Downlink signal evaluation of haps m 55 aircraft above malaysian skies

386 views

Published on

0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total views
386
On SlideShare
0
From Embeds
0
Number of Embeds
1
Actions
Shares
0
Downloads
7
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

Downlink signal evaluation of haps m 55 aircraft above malaysian skies

  1. 1. International Journal of Electronics and Communication Engineering & TechnologyAND INTERNATIONAL JOURNAL OF ELECTRONICS (IJECET), ISSN 0976COMMUNICATION ENGINEERING &2,TECHNOLOGY (IJECET) – 6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue July-September (2012), © IAEMEISSN 0976 – 6464(Print)ISSN 0976 – 6472(Online)Volume 3, Issue 2, July- September (2012), pp. 336-345 IJECET© IAEME: www.iaeme.com/ijecet.htmlJournal Impact Factor (2012): 3.5930 (Calculated by GISI) ©IAEMEwww.jifactor.com DOWNLINK SIGNAL EVALUATION OF HAPS M-55 AIRCRAFT ABOVE MALAYSIAN SKIES Wanis A Hasan and Ahmad N Abdulfattah Communication Engineering Department, Higher and Intermediate Institute of Comprehensive Professions, P.O. Box 0283-11, Bani Walid, +218, Libya, 0917329250, algazalat@yahoo.com Communication and Computer Engineering Department, CIHAN University, P.O. Box 0383-23, Erbil, Kurdistan Region, +964, Iraq, 07701606662, msc.ahmedaldabbagh@gmail.com ABSTRACT HAPS is a promising technology, uses airborne ships for providing narrow and broadband wireless communication and broadcasting services from the sky to users and end terminals on the ground. It is considered as the most viable and cost-effective solution for communication service providers by complementing their existing terrestrial and satellite network investments, to allow their customers have more freedom and convenience to get connected to different communication networks nationwide and worldwide. Malaysia has made significant efforts in the research of HAPS M-55 aircraft deployment and applications in cooperation with some international partners. In this paper, the downlink signal of HAPS M- 55 aircraft will be evaluated within two different reception scenarios in terms of rain attenuation and signal multipath fading, while hovering above Malaysian skies. Racian channel will be introduced as a multipath fading channel. All results will be obtained based on theoretical assumptions and settings and by using the MATHLAB as a simulation tool. 336
  2. 2. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 2, July-September (2012), © IAEMEKEYWORDS: HAPS M-55 aircraft, elevation angle, radio link budget calculation, rainattenuation, signal multipath fading, Racian fading channel.I. INTRODUCTIONThe necessity of finding a reliable wireless communication infrastructure, which can ensurehigh quality of service (QoS) and meet the customers’ communication needs in Malaysia, hasshifted the attention to search deeply in HAPS technology and applications [1],[2]. In 2007,the mile stone was created when the federal government of Malaysia signed an agreementwith QucomHaps Co. of Ireland and the Russian owner and designer of M-55 GNstratospheric aircraft. That agreement aims to fly the M-55 aircraft above the Malaysian skiesto provide a nationwide wireless access to a broadband connectivity at subscription rateslower than anything commercially offered in the local competitive market [1], [2]. Fig.1. Several communication services provided by a HAPS M-55-based systemHAPS M-55 is a piloted aircraft manufactured and developed by the Geoscan InternationalAgency (GIA) projects [1]. It is designed to fly at the Stratosphere layer and lasts for aboutfive-hour-time interval for each flight. It hovers in a circular path at an altitude of nearly 21 337
  3. 3. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 2, July-September (2012), © IAEMEkm high. It has a body weights approximately 24 tons and 37m wingspan long. It canaccommodate carriage of payloads of 2 tons and consumes power supply of 40kW. It is asingle-seated aircraft and can operate at day and night time, even in critical weatherconditions while taking off or landing statuses as stated in. A single M-55 aircraft can formground coverage of about 400 km radius. This coverage is equivalent to approximately 258ground terrestrial base stations coverage. It is supposed that only five M-55 aircrafts will belaunched and flown concurrently to provide wireless broadband coverage for the entireMalaysian territory [1],[2].II.SCENARIOS AND ASSUMPTIONSThe downlink signal of HAPS M-55 aircraft (service signal) will be evaluated based on twodifferent reception scenarios in terms of rain attenuation and signal multipath fading. It isassumed that the HAPS M-55 aircraft will be flown at an altitude of 21 km above Johor state,which is a part of Malaysian territory. The elevation angle of downlink signal reception willbe a vital parameter in both scenarios.Scenario I: two users (uA and uB) receive the downlink signals with 20o and 90o elevationangles respectively. That is to evaluate the downlink signal level when one user is at the endof coverage whereas the other is in the center. 