CN115865586B - A Blind Amplitude Estimation Method for 8PSK Burst Signal - Google Patents

Abstract

A blind estimation method for the amplitude of 8PSK burst signal includes such steps as determining the number of 8PSK symbols used for amplitude estimation, that is, the value of L, S100, and the sequence of 8PSK symbols with timing, frequency and phase synchronizationSequentially and serially inputting the amplitude estimators, and simultaneously iteratively calculating an intermediate parameter p ₁ [ L ]; S300, calculating the intermediate parameter p ₂: S400, calculating an intermediate parameter p ₃：p₃＝|p₂, S500, and calculating an amplitude estimation value Only 8PSK modulation symbols are used for amplitude estimation without any pilot assistance. The method has the advantages that the estimation performance and the estimation time delay can be weighed by adjusting the number of 8PSK symbols participating in amplitude estimation, compared with a DA-MLE method, the method has smaller estimation time delay under the condition of equal estimation performance, and has better estimation performance under the condition of equal estimation time delay.

Description

8PSK burst signal amplitude blind estimation method

Technical Field

The invention relates to the technical field of digital communication, in particular to a parameter estimation technology of burst signals, and particularly relates to an amplitude blind estimation method of 8PSK burst signals.

Background

In a reverse link burst communication receiver of an MF-TDMA satellite communication system, at least two Digital Automatic Gain Controllers (DAGCs) are required to adjust the amplitude of the signal to meet the requirements of the subsequent signal processing modules. One is DAGC1 located between the matched filter and the timing, frequency and phase synchronization module (hereinafter referred to as synchronization module), and the other is DAGC2 located between the synchronization module and the soft demapping module. Fig. 1 illustrates a typical distribution of digital automatic gain controllers in a burst communication receiver.

As shown in fig. 2, in a burst communication receiver, DAGC2 is typically implemented using an open loop feed forward structure. In DAGC2, the gain estimate is calculated by dividing the desired amplitude by the estimated amplitude. Signal amplitude estimation is therefore a crucial step in the gain control process. The present application will focus on the signal amplitude estimation method in DAGC 2.

In the DVB-RCS2 standard, waveforms No. 8-10, no. 18-20 and No. 45-47 are 8PSK burst modulation waveforms containing preamble symbols, scattered pilot symbols and postamble symbols. Fig. 3 is a frame format schematic of such waveforms. In studying their amplitude estimation methods, it was found that while a data-aided maximum likelihood estimation (DA-MLE) method can achieve good estimation results, applying this method has to pay a large estimation delay since each estimation requires waiting for one burst frame period to extract all pilot symbols.

Disclosure of Invention

The invention provides an amplitude blind estimation method of 8PSK burst signals, which mainly aims at the defects and the shortcomings of the related prior art, does not need any pilot frequency assistance, and can balance estimation performance and estimation time delay by adjusting the number of 8PSK symbols participating in amplitude estimation.

In order to achieve the above object, the present invention adopts the following technique:

an amplitude blind estimation method for 8PSK burst signals Representing a sequence of 8PSK symbols for amplitude estimation, wherein y [ k ] = y _I[k]+jy_Q [ k ] is an 8PSK symbol subjected to timing synchronization, frequency synchronization and phase synchronization, y _I [ k ] and y _Q [ k ] are real and imaginary parts of the symbol y [ k ] respectively, L represents the number of symbols, Q- β transform defining the symbol y [ k ] is y ' [ k ] = (y [ k ]) ^Q·e^jβ, wherein Q is a positive integer, β is a argument, absolute transform defining the symbol y ' [ k ] is y ' [ k ] = |y ' _I[k]|+j|y′_Q [ k ] |, wherein y ' _I [ k ] and y ' _Q [ k ] are real and imaginary parts of the symbol y ' [ k ] respectively, and || represents an absolute value of a real number, the amplitude blind estimation method comprising the steps of:

S100, determining the number of 8PSK symbols for amplitude estimation, namely determining the value of L;

S200, 8PSK symbol sequence with timing synchronization, frequency synchronization and phase synchronization Sequentially and serially inputting the amplitude estimators, and simultaneously iteratively calculating intermediate parameters p ₁ [ L ], wherein the method comprises the following steps:

s210, setting an iteration counter k, where the counting range is k=1, 2,;

s220, initializing parameters, setting the initial value of the iteration counter k to 1, and setting the initial value of the intermediate parameter p ₁ to 0, i.e., setting k=1, p ₁ [0] =0;

S230, inputting the kth 8PSK symbol y [ k ] with the completed timing synchronization, frequency synchronization and phase synchronization into an amplitude estimator, and calculating an intermediate parameter p ₁ [ k ], comprising:

S231, Q-beta conversion is carried out on the symbol y [ k ] to obtain y' [ k ] = (y [ k ]) ^Q·e^jβ, wherein in the Q-beta conversion, if constellation definition of 8PSK modulation signals is: then there is Q=2, If the constellation definition of an 8PSK modulated signal is: then q=2, β=0;

