VSAT Interference

Petter Amundsen

Managing Director, VeriSat AS

APSCC 2015, Seoul , 24th September 2015

Contents

• Causes of VSAT interference

• Why is VSAT interference challenging to combat?

• How can the interfering VSAT be determined?

Causes of VSAT Interference

• Misaligned antenna (frequent)

– Incorrect installation

• Inaccurate pointing

• Inaccurate polarization alignment (linear only)

– Disturbance of antenna pointing after installation

• Strong winds

• Physical damage

• Faulty equipment (less frequent)

– Faulty antenna cable shielding may cause retransmission of local radio signals, such as GSM and FM

– Other electronic or mechanical faults of the VSATcausing unwanted transmission to the satellite

Misaligned VSATs cause Interference

Crosspolar

Interference (XPI)

Adjacent Satellite

Interference (ASI)

Misaligned antenna

VSAT Interference – Spectrum View

VSAT TDMA carriers

ASI/XPI caused by

misaligned VSATs

Adjacent satellite

or Cross polar transponder

Nominal interference

from aligned VSATs (<-10 dB SNR)

VSAT network in

Operational satellite

Disturbed services

VSAT Return Links shared by many Terminals

• The VSATs share one or several return link carriers in TDMA mode

• Each terminal in the VSAT network has a unique ID - the terminal ID

• The terminal ID is the key for network control of each VSAT

• When the terminal ID of an interfering VSAT is known, transmission can be stopped from the network control

• How to determine the interfering terminal ID?

Bursts from different terminals

Combatting VSAT interference

Traditionally manual time-consuming trouble-shooting is necessary:

� Move batches of terminals to operate at new frequencies

� By observing the change in interference, the interfering terminals can be narrowed and eventually identified individually

New solution – SatGuard find the terminal in real-time:

� Detection of interfering VSAT terminal ID

� Interference level below -10 dB SNR

� Currently in operation at Eutelsat and SES

SatGuard technology can be applied to enable geolocation of VSATs terminals

SatGuard determines terminal ID of VSATs causing interference

1. Demodulate the operational links, find the terminal ID for each burst

2. Detect bursts on interfered link

Correlate (by time)

Result: List of interfering VSAT IDs

(i.e. MAC addresses)

SatGuard - Automatic VSAT Interference Monitoring

Terminal Report

Major VSAT Systems Supported

• DVB-RCS (many vendors)

• iDirect iNFINITI

• iDirect Evolution

• ViaSat LinkStar

• ViaSat LinkWay

• HNS IPoS-compatible networks (various models)

• Gilat SkyEdge 1, SkyEdge 2

• DVB-RCS2

• Other proprietary VSAT systems at request

SatScan GSM Classification (retransmitted by VSATs)

Operates with SNR as low as 2 dB

Internet site giving GSM cell location

Conclusions

• VSAT interference can cause severe interference that is difficult to combat

• Introduction of automatic tools (SatGuard) resolves VSAT interference quickly and may also be used proactively

• VSAT interference can be minimized and resolved quickly by:

– Good planning

– Quality cabling and connectors

– Proper installation procedures

– Verification of XPI and ASI for each terminal ID at installation time

– Monitoring of XPI and ASI for each terminal ID under operations.

– Terminals causing interference can then be easily stopped