CN110445738B - Phase estimation method and device based on scattered pilot frequency assistance - Google Patents
Phase estimation method and device based on scattered pilot frequency assistance Download PDFInfo
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- CN110445738B CN110445738B CN201910629551.7A CN201910629551A CN110445738B CN 110445738 B CN110445738 B CN 110445738B CN 201910629551 A CN201910629551 A CN 201910629551A CN 110445738 B CN110445738 B CN 110445738B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2602—Signal structure
- H04L27/261—Details of reference signals
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2657—Carrier synchronisation
Abstract
A phase estimation method based on scattered pilot assistance comprises the following steps: extracting a scattered pilot from a received signal; grouping the scattered pilot frequency, and selecting a group number with a preset number; calculating the symbol length of each group of the scattered pilot frequency according to the group number, the total number of the scattered pilot frequencies and the coincidence interval between the adjacent scattered pilot frequencies; calculating the middle position of each group of the scattered pilot frequency; calculating the phase of each group of the scattered pilot frequency; and carrying out phase interpolation between two adjacent sections of the aggregation pilot frequency to estimate the phase of each symbol. A scattered pilot assistance-based phase estimation apparatus, comprising: the device comprises an extraction module, a grouping module, a calculation module and an interpolation module. The characteristics of the scattered pilot frequency are fully utilized, the equivalent aggregation pilot frequency is established for phase interpolation, the influence caused by residual frequency offset is effectively solved, the calculation complexity is low, and the frame format demodulation requirement of DVB-RCS2 is met.
Description
Technical Field
The present invention relates to carrier synchronization technologies, and in particular, to a phase estimation method and apparatus based on scattered pilot assistance.
Background
In digital communication systems, the demodulation scheme determines the performance of the digital modulation system. The frequency synchronization in the carrier synchronization is an indispensable part in the digital communication system, and compensates for the frequency offset damage caused by the signal in the transmission process.
After the frequency synchronization of the signal, a certain residual frequency offset still remains to affect the phase synchronization. For the burst communication of the DVB-RCS2, especially for the high-order modulation mode, due to the limitation of frequency synchronization precision, the symbol is easy to cross the decision domain by the residual frequency offset, which causes misjudgment.
Disclosure of Invention
In order to solve the phase synchronization problem existing in the related prior art, the invention provides a phase estimation method and a phase estimation device based on scattered pilot frequency assistance, which fully utilize the characteristics of the scattered pilot frequency, establish equivalent aggregated pilot frequency for phase interpolation, effectively solve the influence caused by residual frequency offset, have low calculation complexity and meet the frame format demodulation requirement of DVB-RCS 2.
In order to achieve the above object, the present invention employs the following techniques:
the design concept of the method/device is as follows:
the scattered pilot frequencies are extracted from the synchronous signal one by one to form a series of pilot sampling signals without changing the characteristics of the original signals. The series of pilot sampled signals are grouped by finding the appropriate number of groups, each group being equivalent to a segment of the aggregate pilot. Then, phase interpolation is carried out between two adjacent sections of the aggregated pilots, and the phase of each symbol is estimated.
A phase estimation method based on scattered pilot assistance, comprising the steps of:
extracting a scattered pilot from a received signal;
grouping the scattered pilot frequency, and selecting a group number with a preset number;
calculating the symbol length of each group of the scattered pilot frequency according to the group number, the total number of the scattered pilot frequencies and the symbol interval between the adjacent scattered pilot frequencies;
calculating the middle position of each group of the scattered pilot frequency;
calculating the phase of each group of the scattered pilot frequency;
and carrying out phase interpolation between two adjacent sections of the aggregation pilot frequency to estimate the phase of each symbol.
The preamble length of the received signal is LpreSymbol interval between adjacent scattered pilots is ddpThe total number of the extracted scattered pilot frequency is n, and the scattered pilot frequency symbol is zdp(t), the channel condition is AWGN.
Calculating the symbol length of each group of the scattered pilot frequency, and adopting a formula: n is a radical ofeq＝ddp·deq；
Wherein the content of the first and second substances,
to round down,. leqIs the number of the groups.
Calculating the middle position of each group of the scattered pilot frequency, and adopting a formula:
is the middle position of the k-th group of pilots, the scattered pilot p of the positionmid(k) The position in the whole frame is
locs(k)＝Lpre+locd(k)·ddp,k＝1,2,...,leq。
Calculating the phase of each group of the scattered pilot frequency, and adopting a formula:
wherein, i is 1, 2., n,
c* dp(i) for a local scattered pilot cdp(i) Conjugation of (1).
