Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Joint Device Positioning and Clock Synchronization in 5G Ultra-Dense
  Networks   In this article, we address the prospects and key enabling technologies for
highly efficient and accurate device positioning and tracking in 5G radio
access networks. Building on the premises of ultra-dense networks as well as on
the adoption of multicarrier waveforms and antenna arrays in the access nodes
(ANs), we first formulate extended Kalman filter (EKF)-based solutions for
computationally efficient joint estimation and tracking of the time of arrival
(ToA) and direction of arrival (DoA) of the user nodes (UNs) using uplink
reference signals. Then, a second EKF stage is proposed in order to fuse the
individual DoA/ToA estimates from one or several ANs into a UN position
estimate. Since all the processing takes place at the network side, the
computing complexity and energy consumption at the UN side are kept to a
minimum. The cascaded EKFs proposed in this article also take into account the
unavoidable relative clock offsets between UNs and ANs, such that reliable
clock synchronization of the access-link is obtained as a valuable by-product.
The proposed cascaded EKF scheme is then revised and extended to more general
and challenging scenarios where not only the UNs have clock offsets against the
network time, but also the ANs themselves are not mutually synchronized in
time. Finally, comprehensive performance evaluations of the proposed solutions
on a realistic 5G network setup, building on the METIS project based outdoor
Madrid map model together with complete ray tracing based propagation modeling,
are provided. The obtained results clearly demonstrate that by using the
developed methods, sub-meter scale positioning and tracking accuracy of moving
devices is indeed technically feasible in future 5G radio access networks
operating at sub-6GHz frequencies, despite the realistic assumptions related to
clock offsets and potentially even under unsynchronized network elements.

12
The categories of this paper are: nucl-th
21
The categories of this paper are: adap-org
25
The categories of this paper are: patt-sol
9
The categories of this paper are: nlin
36
The categories of this paper are: cmp-lg
31
The categories of this paper are: ao-sci
3
The categories of this paper are: physics
26
The categories of this paper are: bayes-an
22
The categories of this paper are: chao-dyn
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The categories of this paper are: funct-an
34
The categories of this paper are: chem-ph
10
The categories of this paper are: q-bio
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The categories of this paper are: econ
20
The categories of this paper are: acc-phys
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The categories of this paper are: atom-ph
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The categories of this paper are: eess