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

(12) INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT) (19) World Intellectual Property Organization International Bureau (43) International Publication Date 16 July 2026 (16.07.2026) 1 11 111 111111E11 11111111111 1 1111 VIII Ell 1 11 III 11111 11111 11111 11111 11 1 11 1111 1111111 1111 1111 11 11 (10) International Publication Number WO 2026 / 148675 Al WIPO I PCT (51) International Patent Classification: HO4L 27 / 00 (2006.01) (21) International Application Number. PCT / CN2025 / 072361 (22) International Filing Date: 14 January 2025 (14.01.2025) (25) Filing Language: English (26) Publication Language: English (30) Priority Data: 19 / 013,436 08 January 2025 (08.01.2025) US (71) Applicant: HONG KONG APPLIED SCIENCE AND TECHNOLOGY RESEARCH INSTITUTE COMPA- NY LIMITED [CN / CNI; 5 / F, Photonics Centre, 2 Science Park East Avenue, Hong Kong Science Park, Shad'', N.T., Hong Kong (CN). (72) Inventors: LUO, Yarning; Rm 05, Floor 23, Block 0, Amoy Gardens, No. 77, Ngau TauKok Road, Kwan Tong, Kowloon, Hong Kong (CN). WEI, Tingling; Room A, Floor 27, JinLaiGe, JinSeDuHui, Luohu District, Shenzhen, Guangdong 518000 (CN). ZHANG, Yuxian; Flat C, 6 / F, Tower 3A, Mayfair By The Sea 8, 1 Fo Yin Road, Tai Po, NT, Hong Kong (CN). CHRJ, Eddy; Flat A, 26 / F, Tower 1, Manhattan Hill, 1 Po Lun Street, Lai Chi Kok, Kowloon, Hong Kong (CN). (74) Agent: CHINA TRUER IP; Room 1104, Building 2, Excellence Meilin Central Plaza (North Area), No. 128 Zhongkang Road, Meidu Community, Meilin Street, Futian District, Shenzhen, Guangdong 518049 (CN). (81) Designated States (unless otherwise indicated, for every kind of national protection available): AE, AG, AL, AM, AO, AT, AU, AZ, BA, BB, BG, BH, BN, BR, BW, BY, BZ, CA, CH, CL, CN, CO, CR, CU, CV, CZ, DE, DJ, DK, DM, DO, DZ, EC, EE, EG, ES, FI, GB, GD, GE, GH, GM, GT, HN, HR, HU, ID, IL, IN, IQ, IR, IS, IT, JM, JO, JP, KE, KG, KH, KN, KP, KR, KW, KZ, LA, LC, LK, LR, LS, LU, LY, MA, MD, MG, MK, MN, MU, MW, MX, MY, MZ, NA, NG, NI,NO, NZ, OM, PA, PE, PG, PH, PL, PT, QA, RO, RS, RU, RW, SA, SC, SD, SE, SG, SK, SL, ST, SV, SY, TH, TJ, TM, TN, TR, TT, TZ, UA, UG, US, UY, UZ, VC, VN, WS, ZA, 7M, ZW. (84) Designated States (unless otherwise indicated, for every kind of regional protection available): ARIPO (BW, CV, GH, GM, KE, LR, LS, MW, MZ, NA, RW, SC, SD, SL, ST, SZ, TZ, UG, ZM, ZW), Eurasian (AM, AZ, BY, KG, KZ, RU, TJ, TM), European (AL, AT, BE, BG, CH, CY, CZ, DE, DK, EE, ES, FI, FR, GB, GR, HR, HU, IE, IS, IT, LT, -=••-- (54) Title: METHOD AND APPARATUS FOR PHASE OFFSET ESTIMATION AND COMPENSATION FOR PRACH WITH LARGE FREQUENCY OFFSET 400 (57) Abstract: The embodiments herein relate to method and ap- paratus for phase offset estimation and compensation for Physical Random Access Channel (PRACH) with large frequency offset. In some embodiments, there proposes a method for Physical Ran- dom Access Channel (PRACH) preamble detection. The method may comprise the steps ofreceiving a PRACH preamble with a pluralityofrepeated sequences, in which each sequence includes a plurality of elements on a plurality of antennas; performing a phase offset estimation for multiple repetitions within the plural- ity of repeated sequences, by selectively correlating the multiple repetitions based on magnitudes of the elements; perforating a phase compensation for the multiple repetitions, based on the es- timated phase offset; perforating a sequence combination for the multiple repetitions; and performing a sequence detection on the combined multiple repetitions. Start Downsarnpling \-"110 Serial-to-parallel \ `120 \--"42 I 422 1 Phase offset estimation Phase offset compensation Sequence combination W O 20 26 / 1 48 67 5 A l Correlation Antenna Combination Detection Figure 4 [Continued on next page] WO 2026 / 148675 Al I 11111 11111111 1111111111111 1111111111 1111 I II III 1111111111 1111111111 II III 1111 11111111111 1111 1111 LU, LV, MC, ME, MK, MT, NL, NO, PL, PT, RO, RS, SE, SI, SK, SM, TR), OAPI (BF, BJ, CF,CG, CI, CM, GA, GN, GQ, GW, KM, ML, MR, NE, SN, TD, TG). Published: — with international search report (Art. 21(3)) WO 2026 / 148675 PCT / CN2025 / 072361 METHOD AND APPARATUS FOR PHASE OFFSET ESTIMATION AND COMPENSATION FOR PRACH WITH LARGE FREQUENCY OFFSET Technical Field 5 The embodiments herein relate generally to the field of communication, and more particularly, the embodiments herein relate to method and apparatus for phase offset estimation and compensation for Physical Random Access Channel (PRACH) with large frequency offset. Background 10 PRACH preamble is a special sequence used in wireless communication systems for synchronizing and identifying. 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. PRACH preamble normally has multiple repeated sequences, so as to improve the 15 coverage and anti-interference capability and to support beam sweeping. For example, informat B4 (short sequence), there are 12 repeated sequences, and in format 3 (long sequence), there are 4 repeated sequences. For example, a Zadoff-Chu (ZC) sequence with the symbol length of 139, 839, 569, or 1149 may be used as a PRACH sequence. 20 Figure 1 shows an example decoding method 100 for PRACH preamble. The signal may be received on multiple antennas, and the received signal on each antenna may include multiple sequences for example 12 sequences, each sequence may include multiple symbols. In the example method 100 of Figure 1, downsampling step 110, serial-to-parallel conversion step 120, correlation step 130, signal combination step 140 may be performed on the received signal in 25 this order. Signal combination step 140 may include sequence combination and antenna combination. Then, detection step 150 may be performed on the combined sequences, by compared with the local sequence(s) to determine the matched sequence. That is, in the method 100 of Figure 1, the sequencesin the received signal are correlated at step 130 and then combined at step 140. Since the received signal has multiple sequences (for 30 example 12 sequences), it is not complex and will cause huge complexity, no matter performed in time or frequency domain, for correlating all the 12 sequences. Thus, an improved approach is performing the sequence combining before correlation, as shown in Figure 2. Figure 2 shows another example decoding method 200 for PRACH preamble. In Figure 2, 35 compared with Figure 1, there is an additional sequence combination step 225 between the serial-to-parallel conversion step 120 and the correlation step 130. In step 225, for example all 12 1 WO 2026 / 148675 PCT / CN2025 / 072361 sequences may be combined as one sequence, so that the complexity at the correlation step 130 may be reduced. Then, in step 240, the antenna combination may be performed. The method 200 in Figure 2 may improve the PRACH preamble decoding and detection by reducing the complexity.However, there still may be some problem. 5 In a Non-Terrestrial Network (NTN), the mismatch of Carrier Frequency Offset (CFO) between transmitter and receiver may larger than the terrestrial network, due to high mobility. For example, in an NTN network relayed by satellite (or be referred as satellite network), due to the high mobility of satellites (especially Low Earth Orbit satellite), the Doppler frequency shifting will cause the mismatch of CFO between transmitter and receiver. Similar problem may 10 exist for the mobile network related to the High-speed train (HST), which is considered as one of the essential verticals in 5G applications, very large CFO exists due to the rapid moving of the train as well as the mobile devices on the train. Prior information about the satellite orbits or train cannot efficiently mitigate the influence of CFO, and there still exist non-negligible residual CFO after CFO pre-compensation. 15 At the transmitter side, the sequences originally conveysame signal, but if large CFO exists, at the receiver side, different sequences will have different phase offsets. 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) may be considered to be phase aligned, but the following sequences may have phase offsets caused by the CFO. The phase offset may be accumulated on 20 time, that is each symbol may have larger phase offset than the previous symbol. The slope of the phase offsets may be the CFO. That is, sequence 1 may have the phase offset of AO, sequence 2 may have the phase offset of 26.4130, and so on. The phase offset may be harmful on the sequence combination introduced in step 225 of Figure 2, since the sequences or symbols will cancel each other, if the phase offset between them is 180 degrees (or a). As a result, the 25 detection performance may be poor. The patent publication CN108040366A proposes a random access preamble signaldetection method based on frequency offset correction. The method comprises the steps of: calculating available time-frequency resources, generating 64 preamble sequences, and randomly 30 selecting a preamble sequence as a sending preamble sequence; finding out a sub-frame, which is a PRACH time-domain sub-frame currently; according to related parameters, estimating a Doppler frequency offset value through a maximum likelihood (ML) criterion as frequency offset compensation; performing cyclic prefix elimination, down-sampling filtering and Fourier transformation on processed signals; performing frequency domain correlation of the preamble 35 sequences and local ZC root sequences; and, performing inverse fast Fourier transformation, modular square and multi-antenna combination on frequency domain correlation sequences, 2 WO 2026 / 148675 PCT / CN2025 / 072361 calculating a power delay spectrum energy (PDP), and comparing the power delay spectrum energy (PDP) with detection thresholds A and B,so that a preamble serial number ID and the time advance (TA) are obtained. However, the CFO before downsampling approach in CN108040366A may be directly processing the undownsampled signal is more difficult to 5 implement, and storing the undownsampled signal will increase saving overhead. Problems particularly for CN108040366A may be that it assumes known time offset and it depends on the accuracy of the Signal Noise Ratio (SNR) estimation. The patent publication CN112887241A proposes a frequency offset estimation method 10 and device, a communication device and a storage medium, the method comprising: when it is detected that there is an access signal in a PRACH signal sent by a signal sending end, obtaining a main peak and an auxiliary peak of the PRACH signal, the PRACH signal being composed of a preset number of identical pilot sequences; determining a first frequency offset according to the peak value of the main peak and the peak value of the secondary peak; performingfrequency 15 offset compensation on the PRACH signal according to the first frequency offset to obtain a compensation sequence after frequency offset compensation; and calculating a frequency offset between the compensation sequence and the pilot sequence to obtain a second frequency