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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 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


Motivations
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


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 & Soft QoS

Hard-QoS

Soft-QoS

Yokosuka, Kanagawa (Japan) 21-22 October 2003


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


What s soft qos
What’s Soft-QoS?

Soft-QoS definition

Yokosuka, Kanagawa (Japan) 21-22 October 2003


Soft qos parameters
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


Call admission control
Call Admission Control

Distributed CAC mechanism

Yokosuka, Kanagawa (Japan) 21-22 October 2003


Path service levels
Path Service Levels

  • Path: P = (p1,…, pN)

  • Service levels:

    • Path Peak Bandwidth

    • Path Delay

Yokosuka, Kanagawa (Japan) 21-22 October 2003


Cac gaussian approx
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


MRR

Statistical MAC-layer Resource Reservation

Yokosuka, Kanagawa (Japan) 21-22 October 2003


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


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


Maximum sustainable traffic
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


How to create a path
How to create a path

Soft-QoS routing algorithm

Yokosuka, Kanagawa (Japan) 21-22 October 2003


Path creation maintenance
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


Simulation results
Simulation Results

Simulation of Soft-QoS routing algorithm

Yokosuka, Kanagawa (Japan) 21-22 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

Simulation Scenario

Yokosuka, Kanagawa (Japan) 21-22 October 2003


Gaussian approximation

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


Simulation setup
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


Satisfaction delay dynamics
Satisfaction & Delay dynamics

  • Satisfaction

  • Delay

Yokosuka, Kanagawa (Japan) 21-22 October 2003


Conclusions
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


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


Extra slides
Extra Slides…

Spare Slides

Yokosuka, Kanagawa (Japan) 21-22 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

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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