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2017 IEEE International Conference on Telecommunications and Photonics (ICTP) 26-28 December, 2017, Dhaka, Bangladesh
Designing and Performance Evaluation of GSM/GPS Based Helicopter Tracking Device Md Imdadul Hoque,1,* Abdullah Al Amin,1 Md Jumshadur Rahaman,1 and Mohammad Hossam-E-Haider1 Electrical Electronic & Communication Engineering Department Military Institute of Science and Technology, Dhaka, Bangladesh *
[email protected]
1
Abstract— Low flying aircrafts are always tough to track due to the radar horizon limitation. But an aircraft is always to be tracked for the safety purpose. However, there are means to augment the radar detection like aircraft to ground data link or satellite phone.The combination of Global Positioning System (GPS) and Global System for Mobile Communications (GSM) can also perform the job satisfactorily. This work proposes the design for GPS/GSM based helicopter tracking device and evaluates the performance. In this work, two GSM networks were utilized to track low flying aircrafts in different routes. The device design is proposed basing on the experimental results of tracking. Possible future modifications of the device are also suggested to achieve more accurate and precise results in future experiments. Index Terms—GPS, GSM, Helicopter, SMS, Tracker.
I.
INTRODUCTION
In aircraft detection systems, the radar horizon is the distance at which radar beam rises much above the earth’s surface to make the low-level detection impossible[1]. The presence of clutter zone also restricts the radar beam. Clutter zone can be defined as the zone where radar energy is in the lowest altitude of the troposphere. These make the tracking of low flying aircrafts troublesome in some cases. But for security purpose, the positioning information of these aircrafts is very important[2]. Though Radio Detection and Ranging (RADAR) is an excellent tool for tracking, still the radar shadow and clutter zone needs to be covered up with any alternative communication mean.
communication system may satisfactorily cover up the zone that is blank for a radar and augment the communication throughout. GSM is the most common and widely used communication technology which is readily available at most of the parts around the globe[5]. It allows to send General packet radio service (GPRS) at a cheap rate. This provision can be utilized to transmit the positioning data which can be obtained by GPS. GSM primarily works on line of sight (LOS) principle and designed for surface communication. However, the lower altitudes can be covered by the GSM. This can successfully cover the radar shadow and augment other means of communication. In Spain, A study by Juan showed that, signal transmitted by GSM upwards are traceable by GSM devices up to the height of approximately 3000 meters[6]. Thus, it was confirmed that GSM works at low altitude and can be used for communicating with helicopters. It is easier for GSM network to cover the whole area of Bangladesh as it is the most densely populated country of the world. At present four separate GSM networks are operating in this country. All the networks have widespread network coverage; though may not be the whole country for all. The strengths of these networks are also not similar. Again, the network strength differs from place to place. Even the strongest network at one place may show poor network strength in some other place.
Helicopters are low flying aircrafts. Most helicopters do not have pressurized cabins. So they normally fly in low altitude, generally around 1000 feet. If a helicopter is flying at an altitude of 1000 feet, Radar can detect it up to maximum 75 km of distance. This happens due to the earth’s curvature[3]. Thus, obtaining the real-time position information of the helicopter is troublesome which increases flight safety hazards.
Bangladesh is a land of geo-diversity. Though mostly plain, Bangladesh has a widespread hilly region as well. Obviously, the hilly region causes the radar shadows and radar clutters in some of the areas. Thus, those areas remain untraceable by the radar coverage. But GSM can successfully cover the undulating lands as well.
Presence of the radar shadow and clutter zone allows the helicopters to take Nap-of-the-Earth (NOE). NOE is the very low altitude flying, usually by the military aircrafts to avoid the radar detection. However, it may be useful for aircrafts to avoid the enemy radar detection. But it is of obvious importance to remain in constant communication with own detection system. Secondary Surveillance Radar (SSR) is a means for covering the communication missing zone. But this is not also free of limitation with height. GPS is a trusted and widely accepted tool for obtaining position information[4]. Combination of GSM and GPS
Different technological terms are described here which will help to explain the working procedure of this project.
978-1-5386-3374-8/17/$31.00 ©2017 IEEE
II.
