Link Analysis and Rain Attenuation Considerations in AIII-AIT Satellite Link Project

Link Analysis and Rain Attenuation Considerations
in AI3-AIT Satellite Link Project

Introduction

General

Asian Internet Interconnection Initiative (AI3) is a series of research activities performed on a test bed, constructed using Ku band star VSAT network provided by JCSAT-3 communication satellite.

Goals of AI3 project:
1. Promote internet technologies on Asian countries
2. Develop an efficient Internet topology for Asian countries.
3. Develop recommendations and requirements for Internet connection among Asian countries
From hub station in Nara, Japan, 2 Mbps satellite links are connected to earth stations at the AI3 partners' site in several Asian contries.

Problem Statement

AI3 satellite link may be downed in case of heavy rain around AI3 earth stations of south east Asia.
The satellite link is operating round the year at lower rate than designed to avoid frequent failure.
It is nor worthful to operate the satellite link at lower rate continuously, without properly analyzing the effect of rain on the satellite link.

Objectives

Study of different rain attenuation prediction models
Selection of appropriate rain attenuation model for Thailand
Analysis of AI3-AIT satellite link, operating with different compatible transmission rates, at various rain rates.
Assessment of AI3-AIT satellite link, operating with different coding schemes, at various rain rates.

Scope and Limitations

Selection of link bit rates required for AI3-AIT satellite link at different rain rates will enable the efficient operation of such link.
Shut down of the satellite link due to heavy rain can be avoided.
Stable operation of link is greatly desired for countries where only AI3 project provides Internet connectivity.
Such study would be useful to assess other VSAT networks also.
Rain in only uplink and downlink of the satellite link is considered i.e. effects of simultaneous rain in uplink and downlink are not considered.
The result of this study, however, cannot be verified by other measurement procedure.

Methodology

General

H channels of ISDN server higher data rate user for the purpose
- Video conferencing
- Digital program
- Fast facsimile
- Internet

H channel transmission rates are
- 0.384 Mbps (H0)
- 1.536 Mbps (H11)
- 1.920 Mbps (H12)

Primary Rate Interface (PRI) transmission rate of ISDN are
- 2.488 Mbps (E1)
- 1.544 Mbps (T1)

Modem of AI3 satellite earth stations is compatible to H0, H11, H12, E1 and T1 transmission rates
Currently, AI3-AIT satellite link is operating at H11 transmission rate.
Also, AI3 earth stations are equipped with convolutional encoder and Viterbi decoder.
Modem of the ground stations is equipped with convolutional encoders of rates' 3/4, 1/2 and 7/8
Currently, AI3-AIT is operating with convolutional encoder of rate 3/4

Procedures

Rain attenuation : Garcia Model
- Reasons for selecting Garcia Model
  - Simple in use
  - gives similar accuracy in different regions of earth
  - applicable to different regions of earth.
  - Experimental results have verified that this model provides more accurate results than CCIR (1986) model.

Rain rate exceeded percentage of a year calculation : CCIR Report 563
Threshold rain rate and threshold outage time of designed AI3-AIT satellite link
Analyzing AI3-AIT satellite link with compatible transmission rates of H0, H11, H12, E1 and T1
- Calculation of bit error rate (BER) at different rain rates
- Determination of threshold rain rate and threshold outage time

Analyzing AI3-AIT satellite link with its applicable codind rates of 3/4, 1/2 and 7/8
- Calculation of BER
- Determination of threshold rain rate and threshold rain rate.

Comparision between CCIR method and Garcia method for worldwide

Comparision between CCIR and Garcia Methods for tropical region

Parameters Given for Link VSAT (AIT) Parameters

**Parameters of transmit earth station.**
Name:	AI3-AIT
Geographical coordinater:
Longitude:	100.12E
Latitude:	14.08N
Associated space station:	JCSAT-3 (Geostationary)
Elevation angle (q):	54.6⁰
Azimuth angle (Az):	114.6⁰
Uplink frequency (f_u):	14064.75 MHz
Downlink frequency (f_d):	12318.25 MHz
Height from mean sea level(g)	30m
Polarization:	Linear
Uplink:	Horizontal
Downlink:	Vertical
Gain-to-Noise ratio (G/T)	26.9 dB/K
Cross-polarization discrimination of antenna	³ 30 dB
Modulation Method	QPSK
Encoding method	Convolutional
Decoding method	Viterbi

