CN101977293A - Method for estimating time delay of ground broadcast signals of digital television - Google Patents
Method for estimating time delay of ground broadcast signals of digital television Download PDFInfo
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Abstract
The invention discloses a method for estimating time delay of ground broadcast signals of a digital television, which belongs to the field of digital television broadcasting and wireless navigation positioning. The method comprises the following steps of: by using a transmitting time marker extracted from transmission code steams which are output from a digital television receiver through demodulation coding, reforming the transmission code streams into television signal frames which have same standard and same time sequence with transmitted signals, and then performing coding and modulation the same as those of a sending terminal in turn frame by frame; reforming a transmitted signal sample of a transmitting station which is nearest to a mobile receiving terminal; and performing cross-correlation operation on the sample and a stored received signal sample so as to accurately estimating the time delay for the broadcast signals transmitted by all single-frequency network transmitting station to reach a mobile terminal through different transmission paths. The method has high time delay estimation accuracy, is simple to implement, and has a low cost and a wide application range.
Description
Technical field
The present invention relates to a kind of delay time estimation method of digital television ground broadcast signal, belong to digital television broadcasting and radionavigation positioning field.
Background technology
One, the major defect of existing navigation system
Location technology has obtained extensive use in the national economy every field, has produced huge economic benefit and social benefit.At present, the focus of research is confined to satellite positioning tech more both at home and abroad.Such as: the global positioning system of the U.S. (GPS), the Galileo system (Galileo) in Europe, the Big Dipper navigation system of Muscovite GLONASS system and China.
With most widely used GPS is example.In order to improve detection performance and the secret ability for faint satellite-signal, GPS has adopted the spread spectrum of pseudo noise code, and satellite navigation message is become combinational code through the pseudo noise code spread spectrum, and the carrier wave to the L frequency range carries out the phase shift keying modulation again.GPS has adopted P sign indicating number and two kinds of pseudo noise codes of C/A sign indicating number.Wherein the P sign indicating number is to aim at military accurate measurement sign indicating number, and the absolute prohibition unauthorized user uses; The C/A sign indicating number is used for bigness scale and catches, and uses for general commercial receiver.The frequency of C/A sign indicating number is 1.023MHz, and repetition period 1ms, code length are 1023, and intersymbol is equivalent to 300m apart from 1 μ s; The P code frequency is 10.23MHz, and 266.4 days repetition periods, intersymbol is equivalent to 30m apart from 0.1 μ s.
But the major defect of the global position system of GPS and so on is:
1) is 60% at urban district location probability, indoorly almost can not finishes the location;
2) owing to multipath effect, satellite orbital error, ionosphere delay effects etc. influence positioning accuracy;
3) the location real-time is poor, needs 30s consuming time or longer time just can change normal mode of operation over to when cold start-up.
Based on the mobile phone positioning system of digital ground Cellular Networks, major defect is:
1) the mobile phone signal transmitting power is low, is subjected to the influence of noise jamming and base station location big during reception;
2) effect is intercepted in the network existence;
3) user can not directly obtain the positional information of oneself, just can finish but unite a plurality of base stations by central platform, and the confidentiality of customer location is affected.
Therefore, how to realize the location, become Study of location and hot of research and development by existing other wireless network.
Two, Digital Television Terrestrial Broadcasting navigation system
Along with the issuing and implementation of Digital Television (DTV) terrestrial broadcasting standard and mobile TV standard, ground base station is Large scale construction, and the Digital Television Terrestrial Broadcasting net forms gradually.Digital Television is in order to transmit high-quality digitized video and audio signal, and its signal transmission has following characteristics:
1) transmitting power is big, antenna gain is high and rest on the ground, so the energy of DTV ground broadcast signal is far longer than the energy requirement that global position system can provide than the high 40dB of gps signal;
2) bandwidth of DTV ground broadcast signal is about 6 times of GPS occupied bandwidth, can alleviate the multipath effect of signal transmission;
3) the do not transmitted influence of Doppler frequency shift and ionosphere propagation delay time;
4) signal transmission rate higher than GPS.
