Measurement-based Performance Evaluation of WiMAX and HSDPA

In this work, a realistic physical layer performance evaluation of High Speed Downlink Packet Access (HSDPA) as well as IEEE 802.16-2004, commonly referred to as Worldwide Inter-operability for Microwave Access (WiMAX is provided. The performance evaluation is carried out in two measurement campaigns that took place in an alpine and an urban environment. Both, WiMAX and HSDPA use adaptive modulation and coding to adapt the channel coding rate and the size of the symbol alphabet to the current channel conditions. Additionally, both systems allow for multiple transmit and multiple receive antennas to increase the spectral efficiency and the reliability of the transmission. While WiMAX utilizes multiple transmit antennas by simple Alamouti space-time coding, HSDPA implements a closed-loop system with channel adaptive spatial precoding. The necessary, quantized channel information is fed back from the user equipment to the base station. The physical layer performance of both systems is evaluated in terms of measured data throughput. This allows a direct comparison with theoretic bounds like mutual information or channel capacity. Due to inherent system losses (like for example due to the transmission of guard bands, cyclic prefix, or pilot signals), not even a system with an optimum receiver is able to achieve a throughput equal to the mutual information or the channel capacity. Therefore, a so-called achievable throughput is defined as performance bound that takes the inherent system losses into account. This thesis is structured as follows: Chapter 1 introduces the methodology selected for performance evaluation. Furthermore, the scope of work is defined. Chapter 2 covers the WiMAX system and the implemented algorithms. Among others, a novel Approximate Linear Minimum Mean Square Error channel estimator is derived and compared to other channel estimation techniques in the measurement results section of this chapter. In Chapter 3, the HSDPA system is considered. A novel tap-wise Linear Minimum Mean Square Error channel estimator and the implementation of the required feedback are explained in detail before measurement results are presented. In Chapter 4, WiMAX and HSDPA are compared in terms of measured throughput, achievable throughput, mutual information, and channel capacity. Chapter 5 provides a summary of the thesis as well as an outlook to future measurements of the upcoming Long Term Evolution system. In the appendix of this thesis, the measurement setups in alpine and urban scenarios are described in detail. Furthermore, the measurement procedure involving the Vienna MIMO Testbed is explained shortly.