CN111025355B - Tower type indoor positioning system and method based on GPS signals - Google Patents

Abstract

The invention provides a tower-type indoor positioning system and method based on GPS signals, comprising: a GPS signal receiver, the antenna of which is a Cassegrain reflector antenna device; Amplification; the processing master unit performs comprehensive processing on the amplified signal, and interacts with the data of the auxiliary device of the pseudo-fixed base station; the auxiliary device of the pseudo-fixed base station includes a plurality of pseudo-reference stations uniformly arranged around the circumference of the processing master unit, and the pseudo-reference The site is connected to the location of the processing host unit through a connecting rod, and the connecting rod is a retractable rod; the second amplification unit is used to re-amplify the signal of the processed host unit and transmit it to the transmitter; the transmitter is used to The signal is diffused and distributed indoors without affecting the performance of the inherent equipment in the room. The present invention can improve the accuracy of indoor positioning with a unique positioning device, and reduce the impact on indoor devices.

Description

A tower-type indoor positioning system and method based on GPS signals

technical field

The invention relates to the field of GPS positioning, in particular to a tower-type indoor positioning system and method based on GPS signals.

Background technique

GPS is the abbreviation of Global Positioning System (Global Positioning System), which is mainly used in plane positioning and navigation, and consists of 24 GPS satellites with a global coverage rate of up to 98%. However, affected by factors such as weather, buildings, and noise, some uncontrollable deviations occur in the GPS signal during transmission, and its accuracy is also affected. Weak, the resulting deviation is also very large, and even the satellite signal cannot be received.

The traditional pseudolite positioning method is based on the differential GPS positioning method, which mainly includes a fixed monitoring station with a known position, which receives GPS signals in real time and determines the pseudo-range error, and provides this error as a "correction number" to the user, and then The user corrects the pseudo-range difference to the pseudo-range measured by the user through the smart device. In this way, with appropriate equipment, the positioning accuracy within a range of hundreds of kilometers near the monitoring station can be increased to about 5m. However, no matter how differential GPS improves navigation accuracy, reliability and integrity, it cannot overcome the defects caused by unsatisfactory satellite constellation geometry.

The current mainstream indoor positioning technologies mainly include Wi-Fi fingerprint technology, geomagnetic technology, Bluetooth technology, infrared technology, radio frequency identification technology and ultra-wideband technology, etc. These technologies often require the support of more hardware devices. Although some technologies have achieved indoor high-precision positioning, due to the complexity of the internal structures of different buildings, the installation of equipment is quite cumbersome, and the number of equipment is large, the workload of files is large, and maintenance is inconvenient, so it cannot be widely used. Applied to large-scale buildings.

Based on UWB ultra-wideband indoor positioning technology, its positioning accuracy can reach decimeter level, and ultra-wideband radio has strong penetrability, which can better penetrate the materials of building structures. But precisely because of this feature, this technology will have an impact on the performance of inherent indoor equipment, such as related treatment equipment in hospitals, and UWB radios may cause related equipment to fail.

Contents of the invention

An object of the present invention is to provide a tower-type indoor positioning system and method based on GPS signals, which can improve the accuracy of indoor positioning with a unique positioning device and reduce the impact on indoor devices.

In particular, the present invention provides a tower-type indoor positioning system based on GPS signals, including:

The GPS signal receiver is located outdoors, and the main body of the antenna is a Cassegrain reflector antenna device composed of a main reflector, a sub-reflector and a rear feed;

a first amplifying unit, configured to amplify the signal passing through the GPS signal receiver once;

The processing host unit is used to comprehensively process the amplified signal and interact with the data of the auxiliary device of the pseudo fixed-point base station;

Pseudo-fixed base station auxiliary device, which includes a plurality of pseudo-reference stations uniformly arranged around the circumference of the processing main unit, the pseudo-reference stations are connected to the location of the processing main unit through connecting rods, and the connecting rods can be telescopic rod;

The second amplifying unit is used to re-amplify the signal passed through the processing host unit and transmit it to the transmitter;

The transmitter is used to diffuse and distribute the signal indoors without affecting the performance of the inherent equipment in the room.