offset, and performing time delay estimation on the access signal according to the second frequency offset. The patent publications US9491024B2, W02010040264A1, W02013172748A1 20 (US20150139098A1) propose CFO after correlation approach similar to the CN112887241A. However, the CFO after correlation approach in CN112887241A cannot be used for the considered scenario in which the phase offset is estimated before correlation, but the peaks can only be obtained after the correlation. Problems particularly for CN112887241A may be that: PRACH format is modified, thus not suitable for PRACH format specified by 3rd Generation 25 Partnership Project (3GPP) and it may have high complexity. Summary As seen, for PRACHreception in large CFO cases, if combining sequence after correlation (Figure 1), there may be huge complexity; and if combining sequence before correlation (Figure 30 2), there may be poor detection performance. Thus, it is an objective to propose a new algorithm with CFO estimation / compensation before the early combination, and has good balance of complexity and detection performance. In view of the above, the embodiments herein propose method and apparatus for phase offset estimation and compensation for Physical Random Access Channel (PRACH) with large 35 frequency offset. In some embodiments, there proposes a method for PRACH preamble detection. The 3 WO 2026 / 148675 PCT / CN2025 / 072361 method may comprise at least the steps of receiving a PRACH preamble with a plurality of repeated sequences, in which each sequence includes a plurality of elements on a plurality of antennas; performing a phase offset estimation for multiple repetitions within the plurality of repeated sequences, byselectively correlating the multiple repetitions based on 5 magnitudes of the elements; performing a phase compensation for the multiple repetitions, based on the estimated phase offset; performing a sequence combination for the multiple repetitions; and performing a sequence detection on the combined multiple repetitions. In some embodiments, there proposes a PRACH receiver in a wireless communication system, the PRACH receiver may comprise a memory storing machine-readable 10 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 with a plurality of repeated sequences, in which each sequence includes a plurality of elements on a plurality of antennas; perform a phase offset estimation for multiple repetitions within the plurality of repeated sequences, by selectively 15 correlating the multiple repetitions based on magnitudes of theelements; perform a phase compensation for the multiple repetitions, based on the estimated phase offset; perform a sequence combination for the multiple repetitions; and perform a sequence detection on the combined multiple repetitions. In some embodiments, there proposes a computer readable product comprising computer 20 readable code, which when run on an apparatus, causes the apparatus to perform the above method. The embodiments may propose a new algorithm with CFO estimation / compensation before the early combination, and has good balance of complexity and detection performances. For example, the embodiments may have low missed detection rate (MDR), MDR means that the 25 PRACH is transmitted, but not detected (i.e., missing detection); the embodiments may also have low false alarm rate (FAR), FAR means that no PRACH is transmitted, but receiver falsely detects a PRACH (i.e., false alarm). Brief Description of the Drawings 30 The accompanying drawings, which are incorporated hereinand form part of the specification, illustrate various embodiments of the present disclosure and, together with the description, further serve to explain the principles of the disclosure and to enable a person skilled in the pertinent art to make and use the embodiments disclosed herein. In the drawings, like reference numbers indicate identical or functionally similar elements, and in which: 35 Figure 1 shows an example decoding method for PRACH preamble; Figure 2 shows another example decoding method for PRACH preamble; 4 WO 2026 / 148675 PCT / CN2025 / 072361 Figure 3 shows the phase offsets of different sequences of the received signal; Figure 4 shows an example decoding method for PRACH preamble, according to the embodiments herein; Figure 5 shows the magnitude variation in the undownsampled signal; 5 Figure 6 shows an example phase offset estimation approach, according to the embodiments herein; Figure 7 shows an example phase offset compensation approach, according to the embodimentsherein; Figure 8 shows an example PRACH receiver, according to the embodiments herein; and 10 Figure 9 shows an example computer-implemented apparatus, according to the embodiments herein. Detailed Description of Embodiments Embodiments herein will be described in detail hereinafter with reference to the 15 accompanying drawings, in which embodiments are shown. These embodiments herein may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. The elements of the drawings are not necessarily to scale relative to each other. Reference to "one embodiment" or "an embodiment" means that a particular feature, 20 structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrase "in an embodiment" appearing in various places throughout the specification are not necessarily all referring to the same embodiment. As used in the description andthe appended claims, the singular forms "a", "an" and 25 "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also 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. As used throughout this description, and in the claims, a list of items joined by the 30 term "at least one of" or "one or more of" can mean 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. Figure 4 shows an example decoding method for PRACH preamble, according to the 35 embodiments herein. In Figure 4, compared with Figure 2, the method 400 may further comprise a phase offset estimation step 421 and a phase offset compensation step 422. Note that, the phase 5 WO 2026 / 148675 PCT / CN2025 / 072361 offset estimation step 421 and a phase offset compensation step 422may be combined into a single phase offset estimation and compensation step. In the example method 400 of Figure 4, downsampling step 110, serial-to-parallel conversion step 120, the phase offset estimation step 421, a phase offset compensation step 422, 5 sequence combination step 225, correlation step 130, antenna combination step 240, and a detection step 150 may be performed on the received signal in this order. In an example, the method is implemented on a Non-Terrestrial Network (NTN) PRACH receiver, such as receiver of high-speed railway or satellite-based system. In an example, before the phase offset estimation step 421 and the phase offset 10 compensation step 422, there may be a pre-compensation step, in which the sequences (i.e., repetitions) may be pre-compensated in advance, based on satellite orbit information. Then the remaining (or residual) phase offset may be estimated and compensated at the phase offset estimation step 421 and the phase offset compensation step 422respectively. 15 The PRACH preamble signal may be received on multiple antennas, and the received signal on each antenna may include multiple sequences for example 12 sequences, each sequence may include multiple symbols. The multiple antennas may be denoted as i = 1, 2, ...,1, wherein I is the maximum number of antennas considered; 20 The multiple sequences may be denoted as s = 1, 2, ..., S, wherein S is the maximum number of sequences considered; The multiple symbols in each sequence may be sampled as multiple samples, which may be denoted as n = 1, 2, ..., N, wherein Nis the maximum number of samples considered. For example, a PRACH receiver may receive 12 sequences in total, the 12 sequences may 25 be repeated sequences. That is, they are the same at the transmitter side. In order to reduce the complexity of the calculation, for example, the proposed method may only consider 6 sequences. The considered 6 sequences may be also referred as "repetitions". In an example, the multiplesequences (i.e., sequences repetitions) used in the calculation may be all of the plurality of repeated sequences (for example all 12 sequences), or a part of the 30 plurality of repeated sequences (for example 6 sequences within the all 12 sequences). If viewing from the perspective of signal, the multiple sequences (i.e., sequences repetitions) used in the calculation may be all or a part of the received preamble signals on the plurality of antennas. Then, the received sequence may be denoted as y(s, n, 0; and the received sequence with a sequence separation may be denoted as y(s — m, n, i)' , wherein the sequence distance (or 35 sequence separation) between the sequence y(s — m, n, i)' and the sequence y(s, n, i) may be m = 1, 2, ..., S — 1. For example, the sequence distance (or sequence separation) between the 6 WO 2026 / 148675 PCT / CN2025 / 072361 sequence 10 and sequence 11 is 1. Based on the above denotation, one approach for estimate 0:1)(m) for a given sequence separation m maybe: 1 ZIO(m) = ;angle (1 y(s, n, i) * y(s — m, n, 0') s n 5 Equation (1) wherein the 001)(m) means the 0(1) (as shown in Figure 3) calculated by the sequence separation m, it does not mean that the estimated phase offset of the sequence m. In fact, the estimated phase offset of the sequence s = 1, 2, ..., S should be for example s * As shown in the Equation (1), the two sequences, i.e., the sequence y(s — m, n, 0' and the 10 sequence y(s, n, i) are correlated by using conjugate multiplication. Then, the correlation value is converted into angle to obtain phase offset for sequence separation m. Then, the phase offset for sequence separation m may be divided by m, to obtain the normalized phase offset bl)(m), i.e., phase offset of a single sequence separation (i.e., phase offset between two adjacent sequences). 