1. Ahmed Helmy Lecture 4 - A Spring 08
Routing, Resource Discovery and Hierarchical Architecture in Wireless Networks
Ahmed Helmy
Lecture 4 - A
Spring 08

2. Birds-Eye View: Research in Wireless Networks @ UFL
Methodology & Tools
Architecture & Protocol Design
Robust Geographic Wireless Services (Geo-Routing, Geocast, Rendezvous)
Test Synthesis (STRESS)
Query Resolution in Wireless Networks (ACQUIRE & Contacts)
Protocol Block Analysis (BRICS)
Gradient Routing (RUGGED)
Mobility Modeling
(IMPORTANT)
Multicast-based Mobility (M&M)
Worms, Traceback in Mobile Networks
Behavioral Analysis in Wireless Networks
(MobiLib & IMPACT)
Mobility-Assisted Protocols (MAID)
Context-Aware Networks

3. Road Map Unicast Routing with caching Resource Discovery issues
Contact based architectures
CARD, TRANSFER
Geographic routing issues

4. Related Reading list From book (C. Perkins): (one order of reading)
ch 3 DSDV, ch 5 DSR, ch 6 AODV, ch 8 TORA, ch 4 cluster-based, ch 7 ZRP
From the paper reading lists
unicast routing list in syllabus (all papers, most overlap with book, read the book or papers)
broadcast: - broadcsat storm, - min dominating sets
Resource discovery:
book chapter (on-line)
TRANSFER, CARD, MARQ

5. Related Reading list (contd.)
Mobility Modeling
IMPORTANT, PATHS, BRICS, Bk Chptr (posted)
Partial reading list for geographic routing aspects
GPSR, - LAR, - Geocast,
From my web site
Perfect Geocast
Inaccuracy/inconsistency ,
Face routing with inaccuracy
Mobility prediction
Black listing
Book chapter (posted)

6. Routing and Resource Discovery in Wireless Networks

7. Conventional Approaches
Flooding:
Simple
Overhead: N-1 transmissions, g.(N-1) receptions (where g is average node degree)… expensive!
Expanding Ring Search:
Repeated floods with expanding TTL
Terminates when target found
Initial TTL & increment have significant impact

8. Conventional Approaches (contd.)
Reduced Broadcast heuristics (bcast storm ppr):
Probabilistic rebroadcast with p
Counter-based: suppress bcast if cnt rx > cnt thresh
Distance-based: suppress if min(d) < D thresh, where min(d) is min dist to nbr bcast
Location-based: supp if added coverage > Area thresh
Attempts delivery to all nodes
Does not guarantee delivery
Works well when density/redundant bcast is high

9. Cluster-based and Min. Dominating Set
Example connected dominating set, black nodes belong to the
backbone constituting a dominating set.
- Guarantees delivery - Optimum Dist Algo NP hard
- Approximations reduce amount of redundant bcasts to
cover all the nodes
- re-configuration may be major with dynamics/mobility

10. On-demand routing with caching

11. DSR-like routing model:
a querier node Q issues a request for a target resource T.
The request process progresses as follows:
1. Q performs local lookup,
2. If a cached route to T is not found then request a lookup from 1-hop neighbors (within transmission range),
3. If a cached route is not found (or is invalid) then flood a request throughout the network,
4.a. Intermediate nodes with cached route to T reply to Q,
4.b. The target T replies to requests returning multiple paths to Q.

12. qr: obtained by flooding
p:hit ratio
q: validity ratio
qr: obtained by flooding
State diagram for on-demand routing in DSR-like mechanisms.
Overhead (number of transmitted messages)
1 - local cache lookup: no overhead
2 - Nbr Cache lookup: NC=1+.g, where g av deg,
and  fraction of nbrs responding
3 - Cost of Flood: CF~(N-1)+g.L+.N..L,
where L is av. path length from Q to T, .N is fraction of intermediate
nodes responding, and .L is av. path length for such responses
Ov=(1-p1).NC+(1-(p1q1+(1-p1)p2q2)).CF/qr

13. Define cache efficacy as p.q (hit a valid local or nbr cache)
[Recall: Overhead  p.q ]

14. For small transfers, in mobile, large-scale, wireless networks,
cache efficacy is very low,
- need new paradigms: - hierarchy, - hybrid/loose hier. Arch.s