WPMC 2003 Yokosuka, Kanagawa (Japan) October 2003 Department of Information Engineering University of Padova, ITALY On Providing Soft-QoS in Wireless Ad-Hoc Networks A note on the use of these ppt slides: We’re making these slides freely available to all, hoping they might be of use for researchers and/or students. They’re in PowerPoint form so you can add, modify, and delete slides (including this one) and slide content to suit your needs. In return for use, we only ask the following: If you use these slides (e.g., in a class, presentations, talks and so on) in substantially unaltered form, that you mention their source. If you post any slides in substantially unaltered form on a www site, that you note that they are adapted from (or perhaps identical to) our slides, and put a link to the authors webpage: Thanks and enjoy!

WPMC 2003 Yokosuka, Kanagawa (Japan) October 2003 Department of Information Engineering University of Padova, ITALY On Providing Soft-QoS in Wireless Ad-Hoc Networks {andrea.zanella, daniele.miorandi, Andrea Zanella, Daniele Miorandi, Silvano Pupolin, Paolo Raimondi WPMC 2003, October 2003 Special Interest Group on NEtworking & Telecommunications

WPMC 2003 Yokosuka, Kanagawa (Japan) October 2003 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

WPMC 2003 Yokosuka, Kanagawa (Japan) October 2003 Hard & Soft QoS  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-QoS Soft-QoS

WPMC 2003 Yokosuka, Kanagawa (Japan) October 2003 Aim of the study  Reference network scenario  Low-profile  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 Soft-QoS  Providing Soft-QoS support over low-profile multi-hop networks Soft QoS Define Soft QoS parameters distributed statistical CAC Define distributed statistical CAC statistical MAC-layer Resource Reservation (MRR) mechanism Define statistical MAC-layer Resource Reservation (MRR) mechanism AODV Modify AODV in order to support Soft-QoS routing

WPMC 2003 Yokosuka, Kanagawa (Japan) October 2003 What’s Soft-QoS? Soft-QoS definition

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

WPMC 2003 Yokosuka, Kanagawa (Japan) October 2003 Call Admission Control Distributed CAC mechanism

WPMC 2003 Yokosuka, Kanagawa (Japan) October 2003 Path Service Levels  Path: P = (p 1,…, p N )‏  Service levels:  Path Bandwidth: minimum available bandwidth along the path  Path Delay: total delay introduced by the path  Bandwidth b pj and delay d pj of each link are assumed to be (independent) random variables B P & D p are random variables!

WPMC 2003 Yokosuka, Kanagawa (Japan) October 2003 Call Admission Control  Path is feasible if  Bandwidth constrained requests  Delay constrained requests  However, this would require the collection of the complete statistics of link bandwidth and link delay…

WPMC 2003 Yokosuka, Kanagawa (Japan) October 2003 Gaussian approx Gaussian approximation!  But when statistics are tough to be determined… we may (always?) resort to the Gaussian approximation!  Statistics are univocally determined by mean and standard deviation values of link delay and available bandwidth  Such values can be easily determined by each intermediate node  QoS routing algorithm collects and delivers such statistics to the destination node  Destination node performs CAC in a straightforward manner:  Bandwidth constrained requests  Delay constrained requests

WPMC 2003 Yokosuka, Kanagawa (Japan) October 2003 MRR Statistical MAC-layer Resource Reservation

WPMC 2003 Yokosuka, Kanagawa (Japan) October 2003  Once a connection is accepted, resources should be reserved…  To avoid complex static reservation mechanisms and flow differentiation we resort to statistical resource reservation:  Each node processes all the packets in the same way  Packets of different flows get the same service from the same link  For each link, nodes compute the Resource Bounds, i.e., the minimal residual resources that should be guaranteed to preserve QoS levels of accepted connections that go through that link Resource Bounds

WPMC 2003 Yokosuka, Kanagawa (Japan) October 2003 Example of Bandwidth bound Bandwidth B P(b j > B)‏ Target Satisfaction Index  r Required Path Bandwidth B r Actual Sat. Index  Bandwidth Bound

WPMC 2003 Yokosuka, Kanagawa (Japan) October 2003 Bandwidth Bounds  Bandwidth-constrained requests

WPMC 2003 Yokosuka, Kanagawa (Japan) October 2003 Delay Bounds  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

WPMC 2003 Yokosuka, Kanagawa (Japan) October 2003 Maximum Sustainable traffic  The tightest resource margins of the links along the path are made available at the source  The source derives the maximum sustainable traffic rate, i.e., the maximum traffic that may be injected into the network without violating the QoS agreements of the connections already established

WPMC 2003 Yokosuka, Kanagawa (Japan) October 2003 How to create a path Soft-QoS routing algorithm

WPMC 2003 Yokosuka, Kanagawa (Japan) October 2003 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

WPMC 2003 Yokosuka, Kanagawa (Japan) October 2003 Simulation Results Simulation of Soft-QoS routing algorithm

WPMC 2003 Yokosuka, Kanagawa (Japan) October 2003 Simulation Scenario  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

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

WPMC 2003 Yokosuka, Kanagawa (Japan) October 2003 Simulation setup  Target connection c 1  D r = 50 ms   r = 0.2  r = 20 kbit/s  Target connection c 2  D r = 200 ms   r = 0.9  r = 30 kbit/s  Target connection c 3  D r = 200 ms   r = 0.9  r = 20 kbit/s  Target connection c 4  D r = 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

WPMC 2003 Yokosuka, Kanagawa (Japan) October 2003 Satisfaction & Delay dynamics  Satisfaction  Delay

WPMC 2003 Yokosuka, Kanagawa (Japan) October 2003 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

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

WPMC 2003 Yokosuka, Kanagawa (Japan) October 2003 Extra Slides… Spare Slides

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