Estimation And Compensation Of Hardware Impairments For Millimeter-Wave Wireless Communication Systems

With the rapid development of the millimeter-wave technology and modern communication technology, millimeter-wave wireless communication systems are gradually applied in many fields such as satellite communications, wireless local access network (WLAN), collision-avoidance radar. Furthermore, as one of the key wireless technologies of 5G, the millimeter-wave wireless communications technology is attracting more and more attention. In this work, estimation and compensation of hardware impairments for millimeter-wave wireless communication systems are investigated. The major work of this thesis is as follows.Firstly, the features and applications of the millimeter-wave wireless communivation systems are briefly introduced. An overview of the IEEE 802.11aj (45GHz) WLAN system is given. Meanwhile, a discussion about the progress of estimation and compensation for hardware impairments in millimeter-wave wireless communications is also given.Secondly, the hardware impairments including DC offset, non-linear distortion in power amplifiers (PAs), in-phase/quadrature (1/Q) imbalance in quadrature modulators/demodulators, and phase noise (PN) in phase-locked loop (PLL) circuits are expected to significantly compromise the performance. So, the baseband equivalent models of the three hardware impairments are presented and the relevant parameters of the given models are determined. Afterwards, their effects on the performance of IEEE 802.11aj WLAN system are investigated.Next, the dissertation introduces three typical I/Q imbalance estimation and compensation algorithms including self-adaptive method, blind estimation method, the training sequence based method, and the merit and demerit of these estimation approaches are analyzed. Then, a joint transmitter (TX) and receiver (RX) estimation and compensation algorithm is proposed to estimate and compensate frequency-selective I/Q imbalance. The simulation results show that the effectiveness and accuracy of the proposed method are superior to the existing algorithms, and the proposed algorithm has a lower computational complexity.Finally, in order to simulate the actual situation closely, a new two-step algorithm for estimating I/Q imbalance and DC offset is proposed. Combined with previous proposed loop-back structure, DC offset is eliminated by time domain average method firstly, then I/Q imbalance is estimated by the training sequence based method. Simulation results show that the proposed algorithm can effectively eliminate the influence of I/Q imbalance and DC offset with a very low complexity.By estimating and compensating the hardware impairments in millimeter-wave wireless communication, this thesis provides system designers with useful guidance and suggestions for the design of IEEE 802.11 aj WLAN standard.