QoS support and energy efficiency Pascale Minet

1. QoS support and energy efficiency Pascale Minet November 2007

2. QoS support in MANETs Problem State of the art QoS OLSR Principles Performance evaluation

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4. QoS Amateur de jeux Jouer Audio temps réel Surfeuse Texte interactive Naviguer Email Instantaneous bandwidth Consommateur audio Consommateur vidéo Flux audio Flux vidéo QoS support in wireless ad hoc networks bandwidth, delay or priority requirements

5. QoS support: the problem • Multimedia applications have QoS requirements • Throughput • Delay • Priority • Without QoS support, OLSR can fail to find a route providing the requested bandwidth/delay, even if it exists. • Assuming that interferences are limited to 2 hops, a node can be impacted 5 times by the transmission of a flow packet Flow CBR at 100kbps 1 2 4 5 3 6

6. QoS support: complexity results • Finding a path between a source and a destination maximizing the probability of meeting the requested end-to-end delay is NP-hard [Jacquet, Naimi, Rodolakis] • Finding a path between a source and a destination providing the requested bandwith is NP-hard because of radio interferences [Allard, Jacquet, Mans]

7. QoS support: state of the art • BRUIT [Chaudet et al.] is the first bandwidth reservation protocol dealing with interferences • Is used with reactive routing protocols [Sarr et al] • INSIGNIA [Lee et al.] is the adaptation of the IntServ approach to MANETs • Maintains per flow info, uses a bandwidth reservation protocol, is not scalable • SWAN [Ahn et al.] is the adaptation of the DiffServ approach to MANETs • Maintains per class info • [Xu et al.] A scalable approach used with LANMAR routing • Cross-layering approach is generally adopted [Nahrsted et al] • XIAN [Ayache et al.] and [Pau et al.] for 802.11 • [Iannone et al.] for wireless mesh networks 1 2 4 5 3 6 Admission control Rate Control Marker QoS Routing BW estim. MAC layer

8. QoS support: state of the art • Evaluation of QoS metrics • Active versus passive probing of link capacity [Kapoor et al.] • End-to-end capacity of a path [Chen et al.] • Local available bandwidth [Nahrsted et al.] • QoS routing: choice of QoS metrics • Available bandwidth [Xu et al.], [Lee et al.], [Ahn et al.], [Badis et al.] • Delay [Badis et al.], [Jacquet et al.] • Loss [Fdida et al.]

9. QoS OLSR: the principles Application (Bandwidth) • [Nguyen, Minet] • Takes interferences into account • Allows various QoS requirement • - Bandwidth requirement • - High priority processing • Uses different mechanisms • - QoS signaling • - QoS routing • - Admission control • Interference aware Class QoS Bandwidth Controlon the path Path Computation QoS Advertisements MAC layer metrics

10. QoS OLSR: the principles Application (Bandwidth) Class QoS Marking Routing on theFixed Path

11. QoS OLSR: the principles • QoS support is interference aware • Admission control • QoS flows • the acceptance of the new flow does not compromize the QoS of already accepted QoS flows • a route meeting the requested bandwidth can be found • BE flows • they share the bandwidth left by QoS flows • they are shaped by a leaky bucket

12. QoS OLSR: the principles • QoS Routing • QoS flows • are routed on a fixed path • the shortest path meeting the requested bandwidth • this path is updated in case of link breakage or shortest path • BE flows • are routed hop by hop on the shortest path

13. QoS OLSR: the principles • QoS Signaling • Provides information about: • the available bandwidth • the bandwidth used by QoS flows • The Hello message sent by a node N contains: • the available bandwidth at node N • the available bandwidth at any neighbor node • The TC (Topology Control) message originated from a node N contains: • the minimum available bandwidth in a 2-hop area from N • the available bandwidth of its MPR selectors • Uses two types of MPRs • the classical ones to optimize network flooding • the QoS MPRs to build routes

14. QoS MPRs versus MPRs • For a 2-dimension network with average density n, the average number of neighbors selected as: • MPRs is in O(n1/3). • QoS MPRs is in O(n1/3xlog n). • Average number of retransmissions of a flooded message QoS MPRs MPRs

15. MANET OLSRv11 / IPv4&IPv6 / 802.11b (with QoS & Security stacks) N T408 T403 MANET = Mobile Ad-hoc NETwork 2 GTW INSC Indoor & Urban fighting scenario 2010:3:504::auto/48 6 HIPERCOM 10 T303 7 O235 T205 10 3 8 O219 O215 4 9 T203 11 South Parking behind Tower = 5dBi WiFi2.4 GHz omni antenna = MANET demonstration node with applications ALGECO 14 = supervision wired Ethernet access MANET «  wireless Backbone » nodes = Radio direct Link 5 1 12

16. QoS OLSR on the CELAR platform R23 Path without QoS R02 Path with QoS R06 R07 QoS support is interference aware VAIO11 R03 R08 R09 R10 VAIO12 R05 R04 R01

17. QoS OLSR on the CELAR platform R23 R02 R06 R07 VAIO11 R03 R08 R09 R10 VAIO12 R05 R04 R01 Improves the throughput obtained by QoS flows

18. QoS support: conclusion • A good accuracy between simulation results and measures • Confrontation on the real platform of CELAR • The users of QoS flows perceive a better QoS • An increased throughput • A better delivery rate • QoS flows have more stable routes • Less error rate • Shorter delays and jitters • A good usage of network resources • Optimized flooding • Congested areas are avoided • Supports mobility

