A method and apparatus for ultra-wideband signal acquisition and frequency offset computation

Abstract

This invention relates to a method and apparatus for ultra-wideband signal acquisition and frequency offset calculation. The method includes: receiving sampled data containing N consecutive symbols; dividing each symbol in the sampled data into m sampled data sequences to obtain N groups of m sampled data sequences; sequentially inputting the N groups of m sampled data sequences into corresponding m correlators; performing correlation operations between the m sampled data sequences and a standard preamble sequence; and accumulating the outputs of the m correlators to obtain the correlation energy; accumulating the despread correlation results of the N consecutive symbols; and determining whether the preamble has been successfully acquired based on the peak value of the accumulated energy; and calculating the frequency offset based on the m sample points with the largest sum of energy in the symbols after successful preamble acquisition. This invention can optimize chip resources and reduce chip power consumption and cost without sacrificing performance.

Description

Technical Field

[0001] This invention relates to ultra-wideband reception technology in the field of communication technology, and in particular to an ultra-wideband signal acquisition and frequency offset calculation method and apparatus. Background Technology

[0002] Ultra-wideband (UWB) systems are communication systems that use nanosecond-level pulses as symbols. Due to their short pulses and large bandwidth, they have excellent capabilities in distinguishing multipath signals. Even in complex environments such as indoors, they can accurately measure the time of flight of electromagnetic waves, enabling high-precision ranging and positioning. The bandwidth of a UWB system is typically above 500MHz, and the receiver's ADC sampling frequency is generally the Nyquist sampling frequency, i.e., 1GHz.

[0003] The UWB preamble is a pseudo-random code sequence that is periodically and repeatedly transmitted. The preamble length can be 31, 91, or 127. When the preamble length is 127, the symbol time is 1017.63 ns. Since the ADC sampling frequency is 1 GHz, one symbol of the preamble can contain up to 1016 sampling points. The UWB receiver needs to acquire and track the preamble to obtain information such as frequency offset, code offset, and channel impulse response.

[0004] During preamble despreading and acquisition, performing 1016 correlation calculations with the standard preamble using 1016 sampling points can capture the preamble signal transmitted by the transmitter. Current schemes use 1016 storage units to store the 1016 correlation results. After accumulating N symbols to obtain the gain, the point of maximum correlation energy is located for decision-making to determine whether the preamble acquisition was successful. Based on this, the strongest path is used to calculate the frequency offset. The peak sampling points corresponding to adjacent symbols are multiplied by conjugate, and this operation is repeated for N symbols. The correlation results are accumulated, and the phase of the accumulated value is the frequency offset. Because this scheme requires 1016 storage units for preamble spread spectrum acquisition, it consumes significant resources and involves a large computational load. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method and apparatus for ultra-wideband signal acquisition and frequency offset calculation, which can optimize the resources required by the chip and reduce chip power consumption and cost without sacrificing performance.

[0006] The technical solution adopted by this invention to solve its technical problem is: to provide an ultra-wideband signal acquisition and frequency offset calculation method, comprising the following steps:

[0007] Receive sampled data containing N consecutive symbols, divide each symbol in the sampled data into m sampled data sequences, and obtain N groups of m sampled data sequences;

[0008] The N sets of m sampled data sequences are sequentially input into the corresponding m correlators. Correlation operations are performed on the m sampled data sequences and the standard preamble sequence. The outputs of the m correlators are then summed to obtain the correlation energy. Specifically, after the calculation is completed for a set of m sampled data sequences, L / m correlation energies are obtained. These L / m correlation energies are used as the despread correlation result of one symbol. After the calculation is completed for N sets of m sampled data sequences, N symbols of despread correlation results are obtained, where L is the data length of one symbol.

[0009] The despreading correlation results of N consecutive symbols are accumulated, and the preamble is determined to be successfully captured based on the energy peak value after accumulation.

[0010] After the preamble is successfully captured, the frequency offset is calculated based on the m sampling points with the largest sum of energy in the symbol.

[0011] When each symbol in the sampled data is divided into m sampled data sequences, the i-th sampled point sequence is composed of the i-th, m+i, 2m+i, ..., (L / m-1)m+i sampled points.