Preferably, three pseudo-reference sites are evenly distributed in the circumferential direction of the processing main unit, and the three pseudo-reference sites are located on the same plane as the processing main unit.

Preferably, the pseudo-reference station can rotate around the processing host unit to adjust the relative position.

Preferably, the processing host unit includes: a host, a receiving unit, a frequency hopping processing unit, a signal processing unit, an anti-jamming unit, a monitoring unit, and a display screen.

Preferably, the maximum telescopic length of the connecting rod is 5m.

According to another aspect of the present invention, a tower-type indoor positioning method based on GPS signals is also disclosed, including:

S1: The GPS signal receiver receives the signal through the Cassegrain reflector antenna device, amplifies the signal through the primary amplifier of the preamplifier, and obtains the low frequency signal through the receiver host;

S2: amplifying the signal passing through the GPS signal receiver once;

S3: The processing host unit comprehensively processes the amplified signal;

S4: Process the data interaction between the host unit and multiple pseudo-reference sites of the pseudo-fixed base station auxiliary device, form a pseudo-satellite correction system within the range, and generate new GPS signals;

S5: performing secondary amplification on the new GPS signal and transmitting it to the transmitter;

S6: Diffusion and distribution of signals in the room without affecting the performance of the inherent equipment in the room.

Preferably, the processing master unit in S3 utilizes multiple auxiliary functional units for comprehensive processing, including: a receiving unit, a frequency hopping processing unit, a signal processing unit, an anti-jamming unit, and a monitoring unit.

The tower positioning system of the present invention is combined with the GPS signal receiver and the pseudolite correction system, and the pseudolite correction system is composed of a plurality of pseudo-reference sites and a processing host unit. After processing, a new GPS signal suitable for indoors is formed through the pseudolite correction system, thereby improving the accuracy of indoor positioning.

Furthermore, the tower positioning system of the present invention is also provided with a transmitter, and the new GPS signal after measurement and correction is diffused and distributed indoors through the transmitter. Since the attenuation constant becomes larger and the penetration depth decreases as the signal wavelength decreases (i.e., higher frequency signals), the signal dispersion of the transmitter of the present invention can be achieved without affecting the indoor inherent device performance. .

Those skilled in the art will be more aware of the above and other objects, advantages and features of the present invention according to the following detailed description of specific embodiments of the present invention in conjunction with the accompanying drawings.

Description of drawings

Hereinafter, some specific embodiments of the present invention will be described in detail by way of illustration and not limitation with reference to the accompanying drawings. The same reference numerals in the drawings designate the same or similar parts or parts. Those skilled in the art will appreciate that the drawings are not necessarily drawn to scale. In the attached picture:

Fig. 1 is a simple system block diagram according to the tower type indoor positioning system and method of the present invention;

Fig. 2 is the front view of the external device structure of the tower type indoor positioning system according to the present invention;

3 is a top view of the external device structure of the tower-type indoor positioning system according to the present invention;

Fig. 4 is the antenna structural diagram of the Cassegrain reflector of the present invention;

Fig. 5 is the overall schematic diagram of the receiver host unit of the GPS signal receiver of the present invention;

Fig. 6 is the signal path schematic diagram of the receiver host unit of the GPS signal receiver of the present invention;

Fig. 7 is the frequency hopping spread spectrum output waveform in the processing host unit of the present invention.

The meanings of the symbols in the figure are as follows:

1-Cassegrain reflector antenna device; 101-secondary reflector; 102-main reflector; 103-feed source; 2-first amplifying unit; 3-processing host unit; 4-connecting rod; 5-pseudo-reference site; 6-second amplifying unit; 7-transmitter.

Detailed ways

The present invention is mainly aimed at: 1. The existing indoor positioning technology will affect the performance of indoor equipment while ensuring the accuracy of the diffusion process; 2. The complex structure inside the building often requires the installation of a large number of hardware devices to support the realization of related technologies, etc. Two questions. A system and implementation method for completing indoor precise positioning by relying on a single device are studied without affecting the inherent devices in the room.

