Slides from Muriel Medard's Keynote at IEEE Global Conference on Signal and Information Processing, 27 November 2018, Disneyland Hotel, Anaheim, California

1. Private and Confidential codeontechnologies.com
Network Coding in Satellites
Muriel Medard

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Presentation by Muriel Medard @
27 November, Anaheim, California
2018 IEEE Global Conference
on Signal and Information Processing
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Satellite in 5G
Not just point to point
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RLNC Background
Coding Landscape
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Block Codes
Convolutional Codes
Rateless Codes
Raptor and related codes
• Rate-less (refinement to free E2E)
• Still E2E, still static
Network Codes
• RLNC enables network coding
• Deterministic construction for special cases
• Index Coding
• CATWOMAN (Linux 3.10)
Point-to-Point (PtP)
Point-to-Multi-Point (PtMP)
Network Code
1960s
1950s
1998 2003
Modern Codes
• LDPCs
• Turbo Codes
• Polar Codes
1990
to
2010

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RLNC basics
Beyond point to point
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Where to code
Different possibilities
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Satellite point-to-point
Improving throughput
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RLNC for throughput
Allow more errors
At the PHY
Error-rate performance
(AWGN channel) for RS
codes (255, 239, 17) and
(255, 223, 33) in red,
along with PHY
and Effective RLNC Error
Rates with {0.5, 1,
1.5, 2, 2.5, 3}. Note that
the cost of extra
redundancy is taken into
account through a shift in
Eb/No level, whereas
throughput is kept
constant.
“RLNC as a Network-Layer Code
A study of RLNC as a complement to physical-layer coding”
CodeOn White Paper Feb 2018
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RLNC at transport
Integrating with TCP
J. K. Sundararajan, Shah, D., Médard, M., Jakubczak, S., Mitzenmacher, M. and Barros, J.,
“Network Coding Meets TCP: Theory and Implementation”,
invited paper, Proceedings of the IEEE, March 2011, pp. 490 – 512
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Sliding window
Structure would be prohibitive
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TCP without coding
Window ceases to progress
TCPsender
window
p1 p2 p3 p4
p1
p2
p3
ACK(p1)
ACK(p1)
p2 p3 p4 p5 p5
ACK(p1)
p2 p3
p4
ACK(p1)
receiver
M. Kim, Cloud, J., ParandehGheibi, A., Urbina, L., Fouli, K., Leith, D., and Médard, M.,
“Congestion Control for Coded Transport Layers”,
IEEE ICC Communication QoS, Reliability and Modeling Symposium 2014
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TCP with coding
Window continues to progress
Prevents random losses being
interpreted as congestion
Coded TCPsender
window
p1 p2 p3 p4
Σp
SEEN(1)
SEEN(2)
p4 p5 p6 p7
SEEN(4)
SEEN(5)
SEEN(6)
Σp
Σp
Σp
Σp
Σp
Σp
SEEN(3)
p7 p8 p9 p10 p11
SEEN(7)
Σp
p8 p9 p10 p11 p12
receiver
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The four phases of queue oscillation
1. Sat gate queue not full. TCP senders
receive ACKs, increase congestion window.
Queue builds up.
2. Sat gate queue full. New packets arriving
are dropped. Senders still receive ACKs
and send more
data in the direction of the queue. Queue
continues to overflow: burst losses
3. ACKs from dropped packets become
overdue. Senders throttle back. Packet
arrival at queue slows to a trickle. Queue
drains.
4. Queue clears completely. Link sits idle for
part of the time, link not fully utilized
Note: Queue oscillation explains the packet loss phenomena on all sat links we studied
U. Speidel, L. Qian, ’E. Cocker, P. Vingelmann, J. Heide, M. Médard,
“Can Network Coding Mitigate TCP-induced Queue Oscillation on Narrowband Satellite Links?”,
International Conference on Wireless and Satellite Systems, 301–314, Springer International Publishing, July 2015
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Transport needs to be adapted to high RTT
Simple modification
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2
0
1
2
3
4
5
6
7
x 10
6
PER
Goodput(bps)
CTCPv1
CTCPv2
HTCP
Cubic
Hybla
Reno
Veno
Westwood
Rate = 10 Mbps, RTT = 500 ms
J. Cloud, Leith, D, and Médard, M. “Network Coded TCP (TCP) Performance over
Satellite Networks”, SPACOMM 2014
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RLNC for Satellite in the Pacific
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• O3b satellite connection
• Typical peak time link utilization around 50%
• TCP/NC encoders/decoders in Avarua and Auckland
• g=30, overhead variable based on feedback
• TCP/NC running alongside standard TCP
• Would probably need less overhead if all
connections were coded
Rarotonga
U. Speidel, Cocker, ‘E., Vingelmann, P., Heide, J., and Médard, M.,
“Can Network Coding Bridge the Digital Divide in the Pacific?”, Netcod 2015
U. Speidel, Cocker, ‘E., Médard, M., Heide, J., amd Vingelmann, P.,
“Topologies for the Provision of Network-Coded Services via Shared Satellite Channels”, SPACOMM 2017 (Winner Best Paper Award)

