The study investigates the effect of propagation impairments such as rain, cloud, gases

and tropospheric scintillation on fixed satellite communication link on earth-space path for

frequencies between 10 and 50 GHz at Ku, Ka and V bands for 37 locations in Nigeria. Two

standard elevation angles of 50, 550 as well as some elevation angles for links to recently

launched Nigeria Communication Satellite, (NigComsat-1) were used in the computation of the

propagation impairments for the 37 locations. Linearly and circularly polarized waves were

considered. The International Telecommunication Union Radiowave Propagation models (ITURP) were used in the investigation of the propagation impairments. The study is divided into three parts; firstly, the collection and analysis of meteorological data from Tropical Rain

Measurement Mission (TRMM) and Atmospheric Infrared Sounder (AIRS) satellites such as rain accumulation, profiles of temperature, pressure, and relative humidity, surface temperature and pressure were validated with the available ground data in Nigeria to form statistics on monthly and annual basis. These are reprocessed to derive propagation parameters, such as; one-minute rainfall rate, water vapour density, total cloud liquid water content, and integrated water vapour content. Secondly, an appropriate ITU-RP propagation model was selected for each of the propagation impairment and was used to calculate each attenuation distribution for a percentage of time unavailability. Thirdly, the attenuation due to all impairments were combined based on the annual cumulative distribution and percentage of time unavailability between 0.01 to 10%. The calculation of the propagation parameters are based on the measured mean annual data in each location for the period of 4 to 9 years. Propagation impairments were also computed at Ku, Ka and V bands for links to NigComsat-1 at 0.01 to 10% of time unavailability in an average year. The results of all impairment were compared on regional basis by using a colour chart for all the 37 locations in Nigeria. The results of the predicted propagation impairments are as follows: rain attenuation is highly severe in Abakaliki the South-East (SE) region followed, in descending order, by Yenagoa the South-South (SS), Ibadan South-West (SW), Jos Middle-Belt (MB), Damaturu North-East (NE), and Kastina North-West (NW) regions. Cloud attenuation is highly severe in Abakaliki the SE region followed, in descending order, by Jos (MB), Gombe (NE), Dutse (NW), Ikeja (SW), and Calabar (SS) regions. Gaseous attenuation is highly severe in Calabar the (SS regions) followed, in descending order, by Ikeja (SW), Abakaliki (SE), Abuja(MB), Dutse the (NE) and Kastina (NW) regions. Tropospheric scintillation is very high in Calabar (the SS region) followed, in descending order, by Ikeja (SW), Owerri (SE), Abuja (MB), Dutse (NE) and Kastina (NW) regions. Combined impairments due to multiple sources of simultaneously occurring atmospheric attenuation is highly severe in Abakaliki the (SE region)

followed, in descending order, by Uyo (SS), Ikeja the (SW), Markudi (MB), Maiduguri (NE) and Katsina (NW) regions. For links to NigComsat-1 the combined impairments due to multiple sources of simultaneously occurring atmospheric attenuation is highly severe in Yenagoa the (SS region ) followed, in descending order, by Owerri (SE), Ibadan (SW), Jos (MB), Damaturu the (NE), and Katsina (NW) regions. Overall, Sokoto and Katsina appear as good locations to site fixed satellite earth stations (operating at Ku band and above) for deep space exploration as the results obtained showed consistently that the two locations are less affected by all propagation impairments investigated.

