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Handover Optimization in GSM DEGREE PROJECT, IN SIGNAL PROCESSING (EQ272X) , SECOND LEVEL STOCKHOLM, SWEDEN 2015 Handover optimization in GSM AHMAD J.A. BAZZARI KTH ROYAL INSTITUTE OF TECHNOLOGY ELECTRICAL ENGINEERING www.kth.se Royal Institute of Technology EE - School Master's thesis report for a Degree Project in Signal Processing (EQ272X) Handover optimization in GSM Ahmad Bazzari Master's Programme, Research on Information and Communication Technologies Supervisors: Per Zetterberg (KTH), Sebastian Lindqvist (Ericsson) Examiner: Joakim Jaldén (KTH) Date: 31st May 2015 Handover optimization in GSM, Bazzari 2015 i Acknowledgment I would like to thank the awesome people at Ericsson for the great working environment and the limitless support I found and experienced during the course of this work: my supervisor Sebastian Lindqvist for his support and guidance throughout this work, Birgitta Sagebrand for her endless support and advices, Joakim Riedel, Patrik Wiman, Ulf Händel, and Jaroslaw Dudek. Moreover, I would like to express my deepest gratitude to our manager Magnus Sandelin, to whom I will always be grateful for giving me the opportunity of working at Ericsson. My sincere appreciation is extended to both my examiner professor Joakim Jaldén, and supervisor Per Zetterberg at the electrical engineering school of KTH for their valuable support and advice. Special thanks to Johann Pavski, the brilliant mathematician for all the thoughts and discussions we had, and for the journey we shared for five months at Ericsson in Linköping. I would also like to thank my classmates in MERIT program whom I spent a lovely two years in two universities I am proud to be one of their alumni’s; Politecnico di Torino (PdT) in Italy and the royal institute of technology (KTH) in Sweden. My thanks go to all the amazing friends I met in Torino, Stockholm, and Linköping. I would also like to extend my deepest gratitude to my family. Without their love, support and encouragement, this whole two years journey would not be possible nor bearable. ii Handover optimization in GSM, Bazzari 2015 Handover optimization in GSM, Bazzari 2015 iii Abstract The current trend in the cellular networks to reduce the amount of spectrum dedicated to GSM networks put a burden on the radio access part to keep the promised quality of service. In addition to the focus of operators on other radio access technologies and data networks have raised the need to direct most of the effort towards other activities. Subsequently new techniques are needed to compensate for the lack of time and resources to keep GSM networks as optimized as possible. The handover functionality is in the heart of any cellular system. It is more important when delay is not tolerated. Therefore, the choice of its parameters is important. These parameters are chosen based on network performance and traffic load patterns among other criteria. It is a time consuming task, and investigating in a way to automatically choose appropriate settings for its parameters is desired. This work investigates the possibility of such an automated procedure. A simulation environment is developed in order to run simulations. An automated function that utilizes the principles of control theory, optimization, and live networks statistics is developed and used to build an algorithm to regulate the settings of the handover procedure. By regulating four parameters from the handover procedure, and by introducing different traffic loads, frequency reuse and mobility patterns, while testing the results against a set of performance metrics in the simulator. The results show better network performance in terms of performance metrics when the regulating algorithm is applied than when manually choosing values of these four parameters. However, further investigation shows that the algorithm under an aggressive mobility pattern imitating a high speed moving users, might need a stopping rule. The algorithm tries to find a better network performance even if the current metrics are acceptable. This appears to be invalid approach under some aggressive models. iv Handover optimization in GSM, Bazzari 2015 Handover optimization in GSM, Bazzari 2015 v Table of Contents CHAPTER 1 INTRODUCTION .........................................................................................1 1.1 Background ................................................................................................................................ .1 1.2 Motivation ................................................................................................................................... 2 1.3 Previous work............................................................................................................................. 3 1.4 Problem statement ..................................................................................................................... 4 CHAPTER 2 LITERATURE REVIEW ...............................................................................5 2.1 GSM overview ............................................................................................................................ 5 2.2 Protocols and interfaces in GSM .............................................................................................. 7 2.2.1 General overview ............................................................................................................... 8 2.2.2 The air interface .................................................................................................................. 9 2.3 Handover in GSM .................................................................................................................... 10 2.3.1 Handover classifications .................................................................................................. 10 2.3.2 Handover initiation .......................................................................................................... 11 2.4 Logical channels ....................................................................................................................... 12 2.5 Speech and channel coding .................................................................................................... 13 2.5.1 Speech coding ................................................................................................................... 13 2.5.2 Channel coding ................................................................................................................. 13 2.6 Frequency management in GSM ............................................................................................ 14 2.7 Radio link measurements in GSM ......................................................................................... 16 CHAPTER 3 METHODOLOGY AND APPROACH ....................................................21 3.1 Area if interest .......................................................................................................................... 21 3.2 The approach ............................................................................................................................ 22 3.3 The simulator ............................................................................................................................ 23 3.3.1 Overview ........................................................................................................................... 23 3.3.2 Handover functionality and movement patterns ........................................................ 24 3.3.3 The model and scenarios ................................................................................................. 27 3.4 Parameters of Interest and Key Performance Indicators .................................................... 29 3.5 Simulation ................................................................................................................................. 31 CHAPTER 4 THE REGULATING ALGORITHM ........................................................35 4.1 The framework ......................................................................................................................... 35 vi Handover optimization in GSM, Bazzari 2015 4.1.1 Control theory approach ................................................................................................. 35 4.1.2 The optimization approach ............................................................................................. 42 CHAPTER 5 SIMULATION RESULTS ......................................................................... 43 5.1 Baseline results ......................................................................................................................... 43 5.2 The algorithm results .............................................................................................................. 46 5.2.1 First simulation step ......................................................................................................... 46 5.2.2 Second simulation step .................................................................................................... 47 5.2.3 Third simulation step ....................................................................................................... 47 5.2.4 Fourth simulation step ..................................................................................................... 48 5.2.5 Fifth simulation step ........................................................................................................ 48 5.3 Discussion ................................................................................................................................
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