For example, the DTV of United States advanced television systems committee (ATSC:Advanced Television System Committee) standard can transmit 19.3Mb/s at the terrestrial broadcasting channel of 6MHz bandwidth; Digital video broadcast-terrestrial (DVB-T:Digital Video Broadcasting-Terrestrial) standard message transmission rate in the 6MHz bandwidth in Europe reaches as high as 23.8Mbps, reaches as high as 31.67Mbps in the 8MHz; Integrated Services Digital Broadcasting (ISDB:Integrated Services DigitalBroadcasting) standard message transmission rate in the 6MHz bandwidth of Japan reaches as high as 23.23Mbps; The digital television ground broadcast transmission system national standard (GB20600-2006) " digital television ground broadcast transmission system frame structure, chnnel coding and modulation " of China (DMB-TH) also can be supported the rate of loading of 24.364Mbps.In other words, if be that 20Mbps (being that code frequency is 20MHz) calculates by the average transmission code check, then intersymbol is equivalent to 15m apart from being 0.05 μ s, range accuracy even also double than the P sign indicating number of GPS.
In fact, based on the positioning accuracy of the Passive Positioning System in radio radiation source and carrier frequency, bearing mode (single carrier, multicarrier), symbol period, modulation system and the data frame structure etc. of emitter Signals relation is arranged all.Adopt the DTV signal of ATSC standard to position through demonstration at ConUS, precision can reach meter level, has not only substantially exceeded the positioning accuracy based on the mobile cellular communication network, also is much better than the civilian positioning accuracy of utilizing GPS.Therefore, position, become the focus of research, and we have promptly invented the radio combined positioning method (ZL200510095536.7) based on digital broadcasting-television signal as far back as 2005 by means of existing digital television ground broadcast signal.
Three, the new problem brought of single frequency network
According to the domestic and international research result, utilize radio signal to carry out the short-cut method and the key technology thereof of Passive Positioning, be to estimate radio signal as far as possible exactly to propagate into time delay between travelling carriage (MS) the user reception antenna that need to determine self-position from transmitting base station (BS) antenna as radiation source, abbreviate the estimation of the time of advent (TOA) as, or time delay is estimated.And in many fields such as radar, sonar, GPS, navigation, though time delay estimates it is the ripe common technology of a basis principle, and widely use already.
Because radio wave is with light velocity propagation, its propagation velocity can be considered constant substantially, and from the relation of plane geometry, apart from the MS that BS transmitting antenna time delay equates, all is positioned at the BS transmitting antenna and is the center of circle, multiply by on the circumference that the light velocity is a radius with this time delay.Therefore, for the only plane coordinates of determining a MS, need at least to receive simultaneously from the transmitting of 3 different B S, and estimate 3 corresponding time delay values.For the TV station of past employing simulation system or the signal that launch in the broadcasting station, we are not difficult to accomplish this point, because they are (promptly the adopting different channels) of adopting diverse transmit frequency respectively.Even for the identical program of content (for example relaying " news hookup " of the Chinese Central Television (CCTV) or Central People's Broadcasting Station simultaneously), they also must adopt different transmit frequency (promptly adopting channel or the frequency of distributing to oneself).This makes orientation problem not have ambiguity at least on principle: only need receive simultaneously respectively from 3 different B S and different the transmitting of frequency with 3 receivers that are operated in different channel, and estimate 3 corresponding time delay values and get final product.
But, after broadcast television signal is realized the digitlization transmission, guaranteed that technically different BS can adopt identical single-frequency to broadcast identical program simultaneously fully, and in order to improve the availability of frequency spectrum and to improve reception, in application, also implement so just, be referred to as single frequency network (SFN) broadcasting.
The SFN broadcasting of Digital Television or digital audio has no doubt greatly improved covering performance and reception, but brought the puzzlement on the principle: because of the received signal of MS digital receiver that is tuned on a certain channel based on the Passive Positioning of digital television ground broadcast signal, may be from the diverse BS transmitting antenna in several (for example 3) geographical position, and the reception antenna of present vehicle-mounted radio and in-car TV machine is an omnidirectional, so if MS utilizes this directionless optionally antenna to receive the SFN digital television signal of the no difference on the frequency opposite sex, then according to existing principle and technology, particularly when MS does not know current oneself accurate position, can not right area divide same frequency TOA from different B S.