15 In an example, performing the phase offset estimation includes calculating a phase of correlation of two repetitions, for a combination including the two repetitions, as shownin the calculation "angle 0" in equation (1). If Equation (1) is used for all possible value of m, i.e., for example m = 1, 2, ... S-1, the 20 final M may be: S — 1m S-1 S N A601) — 1 1 angle (I, =o y(s,n, * y(s — m,n, 0') • m=1 s=m n=0 Equation (2) As shown in the Equation (2), for each value of m, for example m = 1, 2, ... S-1, a combination of two sequences, i.e., the sequence y(s — m, n, i)' and the sequence y(s, n, i) are correlated by using conjugate multiplication. Then, each of the correlation value is converted 25 into angle to obtain phase offset for sequence separation m. Then, each of the phase offset for sequence separation m may be divided by m, to obtain the normalized phase offset A(I)(m), i.e., phase offset of a single sequence separation (i.e., phase offset between two adjacent sequences). Then, the m All)(m) may be averaged to form the final AO. Depending on whether m = 1, the two sequences in a combination may be adjacent 30 repetitions or non-adjacent repetitions.For adjacent repetitions, m = 1. Note that, the normalization and average may be seen as a single calculation, i.e., weighted average. That is, in the equation (2), the estimated phase offset is a weighted average of the 7 WO 2026 / 148675 PCT / CN2025 / 072361 phase of correlation of the two repetitions relative to a distance (i.e., sequence separation m) of the two repetitions, for all combinations used. In a specific example of the Equation (2), if there are 12 sequences. All of the possible * combinations of any two sequences are used, then there may be Ci 2 12 211 2 = = 66 combinations 5 of two sequences. In an example, all of the 66 possible combinations are used for the phase offset estimation in step 421 or only a part of the all 66 possible combinations are used for the phase offset estimation in step 421. In an example, in order to reduce the complexity, there may be a threshold for the 10 sequence separation m, i.e., combinations each including two repetitions with a sequenceseparation m (or sequence distance) less than or equal to a threshold are used for the phase offset estimation. For example, the threshold may be set as 6. As a result, the sequence 1 may be correlated with the sequence 7, but cannot be correlated with sequence 8. Then, only 51 combinations of 15 the all 66 possible combinations are used for the phase offset estimation in step 421. The complexity for using all 66 possible combinations of sequences (or repetitions) are too large. The embodiments may further propose correlating the multiple repetitions based on magnitudes of the elements, so as to reduce the complexity. Figure 5 shows the magnitude 20 variation in the undownsampled signal. As shown in Figure 5, there may be magnitude variation in the undownsampled signal, i.e., some of the samples may stronger than other samples. Here, the term "element" may mean the samples on antennas, for example 1024 samples on 4 antennas. The embodiments consider that the stronger samples may causethe samples correlation values, that is the larger correlation may be from the dominant elements. 25 In an example, the larger correlation value may be considered. For example, top k of the 51 combinations of the all 66 possible combinations, or top k of the all 66 possible combinations may be considered in the phase offset estimation in step 421. In an example, the top one of the 51 combinations of the all 66 possible combinations, or top one of the all 66 possible combinations may be considered in the phase offset estimation in 30 step 421, i.e., k = 1. Figure 6 shows an example phase offset estimation approach, according to the embodiments herein. In the Figure 6, the antenna dimension is not shown. As shown in the top portion of Figure 6, the horizontal axis is sample axis and the longitudinal axis is sequence axis. 35 As shown in Figure 6, there may be 4 sequences (4 repetitions), each sequence may include 8 samples. If there are 4 antennas, then each sequence may include 8 * 4 =32 samples, or be 8 WO 2026 / 148675 PCT / CN2025 / 072361 referred as 32 elements; and all 4 sequences include 128 elements. Note that, the shown sequence length in Figure 6 is only an example, each sequence may include more or less samples. For example, there may be 1024 samples in one sequence. Please note that, the shown samples for calculation is an example. For example, a part of 5 samples may be used for calculation. For example, there may be 1024 samples in one sequence, and only 128 of them with larger magnitudes are used for the calculation. In an example, for each of the 8 elements in a sequence shown in Figure 6, there may be 4 elements in a column of Figure 6. For example, for the sample 1 (element 1), which may be referred as "a specific position of the multiple repetitions", there are 4 elements in the first 10 column. For this "specific position of the multiple repetitions" (shown as a column in Figure 6), the dominating elements are selected. For position (n, i), (that is, aspecific sample n on a specific antenna i), the dominating elements sl , s2 may be denoted as sl(n, i), s2(n, i), (sl < s2) are with two largest abs(y(s, n, i))Vn, i. In an example, the dominating elements may have largest 15 magnitude, i.e., they are dominating elements in terms of magnitude. Note that, in this example, two dominating elements with the largest magnitudes are used for the correlation, that is the correlation is between one combination including two dominating elements. However, the examples do not limit to this. In another example, three dominating elements with the largest magnitudes are used for the correlation, that is there are three 20 correlations, each of them is between one combination including two of said three dominating elements. In an example, a plurality of elements located at a specific position of the multiple repetitions respectively are compared, to select two dominating elements in terms of magnitude from the plurality of elements. For example, thedominating elements in position 1 (first column 25 in Figure 6) may be located in sequence 1 and 4, the dominating elements in position 2 (second column in Figure 6) may be located in sequence 1 and 3, the dominating elements in position 3 (third column in Figure 6) may be located in sequence 1 and 2, the dominating elements in position 4 (fourth column in Figure 6) may be located in sequence 1 and 4, the dominating elements in position 5 (fifth column in Figure 6) may be located in sequence 2 and 4, the 30 dominating elements in position 6 (sixth column in Figure 6) may be located in sequence 1 and 3, the dominating elements in position 7 (seventh column in Figure 6) may be located in sequence 3 and 4, and the dominating elements in position 8 (eighth column in Figure 8) may be located in sequence 1 and 3. In an example, two repetitions in which the two dominating elements are located 35 respectively are correlated for the specific position. In order to correlate the dominatingelements, in an example, the distance (i.e., sequence separation m) between the dominating elements at 9 WO 2026 / 148675 PCT / CN2025 / 072361 each position may be calculated. For example, for position 1-8, m = {3, 2, 1, 3, 2, 2, 1, 2}. For each position (n, i), the sequence with same sequence separation m may be correlated. For example, as shown in bottom portion of Figure 6, for the positions 1 and 4 with m = 3, the sequence 1 may be correlated with sequence 4; for the positions 2, 5, 6 and 8 with m = 2, the 5 sequence 1 may be correlated with sequence 3, and the sequence 2 may be correlated with sequence 4; for the positions 3 and 7 with m = 1, the sequence 1 may be correlated with sequence 2, the sequence 2 may be correlated with sequence 3, and the sequence 2 may be correlated with sequence 4. That is, the equation (2) may become the following equation (3), in which the dominating 10 elements are correlated for each position. s-i Acl) = s 1 1 angle y(s2(n, i), n, i) * y (s 1(n, i), n,i)' m=1 (n,i)EG(m) where G (m) = {(n, i) with s2(n, i) — sl(n, i) == m} equation (3). In the example shown in Figure 6 and in equation (3), the obtained phase offset from the correlation may be weighted averaged, to obtain the final AO. Compared with the equation (1), for the equation (3), for each position within a sequence, 15 the correlation may be done for only one time, as a result, the equation (3) may be seen as only one correlation over the positions. As a result, the complexity of the phase offset estimation may be significantly decreased, especially for a sequence with large number of samples for example 1149 samples. By using the equation (3), the elements that are most influencing and noise resistant may be captured, at the same time, the complexity is reduce. 20 Note that, some further improvement for equation (1) or equation (2) may be also applicable for equation (3). For example, there may be a threshold the sequence separation m, i.e., combinations each including tworepetitions with a sequence separation m (or sequence distance) less than or equal to a threshold are used for the phase offset estimation. Depending on whether m = 1, the two sequences in a combination may be adjacent 25 repetitions or non-adjacent repetitions. For adjacent repetitions, m = 1. Figure 7 shows an example phase offset compensation approach, according to the embodiments herein. In the example of Figure 7, all elements within a repetition are compensated with a constant value based on the estimated phase offset AO. 30 For example, as shown in Figure 7, for the s -th sequence, update y(s, n, i) by: yupdate s 7.4 0 = y (s, n, * exp (j * ,6,(1) * (s — 1)) Equation (4) For example, in an example (Compensation Solution 1 in Figure 7), sequence 0 is considered as the first sequence, then for all symbols in the following sequence 1, the phase 10 WO 2026 / 148675 PCT / CN2025 / 072361 offset compensation is the same, i.e., Acto; for all symbols in the following sequence 2, the phaseoffset compensation is the same, i.e., 2 * Ac13, and so on. In addition, in an alternative approach (Compensation Solution 2 in Figure 7), the symbols in the same sequence may be compensated with different phase offsets, that is the first symbol is 5 compensated with a phase offset less than the last symbol, so that the phase offset compensation may be linear, as shown in Figure 7. In an example, if there are 256 symbols in a sequence, then each symbol may be compensated with a phase offset of 0cI3 / 256 more than the previous symbol. Comparing the two Compensation Solutions in Figure 7, the Compensation Solution 1 is 10 preferred, since the complexity is low, and the constant part of each sequence influencing performance most. In addition, the Compensation Solution 1 may also work for larger CFO, for example, AO may be greater than 360 degrees (or 2 n ), at this time, the Ac / 256 may be wrong, since the estimated Acl) may be actually Ail) — 2 71 . That is, although there is nodifferences for the correlation or sequence combination for AO and M — 2 n (they may be 15 seen as the same phase), but the 0c13 / 256 and (AO — 2 n ) / 256 may be totally different in phase. Note that, the above proposed features may be combined with each other, to further improve the balance of complexity and detection performance. 