A Blind Amplitude Estimation Method for 8PSK Burst Signal

Abstract

A method for blindly estimating the amplitude of an 8PSK burst signal relates to a parameter estimation technology for a burst signal. The estimation method comprises the following steps: S100, determining the number of 8PSK symbols used for amplitude estimation, that is, determining the value of L; S200, sequentially inputting the 8PSK symbol sequence #imgabs0# that has completed timing synchronization, frequency synchronization and phase synchronization into an amplitude estimator, and iteratively calculating an intermediate parameter p1[L]; S300, calculating the intermediate parameter p2: #imgabs1# S400, calculating the intermediate parameter p3: p3=|p2|; S500, calculating the amplitude estimation value #imgabs2##imgabs3#. Only 8PSK modulation symbols are used for amplitude estimation without any pilot assistance. By adjusting the number of 8PSK symbols involved in amplitude estimation, the estimation performance and estimation delay can be weighed; compared with the DA-MLE method, under the condition of equal estimation performance, the estimation delay is smaller; under the condition of equal estimation delay, the estimation performance is better.

Description

Technical Field

[0001] The invention relates to the technical field of digital communication, in particular to a parameter estimation technology of a burst signal, and specifically to an amplitude blind estimation method of an 8PSK burst signal. Background Art

[0002] In the return link burst communication receiver of the MF-TDMA satellite communication system, at least two digital automatic gain controllers (DAGCs) are required to adjust the signal amplitude to meet the requirements of the subsequent signal processing module. One is DAGC1 located between the matched filter and the timing, frequency and phase synchronization module (hereinafter referred to as the synchronization module), and the other is DAGC2 located between the synchronization module and the soft demapping module. Figure 1 The typical distribution of digital automatic gain controllers in burst communication receivers is demonstrated.

[0003] like Figure 2 As shown, in a burst communication receiver, DAGC2 is usually implemented using an open-loop feedforward structure. In DAGC2, the method for calculating the gain estimate is to divide the expected amplitude by the estimated amplitude. Therefore, signal amplitude estimation is a crucial step in the gain control process. This application will focus on the signal amplitude estimation method in DAGC2.

[0004] In the DVB-RCS2 standard, waveforms 8 to 10, waveforms 18 to 20, and waveforms 45 to 47 are all 8PSK burst modulation waveforms containing a preamble symbol, a scattered pilot symbol, and a postamble symbol. Figure 3 This is a schematic diagram of the frame format of this type of waveform. When studying their amplitude estimation methods, it was found that although the data-aided maximum likelihood estimation (DA-MLE) method can achieve good estimation results, since each estimation requires waiting for a burst frame period to extract all pilot symbols, the application of this method has to pay the price of a large estimation delay. Summary of the invention

[0005] Mainly aiming at the deficiencies and defects of the above-mentioned related prior arts, the present invention provides a method for blind amplitude estimation of an 8PSK burst signal, which does not require any pilot assistance and can balance the estimation performance and estimation delay by adjusting the number of 8PSK symbols involved in amplitude estimation.

[0006] In order to achieve the above object, the present invention adopts the following technologies:

[0007] A blind amplitude estimation method for 8PSK burst signal represents the 8PSK symbol sequence used for amplitude estimation, where y[k] = y I [k]+jy Q[k] is an 8PSK symbol that has undergone timing synchronization, frequency synchronization, and phase synchronization. I [k] and y Q [k] are the real and imaginary parts of the symbol y[k], L represents the number of symbols, and the Q-β transform of the symbol y[k] is defined as y′[k] = (y[k]) Q ·e jβ , where Q is a positive integer, β is the argument, and the absolute transformation of the symbol y′[k] is defined as y″[k]=|y′ I [k]|+j|y′ Q [k]|, where y′ I [k] and y′ Q [k] are the real part and the imaginary part of the symbol y′[k], respectively, |·| represents the absolute value of a real number, and the amplitude blind estimation method comprises the following steps:

[0008] S100, determining the number of 8PSK symbols used for amplitude estimation, that is, determining the value of L;

[0009] S200, the 8PSK symbol sequence that has completed timing synchronization, frequency synchronization and phase synchronization The amplitude estimator is serially inputted sequentially, and the intermediate parameter p1[L] is iteratively calculated simultaneously, including:

[0010] S210, set an iteration counter k, whose counting range is k=1, 2, ..., L;

[0011] S220, initializing parameters, setting the initial value of the iteration counter k to 1, and setting the initial value of the intermediate parameter p1 to 0, that is, setting k = 1, p1[0] = 0;

[0012] S230, inputting the kth 8PSK symbol y[k] that has completed timing synchronization, frequency synchronization, and phase synchronization into an amplitude estimator, and calculating an intermediate parameter p1[k], including:

