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© 2008 VT iDirect, Inc.
PCMA:Enhancing Bandwidth Efficiency in New and Old NetworksNinh Le
Director, Complex Systems Group
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PCMA Saves 15% – 45% on Bandwidth
Without PCMA
Satellite Transponder Spectra
Normalized Frequency Normalized Frequency
P o w e r ( d B )
P o w e r ( d B )
With PCMA
PCMA saves satellite bandwidth by using the same
spectrum for both upstream & downstream carriers.Hughes Network Systems (HNS) makes proprietary Outroute Cancellation
EMC makes COTS (commercial off-the shelf) NRS Bandwidth Booster
ViaSat makes COTS PCMA (Paired Carrier Multiple Access)
Comtech makes COTS DoubleTalk under license from AST
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PCMA Is Easy to Implement
Because It Only Goes at the Hub
Overlapping uplink signal is subtracted to getdesired downlink signal
Downlink =Hub + Remote
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Remote Hub
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Why Does PCMA Work Best on iDirect Systems and
Not So Well on Other VSAT Systems?
iDirect’s upstream carriers use 100% reservation access
Other VSAT need random access because traffic is often bursty.
Collisions in random access schemes like Slotted Aloha spike power.
20% of TDMA bursts in Slotted Aloha overlap bursts from other remotes.
2 bursts colliding doubles power; 3 bursts colliding triples power; etc.
Power spikes jam downstream, occasionally forcing competing VSAT off net.
iDirect’s 100% reserved upstream avoids power spikes to downstream
Only iDirect’s reservation scheme is responsive enough to carry bursty traffic.
iDirect’s remote terminals all have uplink power control (UPC).
Without UPC, remotes uplink maximum power all the time.
Maximum power typically contains 2-3 dB of extra power for rain fade andanother few dB of extra power for differences in G/T contour.
Every dB of extra uplink power at any remote is a dB of unnecessaryinterference to the downstream carrier.
Downstream facing more interference needs more transponder power or aless efficient MODCOD to overcome the extra (unnecessary) interference.
UPC minimizes upstream power interfering with downstream carrier.
UPC makes all remotes hit satellite with the same (minimum) flux density.
No unnecessary interference = maximum efficiency.
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When Should iDirect Bring Up PCMA as a Topic?Obvious Situations
When new bandwidth is not available for new projects, PCMAfrees up existing bandwidth for use by new iDirect VSAT.
When low margin projects need cost cuts to be viable, PCMA cutsoperating costs, especially for bandwidth intensive apps.
For Evolution, PCMA saves the most BW in 3:1 asymmetric networks.
iNFINITI best in networks too small for DVB-S2’s min (2-3 MHz) scale.
For iNFINITI networks…
PCMA cuts operating costs by the same amount as LDPC from DVB-S2
PCMA upgrade takes less time, work, & money than DVB-S2 upgrade
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When Should iDirect Bring Up PCMA as a Topic?Payback Calculator for Obvious Situations
DS IP Data Eff ic iency 1 .29 bi ts /sec/HzUS IP Data Effici ency 0.8 bits/sec/Hz
Satelli te BW Cost 5,000 $/MHz/Month
IFL Frequency L-Band
1:1 PCMA Redundancy YesFrequency Converters Yes
Installation Services Yes (Frequency Converters)SkyMonitor No
Installation Services No (SkyMonitor)
US IP Data
Throughput,
Mbps
Payback
Period,
Months
Additional
Revenue,
%
US IP Data
Throughput,
Mbps
Payback
Period,
Months
Additional
Revenue,
%
US IP Data
Throughput,
Mbps
Payback
Period,
Months
Additional
Revenue,
%
US IP Data
Throughput,
Mbps
Payback
Period,
Months
Additional
Revenue,
%
US IP Data
Throughput,
Mbps
Payback
Period,
Months
Additional
Revenue,
%
0.50 0.50 31 62.0% 0.33 33 80.4% 0.25 47 57.1% 0.17 79 33.7% 0.13 120 22.0%
