CN101299617B - Multimodule modulation-demodulation self-adaption method for wireless sensing network shortwave one-way communication - Google Patents
Multimodule modulation-demodulation self-adaption method for wireless sensing network shortwave one-way communication Download PDFInfo
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Abstract
The invention discloses a wireless sensing net short wave one-way communication multiple model modem self-adapting method, which presets a low speed, an intermediate speed and a high speed communication modes at the receiving terminals in the software radio mode, carries communication mode information at the sweep frequency frame head transmitted by the transmitting terminal, and executes modulation to the sweep frequency frame head in a high-reliability modulation mode, thereby the receiving terminal can simultaneously obtain subsequent data communication mode after capturing and confirming the sweep frequency frame head information, and execute demodulation to the subsequent information in corresponding communication mode after the sweep frequency head receiving is completed.
Description
Technical field
The present invention relates to wireless sensing network shortwave communication and adaptive communications field, particularly a kind of wireless sensing network shortwave one-way communication multimode modulation-demodulation self-adaption method.
Background technology
Wireless sensor network (Wireless Sensor Network; WSN) relate to multidisciplinary height intersection, the integrated hot research field, forward position of knowledge height; It combines sensor technology, embedding people formula computing technique, modern network and wireless communication technology, distributed information processing etc.; Can be through the information of all kinds of integrated microsensors cooperation ground monitorings in real time, perception and various environment of collection or monitoring target; And those information are sent through wireless mode; Simultaneously can also be sent to user terminal, thereby realize physical world, the connection of calculating the world and the human society ternary world, therefore with the network mode of organizing multi-hop certainly; Sensor network has very wide application prospect; Especially at many key areas such as military and national defense, industrial or agricultural, city management, biologic medical, environmental monitoring, rescue and relief work, anti-probably anti-terrorism, deathtrap Long-distance Control potential practical value is arranged all, caused the great attention of many national academias and industrial quarters, be considered to one of technology of power that 21 century had an immense impact on.
Wireless sensor network system generally includes two big types of sensor node, aggregation nodes (Sink node).The sensing node that has wireless transmission capability in a large number is battery-powered, is deployed at random in the monitored area, constitutes network through the self-organizing mode.Sensing node is uploaded to Sink with the interest incident through multi-hop mode between node, and sensing data possibly worked in coordination with or fusion treatment with other nodes in upload procedure, uploads comentropy and the purpose that reduces offered load thereby reach to improve.Sink after collecting the information of target area through internet or satellite transmission to terminal use or network data base.Existing wireless sensor network typical application sketch map is as shown in Figure 1.
From application, wireless sensor network is the network media of linking up between people and the physical world as the mankind's nerve endings network, has the characteristics of long-term unattended operation of network and ubiquitousization.Its demand field is very extensive; And applied environment and Network have diversified characteristic, all have huge otherness like the layout density of node, spacing, communication environment, transducer kind, object event probability of happening, data traffic size, QoS service guarantee etc.Therefore, the application and development of all kinds of wireless sensor networks must have the staged characteristic of development, is progressively set up and perfect to Ubiquitous Network by typical application.
The information transmission of wireless sense network is uploading of information in most cases, and node is uploaded information with short distance multi-hop form to the sink node; But as far as the sensing net of two-way communication, user or sink node place are to the node transmitting order to lower levels or carry out other whens scheduling, when promptly passing under the information; If adopt the mechanism identical with information uploading; Still need carry out the information interaction of multi-hop between node, the time that will cause each node to receive orders is inconsistent, has delayed order and has assigned speed; And in the transmittance process of information, expended the sensing net node lot of energy, influenced the life cycle of network.In the system background of this patent, because charge center and sensor measuring node apart from each other, and the information of issuing an order is shorter, when downlink information transmits, adopts the short wave communication mode, covers the direct transmission that reaches order through large-scale electric wave.In the native system, sensing node is because the restriction of energy can't carry out uploading of information through shortwave, thereby this system is a simplex system.