Summary of the invention
The present invention is directed to the deficiencies in the prior art, propose a kind of under the condition that does not have each Digital Television Terrestrial Broadcasting transmitting station azimuth information, in single frequency network, estimate to arrive the method for the propagation delay time of mobile receiving terminal, be used for determining the current geographic position of portable terminal from the digital television signal of different transmitting stations.
This method is to utilize sign launch time that extracts from the transmission code stream of digital television receiver demodulation coding output, after this transmission code stream reformulated TV signal frame with transmit identical standard and identical sequential, carry out coding and the modulation same more frame by frame successively with transmitting terminal, reconstruct the sample that transmits with the nearest transmitting station of mobile receiving terminal, received signal sample with this sample and storage carries out computing cross-correlation again, thereby estimates all single frequency network transmitting station broadcast singals arrive portable terminal through different transmission path time delay.
The present invention has following technique effect:
1) time delay estimated accuracy height
This method can make full use of the signal advantage of existing DTV transmission standard and the synchronous characteristics of single frequency network transmission, the running fix user can be directly the transmitting of the nearest DTV transmitting station of base band, intermediate frequency even radio frequency reconstruct, and be used for estimating at one stroke all single frequency network transmitting station broadcast singals arrive mobile receiver through different transmission path time delay.Because the bit rate of DTV exceeds order of magnitude of C/A sign indicating number of GPS, and the transmitting carrier frequency of DTV is higher than at least one order of magnitude of P sign indicating number of GPS, so the time delay estimated accuracy of this method is far above gps system, and be expected to be used for the location (Internet of Things as indoor goods is used) that gps signal can't arrive part, thereby provide direct illustration for the hi-Fix that utilizes digital television ground broadcast signal to carry out sub-meter grade.
2) realize easy economy
At present all mobile receivers that can receive DTV standard (which country, which kind of standard) signal all comprise channel equalization link or function; The commercial integrated circuit (IC) chip of all DTV receivers all contains the pin that can export the transmission code stream that is demodulated at present.Therefore, except the hardware that is used for time delay estimation and positioning calculation that all running fix terminals all need, this method only need increase the DTV modulation hardware of respective standard, and all reception processing capacities are then finished by the DTV receiver.It is worthy of note, compare that because the DTV receiver has been eliminated Doppler frequency shift, thereby this method only needs the cross-correlator of a fixed frequency to get final product with the processing procedure of GPS receiver.Thereby on the basis of DTV receiver, only needing increases soft on a small quantity, hardware spending, can realize hi-Fix.
3) be suitable for face width
This method can both be carried out the time delay estimation under base band, intermediate frequency and radio frequency situation, thereby can be according to the hardware implementation cost of concrete required precision and economic index control cross-correlator, farthest to adapt to the positioning requirements of the different occasions of different user.Simultaneously, technical thought of the present invention also is applicable to all Digital Television and digital broadcast transmission standard and system on principle.
Description of drawings
Fig. 1 is the overall procedure block diagram of the inventive method.
Fig. 2 is the transmitting terminal theory diagram of the digital television ground broadcast transmission system of Chinese Industrial Standards (CIS).
Fig. 3 is that broad sense cross-correlation time delay is estimated the principle of operation block diagram, and among the figure: x (t), y (t) represent the received signal baseband sample of transmit sample and the storage that reconstruct respectively; X (f), Y (f) are respectively the corresponding frequency spectrum of x (t), y (t);
Conjugation for X (f); G
Xy(f) be the cross-correlation power spectrum of x (t) and y (t); R
Xy(τ) be the cross-correlation function of x (t) and y (t).
Fig. 4 is the present invention at the place an order time delay estimation effect figure of base station of base band situation, and wherein: Fig. 4 (a) is that time delay is estimated general picture; Fig. 4 (b) is the partial enlarged drawing of Fig. 4 (a) time delay estimated result.
Fig. 5 is the time delay estimation effect figure of the present invention 3 base stations under the base band situation, and wherein: Fig. 5 (a) is that time delay is estimated general picture; Fig. 5 (b) is that the time delay of base station 1 is estimated enlarged drawing; Fig. 5 (c) is that the time delay of base station 2 is estimated enlarged drawing; Fig. 5 (d) is that the time delay of base station 3 is estimated enlarged drawing.
