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CROSS LAYER DESIGN OF INTERFERENCE AWARE MULTI-HOP MOBILE RELAY WIMAX NETWORK

MUHAMMAD FIRDAUS BIN DZULKURNAIN

UNIVERSITI TEKNOLOGI MALAYSIA

CROSS LAYER DESIGN OF INTERFERENCE AWARE MULTI-HOP

MOBILE RELAY WIMAX NETWORK

MUHAMMAD FIRDAUS BIN DZULKURNAIN

A project report submitted in fulfilment of the

requirements for the award of the degree of

Master of Engineering (Electrical – Electronics and Telecommunications)

Faculty of Electrical Engineering

Universiti Teknologi Malaysia

MAY 2011

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Dedicated, in thankful appreciation for support, encouragement and understandings

to my father and mother, Dzulkurnain b. Mohd Isa and Zaimah bt. Mahamood and to

all my beloved friends.

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ACKNOWLEDGEMENTS

In the name of ALLAH S.W.T., the Most Merciful and the Most Gracious.

Alhamdulillah, a lot of thanks to ALLAH S.W.T for His blessing for me to

complete my project and this thesis is the symbolic of the support and guidance that I

get from all my family and friends.

First and foremost, I would like to express my heartily gratitude to my

supervisor, Prof. Dr. Norsheila bt. Fisal for the guidance and enthusiasm given

throughout the progress of this project.

My appreciation also goes to my family who has been so tolerant and

supports me all these years. Special thanks for their encouragement, love and

emotional supports that they had given to me. Besides, I would like take this

opportunity to thank all my friends, PhD students in UTM – MIMOS Centre of

Excellence (COE) for their technical support and moral guidance.

I also would like to thank to those who has given the constructive comments

and ideas in completing this project and I hope this project could give the advantages

and knowledge for all the readers.

I am also indebted to my siblings for their supports throughout my life.

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ABSTRACT

The MMR (IEEE 802.16j) WiMAX standard provides a mechanism for

creating multi-hop relay, which can extend coverage and capacity and be deployed as

a high speed wide area wireless network. Interference in wireless system is one of the

most significant factors that limit the network capacity and scalability of wireless

relay networks. Cross layer design (CLD) and optimization is known to improve the

performance of wireless communication and mobile networks. In order to design a

spectrally efficient IEEE 802.16j relay network, a joint design and optimization

technique that relies on Physical layer which has the interference information, as well

as scheduling and route selection mechanism in Data Link layer will be opted using

software NCTUns and programming languange. The proposed scheme includes a

novel interference-aware route construction algorithm and an enhanced scheduling

scheme, which consider both traffic load and demand interference conditions. This

interference-aware design should lead to better spatial reuse and thus higher spectral

efficiency. By taking average 10 mobile users into consideration, the results show

that the throughput is enhanced up to 8.5% from the normal implementation. It can

be concluded that, the CLD approach will select the best route selection based on the

SNR calculation and improve the scheduling for this network.

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ABSTRAK

MMR (IEEE 802.16j) WiMAX merupakan satu piawai yang memberikan

mekanisma untuk menghasilkan geganti banyak arah lompatan, yang mana mampu

untuk meluaskan liputan dan kapasiti dan boleh menghasilkan jalur lebar tanpa

wayar bagi kawsan yang luas. Masalah gangguan interferens di dalam rangkaian

tanpa wayar adalah merupakan salah satu faktor yang boleh menghadkan kapasiti

rangkaian tersebut. Rekaan penyilangan antara lapisan adalah mampu untuk

menambah baik prestasi rangkaian komunikasi tanpa wayar. Untuk membolehkan

penghasilan yang efisyen terhadap rangkaian IEEE 802.16j, rekaan pencantuman

yang optimum yang bergantung kepada lapisan Fizikal yang mana mempunyai

informasi interferens, juga informasi bagi memilih haluan di dalam lapisan Pautan

Data dihasilkan menggunakan bantuan program simulasi jaringan (NCTUns) dan

pengaturcaraan C. Skim yang dihasilkan mengandungi algoritma binaan laluan tanpa

interferens dan skim peninggian daftar laluan, mengambil kira beban trafik dan

kondisi interferens. Dengan mengambil kira 10 sampel pengguna mobil, hasil kajian

menunjukkan output capaian dapat ditingkatkan kepada 8.5% daripada keadaan

rangkaian biasa. Kesimpulannya, penghasilan penyilangan antara lapisan akan

membantu untuk memilih laluan yang paling baik berdasarkan pengiraan SNR

seterusnya dapat mengatasi masalah interferns di dalam rangkaian tanpa wayar.