Short wave communication is meant that utilizing wavelength is that (frequency is the radio communication that 3 ~ 30MHz) electromagnetic wave carries out to 100 ~ 10m.Short wave communication can utilize earthwave or tens kilometers middle short-range communications to the hundreds of kilometer of lower ionosphere reflection carrying out; Upper ionosphere reflection carrying out telecommunications thousands of and even up to ten thousand kilometers in also can utilizing; By means of relay station, short wave communication even can carry out global communication.Short-wave radio set both can be large-scale fixed station; Also can be vehicle-mounted, carrier-borne, airborne or backpack travelling carriage, short wave communication equipment is simple, and be cheap; Flexible; And channel is survivable, thereby short wave communication is widely used in departments such as government, military affairs, diplomacy, meteorology, commerce for many years, is used for transmitting information such as language, literal, image, data.
The shortwave transmission channel is a comparatively abominable communication channel complicated and changeable, and the influence of many factors such as multipath effect, decline, phase fluctuation is selected and signal processing has proposed higher requirement the modulation system of short wave communication.
Under general environment, in order to guarantee the requirement to the error rate, below 200b/s, channel bit error rate is usually 10 always for traditional its transmission rate of shortwave data communication system
-2~ 10
-3The order of magnitude.In order to reach higher message transmission rate, the error rate is not higher than 10 simultaneously
-4, must adopt special modulation technique and processing mode.
TFSK is a kind of combination modulation, and it is on the basis of strong control of frequency displacement (FSK) and time-shift keying (TSK), to grow up.It is a kind of in the parallel modulation system, through with the high speed data conversion of serial for the low-speed parallel data that on different frequency, transmit reduce the influence of intersymbol interference, reach the purpose of high-speed transfer.Owing on frequency, separately, can reach the effect of frequency diversity, and, have certain error correction owing to the different coding mode is arranged to different code words.Adopt frequency diversity and parallel modulator approach, have anti-fading preferably ability, also can good communication under abominable channel circumstance, but transmission rate is lower.
PSK modulation system transmission rate is higher, adopt balancing technique after, also have certain anti-fading ability, but laser propagation effect is relatively poor under the relatively poor situation of channel circumstance, suitable channel circumstance is situation preferably.
Short wave channel is a time varying channel, and bad during the channel quality fashion that provides, simultaneously, the transmission amount of information size of transmitting terminal is also not quite identical to the requirement of transmission rate, thereby data modulation system and transmission rate have been proposed different requirement.
Summary of the invention
The objective of the invention is to deficiency, a kind of wireless sensing network shortwave one-way communication multimode modulation-demodulation self-adaption method is provided to prior art.
The objective of the invention is to realize through following technical scheme: a kind of wireless sensing network shortwave one-way communication multimode modulation-demodulation self-adaption method may further comprise the steps:
(4) the DSP acquiescence loads the frequency sweep module, and DSP peripheral hardware and AD converter at first are set after powering on, and receives table frequently from ARM then, gets into the frequency sweep circulation afterwards;
(5) after capturing the frequency sweep head and successfully knowing modulation system information, DSP will notify ARM frequency sweep result, and ARM loads PSK or FTSK demodulation module according to the information that the frequency sweep head comprises;
(6) DSP gets into and receives circulation, and ARM will judge whether to continue to receive according to demodulation result, as need not to continue to receive, and then ARM sends instruction and closes DSP, gets into initial condition this moment.
The invention has the beneficial effects as follows: the present invention presets low speed (FTSK modulation), middling speed (BPSK modulation) and high speed (QPSK modulation) three kinds of communication patterns at receiving terminal with the software radio mode; The frequency sweep frame head that sends at transmitting terminal carries communication mode information; And the frequency sweep frame head is modulated with the high reliability modulation system; Thereby make receiving terminal when catching affirmation frequency sweep frame head information, obtain the subsequent data communications pattern, after the reception of frequency sweep head finishes, promptly follow-up is carried out demodulation with the corresponding communication pattern.
