ABSTRACT
Contents 3.1 Introduction ................................................................................... 80 3.2 Prediction and Measurement of System Coverage ................................ 81
3.2.1 Accurate Propagation Modeling: Cons and Pros ....................... 82 3.2.2 Drive and Walk Tests: Limits and Constraints ......................... 84 3.2.3 Other Methods for Database Updates ..................................... 84
3.3 Virtual Drive Test ............................................................................ 85 3.3.1 Virtual Drive Test Concept .................................................... 85 3.3.2 Network Report Acquisition .................................................. 85 3.3.3 Event and User Location Principles ......................................... 86
3.3.3.1 Satellite-based Positioning ....................................... 86 3.3.3.2 Time of Arrival-based Positioning ............................. 87 3.3.3.3 Angle of Arrival-based Positioning ............................ 88 3.3.3.4 Positioning based on Radio Signal Strength
Measurements ........................................................ 89 3.3.3.5 Location Based on Channel Pattern Matching ............ 90 3.3.3.6 Location Based on Cell ID and Sector Azimuth .......... 91 3.3.3.7 Ways to Enhance Location Ability ............................ 91
3.4 Mapping the Measured Information ................................................... 94 3.4.1 Map Types .......................................................................... 94
3.4.1.1 Traffic and Services Maps ........................................ 94 3.4.1.2 Coverage Maps ....................................................... 94 3.4.1.3 Special Events Maps ................................................ 95
3.5 Network Optimization Using VDT ................................................... 98 3.5.1 Optimizing for Measurements and Predictions-A Unified
Approach ............................................................................. 98
3.5.2 Optimization Procedures ....................................................... 99 3.5.2.1 Network Consistency Analysis .................................. 99 3.5.2.2 Neighbor Planning ................................................. 99 3.5.2.3 Frequency Planning, Scrambling, and Permutation
Codes ................................................................. 101 3.5.2.4 Cell Configuration ................................................ 101 3.5.2.5 Load Balancing ..................................................... 102
3.5.3 Requirements of Location and RSS Measurement Accuracies ... 102 3.5.4 Demonstration of an Optimization Project ............................ 103
3.6 VDT for LTE and Fourth-Generation Systems .................................. 104 3.6.1 Advanced System Main Features ........................................... 105
3.6.1.1 Flat All-IP Architecture ......................................... 105 3.6.1.2 Wideband MIMO-OFDM Air Interface ................. 105 3.6.1.3 Usage of Multi-Carriers ......................................... 105 3.6.1.4 Massive Usage of Picocells, Femtocells, and Relays .... 106 3.6.1.5 Cooperation among Network Elements ................... 106
3.6.2 VDT Concept in Advanced Systems ..................................... 107 3.7 Open Issues ................................................................................... 108 3.8 Summary ...................................................................................... 108 References .............................................................................................. 109
3.1 Introduction The cellular telephone has had a major effect on everybody’s life. Since its early days, we have witnessed a larger and larger penetration of the mobile telephone service and it has been quickly adapted as a major means of personal communications. The cellular telephone has continuously evolved over the relatively short years of its existence. From the prestigious car phone of earlier days, use of wireless communications has become ubiquitous and personal. Indoor usage is significantly larger than outdoor usage. It keeps evolving as the current trend is for the data traffic, of which the usage is constantly increasing, and the transition to all-IP (Internet Protocol) networks is the key for the next-generation networks [1,2]. User demand for higher data rates does not come without its toll. Higher data rates essentially lead to higher bandwidth systems, and the scarcity of spectrum resources makes it necessary to resort to other means to satisfy the higher-capacity demands. These may include adding base stations, increasing the spectral efficiency of the physical layer by various means such as additional antenna [multiple-input multiple-output (MIMO)] systems, using diversity and spatial multiplexing to raise the reliability of the wireless channel, and to increase its capacity. One of the most important means used by operators is sophisticated network optimization techniques, which enable adapting the network better to the needs and demands of the users and better exploiting existing resources.
