ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.
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Transcript of ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.
![Page 1: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/1.jpg)
ZipTx: Harnessing Partial Packets in 802.11 Networks
Nate KushmanKate Ching-Ju Lin, Dina Katabi
![Page 2: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/2.jpg)
Wasteful to throw away all correct bytes
Current wireless is all-or-nothingA packet that fails the CRC test is discarded
![Page 3: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/3.jpg)
Much prior work trys to leverage partial packets• [JB07], [WKKS07], [KKBM08], [KKRL03], HARQ, …
But…..
I only care about my 802.11 laptop
![Page 4: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/4.jpg)
• How do we build a driver that leverages partial packets?
• What are the throughput gains in 802.11 networks?
– Given 802.11’s auto-rate tries to avoid partial packets
Problem
![Page 5: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/5.jpg)
Contributions• Characterizing the throughput gains of partial
packets in 802.11 networks with auto-rate: Indoor WLANS:• Auto-rate is effective at eliminating partial packets• Gains are limited to 20-25%
Challenged outdoor and mobile networks:• Auto-rate is ineffective at eliminating partial packets• Allows 2-3x throughput gains
• ZipTx, an 802.11 driver that collects these gains
![Page 6: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/6.jpg)
Indoor Testbed• 35 nodes• Bitrates 6Mb/s 54 Mb/s• RSSI 1-34
Outdoor Testbed
Measurement Environment
• 25 nodes • Bitrates 1Mb/s 11 Mb/s• RSSI 1-12
Method• Configure hardware to pass up packets failing the CRC check• At each location, cycle between all bitrates• For each bitrate, compute correct-packet-throughput and
correct-byte-throughput
![Page 7: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/7.jpg)
Why Does Rate Adaptation Matter?Say you can’t adapt the bit rate
![Page 8: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/8.jpg)
Why Does Rate Adaptation Matter?Say you can’t adapt the bit rate
Correct Pkts at 48Mb/s
![Page 9: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/9.jpg)
Why Does Rate Adaptation Matter?Say you can’t adapt the bit rate
Correct Pkts at 48Mb/sCorrect Bytes at 48Mb/s
No Rate Adaptation Dramatic Gains
35x
![Page 10: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/10.jpg)
Why Does Rate Adaptation Matter?
Correct Pkts at 48Mb/sCorrect Bytes at 48Mb/s
Say you can adapt the bit rate
![Page 11: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/11.jpg)
Gain is about 25%; Much smaller than no autorate
Why Does Rate Adaptation Matter?Say you can adapt the bit rate
Correct Pkts at 48Mb/sCorrect Bytes at 48Mb/sCorrect Pkts at 36Mb/s
![Page 12: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/12.jpg)
Why Does Rate Adaptation Matter?Say you can adapt the bit rate
![Page 13: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/13.jpg)
Why Does Rate Adaptation Matter?Say you can adapt the bit rate
![Page 14: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/14.jpg)
Why Does Rate Adaptation Matter?Say you can adapt the bit rate
Envelope of Correct Pkts
![Page 15: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/15.jpg)
Why Does Rate Adaptation Matter?Say you can adapt the bit rate
Envelope of Correct Pkts
![Page 16: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/16.jpg)
Why Does Rate Adaptation Matter?Say you can adapt the bit rate
Envelope of Correct Pkts
![Page 17: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/17.jpg)
Why Does Rate Adaptation Matter?Say you can adapt the bit rate
Envelope of Correct Pkts Envelope of Correct Bytes
![Page 18: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/18.jpg)
Why Does Rate Adaptation Matter?Say you can adapt the bit rate
Rate Adaptation Limited Gain (about 25%)
Envelope of Correct Pkts Envelope of Correct Bytes
![Page 19: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/19.jpg)
Where Do the Gains Come From?
![Page 20: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/20.jpg)
Where Do the Gains Come From?
![Page 21: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/21.jpg)
Where Do the Gains Come From?
![Page 22: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/22.jpg)
Where Do the Gains Come From?
![Page 23: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/23.jpg)
Where Do the Gains Come From?
![Page 24: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/24.jpg)
Where Do the Gains Come From?
![Page 25: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/25.jpg)
Where Do the Gains Come From?
