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In licensed shared access (LSA) the radio spectrum is dynamically shared between an incumbent and one or more licensee systems. Protective measures are applied to the licensees’ communication activity to protect the normal operation of the incumbent system. Such measures are therefore crucial components of the LSA, and thus fundamentally affect the achievable spectrum efficiency. In this paper, we investigate a vertical LSA including an airport traffic control system, as the incumbent, and a mobile network as the licensee. While some previous works only consider the licensee uplink, we analytically obtain the interference received by the incumbent from the licensee's transmission both in the uplink and downlink. We then obtain optimal uplink and downlink power allocation in the licensee using an optimisation problem with the objective of maximizing licensee's spectral efficiency (SE) subject to the incumbent interference threshold. Furthermore, we investigate the effect of the number of users and cell size on the SE. Our results provide quantitative insights for practical system design and deployment of LSA system. We then examine the whole LSA spectrum utilization by characterising the availability of the LSA spectrum using a tandem queue setting. Using this model we obtain an expression for the spectral utilization as a function of the licensee's achievable spectral efficiency and the statistics of the LSA spectrum availability. Simulation results show more than a seven-fold improvement in the licensee SE using the optimal power allocation. It is also seen that a higher SE gain is achieved with the proposed optimal power allocation in cases where the number of user equipment in the eNodeB coverage area is very small. Furthermore, higher spectrum utilization efficiency is achieved as a result of shorter busy period and higher achievable SE for distant cells. [ABSTRACT FROM AUTHOR]

We propose a novel scheme for downlink beamforming design in an underlay cognitive cellular system. The beamforming design is formulated as an optimization problem with the objective of keeping the cognitive base station transmit power as well as the induced interference on the primary users, below predefined system thresholds. This is subject to providing a certain level of signal-to-interference-plus-noise ratio (SINR) to the secondary users. We then derive the corresponding semidefinite programming form for the formulated optimization problem and propose an iterative algorithm to obtain the beamforming vectors as the optimal solutions. We further analytically show the convergence of the proposed iterative algorithm. Extensive simulations verify that the proposed algorithm quickly converges to the optimal solution. We then compare the proposed scheme with a benchmarking system defined based on the previous methods proposed in the related literature. Comparisons show that the proposed algorithm outperforms the benchmarking system and induces lower interference at the primary service receivers. It is also observed that the proposed algorithm offers a higher sum rate in comparison to the benchmarking system. Simulation results further reveal that the proposed approach effectively works at a relatively high SINR level required by secondary users and strict interference threshold set by the primary system while the benchmarking system fails to do so. [ABSTRACT FROM AUTHOR]

In this paper, we present a novel and rather simple method for calculating reverse-link outage probability in signal-to-interference ratio (SIR)-based power-controlled direct-sequence code-division multiple access (DS-CDMA) systems. We obtain outage probability for a single-service system using the interference-to-received-signal-power ratio. We extend our method to the multiservice case using the uplink load factor, which is the ratio of the interference to the interference plus noise. Unlike most of the previous works, we employ the 2-D Poisson point process to model the spatial distribution of mobile users in the network coverage area. We approximate the intercell-interference-to-received-signal-power ratio and uplink load factor using their cumulants and obtain the outage probabilities for single- and multiservice cases. Our approximations are verified using simulations. [ABSTRACT FROM AUTHOR]

A novel framework is proposed to model downlink resource allocation problem in multiservice direct-sequence code division multiple-access (DS-CDMA) cellular networks. This framework is based on a defined utility function, which leads to utilizing the network resources in a more efficient way. This utility function quantifies the degree of utilization of resources. As a matter of fact, using the defined utility function, users' channel fluctuations and their delay constraints along with the load conditions of all BSs are all taken into consideration. Unlike previous works, we solve the problem with the general objective of maximizing the total network utility instead of maximizing the achieved utility of each base station (BS). It is shown that this problem is equivalent to finding the optimum BS assignment throughout the network, which is mapped to a multidimensional multiple-choice knapsack problem (MMKP). Since MMKP is NP-hard, a polynomial-time suboptimal algorithm is then proposed to develop an efficient base-station assignment. Simulation results indicate a significant performance improvement in terms of achieved utility and packet drop ratio. [ABSTRACT FROM AUTHOR]

We propose a novel approach to derive an upper bound for the air interface blocking probability in a multi-service CDMA network with soft handoff (SHO) as a function of network load. This method requires only general assumptions made for network design and dimensioning. We obtain an approximated upper bound and compare it with the calculated values for the upper bound and with real network simulation results to show that our method with a reduced computational complexity is also accurate. [ABSTRACT FROM AUTHOR]