Description of drawings
Fig. 1 is the sensor network sketch map,
Fig. 2 is system's up-downgoing transmission sketch map,
Fig. 3 is a transmitting terminal Base-Band Processing block diagram,
Fig. 4 is receiver structure figure,
Fig. 5 is a receiver baseband system general structure block diagram,
Fig. 6 realizes block diagram for the single sideband demodulation principle,
Fig. 7 realizes block diagram for the FTSK demodulation principle,
Fig. 8 realizes block diagram for demodulation principle,
Fig. 9 is the Viterbi decoding principle schematic,
Figure 10 is the systems soft ware flow chart.
Embodiment
Short wave channel is in the variation constantly; And multipath effect is serious; For under abominable communication condition, also better communicating by letter, must carry out a series of processing to signal at receiving terminal, disturb and decline, the bit of correcting a mistake obtain the lower error rate in the hope of reducing through offseting of certain way.
System adopts plurality of communication schemes, and mode one is sent for low speed is stable, and mode two is sent for high-speed burst.The stable transmission of low speed adopted the FTSK transmission means, through reducing the increase that data rate obtains every bit signal energy, reduces channel effect through the parallel transmission mode simultaneously, and can obtain frequency and time diversity.FTSK is insensitive to noise effect, still can right demodulation under the lower situation of signal to noise ratio.High-speed burst sends and adopts BPSK and QPSK modulation system respectively, reduces channel effect through equilibrium treatment, thereby obtains higher transmission rate, and the transmission of short message will be accomplished within a short period of time.
In the system design, realize information processing through software programming, and the dynamic-configuration systemic-function.The short-wave radio set intermediate-frequency section is to signal digitalized processing, realizes neatly on wideband digital filtering, Direct Digital frequency synthesis, the numeral/down-conversion, modulating/demodulating, error coding, channel equalization, signaling control, source encoding etc. with the software programming mode.
Software processing mode is provided convenience for selecting more excellent algorithm; Use adaptive equalization technique in the system,, reduce and disturb and decline according to signal reception result automatic adjustment equipment parameter; Adopt the channel coding/decoding mode simultaneously; Realize correction through certain redundancy,, reduce the error rate to greatest extent to reach the optimal communication effect to error code.
1, information is sent
Information transmitting terminal need realize multiple modulation system, is respectively applied for to satisfy burst and two kinds of substantive requirements of form of the stable transmission of low speed.Burst mode is applicable to channel condition situation preferably; In this case, the signal amplitude that receives is strong, satisfies the high-speed transfer requirement; Adopt the pattern of repetitive burst this moment; From a plurality of signals that repeat to send, choose the correct signal of transmission, can reduce of the influence of channel magnitude fluctuations, guarantee the correct reception of receiving terminal information to receiving.Low speed is stablized the situation that sending mode is applicable to that channel condition is relatively poor, in this case, the signal amplitude that receives a little less than, need concentration of energy can be guaranteed the right demodulation of receiving terminal.Burst mode adopts PSK modulation (demodulation) mode, and low speed is stablized sending mode and adopted FTSK modulation (demodulation) mode.
Information transmitting terminal has the chnnel coding ability.Initial data is carried out chnnel coding, and the system of can be provides certain error correcting capability, and primary signal can correct Solution be calculated by the assurance system under the few situation of mistake.This shows important to the transmission of the signal in the short wave channel is outstanding.
Data behind the information transmitting terminal framing can select FTSK modulation system or PSK modulation system to modulate through after the chnnel coding, but the control end selecting modulation mode is exported the signal of selected modulation system modulation at output control terminal, sends into radio-frequency head.
1) chnnel coding
Primary signal is mutual:
Carry out information interaction with the control subsystem, transferred data are read in by the framing mode.When modulation system is FTSK, read in 8 * 3 bytes; When modulation system is PSK, read in 30 * 5 bytes.Read in purpose ID simultaneously, the time, whether file transmits information such as finish, and adds as command frame with current number of repetition and the information such as position in paragraph.
CRC check and framing 1:
The signal that reads in is carried out the 16bitCRC coding, check results and data are formed Frame together, and add 8 bit frame heads in front.
