17 research outputs found
Towards the Next Generation of Location-Aware Communications
This thesis is motivated by the expected implementation of the
next generation mobile networks (5G) from 2020, which is being
designed with a radical paradigm shift towards millimeter-wave
technology (mmWave). Operating in 30--300 GHz frequency band
(1--10 mm wavelengths), massive antenna arrays that provide a
high angular resolution, while being packed on a small area will
be used. Moreover, since the abundant mmWave spectrum is barely
occupied, large bandwidth allocation is possible and will enable
low-error time estimation. With this high spatiotemporal
resolution, mmWave technology readily lends itself to extremely
accurate localization that can be harnessed in the network design
and optimization, as well as utilized in many modern
applications. Localization in 5G is still in early stages, and
very little is known about its performance and feasibility.
In this thesis, we contribute to the understanding of 5G mmWave
localization by focusing on challenges pertaining to this
emerging technology. Towards that, we start by considering a
conventional cellular system and propose a positioning method
under outdoor LOS/NLOS conditions that, although approaches the
Cram\'er-Rao lower bound (CRLB), provides accuracy in the order
of meters. This shows that conventional systems have limited
range of location-aware applications. Next, we focus on mmWave
localization in three stages. Firstly, we tackle the initial
access (IA) problem, whereby user equipment (UE) attempts to
establish a link with a base station (BS). The challenge in this
problem stems from the high directivity of mmWave. We investigate
two beamforming schemes: directional and random. Subsequently, we
address 3D localization beyond IA phase. Devices nowadays have
higher computational capabilities and may perform localization in
the downlink. However, beamforming on the UE side is sensitive to
the device orientation. Thus, we study localization in both the
uplink and downlink under multipath propagation and derive the
position (PEB) and orientation error bounds (OEB). We also
investigate the impact of the number of antennas and the number
of beams on these bounds. Finally, the above components assume
that the system is synchronized. However, synchronization in
communication systems is not usually tight enough for
localization. Therefore, we study two-way localization as a means
to alleviate the synchronization requirement and investigate two
protocols: distributed (DLP) and centralized (CLP).
Our results show that random-phase beamforming is more
appropriate IA approach in the studied scenarios. We also observe
that the uplink and downlink are not equivalent, in that the
error bounds scale differently with the number of antennas, and
that uplink localization is sensitive to the UE orientation,
while downlink is not. Furthermore, we find that NLOS paths
generally boost localization. The investigation of the two-way
protocols shows that CLP outperforms DLP by a significant margin.
We also observe that mmWave localization is mainly limited by
angular rather than temporal estimation.
In conclusion, we show that mmWave systems are capable of
localizing a UE with sub-meter position error, and sub-degree
orientation error, which asserts that mmWave will play a central
role in communication network optimization and unlock
opportunities that were not available in the previous generation
Error Bounds for Uplink and Downlink 3D Localization in 5G mmWave Systems
Location-aware communication systems are expected to play a pivotal part in
the next generation of mobile communication networks. Therefore, there is a
need to understand the localization limits in these networks, particularly,
using millimeter-wave technology (mmWave). Towards that, we address the uplink
and downlink localization limits in terms of 3D position and orientation error
bounds for mmWave multipath channels. We also carry out a detailed analysis of
the dependence of the bounds of different systems parameters. Our key findings
indicate that the uplink and downlink behave differently in two distinct ways.
First of all, the error bounds have different scaling factors with respect to
the number of antennas in the uplink and downlink. Secondly, uplink
localization is sensitive to the orientation angle of the user equipment (UE),
whereas downlink is not. Moreover, in the considered outdoor scenarios, the
non-line-of-sight paths generally improve localization when a line-of-sight
path exists. Finally, our numerical results show that mmWave systems are
capable of localizing a UE with sub-meter position error, and sub-degree
orientation error.Comment: This manuscripts is updated following two rounds of reviews at IEEE
Transactions on Wireless Communications. More discussion is included in
different parts of the paper. Results are unchanged, and are still vali
Single-Anchor Two-Way Localization Bounds for 5G mmWave Systems
Recently, millimeter-wave (mmWave) 5G localization has been shown to be to
provide centimeter-level accuracy, lending itself to many location-aware
applications, e.g., connected autonomous vehicles (CAVs). One assumption
usually made in the investigation of localization methods is that the user
equipment (UE), i.e., a CAV, and the base station (BS) are {time} synchronized.