As shown in Fig. 1, the present invention has designed a kind of tower type device that receives, demodulates, modulates, analyzes and processes, converts, amplifies, rectifies and spreads the GPS signal, mainly realizes through several big functions without affecting indoor Under the premise of inherent equipment, rely on a single device to complete the purpose of indoor precise positioning. The functions of these blocks are: GPS signal receiver, first amplifying unit 2 , processing host unit 3 , second amplifying unit 6 and transmitter 7 .

As shown in Figures 2, 3 and 4, the GPS signal receiver is located outdoors for receiving GPS signals. The GPS signal receiver includes an antenna, a host, and a power supply. Wherein, the main body of the antenna is a Cassegrain reflector antenna device 1 , which is mainly composed of a main reflector 102 , a sub-reflector 101 and a feed source 103 . The main reflector 102 is a parabolic cone, and the sub-reflector 101 is a hyperbolic cone. In this embodiment, the feed source 103 is a rear feed source, which can shorten the length of the feed line, reduce the noise brought by the transmission line, and convert the extremely weak electromagnetic wave energy of the GPS satellite signal into corresponding current. The preamplifier and rear feed are sealed together. The antenna is sealed with the preamplifier to ensure its normal operation and reduce signal loss. The host of the receiver has: a frequency converter, an intermediate frequency receiving amplifier, a signal channel, a memory, a microprocessor, and a display.

As shown in FIG. 5 , the outdoor GPS signal receiver efficiently receives and converts signals through the Cassegrain reflector antenna device 1 . According to the principle of the Cassegrain reflector antenna, the smaller the eccentricity, the greater the magnification, and usually the magnification M>3. After passing through the antenna and the preamplifier, the weak electromagnetic pen of the GPS is converted into a corresponding current, and then the signal current is amplified. Then, the frequency conversion, despreading, and demodulation of the amplified signal are performed by the receiver host to obtain the navigation message of the received signal. Among them, the frequency converter and intermediate frequency amplifier in the main body of the receiver make the receiver channel obtain a stable high gain, and make the radio frequency signal of the L frequency band into a low frequency signal.

As shown in the signal channel analysis diagram shown in Figure 6, the C/A code generator and the P code generator will be used to complete the despreading and demodulation processing of the low-frequency signal, and obtain multiple sets of navigation message D code pseudo code measurement data, carrier phase Measurement data. And calculate the time of GPS signal from the satellite to the receiving antenna in real time, and calculate the three-dimensional position, three-dimensional velocity and time of the monitoring station. Store all the above data in the memory of the GPS signal receiver. The data is output under the analysis and processing of the microprocessor, and the data processed by the microprocessor is displayed on the display screen, and the data observation and control are carried out through the display screen. Therefore, the GPS signal receiver can be used to amplify the frequency of the received signal, despread and modulate the signal, measure the bit code and carrier phase, and perform self-inspection, measurement, calculation and other processes in the microprocessor. Data observation and operation can also be performed through the display.

The first amplifying unit 2 amplifies the signal passing through the GPS signal receiver for subsequent processing.

The processing host unit 3 comprehensively processes the once-amplified signal, and exchanges data with the auxiliary device of the pseudo fixed-point base station. The processing host unit 3 and the auxiliary device of the pseudo-fixed base station together form a pseudolite correction system. The auxiliary device for pseudo-fixed base stations has a plurality of pseudo-reference stations 5 . The processing host unit 3 is the heart of the orthotic system. A plurality of pseudo-reference sites 5 are uniformly arranged around the circumference of the processing host unit 3. In this embodiment, there are three pseudo-reference stations 5, and the angle difference between them is 120°. The pseudo-reference site 5 is connected to the location of the processing host unit 3 through a connecting rod 4 . Because the connecting rod 4 is a telescopic rod. The linear distance between the pseudo-reference site 5 and the processing host unit 3 can be adjusted. The maximum telescopic length of a single connecting rod 4 is 5 meters. Moreover, the pseudo-reference station 5 can also rotate around the processing master unit 3 . Therefore, the pseudo-reference station 5 can capture signal sources at different points, receive different GPS signals in real time, determine the pseudo-range error, and send the information to the processing host unit 3 to complete the data interaction, thereby measuring and correcting the GPS signal .

