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Department of Information Engineering University of Padova, ITALY

Department of Information Engineering University of Padova, ITALY. Special Interest Group on NEtworking & Telecommunications. On Providing Soft-QoS in Wireless Ad-Hoc Networks. Andrea Zanella, Daniele Miorandi, Silvano Pupolin, Paolo Raimondi.

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Department of Information Engineering University of Padova, ITALY

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  1. Department of Information EngineeringUniversity of Padova, ITALY Special Interest Group on NEtworking & Telecommunications On Providing Soft-QoS in Wireless Ad-Hoc Networks Andrea Zanella, Daniele Miorandi, Silvano Pupolin, Paolo Raimondi {andrea.zanella, daniele.miorandi, silvano.pupolin}@dei.unipd.it WPMC 2003, 21-22 October 2003 Yokosuka, Kanagawa (Japan) 21-22 October 2003

  2. Motivations • Ad-hoc networks are a valuable solution to • Extend in a multi-hop fashion the radio access to wired networks • Interconnect wireless nodes without any fixed network structure • In these contexts, providing QoS is a key issue • audio/video streaming • interactive games • multimedia • A possible QoS support method • QoS-routing & Call-Admission-Control (CAC) mechanisms • Constrained Shortest Path Routing Problem (NP-complete) • MAC-layer Resource Reservation (MRR) and scheduling strategies Yokosuka, Kanagawa (Japan) 21-22 October 2003

  3. Widely used in wired networks Integrated Services: flow based (RSVP) Differentiated Services: class based Suitable for wireless networks Applications may work even if, for short periods of time, QoS requirements are not satisfied Deals with limited bandwidth and radio channel Hard & Soft QoS Hard-QoS Soft-QoS Yokosuka, Kanagawa (Japan) 21-22 October 2003

  4. Aim of the study • Reference network scenario • Low-profile multi-hop wireless networks • Intermediate nodes capable of basic functionalities • Routing – Link monitoring – Basic computation • Border nodes capable of rather complex functionalities • Call Admission Control (CAC) – MAC layer Resource Reservation (MRR) • Goal • Providing Soft-QoS support over low-profile multi-hop networks • DefineSoft QoS parameters • Define distributed statistical CAC • Define statistical MAC-layer Resource Reservation (MRR) mechanism • Modify AODV in order to support Soft-QoS routing Yokosuka, Kanagawa (Japan) 21-22 October 2003

  5. What’s Soft-QoS? Soft-QoS definition Yokosuka, Kanagawa (Japan) 21-22 October 2003

  6. Soft-QoS parameters • QoS parameters required per link • Minimum peak band: Br • End-to-End Delay: Dr • Soft QoS parameter: Target Satisfaction index • r = percentage of pcks expected to satisfy QoS constrains • r = 1  hard QoS (or “wealthy” clients) • r = 0  pure best-effort (or “poor” clients) Yokosuka, Kanagawa (Japan) 21-22 October 2003

  7. Call Admission Control Distributed CAC mechanism Yokosuka, Kanagawa (Japan) 21-22 October 2003

  8. Path Service Levels • Path: P = (p1,…, pN) • Service levels: • Path Peak Bandwidth • Path Delay Yokosuka, Kanagawa (Japan) 21-22 October 2003

  9. CAC & Gaussian approx • Path is feasible if • Bandwidth constrained requests • Delay constrained requests • This would require the collection of the complete statistics of link bandwidth and delay… but we may (always?) resort to the Gaussian approximation • Statistics are univocally determined by mean and standard deviation values • Bandwidth constrained requests • Delay constrained requests Yokosuka, Kanagawa (Japan) 21-22 October 2003

  10. MRR Statistical MAC-layer Resource Reservation Yokosuka, Kanagawa (Japan) 21-22 October 2003

  11. Bandwidth Margins • Resource bounds • Minimal residual resources that should be guaranteed to preserve QoS levels of accepted connections • Bandwidth-constrained requests Yokosuka, Kanagawa (Japan) 21-22 October 2003