20o was chosen as the lowest elevation angle,at which the user is supposed to receive the downlink signal with the lowest quality. If thelowest elevation angle is assumed, the larger the service coverage can be formed, but the rainpropagation path, however, becomes longer and larger fade margin may be needed [3]. Also90o was also chosen as the highest elevation angle, at which the user centralizes directlyunder the Sub-Platform Point (SPP), and can receive the downlink signal with better quality[3]. Communication links of the downlink signals received by both users are considered Line-of-Sight (LOS) paths. While travelling between the HAPS M-55 aircraft and the two users, itis assumed that those signals will experience a rainfall event (rainy sky weather condition).Just for a comparison purpose, they will be first evaluated under clear sky weather condition.Settings of the two users were calculated and inserted in Table (1) as below: 338
  4. 4. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 2, July-September (2012), © IAEME Table (1) Settings of the two users (uA & uB) Elevation Altitude Distance Propagation Total Antenna Feeder angle (m) to SPP path length signal gain Loss (Degree) (km) (km) path No. (dBi) (dB)uA 20` 25 57.70 61.39 1 28 0.7uB 90 25 0 21 1 28 0.7 Fig.2. Two users receive HAPS M-55 downlink signal with 20o and 90o elevation anglesOperational parameters of HAPS M-55 aircraft were assumed for both downlink signalswhile travelling under a clear sky condition and inserted in Table (2) as below: 339
  5. 5. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 2, July-September (2012), © IAEME Table (2) Operational parameters of HAPS M-55 aircraft Parameter Downlink Elevation angle (degrees) 20 90 Altitude (Km) 21 21 Frequency (GHz) 28 28 Data Rate (Mbit/s) 2 2 Modulation Scheme QPSK QPSK Output power (dBW) -12.1 -13.2 Feeder loss (dB) 0.7 0.7 Gain (dBi) 26.6 18.3 EIRP (dBW) 13.8 4.4 Propagation path length (Km) 61.93 21 Free space loss (dB) 157.1 147.7 Atmospheric gas loss (dB) 0.4 0.4 Rain attenuation (dB) 0 0In order to evaluate the downlink signal under a rainy sky condition, data of rainfall rate ofJohor was collected and used to predict the overall rain attenuation based on [4], [5], [6] asshown in Table (3) below: Table (3) Rain attenuation predicted in Johor State Elevation angle Service reliability Rain rate Rain attenuation predicted (degree) (%) (mm/h) (dB) 20 103.6 99 120.35 90 13The equation, which is used in the calculations, is the basic simplified received signal powerequation as shown below [4]: P୰ = P୲ − L୤ୣୣୢୣ୰ + G୲ − L୤ୱ୪ − L୥ୟୱ − L୰ୟ୧୬ + G୰ − L୤ୣୣୢୣ୰ (1)Where: 340
  6. 6. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 2, July-September (2012), © IAEMEP୰ : Downlink received signal power (dBW)P୲ : Transmitted signal power (dBW)L୤ୣୣୢୣ୰ : Transmitted signal power loss because of feeder inefficiency (dB).G୲ : Transmitting antenna gain (dBi)L୤ୱ୪ : Free space loss (dB)L୥ୟୱ : Power loss because of Atmospheric gas (dB).L୰ୟ୧୬ : Rain attenuation loss (dB)G୰ : Receiving antenna gain (dBi)L୤ୣୣୢୣ୰ : Received power loss because of feeder inefficiency (dB).Scenario II: only one user, uA, receives the downlink signal through direct and diffusepropagation paths due to the nature of vicinity. It is assumed that one Line-of-Sight path(LOS) and five delayed paths (NLOS) will be absorbed by the uA’s antenna. In this scenario,the downlink signal which is received by the uB will be ignored, because it is supposed tohave only one Line-of-Sight path (direct path) [3], [7]. The vicinity of the user, uA, includesmany clutters and obstructions whose locations relative to the user uA will determine the timedelay length the diffuse downlink signal may experience [7], [8], [9]. It is known that themost delayed path will travel the longest distance from the HAPS M-55 aircraft to the uA andthe vise-versa. For this purpose, the time delay of the five paths will be set based on into twoassumptions; assuMax specifies the maximum time delay of the last diffuse path (the fifthdelayed path) does not exceed the time duration of the transmitted symbol, and the maximumrange of the surrounding clutter is less than 300 m. Also assuMin specifies that the minimumtime delay of the first diffuse path (the first delayed path) is longer than the time duration ofthe transmitted symbol, and the minimum range of surrounding clutter is more than 300 m.This scenario will focus on the multipath effects on the downlink signal based on thismanner, and by using the Racian multipath fading channel [2], [8], [10], [11], [12]. Settingsused for the user, uA, in this scenario are shown in Table (4) as below: 341