[0012] The step of determining whether the preamble has been successfully captured based on the accumulated energy peak value specifically includes:

[0013] Calculate the ratio of the accumulated peak energy to the mean of all samples excluding the peak energy;

[0014] When the ratio exceeds the set threshold, the preamble is successfully captured.

[0015] The frequency offset calculation based on the m sampling points with the largest sum of energy in the symbol is specifically as follows:

[0016] Based on the m sampling points with the largest sum of energy in the symbols obtained when the preamble is successfully captured, determine the sampling points in each symbol corresponding to the m sampling points with the largest sum of energy;

[0017] Multiply the sampling points corresponding to the N adjacent symbols by conjugate to obtain m sets of N-1 complex number results;

[0018] The phase of the accumulated N-1 complex number results is the frequency offset.

[0019] The technical solution adopted by this invention to solve its technical problem is: to provide an ultra-wideband signal acquisition and frequency offset calculation device, comprising:

[0020] The receiving and dividing module is used to receive sampled data containing N consecutive symbols, divide each symbol in the sampled data into m sampled data sequences, and obtain N groups of m sampled data sequences;

[0021] The preamble despreading module is used to sequentially input the N groups of m sampled data sequences into the corresponding m correlators, perform correlation operations on the m sampled data sequences and the standard preamble sequence, and accumulate the output results of the m correlators to obtain the correlation energy; wherein, after the calculation is completed for a group of m sampled data sequences, a group of L / m correlation energies is obtained, and the L / m correlation energies are used as the despreading correlation result of one symbol; after the calculation is completed for N groups of m sampled data sequences, the despreading correlation result of N symbols is obtained, where L is the data length of one symbol;

[0022] The preamble acquisition module is used to accumulate the despreading correlation results of N consecutive symbols and determine whether the preamble has been successfully acquired based on the energy peak value after accumulation.

[0023] The frequency offset calculation module is used to calculate the frequency offset based on the m sampling points with the largest sum of energy in the symbol after the preamble is successfully captured.

[0024] When the receiving and dividing module divides each symbol in the sampled data into m sampled data sequences, the i-th sampled data sequence is composed of the i-th, m+i, 2m+i, ..., (L / m-1)m+i sampled points.

[0025] The preamble capture module includes:

[0026] The calculation unit is used to calculate the ratio of the accumulated energy peak to the mean of all samples except the energy peak.

[0027] The determination unit is used to determine that the preamble has been successfully captured when the ratio exceeds a set threshold.

[0028] The frequency offset calculation module includes:

[0029] The determining unit is used to determine the sampling point in each symbol corresponding to the m sampling points with the largest sum of energy in the symbols obtained when the preamble is successfully captured;

[0030] The complex number calculation unit is used to perform conjugate multiplication on the sampling points corresponding to N adjacent symbols to obtain m sets of N-1 complex number results;

[0031] The accumulation calculation unit is used to accumulate m groups of N-1 complex number results, and the phase of the accumulated result is the frequency offset.

[0032] Beneficial effects

[0033] By employing the aforementioned technical solution, this invention offers the following advantages and positive effects compared to existing technologies: This invention reduces the number of storage units in the preamble despreading acquisition process to one-mth of that in existing schemes by first accumulating the correlator output results and then storing them. Due to factors such as multipath effects in real-world scenarios, signal analysis needs to be performed within a certain range of sampling points. The main task of the preamble acquisition stage is to determine the main energy region in the channel impulse response, apply a window to this region, and subsequently process the sampling points within the window. This invention does not affect the accuracy of the windowing; therefore, the processing method of this invention does not reduce the performance of preamble acquisition but effectively reduces the chip area, power consumption, and production cost. Simultaneously, the frequency offset calculation method used in conjunction with this despreading acquisition algorithm has greater gain. Attached Figure Description

[0034] Figure 1 This is a flowchart of the first embodiment of the present invention;

[0035] Figure 2 This is a schematic diagram of the despreading algorithm for a symbol in the first embodiment of the present invention;

[0036] Figure 3 This is a schematic diagram of frequency offset calculation in the first embodiment of the present invention. Detailed Implementation

[0037] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0038] The first embodiment of the present invention relates to a method for ultra-wideband signal acquisition and frequency offset calculation, such as... Figure 1 As shown, it includes the following steps:

[0039] Receive sampled data containing N consecutive symbols, divide each symbol in the sampled data into m sampled data sequences, and obtain N groups of m sampled data sequences;

[0040] The N sets of m sampled data sequences are sequentially input into the corresponding m correlators. Correlation operations are performed on the m sampled data sequences and the standard preamble sequence. The outputs of the m correlators are then summed to obtain the correlation energy. Specifically, after the calculation is completed for a set of m sampled data sequences, L / m correlation energies are obtained. The L / m correlation energies are used as the despread correlation result of a symbol. After the calculation is completed for N sets of m sampled data sequences, the despread correlation result of N symbols is obtained, where L is the data length of a symbol.

