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9/18/2003 UCAN @ MOBICOM'03 1
UCAN: A Unified Cellular and Ad-Hoc Network
Architecture
Haiyun LuoRamachandran Ramjee
Prasun Sinha, Li Erran Li, Songwu Lu
9/18/2003 UCAN @ MOBICOM'03 2
Wireless WAN v.s. LAN
1xEV-DO (HDR) Large coverage Low data rate Infrastructure
only IEEE 802.11
Small coverage High data rate Ad-hoc capable
BaseStation
9/18/2003 UCAN @ MOBICOM'03 3
Wireless WAN v.s. LAN Observations:
Commercial applications need availability assurance – only through WAN infrastructure
Low data-rate (depending on location) client reduces WAN T’put
Goal: Cost-effective way to improve WAN channel
utilization, while maintaining fairness Solution:
A new network paradigm to improve WAN T’put through opportunistic use of ad-hoc LAN
9/18/2003 UCAN @ MOBICOM'03 4
Motivation: Experiment
Verizon WirelessCDMA2000-1X
Dual interfaces Verizon Wireless
CDMA2000-1X 144Kbps
802.11b 11Mbps Destination Laptop
Locate in Lab Room w/ Poor CDMA2000-1X Channel
Relay Computer Locate in Lab
Corridor w/ Good CDMA2000-1X Ch’l
Destinationin Lab Room
Relay inLab Corridor
BaseStation
802.11b
9/18/2003 UCAN @ MOBICOM'03 5
Results
Average T’put No-relay
51.6Kbps Relay 93.9Kbps
Max T’put No-relay
95Kbps Relay 130Kbps
9/18/2003 UCAN @ MOBICOM'03 6
Outline UCAN Device UCAN Architecture
Base-station assisted routing Incentive provisioning
Simulation evaluation Conclusion, future work
9/18/2003 UCAN @ MOBICOM'03 7
UCAN Device
Dual interfaces: both 3G WAN and 802.11 LAN Laptops with 3G wireless modem and 802.11
card GTRAN Wireless ‘DotSurfer 5000 Wireless
Modem” 802.11b and CDMA2000-1X in a single client card
9/18/2003 UCAN @ MOBICOM'03 8
UCAN Architecture
low data-rate
high data-rate
Poor WANChannel
Good WANChannel
802.11b
RelayProxy
BaseStation
9/18/2003 UCAN @ MOBICOM'03 9
Issues
high data-rate
PoorChannel
GoodChannel802.11
RelayProxy
Routing Node mobility HDR channel
dynamics Scheduling Incentives
WAN operator Proxy & relay
1xEV-DOBase
Station
9/18/2003 UCAN @ MOBICOM'03 10
Routing Proxy discovery, proxy and route
maintenance On-demand and greedy proxy discovery Base station assisted error recovery
Design principles Leverage always-available HDR links Frugal use of HDR links (downlink and
uplink) Client push v.s. base station pull
9/18/2003 UCAN @ MOBICOM'03 11
On-demand Proxy Discovery
BSC
A B E
J
F
1. RtRequest Flooding with Limited Range (2 hops) --- Client Downlink Quality (A:2)
C
B E
F
D
2. Proxy Candidates D, E, F, inform BS
F
E
D3. Base station chooses E as Proxy --- Proxy table:
E2
2
6 10
5
8
7
12
1
12
2
2Dst. Proxy
A E
9/18/2003 UCAN @ MOBICOM'03 12
Greedy Proxy Discovery
BSC
A B E
D
F1. RtRequest Unicast with Range Limit (2 hops) --- A’s Downlink Quality included
2. Base station assigns E as proxy --- Proxy table:
E2
2
6 10
5
8
7
42
1
12
2
2Dst. Proxy
A E
0. Maintains one-hop neighboring devices’ downlink channel qual
9/18/2003 UCAN @ MOBICOM'03 13
UCAN Proxy Discovery On-demand
Best proxy within certain range Flooded RTREQ message Multiple Proxy Application messages on HDR
uplink Greedy
Proactive neighborhood maintenance Unicast RTREQ propagation Single Proxy Application message
9/18/2003 UCAN @ MOBICOM'03 14
Route Maintenance
BSC
A E
J
1. If B moves away
3. Base station assigns D as proxy --- Proxy table:D
2
2
B6 10
5
82
Dst. Proxy
A D
2. E reports error to Base station3. Base station proxy table:
Dst. Proxy
A A
B6B6B6B6
Dst. Proxy
A E
9/18/2003 UCAN @ MOBICOM'03 15
Route Maintenance Proxy downlink channel degradation:
Periodical piggyback in data packets Skip the proxy with degraded channel data rate
Any case: Route failure detection and recovery (1 single
message) Recovery from mobile client (receiver-initiated) HDR base station assisted (fast, efficient,
reliable)
9/18/2003 UCAN @ MOBICOM'03 16
Providing Incentives WAN operators
Increased channel utilization through ad-hoc relay
Increased channel diversity through HDR base station scheduling
No extra equipment cost Clients actively receiving
Increased throughput of their own flows through HDR base station scheduling
Idle clients ?
9/18/2003 UCAN @ MOBICOM'03 17
Incentives for Relay Clients
PoorChannel
GoodChannel802.11
RelayProxy
Refined PF scheduling Use destination’s own
channel rate Make entire path
available at base station Simplified loop
detection Further increased
channel diversity Award all relay clients
BaseStation
9/18/2003 UCAN @ MOBICOM'03 18
Simulation
NAM Snapshot
Destination
Destination
Relay
Relay
Proxy
Proxy
NS-2 simulation HDR downlink TDMA
channel w/ slow and Rayleigh fast fading
Proxy discovery and path maintenance
HDR scheduling Mobile clients of
different densities Multiple FTP/TCP,
CBR/UDP flows
9/18/2003 UCAN @ MOBICOM'03 19
Simulation Summary Throughput gain
Single flow w/ 3-hop relay: up to 50% gains with average 1 neighbor, 210% throughput gain with average 4 neighbors
Up to 60% aggregate throughput gain in five flow case w/ 3-hop relay – PF scheduling
Resilient to node mobility, sensitive to node density
Greedy proxy discovery: 50% higher energy consumption on 802.11b interfaces
On-demand proxy discovery: Up to 7 times higher overhead on HDR uplink
9/18/2003 UCAN @ MOBICOM'03 20
Related Work Multi-hop cellular
A-GSM, ODMA, MCN: reduce power consumption
MADF: tradeoff between channel utilization and complexity
iCAR: pre-deployed, dedicated, stationary relay devices
Routing for p2p traffic in MANET DSDV, DSR, AODV, TORA, GPSR, LANMAR, LAR
Cooperation enforcement (Hubaux et al)
9/18/2003 UCAN @ MOBICOM'03 21
UCAN Architectural Benefits Integration of two complementary wireless
data technologies Cellular networks
Improved channel utilization and network throughput w/o additional equipment cost
Ad-hoc networks Improved connectivity through more efficient
and reliable routing Incentives for commercial application scenarios Other resources in managed WAN infrastructure:
key management, time sync, localization …
9/18/2003 UCAN @ MOBICOM'03 22
Summary A new network paradigm of unified and
cellular ad-hoc architecture Opportunistic use of ad-hoc relay to improve
wireless WAN throughput Routing, scheduling and incentive provisioning Simulation evaluation
Design space for Wireless WAN LAN Collaboration
Future work: uplink proxy, multicast, flooding, QoS for p2p traffic