Assuming that the propagation time is Ti and the ideal speed is the speed of light c, the data transmission distance Di can be expressed as: Di=c*Ti(i=1, 2, 3). In addition, the WCDMA algorithm is used to calculate the bit error rate and base station sensitivity. Among them, the radio frequency bandwidth is equal to the chip rate, that is, 3.84MHz. For a QPSK modulated signal with a rate of 12.2kbit/s, the specified bit error rate BER (0.1%) can be obtained when the Eb/No value is 5dB. Can be calculated to get:

KTBRF(dBm)＝10log(1.381×10-23W/Hz/K×290K×3.84MHz×1000mW/W)＝-108dBm

Gp(dB)＝BRF/Rb＝25dB

Then, base station sensitivity: S(dBm)=NF-108+5-25=NF-128dB

In addition, in order to achieve a dynamic range of 60dB, the FDMA-frequency offset technology is used to make the pseudolite signal deviate from the nominal value of 1575.42MHZ by about 10-20MHZ, which can isolate 25dB of the normal code.

The processing host unit 3 performs comprehensive processing on the signal, which is assisted by the host, receiving unit, frequency modulation processing unit, signal processing unit, anti-interference unit, monitoring unit, and display screen that make up the processing host unit. The processing master unit 3 comprehensively analyzes, processes, and monitors the data input from the GPS signal receiver and the data input from the pseudo fixed-point base station auxiliary device.

Since noise interference is generated during the above-mentioned transmission processing, an anti-interference unit is added in the processing process to improve its anti-interference performance. The anti-interference performance is expressed by the processing gain Gp as:

The size of the processing gain of the spread spectrum system determines the strength of the system's anti-interference ability. According to Shannon's theorem, when the information capacity is kept constant, the ratio of the system input to output signal-to-noise power ratio can be converted into the ratio of the system spreading bandwidth (B _RF ) to the information bandwidth (B _b ), or into a pseudocode The ratio of the rate (R _c ) to the information rate (R _b ). Expressed mathematically as:

Among them, R is the transmission rate of the signal, and B _RF is the radio frequency broadband of the signal. If there are no additional parameters, it can be estimated according to Gp (dB): 10lg [PN code length], and the anti-interference performance of the device can be improved through the above processing.

Figure 7 is the frequency hopping spread spectrum output waveform. For the frequency hopping processing unit, we use hybrid spread spectrum techniques, namely direct sequence spread spectrum, frequency hopping spread spectrum, time hopping spread spectrum and linear modulation. Among them, direct sequence spread spectrum technology and frequency hopping spread spectrum technology are mainly used. For the direct-sequence spread spectrum technology, the synchronous data signal may be a bit or a binary channel coding symbol, which is formed into chips by modulo 2 addition operation, and then phase-shifted and modulated. The received spread spectrum signal of a single user can be expressed as:

Among them, m(t) is a data sequence, and p(t) is a PN (pseudo-noise sequence) spreading sequence. For the frequency hopping spread spectrum technology, the carrier frequency is changed in discrete increments according to the graphics generated by a code sequence. After the digital information and the binary pseudocode sequence are subjected to modulo 2 addition operation, the output frequency of the RF carrier oscillator is controlled discretely. , so that the frequency of the transmitted signal jumps with the change of the pseudocode, as shown in Figure 7, in the process of transmission to the receiving unit, assuming that the receiving unit has reached synchronization, the received signal passes through a wideband filter, and then with the locally generated PN The sequence p(t) is multiplied, if p(t)=±1, there are:

p ^2(t) = 1

The despread signal is obtained by multiplication:

S ₁ t＝A _m (t)cos(2πf _c t+θ)