Convolutional encoding: adopt (2,1,7) convolutional encoding, used multinomial is following:
b
0＝input+x
1+x
3+x
4+x
6
b
1＝input+x
3+x
4+x
5+x
6
Interweaving encoding: the data arrangement after will encoding becomes 16 * 32 matrix, and the matrix that generates 32 * 16 is then read (during the PSK modulation system).
Data arrangement behind the coding is become 8 * 18 matrix, and the matrix that generates 18 * 8 is then read (during the FTSK modulation system).
Framing 2:
Be used to catch with balanced frame head and do not participate in chnnel coding, solid aforementioned data frame also need be to signal framing again after passing through chnnel coding.When modulating for FTSK, before multi-frame, add and catch frame head, catch the agreement ID that frame head is repetition.When modulating for PSK, catching the frame head before multi-frame also need be added 64 balanced frame heads in each frame front.
2) FTSK modulation
Serial to parallel conversion: serial data becomes two channel parallel datas;
Encoder matrix: the input of two channel parallel datas, with the Quad Data Rate generation NCO frequency control signal of input data, select the different combinations mode.
Signal and frequency corresponding relation under the form 1:4FTSK modulation system
| Parallel input bit | The 4FTSK signal |
| 00 | f4?f3?f2?f1 |
| 01 | f1?f2?f3?f4 |
| 10 | f2?f4?f1?f3 |
| 11 | f3?f1?f4?f2 |
NCO: digital controlled oscillator, select its frequency jitter mode by encoder matrix.
3) PSK modulation
Information to input is carried out IQ two-way quadrature modulation.
Serial to parallel conversion: serial data is become two channel parallel datas (as being BPSK, then two paths of data is identical, as is QPSK, and then two paths of data is different);
Differential coding: initial data is carried out differential coding handle (BPSK and QPSK differential coding mode are different);
NCO: digital controlled oscillator produces sine and cosine wave;
32 rank root raised cosine filters of formed filter: α=0.5;
4) a frequency sweep modulation system
Because the relative PSK of FTSK has stronger antijamming capability, so swept-frequency signal adopts the FTSK modulation system.Specific practice is following: the frequency sweep head is 3 31 a Gold sign indicating number, and bit rate is 100chip/s, corresponds respectively to BPSK, QPSK and FTSK signal, and is listed like following table.
Form 2: frame head decisional table
| GOLD sign indicating number sequence | Represented signal modulation system |
| 1，1，0，0，1，0，0，0，1，1，1，1，0，1，0，1，1，0，0，1，0，0，0，1，1，1，1，0，1，0，1 | FTSK |
| 0，0，1，1，1，1，1，1，0，1，0，0，1，0，0，0，0，1，1，1，1，1，1，0，1，0，0，1，0，0，0 | BPSK |
| 0，0，1，1，0，0，1，1，0，0，1，0，1，0，1，1，0，1，1，0，0，1，1，0，0，1，0，1，0，1，1 | QPSK |
2, receiver structure
Receiver general structure sketch is as shown in the figure.Radio wave gets into receiver from antenna; Carry out processing such as signal reception, amplification, frequency conversion at radio-frequency module after; Deliver to DSP via the data after the AD conversion and carry out digital processing; Through separating the mediation channel-decoding, calculate initial data here, through Mailbox mechanism data are delivered to MCU and further handle, show or carry out corresponding operating.The program of control module and baseband module all when powering on from the FLASH dynamic load.ARM is responsible for RF switch, energy-conservation etc. control, switches RF spot when DSP then is responsible for frequency sweep through spi bus.
As shown be receiver baseband portion structure chart.Baseband processing module adopts serial AD to send in the DSP to radio frequency output carrying out AD sampling.Adopt two kinds of demodulation schemes in the DSP algorithm, respectively to FTSK modulation system and PSK modulation system.Two kinds of demodulation schemes move simultaneously, and the output signal is carried out channel decoding.The base band subsystem is made up of single sideband demodulation module, FTSK demodulation module, frequency sweep trapping module, PSK demodulation module and channel decoding module etc.
