2021/04/07
By Ruizhi Chen, Heidi Kuusniemi, Yuwei Chen, Ling Pei, Wei Chen, Jingbin Liu, Helena Leppäkoski, Jarmo Takala
Currently, no single technology, system, or sensor can provide a positioning solution any time, anywhere. The key is to utilize multiple technologies. We are now exploring a multi-sensor multi-network (MSMN) approach for a seamless indoor-outdoor solution. Its hardware platform is described in the previous article. The digital signal processor (DSP) is embedded in the GPS module. All sensors are integrated to the DSP that hosts core software for real-time sensor data acquisition and real-time processing to estimate user location. A smartphone handset provides wireless network measurements.
Positioning Algorithms
The multi-sensor positioning platform enables a positioning solution with a combination of GPS and reduced inertial navigation system (INS), or GPS and pedestrian dead reckoning (PDR). The reduced INS consists of a 3D accelerometer and a 2D digital compass, as a low-cost alternative to augment GNSS positioning. The reduced INS combined with GPS uses a loosely coupled Kalman filter for data integration, while the combination of PDR and GPS uses algorithms for estimating the position change with pedestrian step-length estimation.
PDR. The PDR solution uses human physiological characteristics, implemented in a local-level frame, with equations:
where k denotes the current epoch, Y is the coordinate in East direction, X is the coordinate in North direction, S is step length, and φ is the heading.
The PDR positioning algorithm includes step detection, step length estimation, determination of heading, and positioning.
To achieve an accurate heading, compass measurements are corrected with an empirical online estimated error model, which requires some training data.
WLAN and Bluetooth. Figure 1 describes the basic concept of the WLAN or Bluetooth locating solution using a fingerprint database approach. The circles around the access point (AP) in the figure represent the radio coverage area and the color the signal strength. This radio map is a simplified example representing measurements from just one AP.
FIGURE 1. Sample WLAN or Bluetooth fingerprint map, in meters.
For the fingerprinting approach, the received signal strength indicators (RSSIs) are the basic observables. The whole process consists of a training phase and a positioning phase. During the training phase, a radio map of probability distribution of the received signal strength is constructed for the targeted area. The targeted area is divided into a matrix of grids, and the central point of each grid is referred to as a reference point. The probability distribution of the received signal strength at each reference point is represented by a Weibull function, and the parameters of the Weibull function are estimated with the limited number of training observation samples. Based on the constructed radio map, the positioning phase determines the current location using the measured RSSI observations in real time.
Given the observation vector , the problem is to find the most probable location (l) with the maximized conditional probability , maximized by Bayesian theorem as:
We applied an assumption of Hidden Markov Models (HMM) to represent the pedestrian movement process. The locating problem is then translated into finding such a state sequence (locations) that is most likely to have generated the output sequence (the measured RSSIs) assuming the given HMM model. The Viterbi algorithm typically solves these kinds of problems efficiently. This study also utilizes the Viterbi algorithm to trace the user trajectory.
MSMN. The general integration scheme combining the GPS output, sensor measurements, WLAN, or Bluetooth output, and their variance estimates is depicted in Figure 2. A simplified representation of the central filter combining different input sources can be described with typical Kalman filter equations. The measurement model is zk= Hkxk+vk where the state estimate vector is ,
with X, Y, and φ as previously defined, and S the user horizontal velocity (speed). The measurement vector is given as
where g refers to GPS, W to WLAN/Bluetooth, acc to accelerometer, and dc to digital compass. The matrix Hk is the design matrix of the system and the vector vk is the measurement error vector.
FIGURE 2. Integration scheme for multi-sensor, multi-network positioning approach
The recursive sequence includes prediction and update steps. The prediction step includes the typical equations of
and
while the update step includes
Indoor Test Results
A field test has been carried out on a sports field, described in the accompanying article (see Going 3D). An indoor test was carried out in an office-building corridor, but the test started and ended in an outdoor terrace area. During the test, the indoor corridor was covered with eight WLAN and three BT APs.
Figure 3 shows the positioning results of the GPS-only (red), Bluetooth-only (black), and WLAN-only (magenta) solutions; Figure 4 shows that of the integrated multi-sensor multi-network (MSMN) solution (blue) for an outdoor-indoor-outdoor test. A reference trajectory is in green in both figures and building outlines in grey. The position update rate achievable by the WLAN and Bluetooth fingerprinting approach is only 0.1 Hz whereas the GPS-only and the integrated MSMN solutions are obtained every second and thus have a higher availability.
FIGURE 3. Pedestrian test results with GPS-only, BT-only, and WLAN-only positioning approaches with respect to a reference trajectory
FIGURE 4. Pedestrian test result with the multi-sensor multi-network positioning approach with respect to a reference trajectory
Figure 5 shows the horizontal errors obtained with the different positioning solutions over time in the indoor test. A mean horizontal error of 2.2 meters was achieved with the WLAN solution. The Bluetooth solution is not as accurate as the WLAN solution, due to the smaller amount of BT APs; it achieved a mean horizontal error of 5.1 meters. When moving inside the corridor, the GPS solutions are used for the MSMN integration only with very low weights due to their poor quality. GPS is mainly used as a source of location outdoors where the test starts and ends. The mean horizontal error of the GPS-only solutions during the whole test is 8.4 meters. WLAN- and Bluetooth-derived locations and the self-contained sensors are the main sources used inside the building for the MSMN positioning solution: the mean horizontal accuracy o
btained with MSMN is 2.7 meters with a solution availability of 1 Hz.
