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Mohamed Amine IsmailMohamed Amine IsmailAmine.ismail@{UDcast.com,INRIA.fr}Amine.ismail@{UDcast.com,INRIA.fr}

INRIA, Planete Team

R&D Department UDcast

An Improved WiMAX Module for An Improved WiMAX Module for ns-3 Simulatorns-3 Simulator

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3rd International ICST Conference on Simulation Tools and Techniques

SIMUSIMUToolsTools2010 2010

Workshop on NS-3Workshop on NS-3Torremolinos, Malaga, Spain - March 15 2010Torremolinos, Malaga, Spain - March 15 2010

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Presentation Outline

1.1. Overview of the WiMAX technologyOverview of the WiMAX technology2.2. WiMAX simulatorsWiMAX simulators3.3. WiMAX Module for ns-3WiMAX Module for ns-3

•Key challengesKey challenges

•Software designSoftware design– MAC LayerMAC Layer– PHY LayerPHY Layer

4.4. Limitations and future workLimitations and future work5.5. ConclusionConclusion

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Overview of WiMAX Technology

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Overview of WiMAX

WiMAX (Worldwide Interoperability for Microwave Access ) is:

• A radio interface technology standardized by IEEE

• 802.16-2004 (802.16d) for fixed deployment[1]

• 802.16-2005 (802.16e) for mobile deployment[2]

• IEEE defines layer 1 (PHY) and layer 2(MAC) details. The scope is limited to the interface between terminals (SS) and Base Station (BS)

• An end-to-end architecture defined by the WiMAX Forum (WMF) [3]

• The architecture details how to deploy 802.16

• A label for Compliance/Interoperability, delivered by WMF

• WMF takes in charge the definition and realization of certification

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WiMAX on Simulators

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WiMAX simulators Features WINSE(ns-2) Numbat (OMNET+

+)NCTUns

PMP X X X

Mesh - - X

OFDM X X X

OFDMA X X -

ARQ X X -

Initial Ranging X X X

Service Flows management - X X

Management connection X X X

UGS SF X X -

rtPS & nrtPS service flows X - -

BE SF X X X

ertPS SF X - -

CS Packet Classifier X - X

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WiMAX Module for ns-3

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WiMAX Module for ns-3

• First WiMAX module for ns-3

• Based on 802.16d and 802.16e standard

• The code is available at the following URL: http://code.nsnam.org/iamine/ns-3-wimax under the GNU License and has been recently merged with the main ns-3 dev tree

• Implements the Point-to-Multipoint (PMP) topology with TDD mode and MAN ODFM PHY

• Supporting important features including QoS scheduling service, bandwidth management, uplink request/grant scheduling…

• Built completely in C++ with more than 65 classes and approximately 30000 lines of code

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Key challenges • Understanding 802.16

• A complex technology, huge specification, vague description

• Open Area (Scheduling, Burst adaptation)

• Programming challenges

• Compliance with ns-3 API and coding standard

• Time and memory efficient code

• Robust architecture

• Cross layer design

• Parallel MAC and PHY development , interdependence MAC/PHY

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Software Design

• Design fully object oriented

• Class WimaxNetDevice for the MAC layer of WiMAX it extends the NetDevice class of ns-3

• WimaxNetDevice is extended by BaseStationNetDevice and SubscriberStationNetDevice defining the MAC layers of BS and SS respectively.

• The key functions of MAC are distributed to several other classes like: LinkManager, UplinkScheduler, SsScheduler, BsScheduler, ConnectionManager, serviceFlowManager, BurstProfileManager, ...