1.00 1.00 16 62.0% 0.67 17 80.4% 0.50 24 57.1% 0.33 40 33.7% 0.25 60 22.0%2.00 2.00 8 62.0% 1.33 9 80.4% 1.00 12 57.1% 0.67 20 33.7% 0.50 30 22.0%3.00 3.00 6 62.0% 2.00 6 80.4% 1.50 8 57.1% 1.00 14 33.7% 0.75 20 22.0%4.00 4.00 4 62.0% 2.67 5 80.4% 2.00 6 57.1% 1.33 10 33.7% 1.00 15 22.0%5.00 5.00 4 62.0% 3.33 4 80.4% 2.50 5 57.1% 1.67 8 33.7% 1.25 12 22.0%
6.00 6.00 3 62.0% 4.00 3 80.4% 3.00 4 57.1% 2.00 7 33.7% 1.50 10 22.0%
7.00 7.00 3 62.0% 4.67 3 80.4% 3.50 4 57.1% 2.33 6 33.7% 1.75 9 22.0%8.00 8.00 2 62.0% 5.33 3 80.4% 4.00 3 57.1% 2.67 5 33.7% 2.00 8 22.0%9.00 9.00 2 62.0% 6.00 2 80.4% 4.50 3 57.1% 3.00 5 33.7% 2.25 7 22.0%
10.00 10.00 2 62.0% 6.67 2 80.4% 5.00 3 57.1% 3.33 4 33.7% 2.50 6 22.0%
15.00 15.00 2 62.0% 10.00 2 80.4% 7.50 3 57.1% 5.00 4 33.7% 3.75 6 22.0%20.00 20.00 2 62.0% 13.33 2 80.4% 10.00 2 57.1% 6.67 3 33.7% 5.00 5 22.0%25.00 25.00 1 62.0% 16.67 1 80.4% 12.50 2 57.1% 8.33 3 33.7% 6.25 4 22.0%30.00 30.00 1 62.0% 20.00 1 80.4% 15.00 2 57.1% 10.00 3 33.7% 7.50 4 22.0%35.00 35.00 1 62.0% 23.33 1 80.4% 17.50 2 57.1% 11.67 2 33.7% 8.75 3 22.0%
PCMA Payback Period and Additional Revenue Calculator
Satellite Links Paramaters
Hub Equipment Configuration
Downstream IP Data
Aggregate
Throughput,
Mbps
4 : 1
DS-to-US Link Asymmetry
1 : 1 1.5 : 1 2 : 1 3 : 1
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When Should iDirect Bring Up PCMA as a Topic?Less Obvious Situations
When competing against Comtech’s CDM-QxL modems, PCMAmakes iDirect’s SCPC modems comparable in BW efficiency.
PCMA expands iDirect’s addressable GSM market to thicker trunks.
In SCPC applications, both sides of a link need a PCMA canceller.
To afford PCMA at all sites, iDirect needs L-band PCMA canceller.
ViaSat should deliver first L-band PCMA cancellers in Q2 of 2009.
When special access is required for the return channel…
PCMA hides upstream carriers from detection
PCMA makes bandwidth for spread spectrum carriers affordable
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iDirect Hub with PCMA and Quintech Converters
iDirect
Hub P C M A
C a n c e l l e r
Frequency
(Up)
Converter
1
RXRX
OutRX
InIFL
Out
IF
InIF
OutIFL
In
L Band
70 MHz BNC F
LNB
Rx
Power In
Nominal: -25dBm
Min: -65dBm
Max: -5dBm
Power In
Nominal: -25dBm
Min: -50dBm
Max: -20dBm
Power OutNominal: -25dBm
Min: -50dBm
Max: -20dBm
Power OutNominal: -25dBm
Min: -50dBm
Max: -20dBm
Power In
Nominal: -25dBm
Min: -50dBm
Max: -20dBm
TXTX
In
TX
Out
Frequency
(Down)
Converter
2IFL
In
IF
Out
IF
InIFL
Out
HPA
Tx
Power Out
Nominal: -25dBm
Min: -35dBm
Max: +7dBm
Power Out
Nominal: -25dBm
Min: -50dBm
Max: -20dBm
Power In
Nominal: -25dBm
Min: -50dBm
Max: -20dBm
Power In
Nominal: -25dBm
Min: -30dBm
Max: +10dBm
Power Out
Nominal: -25dBm
Min: -35dBm
Max: -5dBm
Power In
Nominal: -25dBm
Min: -50dBm
Max: -20dBm
Power Out
Nominal: -25dBm
Min: -50dBm
Max: -20dBm
L-band
CenterFrequency
70
MHz CenterFrequency
70
MHz CenterFrequency
L-band
CenterFrequency
L-band
Center
Frequency
70
MHz Center
Frequency
70
MHz Center
Frequency
L-band
Center
Frequency
Frequency
(Up)
Converter
4
Frequency
(Down)
Converter
3
Power In
Nominal: -25dBm
Min: -30dBm
Max: +10dBm
Power OutNominal: -25dBm
Min: -35dBm
Max: -5dBm
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iDirect Will Sell PCMA Cancellers at List Price
PCMA Packages from iDirect Frequency Converters Option
Single Amount of MSRP for Mandatory Minimum Frequency FrequencyThread or Cancellation PCMA Professional PCMA Converters ConvertersRedundant (MHz) Appliance Services Packages for L-band IFL for 70 MHz IFL
Single Thread 2 12,499$ 9,000$ 21,499$ 7,320$ 3,660$Single Thread 5 15,999$ 9,000$ 24,999$ 7,320$ 3,660$Single Thread 10 24,999$ 9,000$ 33,999$ 7,320$ 3,660$Single Thread 20 37,499$ 9,000$ 46,499$ 7,320$ 3,660$Single Thread 36 49,999$ 9,000$ 58,999$ 7,320$ 3,660$1:1 Redundant 10 42,498$ 9,000$ 51,498$ 7,320$ 3,660$1:1 Redundant 20 63,748$ 9,000$ 72,748$ 7,320$ 3,660$1:1 Redundant 36 84,998$ 9,000$ 93,998$ 7,320$ 3,660$
Frequency Converters from Quintech deliver best phase noise value.Technical Support Charges after the Sale: as per standard iSupport fees.Mandory Professional Services: 3.5 days including travel and expenses.
