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The femtocell is a promising technology that can be employed to enhance next generation wireless network coverage. It possesses the potential to reduce network deployment risk, improve network operation efficiency and capacity. By utilizing femtocells spectrum utilization can be improved. Due to its key features, including low cost, high speed, and plug and play capability, network operators should...
In order to reduce the traffic load in cellular network and improve the data rates for users located in an indoor environment the Femtocells are used to solve the poor indoor coverage problem. It represents a cost-effective solution compared to other solutions such as Picocells and distributed antenna systems. However, if the signal-to-noise ratio is high then UEs can receive good throughput. For...
This paper investigates the resource allocation problem in heterogeneous cognitive radio networks (HCRNs). In this paper, two types of users, i.e., multi-homing and single-network cognitive radio users (CRUs), are considered to coexist in HCRNs. Multi-homing CRUs can access multiple networks simultaneously, while single-network CRUs can be served by only one network at a time. With the aim of maximizing...
Non-Orthogonal Multiple Access (NOMA) is a promising multiple access technique for 5G wireless communication networks due to its higher spectral efficiency and user fairness. Power allocation is the key to improve the performance of NOMA systems. In this paper, we focus on a certain NOMA group of a hybrid NOMA system. We formulate a sum-throughput maximization problem for uplink under the constraints...
Increased demand for wireless services has spurred research into spectrum co-existence between radar and communication systems. The effect of an unaltered radar interference on an uncoded communication receiver has been investigated for constellations used in commercial systems. However, the constellation design — possible for a cognitive transmitter-receiver pair — that maximizes the transmission...
In this paper, a non-orthogonal multiple access cognitive radio network with simultaneous wireless information and power transfer is studied under a practical non-linear energy harvesting model. A multi-objective optimization problem(MOOP) is formulated to maximize the harvesting power of each energy harvesting receiver. This problem is non-convex and challenging to be solved. The weighted Tchebycheff...
We propose novel resource allocation algorithms that have the objective of finding a good tradeoff between resource reuse and interference avoidance in wireless networks. To this end, we first study properties of functions that relate the resource budget available to network elements to the optimal utility and to the optimal resource efficiency obtained by solving max-min utility optimization problems...
We study a cognitive radio network in which two sources communicate with each other through multiple relays operating in non-overlapping frequency bands in the radio spectrum. We consider the problem of optimizing the transmission powers of the sources and relays so that the minimum of the two sources' transmission capacities is maximized. Thanks to the non-overlapping nature of the relays' signals,...
Conventional radar generally uses fixed transmit waveform, which is difficult to obtain optimal target detection performance in the presence of interference. To solve this problem, a joint optimization algorithm of waveform and receiving filter for MIMO radar is proposed. Firstly, the maximization of output signal to interference plus noise ratio is used as objective function. The joint optimization...
Coordinated multipoint transmission (CoMP) and soft frequency reuse (SFR) are two popular techniques used to control the deleterious effects caused by inter-cell interference in current 4G and envisaged 5G cellular networks. The performance of the combination of CoMP and SFR has been shown to be strongly influenced by the specific choice of the parameters governing the action of both mechanisms. Unfortunately,...
In this work, we propose a mobility management optimization framework for the networks employing full-frequency reuse. The mobility management issue is considered in the context of two main self-organizing networks (SON) functionalities, i.e mobility load balancing (MLB) and mobility robustness optimization (MRO) as a user-to-BS assigment problem. A central optimization method, which aims to maximize...
The lifetime of machine to machine (M2M) communication networks plays significant impact on system performance and user quality of service (QoS). To increase network lifetime, efficient resource allocation schemes can be applied. In this paper, we study the network lifetime maximization problem of an M2M communication network consisting one base station (BS) and a number of machine type communications...
Due to the openness of the physical layer, the physical layer security has been widely discussed. It is considered as an effective way to improve the secrecy rate that we add artificial noise to D2D communications underlaying cellular networks. Compared to previous studies, in this paper we not only think of the situation where artificial noise is added to the original communication signal between...
Orthogonal frequency division multiplexing access (OFDMA) inherently suffers from large spectral sidelobes, which will lead to interference between users and can not be ignored. In this paper, in order to suppress spectral sidelobes, we propose a novel windowing scheme. The derivation of the optimum window function is based on the solution of an optimization problem. It aims to minimize in-band-out-of-subband...
A well known challenge in linearly-constrained beamforming is how to suppress multiple interferences when the degrees of freedom (DoF) provided by the array are fewer than the number of sources in the environment. In this paper, we propose a beamformer design to address this challenge. Specifically, we propose a min-max beam-former design that penalizes the spatial responses on all interferences'...
The Device-to-Device (D2D) communication underlaying cellular networks has advantages of improving the spectral utilization, data rate, and energy efficiency. This paper studies a position-based mode selection and resource allocation scheme for D2D communications underlaying cellular networks. With position information available, first an offline channel state information (CSI) retrieval model is...
Plane wave methods for ultrafast ultrasound imaging suffer from a low signal to noise ratio (SNR) and a limited field of view at greater imaging depths. Imaging using multiple focused coded beams in parallel is one strategy for high speed imaging that may improve on these limitations. However, the SNR and resolution of this strategy are degraded by interference between the beams transmitted in parallel...
Plane wave methods for ultrafast ultrasound imaging suffer from a low signal to noise ratio (SNR) and a limited field of view at greater imaging depths. Imaging using multiple focused coded beams in parallel is one strategy for high speed imaging that may improve on these limitations. However, the SNR and resolution of this strategy are degraded by the interference between the beams transmitted in...
In this paper, a joint cross-layer design of adaptive modulation and coding (AMC) and cooperative automatic repeat request (C-ARQ) scheme is proposed for a secondary user in a shared-spectrum environment. First, based on the statistical descriptions of the channel, closed-form expressions of the average spectral efficiency (SE) and the average packet loss rate (PLR) are presented. Then, the cross-layer...
Device-to-device (D2D) will be the future of wireless technology with low power, high data rate and low latency for information exchange between wireless devices. However it may not be always feasible because of mobility and influence of surroundings on the devices. This paper presents an approach to model and investigate D2D network at two millimeter wave (mmW) frequencies of 28 and 60 GHz, by calculating...
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