S232, carrying out absolute transformation on the symbol y '[ k ] to obtain y' '[ k ] = |y' _I[k]|+j|y′_Q [ k ] |;

s233, calculating an intermediate parameter p ₁ [ k ] to obtain p ₁[k]＝p₁ [ k-1] +y ] [ k ];

s240, judging whether L times of iterative computation are completed or not:

if so, outputting a calculation result p ₁ [ L ] of the intermediate parameter;

if not, the counter is updated: k≡k+1, repeating step S230 and step S240 until L iterative computations are completed;

S300, calculating an intermediate parameter p ₂:

S400, calculating an intermediate parameter p ₃：p₃＝|p₂;

S500, calculating an amplitude estimation value

The method has the beneficial effects that the method only adopts 8PSK symbols to carry out amplitude estimation, and no pilot frequency assistance is needed. The method has the advantages that the estimation performance and the estimation time delay can be weighed by adjusting the number of 8PSK symbols participating in amplitude estimation, compared with a DA-MLE method, the method has smaller estimation time delay under the condition of equal estimation performance, and has better estimation performance under the condition of equal estimation time delay.

Drawings

The drawings described herein are for illustration of selected embodiments only and not all possible implementations, and are not intended to limit the scope of the invention.

Fig. 1 is a typical distribution of DAGC in a burst communication receiver.

Fig. 2 is a typical open loop feed forward structure of a burst communication receiver DAGC 2.

Fig. 3 is a schematic diagram of a frame format of a burst signal including preamble symbols, scattered pilot symbols, and postamble symbols.

Fig. 4 is a constellation diagram of an 8PSK modulated signal.

Fig. 5 is a constellation diagram of another 8PSK modulated signal.

FIG. 6 is a comparison of estimated performance of the method of the present invention with the DA-MLE method.

Fig. 7 is an estimated performance evaluation of the method of the present invention.

Detailed Description

In order to make the objects, technical solutions and specific implementation methods of the present application more clear, the present application will be described in further detail below.

The embodiment of the application provides an amplitude blind estimation method of 8PSK burst signals.

To be used forRepresenting a sequence of 8PSK symbols for amplitude estimation, wherein y [ k ] = y _I[k]+jy_Q [ k ] is an 8PSK symbol subjected to timing synchronization, frequency synchronization and phase synchronization, y _I [ k ] and y _Q [ k ] are the real part and the imaginary part of the symbol y [ k ] respectively, L represents the number of symbols, Q- β transform defining the symbol y [ k ] is y ' [ k ] = (y [ k ]) ^Q·e^jβ, wherein Q is a positive integer, β is a argument, absolute transform defining the symbol y ' [ k ] is y ' [ k ] = |y ' _I[k]|+j|y′_Q [ k ] |, wherein y ' _I [ k ] and y ' _Q [ k ] are the real part and the imaginary part of the symbol y ' [ k ] respectively, and || represents the absolute value of the real number.

The amplitude blind estimation method of the present example includes the steps of:

s100, determining the number of 8PSK symbols for amplitude estimation, namely determining the value of L.

S200, 8PSK symbol sequence with timing synchronization, frequency synchronization and phase synchronizationSequentially and serially inputting the amplitude estimators, and simultaneously iteratively calculating intermediate parameters p ₁ [ L ], wherein the method comprises the following steps:

s210, setting an iteration counter k, where the counting range is k=1, 2,;

s220, initializing parameters, setting the initial value of the iteration counter k to 1, and setting the initial value of the intermediate parameter p ₁ to 0, i.e., setting k=1, p ₁ [0] =0;

S230, inputting the kth 8PSK symbol y [ k ] with the completed timing synchronization, frequency synchronization and phase synchronization into an amplitude estimator, and calculating an intermediate parameter p ₁ [ k ]. Specifically, calculating the intermediate parameter p ₁ [ k ] includes:

S231, Q-beta conversion is carried out on the symbol y [ k ] to obtain y' [ k ] = (y [ k ]) ^Q·e^jβ, wherein in Q-beta conversion, the values of parameters Q and beta are closely related to constellation definition of 8PSK modulation signals. If the constellation definition of an 8PSK modulated signal is: (see fig. 4), then there is q=2, If the constellation definition of an 8PSK modulated signal is: (see fig. 5), then q=2, β=0;

S232, carrying out absolute transformation on the symbol y '[ k ] to obtain y' '[ k ] = |y' _I[k]|+j|y′_Q [ k ] |;

s233, calculating an intermediate parameter p ₁ [ k ] to obtain p ₁[k]＝p₁ [ k-1] +y ] [ k ];

s240, judging whether L times of iterative computation are completed or not:

if so, outputting a calculation result p ₁ [ L ] of the intermediate parameter;

If not, the counter is updated: k≡k+1, and repeating steps S230 and S240 until L iterative computations are completed.