Efficient connectivity in cellular-connected unmanned aerial vehicles (UAV)s is limited by scarcity of the radio spectrum and strong inter-cell interference (ICI). To address these issues, we propose an aerial-terrestrial network non-orthogonal multiple access (ATN-NOMA) scheme. In this proposed scheme, we pair the aerial user (AU) and terrestrial user (TU) in a NOMA setting to leverage their asymmetric channel gains and rate demands in downlink communications. In ATN-NOMA, the strong ICI issue at the AU receiver is further managed by an elevation-angle based user association, equipping the AU with an adjustable beamwidth directional antenna, and forming a beamforming among the coordinated terrestrial base stations (BS)s. We then obtain the optimal beamwidth and suboptimal power allocation so that the TUs’ sum-rate is maximized subject to the AU’s Quality-of-Service (QoS) requirement. The corresponding optimization problem is non-convex in which we exploit the structure of the problem and apply successive convex approximation (SCA) to obtain a suboptimal solution. We then derive the statistical properties, which consequently enable us to estimate the aggregated ICI. In cases where no interfering BSs have the same elevation angle as the coordinated BSs, we further approximate the AU’s outage probability. We then compare the TUs’ sum-rate and the outage probability of the ATN-NOMA with multiple existing schemes. Extensive simulation results show that our proposed ATN-NOMA scheme outperforms existing schemes by 52-91% in terms of the sum-rate, and its analytical outage probability can be as low as the order of $10^{-17}$. Furthermore, we show that the pairing of AU and TU in multi-cell networks remains beneficial, subject to effective mitigation of ICI. [ABSTRACT FROM AUTHOR]

We study the coverage performance of multiantenna [multiple-input multiple-output (MIMO)] communications in heterogeneous networks (HetNets). Our main focus is on open-loop and multistream MIMO zero-forcing beamforming at the receiver. Network coverage is evaluated adopting tools from stochastic geometry. Besides fixed-rate transmission (FRT), we also consider adaptive-rate transmission (ART) while its coverage performance, despite its high relevance, has so far been overlooked. On the other hand, while the focus of the existing literature has solely been on the evaluation of coverage probability per stream, we target coverage probability per communication link&#x2014.comprising multiple streams—which is shown to be a more conclusive performance metric in multistream MIMO systems. This, however, renders various analytical complexities rooted in statistical dependence among streams in each link. Using a rigorous analysis, we provide closed-form bounds on the coverage performance for FRT and ART. These bounds explicitly capture impacts of various system parameters including densities of BSs, SIR thresholds, and multiplexing gains. Our analytical results are further shown to cover popular closed-loop MIMO systems, such as eigen-beamforming and space-division multiple access. The accuracy of our analysis is confirmed by extensive simulations. The findings in this paper shed light on several important aspects of dense MIMO HetNets: first, increasing the multiplexing gains yields lower coverage performance; second, densifying network by installing an excessive number of low-power femto BSs allows the growth of the multiplexing gain of high-power, low-density macro-BSs without compromising the coverage performance; and third, for dense HetNets, the coverage probability does not increase with the increase of deployment densities. [ABSTRACT FROM AUTHOR]

Wireless Power Transfer in the 5G frequency band is the most promising technology to power up ubiquitous small electronic devices as well as IoT devices. A strongly coupled magnetic resonance WPT technique that focuses on near-field electromagnetic energy has been proposed in this paper. However, most Magnetic Resonance Coupling Wireless Power Transfer (MRC WPT) applications have been designed in kHz and MHz frequency spectrum. This paper demonstrates Planar Spiral Coil Magnetic Resonance Coupling (PSC MRC) WPT designs at 5G (GHz) frequencies. Also, the transformation technique of the low frequency (kHz and MHz) magnetic resonance circuit model equations to high frequency (GHz) circuit model equations to achieve a high-efficiency power transfer. PSC MRC WPT designs structure antennas are designed at 3.4 - 3.5 GHz in the form of circular and square shapes with 1 turn coil. The proposed antenna structures are firstly being optimized in a full-wave electromagnetic simulator, CST Microwave Studio to resonate at the 3.4 - 3.5 GHz band. Then, the close-loop equations to determine the efficiency of 5G Magnetic Resonance Coupling Planar Spiral Coil Wireless Power Transfer is designed. Lastly, the results are compared with the simulation and calculated parts. The highest efficiency of the PSC MRC circular antenna is 31.58 % when the distance is at 2 mm, and 31.26 and 31.02 % when the distance is at 3 and 4 mm, respectively. The efficiency of circular PSC MRC is found to be 25 % better than the efficiency of square shape design. [ABSTRACT FROM AUTHOR]

