A method and device for estimating channel matching response noise reduction of UWB receiver

Abstract

The present invention relates to a method and device for estimating channel matching response noise reduction of a UWB receiver, wherein the method comprises: obtaining a coherent cumulative output signal; obtaining an initial noise floor power for the coherent cumulative output signal, and obtaining a noise threshold based on the initial noise floor power; extracting a noise signal in the coherent cumulative output signal according to the noise threshold, and obtaining a noise floor power for the extracted noise signal in the coherent cumulative output signal, and obtaining a new noise threshold based on the noise floor power; judging whether the number of iterations has been reached, if the number of iterations has been reached, proceeding to the next step, otherwise returning to the previous step; marking the part of the coherent cumulative output signal that exceeds the noise threshold as a useful signal; and setting the unmarked signal in the coherent cumulative output signal to zero. The present invention can accurately approximate the noise variance estimation.

Description

Technical Field

[0001] The present invention relates to the technical field of channel matching response, and in particular to a method and device for estimating the noise reduction of a UWB receiver channel matching response. Background Art

[0002] The UWB system is a communication system that uses nanosecond-width pulses as chips. Due to the short duration and large bandwidth of UWB pulses, it has excellent ability to distinguish multipath signals. Therefore, in complex environments such as indoors, the flight time of its electromagnetic waves can be accurately measured (centimeter level) and used for high-precision ranging and positioning. The bandwidth of the UWB system is generally above 500MHz, and the ADC sampling frequency is usually at least 1GHz.

[0003] The UWB preamble signal is composed of a pseudo-random code sequence (PRN) that is periodically and repeatedly transmitted by the above-mentioned pulse modulation, and each such modulated pseudo-random code sequence is called a preamble. The PRN used in the UWB preamble has a perfect cyclic autocorrelation characteristic, that is, when the time difference between the two functions involved in the correlation operation (both are the PRNs used themselves) is 0, it has the maximum correlation peak, otherwise it is 0; the selection of such a PRN combined with large-bandwidth pulse modulation reduces multipath interference to an extremely low level, which is extremely beneficial to improving the estimation performance of the electromagnetic wave arrival time (TOA), and greatly simplifies the channel estimation algorithm. In general, the carefully designed UWB preamble greatly reduces the complexity of the UWB receiver design and improves the performance of the UWB ranging and positioning system. According to the UWB physical layer protocol, the length of the PRN used in the UWB preamble is 31 or 127. After zero insertion (zero insertion ratio is 4, 16 or 64), the actual length of the preamble sequence obtained will be doubled. For example, after 16 times zero insertion of the PRN with a length of 31, the final preamble sequence length increases to 16 times, that is, 496. The possible values ​​of the sequence are {1, 0, -1}, each value corresponds to a code chip, and each code chip is modulated by a selected narrow pulse (usually a Gaussian pulse) to obtain the preamble code; and the UWB preamble signal can be composed of 16, 64, 1024 or 4096 consecutive preamble codes. The UWB receiver needs to complete the detection and channel parameter estimation of the preamble signal, and then realize the ranging positioning and subsequent data demodulation and decoding. The current UWB receiver processes the preamble signal in two stages: the capture stage and the tracking stage. In the initial signal capture stage, it is necessary to determine the existence of the preamble code. Once the preamble code is confirmed to exist, the receiver enters the signal tracking stage. In the tracking phase, the receiver needs to compensate for the frequency offset and resample the ADC data to synchronize the local signal with the received signal, creating conditions for subsequent correlation processing and coherent accumulation to obtain coherent gain. After the receiver completes the reception of all preamble codes, it processes the CMR (channel matching response) represented by the accumulated data to estimate the TOA (time of arrival) of the signal. CMR is used for multipath combining and matching reception for subsequent data demodulation. However, the existing CMR estimation not only fails to effectively exclude useful signals, but also does not undergo noise reduction processing, resulting in more noise components, which reduces the data decoding signal-to-noise ratio and affects the accuracy of subsequent channel estimation. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method and device for estimating the noise reduction of a UWB receiver channel matching response, which can accurately approximate the noise variance estimation.

