1 Mohamed Amine Ismail INRIA, Planete Team R&D Department UDcast An Improved WiMAX Module for ns-3 Simulator _____________________________ 3rd International ICST Conference on Simulation Tools and Techniques SIMUTools2010 Workshop on NS-3 Torremolinos, Malaga, Spain - March

2 Presentation Outline 1. Overview of the WiMAX technology 2. WiMAX simulators 3. WiMAX Module for ns-3 Key challenges Key challenges Software design Software design –MAC Layer –PHY Layer 4. Limitations and future work 5. Conclusion

3 Overview of WiMAX Technology

4 Overview of WiMAX WiMAX (Worldwide Interoperability for Microwave Access ) is: A radio interface technology standardized by IEEE (802.16d) for fixed deployment[1] (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 A label for Compliance/Interoperability, delivered by WMF WMF takes in charge the definition and realization of certification

5 WiMAX on Simulators

6 WiMAX simulators FeaturesWINSE(ns-2) Numbat (OMNET++) NCTUns PMPXXX Mesh--X OFDMXXX OFDMAXX- ARQXX- Initial Ranging XXX Service Flows management -XX Management connection XXX UGS SF XX- rtPS & nrtPS service flows X-- BE SF XXX ertPS SF X-- CS Packet Classifier X-X

7 WiMAX Module for ns-3

8 First WiMAX module for ns-3 Based on d and e standard The code is available at the following URL: under the GNU License and has been recently merged with the main ns-3 dev treehttp://code.nsnam.org/iamine/ns-3-wimax 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 lines of code

9 Key challenges Understanding 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

10 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,...

11 Module Architecture

12 MAC Layer The 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

13 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

14 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

15 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

16 Implementation: Things to be done... FeaturesWINSENumbatNCTUnsNS-3-WiMAX PMPXXXX Mesh--X- OFDMXXXX OFDMAXX-- ARQXX-- Initial Ranging XXXX Service Flows Initialization -XXX Management connection XXXX UGS class XX-X rtPS & nrtPs class X--X BE class XXXX ertPS class X--- CS Packet Classifier X--X

17 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.

18 References [1] IEEE std , IEEE Standard for Local and Metropolitan Area Networks- Part 16: Air Interface for fixed Broadband Wireless Access Systems. October [2] IEEE std e-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 [3] [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 1 st International Conference on Performance Evaluation Methodologies and Tool, October 2006 [5] The Network Simulator ns-2 NIST add-on – IEEE 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 18 th 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,

19 Thank you