Zone Sharing: A Hot-Spots Decomposition Scheme for Data-Centric Storage in Sensor Networks
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Transcript of Zone Sharing: A Hot-Spots Decomposition Scheme for Data-Centric Storage in Sensor Networks
Zone Sharing: A Hot-Spots Decomposition Scheme
for Data-Centric Storage in Sensor Networks
Mohamed Aly Nicholas Morsillo
Panos K. ChrysanthisKirk Pruhs
Advanced Data Management Technologies LabDept. of Computer Science
University of Pittsburgh
DMSN’05
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Roadmap
Background Problem Statement: Storage Hot-spots Algorithms: Zone Sharing Experimental Results Conclusions
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Sensor Networks Data Characteristics
Monitoring Applications: One or more phenomenon
Sensor readings: events An event contains one or more attributes for each
phenomenon under concern Querying load variations
Continuous queries: e.g. habitat monitoring applications Ad-hoc queries: e.g. disaster management applications
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Sensor Networks Data Storage Options
Base station storage Events are sent to base stations where queries are issued
and evaluated Best suited for continuous queries
In-Network storage Events are stored in the sensor nodes Best suited for ad-hoc queries
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Data-Centric Storage
Quality of Data (QoD) of ad-hoc queries Define an event owner based on the event value Examples:
Distributed Hash Tables (DHT) [Shenker et. al., HotNets’03]
Geographic Hash Tables (GHT) [Ratnasamy et. al., WSNA’02]
Distributed Index for Multi-dimensional data (DIM)[Li et. al., SenSys’03]
Greedy Perimeter Stateless Routing algorithm (GPSR)[Karp & Kung, Mobicom’00]
Among the above schemes, DIM has been shown to exhibit the best performance
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Storage Hot-Spots
S1x є
[1,10]
S2x є
[10,20]
S3x є
[20,30]
S4x є
[30,40]
50%
40%
7%
3%
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Zone Sharing in DIM
S2x є
[10,20]
y є [1,10]
S3x є
[10,20]
y є [10,20
]
S1x є
[1,10]y є
[1,20]
Z = 0
Z = 10
Z = 11
70%
5%
25%
S1
S2 S3 A = 0
A = 10 A = 11
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Zone Sharing in DIM
S2x є
[1,10]y є
[1,10]
S3x є
[10,20]
y є [1,20]
S1x є
[1,10]y є
[10,20]
Z = 01
Z = 00
Z = 1
35%
35%
30%
(donor)
(migrator)
(receiver)
S3
S2 S1 A = 1
A = 00 A = 01
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Hot-Spot Decomposition in Zone Sharing
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Hot-Spot Decomposition in Zone Sharing
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Hot-Spot Decomposition in Zone Sharing
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Hot-Spot Decomposition in Zone Sharing
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Hot-Spot Decomposition in Zone Sharing
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Hot-Spot Decomposition in Zone Sharing
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Hot-Spot Decomposition in Zone Sharing
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Hot-Spot Decomposition in Zone Sharing
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Hot-Spot Decomposition in Zone Sharing
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Hot-Spot Decomposition in Zone Sharing
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Hot-Spot Decomposition in Zone Sharing
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Storage Safety Requirement (1)
Pre-migration load (donor) >> post-migration load (receiver)
ldonor / (lmigrator + lreceiver) ≥ C1
C1 should be greater than or equal to 2 to make sure that the donor is really falling in a hot-spot
Evaluated by donor and receiver
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Storage Safety Requirement (2)
Post-migration load (migrator) >> pre-migration load (migrator)
T / lmigrator ≥ C2
C2 should be greater than or equal to 2 to avoid cyclic migrations
Applied solely by migrator
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Energy Safety Requirement (1)
Energy consumed (donor) << total energy (donor) T / edonor ≤ E1
E1 must be less than or equal to 0.5 Applied only by donor
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Energy Safety Requirement (2)
Energy consumed (migrator) << total energy (migrator)
(lmigrator + re * T) / emigrator ≤ E2
E2 must be less than or equal to 0.5 Applied only by migrator
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Energy Safety Requirement (3)
Energy consumed (receiver) << total energy (receiver)
lmigrator * re / ereceiver ≤ E3
E3 must be less than or equal to 0.5 Applied only by migrator
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Distributed Migration Criterion (DMC)
1. ldonor / (lmigrator + lreceiver) ≥ C1
2. T / lmigrator ≥ C2
3. T / edonor ≤ E1
4. (lmigrator + re * T) / emigrator ≤ E2
5. lmigrator * re / ereceiver ≤ E3
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Single-Hop Zone Sharing (SHZS)
Goal: Overall minimal changes to the original DIM
Single Hop Zone Sharing: A zone can be traded at most once Periodic exchange of neighbors information DMC applied locally by nodes No changes needed to GPSR
Applicability: Small Hot Spots
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Single-Hop Zone Sharing (SHZS)
Problems: Large hot-spots: overloaded neighbors
DMC hard to be satisfied Zone traded only once
nodes still in hot-spots after migration process Messages pass by original destination (donor) before
going to migrator energy consumption overhead
Solution: Allow a zone to be traded more than once
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Multi-Hop Zone Sharing (MHZS)
A zone can be traded more than once A new data structure: Traded Zoned List
Keeps track of the traded zones to redirect messages to their new destinations
An entry is composed of 3 values: (zone address, original owner, final owner)
GPSR changed to check the list first and update the destination field in the message
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Roadmap
Background Problem Statement: Storage Hot-spots Algorithms: Zone Sharing Experimental Results Conclusions
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Simulation Description
Compare: DIM, SHZS, and MHZS. Simulator similar to the DIM’s [Li et. al., SenSys’03]
Two phases: insertion & query. Insertion phase
Each sensor initiates 5 events Events forwarded to owners
Query phase Queries of sizes 10% to 100% of the attributes ranges
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Experimental Setup
Parameter Value
Network size 50 to 300 sensors
Initial energy 50 units
Energy unit energy needed to send one event
C1 & C2 2
E1 , E2 , and E3 0.3
Number of hot-spots 1
Hot-spot sizes (X,Y) 10% - 50% of the events (X)
falling into
10% of the attribute ranges (Y)
Sensor node storage capacity 15 units (events)
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Experimental Results: Data Persistence
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Network Size
DIM
SHZS
MHZS
Dropped Events for a network with a (50%, 10%) Hot-Spot
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Experimental Results: QoD
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Network Size
DIM
SHZS
MHZS
Result Size of a 50% Query for a network with a (50%, 10%) Hot-Spot
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Experimental Results: Load Balancing
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50 100 150 200 250 300
Network Size
DIM
SHZS
MHZS
Note: An overloaded node is a node reaching its max. capacity
Overloaded Nodes for a network with a (40%, 10%) Hot-Spot
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Experimental Results: Energy Consumption
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50 100 150 200 250 300
Network Size
DIM
SHZS
MHZS
Average Node Energy for a network with a (50%, 10%) Hot-Spot
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Conclusions
Contribution: A storage hot-spots decomposition scheme for DCS sensor nets Two versions: SHZS & MHZS
Experimental validation of its practicality Current ZS extensions:
Hot-spots incremental avoidance scheme (submitted for publication)
Possibility of ZS generalizations: Non-uniform loads for individual sensors Upper bound for ZS max. trading hops (nMHZS)
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Thank You
Questions ?
Advanced Data Management Technologies Labhttp://db.cs.pitt.edu