15 research outputs found
Smart Passive Localization Using Time Difference of Arrival
A smart passive localization system using time difference of arrival (TDoA) measurements is designed and analyzed with the goal of providing the position information for the construction of frequency allocation maps
Multi-source parameter estimation and tracking using antenna arrays
This thesis is concerned with multi-source parameter estimation and tracking using antenna arrays in wireless communications. Various multi-source parameter estimation and tracking algorithms are presented and evaluated.
Firstly, a novel multiple-input multiple-output (MIMO) communication system is proposed for multi-parameter channel estimation. A manifold extender is presented for increasing the degrees of freedom (DoF). The proposed approach utilises the extended manifold vectors together with superresolution subspace type algorithms, to achieve the estimation of delay, direction of departure (DOD) and direction of arrival (DOA) of all the paths of the desired user in the presence of multiple access interference (MAI).
Secondly, the MIMO system is extended to a virtual-spatiotemporal system by incorporating the temporal domain of the system towards the objective of further increasing the degrees of freedom. In this system, a multi-parameter es-
timation of delay, Doppler frequency, DOD and DOA of the desired user, and a beamformer that suppresses the MAI are presented, by utilising the proposed virtual-spatiotemporal manifold extender and the superresolution subspace type
algorithms.
Finally, for multi-source tracking, two tracking approaches are proposed based on an arrayed Extended Kalman Filter (arrayed-EKF) and an arrayed Unscented Kalman Filter (arrayed-UKF) using two type of antenna arrays: rigid array and
flexible array. If the array is rigid, the proposed approaches employ a spatiotemporal state-space model and a manifold extender to track the source parameters, while if it is flexible the array locations are also tracked simultaneously.
Throughout the thesis, computer simulation studies are presented to investigate and evaluate the performance of all the proposed algorithms.Open Acces
Analysis of data-aided channel tracking for hybrid massive MIMO systems in millimeter wave communications
As the data traffic in future wireless communications will explosively grow up to 1000
folds by the deployment of 5G, several technologies are emerging to satisfy this demand, including
massive multiple-input multiple-output (MIMO), millimeter wave(mmWave) communications,
Non-Orthogonal Multiple Access (NOMA), etc. The combination of millimeter
wave communication and massive MIMO is a promising solution since it can provide tens
of GHz bandwidth by fundamentally exploring higher unoccupied spectrum resources. As
the wavelength of higher frequency shrinks, it is possible to design more compact antenna
array with a very large number of antennas. However, this will cause enormous hardware
cost, energy consumption and computation complexity of decent RF(Radio Frequency)
chains. To this end, spatial sparsity is widely explored to enable hybrid mmWave massive
MIMO systems with limited RF chains to achieve high spectral and energy efficiency.
On the other hand, channel estimation problem for systems with limited RF chains
is quite challenging due to the unaffordable overhead. To be specific, the conventional
pilot-based channel estimation requires to repeatedly transmit the same pilot because only
a limited number of antennas will be activated for each time slot. Therefore, it consumes
a huge amount of temporal and spectral resources. To overcome this problem, channel
estimation for mmWave massive MIMO systems is still an on-going research area. Among
plenty of candidates, channel tracking is the most promising one. To achieve the extremely
low cost and complexity, which is also the greatest motivation of this thesis, data-aided
channel tracking method is thoroughly investigated with closed-form CRLB(Cram´er-Rao
lower bound). In this thesis, data-aided channel tracking systems with different types of
antenna, including ULA(Uniform Linear Antenna array), DLA(Discrete Lens Antenna ar
ray) and UPA(Uniform Planar Antenna array), are comprehensively studied and proposed,
and the closed-form expressions of the corresponding CRLBs are carefully derived. The
numerical results of the simulations for each case are shown respectively, and they reveal
that the performance of the proposed data-aided channel tracking system approaches the
CRLB very well.
In addition, to further explore the data-aided channel tracking system, the multi-user
scenario is investigated in this thesis. This is motivated by the highway and high-speed
railway application, where overtaking operation happens frequently. In this case, the users
in the same beam suffer from high channel interference, thus degrading the channel estimation
performance or even causing outage. To deal with this issue, we proposed an
estimated SER(Symbol Error Rate) metric to indicate if a scheduling operation is necessary
to be taken place and restart of the whole channel tracking system is required. This
metric is included as the Update phase in the proposed channel tracking method for multiuser
scenario with DLA. The theoretical SER closed-form expression is also derived for
multi-user data detection. The numerical results of the simulations verified the theoretical
SER expression, and the scheduling metric based on the estimated SER performance is
also discussed