A preamble-free access TA synchronization method and apparatus that saves time domain resources

Abstract

This invention discloses a preamble-free access TA synchronization method and apparatus that saves time-domain resources, comprising: coarse search for candidate TAs: selecting multiple TA candidates within a preset range with a fixed step size; signal preprocessing: receiving repeatedly transmitted Msg3 frames and obtaining the frequency domain data corresponding to each TA candidate; parallel soft combining and score calculation: performing channel estimation, equalization, and descrambling on each candidate data in parallel to obtain descrambling LLR soft bits, and accumulating their absolute values ​​to calculate the synchronization score of each candidate; candidate selection and decoding verification: sorting by score and selecting high-scoring candidates for decoding and CRC verification; synchronization confirmation: using the successfully verified TA as the final synchronization quantity. This invention saves preamble time slots and response windows, significantly reducing access latency and resource consumption.

Description

Technical Field

[0001] This invention relates to the field of communication technology, and in particular to a preamble-free access TA synchronization method and apparatus that saves time domain resources. Background Technology

[0002] In cellular communication systems, before a terminal initiates an uplink transmission, it needs to complete a time synchronization with the base station to obtain a timing advance (TA) to compensate for signal propagation delay, thereby ensuring that the uplink signals of multiple terminals can be received in time alignment at the base station.

[0003] Currently, systems represented by Narrowband Internet of Things (NB-IoT) generally adopt the traditional four-step random access procedure to complete the initial uplink synchronization. This procedure specifically includes: the terminal sending a random access preamble (NPRACH, i.e., Msg1); the base station detecting the preamble and replying with a random access response (Msg2, which includes the TA calculated for the terminal and uplink resource grant); the terminal sending the Msg3 data frame according to the grant; and the base station finally replying with a contention resolution message (Msg4). However, this traditional procedure suffers from significant time-domain resource waste and efficiency problems, mainly in the following aspects:

[0004] 1. NPRACH periodically occupies fixed resources: Base stations must periodically reserve dedicated NPRACH time-frequency resources for contention-based access. Each NPRACH transmission opportunity occupies time-domain resources ranging from 5.6ms to 34.8ms (the specific duration depends on the preamble format). Even if no terminal needs to access the network at that time, these resources cannot be used for data transmission, resulting in reduced spectrum utilization.

[0005] 2. RAR window introduces waiting delay: After sending Msg1, the terminal must continuously listen to the downlink channel within a preset random access response window to receive Msg2. This RAR window typically lasts 2~10ms, increasing the overall latency of terminal access and listening power consumption.

[0006] 3. Separation of TA detection and data transmission steps: In traditional schemes, TA detection relies entirely on an independent random access preamble sequence. Only after successfully acquiring the TA can the base station schedule the terminal to transmit data (Msg3). These two steps are executed serially, with the delays superimposed, prolonging the overall access process.

[0007] 4. Existing simplification schemes are still not thorough: The two-step random access (MsgA+MsgB) scheme introduced in later versions of the 3GPP program merges the transmission of preamble (Msg1) and data (Msg3), but the preamble sequence still needs to be transmitted, and the window waiting problem of MsgB still exists. It fails to fundamentally eliminate the time domain overhead caused by preamble transmission and response waiting.

[0008] In scenarios highly sensitive to latency and resource efficiency, such as satellite communication, industrial IoT, and massive terminal access, the waste of the aforementioned time-domain resources will lead to a series of adverse effects, including limited system access capacity, increased terminal access latency, increased probability of random access conflicts, and increased terminal power consumption. Therefore, there is an urgent need in this field for a novel uplink synchronization technology solution that can significantly save time-domain resources and simplify the access process. Summary of the Invention

[0009] To address the shortcomings of existing technologies, this invention provides a preamble-free access TA synchronization method and apparatus that saves time-domain resources.

[0010] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is as follows:

[0011] A time-domain resource-saving, preamble-free access TA synchronization method includes the following steps:

[0012] Step S1, coarse search for candidate TAs: within the preset TA search range, a coarse search is performed with a preset step size to filter out M TA candidates, where M is an integer greater than 1;

[0013] Step S2, Signal preprocessing: Receive Msg3 data frames containing known DMRS reference signals sent by user equipment, and obtain frequency domain data corresponding to each TA candidate;

[0014] Step S3, Parallel soft combining and score calculation: Perform channel estimation, equalization and descrambling processing on the frequency domain data corresponding to each TA candidate to obtain the descrambled LLR soft bits corresponding to each TA candidate; for each TA candidate, accumulate the absolute value of the descrambled LLR soft bits of the Msg3 data frames that are repeatedly transmitted to obtain the score of each TA candidate.

