Opportunistic Routing Is Missing Its Opportunities! Sachin Katti & Dina Katabi

Opportunistic Routing R1R2R3 R4 R5 D S

Opportunistic Routing R1R2R3 R4 R5 D S Opportunistic Routing leverages opportunistic receptions

Opportunistic Routing R1R2R3 R4 R5 D S Opportunistic Routing leverages opportunistic receptions

R1R2R3 R4 R5 D S But Opportunistic Routing is missing the bulk of its opportunities

R1R2R3 R4 R5 D S Loss Longer jumps by partially correct packets, but dropped due to packet abstraction

R1R2R3 R4 R5 D S Leverage longer opportunistic receptions of partially correct packets! Opportunistic Routing capitalizes on Partial Packet Forwarding

R1R2R3 R4 R5 D S Leverage longer opportunistic receptions of partially correct packets!

Partial Packet Forwarding capitalizes on Opportunistic Routing R1 R2 D S

Partial Packet Forwarding capitalizes on Opportunistic Routing R1 R2 D S Spatial Diversity  Routers are unlikely to have error in the same byte positions

Partial Packet Forwarding capitalizes on Opportunistic Routing R1 R2 D S Together the partial packets have all the original bytes  No need to retransmit!

Opportunistic Routing Partial Packet Forwarding Synergy

Contributions Byte Level Network Coding Harvests synergy Provides adaptive error correction Provides the right abstraction for the PHY and network layers to maximize throughput

MIXIT R1 R2 D S

MIXIT R1 R2 D How do routers know which bytes are correct?  Physical layer knows!

How do routers knows which bytes are correct? PHY knows how confident it is for every byte it decodes High confidence Clean Byte Dirty Byte Forward “clean” bytes, throw away the “dirty” bytes Low confidence

Who should forward what? R1 R2 D Overlap in received correct bytes  Routers forward duplicates

How to prevent duplicate transmissions? R1 R2 D S Source transmits packets in batches P1 P2

R1 R2 D S Routers use byte level network coding How to prevent duplicate transmissions?

R1 R2 D … … … … Routers create random combinations of clean bytes How to prevent duplicate transmissions?

R1 R2 D Routers create random combinations of clean bytes … … … … … … … … … … How to prevent duplicate transmissions?

R1 R2 D Routers transmit coded packets to the destination … … … …

How to prevent duplicate transmissions? R1 R2 D Destination decodes by solving simple linear equations … … … … Solve 2 equations

How to prevent duplicate transmissions? R1 R2 D Destination decodes by solving simple linear equations … … … … Solve 2 equations

How to prevent duplicate transmissions? R1 R2 D Destination decodes by solving simple linear equations … … … … Solve 2 equations Byte Level Network Coding prevents spurious transmissions without any co-ordination or scheduling

How to represent the code? How to efficiently tell the destination the code of each bit?  Use run length encoding Original Packets Coded Packet

How to represent the code? How to efficiently tell the destination the code of each bit?  Use run length encoding Original Packets Coded Packet

How to represent the code? How to efficiently tell the destination the code of each bit?  Use run length encoding Original Packets Coded Packet

How to represent the code? How to efficiently tell the destination the code of each bit?  Use run length encoding Original Packets Coded Packet

How to represent the code? How to efficiently tell the destination the code of each bit?  Use run length encoding Run length encoding to represent contiguous runs of coded bits with the same code

Clean bytes can be incorrect Can be incorrect with low probability How does the destination recover from these errors? How does the destination recover from these errors? Clean Byte Dirty Byte High confidence Low confidence

How to recover from errors? Symbol Level Network Coding Adaptive Error-Correcting Code If k bytes are combined to produce n (>k) random combinations, destination can correct (n-k)/2 byte errors Routers can keep transmitting until destination decodes correctly  Rateless error-correcting code

To conclude… MIXIT: Harvests synergy between opportunistic routing and partial packet forwarding Provides the right abstraction for the PHY and network layers to maximize throughput