| Multicarrier modulation is of considerable interest for high speed mobile communications, due to its effectiveness in a multipath fading environment. The major drawback of this technique is its performance degradation in the presence of nonlinear amplification. Linear amplification of multicarrier signals, however, would impose a substantial reduction in power efficiency, which is especially undesirable for mobile applications. The goal of this thesis is, therefore, to quantify the nonlinear amplification effects on multicarrier system performance and to optimize overall power consumption of the system.; In this thesis, a general objective function for the power optimization of communication systems with nonlinear power amplifiers is derived. This derivation reveals the shortcomings of the conventionally used objective function. In order to demonstrate the methodology for power optimization based on the objective function, we present optimization procedures for multicarrier systems with various amplifiers, including dc bias controlled amplifiers. In the process of optimization, we are able to demonstrate a significant power reduction using dc bias control schemes for highly nonconstant envelope signals, such as multicarrier signals.; The effect of amplifier nonlinearities on the performance of multicarrier spread spectrum systems in both single-user and multi-user environments is analyzed. For the multi-user case, single-cell multicarrier code division multiple access systems are considered and perfect power control is assumed. A memoryless polynomial model is used to represent the amplifier amplitude nonlinearities, and a slow frequency nonselective independent Rayleigh fading channel is assumed for each modulated carrier.; We derive bit error probability for uncoded systems and upper bounds on the bit error probability for convolutionally coded systems in both single and multi-user systems. In multi-user systems, the effect of other users' nonlinearities on the performance of a desired user is analytically derived and the total power consumption of users is optimized. Finally, we identify the inherent power consumption problem for conventional amplifiers used in power controlled cellular systems. We provide an effective solution to this problem and quantify realizable power savings. |