[0041] Since the preamble sequence is sent cyclically and repeatedly, new data is constantly entering the correlator. Each sampled data sequence appears to be cyclically shifted. After cyclically shifting L / m times, it returns to the initial state, completing the despreading of one symbol. After N sets of m sampled data sequences, the despreading results of N symbols can be obtained.

[0042] The despreading correlation results of N consecutive symbols are accumulated, and the preamble is determined to be successfully captured based on the energy peak value after accumulation.

[0043] After the preamble is successfully acquired, the frequency offset is calculated based on the m sampling points with the largest sum of energy in the symbol.

[0044] The primary goal of UWB receiver preamble acquisition is to detect the presence of a UWB preamble being transmitted using a low-power algorithm. This implementation detects preamble transmission by calculating the correlation energy between the sampled data sequence and the standard preamble sequence. The correlation energy is calculated as follows: Figure 2 As shown, assuming the current preamble length is 127, a symbol can contain a maximum of 1016 sampling points. In this embodiment, since the ADC frequency is relatively high at 1GHz, the correlator uses a 125MHz clock, requiring a multiphase correlator architecture for parallel processing. Eight correlators are used, each with a length of 127 (1016 / 8), the same as the preamble length. The 1st, 9th, 17th, ..., 1009th sampling points are grouped into a sampling point sequence of length 127. Similarly, the 2nd, 10th, 18th, ..., 1010th sampling points are grouped into another sampling point sequence of length 127, resulting in eight sampling data sequences per symbol. The correlators perform correlation operations between the sampling data sequences and the standard preamble sequence to obtain the correlation energy value. The correlation energy values ​​output by the eight correlators are accumulated and stored in the memory unit. Despreading a symbol outputs 127 correlation energy values, requiring only 127 sets of memory units.

[0045] Therefore, this embodiment processes the correlation results output by the correlator and stores them after accumulating every 8 correlation results, requiring only 127 sets of storage units. The required resources are reduced to one-eighth of the existing solutions. At the same time, finding the peak value among 127 correlation results requires less work than finding the peak value among 1016 correlation results.

[0046] The receiver continuously despreads N symbols. Since the preamble is periodically repeated, periodic pulse peaks are obtained after despreading. Considering that a single pulse may be submerged by noise, the pulse signals can be periodically superimposed, that is, the despreading results of N symbols are accumulated, thus obtaining a sharper pulse, which helps the receiver make a more sensitive decision. The data in the accumulator (the modulus of the despread data) is equivalent to the magnitude of the channel's impulse response to the pulse. When the ratio of the accumulated peak energy to the mean of all samples excluding the peak energy exceeds a set threshold, the preamble is considered to have been successfully acquired. The selection of the threshold needs to consider the performance of the ADC and the noise level to ensure a reasonable false positive rate and false negative rate.

[0047] Due to multipath effects, the main energy of the received signal is concentrated in a certain range of sampling points. Therefore, the task of the acquisition stage is to determine the main energy region in the channel impulse response, and to frame the main energy region using a sample window of a certain length. Subsequent processing mainly focuses on the sampling points within the window. The energy calculation method in this embodiment does not affect the accuracy of windowing, thus it does not reduce the signal acquisition capability, effectively reducing chip resource consumption while maintaining lossless performance.

