1. SERENA: SchEduling RoutEr Nodes Activity in wireless ad hoc and sensor networks Pascale Minet and Saoucene Mahfoudh INRIA, Rocquencourt 78153 Le Chesnay Cedex, France IWCMC 2008

2. 2 Outline Introduction The Proposed Solution: SERENA  Distributed Coloring  Time Slot Assignment  Late Node Arrivals and Node Mobility  Integration with an Energy Efficient Routing Conclusion

3. 3 Introduction Sleeping:  the radio is turned off, no communication is possible. The node uses P sleep that is largely smaller than any other power. Idle:  even when no messages are being transmitted over the medium, the nodes stay idle and keep listening the medium with P idle ; Transmitting:  node is transmitting a frame with transmission power P transmit ; Receiving:  node is receiving a frame with reception power P receive. This frame can be decoded by this node or not, it can be intended to this node or not. Lucent silver wavelan PC card

4. 4 Introduction A. Sleeping nodes  extend network lifetime by dividing the network nodes in sets Centralized Distributed and localized

5. 5 Introduction B. Centralized and distributed one-hop coloring  coloring nodes with the minimum number of colors such that two adjacent nodes have not the same color Centralized Distributed [10] Distributed Largest First (DLF)  the number of colors needed to color a graph G  its time complexity, expressed in the case of a distributed algorithm, by the maximum number of rounds needed to color each node

6. 6 Introduction [10] Distributed Largest First (DLF)  A round is such that every node can: send a message to all its one-hop neighbors, receive the messages sent by them, perform some local computation based on the information contained in the received messages.

7. 7 Introduction C. Slot assignment algorithms  [14] Probabilistic algorithms  TRAMA [12] FLAMA [13] the number of slots allocated to a node depends on the number of colors seen by this node (i) each node is guaranteed to receive at least one slot (ii) the number of slots granted to a node depends on its traffic rate

8. 8 The Proposed Solution: SERENA Goal  maximize network lifetime by allowing router nodes to sleep, while ensuring end-to-end communication

9. 9 The Proposed Solution: SERENA The solution must meet the following requirements:  distributed and localized  fair: each node is ensured to receive at least one time interval to transmit  adaptive to traffic rates: nodes with high traffic will receive more than one time interval, if possible  adaptive to late node arrivals  simple, quick to converge  efficient (node throughput), low overhead

10. 10 The Proposed Solution: SERENA Distributed Coloring A. Two-hop coloring algorithm  two distinct router nodes at a distance up to two hops have distinct colors  the number of colors used is as small as possible  the algorithm is distributed and localized to limit the overhead

11. 11 The Proposed Solution: SERENA Distributed Coloring Rule RC1: For any node N, if all nodes in N 2 (N), with a higher priority than N, have a color assigned, N selects the color that is the smallest color unused in N 2 (N). Rule RC2: Each node N sends to its one-hop neighbors, a message containing its identifier, its priority, its color if already assigned, its list of neighbors and the list of colors already used by them.

12. 12 The Proposed Solution: SERENA Distributed Coloring B. Performance evaluation  Distributed Largest First (DLF) [10]  The first one is based on the node identifier  The second one is based on the cardinality of N 2 (N) Network density is fixed to 10

13. 13 The Proposed Solution: SERENA Distributed Coloring B. Performance evaluation  Distributed Largest First (DLF) [10]  The first one is based on the node identifier  The second one is based on the cardinality of N 2 (N) 100 nodes, Network density varying from 5 to 20

14. 14 The Proposed Solution: SERENA Time Slot Assignment A. Principles A node N enters the time slot assignment algorithm as soon as it is colored as well as all nodes in N 2 (N) Let Size denote the number of slots in the frame Size is set to 2 ∗ 4 ∗ density  density denotes the average number of nodes in the transmission range

15. 15 The Proposed Solution: SERENA Time Slot Assignment Rule RS1: Each node has one reserved slot depending on its color. This slot is guaranteed to the node, whatever its traffic rate. 1 2 3 4 5 Slot

16. 16 The Proposed Solution: SERENA Time Slot Assignment Rule RS2: If all nodes in N 2 (N) with a higher priority than N have selected their additional slots, node N selects its additional slots among the available slots. Their number is equal to k’, with: Size is the size of the frame |VisibleColor(N)| denotes the cardinal of the set of colors visible by N up to two-hop. traffic(N) is the bandwidth request of node N traffic(i) denotes the highest bandwidth request of nodes having color i up to two-hop from N

17. 17 The Proposed Solution: SERENA Time Slot Assignment Slot 1 2 3 4 5 6

18. 18 The Proposed Solution: SERENA Time Slot Assignment Rule RS3: If all nodes succeed in selecting their k additional slots, the algorithm is over. Otherwise, let N a node that fails to assign its k slots, it requisitions k slots among the requisitionable ones in N 2 (N), with The requisitionable slots of a node are constituted by its additional k’ − k slots. Each node has the guarantee to obtain at least k+1 slots It is possible to obtain k’+1 slots

19. 19 The Proposed Solution: SERENA Time Slot Assignment Rule RS4: The message sent by a node N in its one-hop neighborhood contains its identifier, its priority, its color, its bandwidth request, its list of slots if already assigned, with the indication whether the slot is requisitionable or not, and for each of its one-hop neighbors: its identifier, its priority, its color, its bandwidth request and its list of slots if already assigned, the indication whether the slot is requisitionable or not. B. Adaptivity to traffic changes and optimizations Rule RS5: The time slot assignment algorithm is run periodically.

20. 20 The Proposed Solution: SERENA Time Slot Assignment Three important features of this algorithm:  No node starvation: minimum throughput guaranteed to a node is equal to Bandwidth/Size  Node fairness  Adapt to varying traffic rates

21. 21 The Proposed Solution: SERENA C. Performance evaluation The frame size is set to 2 ∗ |N 2 (N)| slots

22. 22 The Proposed Solution: SERENA

23. 23 The Proposed Solution: SERENA

24. 24 The Proposed Solution: SERENA Late Node Arrivals and Node Mobility A. Assumptions  a high majority of nodes are present initially,  topology changes are limited,  mobility is also limited: only a few nodes can move and their speed is slow,  the maximum number of nodes up to two hops is known. B. General case

25. 25 The Proposed Solution: SERENA Integration with an Energy Efficient Routing EOLSR  SERENA is combined with a routing efficient strategy, based on the OLSR routing protocol [16] Nodes ranges from 50 to 200 The initial energy of nodes is randomly chosen in the interval [50, 100] Joules Network throughput is set to 2Mbps User traffic consists of 10 flows, with randomly chosen sources and destinations, and a throughput of 4 Kbps The slot size is fixed to 8ms and the frame consists of 80 slots  The frame size is equal to 2 ∗ 4 ∗ density slots

26. 26 The Proposed Solution: SERENA Integration with an Energy Efficient Routing For 100 nodes, the lifetime increase reaches 420% the increase in the volume of user data delivered reaches 404%

27. 27 The Proposed Solution: SERENA Integration with an Energy Efficient Routing First, SERENA considerably reduces the time spent in the idle state. Second, SERENA reduces the energy losses due to interferences

28. 28 Conclusion This paper propose SERENA to maximize network lifetime in wireless and sensor networks Simulation results show the benefits brought by SERENA:  network lifetime is maximized  the amount of user messages delivered is increased proportionally to the network lifetime

29. 29 Thank you