  7. 7. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 2, July-September (2012), © IAEME Table (4) Settings of the user, uA Coverage area Propagation Total signal path User speed Max Doppler shift K-Factor environment No. (m/s) (Hz) Suburban Outdoor 6 1.3 121.3 4 III. RESULTS AND DISCUSSION• Downlink signal level The downlink signal was simulated under two different weather conditions (clear & rainy) and plotted in Fig.3. as shown below: Fig.3. Downlink signal versus elevation angle of reception It is observed that the downlink signal level varies as a function of the elevation angle of reception and the weather condition. In other words, its level drops while a rainfall event is taking place, especially when the elevation angle of reception decreases. uA will only enjoy the same downlink signal level as the uB does when the sky is clear, but will not do during the rainfall events; regardless their downlink signals experience the same rainfall rate.• Downlink signal experienceThe downlink signal was simulated based on the assuMax multipath assumption and plottedin Fig.4. as shown below: 342
  8. 8. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 2, July-September (2012), © IAEME Fig.4. Magnitude of downlink signal versus time delay and frequencyIt is noticed that the downlink signal received by the user, uA experiences a frequency-flatfading, caused due to the time dispersion phenomena. The scattering and reflection of thedownlink signal on the surfaces and edges of the clutters, which are located at not farther than300 m from the user, uA, produced several replicas of the downlink signal. Those replicaswere delayed and received at irresolvable time points within the time duration of the directreceived symbol. It seen that the five delayed components combine and get clustered atapproximately the time zero second as shown in Fig.4.Also the downlink signal was simulated based on the assuMin multipath assumption andplotted in Fig.5. as shown below: 343
  9. 9. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 2, July-September (2012), © IAEME Fig.5. Magnitude of downlink signal vs. time delay and frequencyIt is seen in this time that the downlink signal received by the user, uA experiences afrequency-selective fading, resulted from the delayed signals which were received randomlyat different time points higher than time duration of the direct received symbol. It is clear thatthe five delayed components are aligned to the time line relative to their locations (atdistances farther than 300 m) to the user, uA as shown in Fig.5.IV. CONCLUSIONIt can be concluded that the downlink signal of the HAPS M-55 aircraft (service signal) maybe affected by several propagation impairments such as the rain attenuation, especially inMalaysia, where the rainfall events are dominant weather conditions along the year. Also thesignal multipath fading is a matter of importance that can affect the downlink signal leveleither with flat or selective fading unless proper fade mitigation techniques (FMTs) areapplied. 344
  10. 10. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 2, July-September (2012), © IAEMEV. REFERENCES1. GEOSCAN (UK) Plc., et al. (2004), “project profile”, Moscow, Russia2. Alejandro .A.Z., et. al. (2008), “High-Altitude Platforms for Wireless Communications”,1st ed, John Wiley & Sons Ltd, Chichester, UK,3. International Telecommunication Union (2002), “Technical and operational characteristicsfor the fixed service using high altitude platform stations in the bands 27.5-28.35 GHz and31-31.3 GHz,” Rec. ITU-R F.1569, Geneva, Switzerland4. Wanis .A.H. (2010), “Evaluation of potential interference and rain effects on 21.4-22 GHzdownlink broadcasting satellite signal in Malaysia,” Johor, Malaysia5. Cheblil .J (1997) “Rain rate and rain attenuation distribution for Microwave study inMalaysia,” Johor, Malaysia6. International Telecommunication Union (2007), “Propagation Data and PredictionMethods Required for the Design of Earth-Space Telecommunications Systems,” Rec. ITU-RP.618-9, Geneva, Switzerland7. José .L. C., et. al. “Channel Modeling and Simulation in HAPS Systems,” Catalonia, Spain8. Fabio .D., et. al. (2002), “Small-Scale Fading for High-Altitude Platform (HAP)Propagation Channels,” IEEE Journal on Selected Areas in Communications, vol. 20, No. 3,April 20029. International Telecommunication Union (2012), “Propagation data required for the designof Earth-space aeronautical mobile telecommunication systems,” Geneva, Switzerland10. Vogel, W. J. and J. Goldhirsh (1995), “Multipath Fading at L-Band for Low ElevationAngle, Land Mobile Satellite Scenarios,” IEEE Journal on Selected Areas inCommunications, Vol. 13, No. 2, February 199511. International Telecommunication Union (2001), “Propagation data required for the designof Earth-space land mobile telecommunication systems,” ITU-R P.682-3, Geneva,Switzerland12. Fernando U-V. and Delgado-P, “Performance simulation in high altitude platforms(HAPS) communications systems,” Catalonia, Spain 345

×