Long-distance Users Research Articles

Energy-Efficient Power Allocation and Relay Selection Schemes for Relay-Assisted D2D Communications in 5G Wireless Networks

Device-to-device (D2D) communications allows user equipment (UE) that are in close proximity to communicate with each other directly without using a base station. Relay-assisted D2D (RA-D2D) communications in 5G networks can be applied to support long-distance users and to improve energy efficiency (EE) of the networks. In this paper, we first establish a multi-relay system model where the D2D UEs can communicate with each other by reusing only one cellular uplink resource. Then, we apply an adaptive neuro-fuzzy inference system (ANFIS) architecture to select the best D2D relay to forward D2D source information to the expected D2D destination. Efficient power allocation (PA) in the D2D source and the D2D relay are critical problems for operating such networks, since the data rate of the cellular uplink and the maximum transmission power of the system need to be satisfied. As is known, 5G wireless networks also aim for low energy consumption to better implement the Internet of Things (IoT). Consequently, in this paper, we also formulate a problem to find the optimal solutions for PA of the D2D source and the D2D relay in terms of maximizing the EE of RA-D2D communications to support applications in the emerging IoT. To solve the PA problems of RA-D2D communications, a particle swarm optimization algorithm is employed to maximize the EE of the RA-D2D communications while satisfying the transmission power constraints of the D2D users, minimum data rate of cellular uplink, and minimum signal-to-interference-plus-noise-ratio requirements of the D2D users. Simulation results reveal that the proposed relay selection and PA methods significantly improve EE more than existing schemes.

Semidefinite Relaxation and Approximation Analysis of a Beamformed Alamouti Scheme for Relay Beamforming Networks

In this paper, we study the amplify-and-forward (AF) schemes in two-hop one-way relay networks. In particular, we consider the multigroup multicast transmission between long-distance users. Given that perfect channel state information is perceived, our goal is to design the AF process so that the max-min-fair (MMF) signal-to-interference-plus-noise ratio (SINR) is optimized subject to generalized power constraints. We propose a rank-two beamformed Alamouti (BFA) AF scheme and formulate the corresponding AF design problem as a \emph{two-variable} fractional quadratically-constrained quadratic program (QCQP), which is further tackled by the semidefinite relaxation (SDR) technique. We analyze the approximation quality of two-variable fractional SDRs under the Gaussian randomization algorithm. These results are fundamentally new and reveal that the proposed BFA AF scheme can outperform the traditional BF AF scheme, especially when there are many users in the system or many generalized power constraints in the problem formulation. From a practical perspective, the BFA AF scheme offers two degrees of freedom (DoFs) in beamformer design, as opposed to the one DoF offered by the BF AF scheme, to improve the receivers' SINR. In the latter part of this paper, we demonstrate how this extra DoF leads to provable performance gains by considering two special cases of multicasting, where the AF process is shown to employ a special structure. The numerical simulations further validate that the proposed BFA AF scheme outperforms the BF AF scheme and works well for large-scale relay systems.

Schemes generating entangled states and entanglement swapping between photons and three-level atoms inside optical cavities for quantum communication

We propose quantum information processing schemes based on cavity quantum electrodynamics (QED) for quantum communication. First, to generate entangled states (Bell and Greenberger---Horne---Zeilinger [GHZ] states) between flying photons and three-level atoms inside optical cavities, we utilize a controlled phase flip (CPF) gate that can be implemented via cavity QED). Subsequently, we present an entanglement swapping scheme that can be realized using single-qubit measurements and CPF gates via optical cavities. These schemes can be directly applied to construct an entanglement channel for a communication system between two users. Consequently, it is possible for the trust center, having quantum nodes, to accomplish the linked channel (entanglement channel) between the two separate long-distance users via the distribution of Bell states and entanglement swapping. Furthermore, in our schemes, the main physical component is the CPF gate between the photons and the three-level atoms in cavity QED, which is feasible in practice. Thus, our schemes can be experimentally realized with current technology.

