CN108923877A - A kind of PCMA timing acquisition and tracking - Google Patents
A kind of PCMA timing acquisition and tracking Download PDFInfo
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- CN108923877A CN108923877A CN201810720521.2A CN201810720521A CN108923877A CN 108923877 A CN108923877 A CN 108923877A CN 201810720521 A CN201810720521 A CN 201810720521A CN 108923877 A CN108923877 A CN 108923877A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J3/00—Time-division multiplex systems
- H04J3/02—Details
- H04J3/06—Synchronising arrangements
- H04J3/0635—Clock or time synchronisation in a network
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/14—Relay systems
- H04B7/15—Active relay systems
- H04B7/185—Space-based or airborne stations; Stations for satellite systems
- H04B7/18578—Satellite systems for providing broadband data service to individual earth stations
- H04B7/18582—Arrangements for data linking, i.e. for data framing, for error recovery, for multiple access
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Abstract
The present invention relates to a kind of PCMA timing acquisition and trackings, include the following steps：S1. timing acquisition interference signal；S2. the modulation and encoded information for receiving next frame, obtain the frame length information of present frame, predict the appearance position of next frame head, realize dynamically track.Timing acquisition proposed in this paper and its performance of track algorithm are still fine under dynamic frequency offset, meet the application demand of certain high dynamic scenes, simultaneously under conditions of lower signal-to-noise ratio, the root-mean-square error of timing is better than traditional algorithm, the accuracy with preferable tolerance and synchronization.
Description
Technical field
The present invention relates to digital communicating fields, more particularly to a kind of PCMA timing acquisition and tracking.
Background technique
Paired carrier multiple access technology (PCMA, Paired Carrier Multiple Access) by making two, ground
The satellite channel of different terminals occupies identical band bandwidth, so that band efficiency theoretically can be improved one times, from
And power system capacity is greatly improved, while also improving the safety of satellite communication.When PCMA system works in asymmetric mode
When, the lesser earth station of transmission power can dispose small-power component as noise signal, so that it may it is larger to obtain power
The signal of one side, can also do identical processing for non-cooperating third party can be obtained information.It is biggish for transmission power
Earth station can send signal " reproduction " local, and offset as self-interference signal, thus the signal of isolated other side.
In the demodulation of PCMA signal, the part of most critical is the estimation to channel parameter.Utilize the local corresponding base band of information sequence
Information, in conjunction with the downward signal of satellite received to the parameter of channel, using advanced timing acquisition and track algorithm, on the one hand
Time delay can accurately be estimated, obtain corresponding estimated value, provide stringent time reference to reproduce local signal, it is another
Accurately Symbol Timing helps to reduce the influence of noise aspect, to improve demodulation performance.
For single-signal processing usually regardless of the time delay of signal in digital communication.But multiple letters in mixed signal
When number time delay is not identical, different time delays corresponds to different Symbol Timings, uses symbolic information to directly influence
The convergence effect and convergence rate of algorithm and subsequent algorithm.It is proposed by the present invention using the incoherent timing acquisition of known symbol and
Tracking solves the problems, such as that traditional closed-loop algorithmic statement is slow, delay is big and timing accuracy is not high, and performance is in high dynamic
Still do well under frequency deviation and Low SNR, suitable for the various application scenarios of environment harshness, creates pole for user
Big economic value.
Summary of the invention
It is an object of the invention to overcome the deficiencies of the prior art and provide a kind of PCMA timing acquisition and tracking, energy
Enough solve the technical problem that traditional closed-loop algorithmic statement is slow, delay is big and timing accuracy is not high.
The purpose of the present invention is achieved through the following technical solutions：
A kind of PCMA timing acquisition and tracking, it is characterised in that：It the described method comprises the following steps：
S1. timing acquisition interference signal, including：
S11. the interference signal data of two frame lengths are obtained；
It is S12. primary every four sampled point sliding windows among the first frame data of the interference signal data of described two frame lengths,
Extract one times of symbol；
S13. known symbol is divided into 16*16 grouping, does noncoherent accumulation, calculate energy and compared with thresholding；
S14. judge whether current sliding window energy is greater than thresholding；If so, S15 is thened follow the steps, if it is not, thening follow the steps
S16；
S15. next window is slid into；Execute step S17；
S16. first frame data are abandoned, step S11 is executed；
S17. judgement works as whether front window energy is greater than two windows of left and right, if it is not, S15 is thened follow the steps, if so, thening follow the steps
S18；
S18. two sampled points are respectively being slided before and after front window, is obtaining a total of five sliding window data, will be accorded in sliding window
Number it is divided into 16*16 grouping, does noncoherent accumulation；Take out the corresponding sliding window of Energy maximum value and freeze frame in five sliding windows
Head；
S2. the modulation and encoded information for receiving next frame, obtain the frame length information of present frame, predict the appearance of next frame head
Dynamically track is realized in position.