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RLNC for Satellite in the Pacific
Funafuti, Tuvalu
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• GEO downlink (16 Mbps)
• TCP supported by SilverPeak accelerator
• Very low link utilization below 25%
TCP/NC maintains steady goodput
with 1-10% packet loss
TCP/NC can complete some downloads
even with >10% packet loss
U. Spiedel, Cocker, ‘E., Vingelmann,
P., Heide, J., and Médard, M., “Can
Network Coding Bridge the Digital
Divide in the Pacific?”, Netcod 2015
P. Vingelmann, J. Heide, M. Médard,
“Can Network Coding Mitigate TCP-
induced Queue Oscillation on
Narrowband Satellite Links?,
International Conference on Wireless
and Satellite Systems, 2015
U. Speidel, Cocker, ‘E., Médard, M.,
Heide, J., amd Vingelmann, P.,
“Topologies for the Provision of
Network-Coded Services via Shared
Satellite Channels”, SPACOMM 2017
TCP/NC
experiments
Graphic: own measurement

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Which layer?
Can do both
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Coding and delay
Packet reception time
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J. Cloud, D. Leith, and M.
Médard, “A Coded
Generalization of Selective
Repeat ARQ”, INFOCOM 2015
M. Karzand, Leith, D., Cloud, J.,
and Médard, M., “Design of
FEC for Low Delay in 5G”, IEEE
Journal of Selected Areas in
Communication, Vol. 35, No. 8,
Aug. 2017, pp. 1783- 1793

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Coding and delay
Packet reception time
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J. Cloud, D. Leith, and M.
Médard, “A Coded
Generalization of Selective
Repeat ARQ”, INFOCOM 2015
(RLNC)

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In order decoded delay
Gains and tuning
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Broadcast
Transmission to multiple end users
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Satellite broadcast with feedback
TDD
dofs to decode:
dofs to decode:
dofs to decode:Rx 1
Rx 2
Rx N
Tx
M packets
M
M
M
dofs = degrees of freedom
D. Lucani, Médard, M., and Stojanovic, M., “On Coding for Delay - Network Coding for Time Division Duplexing”,
IEEE Transactions on Information Theory, vol. 58, no. 4, April 2012, pp. 2330 - 2348
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Satellite broadcast with feedback
TDD
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10
-3
10
-2
10
-1
0.3
0.4
0.5
0.6
MeanCompletionTime(s)
(a)
10
-3
10
-2
10
-1
10
0
10
1
10
2
Packet Erasure Probability
NumberofCodedPackets
(b)
Broadcast TDD Optimal
Broadcast TDD Worst Link Channel
Broadcast TDD Combined Erasure Effect
Broadcast TDD Optimal
Broadcast TDD Worst Link Channel
Broadcast TDD Combined Erasure Effect
N1
N5