A Stochastic Beamformed Amplify-and-Forward Scheme in a Multigroup Multicast MIMO Relay Network with Per-Antenna Power Constraints

In this paper, we consider a two-hop one-way relay network for multigroup multicast transmission between long-distance users, in which the relay is equipped with multiple antennas, while the transmitters and receivers are all with a single antenna. Assuming that the perfect channel state information is available, we study amplify-and-forward (AF) schemes that aim at optimizing the max–min-fair (MMF) rate. We begin by considering the classic beamformed AF (BF-AF) scheme, whose corresponding MMF design problem can be formulated as a rank-constrained fractional semidefinite program (SDP). We show that the gap between the BF-AF rate and the SDR rate associated with an optimal SDP solution is sensitive to the number of users as well as the number of power constraints in the relay system. This reveals that the BF-AF scheme may not be well suited for large-scale systems. We, therefore, propose the stochastic beamformed AF (SBF-AF) schemes, which differ from the BF-AF scheme in that time-varying AF weights are used. We prove that the MMF rates of the proposed SBF-AF schemes are at most 0.8317 bits/s/Hz less than the SDR rate, irrespective of the number of users or power constraints. Thus, SBF-AF can outperform BF-AF especially in large-scale systems. Finally, we present numerical results to demonstrate the viability of our proposed schemes.

Competing with Whom? Where? and Why (Not)? an Empirical Study of U.S. Online Newspapers’ Competition Dynamics

As a newspaper Web site theoretically may compete with anything and everything, online and offline, this study empirically examines the nature, degree, and locale of online newspaper competition. Based on online reader survey data collected from users of 27 local U.S. newspaper Web sites, this study seeks to capture the competitive relationship between the local newspaper site and other online/offline news sources among local and long-distance users. A competitive relationship between the newspaper site and its print counterpart in the local market was found among about one third of the cases, after controlling for demographics and Internet use. Theoretical and managerial implications are discussed.

Are Long-Distance Users an Inconvenient Truth? Profiling U.S. Newspapers' Online Readership in the Dual-Geographic Market

In response to the newspaper crisis, U.S. newspapers are seeking new business models for their online operation, but often ignore non-local readers who constitute a non-traditional niche audience with market potential. This study attempts to expand the understanding of the U.S. online newspaper readership in the dual-geographic market by empirically comparing local and long-distance users on demographic characteristics, online behavior, and satisfaction level with the newspaper site. Utilizing a dataset containing 28 newspaper Web sites' 25,964 visitors, this study performed a large-scale, in-depth analysis of online newspapers' long-distance readership unseen in previous research. Results show that more than one fourth of these newspaper sites' online users reside outside the print market. Most long-distance users have personal ties with the geographic area associated with the newspaper. Compared with local users, long-distance users tend to be male, older, better educated, and with a higher income. They are more likely to obtain local sports information from the site, but are less likely to visit the classifieds areas of the site. They also tend to be more loyal to and satisfied with the newspaper site. Newspapers should perceive long-distance users as a potential audience segment rather than an inconvenient truth when developing content, pricing, and marketing strategies.

Valuing the Effect of Regulation on New Services in Telecommunications

THIS PAPER DEALS with how to value the introduction of new services in telecommunications. Much public discussion has centered on the evolving information superhighway as well as on the many new services that may be offered as high-capacity fiber optic transmission networks are extended into the telecommunications infrastructure. The Federal Communications Commission (FCC) has decided to tax longdistance users to subsidize Internet access to schools and libraries. The cost is estimated to exceed $2 billion a year. Numerous cable companies, such as Time Warner, have announced plans to upgrade their current coaxial-based networks to combined fiber-coax networks. This increased transmission capacity will allow many more channels of entertainment, high-speed access to information, and new interactive services. How can society establish the value of these new services and increased choices? This question has potentially important economic consequences and equally important public policy implications. Because of the network structure of telecommunications, public policy has always played a large role in its production and regulation. In countries such as the United States and Canada, very strict regulation (which is only slowly being loosened) has limited the ability of companies to compete freely in telecommunications. By demonstrating how to value new telecommunications services, I allow for a more reasoned approach to the necessary benefit-cost calculations; this approach can help both

Support Services for Campus Remote Users

Abstract Library remote users are often thought of as long-distance users of the library. As libraries begin to provide electronic databases through campus backbones a new group of remote users will emerge. Campus remote users are in a unique situation which requires support services that blend services provided to patrons who come into the library and those who are long-distance users. This article offers tips and suggestions in providing support services to campus remote users.