RF Impairment Compensation for Future Radio Systems
15.1 INTRODUCTION AND MOTIVATION
The future of wireless communications is strongly heterogeneous, being composed of a rich mixture of various mobile cellular systems (UMTS/HSPA, LTE, WiMAX, IMT-Advanced, etc.), fixed wireless local area networks (e.g., 802.11x), short-range low-energy personal communications (UWB), positioning and navigation systems (e.g., GPS, Galileo), and broadcasting systems (e.g., DVB-H) . To access these systems and services using a single user terminal, highly flexible and reconfigurable radio transmitters and receivers are needed. In addition to the flexibility aspect, another major issue in the design and implementation of radio equipment for mass-market applications is the cost-efficiency, in terms of radio implementation size, cost, and power consumption. This applies also to the base station radio equipment used, for example, in cellular systems. The cost-efficiency issues of individual radios are emphasized especially when multiple transmitting and receiving antennas and thus multi-antenna waveforms are deployed, calling for multiple parallel radio implementations operating simultaneously in a single device [2-6].
In general, building such compact and low-cost yet flexible and high-quality radio equipment for future wireless systems is a very challenging task. On the one hand, the needs for flexibility and reconfigurability ...