[0015] Step S4, Candidate Screening and Decoding Verification: Sort all TA candidates from high to low according to their scores, and select the N TA candidates with the highest scores for decoding and CRC verification, where N is a positive integer less than M;

[0016] Step S5, Synchronization Confirmation: The TA candidate with successful CRC verification is used as the final synchronization TA to complete the data auxiliary synchronization; if the CRC verification of all selected N TA candidates fails, the access synchronization is determined to have failed.

[0017] Furthermore, in step S1, the preset TA search range is 5~205, the preset step size is 10~20, and the number of the M TA candidates obtained by screening is 20.

[0018] Further, step S1 specifically includes: within the TA search range, performing a coarse search with a fixed step size to obtain a set of initial TA candidate points; supplementing TA points between adjacent initial TA candidate points so that the total number of TA candidates reaches M.

[0019] Further, in step S2, obtaining the frequency domain data corresponding to each TA candidate includes:

[0020] The received time-domain sampled signal is sliced ​​according to the time-domain position corresponding to each TA candidate to construct a two-dimensional array;

[0021] The frequency domain data corresponding to all TA candidates is output at once through a single batch FFT operation.

[0022] Furthermore, in step S2, the channel estimation performed for each TA candidate is batch parallelized, including:

[0023] Organize the DMRS data in the frequency domain data corresponding to each TA candidate into a unified array;

[0024] By performing a single batch processing operation, the DMRS channel estimation of all TA candidates is completed in parallel, resulting in independent channel parameters for each TA candidate.

[0025] Furthermore, in step S3, the score The calculation formula is:

[0026]

[0027] in, For the first The TA candidate, the first The 1st retransmission After descrambling, the LLR soft bits are used, where R is the number of times the Msg3 data frame is repeatedly transmitted. This represents the total number of LLR soft bits after descrambling.

[0028] This invention also discloses a time-domain resource-saving preamble-free access TA synchronization device, characterized in that it is used to perform the above-described preamble-free access TA synchronization method, comprising:

[0029] The TA coarse search module is used to perform a coarse search within a preset TA search range with a preset step size, and filter out M TA candidates, where M is an integer greater than 1;

[0030] The signal preprocessing module is used to receive Msg3 data frames containing known DMRS reference signals sent by user equipment, and to obtain frequency domain data corresponding to each TA candidate.

[0031] The soft combining and score calculation module is used to perform channel estimation, equalization and descrambling processing on the frequency domain data corresponding to each TA candidate, to obtain the descrambled LLR soft bits corresponding to each TA candidate, and to accumulate the absolute value of the descrambled LLR soft bits of the Msg3 data frames that are repeatedly transmitted for each TA candidate to calculate the score.

[0032] The decoding and verification module is used to sort all TA candidates from high to low according to the score, and select the N TA candidates with the highest scores for decoding and CRC verification, where N is a positive integer less than M.

[0033] The synchronization confirmation module is used to select the TA candidate that has a successful CRC check as the final synchronization TA to complete the synchronization; if the CRC check of all N selected TA candidates fails, the access synchronization is determined to have failed.

[0034] Furthermore, the signal preprocessing module includes a batch FFT submodule, which slices the received time-domain sampled signal according to the time-domain position corresponding to each TA candidate and constructs a two-dimensional array, and outputs the frequency domain data of all TA candidates at once through a single batch FFT operation.

[0035] Furthermore, the soft combining and scoring calculation module includes a batch channel estimation submodule, which organizes the frequency domain DMRS data of each TA candidate into a unified array, and performs channel estimation of all TA candidates in parallel through batch processing to obtain independent channel parameters for each group.

[0036] Furthermore, the device is applied to narrowband IoT, satellite communication, or industrial IoT systems, and is adapted to the synchronous processing of user equipment directly transmitting Msg3 data frames in scenarios without preamble access.

[0037] Compared with the prior art, the advantages of the present invention are as follows:

[0038] 1. Completely simplified access process, enabling direct transmission without preamble: This invention eliminates the traditional random access preamble transmission and response interaction, allowing the terminal to immediately send data frames after obtaining system information. This fundamental change simplifies the signaling process and reduces the complexity and signaling overhead of the access procedure.

[0039] 2. Significantly saves air interface time domain resources and greatly reduces access latency: By eliminating the time slots dedicated to preamble transmission and the window time for the terminal to wait for the base station response, this invention combines uplink synchronization and data reception into one, thereby significantly shortening the total latency from the terminal initiating access to completing synchronization and data transmission, and freeing up valuable time domain resources for data transmission.