Input signal disturbs and noise outside band pass filter filtering band; Carry out single sideband demodulation then; At first get into the frequency sweep module behind the data after demodulating resampling; And receive frequently, and the demodulation module that calls according to the communication mode information decision that comprises in the frequency sweep information according to whether frequency sweep result decision is fixed on this frequency.After frequency and modulation system all were determined, the frequency sweep module was unloaded, and loads corresponding demodulation module.
In the FTSK demodulation module; Signal at first is input to trapping module and carries out the synchronous code acquisition of FTSK, also is the synchronous head of FTSK Frame simultaneously owing to catch employed Barker code, so we have also just obtained frame synchronization acquisition success the time; Tracker begins data are followed the tracks of synchronously subsequently; And export synchronizing information aid demodulation module and carry out the FTSK demodulation, the data after the demodulation are directly carried out deinterleaving, Viterbi and CRC check, export raw information at last.
The PSK demodulation module is configurable to be two kinds of BPSK and QPSK.In the BPSK demodulation module, input signal at first gets into the BPSK phase-locked loop and carries out base band demodulating and matched filtering, carries out frame synchronization then; BPSK base band data frame uses 63 GOLD sign indicating numbers as the frame synchronization head, and frame synchronization module is carried out correlation capturing in the sampled point level to input signal and local GOLD sign indicating number; Behind the acquisition success, signal is by resampling and carry out symbol synchronization, and the sampled point clock that recovers according to symbol synchronization carries out the bit-level sampling to signal; Carry out after the equilibrium of sampled value sequence importing soft Viterbi decoder after the deinterleaving, carry out at last exporting after the CRC check.QPSK is divided into two data branch roads of IQ, and each branch road adopts the frame structure identical with BPSK, so the QPSK demodulation module is all identical with BPSK demodulation module other parts except that phase-locked loop is different.
1) single sideband demodulation module
At first pass through band pass filter from the signal of AD input, the number of winning the confidence place frequency band (as being usb signal, during bandwidth 3KHz, being got 12KHz～15KHz) interior signal and is carried out the single sideband demodulation processing.The primary signal that in DSP, produces a local oscillation signal (local oscillation signal is adjustable) and import through AD multiplies each other, and the result after multiplying each other is through low pass filter, and one the tunnel carries out the Hilbert conversion, and another road time-delay back addition (subtracting) obtains upper sideband or lower sideband signal thus.
2) frequency sweep trapping module
The frequency sweep trapping module is according to the predeterminated frequency table that is provided by the master control subsystem, and the signal of each frequency is carried out demodulation process, and can judgement catch frame head.If can catch, be parked in this frequency and receive information, and see off and catch indication, as not catching, continue next frequency of scanning.
Each intermediate frequency data of handling 0.64 second during frequency sweep; If signal is arranged; This section intermediate frequency data must contain a complete GOLD sign indicating number sequence; This segment signal is carried out the FTSK demodulation process, in demodulation symbol, carry out the GOLD code searching, confirm the modulation system that transmitting terminal signals according to the sign indicating number sequence that searches.
3) FTSK demodulation module
Data behind the single sideband demodulation are sent into four band pass filters respectively, and the band pass filter center frequency points lays respectively at f1, f2; F3; F4 is last, and the signal that four filters are exported carries out envelope detection respectively, can adjudicate whether signal output is arranged on this frequency output point.Result according to envelope detection calibrates synchronised clock, and according to the synchronised clock sampling, sampled result is carried out matrix decoding, calculates probability and result that various combinations take place respectively, according to the final message data of probability judgement.
4) PSK demodulation module
Data and local local oscillator multiply each other the back through low pass filter behind the single sideband demodulation, obtain IQ two-way baseband signal, and signal is carried out sending into equalizer and carrying out equilibrium treatment after reduction of speed handles.Carry out at first in the equalizer that equalization data is caught and local balanced ideal data is set up mapping relations one by one, be used to produce equalizer coefficients.After treating equalizer convergence, initial data is following closely carried out equilibrium treatment.Judge simultaneously whether equilibrium is effective, if effectively, the balanced back of output data, if invalid, the data that output is not balanced.These data are carried out synchronous demodulation, can obtain initial data.
