Multiple-input multiple-output (MIMO) OFDM systems with implementation impairments.

摘要

High speed communications over broadband wireless channels has emerged as a key feature of future communications systems due in part to the explosive interest in information technology applications, including wireless sensor networks, mobile computing, high-speed mobile internet, and real time wireless multimedia applications. The demand for higher information capacity in these and other similar applications has motivated the utilization of broadband wireless channels in order to provide higher data rates.; Orthogonal frequency division multiplexing (OFDM) is emerging as the modulation scheme for broadband communications. This is mainly motivated by the simple receiver structures for OFDM systems over broadband channels. OFDM-based physical layers have already been chosen for several wireless systems such as the IEEE 802.11a wireless local area network (WLAN) in the 5GHz band [WLA99], the recently adopted IEEE 802.11g wireless local area network (WLAN) in the 2.4GHz band [WLA03], and the European digital video broadcasting system (DVB-T) [DVB]. It is also under consideration as the high rate alternate physical layer to the IEEE P802.15.3 wireless personal area network (WPAN) [WPA], the IEEE 802.20 mobile broadband wireless access (MBWA) [MBW] and the IEEE 802.16 wireless metropolitan area networks (WMAN) [WMA].; This dissertation addresses some challenging issues in MIMO OFDM implementations. One limiting issue in implementing low-cost, low-power, and fully-integrated wireless systems is the impairments associated with the analog processing due to component imperfections. The impairments in the analog domain are mainly due to fabrication process variations which are neither predictable nor controllable and tend to increase with fabrication technologies scaling down. Chapters 1-3 of this dissertation address one of the dominating sources of such impairments (i.e., IQ imbalances) and develop novel efficient compensation algorithms in the digital baseband domain. Chapters 4-5 show how the structure of space time codes can be exploited to design efficient MIMO OFDM receiver structures, both least-squares and adaptive. Chapters 6-7 of the dissertation present two structural enhancements to OFDM receivers in terms of data recovery and channel tracking. (Abstract shortened by UMI.)