Automatic Vehicle Locator [Author Avinash Jha]

ACKNOWLEDGEMENT

We owe a great many thanks to a great many people who helped and supported me during

the making of this project report.

Our deepest thanks to Prof. Mehul C. Patel,(Guide of our project) for providing proper

guidance. He has taken pain to go through the project and make necessary suggestions as

and when needed.

We also express our thanks to Dr. Suprvava Patnaik, Head of the Electronics

Engineering Department, SVNIT Surat , for extending her support.

We would also thank other faculty members without whom this project would have been

a distant reality. We also extend our heartfelt thanks to my family and well wishers.

Avinash Kumar U08EC347

Mitendra Kumar U08EC350

Alok Kumar U08EC351

ABSTRACT

If navigational data of a remote object can be sent over the air, then very powerful

monitoring systems of immense utility can be designed. Our project work aims to achieve

this by bringing together technologies like GPS and GSM. These modules are interfaced

using high performance ARM9 application domain processor. The data sent by remote

object include current location in terms of coordinates, height, and speed each with

chosen time interval. SMS Service is used to send the data automatically to control centre.

The control center can be where.

The final system will consist of a remote object having U-Blox GPS modem, SAMSUNG

S3C2440 ARM920T running Embedded Linux and SIM300 GSM modem while the

monitoring station will be having GSM terminal. This system is of immense utitility in

many fields like surveying, spying, tracking etc.

i

Table of Contents

List of Figures iii List of Tables iv

1. Introduction 01

1.1 Motivation 01 1.2 Overview of Project 02 1.3 Implementation Scheme 03

2. ARM9 MCU 04 2.1 Registers 04 2.2 Processor Modes 05 2.3 ARM Instruction Set 06

3. Embedded Linux 10

3.1 Introduction 10 3.2 Generic architecture 10 3.3 System Start up 13 3.4 System Memory Layout 15 3.5 Configuring and Compiling The Bootloader 17 3.6 Configuring and Compiling The Kernel 18 3.7 Configuring and Compiling The Rootfile system 20 3.8 Hardware Description of ARM9 Board 21 3.9 ARM9 Board Module Detail 21

4. GSM Receiver 24

4.1 Introduction 27 4.2 GSM Modem 28 4.3 GSM Kit 32 4.4 Power Supply 32 4.5 Dual Serial Interface 34 4.6 Indicator 37 4.7 Antenna Interface 38

5. GPS System 40

5.1 Why GPS 40 5.2 Generating GPS Signal Transit Time 41 5.3 Determining The Position in 3-D 42 5.4 Description of The entire System 43

ii

5.5 The GPS navigation Message 49 5.6 Information Contained in The subframe 50 5.7 Calculating Position 51 5.8 GPS Receiver 55 5.9 Basic Design of GPS Module 58 5.10 NMEA Data Interface 59

6. Algorithm and Results 65 6.1Algorithm 66 6.2Results 66 6.3Application 71

7. Conclusion 73

List of References 74

List of Acronyms 76

iii

List of Figures

1. Fig. 1.1 The Remote Object 02

2. Fig. 1.2 The Monitoring Station 03

3. Fig. 2.1 CPSR 04

4. Fig. 2.2 Processor Modes and registers 05

5. Fig. 2.3 ARM Instruction Format 06

6. Fig. 3.1 Architecture of generic Linux system 11

7. Fig. 3.2 System start up scenario 13

8. Fig. 3.3 Physical and virtual memory map for Compaq iPAQ 17

9. Fig. 3.4 Configuring and compiling the kernel 19

10. Fig. 3.5 Configuring and compiling the rootfile system using ptxdist 21

11. Fig. 3.6 ARM9 board 22

12. Fig. 3.7 ARM9 block diagram 23

13. Fig. 3.8 Circuit diagram of system reset 24

14. Fig. 3.9 Block diagram of serial ports of UART 25

15. Fig. 3.10 Circuit diagram of LCD interface 26

16. Fig. 4.1 GSM modem 30

17. Fig .4.2 Block diagram of GSM modem 31

18. Fig. 4.3 VBAT input 33

19. Fig. 4.4 Interfacing of serial port 35

20. Fig. 4.5 SIM interface circuit 37

21. Fig. 5.1 GPS satellite orbit to earth on 6 orbit plane 41

22. Fig. 5.2 Four satellites are required to determine a position in 3-D 42

23. Fig. 5.3 GPS segments 43

24. Fig. 5.4 Simplified satellite block diagram 46

25. Fig 5.5 Data structure of GPS satellite 46

26. Fig. 5.6 Measuring signal transit time 48

27. Fig. 5.7 Structure of entire navigation message 51

iv

28. Fig. 5.8 Four satellite signal must be received 52

29. Fig. 5.9 3-D coordinate system 53

30. Fig. 5.10 Smart GPS receiver 55

31. Fig. 5.11 Simplified block diagram of GPS receiver 56

32. Fig. 5.12 Typical block diagram of GPS 57

33. Fig. 6.1 Algorithm 65

34. Fig. 6.2 Snapshots of Location A 66

35. Fig. 6.3 Snapshots of Location B 67

36. Fig. 6.4 Message received at GSM Terminal 68

37. Fig. 6.5 Messages received at GSM Terminal when connected to pc 69

38. Fig. 6.6 Raw NMEA Data on minicom 70

39. Fig. 6.7 AVL Application 71

40. Fig. 6.8 Applicatoin in Science and Research 72

v

List of Tables

1. Table 2.1 Vector Table 07

2. Table 2.2 ARM Instructions 08

3. Table 4.1 GSM Technical Specifications 22

4. Table 4.2 AT Commands 24

5. Table 4.3 Logic Level of Port pins 34

6. Table 4.4 Signal of SIM Interface 36

7. Table 4.5 Working State of Network Status indicator 38

8. Table 5.1 Carrier Link Budget Analysis 44

9. Table 5.2 Causes of Error 52

10. Table 5.3 NMEA Data 61

11. Table 5.4 GGA Data 62

12. Table 5.5 GLL Data 63

13. Table 5.6 GSA Data 64

1

Introduction Chapter-1

1.1 Motivation

With the advent of satellite navigation systems like GPS (Global Position System),

GLONASS and Galileo etc., it has become possible to track the position of any object

having such systems. Concept of localizing or determining position of an object has been

popular since ancient times. Earlier voyagers used magnetic compass for navigation

purposes. It gave information about the directions with certain accuracy but localizing the

position of object was still a distant reality. Now the navigations systems are used at

many places for example in cars, military, engineering surveys and the list goes on.

The advent use of navigation can be combined with modern day wireless communication

services to yield a very useful application. It can be used to send the position of an object

to a distant location. So it becomes possible to monitor the position of a remote object.

This opens a wide door of possibilities for new and exciting applications. Surveillance,

Vehicle Location Information, Location Based Services can be provided with

considerable ease.

The remote monitoring systems become all the more useful if we use brute computing

capabilities of monitoring stations to calculate various other parameters related to remote

object. For example it is possible to record the path taken by a remote object (call it path

tracing), or for calculating speed of the object over long period of time, or for sounding a

alarm when the object approaches restricted regions. Hence it depends on monitoring

stations what kind of services they want to implement.

So there can be innumerous applications for a tracking system, that the reason for

implement the AVL. Throughout the thesis the AVL system has been explained.

2

1.2 Overview of Project

The Automatic Vehicle Locating System can be broadly divided into two parts

The remote object

The monitoring station

The remote object is the object whose location is to be monitored. In this thesis

considered it to be a vehicle. The remote object should consist of some kind of navigation

system, which would help to localize the position of the object. Further it should also

contain some form of communication equipment, preferably wireless. And at last there

must be some kind of controller which co-ordinates the operation of the navigation

systems and communication equipment.

Fig. 1.1 The Remote Object

Similarly the monitoring station should be equipped with a communication equipment to

receive the location data from the remote object. Further the station must contain a

computing device which can calculate and interpret the location data and provide it to the

user in a comprehensive manner. For example if the user wants the output on map then

co-ordinates obtained or calculated must be represented on map. Also note that

monitoring station need not be 'fixed'. There is no reason to place such a restriction, after

all as long as communicating equipment of the remote object and the monitoring stations

are connected it doesn't matter where a monitoring station is located. This opens a new

possibility of a portable monitoring station.

Navigation

System

Controller Communication

Equipment

3

Fig. 1.2 The Monitoring Station

1.3 Implementation Scheme

Until now showing the blocks of AVL conceptually. But real physical implementation

requires far more complexity. How this functionality achieve that is shown conceptually

in the previous section.

We start with the remote object. To localize the position of the object we have decided to

use GPS (Global Positioning System). Further GPS provides many advantages over other

navigation systems [1].We have used a GPS modem with a RS-232 interface provided by

MikroElektronika™. Since wireless communication between the remote object and

monitoring station is desirable we need to ensure a robust and secure connection

mechanism. Hence GSM becomes an obvious candidate. So a GSM modem with RS-232

interface provided by SciTech has been employed in this project. Finally we need a high

performance microcontroller to perform the control operations. Since a we have to

complex tasks of handling GPS calculations and GSM modem control, ARM9 MCU

provide by SAMSUNG is used.

At the monitoring station, a GSM modem. The computing device for interpreting the

received data can be either a computer or another ARM9 MCU. It depends on whether we

want portable or fixed monitoring stations. Finally we have used LCD display to display

the final result in a comprehensive format.

Although there is possibility to use either SMS or GPRS to transfer the remote object

data, we have decided to implement the system initially using the SMS. This is mainly

because of bulk SMS service is available at a low cost. Now that we have shown the role

of various modules in our project, we will see a detailed description of each of the

modules.