Source: JCSAT Corporation

Satellite (JCSAT-3) Parameters

**Satellite Parameters**
Saturation power flux density (W _sat):
Inbound link	-90.6 dBW/m²
Outbound link	-92.7 dBW/m²
Saturation EIRP of satellite (EIRP_s,sat):
Inbound link	46.2 dBW
Outbound link	46.4 dBW
No. of Ku-band transponder:	16
Bandwidth of each Ku-band transponder:	36 MHz
Gain-to-Noise ratio(G_u/T_u):
Inbound link	1.5 dBW/⁰K
Outbound link	3.6 dBW/0K
Input back-off (BOI):	17.7 dB
Output back-off (BOO):	17.5 dB
Relation between output and input back-off:	BOI=BOO+0.2 dB
Cross-polarization discrimination of satellite antenna for both uplink and downlink:	³ 30 dB
Access method:	SCPC-FDMA

Source : JCSAT Corporation.

Hub (Nara, Japan) Parameters

**Parameters of Nara earth station**
Geographical Coordinates:
Longitude:	135.83⁰E
Latitude:	34.683⁰N
Elevation Angle (q):	49.4⁰
Azimuth Angle (Az):	193.6⁰
Cross-polarization discrimination of antenna	³ 30 dB
Gain-to-Noise ratio (G/T):	26.9 dB/⁰K
Encoding method:	Convolutional
Decoding method:	Viterbi
Polarization:	Linear
Uplink:	Horizontal
Downlink:	Vertical
Height from mean sea level (g):	110m

Source: JCSAT Corporation

Interference Parameters (assumed)

**Interference Parameters**
Carrier-to-adjacent satellite interference ratio for both uplink and downlink:	25dB
Carrier-to-adjacent channel interference ratio for both uplink and downlink:	20dB
Rain depolarization at receive earth station antenna	20dB
Inter Symbol Interference (ISI)	1.5dB
Antenna tracking and atmospheric loss at receive earth station (L₁)	0.5db

Source : (Ha, 1990) and (CCIR 1988)

Results

Rain attenuation

Rain attenuation calculated for uplink frequency approached to higher value

Rain rate exceeded percentage

It is higher for Bangkok rain than Japan rain, as Bangkok and Japan are situated in tropical and temperate regions of CCIR rain climate zone respectively.

Rain attenuation for different uplink and downlink rain rates for inbound link (Bangkok-Japan)

Rain attenuation for both uplink and downlink of AI3-AIT satellite link for outbound (Japan-Bangkok)

Outage time of designed AI3-AIT satellite link

Inbound (Bangkok-Japan) and Outbound (Japan-Bangkok) satellite communication

Parameter		Inbound link (Bangkok-Japan)		Outbound link (Japan-Bangkok)
Parameter		Uplink	Downlink	Uplink	Downlink
Threshold rain rate (mm/h)		38	49	21	75
Threshold outage time	% of a year	0.070436	0.006327	0.048904	0.018889
	hour	6.17	0.55	4.28	1.65
	min.	370	33	257	99

Figure shows the outage time contributed by different rain rates on total outage time corresponding to threshold rain rate of 38 mm/h of Bangkok rain and 21 mm/h of Japan rain.

Bi-directional communication

Parameter		Rain Location
Parameter		Bangkok	Japan
Threshold rain rate (mm/h)		38	21
Threshold outage time	% of a year	0.070436	0.048904
	hour	6.17	4.28
	min.	370	257

threshold rain rate is the rain rate up to which reliable opeartion of satellite link be maintained
threshold outage time is total outage time of the satellite link.

Cumulative link outage time

AI3-AIT satellite link at different transmission rate

Inbound Link (Bangkok-Japan)

Bit Error rate
- BER is calculated for the satellite link, operating with transmission rates of H1, H11, H12, T1 and E1 at different rain rates
- BER of 10^-7 is specified as criterion for reliable operation of satellite link
- Rain rate corresponds to BER of 10^-7 is determined, which is a threshold rain rate.
- Percentage of a year, in which the threshold rain rate is exceeded, is determined, which is a threshold outage time.
  
  BER at different uplink and downlink rain rates for inbound link at transmission bit rate of 1.920 Mbps (H12).
- threshold rain rates: 31 mm/h of uplink (Bangkok) only rain and 36 mm/h of downlink (Japan) only rain.
- threshold outage time: 0.094334 and 0.015111 percentage of a year for the case of uplink only and downlink only rain.
  