[0048] The UWB receiver in this embodiment can employ a zero-IF (zero intermediate frequency) architecture, controlling a fixed frequency difference between the transmitting and receiving ends. When the receiver's ADC samples the signal at a fixed sampling frequency, the sampling points will slowly shift within the periodically repeating preamble sequence. After the receiver confirms that the preamble reception is complete, it can estimate the frequency offset between the transmitting and receiving ends. The frequency offset is calculated as follows: Figure 3 As shown, by despreading and capturing the transmitted signal, the eight sampling points with the strongest energy in the symbol can be obtained. The peak sampling points corresponding to adjacent symbols are multiplied by their conjugates, and the phase of the correlation result is the frequency offset Δφ between symbols. Sampling point 1 undergoes (N-1) complex multiplication operations, and then these (N-1) complex results are added together to obtain ADD1. Similarly, ADD2 to ADD8 are obtained. Compared to taking the modulus of ADD1 to ADD8 to find the strongest path, this implementation accumulates ADD1 to ADD8 to obtain the multipath merging benefit. This method has a smaller computational load and consumes fewer resources; the phase of the accumulated value is the frequency offset.

[0049] Regarding frequency offset calculation, corresponding to the aforementioned preamble despreading acquisition algorithm, this embodiment proposes a frequency offset calculation method with relatively low computational cost. Based on the m sampling points with the largest energy sum obtained when the preamble is successfully acquired, the sampling points corresponding to the m sampling points with the largest energy sum in each symbol are determined. Complex multiplication is then performed on the sampling points corresponding to the N adjacent symbols, and all results are accumulated to obtain the multipath merging gain of the strongest energy point. The phase of the accumulated value is the frequency offset. This calculation method consumes relatively few resources.

[0050] A second embodiment of the present invention relates to an ultra-wideband signal acquisition and frequency offset calculation device, comprising:

[0051] The receiving and dividing module is used to receive sampled data containing N consecutive symbols, divide each symbol in the sampled data into m sampled data sequences, and obtain N groups of m sampled data sequences;

[0052] The preamble despreading module is used to sequentially input the N groups of m sampled data sequences into the corresponding m correlators, perform correlation operations on the m sampled data sequences and the standard preamble sequence, and accumulate the output results of the m correlators to obtain the correlation energy; wherein, after the calculation is completed for a group of m sampled data sequences, a group of L / m correlation energies is obtained, and the L / m correlation energies are used as the despreading correlation result of one symbol; after the calculation is completed for N groups of m sampled data sequences, the despreading correlation result of N symbols is obtained, where L is the data length of one symbol;

[0053] The preamble acquisition module is used to accumulate the despreading correlation results of N consecutive symbols and determine whether the preamble has been successfully acquired based on the energy peak value after accumulation.

[0054] The frequency offset calculation module is used to calculate the frequency offset based on the m sampling points with the largest sum of energy in the symbol after the preamble is successfully captured.

[0055] When the receiving and dividing module divides each symbol in the sampled data into m sampled data sequences, the i-th sampled data sequence is composed of the i-th, m+i, 2m+i, ..., (L / m-1)m+i sampled points.

[0056] The preamble capture module includes:

[0057] The calculation unit is used to calculate the ratio of the accumulated energy peak to the mean of all samples except the energy peak.

[0058] The determination unit is used to determine that the preamble has been successfully captured when the ratio exceeds a set threshold.

[0059] The frequency offset calculation module includes:

[0060] The determining unit is used to determine the sampling point in each symbol corresponding to the m sampling points with the largest sum of energy in the symbols obtained when the preamble is successfully captured;

[0061] The complex number calculation unit is used to perform conjugate multiplication on the sampling points corresponding to N adjacent symbols to obtain m sets of N-1 complex number results;

[0062] The accumulation calculation unit is used to accumulate m groups of N-1 complex number results, and the phase of the accumulated result is the frequency offset.

[0063] It is easy to see that this invention reduces the number of storage units in the preamble despreading acquisition process to 1 / m of that in existing schemes by first accumulating the correlator output results and then storing them. Due to factors such as multipath effects in real-world scenarios, signal analysis needs to be performed within a certain range of sampling points. The main task of the preamble acquisition stage is to determine the main energy region in the channel impulse response, apply a window to this region, and subsequently process the data from the sampling points within the window. This invention does not affect the accuracy of the windowing, therefore it does not reduce the performance of preamble acquisition, but effectively reduces the chip area, power consumption, and production cost. Simultaneously, the frequency offset calculation method used in conjunction with this despreading acquisition algorithm has greater gain.