20 The performances may be compared for the different solutions, prior art solution (1) shown in Figure 1; prior art solution (2) shown in Figure 2; the proposed solution (3) by using equation (1) or (2) (making m = 1) and (4); the proposed solution (3) by using equation (3) or (4). The Missed detection rate (MDR) and false alarm rate (FAR) for FR2 B4 60kHz SCS 25 case from 3GPP standard are compared for the solution (1) to (4), the following table 1 may be obtained. Table 1: Simulated performances of solutions Solutions Missed detection rates at SNR -6.9dB False alarm rate (including extra error) at SNR -6.9dB solution (1) 0.22% 5.42% solution (2) 29.98%0.06% solution (3) 3.14% 0% solution (4) 0.3% 0% As may be seen from table 1, the proposed solutions, especially the solution (4) proposed may satisfy the 3GPP requirement on miss detection rate in large CFO and may 11 WO 2026 / 148675 PCT / CN2025 / 072361 achieve much better MDR and FAR performances than the prior art solutions. Complexity of solution (1) of Figure 1, in which combining is after correlation may be presented in the following tables (in the unit of operations). For short sequence, it is assumed that there are 12 sequence, each with 256 symbols, and for long sequence, it is 5 assumed that there are 4 sequence, each with 1024 symbols. Table 2: Simulated complexity of prior art solution (1) for short sequence For short sequence Per calling Number of calling Subtotal FFT 256*10g2(256) 2*12 49152 Multiplication 256 2*12*64 393216 IFFT 256*10g2(256) 2*12*64 3145728 Power 256 2*12*64 393216 Combining antenna / sequence 2*12 256*64 393216 Total 4374528 Table 3: Simulated complexity ofprior art solution (1) for long sequence For long sequence Per calling Number of calling Subtotal FFT 1024*10g2(1024) 2*4 81920 Multiplication 1024 2*4*64 1048576 IFFT 2048*log2(2048) 2*4*64 11534336 Power 2048 2*4*64 1048576 Combining antenna / sequence 2*4 2048*64 1048576 Total 14761984 10 Then, for the short sequence and long sequence, the proposed solution (4) may significantly reduce the complexity, for example as shown in the following tables. Table 4: Simulated complexity of proposed solution (4) for short sequence For short sequence Per calling Number of calling Subtotal Find dominating elements 2*256*11*2 11264 Phase estimation 2*256*2+11*3 1057 Compensation 256 11*2 5632 Combining sequence 12 256*2 6144 FFT 256*log2(256) 2 4096 12 WO 2026 / 148675 PCT / CN2025 / 072361 Multiplication 256 2*64 32768 IFFT 256*10g2(256) 2*64 262144 Power 256 2*64 32768 Combining antenna 2 256*64 32768 Total 388641 Table 5: Simulated complexity of proposed solution (4) for long sequence For long sequencePer calling Number of calling Subtotal Find dominating elements 2*1024*3*2 12288 Phase estimation 2*1024*2+3*3 4105 Compensation 1024 3*2 6144 Combining sequence 4 1024*2 8192 FFT 1024*log2(1024) 2 20480 Multiplication 2048 2*64 262144 IFFT 2048*10g2(2048) 2*64 2883584 Power 2048 2*64 262144 Combining antenna 2 2048*64 262144 Total 3721225 By comparing with the solutions (1) and (4) in terms of complexity, the proposed solution (4) may reduce the complexity by 11.26 times for the short sequence and by 3.97 5 times for the long sequence. Note that, compared with solutions (2) or (3) (which is substantially same in terms of complexity), the proposed solution may increase the complexity slightly by 6.6% and less than 8.3% for short and long sequences respectively. 10 Figure 8 shows an example PRACH receiver 800, according to the embodiments herein. In an embodiment, the example PRACH receiver 800 in Figure 8 may be configure to perform the above method 400. In an embodiment, the PRACHreceiver 800 may comprise a processor 801; and a memory 802 coupled to the processor 801. The memory 802 may store instructions executable by the 15 processor 801. When the processor 801 executes the instructions, the processor 801 may be configured to perform the above method 400. Note that, the PRACH receiver 800 may be implemented as hardware, software, firmware and any combination thereof. For example, the PRACH receiver 800 may include a plurality of units, circuities, modules or the like, each of which may be used to perform one or more steps of 13 WO 2026 / 148675 PCT / CN2025 / 072361 the example method 400. In an embodiment, the PRACH receiver 800 may 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., radio access points), base stations (BSs) (e.g., radio base stations, Node 5 Bs, evolved Node Bs (eNBs) and NR NodeBs (gNBs)), 0-RAN nodes or components of an 0-RAN node (e.g., 0-RU,0-DU, 0-CU). Figure 9 shows an example computer-implemented apparatus 900, according to the embodiments herein. In an embodiment, the apparatus 900 may be configured as the above 10 PRACH receiver as shown in Figure 8. In an embodiment, the apparatus 900 may include but not limited to at least one processor such as Central Processing Unit (CPU) 901, a computer-readable medium 902, and a memory 903. The memory 903 may comprise a volatile (e.g., Random Access Memory, RAM) and / or non-volatile memory (e.g., a hard disk or flash memory). In an embodiment, the 15 computer-readable medium 902 may be configured to store a computer program and / or instructions, which, when executed by the processor 901, causes the processor 901 to carry out any of the above mentioned methods 400. In an embodiment, the computer-readable medium 902 (such as non-transitory computer readable medium) may be stored in the memory 903. In another embodiment, the computer 20 program may be stored in a remote location forexample computer program product 904 (also may be embodied as computer-readable medium), and accessible by the processor 901 via for example carrier 905. The computer-readable medium 902 and / or the computer program product 904 may be distributed and / or stored on a removable computer-readable medium, e.g. diskette, CD (Compact 25 Disk), DVD (Digital Video Disk), flash or similar removable memory media (e.g. compact flash, SD (secure digital), memory stick, mini SD card, MMC multimedia card, smart media), HD-DVD (High Definition DVD), or Blu-ray DVD, USB (Universal Serial Bus) based removable memory media, magnetic tape media, optical storage media, magneto-optical media, bubble memory, or distributed as a propagated signal via a network (e.g. Ethernet, ATM, ISDN, 30 PSTN, X.25, Internet, Local Area Network (LAN), or similar networks capable of transporting data packets to the infrastructure node). The disclosure further proposes the following examples. Example 1. A method for PhysicalRandom Access Channel (PRACH) preamble detection, 35 comprising: - receiving a PRACH preamble with a plurality of repeated sequences, in which each 14 WO 2026 / 148675 PCT / CN2025 / 072361 sequence includes a plurality of elements on a plurality of antennas; - performing a phase offset estimation for multiple repetitions within the plurality of repeated sequences, by selectively correlating the multiple repetitions based on magnitudes of the elements; 5 - performing a phase compensation for the multiple repetitions, based on the estimated phase offset; - performing a sequence combination for the multiple repetitions; and - performing a sequence detection on the combined multiple repetitions. Example 2. The method according to claim 1, 10 wherein a plurality of elements located at a specific position of the multiple repetitions respectively are compared, to select two dominating elements in terms of magnitude from the plurality of elements; and wherein two repetitions in which the twodominating elements are located respectively are correlated for the specific position. 15 Example 3. The method according to claim 2, wherein the two repetitions are non-adjacent repetitions. Example 4. The method according to example 1, wherein the multiple repetitions are all or a part of the plurality of repeated sequences, or are all or a part of the received preamble signals on the plurality of antennas. 20 Example 5. The method according to example 2, wherein all or a part of possible combinations of any two repetitions of the multiple repetitions are used for the phase offset estimation, or combinations each including two repetitions with a distance less than or equal to a threshold are used for the phase offset estimation. Example 6. The method according to example 5, wherein performing the phase offset 25 estimation includes calculating a phase of correlation of two repetitions, for a combinations including the two repetitions. Example 7. The method according to example 6,wherein the estimated phase offset is a weighted average of the phase of correlation of the two repetitions relative to a distance of the two repetitions, for all combinations used. 30 Example 8. The method according to example 1, wherein all possible combinations of any two repetitions of the multiple repetitions are correlated for a specific position of the multiple repetitions, to select k combinations with top k correlation values; wherein the k correlation values are used for the phase offset estimation. Example 9. The method according to example 1, wherein in the phase compensation, all 35 elements within a repetition are compensated with a constant value based on the estimated phase offset. 15 WO 2026 / 148675 PCT / CN2025 / 072361 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 comprising: - performing a pre-compensation for the multiple repetitions based on satelliteorbit 5 information, before performing the phase offset estimation. 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 10 executes the machine-readable instructions, it configures the PRACH receiver to: - receive a PRACH preamble with a plurality of repeated sequences, in which each sequence includes a plurality of elements on a plurality of antennas; - perform a phase offset estimation for multiple repetitions within the plurality of repeated sequences, by selectively correlating the multiple repetitions based on magnitudes of the 15 elements; - perform a phase compensation for the multiple repetitions, based on the estimated phase offset; - perform a sequence combination for the multiple repetitions; and - perform a sequence detection on the combined multiple repetitions. 20 Example 12. The PRACHreceiver according to example 11, wherein a plurality of elements located at a specific position of the multiple repetitions respectively are compared, to select two dominating elements in terms of magnitude from the plurality of elements; and wherein two repetitions in which the two dominating elements are located respectively are 25 correlated for the specific position. Example 13. The PRACH receiver according to example 12, wherein the two repetitions are non-adjacent repetitions. Example 14. The PRACH receiver according to example 11, wherein the multiple repetitions are all or a part of the plurality of repeated sequences, or are all or a part of the 30 received preamble signals on the plurality of antennas. Example 15. The PRACH receiver according to example 12, wherein all or a part of possible combinations of any two repetitions of the multiple repetitions are used for the phase offset estimation, or combinations each including two repetitions with a distance less than or equalto a threshold are used for the phase offset estimation. 