In this paper, we develop quantized ergodic resource allocation in uplink orthogonal frequency-division multiple-access (OFDMA)-based relay-assisted networks in which both amplify-and-forward (AF) and decode-and-forward (DF) protocols are investigated. The main objective is to maximize the average sum rate subject to the power constraint at the users and relays. Using the dual-decomposition technique and the block-coordinate descent algorithm (BCDA), we then obtain a near-optimal solution for the proposed problems. The proposed methods significantly decrease the required feedback information, which reduce the overhead on the bandwidth and the cost. Furthermore, we investigate the impact of the noisy feedback channel on the system performance. Extensive simulation results are also presented, which indicate that DF outperforms AF in various conditions. It is also observed that by increasing the number of quantization regions, the average sum rate approaches the case in which full channel state information is available. [ABSTRACT FROM PUBLISHER]

In this paper, we propose a cross-layer resource-allocation scheme for orthogonal frequency-division multiple-access (OFDMA) systems with imperfect channel-state information (CSI). In our modeling, we consider two traffic types: 1) streaming traffic, which requires a maximum guaranteed average delay, and 2) elastic traffic with flexible rate requirements. We then consider queue-state information (QSI) and CSI in a cross-layer framework to maximize the total transmission rate of elastic users while the average delay constraint for streaming users and the maximum transmission power constraint are satisfied. We also consider the impact of imperfect CSI. An algorithm is then proposed based on the dual decomposition method to obtain the subcarrier assignment and power allocation for each user. Using simulations, we evaluate the impact of streaming traffic on the total achievable rate of elastic users for different values of the required outage probability. It is also shown by simulation that, by increasing the variance of CSI estimation, the total rate of elastic traffic is decreased. [ABSTRACT FROM AUTHOR]

In this paper, we propose a downlink multiple-input single-output (MISO) transmission scheme, which is assisted by an intelligent reflecting surface (IRS) consisting of a large number of passive reflecting elements. In the literature, it has been proved that nonorthogonal multiple access (NOMA) can achieve the same performance as computationally complex dirty paper coding, where the quasi-degradation condition is satisfied, conditioned on the users’ channels fall in the quasi-degradation region. However, in a conventional communication scenario, it is difficult to guarantee the quasi-degradation, because the channels are determined by the propagation environments and cannot be reconfigured. To overcome this difficulty, we focus on an IRS-assisted MISO NOMA system, where the wireless channels can be effectively tuned. We optimize the beamforming vectors and the IRS phase shift matrix for minimizing transmission power. Furthermore, we propose an improved quasi-degradation condition by using IRS, which can ensure that NOMA achieves the capacity region with high possibility. For a comparison, we study zero-forcing beamforming (ZFBF) as well, where the beamforming vectors and the IRS phase shift matrix are also jointly optimized. Comparing NOMA with ZFBF, it is shown that, with the same IRS phase shift matrix and the improved quasi-degradation condition, NOMA always outperforms ZFBF. At the same time, we identify the condition under which ZFBF outperforms NOMA, which motivates the proposed hybrid NOMA transmission. Simulation results show that the proposed IRS-assisted MISO system outperforms the MISO case without IRS, and the hybrid NOMA transmission scheme always achieves better performance than orthogonal multiple access. [ABSTRACT FROM AUTHOR]

In this paper we investigate downlink performance in a non-orthogonal multiple access (NOMA) based vehicular communication network. In contrast to the previous works wherein the vehicles are simply assumed to be located anywhere in the coverage area, we consider practical cases where vehicles are located on a system of roads. We then adopt a system model based on Poisson Line Cox Point (PLC) processes, where the road system is represented through a Poisson Line (PL) Process. Vehicles ordered according to their distances to their corresponding roadside units (RSUs) are then served by using power domain NOMA. Adopting analytical tools from the stochastic geometry, we then analyse the outage performance of the system. Numerical results corroborate our analysis and demonstrate how the system settings influence the considered NOMA based V2X network. [ABSTRACT FROM AUTHOR]

This work focuses on the beamforming design for downlink multiple-input single-output (MISO) nonorthogonal multiple access (NOMA) systems. The beamforming vectors are designed by solving a total transmission power minimization (TPM) problem with quality-of-service (QoS) constraints. In order to solve the proposed nonconvex optimization problem, we provide an efficient method using semidefinite relaxation. Moreover, for the first time, we characterize the optimal beamforming in a closed form with quasi-degradation condition, which is proven to achieve the same performance as dirty-paper coding (DPC). For the special case with two users, we further show that the original nonconvex TPM problem can be equivalently transferred into a convex optimization problem and easily solved via standard optimization tools. In addition, the optimal beamforming is also characterized in a closed form and we show that it achieves the same performance as the DPC. In the simulation, we show that our proposed optimal NOMA beamforming outperforms OMA schemes and can even achieve the same performance as DPC. Our solutions dramatically simplifies the problem of beamforming design in the downlink MISO NOMA systems and improve the system performance. [ABSTRACT FROM AUTHOR]