[0005] The technical solution adopted by the present invention to solve the technical problem is: to provide a UWB receiver channel matching response noise reduction estimation method, comprising the following steps:

[0006] Acquire a coherent accumulation output signal;

[0007] Obtaining an initial noise floor power for the coherent accumulation output signal, and obtaining a noise threshold based on the initial noise floor power;

[0008] Extracting a noise signal from the coherent accumulation output signal according to the noise threshold, obtaining a noise floor power for the extracted noise signal from the coherent accumulation output signal, and obtaining a new noise threshold based on the noise floor power;

[0009] Determine whether the number of iterations has been reached. If so, proceed to the next step, otherwise return to the previous step.

[0010] Mark the part of the coherent accumulation output signal that exceeds the noise threshold as a useful signal;

[0011] Set the unmarked signals in the coherent accumulation output signal to zero.

[0012] The extracting the noise signal in the coherent accumulation output signal according to the noise threshold comprises:

[0013] The coherent accumulation output signal is compared with a noise threshold, a portion less than or equal to the noise threshold is selected from the coherent accumulation output signal, and the selected portion is used as a noise signal.

[0014] The step of obtaining the noise floor power of the noise signal extracted from the coherent accumulation output signal is specifically to obtain the noise floor power of the signal based on the energy average of the signal or the modulus average of the signal.

[0015] The number of iterations is 3 times.

[0016] After marking the part of the coherent accumulation output signal exceeding the noise threshold as a useful signal, the method further includes: marking the first and last G signal points marked as the useful signal as useful signals.

[0017] The technical solution adopted by the present invention to solve the technical problem is: a UWB receiver channel matching response noise reduction estimation device, comprising:

[0018] An acquisition module, used for acquiring a coherent accumulation output signal;

[0019] A first noise threshold acquisition module, configured to obtain an initial noise floor power for the coherent accumulation output signal, and obtain a noise threshold based on the initial noise floor power;

[0020] A second noise threshold acquisition module, used to extract the noise signal in the coherent accumulation output signal according to the noise threshold, obtain the noise floor power of the extracted noise signal in the coherent accumulation output signal, and obtain a new noise threshold based on the noise floor power;

[0021] A judging module, used to judge whether the number of iterations has been reached, if so, entering the marking module, otherwise returning to the second noise threshold acquisition module;

[0022] A marking module, used for marking the part of the noise threshold in the coherent accumulation output signal as a useful signal;

[0023] The zeroing module is used for setting the unmarked signal in the coherent accumulation output signal to zero.

[0024] When extracting the noise signal in the coherent accumulation output signal according to the noise threshold, the second noise threshold acquisition module compares the coherent accumulation output signal with the noise threshold, selects a part less than or equal to the noise threshold from the coherent accumulation output signal, and uses the selected part as the noise signal.

[0025] When obtaining the noise floor power of the noise signal extracted from the coherent accumulation output signal, the second noise threshold acquisition module obtains the noise floor power of the signal based on the energy average of the signal or the modulus average of the signal.

[0026] The number of iterations is 3 times.

[0027] The UWB receiver channel matching response noise reduction estimation device further comprises: a retaining mark module, which is used to mark the first and last G signal points marked as useful signals as useful signals.

[0028] Beneficial Effects

[0029] Due to the adoption of the above technical solution, the present invention has the following advantages and positive effects compared with the prior art: the present invention adopts an iterative method to accurately approximate the noise variance estimation, so that the estimation result is less affected by the useful signal. The present invention also retains part of the tail signal as a useful signal to improve the data demodulation performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is the basic processing flow chart of UWB preamble signal;

[0031] Figure 2 It is a flow chart of a channel matching response noise reduction estimation method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0032] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0033] Figure 1 The figure shows the basic processing flow of UWB Preamble signal. First, the UWB electromagnetic wave received by the antenna is processed by the RF (radio frequency) front end, and then converted into a discrete digital signal suitable for processing by digital ASIC, DSP or FPGA by ADC sampling. Next, the preamble sequence reproduced locally is convolved to improve the signal-to-noise ratio and prepare for further signal processing and parameter estimation. The estimation of TOA and CMR requires a higher signal-to-noise ratio to be reliable and accurate, that is, a longer coherent accumulation time is required. The UWB physical layer standard stipulates that the maximum frequency difference allowed is 20ppm. Taking the carrier frequency of 7987.2MHz as an example, the frequency deviation can be as high as about 160kHz. Exceeding the coherent integration length may cause the result to suffer a large attenuation. In addition, the frequency deviation will also cause the sampling clock difference between the transmitting and receiving ends, which also limits the coherent accumulation time. For this reason, frequency deviation and sampling clock phase compensation need to be performed after the Preamble convolution. After further coherent accumulation to obtain the desired signal-to-noise ratio, the noise floor and CMR estimation are performed.