Step S2 further comprises：
S21.DSP informs modulation corresponding to FPGA present frame and coding when sending the backup by present frame
Information, FPGA is by parsing the frame length information of the acquisition of information present frame to predict the appearance position of next frame head；
S22. two sampled points are respectively slided before and after the appearance position of the next frame head of prediction, obtains a total of five sliding
Sliding window internal symbol is divided into 16*16 grouping, does noncoherent accumulation by window data；Take out Energy maximum value pair in five sliding windows
The sliding window answered simultaneously locks frame head.
It the corresponding sliding window of Energy maximum value and locks frame head in five sliding windows of the taking-up and further includes：
If the Best Point acquired is the first two sampled point any point, the super previous point of signal is indicated, if that acquires is best
Point is latter two sampled point any point, indicates that signal prolongs the latter point, if the Best Point acquired is just current point, indicates letter
It number does not also delay in advance.
The beneficial effects of the present invention are：By the timing acquisition and track algorithm of above-mentioned PCMA, can be obtained accurately
Frame header position.Traditional frame synchronization usually utilizes the methods of symbol correlation, and performance can be with the increase of normalization dynamic frequency offset
Or signal-to-noise ratio reduction and sharply deteriorate.Under conditions of received signal to noise ratio is certain, timing acquisition proposed in this paper and tracking are calculated
Its performance of method is still fine under dynamic frequency offset, meets the application demand of certain high dynamic scenes, while in lower signal-to-noise ratio
Under conditions of, the root-mean-square error of timing is better than traditional algorithm, the accuracy with preferable tolerance and synchronization.
Detailed description of the invention
Fig. 1 is the PCMA acquisition and tracking flow chart according to one embodiment.
Fig. 2 is the acquisition phase flow chart according to the PCMA of one embodiment.
Fig. 3 is the tracking phase flow chart according to the PCMA of one embodiment.
Fig. 4 is the simulation model figure according to PCMA.
Fig. 5 is to search for schematic diagram according to the PCMA timing acquisition of one embodiment.
Fig. 6 is to capture schematic diagram according to the adaptive threshold of one embodiment.
Specific embodiment
For a clearer understanding of the technical characteristics, objects and effects of the present invention, this hair of Detailed description of the invention is now compareed
Bright specific embodiment.
Fig. 1 shows the step of entire PCMA acquisition and tracking；
The step of Fig. 2 shows the acquisition phases of PCMA；It specifically includes：
S1. timing acquisition interference signal, including：
S11. the interference signal data of two frame lengths are obtained；
It is S12. primary every four sampled point sliding windows among the first frame data of the interference signal data of described two frame lengths,
Extract one times of symbol；
S13. known symbol is divided into 16*16 grouping, does noncoherent accumulation, calculate energy and compared with thresholding；
S14. judge whether current sliding window energy is greater than thresholding；If so, S15 is thened follow the steps, if it is not, thening follow the steps
S16；
S15. next window is slid into；Execute step S17；
S16. first frame data are abandoned, step S11 is executed；
S17. judgement works as whether front window energy is greater than two windows of left and right, if it is not, S15 is thened follow the steps, if so, thening follow the steps
S18；
S18. two sampled points are respectively being slided before and after front window, is obtaining a total of five sliding window data, will be accorded in sliding window
Number it is divided into 16*16 grouping, does noncoherent accumulation；Take out the corresponding sliding window of Energy maximum value and freeze frame in five sliding windows
Head；
Fig. 3 shows the step of tracking phase of PCMA；It specifically includes：
S21.DSP informs modulation corresponding to FPGA present frame and coding when sending the backup by present frame
Information, FPGA is by parsing the frame length information of the acquisition of information present frame to predict the appearance position of next frame head；
S22. two sampled points are respectively slided before and after the appearance position of the next frame head of prediction, obtains a total of five sliding
Sliding window internal symbol is divided into 16*16 grouping, does noncoherent accumulation by window data；Take out Energy maximum value pair in five sliding windows
The sliding window answered simultaneously locks frame head.
