Frequency deviation estimating method and device

A technology for frequency offset estimation and calculation of symbols, which is applied in the field of frequency offset estimation and can solve the problems of loss of signal accuracy, affecting the accuracy of frequency offset estimation value, and increasing complexity.

Active Publication Date: 2013-12-04
SPREADTRUM COMM (SHANGHAI) CO LTD
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Problems solved by technology

[0003] At present, frequency offset estimation methods suitable for QAM signals include, Chinese patent application number is 200810057421.2, the publication date is July 16, 2008, and the patent name is "A Method and Device for Frequency Offset Estimation", which discloses a QAM Signal frequency offset estimation method, which screens out multiple signal points with power greater than the set threshold from the received signal according to the power of the received quadrature amplitude modulation signal, and then makes a hard decision, by filtering out the signal and its corresponding hard decision The phase and position information of the conjugate multiplication is used to solve the frequency offset value of the received QAM signal. This scheme uses the result of the conjugate multiplication of the traditional received symbol and the corresponding hard decision and the position information of the received symbol through the arctangent operation, using the conjugate The phase of the multiplication result is a function of the frequency offset and the time difference between the two for frequency offset estimation. In order to ensure the estimation accuracy, a multi-level frequency offset estimation plus pre-correction method is further adopted. There are a large number of complex multiplications and sine and cosine operations, resulting in complexity. Increase, engineering realization is more difficult
[0004] The Chinese patent application number is 201010240971.5, and the application date is July 29, 2010. The patent name is "A High-Order Quadrature Amplitude Modulation Signal Frequency Offset Estimation Method and Device", which discloses a high-order QAM signal frequency offset estimation method and device. , the method maps the high-order QAM signal to the low-order QAM signal, or maps the low-order QAM signal to the QPSK signal, and then uses the mature low-order signal frequency offset estimation method to estimate the frequency offset of the received high-order QAM signal. The mapping process of mapping high-order QAM to low-order QAM or mapping low-order QAM to QPSK will lose signal accuracy, which will affect the accuracy of frequency offset estimation

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  • Frequency deviation estimating method and device

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Experimental program
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Effect test

Embodiment 1

[0038] The estimated value of the frequency offset calculated by using the proportional relationship between the imaginary part and the real part of the symbol sequence is to perform frequency compensation on the symbol sequence, and calculate the sum of the squares of the difference between the ratio of the imaginary part and the real part of the symbol sequence after compensation and the standard constellation amplitude threshold, to The frequency compensation value corresponding to the least square sum is an estimated value of frequency offset.

[0039] In particular, taking the time division synchronous code division multiple access TD-SCDMA system QPSK modulation mode as an example for illustration, the preferred implementation process is as follows:

[0040] 101. Rotate the received symbol clockwise by 45°, and mark the rotated symbol sequence as b i , Among them, the received symbol sequence is a i , i=1,..., N, N is the number of received symbols in one code channel, ...

Embodiment 2

[0057] The calculation of the estimated frequency offset by using the proportional relationship between the imaginary part and the real part of the symbol sequence is to calculate the imaginary part of the symbol sequence

[0058] Part to real part ratio, calculate the actual phase of the symbol sequence by arctangent, obtain and use the code channel position, standard phase information and actual phase of the symbol sequence to calculate the estimated frequency offset In particular, take the WCDMA system 16QAM signal as an example to describe in detail, the 16QAM transmission constellation diagram is as follows figure 2 As shown, the preferred implementation process is as follows:

[0059] 201. Symbol screening

[0060] Preferably, constellation points with the same amplitude or phase information are screened out from the received symbol sequence.

[0061] Preferably, the signal points whose ratio of the absolute value of the imaginary part of the symbol to the absolute v...

Embodiment 3

[0077] The estimated frequency offset is calculated by using the proportional relationship between the imaginary part and the real part of the symbol sequence, and the estimated frequency offset is calculated by using the proportional relationship between the imaginary part and the real part of the symbol sequence. The actual phase of the sequence, frequency compensation is performed on the symbol phase, the sum of the absolute value of the difference between the compensated phase and the standard phase is calculated, and the frequency compensation value of the minimum sum of the absolute value of the difference is used as the frequency offset estimation value.

[0078] In particular, the embodiment is described by taking the TD-SCDMA system QPSK modulation mode as an example, and the preferred implementation process is as follows:

[0079] 301. Same as step 101 in Embodiment 1;

[0080] 302. Same as Step 202 of Embodiment 2;

[0081] 303. Same as Step 203 of Embodiment 2;

...

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Abstract

The invention relates to the technical field of communication, in particular to a frequency deviation estimating method and device used in a quadrature amplitude modulation (QAM) mode. The method comprises the following steps of: calculating a frequency deviation estimated value according to the proportional relation between a virtual part and a real part of a symbol sequence; in particular, screening signal points at specific positions on a transmitting star map from a received signal sequence; and screening the phase information and position information of a plurality of screened signal points to realize frequency deviation estimation of a received QAM signal. By adopting the method and the device, the complexity of the QAM signal frequency deviation estimation in the prior art is lowered remarkably while the estimation accuracy is ensured.

Description

technical field [0001] The invention relates to the technical field of communication, in particular to a frequency offset estimation method and device in a quadrature amplitude modulation (QAM, Quadrature Amplitude Modulation) mode. Background technique [0002] In order to further increase the transmission rate of the wireless communication system, high-order modulation is widely used in the communication system. For example, the HSPA service in the third-generation mobile communication system introduces the 16QAM modulation method, and the HSPA+ service introduces the 64QAM modulation method, and cuts down the accompanying DPCH channel of the low-order modulation method. In the e-CELL-FACH / CELL-DCH state, channels such as HS-SCCH / E-AGCH / HS-DSCH all have different degrees of discontinuous characteristics. While the auxiliary carrier Ts0 can carry services, the solution of supplementing broadcast information also has risks. In extreme cases, low-order modulation channels m...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H04L25/02H04L27/34
Inventor 李春霖谭舒
Owner SPREADTRUM COMM (SHANGHAI) CO LTD
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