Certification ii

Dedication iii

Acknowledgements iv

Table of contents v

List of Figures x

List of Tables xii

Abstract xvi

11 Introduction 1

12 Statement of the Problem 2

13 Rationale for the study 3

14 Aim and Objectives of the study 4

21 Scattering and Absorption by Single Particles 6

211 Cross section and Scattering Amplitude 7

22 Propagation Impairment Mechanisms 8

23 Impairment by Rain 9

231 Characteristics of rainfall in tropical region 9

232 Types of Cloud 10

233 Stratiform and Convective Rain 12

234 Raindrop size and shape 13

235 Raindrop size distribution models 14

236 Models of Rain Attenuation Statistics 16

237 Methods of rain attenuation measurements 18

238 Rain Data Source 19

239 Processing of Rain Data 20

240 Computer program to compute one minute rainfall rate 21

241 Station height above mean sea Level 21

242 00C Isotherm height and Rain height 22

243 Calculation of long-term rain attenuation statistics from point rainfall rate 24

244 Empirical scaling formula 27

245 Some Geometrical Parameters Relevant to the Study of Rain Attenuation at

Selected 37 stations in Nigeria 27

251 Impairment by Clouds 29

252 Cloud Data sources 30

253 Cloud Data processing 31

254 Procedure for evaluation of SVD, TCC and IWVC 31

255 Surface Water Vapour Density, � (SVD) 31

25 6 Total columnar content of liquid water in clouds (TCC) 32

257 Integrated Water Vapour Content (IWVC) 33

258 Computer Program to Evaluate SVD, TCC and IWVC 34

259 Procedure for Evaluation of Cloud Attenuation 36

2591 Specific Cloud attenuation coefficient 36

2592 Computer Program for Attenuation due to Cloud 37

26 Impairment by Atmospheric Gases 38

261 Gaseous Specific Attenuation 39

262 Input Data sources for Gaseous Attenuation 39

263 Procedure for the Computation of Gaseous Attenuation 41

264 Gaseous Attenuation along Slant Paths 44

265 Computer program for evaluating evaluate gaseous attenuation 46

27 Tropospheric Scintillation 47

271 Amplitude Scintillation Prediction Models 47

272 Input Data Sources for Evaluation of Tropospheric Scintillation 48

273 Procedure for evaluating the input parameters 49

274 Calculation of monthly and long-term statistics of amplitude

Scintillations at elevation angles greater than 4° 49

275 Computer program for the Evaluation of Tropospheric Scintillation 51

28 Methods of Combining Propagation impairments 54

281 Combination of Different Attenuation Effects 54

282 Equiprobability Summing 54

283 Convolution method 54

284 Disjoint summing 55

285 Root-sum-square addition 55

286 Coherent summing 56

287 Prediction of Combined Propagation Effects 56

288 Estimation of Total Attenuation due to Multiple Sources of Simultaneously

Occurring Atmospheric Attenuation 57

30 Validation of TRMM Data with Measured Rainguage data in Nigeria 59

31 Nine-year Results of Rain Events as Recorded by TRMM Satellite at

37-Locations in Nigeria 62

311 Year to Year Variation of the derived one-minute Rain rate from TRMM Data 65

312 Cumulative Distribution of Rainfall rates in Six regions 68

313 Comparison with Other Works 69

32 Results of Rain Attenuation 73

321 Rain Attenuation at Ku, Ka and V-Bands for Horizontally polarized Wave Unavailability

for 001% in an Average year at the 37-locations in Nigeria 76

322 Application of Rain Attenuation to NigComSat-1 at Ku and Ka for 001-1%

unavailability at the 37-Locations in Nigeria 80

323 Rain Attenuation Results for Links to NigComSat-1 at Ku, Ka and V Downlink

Frequencies for a VSAT at 001 to 10% Unavailability of an Average at the 37-

locations in Nigeria 82

33 Results of Cloud attenuations for 1% Unavailability of an Average Year 87

331 Cloud Attenuations Results at Ku, Ka and V bands for 1% Unavailability of an

Average Year at the 37 Locations in Nigeria 90

332 Cloud Attenuation for Links to NigComSat-1 at Ku, Ka and V-band for

001-10% Unavailability of an Average Year 93

34 Gaseous Attenuation for 1% unavailability of an average year at the 37 Locations

In Nigeria 97

341 Gaseous Attenuations at Ku, Ka and V bands for 1% Unavailability of an Average

Year at the 37 Locations in Nigeria 100

342 Gaseous Attenuation for Links to NigComSat-1 at Ku Ka, and V-bands for

1% Unavailability of an Average at the 37-locations in Nigeria 103

35 Scintillation Fade depth for 001% unavailability at 50 and 550 for the 37-Locations in Nigeria 105

351 Scintillation Fade Depth for the 001% Unavailability at Ku, Ka and V-band at the 37 locations in Nigeria 108

352 Scintillation Fade Depth for Links to NigComSat-1 at Ku and Ka for 001 - 10% Unavailability of an Average at the 37-locations in Nigeria 111