RELATED TECHNOLOGIES
A. GPS Technology The Global Positioning System (GPS) is a network of about 30 satellites. Those keep on orbiting the Earth at an altitude of 20,000 km. The purpose of the development of GPS was military navigation and implemented by the United States (US) government. At present, GPS devices are so available that almost every single person is in the possession
78 of GPS devices, be it a mobile phone or handheld GPS unit. These devices can receive the radio signals which are broadcasted by the satellites. These 30 satellites are so positioned that, any point of the planet is covered by at least four GPS satellites at any time. Those satellites individually transmit the data informing the positional data. Once any GPS receiver has information on the distance from at least three satellites, it can pinpoint the location. This process is known as trilateration. For a moving object, the time-based position, altitude, speed and direction can be extracted from the GPS satellite data.
C. RADAR Horizon The radar horizon is the distance at which radar beam rises much above the earth’s surface to make the low-level detection impossible. The presence of clutter zone also restricts the radar beam. Clutter zone can be defined as the zone where radar energy is in the lowest altitude of the troposphere.
Fig. 3 RADAR horizon.
D. Nap-of-the-Earth NOE is the provision of very low altitude flying to avoid being detected by enemy, particularly at a high-threat environment. During NOE flight, the aircrafts follow geographical features to keep themselves in radar shadow and thereby avoiding being detected. Fig. 4 shows a low flying aircraft (helicopter) following NOE route.
Fig. 1 GPS trilateration technique.
B. GSM Technology In the year of 1970 at Bell Laboratories, the idea of GSM was developed. It is the most widely used mobile communication system around the globe. GSM can operate at 850MHz, 900MHz, 1800MHz and 1900MHz frequency bands.GSM system was developed using time division multiple access (TDMA) technique as a digital system for the purpose of the communication. Data rates from 64kbps to 120Mbps can be carried by the GSM technology. A typical GSM architecture is shown in Fig. 2.
Fig. 4 NOE.
E. Google Maps ‘Google Maps’ is a service of technology giant Google. It is basically a web mapping service. It is very much useful to plot the positional data on a google map for the understanding at user end. Just plotting the position on google maps offers much better assimilation than merely mentioning the data as a list. A flight route of an aircraft plotted on google maps is shown here at Fig. 5.
Fig. 2 GSM architecture.
79 D. SIM800 GSM Module Simcom SIM800 is a quad-band GSM module is designed as a data communication equipment. It supports quad-band 850/900/1800/1900 Mhz. It can transmit voice, data and SMS with low power consumption. It provides a full modem serial port which is used for data transmission and sending command. The modem is controlled via AT commands. It operates within 3.4 volts to 4.4volts and 40°C to 85°C. The module was configured in GPRS mode for sending data to the remote server.
Fig. 5 Google maps.
III. METHODOLOGY Two devices were designed for evaluating the performance of helicopter path profile tracking, based on GSM network. The devices were developed using commercially available hardware comprising GPS receiver, GSM modem, microcontroller unit (MCU), micro Secure Digital (SD) card and power source. The main aim of this work is to develop an affordable and reliable tracking system for helicopter. A. Architechture of Modules To analyse the performance a device was developed and put into real-time experiment. The architecture of module-1 is shown in Fig.6. Here an algorithm was developed for transmission of data based on better network signal. The MCU determines the signal quality among the GSM networks and transmit data through the better one. The result obtained through the first module was not satisfactory. There after the module was redesigned using two MCU and two GSM modules keeping one GPS module. The block diagram is shown in Fig .7.
E. Operating Principle of Module-1 The module-1 was designed with one GPS module, two GSM module and one MCU. The GPS receives positional data from satellite and MCU extract the required data. Then MCU compares the signal strengths among two mobile operators and transmit to the server using best available network. After receiving data on the server side, data validation is conducted and stored in database. A web based application named (ONNESHA) has been developed on the server which projects the real-time location and related information of the device like speed, altitude, direction and time on digital map. The block diagram of module-1 is shown in Fig.6. Total five real-time performance tests were conducted by the module-1. Satellite GPS MCU GSM-1
GSM-2 BTS
B. Atmel Xmega Microcontroller The Atmel Xmega Microcontroller(AXM) is used with the GPS/GPRS/GSM Module for data management from the GPS and transmission of processed data to the remote server. This microcontroller having 100 pins among those 78 are digital Input/Output (IO) pins. The AXM has 128KB program memory. It can be connected to computer through USB cable. The boot loader occupies only 0.5 KB. It contains 8 KB of SRAM and 4 KB of EEPROM.
