CN106054226B - A kind of mobile cellular net combines satellite-signal blind zone positioning method with satellite navigation system - Google Patents

Abstract

The invention belongs to the field of electronic communication and automatic control, and relates to a mobile cellular network and a satellite navigation system jointly realizing a receiver positioning method in a satellite signal blind area. In this positioning method, the receiver uses the satellite signal forwarded by the base station to first calculate the position coordinates independently by using two different methods: one method is that the receiver derives the position coordinates at the next time based on the positioning results at the previous time; The method is that the receiver uses satellite signals to measure the pseudo-range from the base station to the receiver, and then uses the principle of triangulation to calculate the position. Then, the receiver combines the positioning results obtained by the two methods as observations, and uses the Kalman filter algorithm to filter the results to determine the end user's position coordinates. In actual application, the present invention has low deployment cost and easy installation, and can obtain high positioning accuracy.

Description

A mobile cellular network and satellite navigation system combined satellite signal blind area positioning method

technical field

The invention belongs to the fields of electronics, communication and automatic control, and relates to user positioning based on navigation satellites, in particular to user positioning in blind areas of navigation satellite signals.

Background technique

In blind areas of navigation satellite signals, such as inside buildings or tunnels and under viaducts, user receivers generally cannot directly obtain satellite signals, that is, they cannot directly use navigation satellite signals to calculate positions. In this case, if it is still necessary to use satellite signals to achieve positioning, it is necessary to amplify and forward the satellite signals through other devices located in areas with good satellite signals so that users in the blind area can receive effective satellite signals to achieve positioning, such as for indoor Satellite signal repeater forwarding technology used for positioning, etc. However, for environments with incomplete infrastructure, the deployment of satellite repeaters will encounter great challenges. At present, the coverage rate of the mobile cellular network is very high, the coverage radius of the cell base station is gradually reduced, and the blind area of the mobile signal is small. Satellite signals are used to achieve positioning; and in areas where users can directly receive satellite signals, the receiver can use the forwarded satellite signals to further improve positioning accuracy.

Contents of the invention

The invention provides a mobile cellular network and a satellite navigation system to jointly realize a receiver positioning method in a satellite signal blind area. Firstly, the satellite signal is forwarded by a mobile cellular base station. When a base station receives a navigation satellite signal, it first processes the signal to obtain navigation data, then modulates the navigation data with a new spreading code (different from the spreading code used by all navigation satellites), and then uses the same navigation The signal is transmitted with a certain power in the frequency band used by the satellite signal. When retransmitting the satellite signal, the base station uses certain signal processing to maintain the code phase, carrier phase and Doppler frequency shift of the original satellite signal. The transmitting power of the base station to forward the satellite signal should ensure that each receiver can receive the satellite signal forwarded by three or more base stations at the same time. The receiver can realize navigation and positioning by using the received and forwarded satellite signals. The receiver will use two different methods for positioning, and then use the Kalman filter to fuse the data measured by the two methods to achieve the final high-precision positioning.

A kind of mobile cellular network and satellite navigation system combined satellite signal blind area positioning method of the present invention comprises the following steps:

Step 1: Use two positioning methods for positioning

The present invention requires the cellular network base station to be able to forward navigation satellite signals, and the signal forwarding power meets relevant regulations and can ensure that each user receiver can at least receive satellite signals forwarded by three or more base stations at any time. The coordinates of each base station are accurately measured and can be transmitted to the user receiver through the cellular network signaling data. Each base station first needs to process the received satellite signals to obtain ephemeris data. Since the mobile network traffic handled by each base station at the same time may be different, the delay time for satellite signal processing may also be different. Different signal processing delays will cause ranging errors from the receiver to the base station, even if the receiver performs differential processing on the signals from different base stations. The present invention adopts two kinds of positioning methods, specifically as follows:

The first positioning method:

First, signal forwarding processing time errors are eliminated. Note that the time elapsed for the signal measured by the receiver at time t _k to be forwarded from the satellite s _i to the receiver via the base station b _j is but

in, is the time for the signal to travel from satellite s _i to base station b _j ; is the time from the base station b _j to the receiver; δt _c is the clock difference of the receiver; is the propagation error experienced by the signal from the satellite s _i to the base station b _j and then to the receiver; It is the time it takes for the signal to arrive at the base station antenna, be processed by the base station, and then be transmitted from the base station antenna; represents other measurement errors.

Differentializing the signal propagation times from the same satellite and forwarded to the receiver via the same base station but measured at different times yields:

Among them, the receiver clock error δt _c will be eliminated;

The interval between t ₀ and t ₁ is less than or equal to 1 second, and Consider zero. The receiver can obtain the satellite coordinates after decoding the satellite data. When the receiver accesses the base station, it can obtain the coordinate information of the base station through signaling, It can be obtained through satellite and base station coordinate calculation.

