Error Bounds for Localization in mmWave MIMO Systems: Effects of Hardware Impairments Considering Perfect and Imperfect Clock Synchronization

Localization demands high-accuracy positioning, and this rings especially true in the context of fifth-generation (5G) millimeter-wave (mmWave) systems. However, it is easier said than done. mmWave systems require a large number of antennas to be deployed at the transceiver, so having ideal hardware components at each antenna is unrealistic. Degradation in the received signal, caused by hardware impairments (HWIs), affects the spectral efficiency, which in turn influences user positioning. Moreover, a high level of clock synchronization between the base station (BS) and the user equipment (UE) is rarely achieved. In this article, we investigate the effect of HWIs on UE localization under synchronous and asynchronous conditions. In order to minimize imperfect synchronization, two anchors or two-way localization protocols, a round-trip (RLP) as well as a collaborative localization protocol (CLP) are used. Conducting the localization process using the BS, we find the position and orientation bounds. We then study the effect of HWIs on the error bounds under the mentioned scenarios. Our numerical results show that HWIs have a significant impact on localization in all conditions, localization using two anchors and the CLP being more robust, however, against HWIs. Based on our outcome, compensating for imperfect synchronization using RLP does not increase the resilience of the system against HWIs.