Fig. 6 is the present invention at the place an order time delay estimation effect figure of base station of 600MHz carrier frequency situation, and wherein: Fig. 6 (a) is that time delay is estimated general picture; Fig. 6 (b) is the partial enlarged drawing of Fig. 6 (a) time delay estimated result.
Fig. 7 is the time delay estimation effect figure of the present invention 3 base stations under 600MHz carrier frequency situation, and wherein: Fig. 7 (a) is that time delay is estimated general picture; Fig. 7 (b) is that the time delay of base station 1 is estimated enlarged drawing; Fig. 7 (c) is that the time delay of base station 2 is estimated enlarged drawing; Fig. 7 (d) is that the time delay of base station 3 is estimated enlarged drawing.
Embodiment
Effective synchronous code speed of the digital television ground broadcast signal transmission standard of issuing in the world (national standard that comprises China) is higher than order of magnitude of C/A sign indicating number of GPS at least at present, and this provides theoretical assurance with regard to the positioning accuracy that obtains above GPS to the system that utilizes digital television ground broadcast signal to position.In addition, because the pseudo-code spread spectrum system that the transmission of the signal of DTV does not all adopt GPS (and other global position system) to be adopted, so time delay estimates further to bring up to carry out related operation on signal(-) carrier frequency, so precision can also be higher.
Travelling carriage (MS) user side desire utilize single-frequency radio network signal to be correlated with key that time delay estimates is to find or to generate voluntarily a transmitted waveform copy that does not contain any NLOS component and have only (and preferably a first) LOS composition.Utilize such transmitted waveform copy and received signal to carry out cross-correlation, will locate to produce relevant peaks at every paths component (no matter being LOS or NLOS) of received signal, and the distance between relevant peaks is the relative time delay between each propagation path.As long as can determine article one LOS footpath wherein and the time delay that indicates with respect to launch time thereof in view of the above, can know the absolute time delay of each paths successively by inference with respect to launch time.
How to obtain such transmitted waveform copy that is equivalent to the BS nearest apart from MS? in fact, in radio receiver, channel estimating and channel equalization are exactly the common method that weakens or eliminate multipath component, and through being remained after the comparatively perfect channel equalization, just only corresponding to the signal component in (or directly having been strengthened by other) first footpath.If really exist LOS path in the transmitting of that BS nearest apart from MS this moment, what then remained after the channel equalization just only transmits corresponding to this BS.This signal separated be in harmonious proportion after the transport stream that channel decoding obtains being launched, according to handling, promptly obtain the transmitted waveform copy of that nearest BS again with identical DTV coding of transmitting terminal and modulation system.
According to above-mentioned thinking, the theing contents are as follows of the inventive method:
Sign launch time that utilization is extracted from the transmission code stream of digital television receiver demodulation coding output, after this transmission code stream reformulated TV signal frame with transmit identical standard and identical sequential, carry out coding and the modulation same more frame by frame successively with transmitting terminal, reconstruct the sample that transmits with the nearest transmitting station of mobile receiving terminal, received signal sample with this sample and storage carries out computing cross-correlation again, thereby estimates all single frequency network transmitting station broadcast singals arrive portable terminal through different transmission path time delay.
Digital Television Terrestrial Broadcasting transmission standard and base band time delay with China are estimated as example, and the method flow of accurately estimating DTV ground broadcast signal propagation delay time in single frequency network proposed by the invention as shown in Figure 1.Its concrete implementation step is as follows:
1) the DTV ground broadcast signal that receives is down-converted to the storage of zero intermediate frequency post-sampling;
2) the digitlization zero intermediate frequency signals is carried out channel equalization and demodulation, decoding, obtain the transmission code stream of digital television ground broadcast signal;
3), after decoding, extract the transmission time information of this frame the data message frame head that obtains, for the signal frame of reconstruct provides the sequential identical with transmitter according to the indicated time tag position of different DTV standards;
4) signal frame with reconstruct carries out coding and the modulation (as shown in Figure 2) same with transmitting terminal, and carries out successively frame by frame, can reconstruct the sample that transmits of that nearest transmitting station;
The received signal baseband sample of the transmit sample and the storage that 5) will reconstruct carries out computing cross-correlation as shown in Figure 3, can obtain locating required time delay and estimate.That what there is no is different with general cross-correlator on principle for Fig. 3, just carries out at frequency domain in order to reduce operand, utilizes fast Fourier transform (FFT) and inverse fast Fourier transform (IFFT) to realize mutual conversion between time domain and the frequency domain for this reason.