Link budget analysis to quantify bandwidth savingsDesign of PCMA networkPre-installation coordinationInstallation of PCMA Canceller
Acceptance Testing, Training, and Documentation
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Operational Considerations
Necessary Link Conditions
Duplex circuits only (symmetric or asymmetric inroute + outroute)Loopback transponder to receive own uplink signal. No cross-strap Xpdr.
Nice to Have: Factors that Make PCMA More Efficient
Cancellation at Both Sides of Each SCPC Link (Comtech CDM-QxL)
Large Hub Antennas
5+ meter Ku-band antenna
7+ meter C-band antenna
More Powerful Satellite Transponders
48+ dBW EIRP for 36 MHz Ku-band transponders
38+ dBW EIRP for 36 MHz C-band transponders
Lower Link Availability
99.0% or lower end-to-end availability for Ku-band links99.7% or lower end-to-end availability for C-band links
Lower SNR (signal to noise ratio) Thresholds
Better FEC coding (LDPC vs. TPC)
Lower MODCOD’s (BPSK and QPSK vs. 8PSK and 16APSK)
Asymmetric downstream:uptream traffic (1:1 to 3:1 asymmetry is best)
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Operational Considerations
Required Changes in Network Operating Processes
Need one upstream carrier outside PCMA to bring in new VSATCW to peak BUC power at new remote must be done outside PCMA
CW jams shared downstream. Never overlay CW on downstream.
Bring remotes into network at low initial transmit powerLet UPC slowly lift dBm from below SNR threshold to optimal SNR
This acquisition process takes more time than starting at high dBm
Geographic redundancy in iDS 7.0 or later software is neededEach remote in a PCMA network should have 2 networks configured
Primary configuration is the network as it should be with PCMA
Second configuration uses the same spectrum for unpaired carriers thatremotes can fail over to if normal PCMA operations are ever disrupted
To prevent jamming from inter-symbol interference, symbol rates ofpaired carriers cannot be within 5% of each other.
UPC must target no more than SNR threshold + 0.5 dBUpstream SNR 0.5 dB beyond SNR threshold harms downstream
Fine UPC adjustments needed when SNR within ± 0.5 dB of target
Downstream PEB + Upstream PEB ≤ Allocated PEB Downstream carrier typically 0.1 to 0.5 dB bandwidth limited
0.1 to 0.5 dB of total power typically used for upstream carrier
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PCMA Link Budget Analysis: Additional Interference to Downstream Carrier
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PCMA Link Budget Analysis: Additional Interference to Upstream Carrier
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PCMA Link Budget Analysis:Math to Quantify Additional Interference to Both Downstream and Upstream Carriers
1
SNReffective
= Σ 1
SNRii = 1
n
Note: SNR above must be quantified in power ratios, not dB’s.
