Localization error bounds for 5G mm-wave systems under hardware impairments

Localization and location aware systems are expected to be counted as one of the main services of 5G millimeter wave (mmWave) communication systems. mmWave communication systems are offering a large bandwidth from 30-300 GHz frequency band along with low latency communications. Although, they use massive number of antennas at their transmitters and receivers, their transceivers occupy a very small area, in order of centimeters. These features make 5G mmWave communication systems an exceptional candidate for the localization services. However, mmWave suffers from some limitations such as high vulnerability to the environment and hardware deficiency. The hardware used in mmWave system’s transceivers including power amplifiers and analog/digital converters, cannot be manufactured perfectly as of high costs. Therefore, it is highly probabilistic to see a non-linear behavior coming out of the mmWave transceivers, known as hardware impairments (HWIs). HWIs is generally caused as a result of nonlinearity of transmitter power amplifier and receiver low noise amplifier (LNA) as well as analog to digital (ADC) and digital to analog converters (DAC). Moreover, HWIs is the general form of phase noise and In/Quadrature phase (I/Q) imbalance. Because of the mmWave’s nature, even a slight shortcoming can cause severe effects on its performance. This thesis investigates the possible effects of HWIs on the user localization error bounds. Towards that and focusing on line-of-sight (LOS) path, we derive the Cramer-Rao Lower Bound (CRLB) for the user equipment (UE)’s location and orientation by starting with a conventional two dimension (2D) scenario and then, we extend it to the realistic three dimensional (3D) scenario. [...

Localization Error Bounds for 5G mmWave Systems under I/Q Imbalance

Location awareness is expected to play a significant role in 5G millimeter-wave (mmWave) communication systems. One of the basic elements of these systems is quadrature amplitude modulation (QAM), which has in-phase and quadrature (I/Q) modulators. It is not uncommon for transceiver hardware to exhibit an imbalance in the I/Q components, causing degradation in data rate and signal quality. Under an amplitude and phase imbalance model at both the transmitter and receiver, 2D positioning performance in 5G mmWave systems is considered. Towards that, we derive the position and orientation error bounds and study the effects of the I/Q imbalance parameters on the derived bounds. The numerical results reveal that I/Q imbalance impacts the performance similarly, whether it occurs at the transmitter or the receiver, and can cause a degradation up to 12% in position and orientation estimation accuracy