WeCreativez WhatsApp Support
Welcome! My name is Damaris. I am online and ready to help you via WhatsApp chat. Let me know if you need my assistance.
The Complete Material for this Topic is Available for Download.

Download this complete Project material titled; Development Of A Modified Link Budget Forlow Earth Orbiting (Leo)-Based Land Mobile Satellite Communications System with abstract, chapters 1-5, references, and questionnaire. Preview Abstract or chapter one below

  • Format: PDF and MS Word (DOC)
  • pages = 65

 3,000

100% Money-Back Guarantee

Contact us - 08060082010, 08107932631, 08157509410, Edustoreng@gmail.com

ABSTRACT

 

This research work presents the development of a Modified Link Budget for Low Earth Orbiting (LEO)-Based Land Mobile Satellite Communications System operating at Ku, K and Ka frequency bands by taking into cognizance the effect of additional loss due to Doppler frequency shift. Doppler frequency shift poses the problem of receiving higher or lower frequencies than the original transmitted frequency, this may be as a result of a relative movement between the source of the signal and the object (satellite or receiver) or both. In satellite communication system, this phenomenon constitutes the problem of signal loss.Effect of Doppler shift on satellite link budget is assumed negligible in conventional approach thereby resulting in the design of an unrealistic link budget, particularly in Low earth orbit (LEO) where it is more pronounced. In view of this, a more reliable approach to the estimation of satellite link budget at Ku, K, and Ka bands by the inclusion of Doppler frequency shift effect was investigated and its effect was investigated at different satellite orbits (LEO, MEO and GEO). The results obtained show that at maximum satellite converge angle and central frequencies for Ku, K and Ka bands, the Doppler frequencies for LEO (780 km) are: 325.50 kHz, 423.20 kHz and 726.90 kHz; for MEO (20000 km) we have 88.33 kHz, 114.80 kHz and 197.30 kHz; while GEO (35786 km) stood at 55.26 kHz, 71.84 kHz and 123.40 kHz . Variation of Doppler frequency shift with respect to the latitude (location) of the earth’s terminal relative to the satellite motion was also studied. A typical earth terminal location in the range of 0 km – 100 km was selected for the study; from which it was verified that effect of Doppler shift in LEO increased as the distance from the initial location of the user terminal increased. These analyses further confirm that Doppler effect is more pronounced in LEO than in MEO and GEO. Comparative analyses between the conventional and the modified link
viii
budget at Ku, K and Ka bands was achieved thereof. The results obtained show the Carrier to Noise density ratio for Ku frequency banddropped by 40% (from 25dB without Doppler shift to 15dB with Doppler shift). The Carrier to Noise density ratio for K frequency band dropped by 57% (from 70dB without Doppler shift to 30dB with Doppler shift). The Carrier to Noise density ratio for Ka frequency band dropped by 52% (from 110dB without Doppler shift to 53dB with Doppler shift).
This further confirmed that Doppler shift is most pronounced at LEO orbit hence the need to incorporate its effect in link budgeting. This work was validated against the work of Snehasis and Barsha, (2014).The results obtained through comparison show the Carrier to Noise density ratio for Ku frequency banddropped by 58% (from 31dB without Doppler shift to 13dB with Doppler shift). The Carrier to Noise density ratio for K frequency band dropped by 62% (from 54dB without Doppler shift to 20dB with Doppler shift). The Carrier to Noise density ratio for Ka frequency band dropped by 55% (from 85dB without Doppler shift to 38dB with Doppler shift). This clearly shows the need for inclusion of Doppler shift effect in LEO-based link budget.

 

