Date post: | 18-Jan-2016 |
Category: |
Documents |
Upload: | mae-fields |
View: | 215 times |
Download: | 0 times |
Computer Network Lab.
Integrated Coverage and Connectivity Configuration Integrated Coverage and Connectivity Configuration in Wireless Sensor in Wireless Sensor NetworksNetworks
SenSys’03
Xiaorui Wang, Guoliang Xing, Yuanfang Zhang, Chenyang Lu, Robert Pless, Christopher Gill
@Washington Univ.
Computer Network Lab.
ContentsContents
Introduction Coverage and connectivity
Relationship between connectivity and coverage Coverage and connectivity configuration
• Rc >= 2Rs• Rc < 2Rs
Experimentation Coverage configuration Coverage and communication performance System Life time
Conclusion
Computer Network Lab.
Introduction(1)Introduction(1)
Sensor network constraint : Energy Power saving mode
• Active and sleep scheduling General goal
• Minimize the number of active nodes
• Guarantee QoS
– Sensing coverage, network connectivity
Computer Network Lab.
Introduction(2)Introduction(2)
Sensing coverage Monitoring quality Different degree required by application Coverage requirement change Related with the number of faults to be tolerated
Connectivity Minimum number of node to be removed to partition the
graph• larger number greater connectivity
Redundant potential connectivity for fault tolerance Greater connectivity for communication bottleneck
Computer Network Lab.
Introduction(3)Introduction(3)
Past’s approach Separate approaches for each
New idea of this paper Analytic guarantee for Sensing coverage with effective
connectivity Dynamically configured degree of coverage
Computer Network Lab.
ProblemsProblems
Terminology Convex region A of a coverage degree of K
- every location inside A is covered by at least K nodes
Formulation of problem Given a coverage region A, and sensor coverage degree Ks Maximizing the number of nodes that are scheduled to sleep Under constraints
• A is at least Ks-covered
• All active nodes are connected
Computer Network Lab.
Relationship between connectivity and Relationship between connectivity and coveragecoverage
Depends on the ratio of the communication range to the sensing range
Not guarantee each other But can be handled by a configuration protocol if
Rc (Communication range) >= 2Rs (sensing range)
Computer Network Lab.
Sufficient condition for 1-coverage to imply connectivity (Theorem 1) A region is sensor covered, the sensors coverin
g that region are connected if• Rc >= 2Rs
Sufficient condition for 1 covered network to guarantee one-connectivity
Relationship between connectivity and Relationship between connectivity and coverage (2)coverage (2)
u v
x
y
Rs
2Rs <=
Not covered place
Computer Network Lab.
Relationship between connectivity and Relationship between connectivity and coverage (3)coverage (3)
Relationship between the degree of coverage and connectivity Boundary connectivity is Ks (Lemma 1) for a Ks-covered convex region A, it is possible t
o disconnect a boundary node from the rest of the nodes in the communication graph by removing Ks sensors if Rc >= 2Rs
* Removing Ks nodes disconnects a covered network
Computer Network Lab.
Relationship between connectivity and Relationship between connectivity and coverage (4)coverage (4)
Relationship between the degree of coverage and connectivity (cont’d) Tight lower bound on connectivity of communication graph is
Ks (Theorem 2) A set of nodes that Ks-cover a convex region A
forms a Ks connected communication graph if Rc >= 2Rs
* Disconnected network
Computer Network Lab.
Relationship between connectivity and Relationship between connectivity and coverage (5)coverage (5)
Relationship between the degree of coverage and connectivity (cont’d) Tight lower bound of Interior connectivity is 2Ks (Theorem 3) For a set of sensors that Ks-cover a convex reg
ion A, the interior connectivity is 2Ks if Rc >= 2Rs Two cases of disconnected situation of interior communicati
on
• First case
the void does not
merge with boundary
Computer Network Lab.
Relationship between connectivity and Relationship between connectivity and coverage (6)coverage (6)
• Second
the void merge
with boundary
Conclusion Boundary connectivity (for nodes located within Rs distance
to the boundary of the coverage region) Ks
the interior connectivity 2Ks
Computer Network Lab.
Coverage and connectivity configuration Coverage and connectivity configuration when Rc >= 2Rswhen Rc >= 2Rs
CCP Configuration protocol based on theorem 1, 2, 3 Can configure network to the specific coverage degree
requested by the application Decentralized protocol that only depends on local states of
sensing neighbors• Scalability enforcement
• Applications can change its coverage degree at runtime without high communication overhead
Guarantee degrees of coverage at the same time connectivity
Computer Network Lab.
Coverage and connectivity configuration Coverage and connectivity configuration when Rc >= 2Rs(1)when Rc >= 2Rs(1)
Ks-coverage Eligibility Algorithm For Determination to become active Example of Ks-eligibility
Computer Network Lab.
