Abstract
The question how a 5G communication system will look like has been addressed intensely in numerous research projects and in standardization bodies. In the massively connected world of the “Internet of Things” (IoT), it is getting more and more important to be aware of where all these “things” are located. Mobile radio-based technologies envisaged for a 5G system will play an essential role in providing high-accuracy positioning of the “things.” In this work, we will first address the fundamental Cramér-Rao lower bound (CRLB) of time of arrival (TOA) estimation in an orthogonal frequency-division multiplexing (OFDM)-based system (such as 4G and 5G) using the pilots. The achievable performance is compared with the 3GPP LTE and potential future 5G requirements. The Ziv-Zakai lower bound (ZZLB) is also considered for TOA estimation, as it is tighter than the CRLB for medium to low signal-to-noise ratios (SNRs). We show how to optimize the waveform in order to reduce the TOA estimation error. Then, we describe some practical low-complexity maximum likelihood (ML) methods for TOA estimation with enhanced first-arriving path detection. Simulation results show that such adaptive ML methods can in some cases (e.g., line of sight) achieve a performance close to the CRLB. Finally, we will briefly discuss cooperation-based positioning, which will become increasingly important for massively connected IoT.
Highlights
Mobile communication has become an integrated part of our daily lives
In order to increase the effective bandwidth of the positioning reference signals (PRSs), which decreases the energy and time needed for the PRS, long-term evolution (LTE)-M supports frequency hopping, but NB-internet of things (IoT) currently only supports artificial frequency hopping by configuring the PRS onto multiple NarrowBand IoT (NB-IoT) carriers [15], see e.g., [16] for a study on its performance
The narrowband PRS (NPRS) occupies at least 10 subframes consisting of 14 subsequent orthogonal frequency-division multiplexing (OFDM) symbols each, which are all used for the NPRS in guard band and standalone operation mode [2]
Summary
Mobile communication has become an integrated part of our daily lives. Whereas the state-of-the-art fourth generation (4G) wireless standard long-term evolution (LTE) has been in use for a decade, the fifth generation (5G) wireless standard called new radio (NR) is being specified for diverse applications in the 10 years. In the first 5G NR release, Release 15, 60 The Fifth Generation (5G) of Wireless Communication mainly the enhanced mobile broadband (eMBB) use cases have been considered. The ultra-reliable low latency communication (URLLC) use cases will be addressed in Release 16. Other use cases such as massive machine-type communication (mMTC) as well as the internet of things (IoT) are expected to be taken into account later. Mobile radio-based technologies envisaged for a 5G system will play an essential role in providing high-accuracy positioning of the “things.”
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