The receiver performs a differential operation on the propagation time measured at two consecutive moments (t ₀ and t ₁ ) of the signals forwarded by different base stations, namely

Let can be expressed as in i=0,1, that is, the coordinates of the user at time t _i ; is the coordinates of base station b _j (j=1,2,3), and Represents the distance from base station b _j to user receiver at time t _i . Formula (3) can be further expressed as:

Formula (4) can be further organized as:

If the position of the user receiver at time t ₀ is known, the position of the receiver at time t ₁ can be calculated according to formula (5). The calculated user location is

The second positioning method:

When the user receiver receives the retransmission signal from the base station, it can use the signal to measure the time elapsed from the satellite to the user signal through the base station time measured at instant t _k Will be as shown in formula (1). Signals from the same satellite are forwarded through different base stations, and the time required for them to reach the user's receiver will be different. Suppose the same satellite (s ₁ ) signal is forwarded by four base stations b _j (j=1,2,3,4), then

Let is the measured value, and is the time required for the signal to propagate from satellite s ₁ to base station b _j , which can be calculated from the coordinates of satellite s ₁ and base station b _j . Can be expressed as follows:

The base stations b _j (j=1, 2, 3, 4) are generally relatively close to each other, and the receiver can receive the forwarded signals from these four base stations at the same time; considered equal. Satellite signal forwarding processing time per base station Equality is assumed in this positioning method. According to formula (8), it can be further obtained:

Let in is the coordinates of the user receiver at time t _k ; is the coordinates of base station b _j . Formula (9) can be written as:

According to formula (10), the user position coordinates can be calculated and obtained The closed-form solution of , remember the calculated user position as

The second step: use the Kalman filter to fuse the two positioning results

In the first step, the main errors of the positioning results of the two methods come from different factors. If the two positioning results are combined to determine the receiver coordinates, the influence of each factor on the positioning error can be weakened, and the positioning accuracy can be improved. Therefore, the positioning results of the two positioning methods in the first step are used as observation values to filter the results with a Kalman filter to determine the final positioning result.

Assuming that the state transition matrix of the Kalman filter is an identity matrix, the state transition model is:

in represents the coordinates of the user's location at the kth measurement moment, while is the process noise vector.

The positioning results measured by the first positioning method and the second positioning method are combined as the observation value of the Kalman filter, that is,

in and

The relationship matrix H(k) between the observed value and the state value is defined as:

and Defined as a unit matrix. The corresponding measurement noise matrix is defined as:

Among them, v ₁ (k) and v ₂ (k) are the corresponding measured values and measurement error and noise. The observation model is

Filtering using a standard Kalman filter algorithm yields the end user location coordinates.

The joint positioning method of the mobile cellular network and the satellite navigation system proposed by the invention can improve the positioning accuracy of users, and at the same time, the deployment cost is low and the installation is easy in practical applications.

Detailed ways

The first positioning method:

Firstly, the signal forwarding processing time error is eliminated. Note that the time elapsed for the signal measured by the receiver at time t _k to be forwarded from the satellite s _i to the receiver via the base station b _j is then there is

in, is the time for the signal to travel from satellite s _i to base station b _j ; is the time from the base station b _j to the receiver; δt _c is the clock difference of the receiver; is the propagation error experienced by the signal from the satellite s _i to the base station b _j and then to the receiver; It is the time it takes for the signal to arrive at the base station antenna, be processed by the base station, and then be transmitted from the base station antenna; represents other measurement errors.

The difference operation is performed on the signal propagation time from the same satellite and forwarded to the receiver by the same base station but measured at different times, and we can get

Among them, the receiver clock error δt _c will be eliminated; Generally speaking, the interval between t ₀ and t ₁ is very small (less than or equal to 1 second), therefore, and can be considered zero. The receiver can obtain the satellite coordinates after decoding the satellite data. In addition, the receiver can obtain the coordinate information of the base station through signaling when accessing the base station. Therefore, It can be obtained through satellite and base station coordinate calculation.

The receiver performs a differential operation on the propagation time measured at two consecutive moments (t ₀ and t ₁ ) of the signals forwarded by different base stations, namely

Let can be expressed as in i=0,1, that is, the coordinates of the user at time t _i ; is the coordinates of base station b _j (j=1,2,3), and Represents the distance from base station b _j to user receiver at time t _i . In this way, formula (3) can be further expressed as:

Formula (4) can be further organized as:

In this way, if the position of the user receiver at time _t0 is known, the position of the receiver at time _t1 can be calculated according to formula (5). Note that the calculated user location is

Using positioning method one, the receiver can calculate its position at the next time based on its position at the previous time. When the user enters the blind area of the satellite signal from the effective area of the satellite signal, the first position in the blind area can be calculated according to the precise position obtained at the previous moment. When the user is moving in the blind zone, the next moment location can be continuously calculated based on the previous moment location. But the problem is that if there is an error in the position calculation at the previous moment, it will cause an error in the current position calculation, and then the cumulative error will become larger and larger. Therefore, in order to reduce the cumulative error, the error will be corrected by the second method.

