routing, resource discovery and hierarchical architecture in wireless networks ahmed helmy lecture 3...
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Routing, Resource Discovery and Hierarchical Architecture in Wireless Networks
Ahmed Helmy
Lecture 3 - A
Spring 07
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Birds-Eye View: Research in Wireless Networks @ UFL
Architecture & Protocol Design Methodology & Tools
Test Synthesis (STRESS)
Mobility Modeling(IMPORTANT)
Protocol Block Analysis (BRICS)
Query Resolution in Wireless Networks (ACQUIRE & Contacts)
Robust Geographic Wireless Services (Geo-Routing, Geocast, Rendezvous)
Gradient Routing (RUGGED)
Worms, Traceback in Mobile Networks
Behavioral Analysis in Wireless Networks
(MobiLib & IMPACT)
Multicast-based Mobility (M&M)
Mobility-Assisted Protocols (MAID)
Context-Aware Networks
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Road Map
• Unicast Routing with caching
• Resource Discovery issues
• Contact based architectures– CARD, TRANSFER
• Geographic routing issues
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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
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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)
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Routing and Resource Discovery in Wireless Networks
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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
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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
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• Cluster-based and Min. 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
Example connected dominating set, black nodes belong to the
backbone constituting a dominating set.
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• On-demand routing with caching
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Q
T
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4.a
Cache table
T: target nodeQ: queriertr: transmission range request reply
tr2
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4.b
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• 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.
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Localcachelookup
Flood request
Valid route
Neighborcachelookup
Foundlocalcache
Foundneighborcache
p1 q1
1-p1
1-q1
p2
1-p2 q2 1-q2
qr1- qr
DiscoveryRequest
State diagram for on-demand routing in DSR-like mechanisms.
p:hit ratioq: validity ratioqr: obtained by flooding
Overhead (number of transmitted messages)1 - local cache lookup: no overhead2 - Nbr Cache lookup: NC=1+.g, where g av deg, and fraction of nbrs responding3 - 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+p2q2-p1p2q2)).CF/qr
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Vmax (m/s)
Cac
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.q)
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Define cache efficacy as p.q (hit a valid local or nbr cache)
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Network size, N (nodes)
Cache Efficacy [20m/s]Cache Hit Ratio [20m/s]Cache Efficacy [1m/s]Cache Hit Ratio [1m/s]Valid Cache Ratio [1m/s]Valid Cache Ratio [20m/s]
For small transfers, in mobile, large-scale, wireless networks,cache efficacy is very low, - need new paradigms: - hierarchy, - hybrid/loose hier. Arch.s