35 Example 16. The PRACH receiver according to example 15, wherein performing the phase offset estimation includes calculating a phase of correlation of two repetitions, for a 16 WO 2026 / 148675 PCT / CN2025 / 072361 combinations including the two repetitions. Example 17. The PRACH receiver according to example 16, wherein the estimated phase offset is a weighted average of the phase of correlation of the two repetitions relative to a distance of the two repetitions, for all combinations used. 5 Example 18. The PRACH receiver according to example 11, wherein all possible combinations of any two repetitions of the multiple repetitions are correlated for a specific position of the multiple repetitions, to select k combinations with top k correlation values; wherein the k correlation values are used for the phase offset estimation. Example 19. The PRACH receiver according to example 11, wherein in the phase 10 compensation, all elementswithin a repetition are compensated with a constant value based on the estimated phase offset. Example 20. A computer readable product comprising computer readable code, which when run on an apparatus, causes the apparatus to perform any one of the above methods. It will be recognized that principles of the disclosure are not limited to the 15 embodiments so described, but instead can be practiced with modification and alteration without departing from the scope of the appended claims. The above embodiments may include the undertaking only a subset of such features, undertaking a different order of such features, undertaking a different combination of such features, and / or undertaking additional features than those features explicitly listed. The scope of the embodiments 20 should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. 17 WO 2026 / 148675 PCT / CN2025 / 072361 CLAIMS What is claimed is: 5 1.A method for Physical Random Access Channel (PRACH) preamble detection, comprising: - receiving a PRACH preamble with a plurality of repeated sequences, in which each sequence includes a plurality of elements on a plurality of antennas; - performing a phase offset estimation for multiple repetitions within the plurality of 10 repeated sequences, by selectively correlating the multiple repetitions based on magnitudes of the elements; - performing a phase compensation for the multiple repetitions, based on the estimated phase offset; - performing a sequence combination for the multiple repetitions; and 15 - performing a sequence detection on the combined multiple repetitions. 2. The method according to claim 1, wherein a plurality of elements located at a specific position of the multiple repetitions respectively are compared, to select two dominating elements in terms of magnitude from the 20 plurality of elements; and wherein two repetitions in which the two dominating elements arelocated respectively are correlated for the specific position. 3. The method according to claim 2, wherein the two repetitions are non-adjacent 25 repetitions. 4. The method according to claim 1, wherein the multiple repetitions are all or a part of the plurality of repeated sequences, or are all or a part of the received preamble signals on the plurality of antennas. 5. The method according to claim 2, wherein all or a part of possible combinations of any two repetitions of the multiple repetitions are used for the phase offset estimation, or combinations each including two repetitions with a distance less than or equal to a threshold are used for the phase offset estimation. 18 30 35 WO 2026 / 148675 PCT / CN2025 / 072361 6. The method according to claim 5, wherein performing the phase offset estimation includes calculating a phase of correlation of two repetitions, for a combinations including the two repetitions. 5 7. The method according to claim 6, wherein the estimated phase offset isa weighted average of the phase of correlation of the two repetitions relative to a distance of the two repetitions, for all combinations used. 8. The method according to claim 1, wherein all possible combinations of any two 10 repetitions of the multiple repetitions are correlated for a specific position of the multiple repetitions, to select k combinations with top k correlation values; wherein 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 15 within a repetition are compensated with a constant value based on the estimated phase offset. 10. The method according to claim 1, wherein the method is implemented on a Non-Terrestrial Network (NTN) PRACH receiver; and wherein the method further comprising: 20 - performing a pre-compensation for the multiple repetitions based on satellite orbit information, before performing the phase offset estimation. 11. A PRACH receiver in a wirelesscommunication system, the PRACH receiver comprising: 25 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, it configures the PRACH receiver to: - receive a PRACH preamble with a plurality of repeated sequences, in which each sequence includes a plurality of elements on a plurality of antennas; 30 - perform a phase offset estimation for multiple repetitions within the plurality of repeated sequences, by selectively correlating the multiple repetitions based on magnitudes of the elements; - perform a phase compensation for the multiple repetitions, based on the estimated phase offset; 35 - perform a sequence combination for the multiple repetitions; and 19 WO 2026 / 148675 PCT / CN2025 / 072361 - perform a sequence detection on the combined multiple repetitions. 12. The PRACH receiver according to claim 11, wherein a plurality of elements located at a specificposition of the multiple repetitions 5 respectively are compared, to select two dominating elements in terms of magnitude from the plurality of elements; and wherein two repetitions in which the two dominating elements are located respectively are correlated for the specific position. 10 13. The PRACH receiver according to claim 12, wherein the two repetitions are non-adjacent repetitions. 14. The PRACH receiver according to claim 11, wherein the multiple repetitions are all or a part of the plurality of repeated sequences, or are all or a part of the received preamble 15 signals on the plurality of antennas. 15. The PRACH receiver according to claim 12, wherein all or a part of possible combinations of any two repetitions of the multiple repetitions are used for the phase offset estimation, or combinations each including two repetitions with a distance less than or equal to 20 a threshold are used for the phase offset estimation. 16. The PRACH receiver according to claim 15, whereinperforming the phase offset estimation includes calculating a phase of correlation of two repetitions, for a combinations including the two repetitions. 25 17. The PRACH receiver according to claim 16, wherein the estimated phase offset is a weighted average of the phase of correlation of the two repetitions relative to a distance of the two repetitions, for all combinations used. 30 18. The PRACH receiver according to claim 11, wherein all possible combinations of any two repetitions of the multiple repetitions are correlated for a specific position of the multiple repetitions, to select k combinations with top k correlation values; wherein the k correlation values are used for the phase offset estimation. 35 19. The PRACH receiver according to claim 11, wherein in the phase compensation, all 20 WO 2026 / 148675 PCT / CN2025 / 072361 elements within a repetition are compensated with a constant value based on the estimated phase offset. 20. A computer readable product comprising computerreadable code, which when run 5 on an apparatus, causes the apparatus to: - receive a PRACH preamble with a plurality of repeated sequences, in which each sequence includes a plurality of elements on a plurality of antennas; - perform a phase offset estimation for multiple repetitions within the plurality of repeated sequences, by selectively correlating the multiple repetitions based on magnitudes of 10 the elements; - perform a phase compensation for the multiple repetitions, based on the estimated phase offset; - perform a sequence combination for the multiple repetitions; and - perform a sequence detection on the combined multiple repetitions. 15 21 WO 2026 / 148675 PCT / CN2025 / 072361 100 Start Downsampling \-"120 v Serial-to-parallel • V • \--N130 Correlation Correlation Correlation v v v \-"140 \-'-`150 Combination Detection Figure 1 (Prior Art) 1 / 8 110 \-^ 120 \-'225 \-^130 \-"240 \-^150 v Detection v Correlation • Antenna Combination • Serial-to-parallel • Sequence combination vDownsampling Start WO 2026 / 148675 PCT / CN2025 / 072361 200 Figure 2 (Prior Art) 2 / 8 Seq 1 Seq 3 Seq 2 Seq 0 Phase offset caused by CTO • Continuously ac4umulated phase offset (slope is CFO) 3M WO 2026 / 148675 PCT / CN2025 / 072361 Time Figure 3 (Prior Art) 3 / 8 422 ^225 130 \-^ 240 \-^ 150 • Detection • Correlation • Phase offset estimation • Phase offset compensation • Sequence combination • Serial-to-parallel Start • Downsampling • Antenna Combination 400 \ WO 2026 / 148675 PCT / CN2025 / 072361 Figure 4 4 / 8 3 2.5 2 = c 1.5 ti 0.5 Magnitude variation in the undownsampled signal X 14297 Y 2 / 706 X6 1.2635 X 2009 Y 0.59816 X 10201 Y 0.40589 X 18393 y 0.28626 0 WO 2026 / 148675 PCT / CN2025 / 072361 0 2 3 4 5 Sample idx Figure 5 5 / 8 I till *4** 4, *4** **4* Ig .M1•1•••••••••••• .1.11 11.11.11 11110 IlleilM400111.1441114 MIA i,11 11, 41,11. 11• 11.11 114 1.101 140 ii111.1.1111.10110 01M101401101.11.111111.1111.11.11 I 1111 101 110 11.11. 111 11•1 141101110 0.11.11011 11.11 1 14101.00•11W1 41110101 1.111•11oli 4 * *4 ** *4 *** 4*** 4** 104,0410 / 40 / 14••••• 4...614.00146,1. 411.11 1101. 1.11.141 1110 11.11010101,11,11,11•111144.10 eiliii1461•1,1*Wym MOW. •101 1.1.111.11.1110101•11114 .1.1.1.1.11.161161.1.1. m= 1 '*** ***• MMIIMMERIVIE WO 2026 / 148675 PCT / CN2025 / 072361 S ampl e - m = 3 MEM 11•111111 MIIMM 111111111111M • 1111111 III §R 1111 MIMI M111111111MININ 111 1111E1111 11111 (13(3) IIIIMINIM111111 IMMEI • 1111111M 10110 • §A IMMMIN1111111 MEIN! IN 11001M 111 111 • 01 111 m= 2 Figure 6 6 / 8 Weighted 'average over m ite WO 2026 / 148675 PCT / CN2025 / 072361 Seq 0 Seql ... Seq11 Phase offset caused by CFO • Compensation Solution 2 ' Compensatio4 Solution 1 Time Figure 7 7 / 8 Memory The PRACH receiver Processor `̂ 801 802 carrier .M1 CPU Iv...• 901 Computer ‘.N readable medium 902 memory 4- - - L„ 903 Computer program product - r - - - -- 1 1 WO 2026 / 148675 PCT / CN2025 / 072361 800 \ Figure 8 900 \ Figure 9 8 / 8 904 905 INTERNATIONAL SEARCH REPORT International application No. PCT / CN2025 / 072361A. CLASSIFICATION OF SUBJECT MATTER HO4L 27 / 00(2006.01)i According to International Patent Classification (IPC) or to both national classification and IPC B. FIELDS SEARCHED Minimum documentation searched (classification system followed by classification symbols) IPC: HO4L Documentation searched other than minimum documentation to the extent that such documents are included in the fields searched Electronic data base consulted during the international search (name of data base and, where practicable, search terms used) CNTXT,VEN,ENTXT,ENTXTC,3GPP,CJFD,IF.FE: prach, repetition, combination, compensation, magnitude, sequence, phase, offset, estimation C. DOCUMENTS CONSIDERED TO BE RELEVANT Category* Citation of document, with indication, where appropriate, of the relevant passages Relevant to claim No. Y Y A US 2020187139 Al (SAMSUNG ELECTRONICS CO., LTD.) 11 June 2020 (2020-06-11) description, paragraphs