The second positioning method:

When the user receiver receives the retransmission signal from the base station, it can use the signal to measure the time elapsed from the satellite to the user signal through the base station time measured at instant t _k Will be as shown in formula (1). Signals from the same satellite are forwarded through different base stations, and the time required for them to reach the user's receiver will be different. Suppose the same satellite (s ₁ ) signal is forwarded by four base stations b _j (j=1,2,3,4), then

Let is the measured value, and is the time required for the signal to propagate from satellite s ₁ to base station b _j , which can be calculated from the coordinates of satellite s ₁ and base station b _j . so, Can be expressed as follows:

Because the base stations b _j (j=1, 2, 3, 4) are generally relatively close to each other (the receiver can receive the forwarded signals from these four base stations at the same time), so can be considered equal. In addition, the satellite signal forwarding processing time of each base station Equality is also assumed in this method. In this way, ignoring the difference in measurement error, according to formula (8), it can be further obtained:

Let in is the coordinates of the user receiver at time t _k ; is the coordinates of base station b _j . Thus, formula (9) can be written as:

According to formula (10), the user position coordinates can be calculated and obtained The closed-form solution of , remember the calculated user position as

For the above two positioning methods, for the first method, the main positioning error is because the positioning error at each moment will be accumulated in the positioning result at each subsequent moment; for the second method, the main positioning error comes from the different signal processing time of each base station. The main errors of the positioning results of these two methods come from different factors. If the two positioning results are combined to determine the receiver coordinates, the influence of each factor on the positioning error can be weakened, and the positioning accuracy can be improved. Therefore, the positioning results of the two methods can be used as observation values to filter the results with the Kalman filter to determine the final positioning result.

Claims (1)

1. A method for positioning a satellite signal blind area by combining a mobile cellular network and a satellite navigation system comprises the following steps:

the method comprises the following steps: positioning by two positioning methods

The first positioning method comprises the following steps:

firstly, eliminating the error of signal forwarding processing time; is recorded at time t_kSignals measured by the receiver from satellites s_iVia base station b_jThe time elapsed for forwarding to the receiver isThen

Wherein,is the signal from a satellite s_iTo base station b_jThe time of (d);is a signal from the base station b_jTime to receiver; δ t_cIs the receiver clock error;is the signal from a satellite s_iTo base station b_jPropagation errors experienced by the receiver;the time that the signal is transmitted from the base station antenna after the signal reaches the base station antenna and is processed by the base station;represents other measurement errors;

the differential operation of the propagation times of the signals coming from the same satellite and forwarded to the receiver via the same base station, but measured at different times, results in:

wherein the receiver clock difference deltat_cWill be eliminated;

t₀and t₁The interval between the two is less than or equal to 1 second,andconsidered to be zero; the receiver decodes the satellite data to obtain satellite coordinates; the receiver obtains the coordinate information of the base station through signaling when accessing the base station,calculating and obtaining coordinates of a satellite and a base station;

the receiver respectively transmits signals to different base stations at two successive time instants t₀And t₁The measured propagation times being differentially operated, i.e.

Let Is shown asWhereini is 0,1, i.e. at time t_iCoordinates of the user;is a base station b_jWherein j is 1,2,3, andis represented at time t_iSlave base station b_jDistance to the user receiver; equation (3) is further expressed as:

equation (4) is further organized as:

if the subscriber receiver is at time t₀When the position of the receiver is known, the receiver is calculated according to the formula (5) at the time t₁The position of the time; the calculated user position is

The second positioning method comprises the following steps:

when the subscriber receiver receives the retransmitted signal from the base station, it uses the signal to measure the time it takes for the signal to be retransmitted from the satellite to the subscriber via the base stationAt time t_kMeasured timeWill be as shown in equation (1); the signals from the same satellite are forwarded through different base stations, and the time required for them to reach the user receiver will be different; assuming the same satellite s₁Signals are transmitted through four base stations b_jForwarding, where j is 1,2,3,4, then

Letj＝1,2,3,4；To measure, andis the signal from a satellite s₁To base station b_jTime required for propagation through satellite s₁And base station b_jCalculating the coordinates of the target;where j is 1,2,3, 4:

base station b_jThe distance is close, and the receiver simultaneously receives the retransmission signals from the four base stations, wherein j is 1,2,3 and 4;considered equal, where j is 1,2,3, 4; satellite signal retransmission processing time of each base stationEqual is assumed, where j is 1,2,3, 4; according to equation (8), further obtained is:

letWhereinAt a time t_kThe coordinates of the user receiver, j ═ 1,2, 3;is a base station b_jThe coordinates of (a); equation (9) is written as:

according to the formula (10), calculating and obtaining the position coordinates of the userThe calculated user position is recorded as

The second step is that: fusing two positioning results by using Kalman filter

The state transition matrix of the Kalman filter is a unit matrix, and the state transition model is as follows:

whereinRepresents the coordinates of the user's position at the k-th measurement instant, andis a process noise vector;

the positioning results measured by the first positioning method and the second positioning method are combined to be used as an observed value of the Kalman filter, namely

WhereinWhile

The relationship matrix h (k) between the observed values and the state values is defined as:

anddefining the array as a unit array; the corresponding measurement noise matrix is defined as:

wherein v is₁(k) And v₂(k) Are respectively corresponding measured valuesAndthe measurement error and noise of (2); the observation model is

And filtering by using a standard Kalman filtering algorithm to obtain the position coordinates of the end user.