Fig.6 Block diagram of module-1.
C. U-Blox 6 GPS Module The NEO-6 GPS is a stand-alone GPS receiver featuring high performance u-blox 6 positioning engine. The 50channel u-blox 6 positioning engine claims a Time-To-FirstFix (TTFF) of under 1 second. The devoted acquisition engine, with 2 million correlators, is capable of massive parallel time/frequency space hunts, allowing it to find satellites instantaneously. Compact design and technology overpowers jamming sources and mitigates multipath effects, giving NEO-6 GPS receivers brilliant navigation performance even in the most hostile environments.
F. Operating Principle of Module-2 The operating principle is almost same like module-1 except algorithm and number of MCU. The operating block diagram is shown in Fig.7. The main difference between module-2 from module-1 is the use of two MCU. Each MCU extracts data from the same GPS module but transmit data to the server following separate GSM network individually. The algorithm is also different from module-1. A provision of SD card was kept but intentionally it was disabled to analyze the unsuccessful transmission without storing to memory device. So far two tests were conducted
Server
80 through Bell-212 helicopter and in future, more tests will be conducted in different routes covering more area.
Tx vs Rx Chart
Satellite
800
GPS
600
585
546 522
525
400
MCU-1
MCU-2
GSM-1
GSM-2
BTS-1
BTS-2
200
95.60
89.74
0 First Flight Tx
Second Flight Rx
Rx %
Fig. 9 Transmitted vs received data.
Server
Fig. 7 Block diagram of module-2.
IV.
EXPERIMENTAL RESULTS
A. Result from Device-1 The helicopter flew at 200kph and maintained average height of 1000 feet. Total flight time was about 3 hour 30 minutes. After analysing the data received from the device it was found that, only 20-25% data could be sent. The test was conducted using two mobile networks but every time with different network combination. One of the test results is plotted in Fig. 8.
Fig. 8 Helicopter routes tracked by device-1.
B. Result from Device-2 The helicopter flew twice at a speed of 200kph maintaining average height of 1000 feet. Total flight time was 2hr 25min covering distance of 160km per flight. This device could track approximately 92% of total path profile. The algorithm was programmed to send data after each 15 seconds. The maximum height travelled by the helicopter was 1250 feet from where the device could successfully transmit data except few places. The transmitted data was much better than the previous one. The transmitted data vs received data chart is shown in the Fig. 9and the tracked route is plotted on map shown in Fig. 10.
Fig. 10 Helicopter route, tracked by device-2.
V.
CONCLUSIONS
After conducting number of experiment through module1 it was observed that, the device was unable to transmit data despite availability of GSM network. While the MCU compares the strengths and tries to connect a BTS, the helicopter leaves behind the BTS due to its high speed. Since the signal strength is weak and changes vary rapidly, therefore single MCU can not operate two GSM modules effectively. Due to the high speed and low signal quality, the MCU fails to conduct handoff/re-registration of GSM module effectively. On the other side, module-2 with two MCU gave much better result compared to module-1. Each MCU of module-2 operates single GSM module separately. Transmission of 100% data instantly is not possible because of non-availability of network in some particular places. GSM network is not available across wide river and the places where habitation is absent. To get the complete flight path unsuccessful data need to be stored in SD card and transmitted to the server once the device reaches within the range of GSM network. In our future experiment, we will store unsent data in SD card and transmit as soon as the helicopter comes within the GSM network. The block diagram of data transmission and storing is shown in Fig.11. In this experiment two GSM networks were used. Use of even more GSM networks will help to achieve much better tracking result because a particular area not covered by one GSM network may be covered by another GSM network.
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GPS information acquisition
Extraction of position, altitude, speed, direction and time
Transmission of data through multiple GSM network to remote server
Transmission of data through multiple GSM network to remote server
No
Successful?
Store data in SD Card
Yes Logging of time, position, altitude, speed, direction, and GSM strength
Analysis and process of data for display
Fig.11 Block diagram of data transmission and storage procedure.
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