[0040] 3. Effectively improve system access capacity and spectrum utilization: The time-domain resources saved, which were originally reserved periodically for random access, can be dynamically scheduled to carry user data services. This allows the system to serve more concurrent terminals under the same frame structure, thereby improving the overall network access capacity and spectrum resource utilization efficiency.

[0041] 4. The algorithm design is highly efficient, significantly reducing baseband processing complexity and latency: By adopting a multi-level processing architecture of "fixed candidate set coarse synchronization, soft information merging for rapid filtering, and head candidate fine decoding," this invention avoids the huge computational overhead caused by exhaustive search and polling decoding across the entire latency range. The algorithm has a fixed flow, controllable computational load, and is easy to implement in hardware, thus significantly reducing baseband processing latency.

[0042] 5. Strong compatibility, facilitating deployment and smooth evolution in existing networks: The improvements in this invention focus on the receiving and processing algorithms on the network side (base station), without altering the signal format and process transmitted on the terminal side, and are fully compatible with the frame structure defined by existing standard protocols. Therefore, it is easy to deploy by upgrading existing network equipment through software, supporting seamless access for existing terminals. Attached Figure Description

[0043] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a flowchart of the preamble-free access TA synchronization method in an embodiment of the present invention;

[0045] Figure 2 This is the TA candidate coarse search graph in an embodiment of the present invention;

[0046] Figure 3 This is a schematic diagram of batch FFT in an embodiment of the present invention;

[0047] Figure 4 This is the TA LLR score map in an embodiment of the present invention;

[0048] Figure 5This is a flowchart of the candidate screening and decoding verification process in an embodiment of the present invention. Detailed Implementation

[0049] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] This invention is applicable to communication systems with high requirements for latency and resource efficiency, such as narrowband IoT and satellite communication. In the following embodiments, taking a low signal-to-noise ratio narrowband communication scenario as an example, after receiving system broadcast information, the terminal does not send a traditional random access preamble, but directly sends an uplink data frame (Msg3) repeated 64 times. The receiving end performs integrated synchronization of timing advance detection and data decoding based on this Msg3 data frame. The overall process can be referred to... Figure 1 As shown.

[0051] S1: Generation of TA candidate sets

[0052] The receiving end first determines the timing advance range to be searched. In this embodiment, the preset TA search range is 5 to 205. Within this range, a preliminary coarse search is performed with a large fixed step size to significantly reduce the number of candidate points requiring fine processing. Specifically, a step size of 20 is selected for the coarse search, resulting in a set of initial TA candidate points: 5, 25, 45, 65, 85, 105, 125, 145, 165, 185, and 205, totaling 11 points.

[0053] To ensure coverage of all possible propagation delays and avoid missing true TAs due to excessively large step sizes, supplementary points are added between every two adjacent coarse search candidate points. For example, an intermediate point is added between 5 and 25, and so on, ultimately forming a fixed set of M=20 TA candidates. This coarse screening process can be found in [reference needed]. Figure 2 As shown in the diagram. This step significantly reduces the number of TA possibilities to be processed from a total of 201 to 20, laying the foundation for low processing latency.

[0054] S2: Signal Reception and Batch Processing Fast Fourier Transform

[0055] The receiving end receives 64 repeated Msg3 data frames without a preamble from the receiving terminal. This data frame contains a known DMRS reference signal.

[0056] To achieve efficient parallel processing of 20 TA candidates, the receiver slices the received time-domain sampled signal according to the different time-domain start positions corresponding to the 20 TA candidate values ​​generated by S1, constructing a two-dimensional time-domain array. ,in ( ) represents the TA candidate index. Represents the index of time-domain sampling points.

[0057] Subsequently, a single-batch Fast Fourier Transform operation is performed to conduct FFT on all rows of the two-dimensional array (i.e., all TA slices) at once, and the frequency domain data corresponding to all 20 TA candidates are output in parallel. This process can be described as follows:

[0058]

[0059] This method avoids the redundant computation overhead of performing FFT operations independently for each TA candidate, significantly improving processing efficiency. This batch processing workflow can be found by referring to... Figure 3 As shown.

[0060] S3: Batch Channel Estimation

[0061] After obtaining the frequency domain data, channel estimation needs to be performed. This involves extracting the DMRS symbol positions from the 20 candidate frequency domain data points. Organized as a uniform array. Utilizing locally stored known DMRS sequences. Through a single batch processing operation, channel estimation for all 20 TA candidates is completed in parallel, yielding an independent channel frequency response for each TA candidate. The calculation formula is as follows:

[0062]

[0063] The channel parameters of each TA candidate group are independent of each other and are not reused across TAs to ensure the accuracy of the evaluation.