In order to improve the time delay estimated accuracy, be correlated with in base band except above-mentioned, can also remove to modulate the radio-frequency carrier of DTV with frame reorganization gained signal among Fig. 1, and carry out relevant time delay estimation with the received signal (first digitlization) before the down-conversion.
Experimental result:
Below delay time estimation method of the present invention is compared checking respectively under single base station/many base stations and base band/radio frequency situation.Channel model is selected for use in the DTV research field and is used wider Brazil A channel, and do not have NLOS component in the received signal this moment, so that the time delay estimation effect when more clearly observing many base stations.Experiment parameter is chosen as follows:
1) under single base station, the time delay of receiving terminal and base station is 200 μ s;
2) under many base stations, select 3 base stations for use, the distance of receiving terminal and base station 1,2,3 is respectively 160 μ s, 180 μ s and 210 μ s.
Experiment 1: time delay estimated result of the present invention under the checking base band condition.
Shown in Fig. 4 (a), Fig. 4 (b) and Fig. 5 (a), Fig. 5 (b), Fig. 5 (c), Fig. 5 (d), visible the inventive method time delay estimation effect for single base station and many base stations under the base band situation is all fine.
Experiment 2: checking time delay estimated result of the present invention under 600MHz carrier frequency situation.
Shown in Fig. 6 (a), Fig. 6 (b) and Fig. 7 (a), Fig. 7 (b), Fig. 7 (c), Fig. 7 (d), compare with Fig. 5 with Fig. 4 respectively, visible the inventive method has all surpassed the result of base band cross-correlation for the time delay estimated accuracy of single base station and many base stations under the radio-frequency carrier situation again.
In a word, delay time estimation method of the present invention can obtain good estimation effect to the time delay under the different condition.
Claims (3)
1. the delay time estimation method of a digital television ground broadcast signal is characterized in that:
In this method, the received signal sample of portable terminal utilization storage and the sample that transmits of reconstruct carry out computing cross-correlation, thereby estimate all transmitting station broadcast singals arrive portable terminal through different transmission path time delay.
2. the delay time estimation method of digital television ground broadcast signal according to claim 1, it is characterized in that: the restructuring procedure of the described sample that transmits is: utilize sign launch time that extracts from the transmission code stream of digital television receiver demodulation coding output, after this transmission code stream reassembled into TV signal frame with transmit identical standard and identical sequential, carry out coding and the modulation same more frame by frame successively with transmitting terminal.
3. the delay time estimation method of digital television ground broadcast signal according to claim 1, it is characterized in that: the restructuring procedure of the described computing cross-correlation and the sample that transmits carries out in the base band of digital television signal, or carries out on the intermediate frequency of digital television receiver or radio-frequency carrier.
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| CN104181501A (en) * | 2014-08-21 | 2014-12-03 | 上海交通大学 | Positioning system and positioning method based on ground digital radio and television signals |
| CN105469799A (en) * | 2015-12-01 | 2016-04-06 | 北京科技大学 | Audible sound positioning method and system based on hidden channel |
| CN107222274A (en) * | 2017-07-11 | 2017-09-29 | 成都德芯数字科技股份有限公司 | Delay detection method and system |
| CN108152810A (en) * | 2017-03-24 | 2018-06-12 | 郑州微纳科技有限公司 | The transmitting of passive radar signal and reception system based on DTMB radiated waves |
| CN112929710A (en) * | 2019-12-05 | 2021-06-08 | 苏州东奇信息科技股份有限公司 | Method for estimating time delay of digital television ground broadcast signal of single frequency network |
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| CN104181501A (en) * | 2014-08-21 | 2014-12-03 | 上海交通大学 | Positioning system and positioning method based on ground digital radio and television signals |
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| CN105469799A (en) * | 2015-12-01 | 2016-04-06 | 北京科技大学 | Audible sound positioning method and system based on hidden channel |
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| CN112929710A (en) * | 2019-12-05 | 2021-06-08 | 苏州东奇信息科技股份有限公司 | Method for estimating time delay of digital television ground broadcast signal of single frequency network |
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Application publication date: 20110216 |