1,018 research outputs found
Sparse Signal Processing Concepts for Efficient 5G System Design
As it becomes increasingly apparent that 4G will not be able to meet the
emerging demands of future mobile communication systems, the question what
could make up a 5G system, what are the crucial challenges and what are the key
drivers is part of intensive, ongoing discussions. Partly due to the advent of
compressive sensing, methods that can optimally exploit sparsity in signals
have received tremendous attention in recent years. In this paper we will
describe a variety of scenarios in which signal sparsity arises naturally in 5G
wireless systems. Signal sparsity and the associated rich collection of tools
and algorithms will thus be a viable source for innovation in 5G wireless
system design. We will discribe applications of this sparse signal processing
paradigm in MIMO random access, cloud radio access networks, compressive
channel-source network coding, and embedded security. We will also emphasize
important open problem that may arise in 5G system design, for which sparsity
will potentially play a key role in their solution.Comment: 18 pages, 5 figures, accepted for publication in IEEE Acces
Outage Performance of Two-Hop OFDM Systems with Spatially Random Decode-and-Forward Relays
In this paper, we analyze the outage performance of different multicarrier
relay selection schemes for two-hop orthogonal frequency-division multiplexing
(OFDM) systems in a Poisson field of relays. In particular, special emphasis is
placed on decode-and-forward (DF) relay systems, equipped with bulk and
per-subcarrier selection schemes, respectively. The exact expressions for
outage probability are derived in integrals for general cases. In addition,
asymptotic expressions for outage probability in the high signal-to-noise ratio
(SNR) region in the finite circle relay distribution region are determined in
closed forms for both relay selection schemes. Also, the outage probabilities
for free space in the infinite relay distribution region are derived in closed
forms. Meanwhile, a series of important properties related to cooperative
systems in random networks are investigated, including diversity, outage
probability ratio of two selection schemes and optimization of the number of
subcarriers in terms of system throughput. All analysis is numerically verified
by simulations. Finally, a framework for analyzing the outage performance of
OFDM systems with spatially random relays is constructed, which can be easily
modified to analyze other similar cases with different forwarding protocols,
location distributions and/or channel conditions
Advanced DSP Algorithms For Modern Wireless Communication Transceivers
A higher network throughput, a minimized delay and reliable communications
are some of many goals that wireless communication standards, such as the fifthgeneration
(5G) standard and beyond, intend to guarantee for its customers. Hence,
many key innovations are currently being proposed and investigated by researchers in
the academic and industry circles to fulfill these goals. This dissertation investigates
some of the proposed techniques that aim at increasing the spectral efficiency, enhancing
the energy efficiency, and enabling low latency wireless communications systems.
The contributions lay in the evaluation of the performance of several proposed receiver
architectures as well as proposing novel digital signal processing (DSP) algorithms to
enhance the performance of radio transceivers. Particularly, the effects of several radio
frequency (RF) impairments on the functionality of a new class of wireless transceivers,
the full-duplex transceivers, are thoroughly investigated. These transceivers are then
designed to operate in a relaying scenario, where relay selection and beamforming
are applied in a relaying network to increase its spectral efficiency. The dissertation
then investigates the use of greedy algorithms in recovering orthogonal frequency
division multiplexing (OFDM) signals by using sparse equalizers, which carry out the
equalization in a more efficient manner when the low-complexity single tap OFDM
equalizer can no longer recover the received signal due to severe interferences. The
proposed sparse equalizers are shown to perform close to conventional optimal and
dense equalizers when the OFDM signals are impaired by interferences caused by the
insertion of an insufficient cyclic prefix and RF impairments
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