5) channel decoding module
The process of deinterleaving is read data for after finding frame head by the anti-order former state of interleaved order.
Viterbi decoding: the convolutional encoding of corresponding transmitting terminal, figure below are the theory diagram of Viterbi decoding.
Input and lock unit: for decoder provides correct branch road synchronous, each correct output belongs to n bit of a branch road.
Branch metric calculates: whenever n measurement value receiving a new branch road, the branch metric computing unit is just confirmed a new measurement value to the different branch road of each bar in the grid chart.
The storage of path metric and renewal: in this element, branch metric and former path metric addition of storing are carried out path metric relatively to the branch road that converges same node place then, select a paths to measure minimum path and remain.
The storage of information sequence and renewal: for the R=1/n convolution code; One group of new branch road information of every reception deposits the bit of selecting through " Jia-ratio-choosing " circuit that imaginary information bit will deposit path memory simultaneously at first in of thinking in and exports to decision unit in the path memory of 2N-1 state.Therefore, whenever receive a new branch road, 2N-1 path memory just upgrades once the imaginary information sequence that it is stored.Path memory length is decoding depth.
Judgement and output unit: when R=1/n convolution code optimal decoding, should select to have a bit that deposits in the earliest in the imaginary information sequence that minimal path measures and do decoding output.
In the Rayleigh channel, work as E
b/ n
0During=16dB, the convolutional encoding of employing QPSK/BPSK and FSK modulation system and (2,1,7) can satisfy the error rate basically and be lower than 10
-4, consider the error in the actual system design, at E
b/ n
0During=18dB, can satisfy the error rate basically and be lower than 10
-4If but adopted other channel correction means, could reduce E greatly
b/ n
0Requirement.Yet, possibly there is burst error in the short wave channel, the error correcting capability of system is had higher requirement.When interleave depth and short wave channel characteristic are complementary, can correct most burst error, reduce the error rate.
At last, the primary signal that calculates is carried out CRC check,, then information is sent to the control subsystem, be responsible for storage by the control subsystem and show if information is correct.
3, the DSP of baseband system realizes
1) systems soft ware flow process
Fig. 9 is the software flow pattern of system, and the realization of each module is set forth in preamble among the figure.Like figure, the DSP acquiescence loads the frequency sweep module, and DSP peripheral hardware and AD converter at first are set after software powers on, and receives table frequently from ARM then, gets into the frequency sweep circulation afterwards.After capturing the frequency sweep head and successfully knowing modulation system information, DSP will notify ARM frequency sweep result, and ARM loads PSK or FTSK demodulation module according to the information that the frequency sweep head comprises.After this, DSP gets into and receives circulation, and ARM will judge whether to continue to receive according to demodulation result, as need not to continue to receive, and then ARM sends instruction and closes DSP, and this moment, software got into initial condition.
2) hardware handles capability analysis
If the input signal sampling rate is made as 96kHz.
A) during single sideband demodulation
Band pass filter (64 rank), the multiply-add operation of the about 96kHz * 64=6.144MIPs of needs.
Down-conversion produces the 96kHz cosine and sine signal, needs the computing of tabling look-up of about 200kHz.
Through low pass filter, need the multiply-add operation of about 96kHz * 13=1.248MIPs.
After the reduction of speed sampling, data rate will be for about 12kHz.
Through the Hilbert conversion, need the multiply-add operation of about 12kHz * 64=1.248MIPs.
B) FTSK separates when being in harmonious proportion decoding
Signal needs the multiply-add operation of about 4.992MIPs through four band pass filters (64 rank).
Envelope detection needs the comparison operation of about 12kHz * 64=1.248MIPs.
Computing synchronously, the plus and minus calculation of the about 12kHz * 10=0.120MIPs of needs.