19. Energy Efficiency Energy efficient routing Problem State of the art Proposed solution Node activity scheduling Problem State of the art SERENA

20. Energy efficiency: Introduction • Goal: to maximize network lifetime • Four classes of solutions Topology Control Reducing the Volume of info Node Activity Scheduling Energy Efficient Routing

21. Distribution of node energy consumption • Parameters • Power values for the 802.11b • Density: 10 • Interference = 2 x radio range • Bandwidth: 2Mb/s • Initial energy : 100 Joules • 30 point-to-point flows of 16 Kb/s • The highest parts of energy are lost in the Idle and Interference states

22. Energy efficient routing: state of the art • Energy consumed by the transmission of a packet • Transmitter + Receiver + Overhearing + Interferences • Cost(transmission by i) = Etrans + n * Ercv • [Feeney et al] & [Shresta et al.] overhearing and interferences • Multipath routing • Load sharing [Sha et al.] • Maintaining two paths is generally sufficient [Srinivas et al.] [Nasipuri et al.] • For reactive protocols [Lee et al.] • Hop-by-hop routing • Selection of the path consuming the minimum energy [Kwon et al.] • Selection of the path visiting nodes with the highest residual energy [Hassanein et al.] • Hybrid protocols: [Shresta et al.]

23. Energy efficient routing: the problem Flow CBR at 16 kbps 1 2 4 5 3 6 • Energy consumed by the end-to-end transmission of a packet • Cost(transmission by i) = Etrans + n * Ercv • Cost(end-to-end transmission) = • Interferences make the energy efficient routing problem NP-hard • Finding a path between a source and its destination such that any node has sufficient residual energy is NP-hard [Mans et al.]. • Result is still true if interferences are limited to a single hop [Mans et al.].

24. Energy efficient routing: a solution [Mahfoudh, Minet] • Principles • Is based on OLSR • Minimizes the energy consumed by the end-to-end transmission of a packet • Avoids nodes with a low residual energy • Reduces the overhead • How it works • Selects two types of multipoint relays • Those used to optimize network flooding • Classical MPRs • Those used to build energy efficient routes • EMPRs take into account the residual energy of the candidate node and its 1-hop neighbors • Computes the route minimizing the energy consumed, built from the EMPRs

25. Energy efficient routing: performance evaluation • Cost(path) = energy consumed by the end to-end transmission of a packet • Nodes with low residual energy are avoided: not selected as EMPRs • Comparison of different routing strategies • Multipath source routing: for load sharing • Two paths with disjoint links DL or nodes DN are computed by the source • Adaptative hop-by-hop routing: RE • Each node forwards the packet to the next hop on the path of minimum cost D S

26. Energy efficient routing: a solution • Reduced overhead • Maximized network lifetime

27. Distribution of node energy consumption with RE • Energy efficient routing => less energy dissipated in interferences and overhearing

28. Energy efficiency: Introduction • Goal: to maximize network lifetime • Four classes of solutions Topology Control Reducing the Volume of info Node Activity Scheduling Energy Efficient Routing

29. Node activity scheduling: the problem • The sleep mode is the state consuming the least energy • Power values for 802.11b • Requirements • Transmitting a packet to a sleeping neighbor is energy wasteful • Application functionalities must be ensured A coordination of nodes is required

30. Node activity scheduling: state of the art • Solutions building the active nodes set • Centralized solutions with disjoint active sets [Cardei et al.] or not [Cardei et al.] • Distributed solutions based on connected dominating sets [Simplot et al.] • Deterministic slot based solutions • 802.15.4 • in beacon-enabled mode all nodes can sleep • In non-beacon mode, only non-router nodes can sleep • TRAMA [Rajendran et al.] • Neighborhood discovery + schedule exchange + adaptive election selecting the transmitter and receiver for each time slot • Complex • FLAMA [Rajendran et al.] • Designed for data gathering applications • Based on a tree structure

31. SERENA: SchEduling RoutEr Nodes Activity [Mahfoudh, Minet] • Requirements • Distributed and localized • At least one time slot guaranteed to each node • Adaptative to node traffic rates and late arrivals • Simple and fast • Efficient with a small overhead • Principles • Any node must be awake in the slots where: • it transmits • one of its one-hop neighbor transmits • It sleeps the remaining time • Two distributed algorithms: • Two-hop coloring • Slot assignment based on colors

32. SERENA • Distributed and localized algorithm • Node N must know information from its neighborhood up to 2 hops, Ω2(N) • Priority(N) = Node identifier is used to break ties • Two-hop coloring • Color all nodes in the network using the smallest number of colors and such that two nodes having the same color are at a distance > 2 hops • Has been shown NP-hard • Any nodeN takes a color iff all nodes in Ω2(N) with a higher priority are already colored, the color taken is the smallest color unused in Ω2(N)

33. SERENA: two-hop coloring • Requires a small number of rounds • Uses a small number of colors = SERENA = SERENA

34. SERENA: slot assignment • Spatial reuse • Each node N receives the slot corresponding to its color • Each node N receives k additional slots proportionally to its traffic rate • Same rule as color assignment

35. SERENA: slot assignment and traffic rate

36. SERENA performance • maximizes network lifetime • increases the volume of data delivered Without SERENA With SERENA Without SERENA With SERENA

37. SERENA improves energy efficiency • Distribution of node energy consumption SERENA decreases the amount of energy lost in Idle and Interference states,