S300, calculating an intermediate parameter p ₂:

S400, calculating an intermediate parameter p ₃：p₃＝|p₂.

S500, calculating an amplitude estimation value

FIG. 6 is a comparison of estimated performance of the method described in this example with the DA-MLE method. The comparison method is that firstly, the two estimation methods are respectively applied to the amplitude estimation of the DVB-RCS2 standard No. 8 waveform, and then the normalized mean square error of the estimation result of which method is smaller is compared under the same symbol signal to noise ratio (E _sN₀). The waveform is an 8PSK burst modulated waveform, with the entire burst frame containing 536 symbols, with the preamble, scattered pilots, and postamble totaling 76 symbols. The DA-MLE method uses 76 pilot symbols for amplitude estimation. The method described in this example uses three lengths of data symbol sequences 128, 256, 536 for amplitude estimation, respectively. As can be seen from fig. 6, when E _sN₀ >8.6dB (demodulation threshold of waveform No. 8), the method described in this example can obtain 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 requires about 1/4 of the frame period to extract the data symbols required for amplitude estimation, so the estimated delay is significantly smaller than the DA-MLE method.

Fig. 7 is an estimated performance evaluation result of the method described in this example. The evaluation method is to compare the normalized mean square error of the estimation result of the method described in this example with the lower boundary (CRLB) of the Kramer for the amplitude estimation error. As can be seen from fig. 7, when E _sN₀ >10dB, the normalized mean square error of the estimation result of the method described in this example is on the same order of magnitude as the lower cladmerol bound (CRLB) of the amplitude estimation error, and the difference between the two continuously decreases as the symbol signal-to-noise ratio increases. When E _sN₀ >12dB, the normalized mean square error of the estimation results of the method described in this example approximates the lower boundary of the Clamamaro.

The above is only a preferred embodiment of the present invention and is not intended to limit the present invention, and it is obvious that those skilled in the art can make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.

Claims (1)

1. A8 PSK burst signal amplitude blind estimation method is characterized in that:

To be used for Representing a sequence of 8PSK symbols for amplitude estimation, wherein y [ k ] = y _I[k]+jy_Q [ k ] is an 8PSK symbol subjected to timing synchronization, frequency synchronization, and phase synchronization, y _I [ k ] and y _Q [ k ] are real and imaginary parts of the symbol y [ k ] respectively, L represents the number of symbols, Q- β transform defining the symbol y [ k ] is y ' [ k ] = (y [ k ]) ^Q·e^jβ, wherein Q is a positive integer, β is a argument, absolute transform defining the symbol y ' [ k ] is y ' [ k ] = |y ' _I[k]|+j|y′_Q [ k ] |, wherein y ' _I [ k ] and y ' _Q [ k ] are real and imaginary parts of the symbol y ' [ k ] respectively, and || represents an absolute value for real numbers;

The method comprises the steps of:

S100, determining the number of 8PSK symbols for amplitude estimation, namely determining the value of L;

S200, 8PSK symbol sequence with timing synchronization, frequency synchronization and phase synchronization Sequentially and serially inputting the amplitude estimators, and simultaneously iteratively calculating intermediate parameters p ₁ [ L ], wherein the method comprises the following steps:

s210, setting an iteration counter k, where the counting range is k=1, 2,;

s220, initializing parameters, setting the initial value of the iteration counter k to 1, and setting the initial value of the intermediate parameter p ₁ to 0, i.e., setting k=1, p ₁ [0] =0;

S230, inputting the kth 8PSK symbol y [ k ] with the timing synchronization, the frequency synchronization and the phase synchronization completed into an amplitude estimator, and calculating an intermediate parameter p ₁ [ k ];

s240, judging whether L times of iterative computation are completed or not:

if so, outputting a calculation result p ₁ [ L ] of the intermediate parameter;

if not, the counter is updated: k≡k+1, repeating step S230 and step S240 until L iterative computations are completed;

S300, calculating an intermediate parameter p ₂:

S400, calculating an intermediate parameter p ₃：p₃＝|p₂;

S500, calculating an amplitude estimation value

Wherein, calculating the intermediate parameter p ₁ [ k ] in S230 includes:

S231, Q-beta conversion is carried out on the symbol y [ k ] to obtain y' [ k ] = (y [ k ]) ^Q·e^jβ, wherein in the Q-beta conversion, if constellation definition of 8PSK modulation signals is: m=0, 1,2,..7, then q=2 If the constellation definition of an 8PSK modulated signal is: m=0, 1,2,..7, then q=2, β=0;

S232, carrying out absolute transformation on the symbol y '[ k ] to obtain y' '[ k ] = |y' _I[k]|+j|y′_Q [ k ] |;

s233, calculating an intermediate parameter p ₁ [ k ] to obtain p ₁[k]＝p₁ [ k-1] +y ] [ k ].