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TABLE OF CONTENTS

CHAPTER TITLE PAGE

TITLE PAGE i

DECLARATION ii

DEDICATION iii

ACKNOWLEDGEMENTS iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF TABLES x

LIST OF FIGURES xi

LIST OF GRAPHS xiii

LIST OF ABBREVIATION xiv

LIST OF SYMBOLS xv

1 INTRODUCTION 1

1.1 Project Background 1

1.2 Problem Statement 2

1.3 Scope of Work 4

1.4 Objective 5

1.5 Thesis Outline 6

2 LITERATURE REVIEW 7

2.1 IEEE 802.16j Mobile Multi-Hop Relay (MMR) 7

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2.1.1 Relay Modes 9

2.1.2 PHY Layer Frame Structure 13

2.1.3 MAC Layer Frame Structure 15

2.1.3.1 Forwarding Scheme 16

2.1.3.2 Routing and Path Management 17

2.1.3.3 Initial Ranging and Network Entry 18

2.2 Cross Layer Design 18

2.2.1 Cross Layer Optimizations 21

2.3 NCTUns Software 22

2.4 SNR and Capacity in WiMAX 24

2.4.1 Signal-to-Noise Ratio (SNR) 24

2.4.2 Shannon’s Theorem of Capacity 25

2.5 Path and Relay Selection in WiMAX 26

3 METHODOLOGY 27

3.1 NCTUns 6.0 27

3.2 Cross Layer Design Implementation 30

3.2.1 MAC RS 31

3.2.2 Scheduling 32

3.3 Simulation 32

3.3.1 Drawing Topology 32

3.3.2 MAC Module and Rebuilding

Simulation Engine 34

3.4 Network Model 35

3.4.1 Effect increasing the number of

mobile stations (MS) 36

3.4.2 Effect increasing number of relay 37

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4 RESULT AND DISCUSSION 39

4.1 Introduction 39

4.2 Effect increasing the number of

mobile stations (MS) 40

4.2.1 Throughput 41

4.2.2 Delay 43

4.3 Effect increasing number of relay 44

4.3.1 Throughput 45

4.3.2 Delay 47

5 CONCLUSION AND RECOMMENDATION 50

5.1 Conclusion 50

5.2 Recommendations for future work 51

REFERENCES 53

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LIST OF TABLES

TABLE NO. TITLE PAGE

2.1 Comparison of 802.16j and 802.16e-2005 capabilities 8

2.2 Transparent and Non-Transparent Mode Comparison 12

3.1 Simulation parameters 28

xi

LIST OF FIGURES

FIGURE NO. TITLE PAGE

1.1 Multihop Network 3

1.2 Example of interference link in multihop network 4

2.1 The concept of 802.16j MMR 10

2.2 Topology for 802.16j Transparent Mode 11

2.3 Topology for 802.16j Non-Transparent Mode 12

2.4 Transparent mode frame structure (a) viewed at BS,

(b) viewed at RS 14

2.5 Non-transparent mode frame structure

(a) viewed at BS, (b) viewed at RS 15

2.6 Tunnel-based scheme 16

2.7 CID-based tunnel 17

2.8 Cross layer design 20

2.9 Cross-layer optimizations involving Physical, MAC,

Routing, and Transport Layers 22

2.10 SNR detection in 802.16j 27

3.1 NCTUns 6.0 in Linux kernel 28

3.2 Non-transparent mode topology 29

3.3 Physical module in NCTUns 29

3.4 Flowchart of connection using cross layer design 30

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3.5 Cross layer between PHY and MAC layer 31