Communication

Equipment Computing

Device

OUTPUT

4

ARM9 MCU Chapter-2

ARM also known as Advanced RISC Machine was setup in 1990 as a joint venture of

Apple Computer, VLSI Technology and Ascorn Computer. ARM develops the ARM

processor cores and debug systems. But the complete microcontroller includes a number

of other components like memory, peripherals, I/O subsystems other features. ARM

provides licenses to chip manufacturers like NXP, Atmel, Sharp, ST Microelectronics.

These silicon vendors design the complete SOC-MCU. In this chapter summarized

ARM9 MCU from a programmer's point of view only [2],[3].

2.1 Registers

ARM is a load and store architecture, so all data processing instructions can only work on

register file. There are 16 user registers: R0-R15. All of them are 32-bit registers. R0-

R12 are used as general purpose registers. R13 is Stack Pointer and R14 is link register.

Link registers are used to store return address during branching instructions. R15 is the

program counter. CPSR is the current program status register. Its bits are shown in the

"Figure 2.1".

Fig. 2.1 CPSR Current program status register [2]

N,Z,C,V are negative, zero, carry, overflow flags. They are updated only for certain type

of instructions. I and F bit have the capability to mask the interrupts and fast interrupts

respectively. If T bit is set then processor has entered Thumb mode and hence can only

5

executed 16-bit thumb instructions. Last 5 bits are used to indicate the current mode of

the processor [3].

2.2 Processor Modes

There 7 processor modes supported in ARM. These are System mode, User mode,

Supervisor mode, Interrupt mode, Fast interrupt mode, Abort mode and Undefined mode.

Except the user mode all other modes are privileged modes and hence can change CPSR.

Supervisor mode is generally employed for RTOS and user mode for application

programs. Rest of the modes are used for exception handling. Each mode is having its

own stack pointer (SP), SPSR, and link register (LR). In FIQ additionally R7-R12 are

banked.

Fig. 2.2 Processor Modes and registers [4]

When an exception occurs than a processor is forced to change mode and PC loaded with

vector table address as shown in "Figure 2.3".

6

Table 2.1 Vector Table [4]

EXCEPTION MODE ADDRESS

Reset Supervisor 0x00000000

Undefined instruction undefined 0x00000004

Software interrupt Supervisor 0x00000008

Prefetch about (instruction fetch

memory about )

Abort 0x0000000C

Data Abort(data access memory abort) Abort 0x000000010

IRQ (Interrupt) IRQ 0x00000018

FIQ (fast interrupt) 0x0000001C

Out of the given exceptions, Software interrupt is of special interest because it is used to

change the mode from user mode to supervisor mode and hence can be used to implement

RTOS services. Interrupt and Fast interrupt are used to handle asynchronous events like

peripheral interrupts [3].

2.3 ARM Instruction Sets

In ARM mode, all the instructions can be executed conditionally. Also CPSR flag is

optionally updated with instructions. This not only helps to reduce un-necessary

branching (which causes pipeline flush) but also helps to implement complex logic.

Fig. 2.3 ARM Instruction Format [4]

List of ARM Instructions are given categorically in "Table 2.1". For details of syntax

[2].

7

Table 2.2 ARM Instructions [5]

Instruction Type

Functions Instruction

Move

Move MOV

Move NOT MVN

Move SPSR to register MRS

Move CPSR to register MRS

Move register to SPSR MSR

Move register to CPSR MSR

Move immediate to SPSR flags MSR

Move immediate to CPSR flags MSR

Arithmetic

Add ADD

Add with carry ADC

Subtract SUB

Subtract with carry SBC

Subtract reverse subtract RSB

Subtract reverse subtract with carry RSC

Multiply MUL

Multiply accumulate MLA

Multiply unsigned long UMULL

Multiply unsigned accumulate long UMLAL

Multiply signed long SMULL

Multiply signed accumulate long SMLAL

Compare CMP

8

Compare negative CMN

Logical

Test TST

Test equivalence TEQ

AND AND

EOR EOR

ORR ORR

Bit clear BIC

Branch

Branch B

Branch with link BL

Branch and exchange instruction set BX

Load

Word LDR

Word with user-mode privilege LDR

Byte LDR

Byte with user-mode privilege LDR

Byte signed LDR

Halfword LDR

Halfword signed LDR

Multiple block data operations -

Increment before LDMIB

Increment after LDMIA

Decrement before LDMDB

Decrement after LDMDA

Stack operation full LDMFD(A)

9

Stack operation empty LDMED(A)

Store

Word STR

Word with user-mode privilege STRT

Byte STRB

Byte with user-mode privilege STRBT

Halfword STRH

Multiple block data operations -

Increment before STMIB

Increment after STMIA

Decrement before STMDB

Decrement after STMDA

Stack operation full STMFD(A)

Stack operation empty STMED(A)

Swap Word SWP

Byte SWPB

Software interrupt Interrupt SWI

10

EMBEDDED LINUX CHAPTER-3

3.1 INTRODUCTION

Linux is interchangeably used in reference to the Linux kernel, a Linux system, or a

Linux distribution. Strictly speaking, Linux refers to the kernel maintained by Linus

Torvalds and distributed under the same name through the main repository and various

mirror sites. This codebase includes only the kernel and no utilities whatsoever. The

kernel provides the core system facilities. It may not be the first software to run on the

system, as a bootloader may have preceded it, but once it is running, it is never swapped

out or removed from control until the system is shut down. In effect, it controls all

hardware and provides higher-level abstractions such as processes, sockets, and files to

the different software running on the system.

An embedded Linux system simply designates an embedded system based on the Linux

kernel and does not imply the use of any specific library or user tools with this kernel. An

embedded Linux distribution may include: a development framework for embedded linux

systems, various software applications tailored for usage in an embedded system, or both.

Development framework distributions include various development tools that facilitate

the development of embedded systems. This may include special source browsers, cross-

compilers, debuggers, project management software, boot image builders, and so on.

These distributions are meant to be installed on the development host. Tailored embedded

distributions provide a set of applications to be used within the target embedded system.

This might include special libraries, executables, and configuration files to be used on the

target. A method may also be provided to simplify the generation of root file systems for

the target system.

3.2 Generic Architecture of Embedded Linux Systems

Immediately above the hardware sits the kernel. The kernel is the core component of the

operating system. Its purpose is to manage the hardware in a coherent manner while

11

providing familiar high-level abstractions to user-level software. As with other Unix-like

kernels, Linux drives devices, manages I/O accesses, controls process scheduling,

enforces memory sharing, handles the distribution of signals, and tends to other

administrative tasks. It is expected that applications using the APIs provided by a kernel

will be portable among the various architectures supported by this kernel with little or no

changes. This is usually the case with Linux, as can be seen by the body of applications

uniformly available on all architectures supported by Linux.

Fig. 3.1 Architecture of a generic Linux system[19]

Within the kernel, two broad categories of layered services provide the functionality

required by applications. The low-level interfaces are specific to the hardware

configuration on which the kernel runs and provide for the direct control of hardware

resources using a hardware-independent API. That is, handling registers or memory pages

will be done differently on a PowerPC system and on an ARM system, but will be

accessible using a common API to higher-level components of the kernel, albeit with

some rare exceptions. Typically, low-level services will handle CPU-specific operations,

architecture specific memory operations, and basic interfaces to devices

Above the low-level services provided by the kernel, higher-level components provide the

abstractions common to all Unix systems, including processes, files, sockets, and signals.

Since the low-level APIs provided by the kernel are common among different

12

architectures, the code implementing the higher-level abstractions is almost constant

regardless of the underlying architecture. There are some rare exceptions, as stated above,

where the higher-level kernel code will include special cases or different functions for

certain architectures.

Between these two levels of abstraction, the kernel sometimes needs what could be called

interpretation components to understand and interact with structured data coming from or

going to certain devices. Filesystem types and networking protocols are prime examples

of sources of structured data the kernel needs to understand and interact with to provide

access to data going to and coming from these sources.

During its normal operation, the kernel requires at least one properly structured

filesystem, the root filesystem. It is from this filesystem that the kernel loads the first

application to run on the system. It also relies on this filesystem for future operations such

as module loading and providing each process with a working directory. The root

filesystem may either be stored and operated on from a real hardware storage device or

loaded into RAM during system startup and operated on from there. As we'll see later, the

former is becoming much more popular than the latter with the advent of facilities such as

the JFFS2 filesystem.

Services exported by the kernel are often unfit to be used directly by applications. Instead,

applications rely on libraries to provide familiar APIs and abstract services that interact

with the kernel on the application's behalf to obtain the desired functionality. The main

library used by most Linux applications is the GNU C library. For embedded Linux

systems, substitutes to this library can be used, as we'll see later, to compensate for the

GNU C library's main deficiency, its size. Other than the C library, libraries such as Qt,

XML, or MD5 provide various utility and functionality APIs serving all sorts of purposes.

Libraries are typically linked dynamically with applications. That is, they are not part of

the application's binary, but are rather loaded into the application's memory space during

application startup. This allows many applications to use the same instance of a library

instead of each having its own copy. The C library found on a the system's filesystem, for

instance, is loaded only once in the system RAM, and this same copy is shared among all

applications using this library. But note that in some situations in embedded systems,

13

static linking, whereby libraries are part of the application's binary, is preferred to

dynamic linking. When only part of a library is used by one or two applications, for

example, static linking will help avoid having to store the entire library on the embedded

system's storage device.

3.3 System Start-up

Three main software components participate in system startup: the bootloader, the kernel,

and the init process. The bootloader is the first software to run upon startup and is highly

dependent on the target's hardware. The bootloader will conduct low-level hardware

initialization and thereafter jump to the kernel's startup code.

Fig. 3.2 System Start-up Scenario[20]

Embedded Linux systems are as diverse as their non-Linux counterparts. Embedded

Linux systems are characterized, nevertheless, by the requirement to load a Linux kernel

and its designated root filesystem. How these are loaded and operated, largely depends on

the system's requirements and, sometimes, on the state of its development.