36 Combined Attenuation for 001% Unavailability of an Average Year for Frequencies 10 to 50 GHz at the 37-Locations in Nigeria 115

361 Combined Attenuation at Ku, Ka and V-bands for 001% unavailability in an Average Year at the 37 Locations in Nigeria 118

362 Combined Attenuation at Ku, Ka and V-bands for Downlinks from NigComsat-1 at the 37 Locations in Nigeria from 001 to 10% Unavailability in an Average Year 121

411 Rain Attenuation at frequencies between 10 to 50 GHz 129

412 Rain Attenuation Study at Links to NigComSat-1 at Ku and Ka from 001-1%

Unavailability of an Average Year 129

42 Cloud Attenuation at frequencies between 10 to 50 GHz 130

421 Cloud Attenuation Study for Links to NigComSat-1 at Ku and Ka from 001-1%

Unavailability of an Average Year 130

43 Gaseous Attenuation Study at 1% unavailability for frequencies between

10 to 50 GHz 130

431 Gaseous Attenuation Study for Links to NigComSat-1 at Ku and Ka for 1%

Unavailability of an Average year at the 37 locations 130

44 Tropospheric Scintillations Study at 001% unavailability of an Average

Year for Frequencies 10-50GHz at the 37 Locations in Nigeria 130

441 Scintillation fades depth Study for Links to NigComSat-1 at Ku and Ka for

001 to 10% Unavailability of an Average at the 37-locations 131

45 Combined Attenuation Study at 001% Unavailability of an

Average Year for Frequencies between 10 to 50 GHz 131

451 Results of Combined Attenuation Study at Ku, Ka and V-bands for Downlinks

from NigComsat-1 for 001 to 10% Unavailability in an Average Year at the

37-Locations in Nigeria 131

46 Conclusions and Recommendations 132

11 Map of Nigeria showing the 37 stations used in the study 5

21 Illustrating a single Scattering process 7

22 Types of Cloud 10

23 The Ten Basic Cloud Types 12

24 Raindrop size and shape 14

25 Schematic presentation of an Earth-space path giving the parameters to be input into the attenuation prediction process 24

26 Illustration of the A-Train Satellites 31

31 Cumulative Distribution of Rainfall rates for the 37-locations in Nigeria 68

3 2 Rain Attenuation in Nigeria for 001% unavailability of an Average Year for Horizontal polarization at 50 elevation 74

33 Rain Attenuation in Nigeria for 001% unavailability of an Average Year for Horizontal polarization at 550 elevation 75

34 Rain Attenuation Cumulative distribution for links to NigComsat-1 at Ku�band (11GHz) 84

35 Rain Attenuation Cumulative distribution for links to NigComsat-1 at Ka�band (20GHz) 85

36 Rain Attenuation Cumulative distribution for links to NigComsat-1 At V�band (40GHz) 86

37 Cloud Attenuation at the 37 locations for 1% of an Average Year at 50 elevation 88

38 Cloud Attenuation at the 37 locations for 1% of an Average Year at 550 elevation 89

39 Cloud Attenuation Cumulative distribution at Ku (11GHz) downlink Frequency from NigComsat-1 for the 37 locations 94

391 Cloud Attenuation Cumulative distribution at Ka (20GHz) downlink Frequency from NigComsat-1 for the 37 locations 95

392 Cloud Attenuation Cumulative distribution at V (40GHz) downlink Frequency from NigComsat-1 for the 37 locations 96

310 Gaseous Attenuation at the 37 location in Nigeria for 1% Unavailability at 50 Elevation 98

311 Gaseous Attenuation at the 37 location in Nigeria for 1% Unavailability at 550 Elevation 99

312 Tropospheric Scintillation in Nigeria for 001% Unavailability of an Average year at 50 Elevation 106

313 Tropospheric Scintillation in Nigeria for 001% Unavailability of an Average year at 550 Elevation 107

314 Tropospheric Scintillation Cumulative distribution at Ku (11GHz) downlink Frequency from NigComsat-1 for the 37 locations 112

