Department of Electrical and Computer Engineering
M.S. Thesis Abstract
Multi-cell WCDMA Signal Processing Simulation Testbed
Third generation (3G) wireless systems are being developed to increase system capacity and support innovative broadband multimedia services. Wideband CDMA (WCDMA) is one such system where the air interfaces need to support services with different bit error rates, delays, and data rates. This thesis describes the Wireless Propagation and Protocols Evaluation Testbed (WiPPET signal ), a virtual testbed for signal processing simulation for the physical layers of CDMA wireless systems. A multicell simulation platform implementing user mobility and detailed radio channels has been developed to study the impact of mobile users, fading and propagation effects, and othercell interference on waveform level processing. The ultimate aim of the study is evaluate and improve algorithms at the link level (interference cancellation) and system level (power control and handoff) for WCDMA systems.
The modules in the simulation are constructed atop the object oriented Scalable Simulation Framework (SSF) API that promotes high efficiency and separation of modeling code from the internals of a parallel simulator. As an application of this platform, the reverse link performance of the WCDMA (NTT DoCoMo/ARIB) transceiver design and framing structure has been analyzed and validated against measurements for multiple mobiles in a single cell. Subsequently, we have extended the model to multiple cells with SIR based power control, antenna diversity, and soft handoff. Bit error rate results have been obtained for various system parameters, including noise variance, SIR targets, transmitter power limits, and spreading factors. This reverse link simulation has being used to perform multi-cell evaluation of the pilot assisted coherent multistage interference canceller proposed by NTT DoCoMo. Channel estimation, power control and channel coding are also being investigated to help in the improvement of system capacity. Forward link simulation is being used to assist in soft handoff. Gains in performance due to soft handoff have also been illustrated. The parallelization problem for the simulation is described, and two solution approaches are proposed. Speedups obtained from the preferred solution are also illustrated. The validation of the various modules of WiPPET signal has also been discussed. As part of the thesis, an example SSF program has been elucidated for the benefit of future users.
Thesis Director: Professor Roy Yates