There are three different setups used to bootstrap an embedded Linux system: the solid

state storage media setup, the disk setup, and the network setup. Each setup has its own

typical configurations and uses.

14

When power is applied to the ARM9 board, Bootlaoder (U-Boot in our case) performs

some low level hardware initialization, which includes configuring a serial port. It then

prints a banner line. Next the CPU and core are displayed, followed by some

configuration data describing clocks and cache configuration. This is followed by a text

string describing the board.

When the initial hardware configuration is complete, U-Boot configures any hardware

subsystems as directed by its static configuration. Here we see I2C, DRAM, FLASH, L2

cache, PCI, and network subsystems being configured by U-Boot. Finally, U-Boot waits

for input from the console over the serial port, as indicated by the MINI2440# prompt.

Now U-Boot can load the kernel image into RAM from either persistent storage medium like

NAND, SD-CARD or even USB-Stick or network like Ethernet over tftp. After bootm command

can be given to U-Boot. This will pass on kernel parameters to kernel and give control to

kernel. This marks the end of the bootloader. This is an important concept. Unlike the

BIOS in a desktop PC, most embedded systems are architected in such a way that when

the Linux kernel takes control, the bootloader ceases to exist. The kernel claims any

memory and system resources that the bootloader previously used. The only way to pass

control back to the bootloader is to reboot the board.

When the Linux kernel begins execution, it spews out numerous status messages during

its rather comprehensive boot process. During this step Kernel loads the device drivers

and other daemons required for system managements. Shortly before issuing a login

prompt on the serial terminal, Linux mounts a rootfile system. The root file system

contains the application programs, system libraries, and utilities that make up a Linux

system. Note that Linux can mount a root file system from other devices. The most

common, of course, is to mount a partition from a hard drive as the root file system, as is

done on your Linux laptop or workstation. But in our resource limited system kernel

loads the filesystem from SD-Card. However note that even non persistent storage like

network file system (NFS) could be used. It is common during development phase but not

employed in final systems.

15

Until this point, the kernel itself was executing code, performing the numerous

initialization steps in a context known as kernel context. In this operational state, the

kernel owns all system memory and operates with full authority over all system resources.

The kernel has access to all physical memory and to all I/O subsystems. It executes code

in kernel virtual address space, using a stack created and owned by the kernel itself.

When the Linux kernel has completed its internal initialization and mounted its root file

system, the default behavior is to spawn an application program called init. When the

kernel starts init, it is said to be running in user space or user space context. In this

operational mode, the user space process has restricted access to the system and must use

kernel system calls to request kernel services such as device and file I/O. These user

space processes, or programs, operate in a virtual memory space picked at random6 and

managed by the kernel. The kernel, in cooperation with specialized memory management

hardware in the processor, performs virtual-to-physical address translation for the user

space process. The single biggest benefit of this architecture is that an 6 It’s. error in one

process can’t trash the memory space of another. This is a common pitfall in legacy

embedded OSs that can lead to bugs that are some of the most difficult to track down.

3.4 System memory layout

An embedded system designer has many options in the layout and use of Flash memory.

In the simplest of systems, in which resources are not overly constrained, raw binary data

(perhaps compressed) can be stored on the Flash device. When booted, a file system

image stored in Flash is read into a Linux ram disk block device, mounted as a file

system, and accessed only from RAM. This is often a good design choice when the data

in Flash rarely needs to be updated. Any data that does need to be updated is relatively

small compared to the size of the ramdisk. It is important to realize that any changes to

files in the ramdisk are lost upon reboot or power cycle. However we decided to go with

lesser popular but arguably better option. Bootloader is in first partition of NAND but

Kernel and filesystems is placed in SD-card’s first and second partitions respectively so

that they can be updated from laptops.

16

To best use the available resources, it is important to understand the system's memory

layout, and the differences between the physical address space and the kernel's virtual

address space. Most importantly, many hardware peripherals are accessible within the

system's physical address space, but have restricted access or are completely "invisible"

in the virtual address space.

The physical map is important, because it provides us with information on how to

configure the kernel and how to develop custom drivers. During the kernel's

configuration, for instance, we may need to specify the location of the flash devices in our

system. During development, we may also need to write a driver for a memory-mapped

peripheral. We will also need to provide our bootloader with information regarding the

components it has to load.

Upon startup, the bootloader reads the kernel from the root filesystem into the system's

RAM and jumps to the kernel's start routines. From there on, the rest of the system startup

is carried out by Linux. Once Linux is running, the programs use virtual addresses. In

contrast to the physical memory map, the layout of the virtual memory map is of

secondary importance for kernel configuration or device driver development. For device

driver development, for instance, it is sufficient to know that some information is located

in kernel space and some other information is located in user space, and that appropriate

functions must be used to properly exchange data between the two.

The virtual memory layout is mostly important to understand and debug applications.

The kernel occupies a quarter of the virtual address space starting from address

0xC0000000. This region is also known as "kernel space." The rest of the address space is

occupied by application-specific text, data, and library mappings. This is also known as

"user space." Whereas the kernel is always located above the 0xC0000000 mark for all

applications, applications' memory maps may differ even on the same system. An

example of the embedded linux system is shown in figure below.

17

Fig. 3.3 Physical and virtual memory maps for the Compaq iPAQ[19]

3.5 Configuring and Compiling the Bootloader

Though the bootloader runs for a very short time during the system's startup and is mainly

responsible for loading the kernel, it is a very important system component. Setting up a

bootloader is, to some extent, a task common to all Linux systems. It is a special task,

nevertheless, for embedded Linux systems, because the bootloaders used in such systems

are either completely different from those used in common systems or, even when they

are the same, are configured and operated in very different ways.

18

U-Boot is used in this project. U-boot provides options of booting kernel bfrom Flash,SD-

Card,USB or network. U-boot can be configured and compiled on a development host

according to the development board used. The steps are

$cd {PROJECT_ROOT}/uboot

$make mini2440_config

$make ARCH=arm CROSS_COMPILE=arm-none-linux-gnueabi-

3.6 Configuring and Compiling the Kernel

The kernel is the central software component of all Linux systems. Its capabilities very

much dictate the capabilities of the entire system. If the kernel you use fails to support

one of your target's hardware components, for instance, this component will be useless as

long as this specific kernel runs on your target.

First of all the complete Kernel source must be downloaded from the appropriate

repositories available on internet. Then required features of kernel must be selected

according to the project. For example in this project SD-Card Support, USB-Support,

LCD Support, TS support and CDC-ACM drivers (for GPS) must be selected. In general

following options can be customized according to the needs.

Code maturity level options

Loadable module support

General setup

Memory technology devices

Block devices

Networking options

ATA/IDE/MFM/RLL support

SCSI support

Network device support

Input core support

Character devices

19

Filesystems

Console drivers

Sound

Kernel hacking

Following commands are used for above steps

$cd {PROJECT_ROOT}/linux-2.6.38

$make ARCH=arm CROSS_COMPILE=arm-none-linux-gnueabi- menuconfig

$make ARCH=arm CROSS_COMPILE=arm-none-linux-gnueabi- uImage

This will take around 20-30 minutes to compile depending on the host computer. Also the

cross toolchain must be installed on the host for above process to complete successfully.

A snapshot of the above process is shown in the figure on the next page.

Fig. 3.4 Configuring and Compiling the Kernel

20

3.7 Configuring and Compiling the rootfile system

system is very important component of the Embedded Linux System from user point of

view. User is generally unaware of the kernel features. Rootfile systems contains the

components which make embedded linux useful for a particular application. It consists of

following very important components:

Libraries: Required libraries like glibc (for C programs), Qt (for GUI) , libnss (for

networking) must be selected for proper operation.

Kernel Modules: Certain hardware modules can be loaded on the fly from rootfile

system as and when required.

Kernel Image: Although it is not necessary but modern day implementations

include compressed kernel image on the rootfs itself.

Device Files: In Embedded Linux Systems hardware access is easier because of

device files. These device files can be created on the fly as well by utilities like

udev. In this project we make extensive use of device files like /dev/ttyUSB0 (for

usb to serial converter cable used with GSM modem) and /dev/ttyACM0 (for

GPS modem), /dev/fb0 (for graphics).

System Applications: These contain utilities like cd (file browsing) , grep

(parsing utility), minicom (serial communication software equivalent to

hyperterminal in windows), nano (text editor), lsusb (list usb devices), dmesg

(kernel message) etc.

Customised Applications: These contain user developed applications which could

compiled C programs or interpreted perl scripts or even a java program (provided

jvm exists).

System Initialization: It consists of scripts written to run just after kernel passes

control to user domain. It may consist of mounting virtual filesystems like /proc,

/dev etc. Networking daemons and other servers may also be spawned at this

point. It may also set certain environment variables required for system

operations. At the end it will spawn and pass the control to vital processes

required to carry out Embedded tasks. We have used busybox based system

initialization.

PTXDist is used to create complete filesystem for this project. Once ptxdist is installed

on the host system, following commands can be executed to configure and compile the

21

complete filesystem. This is a very lengthy process 2 to 2.30 hours to compile depending

on the host.

$cd {PROJECT_ROOT}/{BSP}

$ptxdist ARCH=arm menuconfig

$ptxdist –ji1 –je1 go

Fig. 3.5 Configuring and Compiling the rootfile system using ptxdist.