TABLE OF CONTENTS

COVER PAGE …………………………………………………………………………………………………. ..i
TITLE PAGE ………………………………………………………………………………………………….. ..ii
DECLARATION ………………………………………………………………………………………………. iii
CERTIFICATION ………………………………………………………………………………………………. iv
DEDICATION …………………………………………………………………………………………………. …v
AKNOWLEDGEMENT ………………………………………………………………………………………………vi
ABSTRACT ……………………………………………………………………. ………………………….. vii
TABLE OF CONTENTS ……………………………………………………………………………………………….. viii
LIST OF FIGURES…………………………………………………………….. …………………………………………xiii
LIST OF TABLES .. ………………………………………………………………………………………………………. ……xiv
LIST OF ABBREVIATIONS …………………………………………………………………………………………. xv
CHAPTER ONE: INTRODUCTION
1.1 Background………………………………………………………………………………………………. 1
1.2 Aim and objectives……………………………………………………………………………………. 4
1.3 Statement of problem…………………………………………………………………………………. 5
1.4 Methodology ………………………………………………………………………………………………5
1.5 Significant contribution of the Research ……………………………………………………6
x
1.6 Thesis outline……………………………………………………………………………………………. 8
CHAPTER TWO: LITERATURE REVIEW AND THEORETICAL BACKGROUND
2.1 Introduction………………………………………………………………………………………………. 9
2.2 Review of fundamental concepts…………………………………………………………………. 9
2.2.1 Atmospheric Absorption loss …………………………………………………………………….. 10
2.2.2 Attenuation caused by rain…………………………………………………………………………. 10
2.2.3 Attenuation caused by cloud or fog……………………………………………………………. 11
2.2.4 Attenuation caused by snow ……………………………………………………………………. 11
2.2.5 Scintillation of atmospheric and Ionospheres…………………………………………….. 12
2.2.6 Gaseous Absorption………………………………………………………………………………… 12
2.2.7 Polarization loss or polarization effects………………………………………………………. 13
2.2.8 Free Space loss…………………………………………………………………………………………. 13
2.2.9 Antenna Misalignment Loss ……………………………………………………………………. 14
2.2.10 Feeder Line Loss ………………………………………………………………………………… 15
2.2.11 Total transmission path loss………………………………………………………………………… 15
2.2.12 Doppler frequency Shift…………………………………………………………………………….. 16
2.2.13 Classical Link Budget analysis…………………………………………………………………… 19
xi
2.3.13.1Effective Isotropic Radiated power…………………………………………………………………19
2.3.13.2 Power Flux Density……………………………………………………………………………………..19
2.3.13.3 Antenna gain……………………………………………………………………………………………….20
2.3.13.4 Link Power equation……………………………………………………………………………………21
2.3.13.5 Figure of Merit……………………………………………………………………………………………22
2.3.13.6Carrier of Noise Density Ratio………………………………………………………………………23
2.3.13.7 Energy per bit to noise density………………………………………………………………………23
2.3.13.8 Overall conventional Link Budget…………………………………………………………………24
2.3.13.9Link Margin………………………………………………………………………………….. …………..25
2.2.13.10 Radio Frequency Band……………………………………………………………………………… 25
2.2.13.10.1 L band ………………………………………………………………………………………………….26
2.2.13.10.2 S band…………………………………………………………………………………………………..26
2.2.13.10.3 C band ………………………………………………………………………………………………….26
2.2.13.10.4 X band………………………………………………………………………………………………….27
2.2.13.10.5 Ku band………………………………………………………………………………………………..27
2.2.13.10.6 Ka band………………………………………………………………………………………………..27
2.2.13.11 Modulation……………………………………………………………………………………………….27
xii
2.3 Review of Similar Research Work………………………………………………………………………..29
CHAPTER THREE: DESIGN METHODOLOGY
3.1 Introduction ……………………………………………………………………………………………………..34
3.2 Methodology…….. ……………………………………………………………………………………………..34
3.2.1Selection of Key Parameters…………………………………………………………………………….34
3.2.1.1 Selection of carrier frequency………………………………………………………………………..35
3.2.1.2 Selection of satellite transmit power……………………………………………………………….36
3.2.1.3 Selection of modulation and demodulation …………………………………………………….37
3.2.2Development of a Mathematical Model of Doppler Frequency shift…………………….37
3.2.2.1 Effect of the earth’s Terminal Location on Doppler Frequency………………………..41
3.2.3 Development of a Modified Model of Satellite Link Budget by including Doppler Effect……………………………………………………………………………………………………….42
3.3 Modified Link Model Validation …………………………………………………………..44
3.4 Conclusion………………………………………………………………………………………………….46
CHAPTER FOUR:RESULTS AND ANALYSIS
4.1 Introduction…………………………………………………………………………………………………..47
4.2 Variation of Doppler Frequency with orbital height …………………………………….47
4.3 Effect of user terminal Location on Doppler frequency………………………………….49
xiii
4.4 Variation of carrier to noise density ration with transmission path loss………………..50
4.4.1 Variation of carrier to noise density ratio with transmission path loss at Ku band… 51
4.4.2 Variation of carrier to noise density Ratio with transmission path loss at K band…. 52
4.4.3 Variation of carrier to noise density ratio with transmission path loss at Ka band… 53
4.5 Modified Link Budget Validation Results……………………………………………………….. 53
4.6 Conclusion…………………………………………………………………………………………………..56
CHAPTER FIVE:CONCLUSION AND RECOMMENDATION
5.1 Introduction………………………………………………………………………………………………………58
5.2 Conclusion ……………………………………………………………………………………………………….58
5.3 Recommendations for Further Work…………………………………………………………………….59
References……………………………………………………………………………………………………………..60
Appendix……………………………………………………………………………………………………………….64

