Instructor: Dr. Yinghsu Li Presented by: Chinh Vu

1. Achieving 360 Angle Coverage with Minimum Transmission Cost in Visual Sensor NetworksBy K.Y Chow, K.SLui, E.Y Lam Instructor: Dr. Yinghsu Li Presented by: Chinh Vu

2. 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)

3. Transmission cost • Capture Range • Range [si,ti] • Transmission cost: T(i) = |Ii| × hc(i) × Et • I: Image size • hc: Hop Count • E: Energy to transmit a bit

4. Minimum Cost Cover prob. • Find subset of sensor M s.t: • Example: 1,2,3,4,7,8 is a MCC.

5. 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 • Edges starting from S: (S, i) ∈ E if i ∈ C and si= 0. w(S, i) = hc(i). • Edges going to T: (i, T) ∈ E if i ∈ C and ti= 360. w(i, T) = 0 • Edges linking nodes in C: (i, j) ∈ E if si< sj≤ tiand ti< tj. w(i, j) = hc(j)

6. 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 GCis 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.

7. 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

8. Simulation

9. Simulation