3.8 Hardware description ARM9 Board

The Friendly ARM Mini2440 is a single board computer based on a Samsung S3C24xx

family of ARM9 microprocessor. S3C24xx is designed to provide hand-held devices and

general applications with cost-effective, low-power, and high-performance micro-

22

controller solution in small die size. To reduce total system cost, the S3C2410A includes

the following components separate 16KB Instruction and 16KB Data Cache, MMU to

handle virtual memory management, LCD Controller (STN & TFT), NAND Flash Boot

Loader, System Manager (chip select logic and SDRAM Controller), 3-ch UART, 4-ch

DMA, 4-ch Timers with PWM, I/O Ports, RTC, 8-ch 10-bit ADC and Touch Screen

Interface, IIC-BUS Interface, IIS-BUS Interface, USB Host, USB Device, SD Host &

Multi-Media Card Interface, 2-ch SPI and PLL for clock generation.

Fig. 3.6 The ARM9 board (FriendlyARM mini2440)[20]

23

Fig. 3.7 ARM9 Block Diagram (FriendlyARM mini2440)[19]

24

3.9 ARM9 board Module Details

Power Supply

The board needs an external 5V power supply. The other reqiuired voltages are

generated on the board: 3.3V, 1.8V and 1.25V.

The reset circuit uses a MAX811 reset IC and there is an additional reset switch

on the board.

Fig 3.8 circuit diagram of system reset[20]

NAND Flash Boot Loader

1. Supports booting from NAND flash memory

2. 4KB internal buffer for booting

3. Supports storage memory for NAND flash memory after booting

UART

The three serial ports are led out on CON1 (UART0), CON2 (UART1) and CON3

(UART2). UART0 is also connected to a RS232 level converter and led out on

COM0 (DB9 connector).

USB

The USB Host is a USB type A connector and the USB Device is a USB type B

connector. For communication control the USB Device has got an additional pin:

USB_EN (GPC5).

25

Fig. 3.9 circuit diagram of serial ports on CON1 (UART0), CON2 (UART1) and CON3

(UART2[20]).

LCD Interface

The board has got a 41 pin display connector (0.5mm pitch). All signals + a four-

wire touch screen interface are on the connector. The jumper J2 is used for the

LCD driver board power supply select signal, either 5V or 3.3V supply.

GPIO

GPIO is on CON4, a 34 pin 2.0mm pitch connector.

26

Fig. 3.10 circuit diagram of LCD interface[20]

27

GSM RECEIVER Chapter-4

4.1 Introduction

Communication over wireless channel is particularly challenging. Wireless channel

provides a dynamic environment because of factors like large scale path loss, small scale

fading effects, and multipath propagation. This all leads to high (and variable) bit error

rates. So many important signal processing techniques like modulation, equalization,

diversity and channel coding are used to improve bit error rate. Also to make wireless

communication secure, we need to employ some form of encryption at some

communication layer [8].

GSM (Global System for Mobile Communication) are the standards given by ETSI

(European Telecommunication Standard Institute) for digital cellular networks. GSM

provides a robust set of protocols for communications. It has some very desirable

features:

o Encryption algorithms for communication over air

o Mobility management for providing high roaming capabilities

o FEC (Forward Error Control) at lower layers of radio interface for combating and

correcting error

o Transparent set of user-plane protocols provide freedom to user. So he can

implement vivid variety of applications using GSM Network without worrying of

wireless communication woes.

We intend to use either SMS or GPRS for transparent transfer of navigation data. The

technical specifications of GSM has been shown in the "Table 6.1"

28

Table 4.1 GSM Technical Specifications[21]

Parameter Specifications

Reverse Channel Frequency 890-915 MHz

Forward Channel Frequency 935-960 MHz

ARFCN Number 0-124 and 975-1023

Tx/Rx Freq spacing 45 MHz

Tx/Rx Time slot spacing 3 Time slots

Modulation Data Rate 270.83 Kbps

Frame Period 4.615 ms

User per frame (Full rate) 8

Time Slot Per Period 576.9 us

Bit Period 3.692 us

Modulation 0.3 GMSK

ARFCN Channel Spacing 200 KHz

Interleaving (max. delay) 40 ms

GPRS Data Rate Max 114 Kbps

4.2 GSM Modems

GSM modems act as an access point for GSM networks. Many complexities of accessing

a GSM network are hidden by GSM modem. GSM modem provides a set of commands

called AT commands (AT stands for Attention) for accessing GSM service. The

supported AT commands and their format depends on the manufacturer of the modem.

Another important point to note is that GSM Modems provide a number of interfaces to

access its capabilities like RS-232, Bluetooth, USB or even wirelessLAN. We have

decided to use a GSM modem with RS-232 interface at the remote object because RS-232

is de-facto standard available on almost all microcontrollers. RS-232 is not one of the

most robust protocols when compared to newer protocols like SPI, I2C but its simplicity

makes it desirable for local interfaces. However at the monitoring station which may have

a PC, we may go for modem with Bluetooth or USB interface, because RS-232 is no

longer available on modern PC.

29

We have already tested Nokia Bluetooth modem at the receiving station. At the

transmitting station we plan to use ScienTech GSM modem with RS-232 interface. As

mentioned earlier the AT commands supported by those modems may vary but GSM

services will remain same, so it makes no difference which modem we chose.

AT commands are shown in "Table 4.2". These are the commands which are normally

found in all GSM modems (hopefully!) [10].

Table 4.2 AT Commands

Command Description

AT Check serial interface and GSM modem working

ATE0 Turn echo off, less traffic on serial line.

AT+CGMI Manufacturer identification

AT+CGMM Model identification

AT+CGSN Product Serial Number

AT+CIMI Request IMSI

AT+CCID Card Identification

AT+CREG Network Registration Status

AT+CNMI Display of new incoming SMS.

AT+CPMS Selection of SMS memory.

ATA Answer a Call

ATD Dial a Number

ATD+VTD, AT+VTS Send DTMF

AT+CMGR Read new message from a given memory location.

AT+CMGS Send message to a given recipient.

AT+CMGD Delete message

AT+CMSS Send a message from a SIM card storage

AT+CMGW To write a message to a SIM card

30

4.3 GSM KIT

GSM receiver is used to receive the data from any user via the BTS. Today

mainlySIM300 module is used for GSM system. This chapter describes the hardware

interface of the SIMCOM SIM300 module that connects to the specific application and

the air interface. As SIM300 can be integrated with a wide range of applications, all

functional components of SIM300 are described in great detail as.

.

Fig 4.1 GSM modem SIM300

31

Fig. 4.2 Block diagram of SIM300 GSM modem

32

4.3.1 Product detail

SIM300 is a Tri-band GSM/GPRS engine that works on frequencies EGSM (Enhanced

GSM )900 MHz, DCS 1800 MHz and PCS1900 MHz. SIM300 provides GPRS multi-slot

class 10 capability and support the GPRS coding schemes CS-1, CS-2, CS-3 and CS-4.

The physical interface to the mobile application is made through a 60 pins board-to-board

connector, which provides all hardware interfaces between the module and customers’

boards except the RF antenna interface.

The keypad and SPI LCD interface will give you the flexibility to develop

customized applications.

Two serial ports can help you easily develop your applications.

Two audio channels include two microphones inputs and two speaker outputs.

This can be easily configured by AT command.

.4.3.2 Application Interface

All hardware interfaces except RF interface that connects SIM300 to the customers’

cellular application platform is through a 60-pin 0.5mm pitch board-to-board connector.

Sub-interfaces included in this board-to-board connector are described in detail in

following chapters: -

Power supply

Dual serial interface

Two analog audio interfaces

SIM interface

Indicators (Buzzer, LED)

4.4 Power supply

The power supply of SIM300 is from a single voltage source of VBAT= 3.4V...4.5V. In

some case, the ripple in a transmit burst may cause voltage drops when current

consumption rises to typical peaks of 2A, So the power supply must be able to provide

sufficient current up to 2A. For the VBAT input, a local bypass capacitor is

33

recommended. A capacitor (about 100μF, low ESR) is recommended. Multi-layer

ceramic chip (MLCC) capacitors can provide the best combination of low ESR and small

size but may not be cost effective. A lower cost choice may be a 100 μF tantalum

capacitor (low ESR) with a small (1 μF to 10μF) ceramic in parallel, which is illustrated

as following figure. And the capacitors should put as closer as possible to the SIM300

VBAT pins.

The following figure is the recommended circuit:-

Fig 4.3 VBAT input[21]

VBAT

Eight BAT pins of the board-to-board connector are dedicated to connect the supply

voltage. The power supply of SIM300 has to be a single voltage source of VBAT=

3.4V...4.5V. It must be able to provide sufficient current in a transmit burst which

typically rises to 2A.mostly, these 8 pins are voltage input.

Vmax= 4.5V

Vmin=3.4V

Vnorm=4.0V

34

Eight VBAT pins of the board-to-board connector are dedicated to connect the supply

voltage; four GND pins are recommended for grounding. BACKUP can be used to back

up the RTC.

4.5 Dual Serial interface

SIM300 provides two unbalanced asynchronous serial ports. The GSM module is

designed as a DCE (Data Communication Equipment), following the traditional DCE-

DTE (Data Terminal Equipment) connection, the module and the client (DTE) are

connected through the following signal (as following figure shows). Autobauding

supports baud rate from 1200 bps to 115200bps.

Serial port 1:-

Port/TXD - Client sends data to the RXD signal line of module

Port/RXD - Client receives data from the TXD signal line of module

Serial port 2:-

Port/TXD - Client sends data to the DGBRXD signal line of module

Port/RXD - Client receives data from the DGBTXD signal line of module

All pins of two serial ports have 8mA driver, the logic levels are described in following

table

Table 4.3 Logic levels of serial ports pin

Parameter

Min

Max

Unit

Logic low input

0 0.3*VDD_EXT

V

Logic high input

0.7 *VDD_EXT

VDD_EXT +0.3

V

Logic low output

GND

0.2

V

Logic high output

VDD_EXT -0.2

VDD_EXT

V

35

Function of Serial Port 1 & 2 supporting

Serial port 1:-

Seven lines on Serial Port Interface.