dB SNR = 10 x log( ) Watts of Signal
Watts of Noise
Therefore, in the first equation above…
SNRi = 10(dB SNR)÷10
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PCMA Link Budget Analysis:Spread Sheet to Quantify Interference to Both Downstream and Upstream Carriers
DownstreamLBA
Upstream
LBA
+
PCMA Downstream Interference AnalysisUnits
Carrier/Link ParametersModulation 4-PSK 2 bits/symRequired Eb/No with FEC coding 5.9 dB
FEC code rate 0.6284
Clear Rain over Rain over
Sky Hub VSAT
PCMA Totals per carrier (End-to-End)
C/(N+I) without upstream interference 12.01 12.01 11.52 dB
Downstream satellite power density -40.44 -40.44 -40.44 dBW/HzUpstream satellite power density towards VSAT -48.96 -48.96 -49.18 dBW/Hz
C/USI (UpStream Interference) 8.52 8.52 8.74 dBC/(N+I) with upstream interference 6.91 6.91 6.90 dB
Required C/(N+I) 6.89 6.89 6.89 dBSystem Margin 0.02 0.02 0.01 dBC/(N+I) degradation due to upstream interference 5.10 5.10 4.62 dB
PCMA Upstream Interference AnalysisUnits
Carrier/Link Parameters
Modulation 4-PSK 2 bits/symRequired Eb/No with FEC coding 8.2 dB
FEC code rate 0.793PCMA cancellation 27 dB
Clear Rain over Rain over Sky Hub VSAT
PCMA Totals per carrier (End-to-End)
C/(N+I) without downstream interference 11.20 10.90 10.99 dBUpstream satellite power density -48.96 -48.96 -49.18 dBW/Hz
Downstream satellite power density towards Hub -40.44 -40.44 -40.44 dBW/HzC/DSI (DownStream Interference) 18.48 18.48 18.26 dB
C/(N+I) with downstream interference 10.46 10.20 10.24 dBRequired C/(N+I) 10.20 10.20 10.20 dB
System Margin 0.25 0.00 0.04 dBC/(N+I) degradation due to downstream interference 0.74 0.70 0.75 dB
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Additional Considerations for Saturated Transponder:1.5 dB OBO and 1 dB Extra Upstream Eb/No Threshold Are Recommended
Downstream Downstream Downstream Downstream Downstream Downstream SNR DownstreamOutput Backoff MODCOD HPA Uplink Pwr Av. SCPC Errors SNR Threshold at 9m Antenna EIRP at Hub(dB) (Watts) (Packets/20sec) (dB) (dB) (dBW)
0.0 8PSK rate 5/6 45.7 0 10.6 14.3 49.30.5 8PSK rate 5/6 40.3 0 10.6 13.3 48.91.0 8PSK rate 5/6 37.8 0 10.6 13.4 48.41.5 8PSK rate 5/6 30.5 0 10.6 12.0 47.91.5 8PSK rate 5/6 30.8 0 10.6 13.8 47.92.0 8PSK rate 5/6 26.1 0 10.6 13.0 47.42.5 8PSK rate 5/6 24.1 0 10.6 12.5 46.93.0 8PSK rate 5/6 21.9 0 10.6 12.4 46.41.0 8PSK rate 5/6 37.6 0 10.6 14.2 48.41.0 8PSK rate 5/6 37.6 0 10.6 14.1 48.41.0 8PSK rate 5/6 37.6 0 10.6 14.1 48.4
1.0 8PSK rate 5/6 37.6 0 10.6 14.0 48.41.0 8PSK rate 5/6 39.0 0 10.6 12.9 48.51.5 8PSK rate 5/6 30.8 0 10.6 12.3 47.9
Downstream Upstream VSAT Modem Upstream Upstream SNR SNR of TDMA SNR of TDMA Upstream TotalOutput Backoff MODCOD Power to BUC Av. CRC Errors Threshold Carrier Inside Carrier Outside Baud Rate(dB) (dBm) (Bursts/20sec) (dB) PCMA Spectrum PCMA Spectrum (Msps)
0.0 QPSK rate 0.66 -10 0 6.1 9.0 9.5 1.5360.5 QPSK rate 0.66 -10 0 6.1 12.0 12.5 1.5361.0 QPSK rate 0.66 -10 0 6.1 12.3 13.4 1.536
1.5 QPSK rate 0.66 -10 0 6.1 14.0 14.5 1.5361.5 QPSK rate 0.66 -17 0 6.1 6.7 7.1 1.5362.0 QPSK rate 0.66 -17 0 6.1 8.2 8.6 1.5362.5 QPSK rate 0.66 -17 0 6.1 8.6 8.7 1.5363.0 QPSK rate 0.66 -17 0 6.1 8.9 8.9 1.5361.0 QPSK rate 0.66 -17 20 6.1 5.5 5.0 1.5361.0 QPSK rate 0.66 -16 0 6.1 6.0 6.4 1.5361.0 QPSK rate 0.66 -15.5 0 6.1 6.5 6.4 1.5361.0 QPSK rate 0.66 -15 0 6.1 7.0 7.0 1.5361.0 QPSK rate 0.66 -15 0 6.1 6.2 6.8 27.5121.5 QPSK rate 0.66 -15 0 6.1 8.3 9.7 27.512
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Conclusion:
PCMA can give iNFINITI VSAT the efficiency of DVB-S2.
PCMA can boost the efficiency of DVB-S2 even further.