Decoding matrix, the plus and minus calculation of the about 400Hz * 20=0.06MIPs of needs.
Deinterleaving needs the storage computing of about 100bps.
Viterbi decoding, the operand of the about 100bps * 160=0.1667MIPs of needs.
C) PSK separates when being in harmonious proportion decoding
Through low pass filter, need the multiply-add operation of about 12kHz * 13=0.156MIPs.
Equalizer: the multiply-add operation that needs about 12KHz * 64=1.248MIPs.
Equalizer coefficients is adjusted, and needs the multiply-add operation of about 12KHz * 64=1.248MIPs.
Deinterleaving needs the storage computing of about 1000bps.
Viterbi decoding, the operand of the about 1000bps * 160=1.667MIPs of needs.
In sum, above-mentioned operand is estimated in the 20MIPs magnitude, as long as the DSP arithmetic speed greater than 20MIPs, can satisfy the computing requirement.
Claims (1)
1. a wireless sensing network shortwave one-way communication multimode modulation-demodulation self-adaption method is characterized in that, may further comprise the steps:
(1) the DSP acquiescence loads the frequency sweep module, and DSP peripheral hardware and AD converter at first are set after powering on, and receives table frequently from ARM then, gets into the frequency sweep circulation afterwards;
Wherein the frequency sweep circulation specifically comprises:
Frequency is set;
Digital band pass is handled;
Single sideband demodulation is handled;
According to the predeterminated frequency table, the signal of each frequency is carried out demodulation process, can judgement catch frame head, if can catch, is parked in this frequency and receives information, and see off and catch indication, as not catching, continues next frequency of scanning;
(2) after capturing the frequency sweep head and successfully knowing modulation system information, DSP will notify ARM frequency sweep result, and ARM loads PSK or FTSK demodulation module according to the information that the frequency sweep head comprises;
If loaded the FTSK demodulation module; Signal at first is input to trapping module and carries out the synchronous code acquisition of FTSK, also is the synchronous head of FTSK Frame simultaneously owing to catch employed Barker code, so we have also just obtained frame synchronization acquisition success the time; Tracker begins data are followed the tracks of synchronously subsequently; And export synchronizing information aid demodulation module and carry out the FTSK demodulation, the data after the demodulation are directly carried out deinterleaving, Viterbi and CRC check, export raw information at last;
If loaded the PSK demodulation module, wherein the PSK demodulation module is configurable is two kinds of BPSK and QPSK, and in the BPSK demodulation module, input signal at first gets into the BPSK phase-locked loop and carries out base band demodulating and matched filtering, carries out frame synchronization then; BPSK base band data frame uses 63 GOLD sign indicating numbers as the frame synchronization head, and frame synchronization module is carried out correlation capturing in the sampled point level to input signal and local GOLD sign indicating number; Behind the acquisition success, signal is by resampling and carry out symbol synchronization, and the sampled point clock that recovers according to symbol synchronization carries out the bit-level sampling to signal; Carry out after the equilibrium of sampled value sequence importing soft Viterbi decoder after the deinterleaving, carry out at last exporting after the CRC check; QPSK is divided into two data branch roads of IQ, and each branch road adopts the frame structure identical with BPSK, so the QPSK demodulation module is all identical with BPSK demodulation module other parts except that phase-locked loop is different;
(3) DSP gets into and receives circulation, and ARM will judge whether to continue to receive according to demodulation result, as need not to continue to receive, and then ARM sends instruction and closes DSP, gets into initial condition this moment.
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| CN104079515A (en) * | 2013-03-29 | 2014-10-01 | 华为技术有限公司 | Adjustment method of modulation mode and modems |
| CN108270487B (en) * | 2017-12-11 | 2019-10-08 | 上海微波技术研究所（中国电子科技集团公司第五十研究所） | Fibre-optic transmission system (FOTS) based on ultrashort wave radio set |
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| CN110191420B (en) * | 2019-05-15 | 2021-01-15 | 成都贝亚特科技有限公司 | Anti-interference wireless intercom system and installation method |
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