287 research outputs found
Intelligent Processing in Wireless Communications Using Particle Swarm Based Methods
There are a lot of optimization needs in the research and design of wireless communica- tion systems. Many of these optimization problems are Nondeterministic Polynomial (NP) hard problems and could not be solved well. Many of other non-NP-hard optimization problems are combinatorial and do not have satisfying solutions either. This dissertation presents a series of Particle Swarm Optimization (PSO) based search and optimization algorithms that solve open research and design problems in wireless communications. These problems are either avoided or solved approximately before.
PSO is a bottom-up approach for optimization problems. It imposes no conditions on the underlying problem. Its simple formulation makes it easy to implement, apply, extend and hybridize. The algorithm uses simple operators like adders, and multipliers to travel through the search space and the process requires just five simple steps. PSO is also easy to control because it has limited number of parameters and is less sensitive to parameters than other swarm intelligence algorithms. It is not dependent on initial points and converges very fast.
Four types of PSO based approaches are proposed targeting four different kinds of problems in wireless communications. First, we use binary PSO and continuous PSO together to find optimal compositions of Gaussian derivative pulses to form several UWB pulses that not only comply with the FCC spectrum mask, but also best exploit the avail- able spectrum and power. Second, three different PSO based algorithms are developed to solve the NLOS/LOS channel differentiation, NLOS range error mitigation and multilateration problems respectively. Third, a PSO based search method is proposed to find optimal orthogonal code sets to reduce the inter carrier interference effects in an frequency redundant OFDM system. Fourth, a PSO based phase optimization technique is proposed in reducing the PAPR of an frequency redundant OFDM system. The PSO based approaches are compared with other canonical solutions for these communication problems and showed superior performance in many aspects. which are confirmed by analysis and simulation results provided respectively. Open questions and future
Open questions and future works for the dissertation are proposed to serve as a guide for the future research efforts
Multidimensional Index Modulation for 5G and Beyond Wireless Networks
This study examines the flexible utilization of existing IM techniques in a
comprehensive manner to satisfy the challenging and diverse requirements of 5G
and beyond services. After spatial modulation (SM), which transmits information
bits through antenna indices, application of IM to orthogonal frequency
division multiplexing (OFDM) subcarriers has opened the door for the extension
of IM into different dimensions, such as radio frequency (RF) mirrors, time
slots, codes, and dispersion matrices. Recent studies have introduced the
concept of multidimensional IM by various combinations of one-dimensional IM
techniques to provide higher spectral efficiency (SE) and better bit error rate
(BER) performance at the expense of higher transmitter (Tx) and receiver (Rx)
complexity. Despite the ongoing research on the design of new IM techniques and
their implementation challenges, proper use of the available IM techniques to
address different requirements of 5G and beyond networks is an open research
area in the literature. For this reason, we first provide the dimensional-based
categorization of available IM domains and review the existing IM types
regarding this categorization. Then, we develop a framework that investigates
the efficient utilization of these techniques and establishes a link between
the IM schemes and 5G services, namely enhanced mobile broadband (eMBB),
massive machine-type communications (mMTC), and ultra-reliable low-latency
communication (URLLC). Additionally, this work defines key performance
indicators (KPIs) to quantify the advantages and disadvantages of IM techniques
in time, frequency, space, and code dimensions. Finally, future recommendations
are given regarding the design of flexible IM-based communication systems for
5G and beyond wireless networks.Comment: This work has been submitted to Proceedings of the IEEE for possible
publicatio
Joint signal detection and channel estimation in rank-deficient MIMO systems
L'évolution de la prospère famille des standards 802.11 a encouragé le développement des technologies appliquées aux réseaux locaux sans fil (WLANs). Pour faire face à la toujours croissante nécessité de rendre possible les communications à très haut débit, les systèmes à antennes multiples (MIMO) sont une solution viable. Ils ont l'avantage d'accroître le débit de transmission sans avoir recours à plus de puissance ou de largeur de bande. Cependant, l'industrie hésite encore à augmenter le nombre d'antennes des portables et des accésoires sans fil. De plus, à l'intérieur des bâtiments, la déficience de rang de la matrice de canal peut se produire dû à la nature de la dispersion des parcours de propagation, ce phénomène est aussi occasionné à l'extérieur par de longues distances de transmission. Ce projet est motivé par les raisons décrites antérieurement, il se veut un étude sur la viabilité des transcepteurs sans fil à large bande capables de régulariser la déficience de rang du canal sans fil. On vise le développement des techniques capables de séparer M signaux co-canal, même avec une seule antenne et à faire une estimation précise du canal. Les solutions décrites dans ce document cherchent à surmonter les difficultés posées par le medium aux transcepteurs sans fil à large bande. Le résultat de cette étude est un algorithme transcepteur approprié aux systèmes MIMO à rang déficient
System design and validation of multi-band OFDM wireless communications with multiple antennas
[no abstract
Low-complexity iterative frequency domain decision feedback equalization
Single-carrier transmission with frequency domain equalization (SC-FDE) offers a viable design alternative to the classic orthogonal frequency division multiplexing technique. However, SC-FDE using a linear equalizer may suffer from serious performance deterioration for transmission over severely frequency-selective fading channels. An effective method of solving this problem is to introduce non-linear decision feedback equalization (DFE) to SC-FDE. In this contribution, a low complexity iterative decision feedback equalizer operating in the frequency domain of single-carrier systems is proposed. Based on the minimum mean square error criterion, a simplified parameter estimation method is introduced to calculate the coefficients of the feed-forward and feedback filters, which significantly reduces the implementation complexity of the equalizer. Simulation results show that the performance of the proposed simplified design is similar to the traditional iterative block DFE under various multipath fading channels but it imposes a much lower complexity than the latter
Distributed space time block coding and application in cooperative cognitive relay networks
The design and analysis of various distributed space time block coding
schemes for cooperative relay networks is considered in this thesis.
Rayleigh frequency flat and selective fading channels are assumed to
model the links in the networks, and interference suppression techniques
together with an orthogonal frequency division multiplexing (OFDM)
type transmission approach are employed to mitigate synchronization
errors at the destination node induced by the different delays through
the relay nodes.
Closed-loop space time block coding is first considered in the context
of decode-and-forward (regenerative) networks. In particular, quasi orthogonal
and extended orthogonal coding techniques are employed for
transmission from four relay nodes and parallel interference cancellation
detection is exploited to mitigate synchronization errors. Availability
of a direct link between the source and destination nodes is studied.
Outer coding is then added to gain further improvement in end-to-end
performance and amplify-and-forward (non regenerative) type networks
together with distributed space time coding are considered to reduce
relay node complexity. A novel detection scheme is then proposed
for decode-and-forward and amplify-and-forward networks with closed-loop
extended orthogonal coding and closed-loop quasi-orthogonal coding
which reduce the computational complexity of the parallel interference cancellation. The near-optimum detector is presented for relay
nodes with single or dual antennas. End-to-end bit error rate simulations
confirm the potential of the approach and its ability to mitigate
synchronization errors
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