlation values ​​are used for the phase offset estimation.

9. The method according to claim 1, wherein in the phase compensation, all elements within a repeating unit are compensated using a constant value according to the estimated phase offset.

10. The method of claim 1, wherein the method is implemented on a non-terrestrial network (NTN) PRACH receiver; The method further comprises: - Before performing the phase offset estimation, pre-compensating the plurality of repetitive units according to satellite orbit information.

11. A PRACH receiver in a wireless communication system, the PRACH receiver comprising: a memory storing machine-readable instructions; as well as A processor configured to execute the machine-readable instructions, such that when the processor executes the machine-readable instructions, a PRACH receiver is configured to: - receiving a PRACH preamble having multiple repeating sequences, wherein each sequence comprises multiple elements on multiple antennas; - selectively correlating a plurality of repeating units in the plurality of repeating sequences according to the amplitude of the element, thereby estimating a phase offset of the plurality of repeating units; - performing phase compensation on the plurality of repeating units according to the estimated phase offset; - performing sequence merging on the plurality of repeating units; as well as - Perform sequence detection on the combined multiple repeat units.

12. The PRACH receiver according to claim 11, in, comparing a plurality of elements respectively located at specific positions of the plurality of repeating units to select two dominant elements that are dominant in magnitude from the plurality of elements; Wherein, for the specific position, the two repeating units where the two dominant elements are respectively located are correlated.

13. The PRACH receiver of claim 12, wherein the two repetition units are non-adjacent repetition units.

14. The PRACH receiver according to claim 11, wherein the plurality of repetition units are all or part of the plurality of repetition sequences, or are all or part of the preamble signals received on the plurality of antennas.

15. The PRACH receiver according to claim 12, wherein: All possible combinations or partial possible combinations of any two repeating units among the multiple repeating units are used for the phase offset estimation, or the combination of two repeating units whose distance is less than or equal to a threshold is used for the phase offset estimation.

16. The PRACH receiver of claim 15, wherein performing phase offset estimation comprises: For a merge including the two repeating units, the phases of the correlation of the two repeating units are calculated.

17. The PRACH receiver of claim 16, wherein for all used combining, the estimated phase offset is a weighted average of the relative phases of the two repetition units relative to the distance of the two repetition units.

18. The PRACH receiver according to claim 11, wherein: For a specific position in the plurality of repeating units, correlating all possible combinations of any two repeating units in the plurality of repeating units to select k combinations with the highest top k correlation values; The k correlation values ​​are used for the phase offset estimation.

19. The PRACH receiver according to claim 11, wherein in the phase compensation, all elements within a repetition unit are compensated with a constant value according to the estimated phase offset.

20. A computer readable product comprising computer readable code which, when executed on a device, causes the device to: - receiving a PRACH preamble having multiple repeating sequences, wherein each sequence comprises multiple elements on multiple antennas; - selectively correlating a plurality of repeating units in the plurality of repeating sequences according to the amplitude of the element, thereby estimating a phase offset of the plurality of repeating units; - performing phase compensation on the plurality of repeating units according to the estimated phase offset; - performing sequence merging on the plurality of repeating units; as well as - Perform sequence detection on the combined multiple repeat units.

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