Mitigating the Effect of Rain Fading on Ka Band High Throughput Satellite in Indonesia: an Empirical Study

INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VOLUME 9, ISSUE 03, MARCH 2020 ISSN 2277-8616

Mitigating The Effect Of Rain Fading On Ka Band High Throughput Satellite In Indonesia: An Empirical Study

Ilvico Sonata, Sandra Octaviani BW, Isdaryanto Iskandar

Abstract— The Indonesian government used fiber optics through the Palapa Ring Project to cover all regions of Indonesia with high-speed internet. Certain areas that cannot be passed by optical fiber will be filled by VSAT Broadband System using High Throughput Satellite. High Throughput Satellite takes advantage of frequency reuse and multiple spot beams to increase throughput and reduce the cost per bit delivered, regardless of spectrum choice. But, with the frequency of Ka band being used by High Throughput Satellie, this will be a disadvantage where Ka band frequency is vulnerable to weather. This Papper studied the effect of rain fading to the VSAT High Throughput Satellite and its mitigation techniques.

Index Terms— adaptive coding and modulation, high throughput satellite, Ka band, Rain fading, site diversity, orbital diversity, uplink power control. ——————————  —————————— 1 INTRODUCTION Rain Attenuation event on Ka Band Satellite Earth Link in High-throughput satellite (HTS) is a classification for Jakarta - Indonesia can be described as follow. communications satellites that provide at least twice, though The time series of a typical rain-induced attenuation event usually by a factor of 20 or more, the total throughput of a recorded simultaneously at 20 and 30 GHz at the Jakarta site classic FSS satellite for the same amount of allocated orbital is shown in Fig. 2. The event, which occurred on 10 December spectrum thus significantly reducing cost-per-bit [3](Fig 1). In 2018, started at 13.20:12 WIB and lasted about 1 hour. the last 10 years, the majority of high-throughput satellites

operated in the Ka Band, however this is not a defining criterion, and at the beginning of 2017 there was at least

10 Ku band HTS satellites projects, of which 4 were already launched and 7 were in construction. Indonesia government will use HTS Nusantara 1 (146o E), SES 12 (95o E), Telstar (138 o E), Intelsat (169o E) and Intelsat (60o E)and future

Nusantara 2 (launch 2022) in which using Ka Band as uplink

operating frequency. In satellite communications, the Ka band

allows higher And width communication. The Ka band is more

susceptible to rain attenuation than the Ku band, which in turn is more susceptible than the C band. The 30/20 GHz band is Event duration (Min) used in communications satellite uplinks in either the 27.5 GHz and 31 GHz band [2]. Fig 2.Rain attenuation Even.

At the peak of the attenuation event the 30 GHz receiver lost track of the signal during several seconds due to the deep fading (Fig 2). In this situation, the design of satellite communication system . must provide suficient system gain to accomodate deep fading (fade margin) to ensure the require quality of service is maintained.

2 SOLUTION 2.1 Uplink Power Control Simplest way to compensite rain fade effect and Increase FIG 1. CONVENTIONAL SATELLITE VS HTS (SOURCE: transmit power at terminal end.But constant transmit with high power result interference and the power amplifier shows a non HTTPS://PSN.CO.ID/NSATU). linear behavior. The output power become limited.

————————————————  Ilvico Sonata is currently pursuing engineer professional certification program in Atma Jaya Catholic University, Indonesia , Jakarta 12920. E-mail: [email protected]  Sandra Octaviani BW is currently Lecturer in telecommunication engineering in Atma Jaya Catholic University, Indonesia, Jakarta

12920. E-mail: [email protected] Modulator Beacon receiver Demodulator  Isdaryanto Iskandar is currently Lecturer in mechanical engineering in Atma Jaya Catholic University, Indonesia, Jakarta 12920. E-mail: [email protected] Uplink Power Control 3315 IJSTR©2020 www.ijstr.org INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VOLUME 9, ISSUE 03, MARCH 2020 ISSN 2277-8616

Fig 3. Uplink power control. 2.3 Diversity Diversity is the technique for increasing availability satellite The beacon signal is reliable and a good beacon receiver can communication with additional another facility. The are two remain locked to the beacon in spite of severe rain fading. types of diversity. Orbital Diversity, by adding one or more The beacon will be a frequency in the downlink band so a orbital satellite. Site diversity, by adding one or more ground calculation of an estimate of the equivalent fade depth at the segment. transmit frequency is required. 2.3.1 Site Diversity Table 1 Site diversity is a method used to minimize the effect of fading Uplink Power Control Even at 10 December 2018 started at due to rain in satellite communication systems, mostly in Ka 13.20:12 WIB and lasted about 1 hour. band. The downlink transmissions of satellites cover large footprints that will have different weather in different regions. Condition Additional Power Up (dB) The site diversity technique consists of connecting two or Clear Sky 0 more terrestrial ground stations receiving the same signal: if Moderate Rain 1-8 the signal to be received is severely affected in one region, Heavy Rain 8-12 Worst Heavy Rain 12-18 other ground stations can accommodate for it. Areas of intense rain for example have super cells, they have a length In TDMA Network, the TDMA Receive modem detect the only few kilometers: while placing the earth stations at a receive burst signal quality from each remote site. The hub sufficient distance that the possibility of fading in the downlink station then tells the remote site to increase or decrease it’s signal path can be minimized. transmit power so as to maintain a nominal adequate quality to the hub. There is some error reported of Uplink power control. When the sky is clear, the power is increase accidently and some large carrier made the transponder saturation. This is Very serious incident.

