Achieving 360 Angle Coverage with Minimum Transmission Cost in Visual

Sensor Networks

By K.Y Chow, K.S Lui, E.Y Lam

Instructor: Dr. Yinghsu Li

Presented by: Chinh Vu

Angle coverage -2- Csc8980 – Fall 2008

Problem definition

Tracking system: an object moves around the network.

Problem: Require full image of object at all time.

Each camera has particular capturing direction (not omni-directional)

Angle coverage -3- Csc8980 – Fall 2008

Transmission cost

Capture Range

o Range [si,ti]

Transmission cost:

T(i) = |Ii| × hc(i) × Et

o I: Image size

o hc: Hop Count

o E: Energy to transmit a bit

Angle coverage -4- Csc8980 – Fall 2008

Minimum Cost Cover prob.

Find subset of sensor M s.t:

Example: 1,2,3,4,7,8 is a MCC.

Angle coverage -5- Csc8980 – Fall 2008

Minimum cost path transformation

Given set of sensors C

Add two new nodes S (source) and T (destination).

Construct GC=(V,E) where V=C U {S,T}, and E comprises of

o Edges starting from S: (S, i) ∈ E if i ∈ C and si = 0. w(S, i) = hc(i).

o Edges going to T: (i, T) ∈ E if i ∈ C and ti = 360.

w(i, T) = 0

o Edges linking nodes in C: (i, j) ∈ E if si < sj ≤ ti and ti < tj. w(i, j) = hc(j)

Angle coverage -6- Csc8980 – Fall 2008

Properties

Property 1: If S → n1 → n2 → · · · → nk → T is a path in GC ,

{n1, n2, ..., nk} is a cover in C.

Property 2: The cost of path S → n1 → n2 → · · · → nk → T in

GC is the cost of cover {n1, n2, ..., nk} in C.

Property 3: If M is a cover without redundant node (cover that all nodes are necessary to maintain the coverage requirement), then the nodes in M, in ascending order of starting angle, form a path from S to T.

Angle coverage -7- Csc8980 – Fall 2008

Lemma

Lemma 1: If M is a minimum cost cover in C, then the nodes in M form a minimum cost path from S to T in GC.

Lemma 2: M is a minimum cost cover in C if the nodes in M form a minimum cost path from S to T in GC.

M is a minimum cost cover in C if and only if the nodes in

M form a minimum cost path from S to T in GC.

Using Dijsktra’s algorithm

Angle coverage -8- Csc8980 – Fall 2008

Simulation

Angle coverage -9- Csc8980 – Fall 2008

Simulation