  12. Delay Margins • Delay-constrained requests • Extra-delay margin is computed for the entire path • Each link along the path is assigned a fraction of the extra delay time inversely proportional to the average link delay Yokosuka, Kanagawa (Japan) 21-22 October 2003

  13. Maximum Sustainable traffic • Before a connection request is accepted the tightest resource margins among the nodes along the path are made available at the source • From these bounds, the source derives the maximum sustainable traffic rate, i.e., the maximum traffic that can be injected into the network without violating the QoS agreements of the connections already established Yokosuka, Kanagawa (Japan) 21-22 October 2003

  14. How to create a path Soft-QoS routing algorithm Yokosuka, Kanagawa (Japan) 21-22 October 2003

  15. Path creation & maintenance • Soft-QoS routing is largely inspired to AODV • Each Route Request (RREQ) packet gathers statistical information on the minimum bandwidth and maximum delay along that portion of the path • RREQ is propagated only whether bandwidth request is satisfied • The destination node back propagates a Route Reply (RREP) packet along the selected path • RREP acquaints intermediate nodes with new resource bounds and updates maximum sustainable traffic rate limit • Source node is required to respect the maximum sustainable traffic rate limit or to refuse the connection Yokosuka, Kanagawa (Japan) 21-22 October 2003

  16. Simulation Results Simulation of Soft-QoS routing algorithm Yokosuka, Kanagawa (Japan) 21-22 October 2003

  17. Bluetooth Scatternet Round Robin Polling Gateways spend 50 slots in each piconet Poisson packets arrival process Mixed packet formats with average length of 1500 bits Delay-constrained requests Simulation Scenario Yokosuka, Kanagawa (Japan) 21-22 October 2003

  18. Local slave-to-slave connections in each piconet Data rate=9.6 Kbit/s Gaussian Approximation • 1 hop • 6 hops • Gaussian approx is fairly close to empirical delay CDF • Gap increases for long-distance and high traffic connection Yokosuka, Kanagawa (Japan) 21-22 October 2003

  19. Simulation setup • Target connection c1 • Dr = 50 ms • r = 0.2 • r = 20 kbit/s • Target connection c2 • Dr = 200 ms • r = 0.9 • r = 30 kbit/s • Target connection c3 • Dr = 200 ms • r = 0.9 • r = 20 kbit/s • Target connection c4 • Dr = 50 ms • r = 0.2 • r = 60 kbit/s • Transversal connections • Starting after 20 s, last for 10 s • On average 1 request/s • Random source, destination & QoS requests • Rate: 520 kbit/s Yokosuka, Kanagawa (Japan) 21-22 October 2003

  20. Satisfaction & Delay dynamics • Satisfaction • Delay Yokosuka, Kanagawa (Japan) 21-22 October 2003

  21. Conclusions • We have proposed a basic Soft QoS routing algorithm for low-profile ad hoc networks • Provides Soft-QoS guarantees • Requires • basic nodes’ functionalities • statistical link state monitoring (mean and standard deviation) • Does not require • service differentiation • static resource reservation • Drawbacks • Lower resource utilization • Higher rate of connection request rejection Yokosuka, Kanagawa (Japan) 21-22 October 2003

  22. Department of Information EngineeringUniversity of Padova, ITALY On Providing Soft-QoS in Wireless Ad-Hoc Networks Andrea Zanella, Daniele Miorandi, Silvano Pupolin, Paolo Raimondi Questions? Yokosuka, Kanagawa (Japan) 21-22 October 2003

  23. Extra Slides… Spare Slides Yokosuka, Kanagawa (Japan) 21-22 October 2003

  24. Bandwidth-constrained Delay-constrained Extra-delay margin given to each link along the path is inversely proportional to the mean link delay Statistical Resource Reservation • Resource bounds • Minimal residual resources that should be guaranteed to preserve QoS levels of accepted connections Resource bounds Actual Satisfaction Yokosuka, Kanagawa (Japan) 21-22 October 2003

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