[0034] The embodiment of the present invention relates to a method for estimating a channel matching response of a UWB receiver with noise reduction, such as Figure 2 As shown, the following steps are included:

[0035] Step 1: Obtain a coherent accumulation output signal. For ease of description, this embodiment represents the coherent accumulation output signal as: S(n), k∈[0, M-1], where M is the selected signal window width.

[0036] Step 2: Calculate the initial noise floor power of the coherent accumulation output signal, and obtain the noise threshold based on the initial noise floor power. In this embodiment, the initial noise floor power N is calculated by the average energy of the signal. 0 , expressed as: N 0 =Mean(S(i) 2 ), noise threshold TH 0 = rN 0 , r is the preset relative threshold value.

[0037] Step 3: extract the noise signal in the coherent accumulation output signal according to the noise threshold, obtain the noise floor power of the extracted noise signal in the coherent accumulation output signal, and obtain a new noise threshold based on the noise floor power.

[0038] The method of extracting the noise signal from the coherent accumulation output signal according to the noise threshold is as follows: extracting the noise signal from the coherent accumulation output signal and the noise threshold TH 0 Compare and select the signal that is less than or equal to the noise threshold TH from the coherent accumulation output signal 0Then, the noise floor power N is calculated by extracting the noise signal in the coherent accumulation output signal through the average energy of the signal. 1 , expressed as: At this time, the noise floor power N 1 Get the new noise threshold TH 1 = rN 1 .

[0039] Step 4: Determine whether the number of iterations has been reached. If the number of iterations has been reached, proceed to step 5, otherwise return to step 3. Specifically, if the number of iterations has not been reached at this time, repeat step 3 to obtain the noise floor power New noise threshold TH 2 = rN 2 , if the number of iterations is reached at this time, go to step 5.

[0040] Step 5: The coherent accumulation output signal exceeding the noise threshold TH 2 The part is marked as useful signal, namely:

[0041]

[0042] Step 6: Mark the first and last G signal points marked as useful signals as useful signals. This step is to expand the signal points marked in step 5, that is, Among them, G is the preset field width.

[0043] Step 7, set the unmarked signal in the coherent accumulation output signal to zero, so that CMR can be

[0044]

[0045] It is worth mentioning that in this implementation, the noise threshold can also be obtained by modulus averaging, which is very close to the principle and effect of energy averaging and can be selected according to specific applications. When the number of iterations of the noise threshold is three, it can usually converge to a sufficiently accurate value, and the computational complexity is acceptable. If it still cannot converge after three times, the number of iterations can be greater than three.

[0046] The embodiment of the present invention also relates to a UWB receiver channel matching response noise reduction estimation device, comprising:

[0047] An acquisition module, used for acquiring a coherent accumulation output signal;

[0048] A first noise threshold acquisition module, configured to obtain an initial noise floor power for the coherent accumulation output signal, and obtain a noise threshold based on the initial noise floor power;

[0049] A second noise threshold acquisition module, used to extract the noise signal in the coherent accumulation output signal according to the noise threshold, obtain the noise floor power of the extracted noise signal in the coherent accumulation output signal, and obtain a new noise threshold based on the noise floor power;

[0050] A judging module, used to judge whether the number of iterations has been reached, if so, entering the marking module, otherwise returning to the second noise threshold acquisition module;

[0051] A marking module, used for marking the part of the noise threshold in the coherent accumulation output signal as a useful signal;

[0052] The zeroing module is used for setting the unmarked signal in the coherent accumulation output signal to zero.

[0053] When extracting the noise signal in the coherent accumulation output signal according to the noise threshold, the second noise threshold acquisition module compares the coherent accumulation output signal with the noise threshold, selects a part less than or equal to the noise threshold from the coherent accumulation output signal, and uses the selected part as the noise signal.

[0054] When obtaining the noise floor power of the noise signal extracted from the coherent accumulation output signal, the second noise threshold acquisition module obtains the noise floor power of the signal based on the energy average of the signal or the modulus average of the signal.

[0055] The number of iterations is 3 times.

[0056] The UWB receiver channel matching response noise reduction estimation device further comprises: a retaining mark module, which is used to mark the first and last G signal points marked as useful signals as useful signals.