315 Tropospheric Scintillation Cumulative distribution at Ka (20GHz) downlink Frequency from NigComsat-1 for the 37 locations 113

316 Tropospheric Scintillation Cumulative distribution at V (40GHz) downlink Frequency from NigComsat-1 for the 37 locations 114

317 Combined Attenuation due to Cloud, Gases, Scintillation and Rain in Nigeria for Horizontal Polarization at 50 elevation 116

318 Combined Attenuation due to Cloud, Gases, Scintillation and Rain in Nigeria

for Horizontal Polarization at 550 elevation 117

319 Combined Attenuation due to Rain, Cloud, Scintillation and Gases at Ku (11GHz) for links to NigComsat-1 122

320 Combined Attenuation due to Rain, Cloud, Scintillation and Gases at Ka (20GHz) for links to NigComsat-1 123

321 Combined Attenuation due to Rain, Cloud, Scintillation and Gases at V  (40GHz) for links to NigComsat-1 124

11 Frequency Bands used in Satellite Communication 2

20 Particles Responsible for Atmospheric Scattering 6

21 Approximate height ranges at which bases of cloud are found 11

22 List of the input parameters necessary for rain attenuation prediction models 17

23 Topographic data: Heights above Mean sea level (m), Zero degree Isotherm

Height (m) and Rain height (km) for the 37- locations in Nigeria 23

24 Some Geometrical Parameters Relevant to the Study of Rain Attenuation at

5 and 55 degrees elevations for the 37 locations 28

25 Summary of the input Climatic data for Cloud and Gaseous Attenuations

Derived from AIRS Satellite data from AUG 2002-JUL 2006 35

26 Summary of the input Climatic data for Computation of Gaseous Attenuations

Derived from AIRS Satellite data from AUG 2002-JUL 2006 40

27 Summary of Climatic Parameters Needed for the Computation of Tropospheric

Scintillation Derived from AIRS Satellite data, Average value from

Aug 2002- Jul 2006 52

28 Geometrical Parameters Relevant to Scintillation Fade Depth for Downlink

from NigSatcom-1 for the 37-locations 53

31 The Seasonal Variation of Mean Precipitation, Percentage Mean Bias Error and

Overall Correlation Coefficients 61

31b Comparison of the 3-yr mean seasonal rainfall (mm/month) of this work with

other climatic regions in Africa 62

32 Summary of Rain Events in Nigeria derived from TRMM 3B43V6 data

January 1998-December 2006 64

33 Year to Year Variations of One-minute Rainfall rates (in mm/h) Exceeded for

001% of an Average Year Derived from TRMM 3B43V6 Satellite Data:

