Abstract-We investigate the spectral efficiency of full-duplex small cell wireless systems, in which a full-duplex capable base station (BS) is designed to send/receive data to/from multiple halfduplex users on the same system resources. The major hurdle for designing such systems is due to the self-interference at the BS and co-channel interference among users. Hence, we consider a joint beamformer design to maximize the spectral efficiency subject to certain power constraints. The design problem is first formulated as a rank-constrained optimization one, and the rank relaxation method is then applied. However the relaxed problem is still nonconvex, and thus optimal solutions are hard to find. Herein, we propose two provably convergent algorithms to obtain suboptimal solutions. Based on the concept of the Frank-Wolfe algorithm, we approximate the design problem by a determinant maximization program in each iteration of the first algorithm. The second method is built upon the sequential parametric convex approximation method, which allows us to transform the relaxed problem into a semidefinite program in each iteration. Extensive numerical experiments under small cell setups illustrate that the full-duplex system with the proposed algorithms can achieve a large gain over the half-duplex one.Index Terms-Full-duplex, self-interference, transmit beamforming, D.C. program, semidefinite programming.
Abstract-We introduce a model for capturing the effects of beam misdirection on coverage and throughput in a directional wireless network using stochastic geometry. In networks employing ideal sector antennas without sidelobes, we find that concavity of the orientation error distribution is sufficient to prove monotonicity and quasi-concavity (both with respect to antenna beamwidth) of spatial throughput and transmission capacity, respectively. Additionally, we identify network conditions that produce opposite extremal choices in beamwidth (absolutely directed versus omni-directional) that maximize the two related throughput metrics. We conclude our paper with a numerical exploration of the relationship between mean orientation error, throughput-maximizing beamwidths, and maximum throughput, across radiation patterns of varied complexity.
Future digital society depends heavily on timely availability of high quality wireless connectivity the offering of which today is dominated by mobile network operators (MNOs). Future 5G systems aim at connecting billions of devices to serve versatile location and case specific needs of vertical sectors in parallel with the provisioning of traditional mobile broadband services. As the majority of mobile traffic originates from indoors, cost-efficient and fast deployment of new indoor small cell networks is fundamental, which calls for new developments in regulation and technology to enable new business. This paper proposes the concept of micro operators (uO) for local service delivery in 5G to build indoor small cell communication infrastructure and offer context related services and content. Key elements of the new micro operator concept are introduced including regulation-related factors of local spectrum access rights, and technology-related factors of flexible network implementation. Several business opportunities are identified for the uO concept including the provisioning of hosted local connectivity to all MNOs in specific locations, operation of secure networks for vertical sector specific use, and offering of locally tailored content and services.
While 5G is being rolled out in different parts of the globe, few research groups around the world − such as the Finnish 6G Flagship program − have already started posing the question: What will 6G be? The 6G vision is a data-driven society, enabled by near instant unlimited wireless connectivity. Driven by impetus to provide vertical-specific wireless network solutions, machine type communication encompassing both its mission critical and massive connectivity aspects is foreseen to be an important cornerstone of 6G development. This article presents an over-arching vision for machine type communication in 6G. In this regard, some relevant performance indicators are first anticipated, followed by a presentation of six key enabling technologies.
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