[0064] S4: Parallel Soft Merging and Synchronous Score Calculation

[0065] For each TA candidate, utilize its independent channel estimation results. For frequency domain data After performing equalization and descrambling processes, the final output is the descrambled log-likelihood ratio soft bit. .in, ( () represents the number of times the transmission is repeated. Represents the soft bit sequence number.

[0066] To evaluate the synchronization quality of each TA candidate, for each candidate The absolute values ​​of all descrambled LLR soft bits corresponding to its 64 repeated transmissions are taken and accumulated to obtain the synchronization score of the candidate. The calculation formula is as follows:

[0067]

[0068] in, This represents the total number of soft bits after descrambling in a single transmission. A higher score indicates better signal alignment, superior channel conditions, and a higher probability of successful decoding at that TA value. The score will exhibit a significant peak near the true TA value, such as... Figure 4 As shown.

[0069] S5: Candidate Selection and Decoding Verification

[0070] After obtaining the scores of the 20 TA candidates, all candidates are sorted from highest to lowest score. To balance processing overhead and success rate, it is not necessary to perform complete channel decoding on all 20 candidates. In this embodiment, the N=3 TA candidates with the highest scores are selected for the fine processing flow.

[0071] For these three high-scoring TA candidates, complete channel decoding (such as Viterbi decoding or Turbo decoding) and cyclic redundancy check were performed respectively. This screening and verification process can be found in [reference needed]. Figure 5 As shown.

[0072] S6: Synchronous Confirmation

[0073] If, in step S5, the decoded data of a certain TA candidate passes the CRC check, then the TA value is determined as the final timing advance for this uplink transmission, and the decoded Msg3 data is output to complete the synchronization and reception without a preamble.

[0074] If the decoded data of all three selected high-resolution TA candidates fails the CRC check, the access synchronization is deemed to have failed. The receiving end can discard the data and wait for the terminal to re-initiate the access attempt.

[0075] Table 1 shows the time-domain resource usage pairs of the present invention and traditional solutions under different scenarios. As can be seen from the table, the present invention can achieve a time-domain resource saving of 40% to 50% at all coverage levels, demonstrating its universality advantage.

[0076] Table 1: Percentage of Time Domain Resource Savings in Different Scenarios

[0077] Normal coverage (N=1) 5.6ms 2ms 8ms 15.6ms 8ms 48.7% Mild enhancement (N=2) 11.2ms 5ms 16ms 32.2ms 16ms 50.3% Moderate enhancement (N=8) 44.8ms 10ms 64ms 118.8ms 64ms 46.1% Deep augmentation (N=64) 358.4ms 10ms 512ms 880.4ms 512ms 41.8% satellite scene 50ms 20ms 100ms 170ms 100ms 41.2%

[0078] Through the above embodiments, this invention embeds the TA detection process into the reception and decoding process of the Msg3 data frame. Utilizing the data's own repetition gain and DMRS signal, and through a mechanism of fixed candidate set, parallel batch processing, LLR score-based rapid screening, and header candidate verification, it efficiently completes uplink timing synchronization without consuming additional time-domain resources. This method is particularly suitable for communication scenarios that are sensitive to latency and require high resource utilization.

[0079] In another embodiment, a time-domain resource-saving preamble-free TA synchronization device is provided. This device is used to perform the preamble-free TA synchronization method described above, including:

[0080] The TA coarse search module is used to perform a coarse search within a preset TA search range with a preset step size, and filter out M TA candidates, where M is an integer greater than 1;

[0081] The signal preprocessing module is used to receive Msg3 data frames containing known DMRS reference signals sent by user equipment, and to obtain frequency domain data corresponding to each TA candidate.

[0082] The soft combining and score calculation module is used to perform channel estimation, equalization and descrambling processing on the frequency domain data corresponding to each TA candidate, to obtain the descrambled LLR soft bits corresponding to each TA candidate, and to accumulate the absolute value of the descrambled LLR soft bits of the Msg3 data frames that are repeatedly transmitted for each TA candidate to calculate the score.

[0083] The decoding and verification module is used to sort all TA candidates from high to low according to the score, and select the N TA candidates with the highest scores for decoding and CRC verification, where N is a positive integer less than M.

[0084] The synchronization confirmation module is used to select the TA candidate that has a successful CRC check as the final synchronization TA to complete the synchronization; if the CRC check of all N selected TA candidates fails, the access synchronization is determined to have failed.

[0085] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is used as an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above.