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Satellite broadcast with feedback
TDD
2424
Full Duplex Broadcast using Round Robin:
Tx Rxi
1 …2 3 1M
ACK
2 3
i-th
Channel
1 3 M 3
TDD Broadcast using Round Robin:
Tx Rxi
1 2 3
ACK
i-th
Channel
9 M

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Satellite broadcast with feedback
TDD
2525
10
-3
10
-2
10
-1
10
0
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Packet Erasure Probability
MeanCompletionTime(s)
Optimal Broadcast with Network Coding TDD
Broadcast Round-Robin (RR) TDD
Broadcast RR Full Duplex (Upper Bound)
Broadcast RR Full Duplex (Lower Bound)
•Outperforms TDD
constrained Round
Robin broadcast scheme
(optimal, no coding)
•For high erasure
probability:
Outperforms
full duplex
Round Robin broadcast

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Multiple paths
Difficulty without coding
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Multiple paths
Keeping track of packets
IP flow 1 IP flow 2
Application layer
IP flow 1 IP flow 2
Application layer
Server Client
Lte NIC WiFi NIC
Block i Block i
Divide & Schedule Combine
Media
player
p1p2p3 … pw p1p2p3 … pw p1p2p3 … pw
Block 1 Block 2 Block 3 …
…
Request block i
Media file:
p1
p3
p5
p2
p4
p6
J. Cloud, du Pin Calmon, F., Zeng, W., Pau, G., Zeger, L., and Médard, M.,
“Multi-Path TCP with Network Coding for Mobile Devices in Heterogeneous Networks”,
VTC 2013
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Multiple paths
Keeping track of packets
IP flow 1 IP flow 2
Application layer
IP flow 1 IP flow 2
Application layer
Server Client
Lte NIC WiFi NIC
Block i Block i
Divide & Schedule Combine
Media
player
p1p2p3 … pw p1p2p3 … pw p1p2p3 … pw
Block 1 Block 2 Block 3 …
…
Request block i
Media file:
p1+p4
p2+p3
p1+p5
p2+p4
p3+p6
p4+p5
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MTP/NC
Coding over
multiple paths
All packets within
the MPTCP/NC
coding window
are coded
together and
pushed to
different sub-
flows
Application
MPTCP/NC
TCP TCP
Fast-
TCP/NC
Fast-
TCP/NC
IP IP
NETWORK
Network
Interface
Network
Interface
Application
MPTCP/NC
TCP TCP
Fast-
TCP/NC
Fast-
TCP/NC
IP IP
Network
Interface
Network
Interface
Network Coding and Reliable Communications Group
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MTP/NC
Coding over
multiple paths
All received
packets are
ACK’ed
All packets within
the MPTCP/NC
coding window
are coded
together and
pushed to
different sub-
flows
Each packet from
TCP generates R
linearly
independent coded
packets where
each packet is
generated from the
set of packets
within the TCP
window
Application
MPTCP/NC
TCP TCP
Fast-
TCP/NC
Fast-
TCP/NC
IP IP
NETWORK
Network
Interface
Network
Interface
Application
MPTCP/NC
TCP TCP
Fast-
TCP/NC
Fast-
TCP/NC
IP IP
Network
Interface
Network
Interface
Each received
packet is
immediately
forwarded to
the TCP layer
Network Coding and Reliable Communications Group
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31. Private and Confidential
MTP/NC
Coding over
multiple paths
All received
packets are
ACK’ed
All packets within
the MPTCP/NC
coding window
are coded
together and
pushed to
different sub-
flows
Each packet from
TCP generates R
linearly
independent coded
packets where
each packet is
generated from the
set of packets
within the TCP
window
Application
MPTCP/NC
TCP TCP
Fast-
TCP/NC
Fast-