[0013] S231, perform Q-β transformation on the symbol y[k], and obtain y′[k]=(y[k]) Q ·e jβ ; Wherein, in the Q-β transform, if the constellation definition of the 8PSK modulated signal is: Then Q = 2, If the constellation definition of 8PSK modulated signal is: Then Q = 2, β = 0;

[0014] S232. Perform an absolute transformation on the symbol y′[k] to obtain y″[k]=|y′ I [k]|+j|y′ Q [k]|;

[0015] S233, calculate the intermediate parameter p1[k], and obtain p1[k]=p1[k-1]+y″[k];

[0016] S240, judging whether L iteration calculations are completed:

[0017] If completed, the calculation result of the intermediate parameter p1[L] is output;

[0018] If not, update the counter: k←k+1, and repeat steps S230 and S240 until L iterative calculations are completed;

[0019] S300, calculate the intermediate parameter p2:

[0020] S400, calculating the intermediate parameter p3: p3 = |p2|;

[0021] S500, calculate amplitude estimation value

[0022] The beneficial effects of the present invention are as follows: the method of the present application uses only 8PSK symbols for amplitude estimation without any pilot assistance. The estimation performance and estimation delay can be weighed by adjusting the number of 8PSK symbols involved in amplitude estimation; compared with the DA-MLE method, under the condition of equal estimation performance, the method has a smaller estimation delay; under the condition of equal estimation delay, the method has better estimation performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present invention.

[0024] Figure 1 This is the typical distribution mode of DAGC in burst communication receiver.

[0025] Figure 2 It is a typical open-loop feedforward structure of the burst communication receiver DAGC2.

[0026] Figure 3 The figure is a schematic diagram of a frame format of a burst signal containing a leading symbol, a scattered pilot symbol and a trailing pilot symbol.

[0027] Figure 4 It is a constellation diagram of an 8PSK modulated signal.

[0028] Figure 5 It is another constellation diagram of 8PSK modulation signal.

[0029] Figure 6It is a comparison of the estimation performance between the method described in the present invention and the DA-MLE method.

[0030] Figure 7 is an estimated performance evaluation of the method described in the present invention. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and specific implementation method of this application clearer, this application is further described in detail below.

[0032] An embodiment of the present application provides a method for blindly estimating the amplitude of an 8PSK burst signal.

[0033] by represents the 8PSK symbol sequence used for amplitude estimation, where y[k] = y I [k]+jy Q [k] is an 8PSK symbol that has undergone timing synchronization, frequency synchronization, and phase synchronization. I [k] and y Q [k] are the real and imaginary parts of the symbol y[k], L represents the number of symbols, and the Q-β transform of the symbol y[k] is defined as y′[k] = (y[k]) Q ·e jβ , where Q is a positive integer, β is the argument, and the absolute transformation of the symbol y′[k] is defined as y″[k]=|y′ I [k]|+j|y′ Q [k]|, where y′ I [k] and y′ Q [k] are the real and imaginary parts of the symbol y′[k], respectively, and |·| means finding the absolute value of a real number.

[0034] The blind amplitude estimation method of this example includes the following steps:

[0035] S100 , determining the number of 8PSK symbols used for amplitude estimation, that is, determining the value of L.

[0036] S200, the 8PSK symbol sequence that has completed timing synchronization, frequency synchronization and phase synchronization The amplitude estimator is serially inputted sequentially, and the intermediate parameter p1[L] is iteratively calculated simultaneously, including:

[0037] S210, set an iteration counter k, whose counting range is k=1, 2, ..., L;

[0038] S220, initializing parameters, setting the initial value of the iteration counter k to 1, and setting the initial value of the intermediate parameter p1 to 0, that is, setting k = 1, p1[0] = 0;

[0039] S230, input the kth 8PSK symbol y[k] that has completed timing synchronization, frequency synchronization, and phase synchronization into an amplitude estimator to calculate an intermediate parameter p1[k]. Specifically, calculating the intermediate parameter p1[k] includes:

[0040] S231, perform Q-β transformation on the symbol y[k], and obtain y′[k]=(y[k]) Q ·e jβ ; In the Q-β transformation, the values ​​of the parameters Q and β are closely related to the constellation definition of the 8PSK modulation signal. If the constellation definition of the 8PSK modulation signal is: (See Figure 4 ), then Q=2, If the constellation definition of 8PSK modulated signal is: (See Figure 5 ), then Q=2, β=0;

[0041] S232. Perform an absolute transformation on the symbol y′[k] to obtain y″[k]=|y′ I [k]|+j|y′ Q [k]|;

[0042] S233, calculate the intermediate parameter p1[k], and obtain p1[k]=p1[k-1]+y″[k];

[0043] S240, judging whether L iteration calculations are completed:

[0044] If completed, the calculation result of the intermediate parameter p1[L] is output;

[0045] If not, update the counter: k←k+1, and repeat steps S230 and S240 until L iterative calculations are completed.