Since S ₁ (T) is a BPSK signal, the data sequence m(t) can be demodulated accordingly. The anti-jamming capability of the system is enhanced through spread spectrum, and the sensitivity formula of the spread spectrum system is as follows:

Spread spectrum system sensitivity formula 1:

Sin(dBm)＝NF(dB)+KTB(dBm)+Eb/No(dB)-Gp(dB)

Spread spectrum system sensitivity formula 2:

Sin(dBm)＝NF(dB)+KTB(dBm)+SNR(dB)--->SNR＝Sout/Nout(dB)

Among them, NF is the noise figure, K, T are the Boltzmann constant and Kelvin temperature (here = 290K), B is the spread spectrum bandwidth, Eb is the signal energy per bit, N0 is the noise power spectral density (note that Different) = F*KT, F is the noise figure, and Gp is the spread spectrum gain=B/R (R=user data baud rate), and it can be concluded that encoding and decoding effectively reduces Eb/N0, improves system sensitivity, and expands The coverage radius improves the anti-interference ability.

In the above information processing process, focus on analyzing the GPS precision factor, where the positional precision factor (PDOP) ranges from 0.5 to 99.9, which is the square root value of the sum of squared errors such as latitude, longitude and elevation, so there are:

HDOP ² +VDOP ² = PDOP ²

Among them, HDOP is the horizontal component precision factor, VDOP is the vertical component precision factor, and for the clock difference precision factor TDOP, the relationship between the geometric precision factor GDOP is:

PDOP ² + TDOP ² = GDOP ²

Solve the above coding and improve its sensitivity to improve the real sensitivity. The key point is the design of the first-stage LNA and input matching circuit. The key to LNA input matching is the lowest noise figure matching. The matching method is Gt gain circle, NF noise Circle, stable circle, find the appropriate GamaS, these are the matching steps, in addition, we add the consideration of sensitivity again, and divide the received signal power into several parts in refinement:

Paten: The signal power received by the antenna, Psignal: The output signal power of the antenna signal after matching, that is, the signal power before the LNA, Psig_reflect: The power reflected back from the LNA does not completely match, Psig_LNA: The signal power received by the LNA, they The relationship between is:

Psignal=Paten*aFactor (attenuation factor)=Psig_LNA+Psig_reflect

It can be obtained that the signal that can effectively decode the system is Psig_LNA, and the way to improve the sensitivity is: reduce the attenuation factor of the signal power from the antenna, and reduce the reflected power of the LNA input system.

Therefore, the processing host unit 3 performs data interaction with multiple pseudo-reference sites 5 of the pseudo-fixed base station auxiliary device to form a pseudolite correction system within the range and generate new GPS signals. Then, through the second amplification unit 6 , the new GPS signal is amplified twice and transmitted to the transmitter 7 . The transmitter 7 diffuses and distributes the signal indoors without affecting the performance of the inherent equipment in the room.

The signal is transmitted and diffused through the transmitter 7. During this process, it must be ensured that it does not affect the performance of the inherent equipment in the room. The Lambert-Beer law describes the signal penetration depth as:

称为透光率，等于T％，

称为吸光度，等于A，K为摩尔吸光系 数，它与吸收物质的性质及入射光的波长λ有关，c为吸光物质的浓度,单位为 mol/L，b为吸收层厚度。同时Lambert-Beer定律与信号衰减常数有关，通过 计算衰减常数找到α，可以发现其受信号波长λ的影响，因此，随着信号波长 的减小(即更高频的信号)，其衰减常数变得更大，并且穿透深度减小。利用此特性我们通过发射机进行GPS信号在室内的传输与扩散分布。in

Called the transmittance, equal to T%,

It is called absorbance, equal to A, K is the molar absorptivity coefficient, which is related to the nature of the absorbing substance and the wavelength λ of the incident light, c is the concentration of the absorbing substance in mol/L, and b is the thickness of the absorbing layer. At the same time, the Lambert-Beer law is related to the signal attenuation constant. By calculating the attenuation constant to find α, it can be found that it is affected by the signal wavelength λ. Therefore, as the signal wavelength decreases (ie, a higher frequency signal), its attenuation constant becomes becomes larger and the penetration depth decreases. Using this feature, we use the transmitter to carry out the transmission and diffusion distribution of GPS signals indoors.

