3.2 a Pragmatic QoS Solution in Wireless Mesh Networks the ADHOCSYS Approach

8/3/2019 3.2 a Pragmatic QoS Solution in Wireless Mesh Networks the ADHOCSYS Approach

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16th IST Mobile & Wireless Communications Summit

Budapest, Hungary 1-5 July 2007

ADHOCSYS Project IST-2004-026548

Luca Leschiutta

Politecnico di Torino, Italy

www.adhocsys.org

A pragmatic QoS solution inwireless mesh networks: the

ADHOCSYS approach


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Agenda

Why ADHOCSYS?

Project objectives

Architecture and scenarios

QoS issues

Concluding remarks


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Objectives Provide a reliable broadband Internet

access solution to people who live in rural

and mountain regions where ADSL is notavailable or non-profitable

Consider also people living outside towns

and villages

Consider also occasional visitors

Cheap solution: ability to use off-the-shelf

hardware equipments; open source

software


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Network architecture The ADHOCSYS network consists of two levels of

network hierarchy

An access network in each town/village connectingall inhabitants

A backbone connecting together towns and villages

The backbone network consists of few longwireless links while the access network consists of

many short links

Internet gateways might be connected directly to

the backbone or the access network

Depending on some external factors this general

architecture may lead to different scenarios


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Architecture illustration


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QoS goal and solutions Goal: guarantee access to an essential set of

services under all conditions while maximizingnetwork utilization for other types of services

Two implementation directions

identification and implementation of mechanisms to

be used to guarantee the availability of essential

services to all ADHOCSYS end-users, includingpriority classification, Connection Admission

Control (CAC), traffic monitoring, and QoS metrics.

selection and implementation of application-level

techniques for multimedia services, to maximizethe perceived quality based on network load and

link status


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Eight QoS classes

Class I: applications which require strong latency

constraints and low bandwidth such as VoIP and

chatting applications (jabber, Yahoo! Messenger, etc). Class II: applications requiring high throughput such

as transaction-processing applications.

Class III: interactive and best-effort type applications

like web-browsing and e-mail.

Class IV: routing and battery information.

Class V: emergency calls.

Class VI: high throughput and latency constraint suchas streaming video.

Class VII: peer-to-peer (P2P) applications.

Class VIII: other types of traffic (unclassified).

QoS Classification


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The traffic sources could be located eitheroutside or inside the ADHOCSYS network.The first case is more common

The framework is composed of thefollowing mechanisms, which are part ofthe functions of the Access Points

Traffic flow identification Scheduling and buffer management

Traffic load and channel congestion status

measurement

CAC (Connection Admission Control)

Rate adaptation

Traffic Management


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Congestion Management Based on the measurement of the

approximated congestion level the AP node

decides whether the request is accepted ornot


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802.11e The new EDCA

(Enhanced DCF

Channel Access)mechanism definedin 802.11eimplements four

different queues atMAC layer, and canbe used as amechanism to

provide unequalerror protection todifferent trafficpatterns


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Packet classificationand queueing

START (packet P received)

END (send packet)

P comes from an

ADHOCSYS node?

Tag P (IP TOS)

Linux queueing (HTB)

WMM queueing

P has been tagged?

Y N

N

Y

Deterministic QoS byHTB (HierarchicalToken Bucket)

Probabilistic QoS by

MMM (WirelessMultimedia)


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Structure of the HTB tree Mapping between application classes, application categories

and WMM Access Categories

Root

A B C

I VIIIII IIVIIV VIII

Category

Class

3 (Highest Priority)IV, VA, B

2IIIA

1I, VIB

0 (Best Effort)II, VII, VIIIC

WMM ACClassCategory


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Ns-2 Simulations Several metrics are considered, includingsystem and MAC throughput, delay atnetwork level and PSNR at application level

The main effort, in this context, has beendevoted to develop the tools to process andanalyze data from the Ns-2 simulationframework.

Our analysis shows that the new EDCA(Enhanced DCF Channel Access)mechanism defined in 802.11e allows to

achieve higher throughput for higher prioritytraffic, and that smart techniques todynamically adapt the retry limit to thenetwork conditions can lead to an increaseof the overall throughput


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Multimedia trafficmanagement

Maximize the perceived quality of multimediaservices without affecting the performance of the

whole network Algorithms for multimedia compression and

transmission often do not consider themechanisms provided by the lower layers for error

protection, scheduling, resource management We have developed a multimedia service cross-

layer framework suitable for ad-hoc networking,for jointly adapting different strategies available at

the various layers, taking into account variousmetrics, such as multimedia quality, consumedpower, and spectrum utilization


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The following issues are also studied in

the project OLSR Optimization

Security and authentication

Auto-configuration, self-healing andreliability

Standalone power supply and renewable

power supply system Installation

Open source

Other issues in the project


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Concluding remarks The objective of the ADHOCSYS project is to

provide a reliable broadband Internet accesssolution to people who live in rural and mountainregions where ADSL is not available

The goal for QoS provisioning in ADHOCSYS isto guaranteeing access to an essential set ofservices under all conditions while maximizing

network utilization for other types of services Flow identification, scheduling and queuing

using 802.11/WMM, load measurement, CACare mechanisms used for our QoS solution

Currently, we have finished the implementationphase

A complete real-life pilot network is beingdeployed in Northern Italy

Documents

3.2 a Pragmatic QoS Solution in Wireless Mesh Networks the ADHOCSYS Approach