![Page 26: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/26.jpg)
Partial Packets allow an increase of one bit-rate
Where Do the Gains Come From?
![Page 27: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/27.jpg)
Is a gain of 25% is all that partial packets can do for 802.11?
25% is the gain in Typical Indoor WLANs
But things look different for the more challenged outdoor environment
![Page 28: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/28.jpg)
Gains in the Outdoor Environment
2x gain
Much larger gains outdoors
3.5x gain
![Page 29: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/29.jpg)
Where Do the Outdoor Gains Come From?
![Page 30: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/30.jpg)
Most Gains Are Not From Jumping Up Bit-Rates
Where Do the Outdoor Gains Come From?
![Page 31: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/31.jpg)
In outdoors, auto-rate cannot avoid partial packets
![Page 32: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/32.jpg)
What’s the fundamental difference?
![Page 33: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/33.jpg)
ZipTx
For 802.11 gains vary from 25% up to 3x
How do we get them today?
![Page 34: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/34.jpg)
Kernel
Driver
To Hardware
ZipTx Modifies the Madwifi Driver
Correct Partial PacketsAuto-Rate Maximizes
Correct bytes
From Application
![Page 35: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/35.jpg)
Need to recover incorrect bits
A software-solution has to choose between: • Block-by-block CRC’s• Coding
How Does ZipTx Correct Partial Packets?
But, we don’t know which bits are incorrect!
Distributed Errors Coding is Better
![Page 36: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/36.jpg)
How Much Coding?Need to look at percentages of byte-errors in packets90%
35% correct
60% partial pkts
~5% Erasures
• Correcting x errors requires 2x parity• We need 20% parity
Want No Overhead For Fully Correct Packets
![Page 37: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/37.jpg)
How Does ZipTx Send Packets?No Ack
Still Requires 20% Overhead for 65% of Packets
![Page 38: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/38.jpg)
How Does ZipTx Send Packets?
85% have less than 3% byte-
errors
Send a small amount of parity first, and only if still undecodable send the restOverhead = 0*.35 + .06*.5 + .2*.15 = 5%
Coded packets are piggybacked on next packet
![Page 39: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/39.jpg)
Modified Auto-Rate• Leverage existing SampleRate algorithm• But maximize throughput after correcting
partial packets
![Page 40: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/40.jpg)
Results
![Page 41: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/41.jpg)
• Same Indoor/Outdoor testbed• Repeatedly choose a source and destination
and perform a 1 minute transfer• Compared Drivers:– Unmodified Madwifi– ZipTx
• Metric of comparison:
Throughput gain =
ThroughputDriver Unmodified
ThroughputZiptx
Experimental Setup
![Page 42: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/42.jpg)
Typical Indoor WLANs
![Page 43: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/43.jpg)
In indoor WLANs, ZipTx gain is 10-20%
Typical Indoor WLANs
![Page 44: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/44.jpg)
Outdoor Environment
![Page 45: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/45.jpg)
Outdoors, ZipTx average gain is about 2x
Outdoor Environment
![Page 46: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/46.jpg)
Mobility Experiment
Repeatedly, walk down the hall and back
![Page 47: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/47.jpg)
Ziptx provides auto-rate algorithm a margin of error
Mobility Experiment
![Page 48: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/48.jpg)
Related Work
• Packet Recovery with Soft Information– [JB07], [WSKK07], and [KKBM08]
• Packet Recover with CRCs– [GJLA06], [DEV05], and [MB05]
• Packet Recover with Coding– HARQ and [KKRL03]
![Page 49: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/49.jpg)
Contributions• Auto-rate matters:
Typical Indoor: 20-25% Challenged Outdoor: 2x-3x Challenged Mobile: 2x-3x
• Today’s 802.11 can collect these gains using ZipTx
![Page 50: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/50.jpg)
Backup Slides
![Page 51: ZipTx: Harnessing Partial Packets in 802.11 Networks Nate Kushman Kate Ching-Ju Lin, Dina Katabi.](https://reader035.fdocuments.net/reader035/viewer/2022062222/5697bf921a28abf838c8f0a7/html5/thumbnails/51.jpg)
CPU Usage
CPU usage is low practical