Date post: | 19-Jan-2016 |
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Ultra Low-Delay @ Edge
Ashu SabharwalECE, Rice University
How Do You Make An Information Theorist Uncomfortable?
How Do You Make An Information Theorist Uncomfortable?Ask About Delay
Delay Has Been a Challenge: Limited Progress
What’s the Bottleneck ?
• Desire reliable communication over random channels – Fading due to mobility– Noise in hardware– …
• Theorems rely on smoothening out the variability – Law of large numbers
• Need very large signaling d.o.f to smoothen out variations
• Error exponents: block length as proxy for delay
1. Hope for Future = Many Many Antennas ?
• 3GPP standardizing 64-antenna configuration• Higher freq bands mean even more antennas in
same aperture
Many d.o.f Simultaneously Available
Power gain
Reduced variance
2. Hope For Future = Large Bandwidths?
Larger BW = more signaling d.o.f per channel use
3. Hope For Future = More Feedback ?
• Feedback Reduces Delay • Fewer d.o.f to achieve the same error
probability
More Feedback Via Full-Duplex ?
• A lot of talk in full-duplex has been about 2-way data
• It’s real power may be in reducing control overhead or control latency
4. Hope for Future = Clustered Devices ?
• Clustering is common - “Smartphone’ing” while waiting
• Higher delay is lost revenue– Ensighten’12, 1 second delay = 7% loss in customer
conversions– Amazon’12, 1 second delay = $1.6B lost revenue– Google’12, 4/10 second delay = 8 million fewer
searches• Base-stations are becoming cloudlets
Turn Disadvantage into Advantage?
• Clustered devices may have similar channels – use it to reduce protocol overhead (and hence overall delay) ?
• Clustering allows device-to-device: leverage device-to-device channels ?
New Opportunities
• New design dimensions– More antennas– More bandwidth– More feedback– More ideas from the workshop
• New use cases– Low mobility access– Clustered devices– Many more in the white papers
• New theory to understand– Large simultaneous d.o.f but each with lower power– Many many users, with different traffic types
Questions/Comments ?