[0002] -

[0110] CN 118984499 A (HUAWEI TECHNOLOGIES CO., LTD.) 19 November 2024(2024-11-19) description, paragraphs

[0026] -

[0027] US 2022376883 Al (CHENGDU CORESAT TECH CO., LTD. et al.) 24 November 2022 (2022-11-24) the whole document 1-20 1-20 1-20 Further documents are listed in the continuation of Box C. annex. / See patent family * Special categories of cited documents: "'p' later document published after the international filing date or priority "A" document defining the general state of the art which is not considered date and not in conflict with the application but cited to understand the to be of particular relevance principle or theory underlying the invention "1)" document cited by the applicant in the international application "X" document of particular relevance; the claimed invention cannot be "E" earlier application or patent but published on or after the international considered novel or cannot be considered to involve an inventive step filing date when the document is taken alone "L" document which may throw doubts on priority claim(s) or whichis "y" document of particular relevance; the claimed invention cannot be cited to establish the publication date of another citation or other considered to involve an inventive step when the document is special reason (as specified) combined with one or more other such documents, such combination "0" document referring to an oral disclosure, use, exhibition or other being obvious to a person skilled in the art means "&" document member of the same patent family "P" document published prior to the international filing date but later than the priority date claimed Date of the actual completion of the international search 28 September 2025 Date of mailing of the international search report 28 September 2025 Name and mailing address of the ISA / CN CHINA NATIONAL INTELLECTUAL PROPERTY ADMINISTRATION 6, Xitucheng Rd., Jimen Bridge, Haidian District, Beijing 100088, China Authorized officer LI,XiaoQian Telephone No. (+86) 010-62089456 Form PCT / ISA / 210 (second sheet) (July 2022) INTERNATIONALSEARCH REPORT Information on patent family members International application No. PCT / CN2025 / 072361 Patent document cited in search report Publication date (day / month / year) Patent family member(s) Publication date (day / month / year) US 2020187139 Al 11 .Tune 2020 US 11350377 B2 31 May 2022 WO 2018236107 Al 27 December 2018 KR 20180138429 A 31 December 2018 KR 102312572 B 1 14 October 2021 CN 118984499 A 19 November 2024 None US 2022376883 Al 24 November 2022 US 11902409 B2 13 February 2024 SE 2250505 Al 30 October 2022 SE 545944 C2 19 March 2024 Form PCT / ISA / 210 (patent family annex) (July 2022) 4 (54) Title of Invention Method and Apparatus for Phase Offset Estimation and Compensation of PRACH with Large Frequency Offset (57) Abstract Embodiments Relate to a method and apparatus for phase offset estimation and compensation of Physical Random Access Channel (PRACH) with large frequency offset. In some embodiments, a method for detecting a Physical Random Access Channel (PRACH) preamble is proposed. The method may include the steps of: receiving a PRACH preamble having a plurality of repeating 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 repeating sequences according to the amplitude of the elements, thereby estimating the 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; and performing sequence detection on the merged plurality of repeating units. (19) State Intellectual Property Office (12) Invention Patent Application (10) Application Publication Number CN 120077616 A (43) Application Publication Date 2025.05.30 (21) Application Number202580000213.0 (22) Application Date 2025.01.14 (30) Priority Data 19 / 013,436 2025.01.08 US (51) Int.CI. H04L 27 / 00 (2006.01) H04L 5 / 00 (2006.01) H04W 74 / 0833 (2024.01) (85) PCT International Application Entering National Phase Date 2025.02.26 (86) PCT International Application Application Data PCT / CN2025 / 072361 2025.01.14 (71) Applicant: Hong Kong Applied Science and Technology Research Institute Limited Address: 5 / F, Optoelectronics Centre, 2 Science Park East, Sha Tin, New Territories, Hong Kong (72) Inventors: Luo Yaming, Wei Tingting, Zhang Yuxian, Zhao Yili (74) Patent Agency: Shenzhen Xinchuangyou Intellectual Property Agency Co., Ltd. 44223 Patent Attorney: Xie Linhong Claims: 2 pages Specification: 12 pages Drawings: 7 pages 9I9ZZ00ZI S CN 120077616 A Claims: 1 / 2^ 1. A method for detecting a Physical Random Access Channel (PRACH) preamble, comprising: - receiving a PRACH preamble having a plurality of repeating sequences, wherein each sequence comprises a plurality of elements on a plurality of antennas; - selectively correlating a plurality of repeating units in the plurality of repeating sequences according to the amplitude of the elements, thereby estimating the 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; and - performing sequence detection on the merged plurality of repeating units. 2. The method of claim 1, wherein multiple elements located at specific positions of the plurality of repeating units are compared, and two dominant elements that dominate in amplitude are selected from the plurality of elements; wherein, for the specific position, the two repeating units where the two dominant elements are located are correlated. 3. The method of claim 2, wherein the two repeating units are non-adjacent repeating units. 4. The method of claim 1, wherein the plurality of repeating units are all or part of the plurality of repeating sequences, or all or part of the preamble signals received on the plurality of antennas. 5. The method of claim 2, wherein all or part of any two repeating units in the plurality of repeating units may be combined for the phase offset estimation, or, combining two repeating units with a distance less than or equal to a threshold is used for the phase offset estimation. 6. The method of claim 5, wherein performing the phase offset estimation includes: for a combination including the two repeating units, calculating the correlated phase of the two repeating units. 7.8. The method of claim 6, wherein for all used merges, the estimated phase offset is a weighted average of the correlated phases of the two repeating units relative to the distance between the two repeating units. 9. The method of claim 1, wherein for a specific location among the plurality of repeating units, all possible merges of any two repeating units are correlated to select k merges with the highest k correlation values; wherein the k correlation values ​​are used for the phase offset estimation. 10. The method of claim 1, wherein in the phase compensation, all elements within a repeating unit are compensated using a constant value based on the estimated phase offset. 11. The method of claim 1, wherein the method is implemented on a non-terrestrial network (NTN) PRACH receiver; wherein the method further comprises: - pre-compensating the plurality of repeating units based on satellite orbit information before performing the phase offset estimation. 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 comprises a plurality of elements on a plurality of antennas; - selectively correlate a plurality of repeating units in the plurality of repeating sequences according to the amplitude of the elements, thereby estimating a phase offset of the plurality of repeating units; - perform phase compensation on the plurality of repeating units according to the estimated phase offset; - perform sequence merging on the plurality of repeating units; and - perform sequence detection on the merged plurality of repeating units. 12. The PRACH receiver of claim 11, wherein a plurality of elements 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; wherein, at the specific positions, the two repeating units where the two dominant elements are located are correlated. 13. The PRACH receiver of claim 12, wherein the two repeating units are non-adjacent repeating units. 14. The PRACH receiver of claim 11, wherein the plurality of repeating units are all or a portion of the plurality of repeating sequences, or all or a portion of the preamble signals received on the plurality of antennas. 15. The PRACH receiver of claim 12, wherein all or some of the possible merging of any two repeating units among the plurality of repeating units are used for the phase offset estimation, or, distances less than or equal to a threshold are 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, calculating the correlated phase of the two repeating units. 17. The PRACH receiver of claim 16, wherein for all used merges, the estimated phase offset is a weighted average of the correlated phase of the two repeating units relative to the distance between the two repeating units. 18. The PRACH receiver of claim 11, wherein, for a specific position among the plurality of repeating units, all possible merges of any two repeating units among the plurality of repeating units are correlated to select k merges with the highest k correlation values; wherein the k correlation values ​​are used for the phase offset estimation. 19. The PRACH receiver of claim 11, wherein in the phase compensation, all elements within a repeating unit are compensated with a constant value based on the estimated phase offset. 20. A computer-readable product comprising computer-readable code, which, when executed on a device, causes the device to: - receive a PRACH preamble having a plurality of repeating sequences, wherein each sequence comprises a plurality of elements on a plurality of antennas; - selectively correlate a plurality of repeating units in the plurality of repeating sequences according to the amplitude of the elements, thereby estimating the phase offset of the plurality of repeating units; - perform phase compensation on the plurality of repeating units according to the estimated phase offset; - perform sequence merging on the plurality of repeating units; and - perform sequence detection on the merged plurality of repeating units. 3 CN 120077616 A Specification i / 12. Method and Apparatus for Phase Offset Estimation and Compensation of PRACH with Large Frequency Offset Technical Field

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

[0002] PRACH preambles are special sequences used for synchronization and identification in wireless communication systems. In Long Term Evolution (LTE) and 5G systems, PRACH preambles play an important role in the random access process.

[0003] PRACH preambles typically have multiple repeating sequences to improve coverage and anti-interference capabilities, and to support beam scanning. For example, there are 12 repeating sequences in format B4 (short sequence) and 4 repeating sequences in format 3 (long sequence). For example, Zadoff-Chu (ZC) sequences with symbol lengths of 139.839,569, or 1149 can be used as PRACH sequences.

[0004] Figure 1 showsAn example of a PRACH preamble decoding method 100. The signal can be received on multiple antennas, and the signal received on each antenna can include multiple sequences, such as 12 sequences, each of which can include multiple symbols. In the example method 100 of FIG1, a downsampling step 110, a serial-to-parallel conversion step 120, a correlation step 130, and a signal combining step 140 can be performed sequentially 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 sequence to determine the matching sequence by comparing it with the local sequence.

[0005] That is, in the method 100 of FIG1, the sequences in the received signal are correlated in step 130 and then combined in step 140. Since the received signal has multiple sequences (e.g., 12 sequences) that are not combined, performing correlation processing on all 12 sequences in both the time and frequency domains would result in huge complexity. Therefore, an improved method is to perform sequence combining first and then correlation, as shown in FIG2.

[0006] Figure 2 shows an example of another decoding method 200 for the TPRACCH preamble. Compared to Figure 1, Figure 2 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 can be merged into one sequence, thereby reducing the complexity of the correlation step 130. Then, in step 240, antenna merging can be performed. The method 200 in Figure 2 can improve the decoding and detection of the PRACH preamble by reducing complexity. However, some problems still exist.

[0007] In non-terrestrial networks (NTNs), due to high mobility, the carrier frequency offset (CFO) mismatch between the transmitter and receiver may be larger than in terrestrial networks. For example, in NTN networks relayed by satellites (or satellite networks), the Doppler shift will cause a CFO mismatch between the transmitter and receiver due to the high mobility of satellites (especially low-Earth orbit satellites). Mobile networks associated with high-speed trains (HST) may also face similar issues. HSTs are considered a key vertical application area for 5G, and due to the rapid movement of trains and mobile devices on board, there is a very large CF0. Prior information about satellite orbits or trains cannot effectively mitigate the impact of CF0; even after CF0 pre-compensation, a non-negligible residual CF0 remains.

[0008] At the transmitting end, these sequences originally transmit the same signal, but if a large CF0 exists, different sequences will have different phase shifts at the receiving end. Figure 3 shows the phase shifts of different sequences of the received signal. For example, as...As shown in Figure 3, the first sequence (Sequence 0) can be considered phase-aligned, but subsequent sequences may have a phase shift starting from page 2 / 12 of the specification. The phase shift can accumulate over time, meaning the phase shift of each symbol may be greater than the previous symbol. The slope of the phase shift may be CF0. That is, the phase shift of Sequence 1 is A.<!---->The phase shift of sequence 2 is 2 AO, and so on. Phase shifts can be detrimental to the sequence merging introduced in step 225 of Figure 2 because if the phase shifts between sequences or symbols are 180 degrees (in the domain redundancy), they will cancel each other out. Therefore, 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 transmission preamble sequence; finding one subframe, currently a PRACH time-domain subframe; estimating the Doppler frequency offset value according to the relevant parameters using the maximum likelihood (ML) criterion as frequency offset compensation; performing cyclic prefix elimination, downsampling 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 sum, and multi-antenna combining on the frequency domain correlated sequence, calculating the power delay spectrum energy (PDP), and comparing the power delay spectrum energy (PDP) with detection thresholds A and B to obtain the preamble sequence number ID and time advance (TA). However, the CFO followed by downsampling method in CN108040366A may be more difficult to directly process unsampled signals, and storing unsampled signals will increase storage overhead. A particular problem with CN108040366A is 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 apparatus, a communication device and a storage medium. The method includes: when an access signal is detected in a PRACH signal transmitted by a signal transmitter, acquiring the main peak and secondary peak of the PRACH signal, wherein the PRACH signal is composed of a preset number of identical pilot sequences; determining a first frequency offset based on the peak value of the main peak and the peak value of the secondary peak; performing frequency offset compensation on the PRACH signal based on 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 a second frequency offset, and estimating the time delay of the access signal based on the second frequency offset. Patent documents US9491024B2, WO2010040264A1, and WO2013172748A1 (US20150139098A1) propose a post-correlation CFO method similar to CN112887241A. However, the post-correlation CFO method in CN112887241A cannot be used for the case under consideration, i.e., the phase shift is estimated before correlation, and the peak value can only be obtained after correlation.A particular problem with CN112887241A is that the PRACH format is modified, making it unsuitable for the PRACH format specified by the 3rd Generation Partnership Project (3GPP), and potentially very complex.