Performing phase interpolation between two adjacent sections of the aggregation pilot frequency to estimate the phase of each symbol, and specifically, the method is implemented by the following steps:
the phase of the k-th group of pilots is equal to the scattered pilot p of the middle position of the group of pilotsmid(k) Has a phase of
Wherein lsIs pmid(k) And pmidThe index of the symbol between (k +1),
is pmid(k) The phase value of (a).
A phase estimation apparatus based on scattered pilot assistance, comprising:
the extraction module is used for extracting the scattered pilot frequency from the received signal;
the grouping module is used for grouping the scattered pilot frequency and selecting a group number with a preset number;
a calculating module, configured to calculate a symbol length of each group of the scattered pilots according to the number of groups, the total number of the scattered pilots, and a symbol interval between adjacent scattered pilots; then calculating the middle position of each group of the scattered pilot frequency; then calculating the phase of each group of the scattered pilot;
and the interpolation module is used for carrying out phase interpolation between two adjacent sections of the aggregation pilot frequency and estimating the phase of each symbol.
The invention has the beneficial effects that:
the characteristics of the scattered pilot frequency are fully utilized, the equivalent aggregation pilot frequency is established for phase interpolation, the influence caused by residual frequency offset is effectively solved, the calculation complexity is low, and the frame format demodulation requirement of DVB-RCS2 is met.
Drawings
Fig. 1 is a diagram of a DVB-RCS2 scattered pilot frame format.
Fig. 2 is a structural diagram of an equivalent aggregated pilot.
FIG. 3 is a flow chart of an embodiment of the method of the present invention.
FIG. 4 is a block diagram of an embodiment of the apparatus of the present invention.
Fig. 5(a) -5 (d) are the constellation diagrams after the phase synchronization and the subtraction of the corresponding white noise by the method/apparatus of the present invention.
Detailed Description
The invention extracts the scattered pilot frequency from the synchronous signal one by one to form a series of pilot frequency sampling signals without changing the original signal characteristics. The series of pilot sampled signals are grouped by finding the appropriate number of groups, each group being equivalent to a segment of the aggregate pilot. Then, phase interpolation is carried out between two adjacent sections of the aggregated pilots, and the phase of each symbol is estimated.
As shown in fig. 1, is a DVB-RCS2 scattered pilot frame format diagram.
In the examples:
let the preamble length of the received signal be LpreSymbol interval between adjacent scattered pilots is ddpA total of n scattered pilots with channel conditions AWGN, cdpAnd (t) is a local scattered pilot symbol.
Fig. 3 is a flow chart of an embodiment of the method of the present invention.
First, extracting n-point scattered pilot symbols zdp(t)。
Second, the scattered pilots are grouped. Selecting proper group number leqEach set of scattered pilots may be equivalent to a segment of aggregated pilots, as shown in fig. 2.
And thirdly, calculating the length of each group of pilot frequency.
Wherein the content of the first and second substances,
to round down. The symbol length of the aggregated pilot
Neq＝ddp·deq
And fourthly, respectively calculating the middle position of each group of pilot frequencies.
As shown in FIG. 2, the k-th pilot set has a middle position of
Scattered pilot p of the positionmid(k) The position in the whole frame is
locs(k)＝Lpre+locd(k)·ddp,k＝1,2,...,leq
And fifthly, respectively calculating the phase of each group of pilot frequency.
Wherein
c* dp(i) For a local scattered pilot cdp(i) Conjugation of (1).
And sixthly, performing phase interpolation between two adjacent sections of pilot frequency. The phase of the k-th group of pilots is equal to the scattered pilot p of the middle position of the group of pilotsmid(k) Has a phase of
Wherein lsIs pmid(k) And pmidThe index of the symbol between (k +1),
is pmid(k) The phase value of (a).
Fig. 4 is a block diagram of an embodiment of the apparatus of the present invention.
The device comprises:
the extraction module is used for extracting the scattered pilot frequency from the received signal;
the grouping module is used for grouping the scattered pilot frequency and selecting a group number with a preset number;
a calculating module, configured to calculate a symbol length of each group of the scattered pilots according to the number of groups, the total number of the scattered pilots, and a symbol interval between adjacent scattered pilots; then calculating the middle position of each group of the scattered pilot frequency; then calculating the phase of each group of the scattered pilot;
and the interpolation module is used for carrying out phase interpolation between two adjacent sections of the aggregation pilot frequency and estimating the phase of each symbol.
By performing phase synchronization on the method and/or the apparatus of the above embodiment, a constellation diagram with the corresponding white noise subtracted can be obtained, as shown in fig. 5(a) to 5 (d).
