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 [s i,t i ]  Transmission cost: T(i) = |I i | × hc(i) × E t 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 s i = 0. w(S, i) = hc(i). o Edges going to T: (i, T) ∈ E if i ∈ C and t i = 360. w(i, T) = 0 o Edges linking nodes in C: (i, j) ∈ E if s i < s j ≤ t i and t i < t j. w(i, j) = hc(j)

Angle coverage -6- Csc8980 – Fall 2008 Properties  Property 1: If S → n1 → n2 → · · · → nk → T is a path in G C, {n 1, n 2,..., n k } is a cover in C.  Property 2: The cost of path S → n 1 → n 2 → · · · → n k → T in G C is the cost of cover {n 1, n 2,..., n k } 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 G C.  Using Dijsktra’s algorithm

Angle coverage -8- Csc8980 – Fall 2008 Simulation

Angle coverage -9- Csc8980 – Fall 2008 Simulation