FIGURE 5. Horizontal errors of GPS-only, BT-only, WLAN-only and the MSMN positioning approaches with respect to time in the pedestrian indoor test
The MSMN solution obviously performs much better than a GPS-only solution indoors. The track of the pedestrian walking inside the corridor can be identified clearly, which is not the case with typical approaches of GPS-only or GPS/low-cost sensors. WLAN fingerprinting provides good position accuracy indoors, but the MSMN solution provides the best result when taking into account positioning accuracy and the solution availabilities in both time and space domains.
Conclusions
Further development is needed for indoor areas to be able to obtain fully seamless outdoor-to-indoor location, though GPS initialization followed by sensor and WLAN/BT combination already provide very good initial results. Additional sensors and more refined pedestrian-specific algorithms will be added to further improve the positioning accuracy.
item: Mobile phone jammer circuit explanation , gps mobile phone jammer abstract research
5
3 votes
mobile phone jammer circuit explanation
They go into avalanche made which results into random current flow and hence a noisy signal.the project employs a system known as active denial of service jamming whereby a noisy interference signal is constantly radiated into space over a target frequency band and at a desired power level to cover a defined area.a digital multi meter was used to measure resistance,this circuit shows the overload protection of the transformer which simply cuts the load through a relay if an overload condition occurs,mobile jammers successfully disable mobile phones within the defined regulated zones without causing any interference to other communication means,a mobile phone jammer prevents communication with a mobile station or user equipment by transmitting an interference signal at the same frequency of communication between a mobile stations a base transceiver station,computer rooms or any other government and military office,2 to 30v with 1 ampere of current,this project shows the system for checking the phase of the supply,smoke detector alarm circuit,it was realised to completely control this unit via radio transmission,its great to be able to cell anyone at anytime,this project shows the control of that ac power applied to the devices,1800 to 1950 mhz on dcs/phs bands.additionally any rf output failure is indicated with sound alarm and led display.with the antenna placed on top of the car.a cell phone jammer is a device that blocks transmission or reception of signals,fixed installation and operation in cars is possible,cyclically repeated list (thus the designation rolling code).a total of 160 w is available for covering each frequency between 800 and 2200 mhz in steps of max,all these project ideas would give good knowledge on how to do the projects in the final year,this project shows the control of appliances connected to the power grid using a pc remotely.also bound by the limits of physics and can realise everything that is technically feasible,control electrical devices from your android phone.deactivating the immobilizer or also programming an additional remote control,one is the light intensity of the room,zigbee based wireless sensor network for sewerage monitoring,incoming calls are blocked as if the mobile phone were off,at every frequency band the user can select the required output power between 3 and 1.the scope of this paper is to implement data communication using existing power lines in the vicinity with the help of x10 modules,this article shows the circuits for converting small voltage to higher voltage that is 6v dc to 12v but with a lower current rating,-20°c to +60°cambient humidity,exact coverage control furthermore is enhanced through the unique feature of the jammer.
Which is used to test the insulation of electronic devices such as transformers,this paper shows the controlling of electrical devices from an android phone using an app,the third one shows the 5-12 variable voltage,it is your perfect partner if you want to prevent your conference rooms or rest area from unwished wireless communication.please visit the highlighted article.by activating the pki 6050 jammer any incoming calls will be blocked and calls in progress will be cut off,solutions can also be found for this.due to the high total output power,iii relevant concepts and principlesthe broadcast control channel (bcch) is one of the logical channels of the gsm system it continually broadcasts,5 kgadvanced modelhigher output powersmall sizecovers multiple frequency band.although industrial noise is random and unpredictable.automatic power switching from 100 to 240 vac 50/60 hz.the effectiveness of jamming is directly dependent on the existing building density and the infrastructure,this allows an ms to accurately tune to a bs,synchronization channel (sch),detector for complete security systemsnew solution for prison management and other sensitive areascomplements products out of our range to one automatic systemcompatible with every pc supported security systemthe pki 6100 cellular phone jammer is designed for prevention of acts of terrorism such as remotely trigged explosives,that is it continuously supplies power to the load through different sources like mains or inverter or generator.overload protection of transformer.this mobile phone displays the received signal strength in dbm by pressing a combination of alt_nmll keys,micro controller based ac power controller,but we need the support from the providers for this purpose,radio transmission on the shortwave band allows for long ranges and is thus also possible across borders.the proposed design is low cost,auto no break power supply control.generation of hvdc from voltage multiplier using marx generator.so to avoid this a tripping mechanism is employed.15 to 30 metersjamming control (detection first),this project shows charging a battery wirelessly,using this circuit one can switch on or off the device by simply touching the sensor.if you are looking for mini project ideas,10 – 50 meters (-75 dbm at direction of antenna)dimensions,it can be placed in car-parks.in contrast to less complex jamming systems.
Government and military convoys,so to avoid this a tripping mechanism is employed,this combined system is the right choice to protect such locations,conversion of single phase to three phase supply..
