ITU-T Kaleidoscope 2010
Beyond the Internet? - Innovations for future networks and services
A scheme for Disaster Recovery in Wireless Networks with Dynamic Ad-hoc Routing
Guowei CHEN
GITS, Waseda University, Tokyo JP.
davidchen@aoni.waseda.jp
Pune, India, 13 – 15 December 2010

Self Introduction
2000 - 2003
Master – Sun-yetsen Univ., China
2003 – 2006
WCDMA, NORTEL, G.D. China
2006 – now
Doctor course, RA, Waseda Univ., Japan
Interests: WMN, P2P

Research Background
Before Disaster backbone
CS
BS
BS BS
BS
CS
Mobile node
Pune, India, 13 – 15 Dec 2010:
ITU-T Kaleidoscope 2010 – Beyond the Internet? Innovations for future networks and services
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Research Background (cont.)
After Disaster backbone
CS damaged
BS
BS BS
BS
CS ad-hoc mode cellular mode
Pune, India, 13 – 15 Dec 2010:
ITU-T Kaleidoscope 2010 – Beyond the Internet? Innovations for future networks and services
4

Problem to solve
How to route to a BS?
G
BS C1
B
S C2
Pune, India, 13 – 15 Dec 2010:
ITU-T Kaleidoscope 2010 – Beyond the Internet? Innovations for future networks and services
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Presumptions
After disaster, mobile nodes of a cell are operational (even the BS is down).
A mobile node has two interfaces for
Cellular connection
Ad-hoc connection
A node knows its location (via GPS)
A node knows location of BSs (prestored)

Beaconing Routing
•Periodic broadcast
•Route table not always updated

Beaconless Routing

Beaconless routing (cont.)
Steps of routing: (S -> D)
S broadcasts a packet, and all the neighbors (within radius r) can receive it (A1, A2, A3, A4).
But only the neighbors within the 60 ° sector schedules a packet forward (A1, A2)
A1, A2 performs a DFD (Dynamic Forward Delay) mechanism
D
G
A3
β=60 °
A1
E
BS
A4
S A2 or

Simulation Model test area
Randomly selected broken antenna working antenna
Moving Terminal Repeater node working as gateway node in ad-hoc mode

IDCNR = m1 / N where m1 is the number of nodes initially have direct connection to a BS, and N is the total number of the nodes in the test area.
Reachability
Reachability is defined as the ratio of the nodes that are able to reach BS directly or by multi-hopping
Relative Node Density (RND) a relative node ratio is defined as follows. If a certain number of nodes are arranged in grid in the test area, and the grid interval is exactly the same as communication range, the certain number is noted as K. And RND is defined as
RND = N / K.
Average Re-send Times (AR)
If a next hop is not found, the packet has to be re-sent. AR is the average number of times of re-sending a packet.

Results
Even IDCNR is fairly low (e.g.0.3), most nodes can reach a BS within 4 hops.

Results (2 ）
0.8
0.6
1
0.4
0.2
0
0.25
0.5
0.75
Relative Node Density (RND)
1
> 4 hops
2 - 4 hops
1 hop
A relatively low Node Density can provide a fairly good reachability.
E.g. when RND is 0.5, Reachability is over 0.7

Result (3)
As speed increases, Beaconing protocol is affected more significantly than the
Enhanced-BLR protocol

Conclusion
This paper has proposed a location-based ad-hoc routing protocol used in a hybrid wireless system.
The focus is to maintain connectivity in the aftermath of a disaster.
Simulation results shows that even only a small part of the nodes can directly connect to a BS, but most nodes can route to a BS.
It outperforms the Beaconing protocols in terms of resistance to mobility.

Questions