Fig. 4 shows the function structure chart of PCMA simulation model.
In real satellite link, signal is to continuously transmit, in order to eliminate the influence of interference signal, it is necessary first to find interference
The initial position of signal frame, the process for searching for frame header position are divided into two steps：Timing acquisition and tracking.
Design uses the incoherent timing capture method of known symbol, and the search process of PCMA capture is as shown in Figure 5；
Entire search process carries out a point window using sliding window and judges, it is assumed that interference signal frame length be N (8 sampling data
Length), receiver receives the data of 2*N long, and the length of window is 256*8, slides in top n symbol, every time half of symbol of sliding
Number (i.e. four sampled points) extract one times of symbol (total 256 symbols) when front window, are divided into 16 groups, every group of 16 symbols, then
Every group of 16 symbols are asked into related (i.e. conjugate multiplication) and cumulative averaging to known symbol respectively, then obtain 16 groups are averaged
Value seeks energy respectively, finally finds out the mean value of 16 energy values.Sliding window finishes in the first frame, find out average energy value maximum value and
The initial position of its corresponding window, window is thick timing position, then slides back and forth 2 sampled points in thick timing position, obtains 5 windows
Data, the cumulative calculating for seeking average energy value of correlation before continuing, find out average energy value maximum value and its corresponding window, then the window
Initial position be frame header position (first sample point of first symbol of physical frame).
By taking kth window as an example, it is assumed thatFor extracted in kth window data symbolic vector (j indicate window starting adopt
Sampling point, j=1,2,3 ..., N), and the QPSK mapping value of known symbol is denoted as know_data, sig_recv is 8 received
Sampling signal, then known symbol to receive signal ask it is related and add up calculating steps are as follows：
Eng (m)=(abs (signal (m)))2 (m=1,2,3 ..., 16)
Wherein, k=(j-1)/4+1；Sig_recv ((i-1) * 8+j) is the one times of symbol extracted every 8 sampling points.It is sliding
N/4 energy value is obtained after windowIt is assumed that the mean power of received 8 sampling signal of a frame is power_
Avg, thresholding bound are power_avg*ratio (ratio=eng_avg/power_avg, ratio are obtained by emulating), ifGreater than bound, then the success of frame head coarse search is determined, corresponding window initial position is jmax.Conversely, abandoning front
A frame length data, continuation search for next time.If searching for successfully, 2 points are respectively slided before and after window initial position, form 5 window numbers
According to finding out 5 energy values by the similar method in frontFind out maximum value thereinThe energy is most
Being worth corresponding sampled point greatly is frame head initial position.
The search process entirely captured can be summarized as 3 steps：
1) every four sampled point sliding windows are primary, extract one times of symbol, do to known symbol related, and are grouped averaging,
Then energy is asked to each group of average value, is finally averaging energy value；
2) value is compared with adaptive threshold, when detecting that energy value is more than thresholding, assert current sliding window packet
Containing frame originating point information, system using in sliding window compared with threshold value by the way of, slided by sampled point, the adaptive threshold of each window
It is as shown in Figure 6 to capture process.H1Indicate that correlated results is greater than the case where receiving power threshold, H0Represent less than the feelings for receiving power
Condition.K is a fixed threshold reference coefficient (value is ratio, 0≤K≤1), is obtained by emulation.When correlated results is greater than thresholding
Afterwards, timing position τ and correlation R (τ) at this time is write down, and continues one sampled point of forward slip, obtains correlation R (τ+1).
If R (τ+1) > R (τ), enables τ=τ+1, continue to slide, until R (τ+1) < R (τ), obtains final result
3) based on the window of maximum value, front and back is respectively pressed sampled point and is slided 2 times, and using 1) similar method, 5 window numbers are always obtained
According to similarly, finding out maximum energy value, find out maximum value and its corresponding window head position, at this point, window head position is interference signal
Frame header position.