[0011] It can be seen that for PRACH reception under large CFO conditions, merging sequences after correlation (Figure 1) can lead to significant complexity; while merging sequences before correlation (Figure 2) can result in poor detection performance. Therefore, the objective is to propose a new algorithm for CFO estimation / compensation before early merging, achieving 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 Physical Random Access Channels (PRACH) with large frequency offsets.

[0013] In some embodiments, a method for PRACH preamble detection is proposed. The method may include at least the following steps: receiving a PRACH preamble having multiple repeating sequences, wherein each sequence includes multiple elements on multiple antennas; selectively correlating multiple repeating units in the multiple repeating sequences according to the amplitude of the elements, thereby estimating the phase offset of the multiple repeating units; performing phase compensation on the multiple repeating units according to the estimated phase offset; performing sequence merging on the multiple repeating units; and performing sequence detection on the merged multiple repeating units.

[0014] In some embodiments, a PRACH receiver in a wireless communication system is proposed, which may include a memory storing machine-readable instructions; and a processor for executing machine-readable instructions. When the processor executes the machine-readable instructions in the specification 5 CN 120077616 A, it configures the PRACH receiver to: receive a PRACH preamble having multiple repeating sequences, wherein each sequence includes multiple elements on multiple antennas; selectively correlate multiple repeating units in the multiple repeating sequences according to the amplitude of the elements, thereby estimating the phase offset of the multiple repeating units; perform phase compensation on the multiple repeating units based on the estimated phase offset; perform sequence merging on the multiple repeating units; and perform sequence detection on the merged multiple 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 perform the above methods.

[0016] The embodiments propose a new algorithm for CFO estimation / compensation before early merging, and achieve a good balance between complexity and detection performance.For example, an embodiment may have a low missed detection rate (MDR), where MDR indicates that a PRACH has been sent but not detected (i.e., a missed detection); an embodiment may also have a low false alarm rate (FAR), where FAR indicates that no PRACH was sent, but the receiver erroneously detected a false alarm at the PRACH pin.

[0017] The accompanying drawings are incorporated in and constitute a part of this disclosure and illustrate various embodiments of the present disclosure, and together with the description, further serve to explain the principles of the present disclosure and enable those skilled in the art to make and use embodiments of the present disclosure. In the accompanying drawings, the same reference numerals denote the same or similar functional elements, wherein:

[0018] Figure 1 shows an example of a PRACH preamble decoding method;

[0019] Figure 2 shows another example of a PRACH preamble decoding method;

[0020] Figure 3 shows the phase shift of different sequences of received signals;

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

[0022] Figure 5 shows the amplitude variation of an undownsampled signal;

[0023] Figure 6 shows an example of a phase shift estimation method according to an embodiment of the present invention;

[0024] Figure 7 shows an example of a phase shift compensation method 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 implementation apparatus according to an embodiment of the present invention. Detailed Description

[0027] Embodiments of the present invention will now be described in detail with reference to the accompanying drawings, in which embodiments are shown. However, these embodiments of the present invention may be embodied in many different forms and should not be construed as limited to the embodiments described herein. Elements in the drawings are not necessarily drawn to scale.

[0028] The reference to “an embodiment” or “an embodiment” means that a particular feature, structure, or characteristic associated with an embodiment is included in at least one embodiment. Therefore, the phrase “in an embodiment” appearing throughout the specification does not necessarily refer to the same embodiment.

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

[0030] In this specification and claims, a list of items connected 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. 6 CN 120077616 A Specification 4 / 12 pages

[0031] Figure 4 shows an example of a method for decoding the PRACH preamble according to an embodiment of the present invention.In Figure 4, compared to Figure 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 may be combined into a single phase offset estimation and compensation step.

[0032] In the example method 400 of Figure 4, the received signal may be 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 merging step 225, a correlation step 130, an antenna merging step 240, and a detection step 150 in sequence.

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

[0034] In one example, a pre-compensation step may be provided before the phase offset estimation step 421 and the phase offset compensation step 422, wherein the sequence (i.e., repeating units) may be pre-compensated based on satellite orbit information. Then, the remaining (or residual) phase offset is estimated and compensated in phase offset estimation step 421 and 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, each sequence can include multiple symbols.

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

[0037] 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 represented 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, which can be repeated sequences. That is, they are the same at the transmitting end. For example, to reduce computational complexity, the proposed method can consider only 6 sequences. These six sequences can also be referred to as “repetitions”.

[0040] In one example, the multiple sequences (i.e., sequence repetitions) used in the calculation can be all of the multiple repetition sequences (e.g., all 12 sequences) or a portion of the multiple repetition sequences (e.g., 6 of the 12 sequences). From a signal perspective, the multiple sequences (i.e., sequence repetitions) 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 received sequence with sequence spacing can be expressed as y'(s-m,n,i), wherein the sequence distance (or sequence spacing) 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 (sequence spacing) between sequence 10 and sequence 11 is 1.

[0042] According to the above representation, for a given sequence spacing m, a method for estimating Δ<0> (m) can be: Δ<0>(m) = 1 / m angle ∑_s∑_n∑_i y(s,n,i)y'(s-m,n,i)* Equation (1)

[0043] Wherein, Δ<0>(m) refers to Δ<0> calculated through the sequence spacing m (as shown in Figure 3), and does not refer to the estimated phase offset of the sequence m. In fact, the estimated phase offset of the sequence s = 1,2,…, S should be s*Δ<0>.

[0044] As shown in Equation (1), two sequences, namely the sequence y'(s-m,n,i) and the sequence y(s,n,i), are correlated by conjugate multiplication. Then, the correlation value is converted into an angle to obtain the phase offset of the sequence spacing m, and the phase offset of the sequence spacing m is divided by m to obtain a normalized phase offset Δ<0>(m), that is, the phase offset of a single sequence spacing (that is, the phase offset between two adjacent sequences). 7 CN 120077616 A Description Page 5 / 12

[0045] In one example, performing phase offset estimation includes calculating the correlated phase of two repeating units, for the combination including two repeating units, as shown in the calculation of "angle ()" in Equation (1).

[0046] If Equation (1) is applied to all possible values of m, for example m=1,2,…S-1, the final Δ<0> can be: Δ<0> = 1 / (∑_{m=1}^{S-1} 1 / m) angle ∑_{m=1}^{S-1} 1 / m (∑_{s=m}^{S} ∑_{n=0}^{N} y(s,n,i) y(s-m,n,i)* ) Equation (2)

[0047] As shown in Equation (2), for each value of m, for example m=1,2,…S-1, the combination of two sequences, namely the sequence y'(s-m,n,i) and the sequence y(s,n,i), is correlated by conjugate multiplication. Then, each correlation value is converted into an angle to obtain the phase offset of the sequence spacing m. Then, each phase offset of the sequence spacing m is divided by m to obtain a normalized phase offset Δ<0>(m), that is, the phase offset of a single sequence spacing (that is, the phase offset between two adjacent sequences). Then, the m Δ<0>(m) can be averaged to form the final Δ<0>.

[0048] Depending on whether m=1, the two sequences in the combination 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 viewed as a single calculation, i.e., a weighted average. That is, in equation (2), for all the merges used, the estimated phase shift is the weighted average of the phases of the two repeating units relative to the distance between the two repeating units (i.e., the sequence interval m).

[0050] In a specific example of equation (2), if there are 12 sequences. Using all possible merges of any two sequences, there are C?2 = - = 66 possible merges of the two sequences.

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

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

[0053] For example, the threshold can be set to 6. In this way, sequence 1 can be associated with sequence 7, but not with sequence 8. Therefore, in step 421, only 51 of the 66 possible merges are used for phase offset estimation.

[0054] The complexity of merging all 66 possible sequences (or repeating units) is too great. An embodiment could further suggest correlating multiple repeating units based on the amplitude of the elements to reduce complexity. Figure 5 shows the amplitude variation of the undownsampled signal. As shown in Figure 5, there may be amplitude variations in the undownsampled signal, i.e., some samples may be stronger than others. Here, the term "element" can refer to a sample on an antenna, such as 1024 samples on 4 antennas.

[0055] The embodiment considers that stronger samples may lead to sample correlation values, i.e., a larger correlation may come from the dominant element.

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

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

[0058] Figure 6 shows an example of the phase offset estimation method according to an embodiment of the present invention. In Figure 6, the antenna size is not shown. As shown in the upper part of Figure 6, the horizontal axis is the sample axis and the vertical axis is the sequence axis. As shown in Figure 6, there may be 4 sequences (4 repeating units), and each sequence may include 8 samples. If there are 4 antennas, each sequence may include 8*4 = 32 samples, or 32 elements; all 4 sequences include 128 elements.

[0059] It should be noted that the sequence length shown in FIG. 6 is only an example, and each sequence may include more or fewer samples. For example, there may be 1024 samples in one sequence.

[0060] It should be noted that the calculation samples shown in the figure are only an example. For example, partial samples may be used for calculation. For example, there may be 1024 samples in one sequence, among which only 128 samples with large amplitudes are used for calculation.

[0061] In one example, for each of the 8 elements in the sequence shown in FIG. 6, there may be 4 elements in one column of FIG. 6. For example, for sample 1 (element 1), which may be referred to as "a specific position of a plurality of repeating units", there are 4 elements in the first column.

[0062] For this "specific position of a plurality of repeating units" (shown as one column in FIG. 6), a dominant element that occupies a dominant position will be selected. For position (n,i), that is, specific sample n on specific antenna i, dominant elements s₁ and s₂ can be expressed as s₁(n,i), s₂(n,i), (s₁<s₂), which have the two largest a_{fc} C_{γ} (ω, n, θ) ∀_{ω, γ}. In an example, the dominant elements may have the largest amplitudes, that is, they are dominant elements in terms of amplitude.

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

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

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

[0066] For example, as shown at the bottom of FIG. 6, 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] In other words, equation (2) may be changed into the following equation (3), where correlation is performed on the dominant element of each position. ΔΦ = Σ jangle ( y{s2(n i), n, i) * y(sl(n i), n, i)') where G(m) = {(n,i) with s2(n,i) - s1 (n,i) = m} Equation (3) 9 CN 120077616 A Description 7 / 12

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

[0069] Compared with equation (1), for equation (3), correlation can be performed only once for each position in the sequence, so equation (3) can be regarded as one correlation across positions. Therefore, the complexity of phase offset estimation can be significantly reduced, especially for sequences with a large number of samples (e.g., 1149 samples). Through equation (3), elements with the greatest impact and strongest noise resistance can be captured while reducing 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 sequence interval m can be set, that is, each combination including two repeating units whose sequence interval m (or sequence distance) is less than or equal to the threshold is used for phase offset estimation.

