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This paper addresses the problem of maximizing the weighted signal-to-interference-plus-noise-ratio (SINR) targets at user terminals in a distributed manner in multicell interference networks. The optimization is constrained to strict individual base station (BS) transmit power limitations in the presence of imperfect channel state information (CSI). This problem is numerically intractable due to...
The capacity performance of ICIC has been extensively studied in coordinated multi-point transmissions (CoMP). In practice however, due to limited feedback, the acquired channel direction information (CDI), which is crucial for ICIC, is often partially available. Hence one may question whether the ICIC is able to meet the Quality-of- Service (QoS) requirements. This paper considers the optimal partitioning...
Unmanned aerial vehicles (UAVs) can be used as aerial base stations (BSs) to deliver broadband wireless connectivity during temporary events, at hotspot areas, or after disasters that may destroy existing communication infrastructure. Since UAV- BSs are low power nodes, their efficient placement is important to reap the maximum capacity and coverage benefits from their deployments. By making use of...
Cognitive radio (CR) has been advocated to improve the network spectrum efficiency for decades, and the cooperation between the primary and secondary systems has become a new paradigm to further improve the spectrum utilization. However, in practice, secondary transmitters (STs) are usually power constrained, which limits the application of cooperative cognitive radio networks (CCRN). In this paper,...
This paper considers the problem of maximizing energy efficiency on the downlink of two-tier wireless backhaul small cell heterogeneous networks, where an interference mitigation strategy that combines reverse time division duplexing and equally orthogonal spectrum splitting is proposed. By enabling the small cell access points with the capability of switching ON/OFF, we develop a joint design of...
We propose a novel model for the NLOS interference power distribution in a cellular system employing MIMO beamforming transmission in mmWave spectrum. The proposed model is a mixture of the Inverse Gaussian and the Inverse Weibull distributions, both are two-parameter medium-to-heavy tail distributions. To estimate the parameters of the mixture model, we design an expectation maximization algorithm...
In this paper, we propose an adaptive filtering algorithm, Hybrid Recursive and Least Mean Square-based Constant Modulus Algorithm (RLS-LMS-CMA) for optimized blind beamforming for a Uniform Linear Array (ULA). We consider that Recursive Least Square-based Constant Modulus Algorithm (RLS-CMA) and Least Mean Square-based Constant Modulus Algorithm (LMS-CMA) algorithms are time tested. Therefore, we...
Abstract-Conventional cloud radio access networks assume single cloud processing and treat inter-cloud interference as background noise. This paper considers the downlink of a multi-cloud radio access network (CRAN) where each cloud is connected to several base-stations (BS) through limited-capacity wireline backhaul links. The set of BSs connected to each cloud, called cluster, serves a set of pre-known...
A cloud radio access network (Cloud-RAN) is a network architecture that holds onto the promise of meeting the explosive growth of mobile data traffic. Cloud-RAN consists a central processor (CP) connecting to multiple multi-antenna base stations (BSs) via finite-capacity backhaul links. To reduce the backhaul traffic, BS-level caching technique is utilized in which the popular contents are pre-fetched...
The Radio Access Network based on Fog computing (F- RAN) has been recently proposed to alleviate the heavy burden on backhauls of Cloud Radio Access Network (C-RAN). Equipping the edge device of C-RAN with local storage module (cache) is a specific realization of F-RAN. Some frequently requested files are cached at the Radio Units (RUs), both the traffic load and the overall delay can be reduced....
In this paper, we propose beamforming schemes to simultaneously transmit data to multiple information receivers (IRs) while transfering power wirelessly to multiple energy-harvesting receivers (ERs). Taking into account the imperfection of the instantaneous channel state information, we introduce a probabilistic-constrained optimization problem to minimize the total transmit power while guaranteeing...
In this paper, we consider a cloud radio access network (CRAN) with full duplex (FD) remote radio heads (RRHs) and half duplex mobile users. Compared with half duplex RRHs, though FD-RRHs can simultaneously transmit and receive data streams, they also suffer from new interference sources such as self-interference and inter-RRH interference. With FDRRHs, the downlink mobile users (DMUs) are also interfered...
We consider a cognitive radio scenario in which two networks share a licensed spectrum. Primary network is the legitimate network while cognitive radio network utilizes the underutilized frequency sub bands. For this scenario our focus is primarily on controlling the interference to the legitimate user and in addition, to minimize the interference between the secondary users while assuring quality...
Although Fractional Frequency Reuse (FFR) is a good solution for Inter-Cell Interference (ICI) problem, combined FFR and beamforming can be utilized for more improved cellular system performance. In this paper, we consider a hexagonal cellular network, where we derive the Downlink (DL) worst case Signal to Interference Ratio (SIR) closed form formula for three different beamforming techniques (horizontal,...
Recently, a subspace-constrained diagonal loading (SSC-DL) method has been proposed for robust beamforming against the mismatched direction of arrival (DoA) issue. Although SSC-DL has outstanding output SINR performance, it is not clear how to choose the DL factor and subspace dimension in practice. The aim of the present study is to further investigate conditions on optimal parameters for SSC-DL...
Due to the open and shared nature, wireless communication systems are vulnerable to jamming attacks. Beamforming is a promising technique to counteract the impact of jamming attacks. However, when the location of the desired signal is close to that of the jamming signal, the performance of the traditional anti-jamming beamformer that uses isotropic antenna elements is significantly degraded due to...
Smart antennas are widely used for wireless communications due to their ability to increase the coverage and capacity of communication systems. Adaptive algorithm is one of the core technologies of smart antenna. Adaptive beamforming can receive signal from a certain direction by adjusting the array weight vector to enhance the desired signal and suppress the interference and noise. This paper proposes...
Robust adaptive beamforming (RAB) has became a popular research topic, with various RAB techniques being proposed in the past decades. However, because the sample covariance matrix rather than the interference-plus-noise co-variance matrix is used to calculate the weight vector, the performance of the previously developed RAB techniques is not optimal. In this paper, a novel RAB algorithm, which uses...
The existing adaptive beamforming techniques developed for underwater sensor array usually suffer from significant performance degradation due to the mismatch between the presumed and actual steering vectors. In this paper, a novel convex optimization based robust adaptive beamforming algorithm is proposed. First, the steering vector corresponding to the desired signal is estimated by solving a convex...
In this paper, we introduce a procedure for the null broadening algorithm design with respect to the perturbation of the interference location. This method is based on maximizing the array output signal-to-interference-plus-noise-ratio (SINR) subject to quadratic constraints. The design problem can be cast as a fractional quadratically constrained quadratic programming (QCQP) problem that can be solved...
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