## Path Diversity over Packet Switched Networks: Performance Analysis and Rate Allocation

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Fashandi, Shervan

Gharan, Shahab Oveis

Khandani, Amir K.

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Path diversity works by setting up multiple parallel connections between the
end points using the topological path redundancy of the network. In this paper,
\textit{Forward Error Correction} (FEC) is applied across multiple independent
paths to enhance the end-to-end reliability. Network paths are modeled as
erasure Gilbert-Elliot channels. It is known that over any erasure channel,
\textit{Maximum Distance Separable} (MDS) codes achieve the minimum probability
of irrecoverable loss among all block codes of the same size. Based on the
adopted model for the error behavior, we prove that the probability of
irrecoverable loss for MDS codes decays exponentially for an asymptotically
large number of paths. Then, optimal rate allocation problem is solved for the
asymptotic case where the number of paths is large. Moreover, it is shown that
in such asymptotically optimal rate allocation, each path is assigned a
positive rate \textit{iff} its quality is above a certain threshold. The
quality of a path is defined as the percentage of the time it spends in the bad
state. Finally, using dynamic programming, a heuristic suboptimal algorithm
with polynomial runtime is proposed for rate allocation over a finite number of
paths. This algorithm converges to the asymptotically optimal rate allocation
when the number of paths is large. The simulation results show that the
proposed algorithm approximates the optimal rate allocation (found by
exhaustive search) very closely for practical number of paths, and provides
significant performance improvement compared to the alternative schemes of rate
allocation.

Comment: 44 pages, 15 eps files. University of Waterloo Technical Report

Comment: 44 pages, 15 eps files. University of Waterloo Technical Report

##### Keywords

Computer Science - Networking and Internet Architecture, Computer Science - Information Theory