[0071] According to whether m=1, the two sequences in the combination can be adjacent repeating units or non-adjacent repeating units. For adjacent repeating units, m=1.

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

[0073] For example, as shown in FIG. 7, for the s-th sequence, y (s,n,i) is updated in the following manner: y_update(s,n,i) = y(s,n,i)*exp(j*ΔΦ*(s-1)) Equation (4)

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

[0075] In addition, in another method (compensation scheme 2 in FIG7), symbols in the same sequence can be compensated with different phase offsets, that is, the phase offset compensation of the first symbol is less than the phase offset compensation of the last symbol, so that the phase offset compensation can be linear, as shown in FIG7.

[0076] In one example, if a sequence has 256 symbols, then the phase offset compensation for each symbol may be A(D / 256) more than the phase offset compensation for the previous symbol.

[0077] Comparing the two compensation schemes in Figure 7, compensation scheme 1 is preferred because it has lower complexity and the constant part of each sequence has the greatest impact on performance. In addition, compensation scheme 1 is also suitable for larger CFOs, for example, ΔO may be greater than 360 degrees (or 2;:), in which case A0 / 256 may be incorrect because the estimated Δ may actually be ΔO-2n. That is, although Δ① and Δ^ have no difference for correlation or sequence merging (they can be regarded as the same phase), ΔO / 256 and (ΔO-2n) / 256 may be completely different in phase.

[0078] It should be noted that the features suggested above 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) (making m=1) and equation (4); the proposed scheme (3) using equation (3) or equation (4).

[0080] The missed detection rate (MDR) and false alarm rate (FAR) of schemes (1) to (4) under the FR2 B460kHz SCS case in the 3GPP standard are compared, and the following table is obtained. Table 1: Simulation performance of each scheme 10 CN 12b077616 A Specification 8 / 12 pages Scheme Sentence-to-noise ratio -6.9dB Sentence-to-noise ratio -6.9dB False alarm rate (including additional error) Scheme (1) 0.22% 5.42% Scheme (2) 29.98% 0.06% Scheme (3) 3.14% 0% Scheme (4) 0.3% 0%

[0081] As can be seen from Table 1, the proposed schemes, especially the proposed scheme (4), can meet the 3GPP requirements for a large CFO false negative rate and can achieve better MDR and FAR performance than existing schemes.

[0082] The complexity of scheme (1) in Figure 1 (where merging is performed after correlation) can be given in the following table (in units of runs). For short sequences, assume there are 12 sequences, each with 256 symbols; for long sequences, assume there are 4 sequences, each with 1024 symbols.Table 2: Simulation complexity of existing technical solution (1) for short sequences Table 3: Simulation complexity of existing technical solution (1) for long sequences For short sequences, the total number of calls per call is: 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 Combined antenna / sequence 2*12 256*64 393216 Total 4374528 For long sequences, the total number of calls per call is: FFT 1024*log2(1024) 2*4 81920 Multiplication 1024 2*4*64 1048576 IFFT 2048*log2(2048) 2*4*64 11534336 Power 2048 2*4*64 1048576 Combined antenna / sequence 2*4 2048*64 1048576 Total 14761984

[0083] Then, for short and long sequences, the proposed scheme (4) can significantly reduce complexity, for example as shown in the table below.Table 4: Suggested Scheme (4) Simulation Complexity for Short Sequences For short sequences, the number of calls per call Subtotal Find the dominant element 2*256*11*2 11264 Phase estimation 2*256*2+11*3 1057 Compensation 256 11*2 5632 Merging sequence 12 256*2 6144 FFT 256*log2(256) 2 4096 11 CN 120077616 A Manual 9 / 12 Table 5: Suggested Scheme (4) Simulation Complexity for Long Sequences Multiplication 256 2*64 32768 IFFT 256*log2(256) 2*64 262144 Power 256 2*64 32768 Merging antenna 2 256*64 32768 Total 388641 For long sequences, the subtotal of each call is: Find the dominant element: 2*1024*3*2 = 12288; Phase estimation: 2*1024*2+3*3 = 4105; Compensation: 1024 = 3*2 = 6144; Merging sequence: 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; Merging antenna: 2 = 2048*64 = 262144; Total: 3721225

[0084] Comparing schemes (1) and (4), in terms of complexity, the proposed scheme (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 schemes (2) or (3) (which are substantially the same in terms of complexity), the proposed scheme may slightly increase the complexity, by 6.6% for short sequences and less than 8.3% for long sequences.

[0086] FIG8 shows an example PRACH receiver 800 according to an embodiment of the present invention. In one embodiment, the example PRACH receiver 800 in FIG8 may be configured to perform 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 perform the above method 400.

[0088] Please note that the PRACH receiver 800 may be implemented in hardware, software, firmware, or any combination thereof. For example, the PRACH receiver 800 may include multiple units, circuits, modules, etc., each of which may be used to perform one or more steps of the example method 400.

[0089] In one embodiment, the PRACH receiver 800 may 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 Bs, evolved Node Bs (eNBs), and NRNode Bs (gNBs)), O-RAN nodes, or components of O-RAN nodes (e.g., O-RUs, O-DUs, O-CUs).

[0090] FIG9 shows an example of a computer implementation apparatus 900 according to an embodiment of the present invention. In one embodiment, apparatus 900 may be configured as the PRACH receiver described above as shown in FIG8.

[0091] In one embodiment, apparatus 900 may 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. Memory 903 may 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 may be configured to store a computer program and / or instructions that, when executed by the processor 901, cause the processor 901 to perform any of the methods described above (CN 120077616 A specification, pages 10 / 12, 400).

[0092] In one embodiment, the computer-readable medium 902 (such as a non-transitory computer-readable medium) may be stored in a memory 903. In another embodiment, the computer program may be stored at a remote location, such as a computer program product 904 (which may also be embodied in a computer-readable medium), and accessed by the processor 901 via 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, CD (optical disc), DVD (digital video disc), flash memory or similar removable storage media (e.g., compact flash memory, SD (Secure Digital), Memory Stick, mini SD card, MMC multimedia card, smart media), HD-DVD (high-definition DVD) or Blu-ray DVD, USB (Universal Serial Bus) based removable storage media, magnetic tape media, optical storage media, magneto-optical media, bubble memory, or as a propagation signal through a network (such as Ethernet, ATM, ISDN, PSTN, X.25, 5.5 networking, local area network (LAN) or similar network capable of transmitting data packets to infrastructure nodes).

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

[0095] Example 1. A method for detecting a Physical Random Access Channel (PRACH) preamble, comprising: - receiving a PRACH preamble having a plurality of repeating sequences, wherein each sequence comprises a plurality of elements on a plurality of antennas; - selectively correlating a plurality of repeating units in the plurality of repeating sequences according to the amplitude of the elements, thereby estimating the 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; and - performing sequence detection on the merged plurality of repeating units.

[0096] Example 2. The method of claim 1, wherein a plurality of elements located at specific positions in 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, the two repeating units in which the two dominant elements are located are correlated.

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

[0098] Example 4. The method of Example 1, wherein the plurality of repeating units are all or part of the plurality of repeating 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 mergings or partial mergings of any two repeating units among the plurality of repeating units are used for phase offset estimation, or each merging of two repeating units including 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 merging including the two repeating units, calculating the correlated phase of the two repeating units.

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

[0102] Example 8. The method according to Example 1, wherein, for a specific location of the plurality of repeating units, all possible mergings of any two repeating units among the plurality of repeating units are correlated to select k mergings with the highest 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, all elements within a repeating unit are compensated with a constant value based on the estimated phase offset. 13 CN 120077616 A Specification ii / 12 Gong

[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 comprises: - pre-compensating multiple repeating units based on satellite orbit information before performing phase offset estimation.

[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 comprises a plurality of elements on a plurality of antennas; - selectively correlate a plurality of repeating units in the plurality of repeating sequences according to the amplitude of the elements, thereby estimating a phase offset of the plurality of repeating units; - perform phase compensation on the plurality of repeating units according to the estimated phase offset; - perform sequence merging on the plurality of repeating units; and - perform sequence detection on the merged plurality of repeating units.

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

[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 preamble signals received on a plurality of antennas.

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

[0110] Example 16. The PRACH receiver according to Example 15, wherein phase offset estimation includes: for a merging that includes two repeating units, calculating the associated phase of the two repeating units.

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

[0112] Example 18. A PRACH receiver according to Example 11, wherein, for a specific location of a plurality of repeating units, all possible combinations of any two repeating units in the plurality of repeating units are correlated to select the k combinations of the highest k correlation values; wherein the k correlation values ​​are used for phase offset estimation.

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

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

[0115] It should be appreciated that the principles of the present disclosure are not limited to the described embodiments, and modifications and changes may be made without departing from the scope of the appended claims. The above-described embodiments may include only subsets of these features, different orders of these features, different combinations of these features, and / or more features other than those explicitly listed. Therefore, the scope of the embodiments should be determined with reference to the appended claims and the scope of all equivalents afforded by these claims. 14 CN 120077616* A Description Page 12 / 12 15 CN 120077616 A Description of Drawings Page 1 / 7 100 110 120 \ Start Downsampling Serial-to-parallel conversion Correlation 1 Correlation Correlation T Combination Detection FIG. 1 (Prior Art) 16 CN 120077616* A Description of Drawings Page 2 / 7 110 120 225 130 240 150 FIG. 2 (Prior Art) Time FIG. 3 (Prior Art) 17 CN 120077616 A Description of Drawings Page 3 / 7 240 150 225 422 ><^x130 421 Start Downsampling Serial-to-parallel conversion Phase offset estimation Phase offset compensation Sequence combination Correlation Antenna combination Detection FIG. 4 18 CN 120077616* A Description of Drawings Page 4 / 7 Amplitude variation of unsampled signal Sampling points x104 FIG. 5 19 CN 120077616 A Description of Drawings Page 5 / 7 Sampling points => x3)m = 3 ►♦♦♦ ►♦♦♦ ►♦♦♦ *♦♦♦ ,,, >•••••• »♦♦♦ 国II = 三 三 = 三 Weighted average on m FIG. 6 20 *CN 120077616 A Description of Drawings Page 6 / 7 Sequence 0 Sequence 1 … Sequence 11 FIG. 7 800 PRACH receiver FIG. 8 21 CN 120077616 A Description of Drawings Page 7 / 7 900 Computer program product ^904 FIG. 9 22.

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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