2.2 Adaptive Coding and Modulation Adaptive coding and modulation (ACM) schemes decrease the required Signal to Noice Ratio (SNR) for achieving a target bit error rate (BER) by reducing the spectral efficiency (in bps/Hz) of the transmitted signal when fading occurs. A satellite system D may switch between higher-order modulation schemes, such Site 2 Site 1 as 16-PSK,16 QAM, 64-PSK, or 254-QAM, under clear sky conditions, and lower-order modulation schemes like BPSK and QPSK under deep fading. Fig 5. Site Diversity.

Simple Empirical Models are used for simulation dual site diversity propose by Hodge [4]:

Site diversity gain: GSD = GD(As)GfGφGψ (1) Dependence of gain Frequency Gf = exp(1-0.025f) (2) . Modulator Beacon Demodulat Dependence of gain Separation Distance receiver or GD = a[1-exp(-bD)] (3) Where: a = 0.78 As -1.94[1-exp(-0.11 As)] (4) ACM Control b= 0.59[1-exp(-0.11 As)] (5) Dependence of gain Base-Line Term Fig 4. ACM Control. Gψ = 1+0.002ψ (6) Dependence of gain elevation Angle Table 2 Gφ = 1+0.006φ (7) Adaptive Coding and Modulation Even at 10 December 2018 started at 13.20:12 WIB and lasted about 1 hour. Where GD , Gf, Gφ and Gψ are respectively the dependence factors of the site-diversity gain on separation distance, D(Km) Condition Modulation Coding between two earth station (Fig 5), the operation frequency, f(Ghz), the common elevation angle, φ(deg), and the Clear Sky 16QAM 7/8 orientation of the baseline relative to the propagation path, Moderate Rain 8PSK 3/4 ψ(deg). As (dB) is the exceed attenuation threshold when the Heavy Rain QPSK 3/4 Worst Heavy Rain BPSK 1/2 link operation without diversity.

2.3.2 Orbital Diversity Orbital diversity reduce fade margin by continuously selecting

(%)

Satellite 1

Satellite 2 Probability ϴ

Fade Margin (dB)

Outage Outage (%)

Fig 7. Single link simulation. Using satellite Telstar (138oE) as a orbital diversity simulation, reduce the required fade margin to 10.6dB. Fig 6. Orbital Diversity. The diversity gain become A similar procedure proposed by Panagopoulus and 18.5 – 10.6=7.9dB. Kanellopoulus [5] for dual orbital diversity:

Ballance diversity gain: BG i = GϴGfGφi , (i=1.2) (8) Where Gϴ is the gain factor depending on the angular separation, ϴ(deg) of the two satellite as seen by the earth station. For unbalanced diversity systems,estimate orbbital diversity gain, GOD, is obtained by adding a correction term ∆G to BG i : GOD = BG i + ∆G (9) The equation become: Probability (%) Outage Gϴ(Asi) = {c i Asi - c2 [1-exp(-c3 Asi)]}{1-exp[-(c4-c5 Fade Margin (db) Asi)ϴ]} (10) c7 Gf = c6f , (11) Fig 8. Orbital Diversity simulation. c9 Gφi = c8φi , (i=1,2), (12) Using site diversity with distance 20km, the diversity gain: c11 c12 ∆G = c10 Asi ∆φf (13) 18.5-4.2 = 14.3dB. When ∆φ(deg) is the difference between the elevation angle, φ1, φ2 of the two satellite, ci(i=1,2,....,12) is climatic zone (P for Jakarta, Indonesia).

3 DESIGN AND SIMULATION OF DIVERSITY HTS SATELLITE LINK IN INDONESIA In this section we will calculate simulation for a specific satellite link operating in Jakarta, Indonesia (Latitude 6° 7' 3.5904'' S, Longitude 106° 54' 22.8564'' E).

Jakarta, Indonesia is included in Zone P rain rate 145 mm/hr. Probability (%) Outage ITU-R Rec.P.618-12 rain attenuation prediction model is used Fade Margin (db) to predicts the long-term statistic of the slant-path rain attenuation at Jakarta for frequency up to 55 GHz[6]. Fig 9. Site Diversity Simulation. Using geostationary satellite Nusantara 1 (1460 E) that covers Larger separation more than 20Km does’t give any significant all Indonesia region. diversity gain, otherwise there is significant decrease of 0 diversity gain for separation under 10 km. The elevation angle from Jakarta to Nusantara 1 was φ1=44 . The availability target P =99.99%, that needed for mostly av application such as banking, multimedia. Availability is the percentage in a year during which the satellite link is available to its users.

The outage probability , Pout is complemetary to availability, that is,

Pout = 1- Pav (14) And annual availability : T=525600P (min/year), (15) Where GainSiteDiversity (dB)

P= Pav or P= Pout (16) Distance between facility (Km)

So, if availability 99.99% it means the satellite link is available Fig 10. Site Diversity Gain VS Distance simulation. to provide services for 525547.44 min/year and unvailable only 52.56 min/year. 4 CONCLUSION Under the above assumption, the first step is use single site A three types empirical study of mitigating rain effect of Ka model. With outage probability 0.01%, a fade margin 18.5dB Band HTS is presented in this paper to provide a mitigating 3317 IJSTR©2020 www.ijstr.org INTERNATIONAL JOURNAL OF SCIENTIFIC & TECHNOLOGY RESEARCH VOLUME 9, ISSUE 03, MARCH 2020 ISSN 2277-8616 information and also be considered to be a useful technique to help implementor in Indonesia to mitigate rain effect. Significant improvement in availability was observed and is safe to conclude that at least one of the types of mitigation should be implemeted in Indonesia while using Ka Band HTS.

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