3.6 GUI environment and running simulation 33

3.7 MAC editing and rebuild new simulation engine 34

3.8 Newly built GUI 35

3.9 QoS provisioning 36

3.10 Increasing number of MS 37

3.11 Increasing number of relays 38

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LIST OF GRAPHS

GRAPH NO. TITLE PAGE

4.1 The average throughput for a selected no. of MS 41

4.2 Average delay of increasing MS 43

4.3 Average throughput relays without CLD 45

4.4 Average throughput relays with CLD 45

4.5 Average delay without CLD 47

4.6 Average delay with CLD 48

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LIST OF ABBREVIATIONS

WiMAX - Worldwide Interoperability for Microwave Acces

OFDM - Orthogonal Frequency Division Multiplexing

OFDMA - Orthogonal Frequency Division Multiple Access

MMR - Multihop Mobile Relay

BS - Base Station

RS - Relay Station

MS - Mobile Station

T-RS - Transparent Relay Station

NT-RS - Non-transparent Relay Station

PHY - Physical layer

MAC - Medium Access Control

SNR - Signal to noise ratio

BER - Bit error rate

UL - Uplink

DL - Downlink

QoS - Quality of Service

GUI - Graphical User Interface

SE - Simulation Engine

UGS - Unsolicited Grant Service

rtPS - Real-time polling service

nrtPS - Non Real-time polling service

CID - Connection identifier

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LIST OF SYMBOLS

dBm - power ratio in decibels in reference to 1 mW

MHz - megahertz

Mbps - megabit per second

kbps - kilobit per second

CHAPTER 1

INTRODUCTION

1.1 Project Background

WiMAX (Worldwide Interoperability for Microwave Access) is an IP based,

wireless broadband access technology that provides performance similar to

802.11/Wi-Fi networks with the coverage and QOS (quality of service) of cellular

networks. WiMAX can provide broadband wireless access (BWA) up to 30 miles (50

km) for fixed stations, and 3 - 10 miles (5 - 15 km) for mobile stations. In contrast,

the WiFi/802.11 wireless local area network standard is limited in most cases to only

100 - 300 feet (30 - 100m).

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The new mobile multi-hop relay (MMR), 802.16j network architecture

imposes a demanding performance on relay stations. These relays will functionally

serve as an aggregating point on behalf of the BS for traffic collection from and

distribution to the multiple MSs associated with them. WiMAX 16j promises to

support mobility up to speeds of 120 km/h. The peak DL data rates are up to 63

Mbps per sector and peak UL data rates are up to 28 Mbps per sector in a 10 MHz

channel with the inclusion of MIMO antenna technique. Peak data rates of 300 Mbps

are achievable. The speed of data can reach 10 Mbps within 10 km range from a

mobile station to base station.

Traditionally, layered architecture like OSI and TCP/IP model, defines a

hierarchy of services to be provided by the individual layers (Bertsekas and Gallager,

1992). However, this method does not lead to an optimum solution for wireless

network. Basically, cross layer design (CLD) involved feedbacks received from other

layer to optimize the information in the current layer so that the performance is

enhanced (Raisinghani and lyer, 2004). CLD will sense the SNR of downlink

channel when there is a request of downlink communication, and send the data

packet to the nearest relay nodes. The algorithm specified in CLD will dynamically

choose the available relay station based on available spectrum before reaching the

subscribers or users. The subscriber stations are located in fixed, nomadic or mobile

wireless coverage.

1.2 Problem Statement

In MMR 802.16j network, the Mobile Station (MS) is compatible with each

other, but the Base Station (BS) in IEEE 802.16e is modified to support relay

operations. A cell of 802.16j consists of one Multihop Relay Base Station (MR-BS),

several RSs, and several MSs.

3

The MMR network is aiming for the improvement of network coverage via

non-transparent (NT) mode relaying using two or more hops. The problem in any

relay network is that, once relay is used, the bandwidth is parted in every relay

existed in the network which will reduced the total of bandwidth in that particular

network.