The physical frame format for performance evaluation is the following 4 waveforms defined by the DVB-RCS2 standard:
WaveformID＝43(BPSK@1/2)；
WaveformID＝42(BPSK@1/3)；
WaveformID＝14(QPSK@1/2)；
WaveformID＝18(8PSK@2/3)。
as can be seen from the figure, the constellation tailing is small, the distance from the judgment threshold is far, and the symbol can be correctly judged.
Claims (6)
1. A phase estimation method based on scattered pilot assistance, comprising the steps of:
extracting a scattered pilot from a received signal;
grouping the scattered pilot frequency, and selecting a group number with a preset number;
calculating the symbol length of each group of the scattered pilot frequency according to the group number, the total number of the scattered pilot frequencies and the symbol interval between the adjacent scattered pilot frequencies;
calculating the middle position of each group of the scattered pilot frequency;
calculating the phase of each group of the scattered pilot frequency, and adopting a formula:
wherein, i is 1, 2., n,
c* dp(i) for a local scattered pilot cdp(i) Is conjugated to zdp(i) For scattered pilot symbols, deqFor the length of each set of scattered pilots, n is the total number of scattered pilots, locd(k) The middle position of the k-th group of scattered pilots;
and carrying out phase interpolation between two adjacent groups of the discrete pilots to estimate the phase of each symbol.
2. The phase estimation method based on scattered pilot assistance of claim 1, wherein the preamble length of the received signal is LpreSymbol interval between adjacent scattered pilots is ddpThe channel condition is AWGN.
3. The scattered pilot assistance-based phase estimation method according to claim 2, wherein the symbol length of each group of the scattered pilots is calculated by using the formula: n is a radical ofeq＝ddp·deq；
Wherein the content of the first and second substances,
in order to get the whole downwards,leqis the number of the groups.
4. The scattered pilot assistance-based phase estimation method according to claim 3,
calculating the middle position of each group of the scattered pilot frequency, and adopting a formula:
is the middle position of the k-th group of pilots, the scattered pilot p of the positionmid(k) The position in the whole frame is
locs(k)＝Lpre+locd(k)·ddp,k＝1,2,...,leq。
5. The phase estimation method based on scattered pilot assistance as claimed in claim 4, wherein the phase of each symbol is estimated by performing phase interpolation between two adjacent groups of the scattered pilots, specifically by:
the phase of the k-th group of pilots is equal to the scattered pilot p of the middle position of the group of pilotsmid(k) Has a phase of
Wherein lsIs pmid(k) And pmidThe index of the symbol between (k +1),
is pmid(k) The phase value of (a).
6. A phase estimation apparatus based on scattered pilot assistance, comprising:
the extraction module is used for extracting the scattered pilot frequency from the received signal;
the grouping module is used for grouping the scattered pilot frequency and selecting a group number with a preset number;
a calculating module, configured to calculate a symbol length of each group of the scattered pilots according to the number of groups, the total number of the scattered pilots, and a symbol interval between adjacent scattered pilots; then calculating the middle position of each group of the scattered pilot frequency; then, calculating the phase of each group of the scattered pilots, and adopting a formula:
wherein, i is 1, 2., n,
for a local scattered pilot cdp(i) Is conjugated to zdp(i) For scattered pilot symbols, deqFor the length of each set of scattered pilots, n is the total number of scattered pilots, locd(k) The middle position of the k-th group of scattered pilots;
and the interpolation module is used for carrying out phase interpolation between two adjacent groups of discrete pilots to estimate the phase of each symbol.
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| CN103095615A (en) * | 2011-10-31 | 2013-05-08 | 华为技术有限公司 | Method and device for phase noise estimation and compensation |
| CN103905351A (en) * | 2014-04-23 | 2014-07-02 | 湖南国科微电子有限公司 | Method and system for DVB-T2 channel estimation |
| CN104219191A (en) * | 2014-09-18 | 2014-12-17 | 扬智科技股份有限公司 | Orthogonal carrier frequency division multiplexing signal processing method and specific pilot frequency domain signal estimation method |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103095615A (en) * | 2011-10-31 | 2013-05-08 | 华为技术有限公司 | Method and device for phase noise estimation and compensation |
| CN103905351A (en) * | 2014-04-23 | 2014-07-02 | 湖南国科微电子有限公司 | Method and system for DVB-T2 channel estimation |
| CN104219191A (en) * | 2014-09-18 | 2014-12-17 | 扬智科技股份有限公司 | Orthogonal carrier frequency division multiplexing signal processing method and specific pilot frequency domain signal estimation method |
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