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Module Architecture

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MAC Layer• The 802.16 MAC layer is divided in to two sublayers: The Convergence sublayer

(CS) and the Common-part sublayer (CPS)

• CS is responsible for:

• Receiving packets from the higher layer and from peer stations

• Classifying packets to appropriate connections

• Keeps a mapping between connection ID and service flows

• CPS is responsible for

• Framing and management messages (DL and UL MAP, packet burst, ... )

• Downlink and Uplink scheduling

• three uplink schedulers

• two downlink sechdulers

• Network Entry and Initialization

• Connection and addressing

• Service flow creation (DSA-X messages)

• Bandwidth request and Grant Mechanism

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PHY layer

• The older version of module (2009) provided two different version of PHY layer

• The first one is a basic implementation

• Simply forwards bursts received by the MAC layer ignoring any underlying PHY layer details very simplistic and not realistic

• The second is very complete and implements all the OFDM operation using IT++ library [8]

• Hardly usable for scalability reasons

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PHY layer

• New implementation of PHY layer

• Based on WirelessMAN-OFDM specification

• Implemented by the SimpleOfdmWiMAXPhy Class

• Block encoding : packet burst are converted to bit stream and then splitted into smaller FEC blocks

• Supports all the 7 modulations and coding schemes (MCS)

• Uses pre-generated SNR to Block Error Rate trace files

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Implementation: Things already done...

• Basic architecture, framing, base station, subscriber station, ...

• Creation, transmission and processing of control messages

• Scanning synchronization and network entry

• Link management: Transmission of ranging messages

• Dynamic creation of connections and service flows (DSX-messages)

• New downlink and uplink schedulers

• A scalable and realistic physical layer

• Support for Multicast

• IP packet Classifier enabling the support of multiple service flows per SS

• Support of fragmentation and defragmentation of MAC PDUs

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Implementation: Things to be done... Features WINSE Numbat NCTUns NS-3-WiMAX

PMP X X X X

Mesh - - X -

OFDM X X X X

OFDMA X X - -

ARQ X X - -

Initial Ranging X X X X

Service Flows Initialization - X X X

Management connection X X X X

UGS class X X - X

rtPS & nrtPs class X - - X

BE class X X X X

ertPS class X - - -

CS Packet Classifier X - - X

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Conclusion• We have proposed a WiMAX module for ns-3 simulator• The module implements the key components of WiMAX MAC and

PHY• Implementing the PMP mode with OFDM specifications• design fully object-oriented• High attention has been put to come up with a standard compliant

implementation• Merged with the main branch of ns-3. Release 3.8

expected by end of April• We hope this module contributes to the scientific society

and facilitates in evaluating and designing WiMAX systems.

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References• [1] IEEE std. 802.16-2004, IEEE Standard for Local and Metropolitan Area Networks-

Part 16: Air Interface for fixed Broadband Wireless Access Systems. October 2004.

• [2] IEEE std. 802.16e-2005, IEEE Standard for Local and Metropolitan Area Networks- Part 16: Air Interface for fixed Broadband Wireless Access Systems- Amendment 2: Physical and Medium Access Control Layers for Combined Fixed and Mobile Operation in Licensed Bands. February 2006.

• [3] www.wimaxforum.org

• [4] J.Chen, C.-C Wnag, F.C.-D. Tsai, C.-W. Chang, S.-S. Liu, J. Guo, W.-j. Lien, I.-H Sum and C.-H Hung. Desing and Implementation of WiMAX Module for ns-2 Simulator. In 1st International Conference on Performance Evaluation Methodologies and Tool, October 2006

• [5] The Network Simulator ns-2 NIST add-on – IEEE 802.16 model (MAC+PHY). Technical report, National Institute of Standards and Technology, June 2007

• [6] J.F. Borina and N.L. Da Fonseca. WiMAX Module for ns-2 Simulator. In 18th Annual IEEE International Symposium on Personal, Indoor and Mobile Radio Communication (PIMRC'07). IEEE, September 2007

• [7] F. Cristiani. Simulation of WiMAX Physical Layer. Technical report, Universita degli Studi di Napoli. Federico II, Italy, December 2007

• [8] IT++ Library of mathematical, signal processing and communication routines, http://itpp.sourceforge.net/.

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Thank you