Contains Data lines /TXD and /RXD, State lines /RTS and /CTS, Control lines

/DTR, /DCD and RING;

Serial Port 1 can be used for CSD FAX, GPRS service and send AT command of

controlling module. Serial Port 1 can use multiplexing function, but you cannot

use the Serial Port 2 at the same time;

Serial Port 1 supports the communication rate as following: 1200, 2400, 4800,

9600, 19200,38400, 57600, 115200 Default as 115200bps.

Autobauding supports the communication rate as following: 1200, 2400, 4800,

9600, 19200, 38400, 57600, and 115200bps.

Serial port 2:-

Two lines on Serial Port Interface .

Only contains Data lines /TXD and /RXD

Serial Port 2 only used for transmitting AT command. It cannot be used for CSD

call, FAX call.And the Serial port 2 can not use multiplexing function;

Serial port 2 supports the communication rate as following: 9600, 19200, 38400,

57600, 115200

Fig 4.4 interface of serial ports[22]

36

4.5.1 Two audio interface

The module provides two Analogy input channels, AIN1 and AIN2, which may be used

for both microphone and line inputs. The AIN1 and AIN2 channels are identical. One of

the two channels is typically used with a microphone built into a handset. The other

channel is typically used with an external microphone or external line input. The Module

Analogy input configuration is determined by control register settings and established

using Analogy multiplexes

.4.5.2 SIM interface

There is facility of inserting SIM card on the GSM modem. The information stored in the

SIM card can be read by using the AT Command.

The SIM interface supports the functionality of the GSM Phase 1 specification and also

supports the functionality of the new GSM Phase 2+ specification for FAST 64 kbps SIM

.Both 1.8V and 3.0V SIM Cards are supported.

The SIM interface is powered from an internal regulator in the module having nominal

voltage 2.8V. All pins reset as outputs driving low. Logic levels are as described in table.

Table 4.4 Signal of SIM interface (board-to-board connector)

PIN SIGNAL DISCRIPTION

19 SIM_VDD

SIM Card Power output automatic output on SIM

mode, one is 3.0V±10%, another is 1.8V±10%.

Current is about 10mA.

21 SIM_I/O

SIM Card data I/O

23 SIM_CLK

SIM Card Clock

25 SIM_RST

SIM Card Reset

16 SIM_PRESENCE

SIM Card Presence

37

Fig 4.5 SIM interface reference circuit with 6 pins SIM card[22]

If you don’t use the SIM card detection function, you can let the SIM_PRESENCE pin

NC or connect to the GND.

4.6 Indicator

There are mainly three indicators used in SIM300 GSM modem:-

BUZZER

POWER LED

NETWORK LED

38

BUZZER

The PIN 36 on the board-to-board connector can be used to drive a buzzer to indicate

incoming call. The output volume of buzzer can be set by “AT+CRSL”.

POWER LED

Power led is used to indicate the available power on the GSM module.

NETWORK STATUS INDICATION LED

The PIN 30 on the board-to-board connector can be used to drive a network status

indication LED lamp. The working state of this pin is listed in following table

Table 4.5 Working state of network status indication LED pin

State

SIM300 function

Off SIM300 is not running

64ms On/ 800ms Off

SIM300 does not find the network

64ms On/ 3000ms Off

SIM300 find the network

64ms On/ 300ms Off

GPRS communication

4.7 ANTENNA INTERFACE

The RF interface has an impedance of 50Ω. To suit the physical design of individual

applications SIM300 offers two alternatives.

Recommended approach: antenna connector on the component side of the PCB

Antenna pad and grounding plane placed on the bottom side

39

To minimize the loss on the RF cable, it need be very careful to choose RF cable. The

value of insertion loss for SIM300 should be less then 1db.

4.7.1 Antenna connector

SIM300 use MURATA’s MM9329-2700 RF connector on the module side, here you

can use MURATA’s MXTK92XXXXX as matching connector on the application side.

4.7.2 Antenna pad

The antenna can be soldered to the pad, or attached via contact springs. To help to

ground the antenna, SIM300 comes with a grounding plane located close to the antenna

pad.

SIM300 material properties:

SIM300 PCB Material: FR4

Antenna pad: Gold plated pad

Antenna pad soldering temperature (fewer 10 seconds): 260°C

40

GPS SYSTEM CHAPTER 5

5.1 Why GPS (GPS-X-02007_UBLOX Model)?

Basically, A GPS (Global positioning system) receiver determine just four variables, i.e

longitude, latitude, height and time. Additional information (e.g speed ,direction etc) can

be derived from these four components.

Using GPS the following value can be determine anywhere on the earth :-

One’s exact location , accurate to within a range of 20m to 1 mm.

The precise time (UTC) accurate to within a range of 60ns to 5ns.

GPS (The full description is:- Navigation System with Timing and Ranging Global

Positioning System, NAVSTAR-GPS) was developed by the U.S. department of defense

(DoD) and can be used both by civilians and military personal. There are currently 28

operational satellites orbiting the earth at a height of 20,180km on 6 different orbital

planes. Their orbits are inclined at 55 degree to equator, ensuring that a least 4 satellites

are in radio communication with any point on the planet.

During the development of the GPS system, particular emphasis was placed on the

following three aspects:-

1. It had to provide users with the capability of determining position, speed and time,

whether in motion or at rest.

2. It had to have a continuous, global, 3 dimensional positioning capability with a

high degree of accuracy, Irrespective of the weather.

3. It had to offer potential for civilian use.

In order to calculate one’s exact position, all that needs to be measured is the signal

transit time between the point of observation and four different satellites whose positions

are known.

41

Fig 5.1 GPS satellites orbit the Earth on 6 orbital planes[21]

distance = transit time • the speed of signal (speed of signal is generally = light

speed)

5.2 Generating GPS signal transit time

28 satellites inclined at 55° to the equator orbit the earth every 11 hrs and 58 minutes at

a height of 20180 km on 6 different orbital planes. Each one of these satellites has a four

atomic clocks on board. Atomic clocks on board. Atomic clocks are currently the most

precise instrument known, losing a maximum of one second every 30,000 to 1,000,000

years. In order to make them even more accurate, they are regularly adjusted so

synchronized from various control point on the Earth (i.e earth segment.)

Signals are transmitted at the speed of light (300,000km/s) and therefore require approx.

67.3 ms to reach a position on the Earth’s surface located directly below the satellite.

If you wish to establish your position on land (or at sea or in the air), all you require is

an accurate clock. By comparing the arrival time of the satellite .Signal with the on

board clock time the moment the signal was emitted, it is possible to determine the transit

time of that signal.

distance =transit time • the speed of light , S=�*C

42

Measuring signal transit time and knowing the distance to a satellite is still not enough to

calculate one’s own position in 3-D space. To achieve this, four independent transit time

measurements are required. It is for this reason that signal communication with four

different satellites is needed to calculate one’s exact position. If the distance to the three

satellites is known, all possible positions are located on the surface of three spheres

whose radii correspond to the distance calculated. The position sought is at the point

where all three surfaces of the spheres intersect.

5.3 Determining a position in 3-D space In order to determine these four unknown variables, four independent equations are

needed. The four transit times required are supplied by the four different satellites (sat. 1

to sat. 4). The 28 GPS satellites are distributed around the globe in such a way that at least

4 of them are always “visible” from any point on Earth.

Fig. 5.2 Four satellites are required to determine a position in 3-D space.[21]

43

5.4 Description of the entire system

The Global Positioning System (GPS) comprises three segments:-

The space segment (all functional satellites)

The control segment (all ground stations involved in the monitoring of the system:

master control station, monitor stations, and ground control stations).

The user segment (all civil and military GPS users).

Fig 5.3 The three GPS segments[21]

44

5.4.1 space segment - The GPS satellites (Construction of a satellites)

All 28 satellites transmit time signal and data synchronized by on board atomic clocks at

the same frequency 1575.42 MHz. The minimum signal strength received on earth is

approx -158dBw to -160dBw. In accordance with the specification, the maximum

strength is approx -153dBw.

Table 5.1 L1 carrier link budget analysis modulated with the C/A code[21]

Gain (+) /loss (-) Absolute value

Power at the satellite transmitter

13.4dBW

(43.4dBm=21.9W)

Satellite antenna gain (due to

concentration

of the signal at 14.3°)

+13.4dB

Radiate power EIRP

(Effective Integrated Radiate

Power)

26.8dBW (56.8dBm)

Loss due to polarisation

mismatch

-3.4dB

Signal attenuation in space

-184.4dB

Signal attenuation in the

atmosphere

-2.0dB

Gain from the reception antenna

+3.0dB

Power at receiver input

160dBW

(130dBm=100.0*10-18W)

. The received power of –160dBW is unimaginably small. The maximum power density is

14.9 dB below receiver background noise.

45

Satellite signals

The following information (navigation message) is transmitted by the satellite at a rate of

50 bits per second:-

Satellite time and synchronization signals.

Precise orbital data (ephemeris).

Time correction information to determine the exact satellite time.

Approximate orbital data for all satellites (almanac).

Correction signals to calculate signal transit time

Data on the ionosphere.

Information on satellite health.

The time required to transmit all this information is 12.5 minutes. By using the navigation

message the receiver is able to determine the transmission time of each satellite signal and

the exact position of the satellite at the time of transmission.

Each of the 28 satellites transmits a unique signature assigned to it. This signature

consists of an apparent random sequence (Pseudo Random Noise Code,PRN) of 1023

zeros and ones.

Generating the satellite signal

Simplified block diagram On board the satellites are four highly accurate atomic clocks.

The following time pulses and frequencies. Required for day-to-day operation are derived

from the resonant frequency of one of the four atomic clocks.

The 50Hz data pulse.

The C/A code pulse (Coarse/Acquisition code, PRN-Code, coarse reception code

at a frequency of 1023 MHz), which modulates the data using an exclusive-or

operation (this spreads the data over a 1MHz bandwidth).