In summary, due to the combination of the GPS signal receiver and the pseudolite correction system, the pseudolite correction system is composed of multiple pseudo-reference stations 5 and a processing host unit 3, therefore, the weak GPS signal can be processed by amplification, despreading, modulation, etc. Finally, through the pseudolite correction system, a new GPS signal suitable for indoors is formed, thereby improving the accuracy of indoor positioning. The measured and corrected new GPS signal is diffused and distributed indoors through the transmitter 7 . Since the attenuation constant becomes larger and the penetration depth decreases as the wavelength of the signal decreases (i.e., higher frequency signals), the signal dispersion of the transmitter 7 of the present invention can be achieved without affecting the inherent equipment in the room. performance.

So far, those skilled in the art should appreciate that, although a number of exemplary embodiments of the present invention have been shown and described in detail herein, without departing from the spirit and scope of the present invention, the disclosed embodiments of the present invention can still be used. Many other variations or modifications consistent with the principles of the invention are directly identified or derived from the content. Accordingly, the scope of the present invention should be understood and deemed to cover all such other variations or modifications.

Claims (7)

1. A tower-type indoor positioning system based on GPS signals, characterized in that, comprising: The GPS signal receiver is located outdoors, and the main body of the antenna is a Cassegrain reflector antenna device composed of a main reflector, a sub-reflector and a rear feedback source; a first amplifying unit, configured to amplify the signal passing through the GPS signal receiver once; The processing host unit is used to comprehensively process the amplified signal and perform data interaction with the auxiliary device of the pseudo fixed-point base station; Pseudo-fixed base station auxiliary device, which includes a plurality of pseudo-reference stations uniformly arranged around the circumference of the processing main unit, the pseudo-reference stations are connected to the location of the processing main unit through connecting rods, and the connecting rods can be telescopic rod; The second amplifying unit is used to re-amplify the signal passed through the processing host unit and transmit it to the transmitter; The transmitter is used to diffuse and distribute the signal indoors without affecting the performance of the inherent equipment in the room. 2. The tower-type indoor positioning system according to claim 1, wherein three pseudo-reference sites are evenly distributed in the circumferential direction of the processing host unit, and the three pseudo-reference sites are located on the same plane as the processing host unit . 3. The tower-type indoor positioning system according to claim 1 or 2, wherein the pseudo-reference station can rotate around the processing host unit to adjust the relative position. 4. The tower-type indoor positioning system according to claim 1, wherein the processing host unit comprises: a host, a receiving unit, a frequency hopping processing unit, a signal processing unit, an anti-jamming unit, a monitoring unit, and a display screen. 5. The tower-type indoor positioning system according to claim 1 or 2, wherein the maximum telescopic length of the connecting rod is 5m. 6. A tower-type indoor positioning method based on GPS signals, characterized in that, comprising: S1: The GPS signal receiver receives the signal through the Cassegrain reflector antenna device, amplifies the signal through the primary amplifier of the preamplifier, and obtains the low frequency signal through the receiver host; S2: amplifying the signal passing through the GPS signal receiver once; S3: The processing host unit comprehensively processes the amplified signal; S4: Process the data interaction between the host unit and multiple pseudo-reference sites of the pseudo-fixed base station auxiliary device, form a pseudo-satellite correction system within the range, and generate new GPS signals; S5: performing secondary amplification on the new GPS signal and transmitting it to the transmitter; S6: Diffusion and distribution of signals in the room without affecting the performance of the inherent equipment in the room. 7. The tower type indoor positioning method according to claim 6, characterized in that, the processing host unit in S3 utilizes a plurality of auxiliary function units to carry out comprehensive processing, including: receiving unit, frequency hopping processing unit, signal processing unit, anti- Interference unit, monitoring unit.

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