Using Low-Speed Links for High-Speed Wireless Data Delivery - - PowerPoint PPT Presentation
Using Low-Speed Links for High-Speed Wireless Data Delivery Henning Schulzrinne Dept. of Computer Science Columbia University (with Stelios Sidiroglou and Maria Papadopouli) ORBIT Research Review - May 13, 2004 1 Overview Disconnected
ORBIT Research Review - May 13, 2004 1
(with Stelios Sidiroglou and Maria Papadopouli)
ORBIT Research Review - May 13, 2004 2
Disconnected ad-hoc networks multi-modal networking using low-speed feedback to accelerate data
7DS prototype future work
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Wireless networks:
Ubiquitous, fast, cheap: pick any two…
Currently, varies from 0.1c to $4/MB Research has primarily explored:
multi-hop connected ad-hoc networks (mesh networks)
But:
2G/3G bandwidth will remain low and precious hot spots not ubiquitous ad hoc networks don’t scale brittle if spanning large areas
Our proposal: use mobile nodes to carry data
to and from infrastructure networks
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8 kb/s ? 10 kb/s 25 kb/s 20 kb/s 8 kb/s 512/128 kb/s 155 Mb/s speed
P P C P C C P P
mode
$20 Iridium $2.06 HSCSD $0.66-$1.70 GSM voice $/MB (= 1 minute of 64 kb/s
videoconferencing or 1/3 MP3)
Modality $133 Motient (BlackBerry) $62.50 SMS (160 chars/message) $4-$10 GPRS $0.018 Australian DSL
(512/128 kb/s)
$0.0013 OC-3
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Good for hotspots, difficult for complete coverage Manhattan = 60 km2 6,000 base stations (not
With ~ 600,000 Manhattan households, 1% of households
Almost no coverage outside of large coastal cities
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Two directions for data:
Internet mobile nodes mobile nodes Internet
Each in multiple hops but not routed
low high voice (2G, 2.5G) satellite SMS? low 802.11 hotspots 7DS high
seven degrees of separation
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Tourism:
get information about sights, travel, public transport schedules, .. upload picture postcards and video recordings
Transportation:
users in buses and trains leverage data capability
Emergencies:
propagate “I’m alive” and rescue information
Mobile sensors:
sensors spread too far to communicate directly with each other large sensor data objects
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Disconnected Infostation 2G/3G access sharing 7DS Connected Infostation WLAN
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Deliver web content to roaming user
deliver matching documents “weather?”
multicast
query for all documents
web cache
7DS node
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"!#$
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200 400 600 800 1000 1200 1400 1600
10 20 30 40 50 60 70 80 90 100 Dataholders (%) Average Delay (s)
P2P (high transmission power) one initial dataholder & 20 cooperative hosts in 2x2 P2P(medium transmission power) one initial dataholder & 20 coperative hosts in 1x1
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Carrier is “infected”, hosts
Transmit to any give host
Pure birth process T=time until data has
E[T]=1/a Σ
Statistical mechanics
*
+,
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Email service interface
propagate to other pedestrians
7DS MTA
encrypt message; encrypt headers with 7DS public key
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Problems with open-loop
no way to inject popular
content into the system
have to limit replication to
avoid flooding
If too few copies, may
never get delivered
copies persist long after
delivery succeeded
Thus, transform into closed-
information
by mobility
control information
data
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Options:
satellite radio (XM, Sirius) LEO satellites (Iridium) low-bandwidth cellular
See also: Ambient Devices
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MTA PL-900 POCSAG
SNPP (RFC 1861)
FLEX
1600-6400 b/s
“message 42 delivered”
remove from cache
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Receiving MTA broadcasts
prevent spoofing
cache
delivery
Popularity management
content distributed to 7DS nodes
from others
Reputation management
and bad guys
messages fast
messages
preferably from good guys
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Initial Java implementation
search not just by URL, but by content greater likelihood of finding appropriate material
Working on PDA implementations Also, considering Linux embedded systems
low-power, self-contained
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Hordes of low-bandwidth
split large or urgent message
spread pieces across many
each node transmits at very
low rate
use Tornado codes for
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7DS as extension of infrastructure and ad-
Combine benefits of low bit-rate, but