The frequency of the civil L1carrier (1575.42 MHz).

The data modulated by the C/A code modulates the L1 carrier in turn by using Bi-Phase-

Shift-Keying (BPSK). With every change in the modulated data there is a180°change in

the L1 carrier phase.

46

Fig 5.4 Simplified satellite block diagram[21]

Fig 5.5 Data structure of a GPS satellite[21]

5.4.2 Control segment

The control segment (Operational Control System OCS) consists of a Master Control

Station located in the state of Colorado, five monitor stations equipped with atomic clocks

47

that are spread around the globe in the vicinity of the equator, and three ground control

stations that transmit information to the satellites.

The most important tasks of the control segment are:-

Observing the movement of the satellites and computing orbital data (ephemeris)

Monitoring the satellite clocks and predicting their behavior

Synchronizing on board satellite time

Relaying precise orbital data received from satellites in communication

Relaying the approximate orbital data of all satellites (almanac)

Relaying further information, including satellite health, clock errors etc.

The control segment also oversees the artificial distortion of signals (SA, Selective

Availability), in order to degrade the system’s positional accuracy for civil use. System

accuracy had been intentionally degraded up until May 2000 for political and tactical

reasons by the U.S. Department of Defense (DoD), the satellite operators. It was shut

down in May 2000, but it can be started up again, if necessary, either on a global or

regional basis

.

5.4.3 User segment

The signals transmitted by the satellites take approx.67 milliseconds to reach a receiver.

As the signals travel at the speed of light, their transit time depends on the distance

between the satellites and the user. Four different signals are generated in the receiver

having the same structure as those received from the 4 satellites. By synchronizing the

signals generated in the receiver with those from the satellites, the four satellite. Signal

time shifts Δt are measured as a timing mark. The measured time shifts Δt of all 4

satellite. Signals are used to determine signal transit time.

In order to determine the position of a user, radio communication with four different

satellites is required. The relevant distance to the satellites is determined by the transit

time of the signals. The receiver then calculates the user’s latitude ϕ, longitude λ, height h

and time t from the range and known position of the four satellites.

48

Signal recovery and the identification of the satellites takes place by means of correlation.

As the receiver is able to recognize all C/A codes currently in use, By systematically

shifting and comparing every code with all incoming satellite signals, a complete match

will eventually occur (that is to say that the correlation factor CF is one), and a correlation

point will be attained.

The correlation point is used to measure the actual signal transit time and, as previously

mentioned, to identify the satellite

.

Fig.5.6 Measuring signal transit time[21]

Fig 5.7 Demonstration of the correction process across 30 bits[21]

49

The quality of the correlation is expressed here as CF (correlation factor).The value range

of CF lies between Minus one and plus one and is only plus one when both signals

completely match (bit sequence and phase).

�� =1

�∗�[(��) − (��)]

�

��

mB : number of all matched bits

uB : number of all unmatched bits

N : number of observed bits.

5.5 THE GPS NAVIGATION MESSAGE

The navigation message is a continuous stream of data transmitted at 50 bits per second.

Each satellite relays the following information to Earth:-

System time and clock correction values.

Its own highly accurate orbital data (ephemeris).

Approximate orbital data for all other satellites (almanac).

System health etc.

The navigation message is needed to calculate the current position of the satellites and to

determine signal transit times.

Structure of the navigation message

A frame is 1500 bits long and takes 30 seconds to transmit. The 1500 bits are divided into

five subframes each of 300 bits (duration of transmission 6 seconds).Each subframe is in

turn divided into10 words each containing 30bits. Each subframe begins with a telemetry

word and a handover word (HOW). A complete navigation message consists of 25 frames

(pages).The structure of the navigation message is illustrated in diagrammatic format in

above figure

50

Fig 5.8 Structure of the entire navigation message[21]

.5.6 Information contained in the subframes

A frame is divided into five subframes, each subframe transmitting different information:-

Subframe 1 contains the time values of the transmitting satellite, including the

parameters for correcting signal transit delay and on board clock time, as well as

information on satellite health and an estimation of the positional accuracy of the

satellite. Subframe 1 also transmits the so-called 10-bit week number (a range of

values from 0 to 1023 can be represented by 10 bits). GPS time began on Sunday,

6th January 1980 at 00:00:00 hours. Every 1024 weeks the week number restarts

at 0.

Subframes 2 and 3 contain the ephemeris data of the transmitting satellite. This

data provides extremely accurate information on the satellite’s orbit.

51

Subframe 4 contains the almanac data on satellite numbers 25 to 32 (N.B. each

subframe can transmit data from one satellite only), the difference between GPS

and UTC time and information regarding any measurement errors caused by the

ionosphere.

Subframe 5 contains the almanac data on satellite numbers 1 to 24 (N.B. each

subframe can transmit data from one satellite only).All 25 pages are transmitted

together with information on the health satellite numbers 1 to 24.

5.7 CALCULATING POSITION

Although originally intended for purely military purposes, the GPS system is

used today primarily for civil applications, such as surveying, navigation (air, sea and

land), positioning, measuring velocity, determining time, monitoring stationary and

moving objects, etc. The system operator guarantees the standard civilian user of the

service that the following accuracy (Table 4.1) will be attained for 95% of the time

(2drms value ):

Table 5.3 Accuracy of the standard civilian service

Horizontal accuracy Vertical accuracy Time accuracy

≤13 m ≤22 m ~40ns

With additional effort and expenditure, e.g. several linked receivers (DGPS), longer

measuring time, and special measuring techniques (phase measurement) positional

accuracy can be increased to within a centimeter.

5.7.1 Calculating a position

The principle of measuring signal transit time (evaluation of pseudo-range.In order for a

GPS receiver to determine its position, it has to receive time signals from four different

satellites (Sat 1 ... Sat 4), to enable it to calculate signal transit time ∆t1 ... ∆t4 (Figure

5.8).

52

Fig. 5.9 Four satellite signals must be received[21]

Calculations are effected in a Cartesian, three-dimensional co-ordinate system with a

geocentric origin (Figure4.1). The range of the user from the four satellites R1, R2, R3

and R4 can be determined with the help of signal transit times ∆t1, ∆t2, ∆t3 and ∆t4

between the four satellites and the user. As the locations XSat, YSat and ZSat of the four

satellites are known, the user co-ordinates can be calculated.

Due to the atomic clocks on board the satellites, the time at which the satellite signal is

transmitted is known very precisely. All satellite clocks are adjusted or synchronised with

each another and universal time co-ordinated. In contrast, the receiver clock is not

synchronised to UTC and is therefore slow or fast by ∆t0. The sign ∆t0 is positive when

the user clock is fast. The resultant time error ∆t0 causes inaccuracies in the measurement

of signal transit time and the distance R. As a result, an incorrect distance is measured

that is known as pseudo distance or pseudo-range PSR

53

Fig. 5.10 Three dimensional co-ordinate system[22]

∆�� = ∆t +∆t�

PSR=∆��. C =(Δt + ∆t�)⋅C

PSR =R + ∆t�⋅c ……………………………. eqn.-1

R: True range of the satellite from the user

C: Speed of light

∆t:signal transit time from the satellite to the user

∆t�: difference between the satellite clock and the user clock

PSR: pseudo-range

The distance R from the satellite to the user can be calculated in a Cartesian system as follows:

54

R=�(�� − ��)� − (�� − ��)

� − (�� − ��)� …………….eqn.-2

Thus eqn.(2) into eqn. (3)

PSR=�(�� − ��)� − (�� − ��)� − (�� − ��)� + C.∆t�

In order to determine the four unknown variables (∆t�, ��, �� and ��), four

independent equations are necessary.

XAnw: means unknown value of X

The following is valid for the four satellites (i = 1 ... 4):

PSR�=��_� − ��− ��_� − ��

�− ��_� − ��

� + C.∆t�

5.7.2 Error consideration and satellite signal

Error components in calculations have so far not been taken into account. In the case of

the GPS system, several causes may contribute to the overall error:

Satellite clocks although each satellite has four atomic clocks on board, a time

error of just 10 ns creates an error in the order of 3 m.

Satellite orbits The position of a satellite is generally known only to within

approx. 1 to 5 m.

Speed of light The signals from the satellite to the user travel at the speed of light.

This slows down when traversing the ionosphere and troposphere and can

therefore no longer be taken as a constant.

Measuring signal transit time The user can only determine the point in time at

which an incoming satellite signal is received to within a period of approx. 10-20

ns, which corresponds to a positional error of 3-6 m. The error component is

increased further still as a result of terrestrial reflection (multipath).

55

Satellite geometry The ability to determine a position deteriorates if the four

satellites used to take measurements are close together. The effect of satellite

geometry on accuracy of measurement.

The errors are caused by various factors that are detailed in Table 5.4, which includes

information on horizontal errors. 1 sigma (68.3%) and 2 sigma (95.5%) are also given.

Accuracy is, for the most part, better than specified, the values applying to an average

satellite constellation.

Table 5.2 Cause of errors

Cause of error

Error

Effects of the ionosphere 4 m

Satellite clocks 2.1 m

Receiver measurements 0.5 m

Ephemeris data 2.1 m

Effects of the troposphere 0.7 m

Multipath 1.4 m

5.8 GPS RECEVIER

56

Fig. 5.11 Smart GPS receiver

Fig 5.12 Simplified block diagram of a GPS receiver[21]

Antenna

The antenna receives extremely weak satellite signals on a frequency of

57

1572.42MHz. Signal output is around –163dBW. Some antenna have a 3dB gain

.LNA 1

This low noise amplifier (LNA) amplifies the signal by approx. 15 ... 20dB.

