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Approximate Semantics for Wirelessly Networked Applications - - PowerPoint PPT Presentation
Approximate Semantics for Wirelessly Networked Applications - - PowerPoint PPT Presentation
Approximate Semantics for Wirelessly Networked Applications Benjamin Ransford Adrian Sampson Luis Ceze WACAS 14 // March 2, 2014 1 Algorithms Programming Languages Compilers Storage Arithmetic Units WACAS
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Programming Languages ✅ Algorithms ✅ Compilers ✅ Storage ✅ Arithmetic Units ✅ Communication ❌
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foo.bmp
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foo.bmp
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foo.bmp
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foo.bmp
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12m apart @ UW CSE
- 10
20 30 40 6 12 18 24 30 36 42 48 54
WiFi Bitrate (Mbps) Frames Retransmitted (%)
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802.11 frame payload 802.11 frame checksum 802.11 frame header IP header IP payload IP header checksum TCP header Application data TCP checksum
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12m apart @ UW CSE
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20 30 40 6 12 18 24 30 36 42 48 54
WiFi Bitrate (Mbps) Frames Retransmitted (%)
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12m apart @ UW CSE
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20 30 40 6 12 18 24 30 36 42 48 54
WiFi Bitrate (Mbps) Frames Retransmitted (%)
< 3% of bits are bad!
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Selective Approximate Protocol
- Optional, partial integrity checks
- Suitably generic (can work with “your” apps)
- Backward compatible with existing networks
- Simple API
“SAP”
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Selective Approximate Protocol
Move error checking to the application layer!
802.11 frame payload 802.11 frame checksum 802.11 frame header IP header IP payload IP header checksum TCP header Application data TCP checksum
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Selective Approximate Protocol
Move error checking to the application layer!
802.11 frame payload 802.11 frame checksum 802.11 frame header IP header IP payload IP header checksum TCP header Application data TCP checksum
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Selective Approximate Protocol
802.11 TCP Application Move error checking to the application layer!
802.11 frame payload 802.11 frame checksum 802.11 frame header IP header IP payload IP header checksum TCP header Application data TCP checksum
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Selective Approximate Protocol
802.11 TCP Application 802.11 UDP-Lite Application Move error checking to the application layer!
802.11 frame payload 802.11 frame checksum 802.11 frame header IP header IP payload IP header checksum TCP header Application data TCP checksum
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Applications
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Open Questions
- Encryption, compression, encoding challenges
- How best to integrate quality metrics?
- How to expose quality controls to apps?
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Summary
- Mismatch between approximate computing and
precise communication
- Relax lower-layer integrity checks
- Improve throughput & range