TCP/NC
IP IP
NETWORK
Network
Interface
Network
Interface
Application
MPTCP/NC
TCP TCP
Fast-
TCP/NC
Fast-
TCP/NC
IP IP
Network
Interface
Network
Interface
MPTCP/NC
layer ACKs
all new
degrees of
freedom
received
Decoding only
occurs at the
MPTCP/NC
layer
Each received
packet is
immediately
forwarded to
the TCP layer
Network Coding and Reliable Communications Group
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MTP/NC
Different delays
log
10
(File Size)
Averagecompletiontime(ms)
Link 1: RTT =1500ms p = 10−3
Link 2: RTT =80ms p = 10−2
3 4 5 6
10
2
10
3
10
4
10
5
10
6
10
7
10
8
Uncoded
Coded, R=(1−p)−1
Coded, R=1.05(1−p)−1
log(File Size)
AverageRate(packet/s)
Link 1: RTT =1500ms p = 10−3
Link 2: RTT =80ms p = 10−2
3 4 5 6
0
200
400
600
800
1000
1200
1400
Uncoded
Coded, R=(1−p)−1
Coded, R=1.05(1−p)−1
Time (s)
Jointwindowwize(packets)
Link 1: RTT=1500ms, p = 10−2
Link 2: RTT=80ms, p = 10−1
0 10 20 30 40 50 60 70
0
50
100
150
200
250
Coded, R=(1−p)−1
Coded, R=1.05(1−p)−1
Uncoded
X
X
Network Coding and Reliable Communications Group
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MTP/NC
Different delays
log(File Size)
AverageRate(packet/s)
Link 1: RTT =1500ms p = 10−3
Link 2: RTT =15ms p = 10−2
3 4 5 6
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
Uncoded
Coded, R=(1−p)−1
Coded, R=1.05(1−p)−1
log10
(File Size)
Averagecompletiontime(ms)
Link 1: RTT =1500ms p = 10−3
Link 2: RTT =15ms p = 10−2
3 4 5 6
10
2
10
3
10
4
10
5
10
6
10
7
10
8
Uncoded
Coded, R=(1−p)−1
Coded, R=1.05(1−p)−1
Time (s)
Jointwindowwize(packets)
Link 1: RTT=1500ms, p = 10−3
Link 2: RTT=15ms, p = 0.3
0 5 10 15 20
0
20
40
60
80
100
120
140
160
180
200
Coded, R=(1−p)−1
Coded, R=1.05(1−p)−1
Uncoded
X
X
Network Coding and Reliable Communications Group
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34. Private and Confidential
Recoding
No need to decode
CODING THE NETWORK:
NEXT GENERATION
CODING FOR FLEXIBLE
NETWORK OPERATION
IEEE CTN Issue: July 2018
K. Fouli, M. Medard, K. Shroff
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Recoding
No ability to decode
Packet reception time
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Satellite Context
Multiple Relevant Topologies
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Brunel.ac.uk
Mobile
Mesh
F. Vieira et al., Satcom 2011
Multipath
Multicast
Multipath
Heterogeneous
Multi-hop
Multi-hop
kddi.com

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Recoding with losses
Different losses
1 2 4
sender
From
given
data
receiver
Recoding at intermediate nodes, without decoding
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Recoding with losses
Different losses
TCP End-to-end coding Re-encoding at node 3 only
0.0042 Mbps 0.1420 Mbps 0.2448 Mbps
(assuming each link has a bandwidth of 1 Mbps in the absence of erasures)
Time average throughput (over 641 seconds)
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Satellite in 5G
Not just point to point
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Future aspects
• Recoding at satellite
• Edge caching with coding
• On-the-ground peer-assisted satellite content delivery
• Coding for multi-beam
• Multi-sourcing with satellite
• Secure coding
Coding throughout
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41. Private and Confidential 41
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