1,376 research outputs found
Unmanned Aerial Vehicles (UAVs) for Integrated Access and Backhaul (IAB) Communications in Wireless Cellular Networks
An integrated access and backhaul (IAB) network architecture can enable flexible and fast deployment of next-generation cellular networks. However, mutual interference between access and backhaul links, small inter-site distance and spatial dynamics of user distribution pose major challenges in the practical deployment of IAB networks. To tackle these problems, we leverage the flying capabilities of unmanned aerial vehicles (UAVs) as hovering IAB-nodes and propose an interference management algorithm to maximize the overall sum rate of the IAB network. In particular, we jointly optimize the user and base station associations, the downlink power allocations for access and backhaul transmissions, and the spatial configurations of UAVs. We consider two spatial configuration modes of UAVs: distributed UAVs and drone antenna array (DAA), and show how they are intertwined with the spatial distribution of ground users. Our numerical results show that the proposed algorithm achieves an average of 2.9× and 6.7× gains in the received downlink signal-to-interference-plus-noise ratio (SINR) and overall network sum rate, respectively. Finally, the numerical results reveal that UAVs cannot only be used for coverage improvement but also for capacity boosting in IAB cellular networks
Effective relaying mechanisms in future device to device communication : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in School of Food and Advanced Technology at Massey University, Palmerston North, New Zealand
Listed in 2020 Dean's List of Exceptional ThesesFuture wireless networks embrace a large number of assorted network-enabled devices
such as mobile phones, sensor nodes, drones, smart gears, etc., with different applications
and purpose, but they all share one common characteristic which is the dependence
on strong network connectivity. Growing demand of internet-connected devices
and data applications is burdensome for the currently deployed cellular wireless networks.
For this reason, future networks are likely to embrace cutting-edge technological
advancements in network infrastructure such as, small cells, device-to-device communication,
non-orthogonal multiple access scheme (NOMA), multiple-input-multiple out,
etc., to increase spectral efficiency, improve network coverage, and reduce network latency.
Individual devices acquire network connectivity by accessing radio resources in
orthogonal manner which limits spectrum utilisation resulting in data congestion and
latency in dense cellular networks. NOMA is a prominent scheme in which multiple
users are paired together and access radio resources by slicing the power domain. While
several research works study power control mechanisms by base station to communicate
with NOMA users, it is equally important to maintain distinction between the
users in uplink communication. Furthermore, these users in a NOMA pair are able to
perform cooperative relaying where one device assists another device in a NOMA pair
to increase signal diversity. However, the benefits of using a NOMA pair in improving
network coverage is still overlooked. With a varierty of cellular connected devices, use
of NOMA is studied on devices with similar channel characteristics and the need of
adopting NOMA for aerial devices has not been investigated. Therefore, this research
establishes a novel mechanism to offer distinction in uplink communication for NOMA
pair, a relaying scheme to extend the coverage of a base station by utilising NOMA
pair and a ranking scheme for ground and aerial devices to access radio resources by
NOMA
Multipacket reception in the presence of in-band full-duplex communication
In-Band Full-DupleX (IB-FDX) is defined as the ability for nodes to transmit and receive
signals simultaneously on the same channel. Conventional digital wireless networks
do not implement it, since a node’s own transmission signal causes interference to the
signal it is trying to receive. However, recent studies attempt to overcome this obstacle,
since it can potentially double the spectral efficiency of current wireless networks.
Different mechanisms exist today that are able to reduce a significant part of the Self-
Interference (SI), although specially tuned Medium Access Control (MAC) protocols are
required to optimize its use. One of IB-FDX’s biggest problems is that the nodes’ interference range is extended, meaning the unusable space for other transmissions and receptions is broader. This dissertation proposes using MultiPacket Reception (MPR) to address this issue and adapts an already existing Single-Carrier with Frequency-Domain Equalization (SC-FDE) receiver to IB-FDX. The performance analysis suggests that MPR and IB-FDX have a strong synergy and are able to achieve higher data rates, when used together. Using analytical models, the optimal transmission patterns and transmission power were identified, which maximize the channel capacity with the minimal energy consumption. This was used to define a new MAC protocol, named Full-duplex Multipacket reception Medium Access Control (FM-MAC). FM-MAC was designed for a single-hop cellular infrastructure, where the Access Point (AP) and the terminals implement both IB-FDX and MPR. It divides the coverage range of the AP into a closer Full-DupleX (FDX) zone and a farther Half-DupleX (HDX) zone and adds a tunable fairness mechanism to avoid terminal starvation. Simulation results show that this protocol provides efficient support for both HDX and FDX terminals, maximizing its capacity when more FDX terminals are used
Quantifying Potential Energy Efficiency Gain in Green Cellular Wireless Networks
Conventional cellular wireless networks were designed with the purpose of
providing high throughput for the user and high capacity for the service
provider, without any provisions of energy efficiency. As a result, these
networks have an enormous Carbon footprint. In this paper, we describe the
sources of the inefficiencies in such networks. First we present results of the
studies on how much Carbon footprint such networks generate. We also discuss
how much more mobile traffic is expected to increase so that this Carbon
footprint will even increase tremendously more. We then discuss specific
sources of inefficiency and potential sources of improvement at the physical
layer as well as at higher layers of the communication protocol hierarchy. In
particular, considering that most of the energy inefficiency in cellular
wireless networks is at the base stations, we discuss multi-tier networks and
point to the potential of exploiting mobility patterns in order to use base
station energy judiciously. We then investigate potential methods to reduce
this inefficiency and quantify their individual contributions. By a
consideration of the combination of all potential gains, we conclude that an
improvement in energy consumption in cellular wireless networks by two orders
of magnitude, or even more, is possible.Comment: arXiv admin note: text overlap with arXiv:1210.843
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