[0086] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A time-domain resource-saving, leaderless access TA synchronization method, characterized in that, Includes the following steps: Step S1, coarse search for candidate TAs: within the preset TA search range, a coarse search is performed with a preset step size to filter out M TA candidates, where M is an integer greater than 1; Step S2, Signal preprocessing: Receive Msg3 data frames containing known DMRS reference signals sent by user equipment, and obtain frequency domain data corresponding to each TA candidate; Step S3, Parallel soft combining and score calculation: Channel estimation, equalization and descrambling are performed on the frequency domain data corresponding to each TA candidate to obtain the descrambled LLR soft bits corresponding to each TA candidate; For each TA candidate, the absolute value of the descrambled LLR soft bits of the corresponding multiple repeated transmissions of Msg3 data frames is accumulated to obtain the score of each TA candidate. Step S4, Candidate Screening and Decoding Verification: Sort all TA candidates from high to low according to their scores, and select the N TA candidates with the highest scores for decoding and CRC verification, where N is a positive integer less than M; Step S5, Synchronization Confirmation: The TA candidate that has passed the CRC check is used as the final synchronization TA to complete the data auxiliary synchronization; If the CRC check of all N selected TA candidates fails, the access synchronization is deemed to have failed.

2. The method according to claim 1, characterized in that, In step S1, the preset TA search range is 5~205, the preset step size is 10~20, and the number of the M TA candidates obtained by screening is 20.

3. The method according to claim 2, characterized in that, Step S1 specifically includes: within the TA search range, performing a coarse search with a fixed step size to obtain a set of initial TA candidate points; supplementing TA points between adjacent initial TA candidate points so that the total number of TA candidates reaches M.

4. The method according to claim 1, characterized in that, In step S2, the frequency domain data corresponding to each TA candidate is obtained, including: The received time-domain sampled signal is sliced ​​according to the time-domain position corresponding to each TA candidate to construct a two-dimensional array; The frequency domain data corresponding to all TA candidates is output at once through a single batch FFT operation.

5. The method according to claim 1, characterized in that, In step S2, the channel estimation performed for each TA candidate is batch parallel processing, including: Organize the DMRS data in the frequency domain data corresponding to each TA candidate into a unified array; By performing a single batch processing operation, the DMRS channel estimation of all TA candidates is completed in parallel, resulting in independent channel parameters for each TA candidate.

6. The method according to claim 1, characterized in that, In step S3, the score is... The calculation formula is: ， in, For the first The TA candidate, the first The 1st repeated transmission After descrambling, the LLR soft bits are used, where R is the number of times the Msg3 data frame is repeatedly transmitted. This represents the total number of LLR soft bits after descrambling.

7. A time-domain resource-saving, leaderless access TA synchronization device, characterized in that, For performing the method according to any one of claims 1 to 6, comprising: The TA coarse search module is used to perform a coarse search within a preset TA search range with a preset step size, and filter out M TA candidates, where M is an integer greater than 1; The signal preprocessing module is used to receive Msg3 data frames containing known DMRS reference signals sent by user equipment, and to obtain frequency domain data corresponding to each TA candidate. The soft combining and score calculation module is used to perform channel estimation, equalization and descrambling processing on the frequency domain data corresponding to each TA candidate, to obtain the descrambled LLR soft bits corresponding to each TA candidate, and to accumulate the absolute value of the descrambled LLR soft bits of the Msg3 data frames that are repeatedly transmitted for each TA candidate to calculate the score. The decoding and verification module is used to sort all TA candidates from high to low according to the score, and select the N TA candidates with the highest scores for decoding and CRC verification, where N is a positive integer less than M. The synchronization confirmation module is used to select the TA candidate that has a successful CRC check as the final synchronization TA to complete the synchronization; if the CRC check of all N selected TA candidates fails, the access synchronization is determined to have failed.

8. The apparatus according to claim 7, characterized in that, The signal preprocessing module includes a batch FFT submodule, which slices the received time-domain sampled signal according to the time-domain position corresponding to each TA candidate and constructs a two-dimensional array, and outputs the frequency domain data of all TA candidates at once through a single batch FFT operation.

9. The apparatus according to claim 7, characterized in that, The soft combining and scoring calculation module includes a batch channel estimation submodule, which organizes the frequency domain DMRS data of each TA candidate into a unified array, and performs channel estimation of all TA candidates in parallel through batch processing to obtain independent channel parameters for each group.

10. The apparatus according to claim 7, characterized in that, The device is applied to narrowband IoT, satellite communication or industrial IoT systems and is adapted to the synchronous processing of user equipment directly transmitting Msg3 data frames in scenarios without preamble access.

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