Trace flow is as shown in Figure 3：After the completion of frame head capture, each frame does a timing tracking.It is assumed that every frame relative to
Former frame is advanced or delays 2 sampled points, using the maximum value of the identical algorithm of timing acquisition and noncoherent accumulation energy come really
Fixed optimal frame starting point indicates the super previous point of signal, if asking if the Best Point acquired is the first two sampled point any point
The Best Point obtained is latter two sampled point any point, indicates that signal prolongs the latter point, if the Best Point acquired is just current
Point indicates that signal is not also delayed in advance.Using preceding 256 known symbols, equally it is divided into 16 groups here, every group of 16 symbols.
Calculation method is similar with capture, repeats no more.
When practical application, DSP can inform tune corresponding to FPGA present frame when sending the backup by present frame simultaneously
System and encoded information, FPGA can get the frame length information of present frame by parsing the information, thus can predict next superframe
The appearance position of frame head realizes dynamically track.2 sample points are respectively deviated before and after at next superframe frame header position of prediction, and
Corresponding noncoherent accumulation energy is acquired, takes out maximum value, the corresponding sample point of the maximum value is real frame header position.
In the above-described embodiments, it all emphasizes particularly on different fields to the description of each embodiment, is not described in some embodiment
Part, reference can be made to the related descriptions of other embodiments.
Those of ordinary skill in the art will appreciate that realizing all or part of the process in above-described embodiment method, being can be with
Relevant hardware is instructed to complete by computer program, the program can be stored in computer-readable storage medium
In, the program is when being executed, it may include such as the process of the embodiment of above-mentioned each method.Wherein, the storage medium can be magnetic
Dish, CD, ROM, RAM etc..
The above disclosure is only the preferred embodiments of the present invention, cannot limit the right model of the present invention with this certainly
It encloses, therefore equivalent changes made in accordance with the claims of the present invention, is still within the scope of the present invention.
Claims (3)
1. a kind of PCMA timing acquisition and tracking, it is characterised in that：It the described method comprises the following steps：
S1. timing acquisition interference signal, including：
S11. the interference signal data of two frame lengths are obtained；
S12. primary every four sampled point sliding windows among the first frame data of the interference signal data of described two frame lengths, it extracts
One times of symbol out；
S13. known symbol is divided into 16*16 grouping, does noncoherent accumulation, calculate energy and compared with thresholding；
S14. judge whether current sliding window energy is greater than thresholding；If so, S15 is thened follow the steps, if it is not, thening follow the steps S16；
S15. next window is slid into；Execute step S17；
S16. first frame data are abandoned, step S11 is executed；
S17. judgement works as whether front window energy is greater than two windows of left and right, if it is not, S15 is thened follow the steps, if so, thening follow the steps S18；
S18. two sampled points are respectively being slided before and after front window, is obtaining a total of five sliding window data, by sliding window internal symbol point
It is grouped at 16*16, does noncoherent accumulation；It takes out the corresponding sliding window of Energy maximum value in five sliding windows and locks frame head；
S2. the modulation and encoded information for receiving next frame, obtain the frame length information of present frame, predict the appearance position of next frame head
It sets, realizes dynamically track.
2. a kind of PCMA timing acquisition according to claim 1 and tracking, step S2 further comprise：
S21. DSP is when sending the backup by present frame, while informing modulation corresponding to FPGA present frame and coding letter
Breath, FPGA is by parsing the frame length information of the acquisition of information present frame to predict the appearance position of next frame head；
S22. two sampled points are respectively slided before and after the appearance position of the next frame head of prediction, obtains a total of five sliding window number
According to, by sliding window internal symbol be divided into 16*16 grouping, do noncoherent accumulation；It is corresponding to take out Energy maximum value in five sliding windows
Sliding window simultaneously locks frame head.
3. a kind of -2 described in any item PCMA timing acquisitions and tracking according to claim 1, five cunnings of the taking-up
It the corresponding sliding window of Energy maximum value and locks frame head in dynamic window and further includes：
If the Best Point acquired is the first two sampled point any point, the super previous point of signal is indicated, if the Best Point acquired is
Latter two sampled point any point indicates that signal prolongs the latter point, if the Best Point acquired is just current point, indicates signal not
It does not also delay in advance.
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| CN117060985A (en) * | 2023-10-10 | 2023-11-14 | 南京控维通信科技有限公司 | Shipborne dual-antenna PCMA system signal recapturing method and device |
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