January 1998 to December 2006 66

34 Statistical Summary of One-minute Derived Rainfall rates Exceeded for 001%

of an Average Year from TRMM 3B43V6 Data: Jan 1998-Dec 2006 67

35 Correlation of the Derived One-minute Rainfall rates with Other Works 70

35b Measured One-minute Rainfall rates for Tropical and Subtropical Locations

around the World Compared with some Tropical and Subtropical Stations in

Nigeria for the Present study 72

36 Calculated Attenuation due to Rain at 5 degrees Elevation for Ku, Ka and

V bands Uplink and Down link Frequencies for Horizontal Polarization for

the State Capitals in Nigeria 78

37 Calculated Attenuation due to Rain at 55 degree Elevations for Ku, Ka and

V bands Uplink and Down link Frequencies for Horizontal Polarization in

the State Capitals in Nigeria 79

38 Some Geometrical Parameters Relevant to NigComSat-1 at Downlink

Frequencies at Ku, Ka, and Extended to V Bands for Future Communication

 Satellite at 001%Unavailability 81

39 Calculated Attenuation due to Cloud at 50 Elevations for Ku, Ka and V Bands

Uplink and Downlink frequency for the State Capitals in Nigeria 91

391 Calculated Attenuation due to cloud at 55

0 Elevations for Ku, Ka and V Bands

Uplink and Downlink frequency for the State Capitals in Nigeria 92

310 Results of Gaseous Attenuation at 5 degree Elevations for Ku, Ka and V Bands

Uplink and Downlink Frequencies for the 37-Locations in Nigeria 101

311 Results of Gaseous Attenuation at 55 degree Elevations for Ku, Ka and V Bands

Uplink and Downlink frequencies for the 37-Locations in Nigeria 102

312 Gaseous Attenuation relevant to link to NigComSat-1 at 1% unavailability at Ku,

Ka and V Satellite Bands 104

313 Results of Tropospheric Scintillation at 5 Degree Elevation for 001%

Unavailability at Ku, Ka and V Bands, Uplink and Downlink, Frequencies, for

the State Capitals in Nigeria 

314 Results of Tropospheric Scintillation at 55 Degree Elevation for 001%

Unavailability at Ku, Ka and V Bands, Uplink and Downlink, Frequencies, for the State Capitals in Nigeria 110

315 Combined Attenuations due to Cloud, Gas, Rain and Scintillation at 50 Elevations for Ku, Ka and V bands Uplink and Downlink Frequencies for Horizontal Polarization in the State capitals in Nigeria 119

316 Combined Attenuations due to Cloud, Gas, Rain and Scintillation at 55

0 Elevations for Ku, Ka and V bands Uplink and Downlink Frequencies for

Horizontal Polarization in the State capitals in Nigeria 120

317 Combined Attenuations due to Cloud, Gas, Rain and Scintillation at Ku-bands

Downlink from NigComsat-1 for Horizontal Polarization for the State capitals in Nigeria 126

318 Combined Attenuations due to Cloud, Gas, Rain and Scintillation at Ka-bands

Downlink from NigComsat-1 for Horizontal Polarization for the State capitals in Nigeria 127

319 Combined Attenuations due to Cloud, Gas, Rain and Scintillation at V-bands Downlink from NigComsat-1 for Horizontal Polarization for the State capitals in Nigeria 128

41 Summary of all propagation impairments in Nigeria by region from 10-50GHz 132

A1 Results of Rain Attenuation (in dB) for 001 % Unavailability for Vertical Polarization at 5 degree elevation 143

A2 Results of Rain Attenuation (in dB) for 001 % Unavailability for Circular Polarization at 5 degree elevation 144

A3 Results of Rain Attenuation (in dB) for 001 % Unavailability for Vertical Polarization at 55 degree elevation 145

A4 Results of Rain Attenuation (in dB) for 001 % Unavailability for Circular Polarization at 55 degree elevation 146

A5 Results of Rain Attenuation (in dB) for links to NigComsat-1 at 001 % Unavailability for Horizontal Polarization 147

A6 Results of Rain Attenuation (in dB) for links to NigComsat-1 at 001 % Unavailability for Vertical Polarization 148

A7 Results of Rain Attenuation (in dB) for links to NigComsat-1 at 001 % Unavailability for Circular Polarization 149

A8 Matlab 70 Functions for the Computation of Climatic input Parameters Needed for Propagation Studies 150

A9 Matlab 70 Functions for the Computation of Attenuations Due to Rain, Gas, Cloud, Tropospheric Scintillation 151

A10 Matlab 70 Programs for the Computation of Climatic input Parameters Needed for Propagation Studies 152

A11 Matlab 70 Programs for the Computation of Attenuations Due to Rain, Gas, Cloud, Tropospheric Scintillation 155

A12 TRMM Instruments and Flight Characteristics 167

A13 NigComsat-1 Characteristics 170