  BER at different uplink and downlink rain rates for inbound link at transmission bit rate of 2.0488 Mbps (E1)
- threshold rain rate: 29 mm/h of Bangkok rain and 33 mm/h of downlink rain
- threshold outage time: 0.0103049 and 0.018747 percentage of a year in the case of Bangkok rain and Japan rain respectively.

Inbound Link (Bangkok-Japan)

Threshold rain rate and threshold outage time of AI3 satellite link at different transmission rates for inbound communication (Bangkok-Japan)

Transmission rate (Mbps)	Uplink only rain				Downlink only rain
	Threshold rain rate (mm/h)	Threshold outage time			Threshold rain rate (mm/h)	Threshold outage time
	Threshold rain rate (mm/h)	% of a year	hour	min.	Threshold rain rate (mm/h)	% of a year	hour	min.
0.384 (H0)	66	0.02546	2.23	134	146	2.92*10^-5	0.00256	0.153
1.536 (H11)	38	0.070436	6.17	370	49	0.006327	0.55	33
1.544 (T1)	35	0.079601	6.97	418	47	0.007195	0.63	38
1.920 (H12)	31	0.094334	8.26	496	36	0.015111	1.32	79
2.0488 (E1)	29	0.103049	9.03	542	33	0.018747	1.64	144

Outbound Link (Japan-Bangkok)

Threshold rain rate and threshold outage time of AI3 satellite link at different transmission rates for outbound communication (Japan-Bangkok)

Transmission rate (Mbps)	Uplink (Japan) only rain				Downlink (Bangkok) only rain
	Threshold rain rate (mm/h)	Threshold outage time			Threshold rain rate (mm/h)	Threshold outage time
	Threshold rain rate (mm/h)	% of a year	hour	min.	Threshold rain rate (mm/h)	% of a year	hour	min.
0.384 (H0)	42	0.01	0.876	53	148	0.00206	0.18	11
1.536 (H11)	21	0.048904	4.28	257	75	0.018889	1.65	99
1.544 (T1)	20	0.053521	4.7	281	74	0.019517	1.71	103
1.920 (H12)	17	0.071212	6.2	374	61	0.030188	2.64	158
2.0488 (E1)	16	0.078794	6.9	414	57	0.03469	3.03	182

Bi-directional satellite communication

Threshold rain rate and threshold outage time of AI3-AIT satellite link, operating at different transmission rate for bi-directional communication.

Transmission rate (Mbps)	Rain Location	Threshold Rain rate (mm/h)	Threshold outage time
Transmission rate (Mbps)	Rain Location	Threshold Rain rate (mm/h)	% of a year	hour	minutes
0.384 (H0)	Bangkok	66	0.02546	2.23	134
0.384 (H0)	Japan	42	0.01	0.876	53
1.536 (H11)	Bangkok	38	0.070436	6.17	370
1.536 (H11)	Japan	21	0.048904	4.28	257
1.544 (T1)	Bangkok	35	0.079601	6.97	418
1.544 (T1)	Japan	20	0.053521	4.7	281
1.920 (H12)	Bangkok	31	0.094334	8.26	496
1.920 (H12)	Japan	17	0.071212	6.2	374
2.0488 (E1)	Bankok	29	0.103049	9.03	542
2.0488 (E1)	Japan	16	0.078794	6.9	414

Page maintained by Olivier Nicole

Last update: Thu, Oct 01, 98

Link Analysis and Rain Attenuation Considerations in AI3-AIT Satellite Link Project

Introduction

General

Problem Statement

Objectives

Scope and Limitations

Methodology

General

Procedures

Parameters Given for Link VSAT (AIT) Parameters

Satellite (JCSAT-3) Parameters

Hub (Nara, Japan) Parameters

Interference Parameters (assumed)

Results

Rain attenuation

Rain rate exceeded percentage

Outage time of designed AI3-AIT satellite link

Bi-directional communication

AI3-AIT satellite link at different transmission rate

Inbound Link (Bangkok-Japan)

Inbound Link (Bangkok-Japan)

Outbound Link (Japan-Bangkok)

Bi-directional satellite communication

Link Analysis and Rain Attenuation Considerations
in AI3-AIT Satellite Link Project