SatGuard - a novel solution to combat

Challenge VSAT Terminal ASI Identify the terminal ID causing interference Measure the ASI at as low ASI level as possible Independent, autonomous operation 3 Copyright 2014 VeriSat. All rights reserved.

Current situation ASI is observed with Power Spectrum Density measurements ASI level visible at +0.5 db above the noise: Noise = 0 db + Signal = - 9 db -> ASI_signal + Noise = 0.5 db This is normally above the level of acceptable ASI When observed: may require immediate action Time-consuming to resolve the source 5 Copyright 2014 VeriSat. All rights reserved.

SatGuard Configuration Operational satellite Adjacent satellite subject to interference from VSAT terminals Forward link Return link ASI Hub Station Terminal SatGuard Monitor Unit 6 Copyright 2014 VeriSat. All rights reserved.

SatGuard Concept Synchronise and correlate information from: Operational link: Forward link signalling Return link bursts ASI link: Detection of ASI bursts 7 Copyright 2014 VeriSat. All rights reserved.

Two main approaches for finding terminal ID 1. Extract signalling information from the VSAT network forward link or 2. Full decoding of the VSAT network return link bursts and extract signalling Common to both approaches: Detect ASI burst synchronised to the frame and time slot structure by power averaging or waveform correlation 8 Copyright 2014 VeriSat. All rights reserved.

Apply Forward Link Signalling Forward Link RF (operational satellite) Interferred link (ASI) Extract: Frame structure Time burst plan Terminal id Frame sync Detect burst: Arrival time Power level Correlate information Terminal ID 9 Copyright 2014 VeriSat. All rights reserved.

Apply Return Link Decoding Return Link RF (operational satellite) Interferred link (ASI) Map burst structure Decode payload Extract terminal id Frame sync Detect burst: Arrival time Power level Correlate information Terminal ID 10 Copyright 2014 VeriSat. All rights reserved.

Detailed block diagram Forward Link mode Forward Link RF (operational satellite) ASI link (monitored satellite) Forward Link signalling decodiing RL link RF capture in the satellite with interference Extract time burst plan and terminal id Frame sync Detect interfering RL bursts (only interfering bursts have sufficient SNR to be found) Correlate arrival time of ASI burst with frame structure Look up time slot assignment burst time plan Look up terminal ID Terminal ID, ASI power level 11 Copyright 2014 VeriSat. All rights reserved.

Detailed block diagram Return Link mode Return Link RF (operational satellite) ASI link (monitored satellite) Decode RL bursts (good SNR, all bursts decoded) RL link RF capture in the satellite with interference Determine timeslot map Extract terminal id Frame sync Detect interfering RL bursts (only interfering bursts have sufficient SNR to be found) Correlate arrival time of ASI burst with decoded bursts Look up terminal ID Terminal ID, ASI power level 12 Copyright 2014 VeriSat. All rights reserved.

Burst detection through power averaging Good results require: Accurate measurement of noise floor Synchronisation to frame and time slot structure Knowledge of time slot assignment (which terminal id is transmitting in each burst) Averaging of a reasonable amount of bursts for each terminal (lower levels more bursts) 14 Copyright 2014 VeriSat. All rights reserved.

Averaging Smoothing/averaging the signal power levels will allow detection of bursts as long as they appear above the noise floor. In the figures below, the burst power is about the same as the noise level. 15 Copyright 2014 VeriSat. All rights reserved.

Burst detection through general correlation Correlation techniques allow very low power levels to be detected For TDMA links, the correlation must be synchronised to the time slot assignments for each terminal 17 Copyright 2014 VeriSat. All rights reserved.

SatGuard can enable: Measure level of ASI for each terminal: Under commisioning, confirm acceptable ASI level Monitor ASI 24/7, determine antenna misalignment when it happens, before ASI level is visible Measure XPOL interference level for each terminal Under commisioning, confirm acceptable XPOL level Monitor XPOL interference 24/7, determine antenna misalignment when it happens, before XPOL is visible Support interference monitoring also where ASI and XPOL interference are masked by other services Subtract overlying signal, then perform correlation Geo-location of individual terminals 18 Copyright 2014 VeriSat. All rights reserved.