[0057] The estimation of noise variance is crucial for selecting useful signals in CMR estimation, but UWB multipath signals may have a large dynamic range. If the noise energy is simply estimated by averaging the energy of all signals (noise and useful signals), the noise variance estimation will be too large. Therefore, the present embodiment adopts an iterative method to accurately approximate the noise variance estimation, and the estimation result is little affected by the useful signal. Since the UWB transmitted pulse signal has a long tail, part of the tail of the received pulse signal will be submerged by noise and cannot be identified by amplitude alone. As a useful signal, this part of the tail is also useful for subsequent data information matching reception. Therefore, the present embodiment retains this part of the tail signal, thereby improving data demodulation performance.

Claims

1. A method for estimating the channel matching response of a UWB receiver with noise reduction. It is characterized in that The following steps are involved: Acquire a coherent accumulation output signal; Obtaining a noise floor power for the coherent accumulation output signal, and obtaining a noise threshold based on the noise floor power; Extracting a noise signal from the coherent accumulation output signal according to the noise threshold, obtaining a noise floor power for the extracted noise signal from the coherent accumulation output signal, and obtaining a new noise threshold based on the noise floor power; Determine whether the number of iterations has been reached. If so, proceed to the next step, otherwise return to the previous step. Mark the part of the coherent accumulation output signal that exceeds the noise threshold as a useful signal; Set the unmarked signals in the coherent accumulation output signal to zero.

2. The UWB receiver channel matching response noise reduction estimation method according to claim 1, It is characterized in that The extracting the noise signal in the coherent accumulation output signal according to the noise threshold comprises: The coherent accumulation output signal is compared with a noise threshold, a portion less than or equal to the noise threshold is selected from the coherent accumulation output signal, and the selected portion is used as a noise signal.

3. The UWB receiver channel matching response noise reduction estimation method according to claim 1, It is characterized in that The step of obtaining the noise floor power of the noise signal extracted from the coherent accumulation output signal is specifically to obtain the noise floor power of the signal based on the energy average of the signal or the modulus average of the signal.

4. The UWB receiver channel matching response noise reduction estimation method according to claim 1, It is characterized in that The number of iterations is 3 times.

5. The UWB receiver channel matching response noise reduction estimation method according to claim 1, It is characterized in that After marking the part of the coherent accumulation output signal exceeding the noise threshold as a useful signal, the method further includes: marking the first and last G signal points marked as the useful signal as useful signals, wherein G is a preset field width.

6. A UWB receiver channel matching response noise reduction estimation device, It is characterized in that include: An acquisition module, used for acquiring a coherent accumulation output signal; A first noise threshold acquisition module, configured to obtain a noise floor power for the coherent accumulation output signal, and obtain a noise threshold based on the noise floor power; A second noise threshold acquisition module, used to extract the noise signal in the coherent accumulation output signal according to the noise threshold, obtain the noise floor power of the extracted noise signal in the coherent accumulation output signal, and obtain a new noise threshold based on the noise floor power; A judging module, used to judge whether the number of iterations has been reached, if so, entering the marking module, otherwise returning to the second noise threshold acquisition module; A marking module, used for marking the part of the coherent accumulation output signal exceeding the noise threshold as a useful signal; The zeroing module is used for setting the unmarked signal in the coherent accumulation output signal to zero.

7. The UWB receiver channel matching response noise reduction estimation device according to claim 6, It is characterized in that When extracting the noise signal in the coherent accumulation output signal according to the noise threshold, the second noise threshold acquisition module compares the coherent accumulation output signal with the noise threshold, selects a part less than or equal to the noise threshold from the coherent accumulation output signal, and uses the selected part as the noise signal.

8. The UWB receiver channel matching response noise reduction estimation device according to claim 6, It is characterized in that When obtaining the noise floor power of the noise signal extracted from the coherent accumulation output signal, the second noise threshold acquisition module obtains the noise floor power of the signal based on the energy average of the signal or the modulus average of the signal.

9. The UWB receiver channel matching response noise reduction estimation device according to claim 6, It is characterized in that The number of iterations is 3 times.

10. The UWB receiver channel matching response noise reduction estimation device according to claim 6, It is characterized in that Also includes: The retaining marking module is used to mark the first and last G signal points marked as useful signals as useful signals, wherein G is a preset field width.

Images