Claims

1. A method for ultra-wideband signal acquisition and frequency offset calculation, characterized in that, Includes the following steps: Receive sampled data containing N consecutive symbols, divide each symbol in the sampled data into m sampled data sequences, and obtain N groups of m sampled data sequences; The N sets of m sampled data sequences are sequentially input into the corresponding m correlators. Correlation operations are performed on the m sampled data sequences and the standard preamble sequence. The outputs of the m correlators are then summed to obtain the correlation energy. Specifically, after the calculation is completed for a set of m sampled data sequences, L / m correlation energies are obtained. These L / m correlation energies are used as the despread correlation result of one symbol. After the calculation is completed for N sets of m sampled data sequences, N symbols of despread correlation results are obtained, where L is the data length of one symbol. The despreading correlation results of N consecutive symbols are accumulated, and the preamble is determined to be successfully captured based on the energy peak value after accumulation. After the preamble is successfully captured, the frequency offset is calculated based on the m sampling points with the largest sum of energy in the symbol.

2. The ultra-wideband signal acquisition and frequency offset calculation method according to claim 1, characterized in that, When dividing each symbol in the sampled data into m sampled data sequences, the i-th sampled data sequence is composed of the i-th, It consists of m+i, 2m+i, ..., (L / m-1)m+i sampling points.

3. The ultra-wideband signal acquisition and frequency offset calculation method according to claim 1, characterized in that, The step of determining whether the preamble has been successfully captured based on the accumulated energy peak value specifically includes: Calculate the ratio of the accumulated peak energy to the mean of all samples excluding the peak energy; When the ratio exceeds the set threshold, the preamble is successfully captured.

4. The ultra-wideband signal acquisition and frequency offset calculation method according to claim 1, characterized in that, The frequency offset calculation based on the m sampling points with the largest sum of energy in the symbol is specifically as follows: Based on the m sampling points with the largest sum of energy in the symbols obtained when the preamble is successfully captured, determine the sampling points in each symbol corresponding to the m sampling points with the largest sum of energy; Multiply the sampling points corresponding to the N adjacent symbols by conjugate to obtain m sets of N-1 complex number results; The phase of the sum of m groups of N-1 complex number results is the frequency offset.

5. A device for ultra-wideband signal acquisition and frequency offset calculation, characterized in that, include: The receiving and dividing module is used to receive sampled data containing N consecutive symbols, divide each symbol in the sampled data into m sampled data sequences, and obtain N groups of m sampled data sequences; The preamble despreading module is used to sequentially input the N groups of m sampled data sequences into the corresponding m correlators, perform correlation operations on the m sampled data sequences and the standard preamble sequence, and accumulate the output results of the m correlators to obtain the correlation energy; wherein, after the calculation is completed for a group of m sampled data sequences, a group of L / m correlation energies is obtained, and the L / m correlation energies are used as the despreading correlation result of one symbol; after the calculation is completed for N groups of m sampled data sequences, the despreading correlation result of N symbols is obtained, where L is the data length of one symbol; The preamble acquisition module is used to accumulate the despreading correlation results of N consecutive symbols and determine whether the preamble has been successfully acquired based on the energy peak value after accumulation. The frequency offset calculation module is used to calculate the frequency offset based on the m sampling points with the largest sum of energy in the symbol after the preamble is successfully captured.

6. The ultra-wideband signal acquisition and frequency offset calculation device according to claim 5, characterized in that, When the receiving and dividing module divides each symbol in the sampled data into m sampled data sequences, the i-th sampled data sequence is composed of the i-th, m+i, 2m+i, ..., (L / m-1)m+i sampled points.

7. The ultra-wideband signal acquisition and frequency offset calculation device according to claim 5, characterized in that, The preamble capture module includes: The calculation unit is used to calculate the ratio of the accumulated energy peak to the mean of all samples except the energy peak. The determination unit is used to determine that the preamble has been successfully captured when the ratio exceeds a set threshold.

8. The ultra-wideband signal acquisition and frequency offset calculation device according to claim 5, characterized in that, The frequency offset calculation module includes: The determining unit is used to determine the sampling point in each symbol corresponding to the m sampling points with the largest sum of energy in the symbols obtained when the preamble is successfully captured; The complex number calculation unit is used to perform conjugate multiplication on the sampling points corresponding to N adjacent symbols to obtain m sets of N-1 complex number results; The accumulation calculation unit is used to accumulate m groups of N-1 complex number results. The phase of the accumulated result is the frequency offset.

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