Figure 1.1: Multihop network

The network topology above describes the implementation of WiMAX MMR

802.16j NT in which the relay station (RS) can acts as a base station (BS) that will

choose the path to send data from mobile station (MS) to BS. Current

implementation in NCTUns network simulator programs the packets sent from MS to

BS to follow the route that has been determined by RS, without considering any

qualitative physical condition i.e. weak signal, which means that the MS will still

have to follow this predetermined route even though the SNR received is low,

although it is considered as the best path.

4

The problem arises when the interference in wireless network occurs (Figure

1.2), which will limit the network capacity and scalability of wireless relay networks.

Therefore, an appropriate design of interference aware of MMR network should be

presented in order to increase the network throughput and at the same time can

enhance the coverage of the network. A cross layer design (CLD) method will make

new adoptions to the MAC layer that rely on the signal-to-noise ratio (SNR)

information in physical (PHY) layer and the scheduling slots in the medium access

layer (MAC) is presented. The network performance of CLD in the MMR will be

simulated using the NCTU-ns software.

Figure 1.2: Example of interference link in multihop network

1.3 Scope of Work

The relay mode that will be used in this project is non-transparent relay mode

for a two-hop 802.16j between mobile station and base station. Cross layer routing

intends to play an essential role in improving the performance of MMR networks.

Such cross-layer design lets protocols that belong to different layers cooperate in

sharing network status information while still maintaining the layers’ separation at

the design level.

5

For this project, the software that is going to be worked with is a network

simulation program, NCTUns version 6.0, run on Linux Fedora 11, using protocol

stacks and global variable initialization defined for 802.16 network nodes. On

NCTUns, the behaviour of MMR WiMAX will be predicted without an actual

network being present. The cross layer design methodology will be adapted using C

programming in the IEEE 802.16j modules in NCTUns.

The Quality of Service (QoS) of this network is measured in terms of the

network throughput an end-to-end delay of the network.

1.4 Objective

1) To propose an efficient approach for increasing the utilization of

WiMAX relay through appropriate design of multi-hop routing and scheduling

2) To design the cross-layer optimization mechanism in IEEE 802.16j in

order to increase the performance of mobile networks.

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1.5 Thesis outline

This project report is divided into five chapters namely introduction, literature

review, methodology, results and conclusion. Each chapter will discuss on different

issues related to the project. Chapter 1 covers on the introduction where it explains

the background of this project, objectives, scopes of project and the project report

outline. Chapter 2 covers on the literature review of WiMAX Multihop Relay, Relay

frame structure, cross layer design, path and relay selection in MMR WiMAX. It also

covers some literatures researchers. Chapter 3 discusses the methodology of

simulation and network performance. Chapter 4 consists of results and analysis of

this project. In this chapter, all simulation results, measurement setup and

measurement results are explained. Finally, the last chapter consists of conclusion

and some future works to improve the quality of this project.

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REFERENCES

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Wireless and Mobile Broadband Radio,” IEEE Commun. Mag, Sept. 2005.

[2] N. Esseling, B. Walke, and R. Pabst, “Fixed Relays For Next Generation

Wireless Systems,” Ch. 5, Emerging Location Aware Broadband Wireless Ad Hoc

Networks, R. Ganesh, S. Kota, and K. Pahlavan, Eds., Springer Science and Business

Media, pp. 71-9, 2005.

[3] IEEE 802.16-2004, “Local and Metropolitan Area Networks, Part 16: Air

Interface for Fixed Broadband Wireless Access Systems,” Oct. 2004.

[4] IEEE 802.16e-2005, “Local and Metropolitan Area Networks, Part 16: Air

Interface for Fixed Broadband Wireless Access Systems: Amendment for Physical

and Medium Access Control Layers for Combined Fixed and Mobile Operation in

Licensed Bands,” Feb. 2006.

[5] Sanjay Shakkottai, Theodore S. Rappaport and Peter C. Karlsson, “Cross-

layer Design for Wireless Networks,” June. 2003

[6] Han, B., W. Jia and L. Lin, “Performance Evaluation Of Scheduling In IEEE

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30: 782-792, 2007

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