687 research outputs found
Interference Mitigation Scheme in 3D Topology IoT Network with Antenna Radiation Pattern
Internet of things (IoT) is one of main paradigms for 5G wireless systems.
Due to high connection density, interference from other sources is a key
problem in IoT networks. Especially, it is more difficult to find a solution to
manage interference in uncoordinated networks than coordinated system. In this
work, we consider 3D topology of uncoordinated IoT network and propose
interference mitigation scheme with respect to 3D antenna radiation pattern. In
2D topology network, the radiation pattern of dipole antenna can be assumed as
onmi-directional. We show the variance of antenna gain on dipole antenna in 3D
topology, consider the simultaneous use of three orthogonal dipole antennas,
and compare the system performance depending on different antenna
configurations. Our simulation results show that proper altitude of IoT devices
can extensively improve the system performance
AirSync: Enabling Distributed Multiuser MIMO with Full Spatial Multiplexing
The enormous success of advanced wireless devices is pushing the demand for
higher wireless data rates. Denser spectrum reuse through the deployment of
more access points per square mile has the potential to successfully meet the
increasing demand for more bandwidth. In theory, the best approach to density
increase is via distributed multiuser MIMO, where several access points are
connected to a central server and operate as a large distributed multi-antenna
access point, ensuring that all transmitted signal power serves the purpose of
data transmission, rather than creating "interference." In practice, while
enterprise networks offer a natural setup in which distributed MIMO might be
possible, there are serious implementation difficulties, the primary one being
the need to eliminate phase and timing offsets between the jointly coordinated
access points.
In this paper we propose AirSync, a novel scheme which provides not only time
but also phase synchronization, thus enabling distributed MIMO with full
spatial multiplexing gains. AirSync locks the phase of all access points using
a common reference broadcasted over the air in conjunction with a Kalman filter
which closely tracks the phase drift. We have implemented AirSync as a digital
circuit in the FPGA of the WARP radio platform. Our experimental testbed,
comprised of two access points and two clients, shows that AirSync is able to
achieve phase synchronization within a few degrees, and allows the system to
nearly achieve the theoretical optimal multiplexing gain. We also discuss MAC
and higher layer aspects of a practical deployment. To the best of our
knowledge, AirSync offers the first ever realization of the full multiuser MIMO
gain, namely the ability to increase the number of wireless clients linearly
with the number of jointly coordinated access points, without reducing the per
client rate.Comment: Submitted to Transactions on Networkin
Partial OFDM Symbol Recovery to Improve Interfering Wireless Networks Operation in Collision Environments
The uplink data rate region for interfering transmissions in wireless networks has been characterised and proven, yet its underlying model assumes a complete temporal overlap. Practical unplanned networks, however, adopt packetized transmissions and eschew tight inter-network coordination, resulting in packet collisions that often partially overlap, but rarely ever completely overlap. In this work, we report a new design called (), that specifically targets the parts of data symbols that experience no interference during a packet collision. bootstraps a successive interference cancellation (SIC) like decoder from these strong signals, thus improving performance over techniques oblivious to such partial packet overlaps. We have implemented on the WARP software-defined radio platform and in trace-based simulation. Our performance evaluation presents experimental results from this implementation operating in a 12node software network testbed, spread over two rooms in a nonlineofsight indoor office environment. Experimental results confirm that our proposal decoder is capable of decoding up to 60 % of collided frames depending on the type of data and modulation used. This consistently leads to throughput enhancement over conventional WiFi under different scenarios and for the various data types tested, namely downlink bulk TCP, downlink videoondemand, and uplink UDP
Towards hydro-transparency on the Euphrates-Tigris basin: mapping surface water changes in Iraq, 1984â2015
This policy paper uses open-source software to examine surface water changes in the Euphrates-Tigris Basin from 1984â2015, focusing on Iraq â a downstream riparian state. The timeline captures the impact on Iraq of upstream dam construction, notably in Turkey and Iran, conflicts, and political transformations, and a period of protracted drought across the basin between 2007â18. Between 1984â2015, the area of permanent water in Iraq declined by a third, with greatest losses in the south. There was an 86 percent reduction in area of the Mesopotamian Marshes. In contrast, over the same period, the area of permanent water in Turkey increased by over a quarter. Mapping long-term changes in the occurrence and variability of surface water is a necessary step in achieving greater hydro-transparency; that is, the open availability of information on the movement, storage and management of water within and across state borders. Increased hydro-transparency, through the public provision of evidence-based information, can build trust between the riparian states (Turkey, Syria, Iraq and Iran), informing options for more sustainable, equitable and reasonable utilisation of basin flows
Non-Orthogonal Signal and System Design for Wireless Communications
The thesis presents research in non-orthogonal multi-carrier signals, in which: (i) a new signal format termed truncated orthogonal frequency division multiplexing (TOFDM) is proposed to improve data rates in wireless communication systems, such as those used in mobile/cellular systems and wireless local area networks (LANs), and (ii) a new design and experimental implementation of a real-time spectrally efficient frequency division multiplexing (SEFDM) system are reported. This research proposes a modified version of the orthogonal frequency division multiplexing (OFDM) format, obtained by truncating OFDM symbols in the time-domain. In TOFDM, subcarriers are no longer orthogonally packed in the frequency-domain as time samples are only partially transmitted, leading to improved spectral efficiency. In this work, (i) analytical expressions are derived for the newly proposed TOFDM signal, followed by (ii) interference analysis, (iii) systems design for uncoded and coded schemes, (iv) experimental implementation and (v) performance evaluation of the new proposed signal and system, with comparisons to conventional OFDM systems. Results indicate that signals can be recovered with truncated symbol transmission. Based on the TOFDM principle, a new receiving technique, termed partial symbol recovery (PSR), is designed and implemented in software de ned radio (SDR), that allows efficient operation of two users for overlapping data, in wireless communication systems operating with collisions. The PSR technique is based on recovery of collision-free partial OFDM symbols, followed by the reconstruction of complete symbols to recover progressively the frames of two users suffering collisions. The system is evaluated in a testbed of 12-nodes using SDR platforms. The thesis also proposes channel estimation and equalization technique for non-orthogonal signals in 5G scenarios, using an orthogonal demodulator and zero padding. Finally, the implementation of complete SEFDM systems in real-time is investigated and described in detail
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