 

Project Topics

 

CHAPTER ONE

 

INTRODUCTION
1.1 BACKGROUND
In recent years, low earth orbit (LEO) satellites have been employed to carry signals for large population of simultaneous users in mobile satellite communication systems over communication link. LEO satellites have very wide scientific applications such as but not limited to; remote sensing of oceans, analyses of Earth’s climate change, Earth’s imagery with high resolution and astronomical purposes. Low earth orbit satellites are also used for data relay and navigation as well as low-cost store-and-forward communications systems. This technology is currently being used for communicating with mobile terminals and with personal terminals that need stronger signals to function. Examples of satellite networks in this orbit include Iridium system with sixty six (66) satellites and Globalstar system’s forty eight (48) satellites (Ray, 2000).
The low earth orbit is located at a height range of 106 – 2000km above the earth surface (Qingchong, 1999) as shown in Figure 1.1. The speed of LEO satellites is high, with a very negligible round trip delay of about 10-20 ms and its orbital period is about 100 minutes(Raymond, 1996). Each LEO satellite is only visible from the earth for about 10 to 20 minutes. Communications between two earth stations typically will involve handing off the signal from one satellite to another. The low earth orbit have attracted the most attention because of technical advantages and the novelty of having many satellites, hand-offs and a cellular-like configuration (Jamalipour, 1997).
2
Figure 1.1: LEO, MEO and GEO Satellite Orbits (Adria, 2010)
The advantages of Low earth Orbit (LEO) include small propagation loss which allows mobile users to use handsets for direct communication, and a small propagation delay (about 10ms compared to 250ms for Geostationary satellite (GEOS)) for better voice performance, and other interactive services. The technical characteristics of satellite orbits are shown in Table 1.1. In addition, Low Earth Orbiting (LEO) Satellites do not suffer from consistent low elevation angles at high altitudes and the associated propagation that Geostationary (GEO) satellites do rather, with proper inclinations, LEO can cover high latitude locations, including polar areas, which cannot be reached by GEO satellites (Raymond, 1996).
Table 1.1: Technical Characteristics of Satellite Orbits (Ogundele, 2010)
S/N
Low Earth Orbit (LEO)
Medium Earth Orbit (MEO)
Geostationary orbit (GEO)
1
Altitude: less than 2000 km above the Earth’s surface in a circular orbit.
Altitude: Located 8,000 to 24,000 km (5k to 15k miles) above the Earth’s surface in circular orbit.
Altitude: Located 35,786 km (22,236 miles) above the Earth’s equator in a circular orbit
2
Most LEO constellations have a circular orbit, which is inclined from the equator, up to polarorbit (90° inclination). Multiple inclinations used.
Most MEO constellations are inclined from the equator, up to polar orbit (90° inclination). Multiple inclination planes are often used.
3
Orbital velocity: ~28,080 km/hr (17,448 miles/hr).
Orbital velocity: ~18,000 km/hr (11,184 miles/hr).
Orbital velocity: 11,066 km/hr (6,876 miles/hour).
One orbital period: 90 minutes to 3 hours
One orbit: 6 to 14 hours, depending on altitude.
One orbit: 23hr 56min 4sec (= Earth’s rotation).
3
4
Angular separation: 30° to 60°, depending on number of LEOs in each inclined plane
Angular separation: ~ 2° (1,476 km; 920 miles).
5
Visible time with Earth Station: 10 to 20 minutes
Visible time with Earth Station: 75 to 8 hours depending on latitude
Visible time with Earth Station: 24 hours.
6
Service life expectancy: 5 to 8 years
Service life expectancy: Longer then LEOs, but less then GEO satellites.
Service life expectancy: 15 yrs or more.
The major disadvantages of the LEO orbit are; more satellites are required, there is increased probability of atmospheric drag, phase error and Doppler frequency shift.
The Doppler frequency shift poses the problem of receiving higher or lower frequencies than the original transmitted frequency. It is defined as the rate of change in signal phase over time relative to the receiver (Jamalipour, 1997). The concept of Doppler frequency shift is applicable to the land mobile radio, including digital cellular transmission link. Here, the cause of Doppler effect could be due to the movement of a mobile unit or natural and constructed obstacles. Natural calamities like torrential rains, raging storms, heavy snowfall e.t.c also cause significant Doppler effect in wireless communication (Kausik et. al, 2007).
In a LEO satellite system, Doppler shift can be introduced in the both uplink and downlink reasons being that if not accounted for during link budget, this Doppler effect can cause serious degradation of demodulation performance and frequent failure of radio link. (Jamalipour, 1997).
1.2 MOTIVATION OF RESEARCH
Effect of Doppler shift on satellite link budget is assumed negligible in conventional approach thereby resulting in the design of an unrealistic link budget, particularly in Low earth orbit (LEO) where it is more pronounced. The prime motivation of this research work is to give an insight on the effect of Doppler on satellite link budget in LEOby first elucidating its adverse nature and then accounting for the losses thereof via a better link design.