Coverage and connectivity configuration Coverage and connectivity configuration when Rc >= 2Rs(2)when Rc >= 2Rs(2)
Ks-coverage Eligibility Algorithm (Theorem 4) A convex region A is Ks-covered by a set of
sensors S if• Intersection points between sensors or between sensors and
A’s boundary exist in a region A
• All intersection points between any sensors are at least Ks-covered
• All intersection points between any sensor and A’s boundary are at least Ks covered
Computer Network Lab.
Coverage and connectivity configuration Coverage and connectivity configuration when Rc >= 2Rs(3)when Rc >= 2Rs(3)
Coverage patch S (same coverage area)
(conclusion of theorem 4) Region A is Ks covered• Coverage degree of a region coverage degree of all the
intersection points in the same region
Computer Network Lab.
Coverage and connectivity configuration Coverage and connectivity configuration when Rc >= 2Rs(4)when Rc >= 2Rs(4)
Ks coverage eligibility algorithm
/*intersection point*/
cf) SN(v) : active node within 2Rs range from v
Computer Network Lab.
Ks coverage eligibility algorithmKs coverage eligibility algorithm
Complexity (O(n^3)) Locations of all sensing neighbors required table of known sensing neighbors based on beacon from its co
mmunication neighbors Beacon message (HELLO)
Rc >= 2Rs• Its own location is included
Rc < 2Rs• Hidden node happens
Hidden node discovery Broadcast HELLO with TTL All known neighbor information in HELLO CCP case Trade off between beacon overhead and the number of active node
s maintained by CCP
Computer Network Lab.
State transition of CCPState transition of CCP
Listen
Sleep Active
Periodically change 1. Ineligible
2. Listen timer expiration
Eligible & join timer expiration
Ineligible & Withdraw
timer Expiration
Eligible
Computer Network Lab.
Coverage and connectivity configuration Coverage and connectivity configuration when Rc < 2Rswhen Rc < 2Rs
Does not guarantee connectivity by CCP Integration of CCP with SPAN SPAN
Decentralized coordination protocol for energy consumption while maintaining a communication backbone composed by active nodes
CCP eligibility rule guarantee the coverage, and for connectivity, SPAN eligibility rule is adapted
Computer Network Lab.
ExperimentationExperimentation
On Coverage Simulator (CS) Coverage configuration - Ottawa protocol vs. CCP
Efficiency of CCP The configurability of CCP
Coverage and communication performance System life time
Computer Network Lab.
Efficiency of CCPEfficiency of CCP
Average coverage degree (Ks =1)
Computer Network Lab.
Efficiency of CCPEfficiency of CCP
Distribution of coverage degree Comparison of active node number
CCP eligibility rule can preserve coverage with fewer active nodes
Computer Network Lab.
The Configurability of CCPThe Configurability of CCP
Coverage degree vs. required coverage degree
Irrespective of # of nodes
Average/min decrease as required degree
increase
Computer Network Lab.
Coverage and communication Coverage and communication performance performance
Simulation Environment NS-2 with CMU wireless extensions 802.11 MAC layer with power saving support 400*400m2 coverage region with 160 nodes randomly distributed 10 sources and 10 sinks in opposite sides of the region with CBR flow to de
stination node (128byte packets with 3Kbps) 2Mbps bandwidth and a sensing range of 50m TwoRayGround radio propagation model Requested coverage degree Ks = 1
Comparison protocols SPAN CCP SPAN+CCP CCP-2Hop SPAN+CCP-2Hop
Computer Network Lab.
Coverage and communication Coverage and communication performanceperformance
SPAN CCP SPAN-CCP-2Hop
Network topology and coverage in a Typical run (Rc/Rs = 1.5)
Medium size dots : sink and source at opposite sides
Large size dots : active nodes
Computer Network Lab.
Coverage and communication Coverage and communication performanceperformance
Coverage degree vs. Rc/Rs Packet delivery ratio vs. Rc/Rs
Connectivity cannot guarantee coverage
Computer Network Lab.
Coverage and communication Coverage and communication performanceperformance
Number of active nodes vs. Rc/Rs
Computer Network Lab.
System life timeSystem life time
Lifetime goes up if many factors can be controlled SPAN + CCP
Coverage lifetime, communication lifetime Until ratio’s dropping below the threshold (90%)
Computer Network Lab.
System life timeSystem life time
System coverage life time System communication life time
Computer Network Lab.
ConclusionConclusion
Coverage efficiency One coverage with smaller number of active nodes than OTTAWA Irrespective of node density
Coverage configuration Effectively enforcement of different coverage degrees Active node proportional to requested coverage degree
Integrated coverage and connectivity configuration Rc>=2Rs
• Good performance with CCP
Rc<2Rs• SPAN + CCP-2Hop : most effective protocol for communication and co
verage