19. Arash PourdamghaniNetwork Coding
Min-Cut Max-Flow
Acyclic graph G = (V,E) with unit capacity edges,
a source vertex S, and a receiver vertex R.
If the min-cut between S and R equals h, then
the information can be send from S to R at a
maximum rate of h.
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20. Arash PourdamghaniNetwork Coding
Main Theorem
There exists a multicast transmission scheme over a
large enough finite field 𝑭 𝒒, in which intermediate
network nodes linearly combine their incoming
information symbols over 𝐹𝑞, that delivers the
information from the sources simultaneously to each
receiver at a rate equal to h.
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22. Arash PourdamghaniNetwork Coding
Finite Fields
Abelian Group -> Galois Field -> Extension Fields
Closure, Associativity, Commutativity
Identity & Inverse element
Closed on ‘+’ and ‘.’
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+ 0 1
0 0 1
1 1 0
. 0 1
0 0 0
1 0 1
23. Arash PourdamghaniNetwork Coding
Finite Fields(cont’d)
Prime Fields: 𝐺𝐹(𝑝) where 𝑝 is prime number
Extension fields: 𝐺𝐹(𝑝 𝑚) where 𝑝 is prime
number and 𝑚 > 1
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+ 0 1 A B
0 0 1 A B
1 1 0 B A
A A B 0 1
B B A 1 0
. 0 1 A B
0 0 0 0 0
1 0 1 A B
A 0 A B 1
B 0 B 1 A
24. Arash PourdamghaniNetwork Coding
Proof methods
•Algebraic
• There exist values in some large enough finite field 𝐹𝑞 for the
components {𝛼 𝑘} of the local coding vectors, such that all
matrices 𝑨𝒋,1 ≤ j ≤ N, defining the information that the
receivers observe, are full rank .
•Information Theoretic
• For each vertex 𝑣 select |𝑂𝑢𝑡(𝑣)| functions 𝑓𝑖
𝑣
: 2ℎ 𝐼𝑛 𝑣 → 2ℎ
chosen uniformly at random
• Each receiver could decode all source packets if get sufficient input
packets
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29. Arash PourdamghaniNetwork Coding
References
J. Kurose, K. Ross, “Computer Networking: Top-
Down Approach”,6th edition, Addison Wesley, 2013
M. Jafari Siavoshani, ”A Very Short Introduction to
Network Coding”, Sharif University of Technology,
Fall 2014
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30. Arash PourdamghaniNetwork Coding
References(cont’d)
C. Fragouli, E. Soljanin, “Network coding
fundamentals” Foundations and Trends in
Networking, 2007
A. Sprintson, Theory and application of network
coding, Texas A&M University, 2016
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