1.3 SIGNIFICANCE OF RESEARCH
Doppler shift is defined as the change in frequencies of a wave (signal) as a result of a relative movement between the source of the signal and the object (satellite or receiver). In satellite communication system, this phenomenon constitutes the problem of signal loss.Conventional Satellite Link budget design which is a key ingredient for effective communication between the satellite and the earth terminal did not take into consideration the effect of Doppler shift particularly in Low earth orbit (LEO) where it is more pronounced.In view of this, a more reliable approach to the estimation of
4
satellite link budget at Ku, K, and Ka bands by the inclusion of Doppler frequency shift effect was investigated and the effect of Doppler shift with respect to the position of the orbiting satellite and earth’s terminal was also critically examined.
1.4 STATEMENT OF PROBLEM
The determination of the satellite link budget is made very complex by orbit perturbations which the satellite experiences as it travels along its track. These perturbations include atmospheric drag and Doppler frequency shift. If these problems are not accounted for during link budget, they can cause serious degradation of the signal propagating on the transmission link which may eventually lead to the link failure. Despite the extensive work done in the prediction and analysis of mobile satellite link, the links are still unreliable due to shift in frequencies caused by motion of transmitter receiver or both, particularly in the Low Earth Orbit where Doppler effect is significant.
The conventional approach used in the link budget analysis as described in the literatures reported herein was not representative enough to achieve a robust communication link design for LEO because of the omission of signal impairment due to Doppler frequency shift.
Furthermore, to the best of my knowledge, there has not been a scientific justification as to why the Doppler effect was not considered or included in link budgeting especially, for satellite in LEO orbit. This research work therefore presents an improved LEO-based link budget for land mobile satellite communication by taking into account losses due to Doppler frequency shift on both uplink and downlink paths by considering its effect on the range of earth’s terminal and on carrier to noise density ratio.
1.5 AIM AND OBJECTIVES
This research is aimed atdeveloping a Modified Link Budget for Low Earth Orbiting (LEO)-Based Land Mobile Satellite Communications System operating at Ku, K and Ka frequency bands by considering the effects of Doppler frequency shift centered on the following objectives:
i. To develop a more reliable analytical approach to the estimation of satellite link budget by inclusion of Doppler frequency shift in the conventional link budget model.
ii. To carry out quantitative analysis of the effect of Doppler frequencyshift at higher microwave frequency bands ( Ku, K and Ka bands) in LEO, MEO and GEO with focus on its severity and the effect of earth’s terminal location on the Doppler frequency shift in relation to the position of satellite in LEO.
iii. Need to validate the results
5
1.6 METHODOLOGY
i. Selection of carrier frequency, satellite transmitter power and methods of modulation and demodulation.
ii. Development of a mathematical model of Doppler frequency shift.
iii. Development of a modified model of a satellite link budget by including Doppler effect.
iv. Simulation of the modified link budget at Ku, K and Ka bands using MATLAB R 2014a version.
v. Comparison between the simulated results obtained for both modified and conventional link budgets at Ku, K and Ka bands.
vi. Validation using comparative analysis
1.7 DISSERTATION ORGANIZATION
The general introduction has been presented in chapter one.The rest of the research work is organized as follows; Fundamental concepts pertinent to the design of a satellite link budget in the Low Earth Orbit (LEO) and a critical review of published similar research works is provided in the next chapter.Chapter three presents the procedures as well as an in-depth analysis leading to a more reliable approach to satellite link budget estimation. Comparison between the link budget modeled with Doppler effect and the conventional link budget analysis without the Doppler effect is also made in this chapter. Chapter four focuses on the interpretation of the results based on the analyses presented in the chapter three. Chapter five contains conclusions, significant contributions, limitations and recommendations for future work. Quoted references and appendices are provided at the end of the dissertation report

GET THE COMPLETE PROJECT»
Do you need help? Talk to us right now: (+234) 08060082010, 08107932631, 08157509410 (Call/WhatsApp). Email: edustoreng@gmail.com

DISCLAIMER:This is a complete project material for students and should NOT be copied verbatim, which is Plagiarism. Only use as a guide in developing your original research work. Call/Whatsapp us if you need our help: (+234) 08060082010, 08107932631, 08157509410. Email: Edustoreng@gmail.com