HF filter

The GPS signal bandwidth is approx. 2MHZ. The HF filter reduces the affects of

signal interference. The HF stage and signal processor actually represent the

special circuits in a GPS receiver and are adjusted to each other.

HF Stage

The amplified GPS signal is mixed with the frequency of the local oscillator. The

filtered IF signal is maintained at a constant level in respect of its amplitude and

digitalised via Amplitude Gain Control (AGC).

IF Filter

The intermediate frequency is filtered out using a bandwidth of 2MHz. The image

frequencies arising at the mixing stage are reduced to a permissible level.

Signal processor

Up to 16 different satellite signals can be correlated and decoded at the same time.

Correlation takes place by constant comparison with the C/A code. The HF stage

and signal processor are simultaneously switched to synchronize with the signal.

The signal processor has its own time base (Real Time Clock, RTC). All the data

ascertained is broadcast (particularly signal transit time to the relevant satellites

determined by the correlator), and this is referred to as source data. The signal

processor can be offset by the controller via the control line to function in various

operating mode.

Controller

58

Using the source data ,the controller calculates position ,time ,speed and course

etc .It controls the signal processor and relays the calculated values to the display.

Important information (such as ephemeris ,the most recent position etc.)are

decoded and saved in RAM .The program and the calculation algorithms are

saved in ROM.

Current supply

The power supply delivers the necessary operational voltage to all levels of

electronic component.

5.9 Basic design of a GPS module

Fig 5.13 Typical block diagram of a GPS module[21]

59

GPS modules have to evaluate weak antenna signals from at least four satellites ,in order

to determine a correct three-dimensional position. A time signal is also often emitted in

addition to longitude ,latitude and height .This time signal is synchronised with UTC

(Universal Time Coordinated) .From the position determined and the exact time

,additional physical variables ,such as speed and acceleration can also be calculated .The

GPS module issues Information on the constellation ,satellite health ,and the number of

visible satellites etc. Figure shows a typical block diagram of a GPS module.

The signals received (1575.42 MHz) are pre-amplified and transformed to a lower

intermediate frequency. The reference oscillator provides the necessary carrier wave for

frequency conversion, along with the necessary clock frequency for the processor and

correlator. The analogue intermediate frequency is converted into a digital Signal by

means of a 2-bit ADC.

Signal transit time from the satellites to the GPS receiver is ascertained by correlating

PRN pulse sequences .The Satellite PRN sequence must be used to determine this time,

otherwise there is no correlation maximum. Data is recovered by mixing it with the

correct PRN sequence. At the same time,the useful signal is amplified above the

Interference level upto 16 satellite signals are processed simultaneously. The control and

generation of PRN sequences and the recovery of data is carried out by a signal processor

.Calculating and saving the position, including the variables derived from this ,is carried

out by a processor with a memory facility.

5.10 The NMEA Data interface

In order to relay computed GPS variables such as position, velocity, course etc. To a

peripheral for example computer, screen, transceiver GPS modules have a serial interface

(TTL or RS-232 level). The most important elements of receiver information are

broadcast via this interface in a special data format. This format is\ standardised by the

National Marine Electronics Association (NMEA) to ensure that data exchange takes

place without any problems. Nowadays, data is relayed according to the NMEA- 0183

specification. NMEA has specified data sets for various Applications. For Example

60

GNSS (Global Navigation Satellite System), GPS, Loran, Omega, Transit and also for

various manufacturers.

The following seven data sets are widely used with GPS modules to relay GP information

1. GGA (GPS Fix Data, fixed data for the Global Positioning System)

2. GLL (Geographic Position – Latitude/Longitude)

3. GSA(GNSS DOP and Active Satellites, degradation of accuracy and the number

of active satellites in the Global Satellite Navigation System)

4. GSV (GNSS Satellites in View, satellites in view in the Global Satellite

Navigation System)

5. RMC (Recommended Minimum Specific GNSS Data)

6. VTG (Course over Ground and Ground Speed, horizontal course and horizontal

velocity)

7. ZDA (Time & Date)

5.10.1 NMEA Protocol Frame

Following is the frame format of NMEA Protocol

$ <Address> <,value> *<Checksum> <CR> <LF>

$ - This is the start character .In NMEA Protocol the starting character is always

dollar($)

Second field is address .This field is subdivided into 2 field .First field indicate the

information originating from a GPS appliance. It is always GP for a GPS receiver.

The second field is indicate the data set type .for example GGA, GLL, GSA, GSV

etc.

Third field is Data field .This content the information of data like Latitude,

Longitude, Altitude, Time. Comma used as a separator for different items of

information

Four field is for check sum Asterisk ( *) used as a separator for the checksum.

This field start with a ‘*’ and consists of two characters representing a hex

number. The checksum is the exclusive OR of all characters between ‘$’ and ‘*’

Check is for checking the entire data.

61

Last field <CR> <LF> indicate the end of the data set: carriage return (<CR>) and

line feed, (<LF>).

Following NMEA Protocol is found in the GPS receiver

Table 5.3 NMEA Data

$GPRMC,130303.0,A,4717.115,N,00833.912,E,000.03,043.4,200601,01.3,W*7D<CR><LF>

$GPZDA,130304.2,20,06,2001,,*56<CR><LF>

$GPGGA,130304.0,4717.115,N,00833.912,E,1,08,0.94,00499,M,047,M,,*59<CR><LF>

$GPGLL,4717.115,N,00833.912,E,130304.0,A*33<CR><LF>

$GPVTG,205.5,T,206.8,M,000.04,N,000.08,K*4C<CR><LF>

$GPGSA,A,3,13,20,11,29,01,25,07,04,,,,,1.63,0.94,1.33*04<CR><LF>

$GPGSV,2,1,8,13,15,208,36,20,80,358,39,11,52,139,43,29,13,044,36*42<CR><LF>

$GPGSV,2,2,8,01,52,187,43,25,25,074,39,07,37,286,40,04,09,306,33*44<CR><LF>

$GPRMC,130304.0,A,4717.115,N,00833.912,E,000.04,205.5,200601,01.3,W*7C<CR><LF>

$GPZDA,130305.2,20,06,2001,,*57<CR><LF>

$GPGGA,130305.0,4717.115,N,00833.912,E,1,08,0.94,00499,M,047,M,,*58<CR><LF>

$GPGLL,4717.115,N,00833.912,E,130305.0,A*32<CR><LF>

$GPVTG,014.2,T,015.4,M,000.03,N,000.05,K*4F<CR><LF>

$GPGSA,A,3,13,20,11,29,01,25,07,04,,,,,1.63,0.94,1.33*04<CR><LF>

$GPGSV,2,1,8,13,15,208,36,20,80,358,39,11,52,139,43,29,13,044,36*42<CR><LF>

$GPGSV,2,2,8,01,52,187,43,25,25,074,39,07,37,286,40,04,09,306,33*44<CR><LF>

.

5.10.2 GGA data set

62

The GGA data set (GPS Fix Data) contains information on time , longitude and latitude,

the quality of the system, the number of satellites used and the height.

$GPGGA,130305.0,4717.115,N,00833.912,E,1,08,0.94,00499,M,047,M,,*58<CR><LF>

Following are the function of the individual characters or character sets.

Table 5.4 GGA Data

Field Description

$ Start of the data set

GP information originating from a GPS appliance

GGA Data set identifier

130305.0 UTC positional time: 13h 03min 05.0sec

4717.115 Latitude: 47° 17.115 min

N Northerly latitude (N=north, S= south)

00833.912 Latitude: 8° 33.912min

E Easterly longitude (E= east, W=west)

1 GPS quality details (0= no GPS, 1= GPS, 2=DGPS)

08 Number of satellites used in the calculation

0.94 Horizontal Dilution of Precision (HDOP)

00499 Antenna height data (geoid height)

M Unit of height (M= meter)

047 Height differential between an ellipsoid and geoid

M Unit of differential height (M= meter)

,, Age of the DGPS data (in this case no DGPS is used)

0000 identification of the DGPS reference station

* Separator for the checksum

63

58 Checksum for verifying the entire data set

<CR><LF> End of the data set

5.10.3 GLL data set

The GLL data set (geographic position latitude/longitude) contains information on

latitude and longitude, time and health.

Example of a GLL data set:-

$GPGLL, l4717.115 ,N, 00833.912, E ,130305.0 ,A*32 <CR><LF>

Following is meaning of each character

Table 5.5 GPGLL Data

$ Start of data set

GP Information originating from a GPS appliance

GLL Data set identifier

4717.115 Latitude: 47° 17.115 min

N Northerly latitude (N=north, S= south)

833.912 Longitude: 8° 33.912min

E Easterly longitude (E=east, W=west)

130305.0 UTC positional time: 13h 03min 05.0sec

A Data set quality: A means valid (V= invalid)




5.10.4 GSA data set

64

The GSA data set (GNSS DOP and Active Satellites) contains information on the

measuring mode (2D or 3D), the number of satellites used to determine the position

and the accuracy of the measurements (DOP: Dilution of Precision)

An example of a GSA data set:

$GPGSA, A, 3, 13, 20, 11, 29, 01, 25, 07 ,04,,,,,1.63, 0.94, 1.33*04<CR><LF>

Following are the description of each character

Table 5.6 GSA Data

$ Start of the data set

GP Information originating from a GPS appliance

GSA Data set identifier

A Calculating mode (A= automatic selection between 2D/3D mode, M=

manual selection Between 2D/3D mode)

3 Calculating mode_(1=_none,_2=2D,_3=3D)_

13 ID number of the satellites used to calculate position








,,,, Dummy for additional ID numbers (currently not used)

1.63 PDOP (Position Dilution of Precision)

.94 HDOP (Horizontal Dilution of Precision)

1.33 VDOP (Vertical Dilution of Precision)




65

ALGORITHM AND RESULTS CHAPTER-6

66

Fig. 6.1 Algorithm

6.1 Algorithm

67

First of all GSM Modem must be registered to Network. Command ‘AT+CREG?’ is sent

to the SIM300 module to check the status. If registration step is not successful then the

above command should be again sent.