In this paper, we remove this assumption and investigate two two-way
localization protocols: (i) a round-trip localization protocol (RLP), whereby
the BS and UE exchange signals in two rounds of transmission and then
localization is achieved using the signal received in the second round; (ii) a
collaborative localization protocol (CLP), whereby localization is achieved
using the signals received in the two rounds. We derive the position and
orientation error bounds applying beamforming at both ends and compare them to
the traditional one-way localization. Our results show that mmWave localization
is mainly limited by the angular rather than the temporal estimation and that
CLP significantly outperforms RLP. Our simulations also show that it is more
beneficial to have more antennas at the BS than at the UE.Comment: This version is accepted for publication as a paper in the IEEE
Transactions on Vehicular Technolog
Interference Mitigating Satellite Broadcast Receiver using Reduced Complexity List-Based Detection in Correlated Noise
The recent commercial trends towards using smaller dish antennas for satellite receivers, and the growing density of broadcasting satellites, necessitate the application of robust adjacent satellite interference (ASI) cancellation schemes. This orbital density growth along with the wider beamwidth of a smaller dish have imposed an overloaded scenario at the satellite receiver, where the number of transmitting satellites exceeds the number of receiving elements at the dish antenna. To ensure successful operation in this practical scenario, we propose a satellite receiver that enhances signal detection from the desired satellite by mitigating the interference from neighboring satellites. Towards this objective, we propose a reduced complexity list-based group-wise search detection (RC-LGSD) receiver under the assumption of spatially correlated additive noise. To further enhance detection performance, the proposed satellite receiver utilizes a newly designed whitening filter to remove the spatial correlation amongst the noise parameters, while also applying a preprocessor that maximizes the signal-to-interference-plus-noise ratio (SINR). Extensive simulations under practical scenarios show that the proposed receiver enhances the performance of satellite broadcast systems in the presence of ASI compared to existing methods
Random-Phase Beamforming for Initial Access in Millimeter-Wave Cellular Networks
The utilization of the millimeter-wave frequency band
(mm-wave) in the fifth generation (5G) of mobile communication is
a highly-debated current topic. Mm-wave MIMO systems will use
arrays with large number of antennas at the transmitter and the
receiver, implemented on a relatively small area. With the inherent
high directivity of these arrays, algorithms to help the user
equipment find the base station and establish a communication
link should be carefully designed. Towards that, we examine
two beamforming schemes, namely, random-phase beamforming
(RPBF) and directional beamforming (DBF), and test their impact
on the Cramer-Rao lower bounds (CRB) of jointly estimating the ´
direction-of-arrival, direction-of-departure, time-of-arrival, and
the complex channel gain, under the line-of-sight channel model.
The results show that the application of RPBF is more appropriate
in the considered scenario as it attains a lower CRB with fewer
beams compared to DB.ARC Discovery Projects Grant DP14010113
Interference Mitigating Satellite Broadcast Receiver using Reduced Complexity List-Based Detection in Correlated Noise
The recent commercial trends towards using smaller dish antennas for satellite receivers, and the growing
density of broadcasting satellites, necessitate the application of robust adjacent satellite interference (ASI)
cancellation schemes. This orbital density growth along with the wider beamwidth of a smaller dish have
imposed an overloaded scenario at the satellite receiver, where the number of transmitting satellites exceeds
the number of receiving elements at the dish antenna. To ensure successful operation in this practical scenario,
we propose a satellite receiver that enhances signal detection from the desired satellite by mitigating the
interference from neighboring satellites. Towards this objective, we propose a reduced complexity list-based
group-wise search detection (RC-LGSD) receiver under the assumption of spatially correlated additive noise.
To further enhance detection performance, the proposed satellite receiver utilizes a newly designed whitening
filter to remove the spatial correlation amongst the noise parameters, while also applying a preprocessor that
maximizes the signal-to-interference-plus-noise ratio (SINR). Extensive simulations under practical scenarios
show that the proposed receiver enhances the performance of satellite broadcast systems in the presence of
ASI compared to existing method