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We study the problem of interference mitigation in a phased array, where a subset containing k out of a total of N receivers creates a virtual spatial null for an incoming interference. The signal-of-interest and interference are represented by their corresponding steering vectors, and an optimum subarray is chosen such that the two vectors are as orthogonal as possible. This optimization is a binary...
We consider a multi-user (MU) multiple-input-single-output (MISO) downlink system with M single-antenna users and N transmit antennas with a nonlinear power amplifier (PA) at each antenna. Instead of emitting constant envelope (CE) signals from the antennas to have highly power efficient PAs, we relax the CE constraint and allow the transmit signals to have instantaneous power less than or equal to...
In view of dynamic multi-criteria decision-making problems, in which the criteria value of alternatives are three-parameters interval numbers and criteria exists different natural states, a dynamic grey stochastic multi-criteria decision-making method is proposed. According to the stationary distribution thought of Markov chain, the final state of natural possibility is obtained. The time information...
In this work, we present a novel robust distributed beam-forming (RDB) approach to mitigate the effects of channel errors on wireless networks equipped with relays based on the exploitation of the cross-correlation between the received data from the relays at the destination and the system output. The proposed RDB method, denoted cross-correlation and subspace projection (CCSP) RDB, considers a total...
Personal audio reproduction systems deal with the creation of personal sound zones within a room without the necessity of using headphones. These systems use an array of loudspeakers and design the required filters at each loudspeaker in order to render the desired audio signal to each person in the room as free of interferences as possible. There are very interesting proposals in the literature that...
Through implementing the equal-strength analysis based on unified strength theory, strength calculation formulas of two-and three-layer prestressed combined dies for cold extrusion were derived in this investigation. Two parameters were included in the suggested strength expression, parameter α presenting/considering the difference between material tensile and compressive properties, and...
With the densification of heterogeneous networks in terms of both users and base stations (BS) being identified as an integral part of future communication systems, the problem of association needs to be reconsidered since conventional schemes which are simply based on the received signal strength lead to small cells being idle. Coordinated multipoint (CoMP) techniques show great potential in improving...
A scenario consisting of several cells is considered where each cell contains a multiple-antenna enhanced remote radio head (eRRH) and several single-antenna mobile stations (MSs). All eRRHs can access the cloud with limited capacity fronthaul links. The beamforming problem aiming at maximizing the sum rate with per eRRH power constraint is considered. In this paper, a hierarchical one-shot top-down...
This paper considers a multiuser system with one full-duplex (FD) base station (BS) serving a set of half duplex (HD) mobile users. Due to the self-interference and co-channel interference from the uplink users to the downlink users, the transmissions of the BS and uplink users have to jointly designed. In this paper, we consider such a joint design problem for maximizing the max-min-fairness (MMF)...
The new networking paradigm of opportunistic spectrum sharing is a promising technology for mitigating the scarcity of spectrum, which has resulted from the exponential increase in the number of wireless devices and ubiquitous services. In light of the new concept of Authorized/Licensed Shared Access (ASA/LSA), in this work, we consider the coexistence and spectrum sharing between a collocated multiple-input-multiple-output...
A secrecy transmission method with robust power control is investigated in this paper for a downlink two-tier femtocell network, where an eavesdropper attempts to wiretap the legitimate macrocell users. Considering the imperfect channel gains, a probability constraint robust optimization problem is formulated to satisfy the quality-of-service (QoS) of users. We aim to maximize the secrecy rate with...
User fairness and spectrum efficiency are conflicting objectives in cellular system optimization given that users share limited spectrum resources. Users at the cell edge are more likely to be unfairly treated due to their disadvantageous locations, where they experience high path losses and strong interferences if co-channel transmission exists. In this paper, a cell edge boundary is obtained and...
Ultra-dense cellular networks are emerging as one key characteristic of 5G wireless networks. In this context, frequency reuse is a fundamental technology enabler for efficient utilization of limited spectrum resources. In this paper, we investigate the in-band Full-Duplex (FD) self-backhauling architecture, in which Base Stations (BSs) operate on the same spectrum used by the users to access the...
In this paper, we study new schemes to maximize network and users' minimum EE energy efficiency through transmission power control. The problem is formulated as fractional optimization programming and solved with a successive convex approximation. The EE metrics are analysed via extensive numerical simulations under different clustering algorithms, namely a variant of nearest neighbor clustering and...
In this paper, we investigate the problem of finding optimal location of the relay node in an underlay cognitive full-duplex relay (CogFDR) network. First of all, an analytical model for the outage probability experienced by the secondary user in a CogFDR network assuming Rayleigh fading channel and neglecting the interference from the primary transmitter is considered. Then, a non-linear optimization...
A decentralized power adjustment scheme based on non-cooperative game theory in a dense heterogeneous femtocell network is studied. Transmission power of the femtocell base stations are adjusted independently in a self-organizing manner to maximize the corresponding utility function, which consists of the signal-to-interference plus noise ratio and the transmission power of the femtocell base stations...
In this paper, we propose a joint analog-digital (AD) beamforming scheme that exploits the mutual coupling effect to further improve the performance of multi-user multiple-input single-output (MU-MISO) systems. We firstly propose a joint AD scheme by iteratively optimizing the beamforming vectors in the digital domain and the load impedances of each antenna element in the analog domain. We further...
In this paper, under the situation of multiple interference regions, an optimal antenna placement problem for a distributed Multi-Input Multi-Output (MIMO) radar is studied. Considering multiple interference regions, we solve the antenna placement problem by utilizing antenna placement method based on Multi-Objective Particle Swarm Optimization (MOPSO). However, it is not clear when to stop the iteration...
The individual applications of network coded opportunistic routing and successive interference cancellation have been proven with significant improvement on throughput performance of wireless multi-hop networks, but there lacks practical optimization on their combination application. Based on a TDMA system, this paper models the throughput maximization as network utility function maximization problem...
In this paper, the problem of joint users' uplink transmission power and rate allocation in NOMA wireless networks is studied, under the scenario that each user is simultaneously requesting multiple services. Each user is associated with a two-variable utility function that represents his satisfaction from his allocated resources (i.e., power and rate). In order to appropriately reflect the combined...
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