If the registration is successful then signal quality is checked using ‘AT+CSQ?’. The

obtained values are displayed on console itself.

A counter is initialized with value 10 (this is because gps data is sent to control station at

interval of 10 seconds). But note that data obtained is shown on local console at normal

rate of 1 sample per second.

Once counter is set, data packets from GPS receiver is received via USB driver interface

‘/dev/ttyACM0’. From these packets like GPGLL, GPRMC, GPGSA are extracted.

From GPGLL packet longitude, latitude and time stamp are saved into buffer. From

GPGGA packet height is extracted and saved to buffer. Similarly from GPGSV the

number of satellites in view and from GPRMC speed is saved.

This data from buffer is sent to local console ‘/dev/tty1’ which is lcd at the rate of 1

sample per second. Once the data is sent the counter is counter is decremented.

If 10 seconds has elapsed then message is sent via GSM Modem using command

‘AT+CMGS’. After this counter is reset to initial value and the process is repeated.

This is the simplified description of the operation of Automatic Vehicle Locator

developed in this project. For demonstration and measurement purposes, a similar

program was run but the data was sampled continuously and extracted data was

continuously dumped to a file and displayed on local console. Here for demonstration

purpose the screenshot is shown next section.

6.2 Results

Figure 6.2 and Figure 6.3 shows the output data at two locations in SVNIT Campus.

Validity of this data was checked using Google Maps. Also while testing the project it

was observed that GPS data is accurate when used in outdoors. This fact could be

explained because in crowded places and indoors there could be multiple path

components causing problem. The longitude and latitude are shown in degree and

minutes multiplied by 100. Another point to note here is that number of satellites in view

generally depends on time of the day, and the location at which the remote object is. But

user should not worry about the number of satellites because 4 satellites are enough to

calculate the exact coordinates. Speed is shown in Nautical Miles per hour because this is

defacto in GPS receivers. Height shown in the data are the measured from geodetic datum

which could be approximated as mean sea level for simple applications.

68

Fig 6.4 shows the data obtained on a GSM terminal (control station). The format of the

message is self explanatory. However point to note is that there is time stamp with each

message and message are at interval of 10 seconds.

Fig.6.2 Snapshot at Location A (SVNIT Campus, Hostel-6 Block B)

69

Fig. 6.3 Snapshot at location B (SVNIT CAMPUS Hostel-6 Block D)

Fig. 6.4 Message Received on GSM Terminal

70

Fig 6.5 Messages received when GSM Terminal is Connected to PC via PC Suite

Packets received from GPS receiver via NMEA protocol can be seen in raw format on

‘minicom’ or ‘microcom’. This is particularly useful to study the data formats used in

NMEA protocols. This is shown in figure 6.6. However note that when reception is weak

the packets would be empty. This condition was taken care of in programs. All the

packets contain the checksum at the end (after *). This is useful to see if there was any

error in received packet. No checksum problems were found during the project phase.

This could be because USB uses differential signalling which is much more reliable and

immune to error than RS-232 interface.

71

Fig 6.6 Raw NMEA data shown on minicom

72

6.3 APPLICATION

Using the Global Positioning System (GPS) ,a process used to establish apposition at any

point on the globe) the following two values can be determined anywhere on Earth .

One’s exact location (longitude, latitude and height co-ordinates) accurate to

within a range of 20 m to approx.1mm.

The precise time (world time, Universal Time Coordinated, UTC) accurate to

within a range of 60ns to approx.1ns.

Various additional variables can be derived from the three-dimensional position and the

exact time, such as

Speed

Acceleration

Course

Local time

Range instrument

AVL (Automatic vehicle locator) we can track the exact position of any vehicle or

moving object.

Fig 6.7 AVL application[27]

73

Other application

1. Transport companies, logistics in general (aircraft, water-borne craft and

road vehicle)

2. Railways

3. Geographical tachographs

4. Fleet management

5. Navigation systems

6. Military

Science and Research

GPS has readily found itself a place in archaeology ever since this branch of science

began to use aerial and satellite imaging.

In land surveying, GPS has virtually become an exclusive method for pinpointing sites in

basic networks. Everywhere around the world, continental and national GPS networks are

emerging that, in conjunction with the global ITRF, provide homogenous and highly

accurate networks of points for density and point to point measurements. At a regional

level, the number of tenders to set up GPS networks as a basis for geo-information

systems and cadastral land surveys is growing.

Fig 6.8 Application in Science and Research[27]

74

Conclusion Chapter-7

For physical implementation of this system, there could be a number of design

alternatives. In earlier phase of project RTOS and ARM7 was employed along with U-

Blox GPS modem and SIM300 GSM modem. But later on Embedded linux was chosen

over RTOS and ARM9 was chosen over ARM7 because of performance reasons. This

time same GPS receiver is used as navigation system. NMEA is used as communication

protocol between controller and GPS receiver over a USB interface. GSM is used to

provide communication link between remote object and monitoring system. GSM modem

is interfaced to controller using AT protocols over a RS232 interface. controller in this

case is high performance application domain processor SAMSUNG S3C2440 (ARM9). It

runs self compiled Embedded linux.

Performance of GPS and GSM receivers is limited by signal reception. So antenna plays

an important role. Also Embedded linux provides a lot of flexibility in terms of available

libraries and device drivers. Libraries like glibc, Qt were used. Device drivers like CDC-

ACM (for GPS modem) and PL2303 (for GSM modem) were used.

The data is extracted by controller from NMEA packets sent by GPS receiver. From these

packets controller calculates useful data like longitude, latitude, height, speed, timestamp.

These data are saved in a specific format and sent over GSM modem every 10s. The time

is hardcoded but can be easily changed. This time will depend on the application for

example a speed measuring or height profiling applications would require frequent data

but normal tracking applications could work with lesser frequent data. The results have

been attached in appendix.

75

List of References

[1]. French G.T., An Introduction to GPS systems, GeoResearch Inc., 1996

[2]. Sloss, Symes, Wright, ARM System Developer's Guide, Morgan Kaufman

Publishers, 2005

[3]. Furber S., ARM System on Chip Architecture, Pearson Education, 2000

[4]. LPC2138 User Manual, Rev.3,

http://www.nxp.com/documents/user_manual/UM10120.pdf

[5]. ARM7TDMI Technical Reference Manual,

http://infocenter.arm.com/help/topic/com.arm.doc.ddi0210c/DDI0210B.pdf

[6]. Noergard T., Embedded System Architecture, Newnes Publishers, 2005

[7]. Labrosse J.J., MicroC/OS-II: The Real Time Kernel, Viva Publishers, 2002

[8]. Rappaport T., Wireless Communications, Prentice Hall Inc., 2002

[9]. Eberspacher, Vogel, Bettstetter, Hartmann, GSM Architecture Protocol and

Services, John Wiley & Sons Ltd., 2009

[10]. AT Commands Interface Guide,

http://www.coster.info/costerit/teleges/doc/gsm822w.pdf

[11]. Rabbany A.E., The Global Positioning Systems, Artech House, 2006

[12]. Y. Lv, X. Li, X, Peng, and J. Sun, "Design of the navigation system of UAV in

high dynamic circumstance based on GPS," Proceedings of 6th International

Symposium on Test and Measurement, Vol. 7, 2005

[13]. Tsui Y., Bao J., Fundamentals of Global Positioning System Receivers: A

Software Approach, John Wiley & Sons, 2000

[14]. Takamura J., Shimizu K., Tanaka T., The Improvement of the Shift Error in GPS

Standard Positioning Service, SICE Annual Conference in Fukui, August 4-6,

2003

[15]. Joong-hee Han; Kwon, J.H.; Impyeong Lee; Kyoungah Choi; , "Position and

Attitude Determination for UAV-Based GPS, IMU and AT without GCPs," Multi-

Platform/Multi-Sensor Remote Sensing and Mapping (M2RSM), 2011

International Workshop on , vol., no., pp.1-5, 10-12 Jan. 2011

76

[16]. Michael S. Braach and A.J. Van Dierendonck,"GPS receiver architectures and

measurements" in proceedings of the IEEE vol81, no.1, january 1999

[17]. Karim Yaghmour, ”Building Embedded Linux Systems”, O’Reilly & Associates,

2003

[18]. Cristopher Hallinan, ”Embedded Linux Primer”, Prentice Hall, 2010

[19]. “User Manual S3C2410A Revision 1.0”, Samsung Electronics, 2004

[20]. “S3C2410-III v2.0 Linux User Manual Revision 1.0”, Embest Info, 2008

[21]. Jean Marie“GPS Basics Introduction to the system Application overview”, Ublox,

2002

[22]. “SIM300 Hardware Specifications Version 1.06”, SIMCOM Ltd., 2005

77

List of Acronyms

AVL Automatic Vehicle System

BPSK Binary phase Shift keying

CDC ACM Communication Device Class Abstract Control Model

CF Correlated Function

DGPS Differential Global Positioning System

ETSI European Telecommunications Standards Institute

FCC Federal Communications Commission

GLONASS Global Navigation Satellite System

GPRS General Packet Radio Service

GPS Global Positioning System

GGSN Gateway GPRS Support Node

GSM Global System for Mobile communication

OCS Operational Control System

NMEA National Marine Electronics Association

MCU Microcontroller unit

MSC Mobile Switching Centre

MCS Micro-controller Unit

PRN Pseudo Random Noise

PPS Precise Positioning Service

RTCM Radio Technical Commission for Maritime Services

SGSN Serving GPRS Support Node

SMS Short Message Service

SP Stack Pointer

SPS Standard Positioning Service

Documents

Automatic Vehicle Locator [Author Avinash Jha]