[0046] S300, calculate the intermediate parameter p2:

[0047] S400, calculating an intermediate parameter p3: p3 = |p2|.

[0048] S500, calculate amplitude estimation value

[0049] Figure 6 The comparison results of the estimation performance between the method described in this example and the DA-MLE method are as follows: first, the two estimation methods are applied to the amplitude estimation of the DVB-RCS2 standard No. 8 waveform, and then the two estimation methods are applied to the amplitude estimation of the DVB-RCS2 standard No. 8 waveform under the same symbol signal-to-noise ratio (E sN0) condition to compare which method has the smaller normalized mean square error of the estimation result. The waveform is an 8PSK burst modulation waveform. The entire burst frame contains 536 symbols, of which the leading, scattered pilot and trailing symbols total 76 symbols. The DA-MLE method uses 76 pilot symbols for amplitude estimation. The method described in this example uses three data symbol sequences of length 128, 256 and 536 for amplitude estimation. Figure 6 It can be seen that when E s When N0>8.6dB (demodulation threshold of waveform No. 8), the method described in this example can achieve better estimation effect than the DA-MLE method by using only 128 data symbols for amplitude estimation. At the same time, the method described in this example only takes about 1 / 4 of the frame period to extract the data symbols required for amplitude estimation, so the estimation delay is significantly smaller than the DA-MLE method.

[0050] Figure 7 is the estimation performance evaluation result of the method described in this example. The evaluation method is: compare the normalized mean square error of the estimation result of the method described in this example with the Cramer-Rao lower bound (CRLB) of the amplitude estimation error. Figure 7 It can be seen that when E s When N0>10dB, the normalized mean square error of the estimation result of the method described in this example is in the same order of magnitude as the Cramer-Rao lower bound (CRLB) of the amplitude estimation error, and the difference between the two decreases continuously as the symbol signal-to-noise ratio increases. s When N0>12dB, the normalized mean square error of the estimation result of the method described in this example approaches the Cramer-Rao lower bound.

[0051] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for blind amplitude estimation of an 8PSK burst signal, characterized in that: by represents the 8PSK symbol sequence used for amplitude estimation, where y[k] = y I [k]+jy Q [k] is an 8PSK symbol that has undergone timing synchronization, frequency synchronization, and phase synchronization. I [k] and y Q [k] are the real and imaginary parts of the symbol y[k], L represents the number of symbols, and the Q-β transform of the symbol y[k] is defined as y′[k] = (y[k]) Q ·e jβ , where Q is a positive integer, β is the argument, and the absolute transformation of the symbol y′[k] is defined as y″[k]=|y′ I [k]|+j|y′ Q [k]|, where y′ I [k] and y′ Q [k] are the real and imaginary parts of the symbol y′[k], respectively, and |·| means finding the absolute value of a real number; The method comprises the steps of: S100, determining the number of 8PSK symbols used for amplitude estimation, that is, determining the value of L; S200, the 8PSK symbol sequence that has completed timing synchronization, frequency synchronization and phase synchronization The amplitude estimator is serially inputted sequentially, and the intermediate parameter p1[L] is iteratively calculated simultaneously, including: S210, set an iteration counter k, whose counting range is k=1, 2, ..., L; S220, initializing parameters, setting the initial value of the iteration counter k to 1, and setting the initial value of the intermediate parameter p1 to 0, that is, setting k = 1, p1[0] = 0; S230, inputting the kth 8PSK symbol y[k] that has completed timing synchronization, frequency synchronization and phase synchronization into an amplitude estimator to calculate an intermediate parameter p1[k]; S240, judging whether L iteration calculations are completed: If completed, the calculation result of the intermediate parameter p1[L] is output; If not, update the counter: k←k+1, and repeat steps S230 and S240 until L iterative calculations are completed; S300, calculate the intermediate parameter p2: S400, calculating the intermediate parameter p3: p3 = |p2|; S500, calculate amplitude estimation value The calculation of the intermediate parameter p1[k] in S230 includes: S231, perform Q-β transformation on the symbol y[k], and obtain y′[k]=(y[k]) Q ·e jβ ; Wherein, in the Q-β transform, if the constellation definition of the 8PSK modulated signal is: m=0,1,2,…,7, then Q=2, If the constellation definition of 8PSK modulated signal is: m=0,1,2,…,7, then Q=2, β=0; S232. Perform an absolute transformation on the symbol y′[k] to obtain y″[k]=|y′ I [k]|+j|y′ Q [k]|; S233. Calculate the intermediate parameter p1[k], and obtain p1[k]=p1[k-1]+y″[k].

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