A Multi-Beam NOMA Framework for Hybrid mmWave Systems

et al. 2018

IEEE Trans. Commun.

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In this paper, we investigate the system performance of a multi-cell multi-user (MU) hybrid millimeter wave (mmWave) communications in a multiple-input multiple-output (MIMO) network. Due to the reuse of pilot symbols among different cells, the performance of channel estimation is expected to be degraded by pilot contamination, which is considered as a fundamental performance bottleneck of conventional multicell MU massive MIMO networks. To analyze the impact of pilot contamination to the system performance, we first derive the closed-form approximation of the normalized mean squared error (MSE) of the channel estimation algorithm proposed in [2] over Rician fading channels. Our analytical and simulation results show that the channel estimation error incurred by the impact of pilot contamination and noise vanishes asymptotically with an increasing number of antennas equipped at each radio frequency (RF) chain at the desired BS. Furthermore, by adopting zero-forcing (ZF) precoding in each cell for downlink transmission, we derive a tight closed-form approximation of the average achievable rate per user. Our results unveil that the intra-cell interference and inter-cell interference caused by pilot contamination over Rician fading channels can be mitigated effectively by simply increasing the number of antennas equipped at the desired BS.

Section: Introductionmentioning

confidence: 99%

Multi-Cell Hybrid Millimeter Wave Systems: Pilot Contamination and Interference Mitigation

Zhao

et al. 2018

IEEE Trans. Commun.

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“…We consider an mmWave system with carrier frequency at 28 GHz. There are one LOS path and L = 10 NLOS paths for the channel model in (1) and the path loss models for LOS and NLOS paths follow Table I in [37]. A single hexagonal cell with a BS located at the cell center with a cell radius of 200 m is considered.…”

Section: Simulation Resultsmentioning

confidence: 99%

Multi-Beam NOMA for Hybrid mmWave Systems

Zhao

Guo

et al. 2019

IEEE Trans. Commun.

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137

In this paper, we propose a multi-beam non-orthogonal multiple access (NOMA) scheme for hybrid millimeter wave (mmWave) systems and study its resource allocation. A beam splitting technique is designed to generate multiple analog beams to serve multiple users for NOMA transmission. Compared to conventional mmWave orthogonal multiple access (mmWave-OMA) schemes, the proposed scheme can serve more than one user on each radio frequency (RF) chain. Besides, in contrast to the recently proposed single-beam mmWave-NOMA scheme which can only serve multiple NOMA users within the same beam, the proposed scheme can perform NOMA transmission for the users with an arbitrary angle-of-departure (AOD) distribution. This provides a higher flexibility for applying NOMA in mmWave communications and thus can efficiently exploit the potential multi-user diversity. Then, we design a suboptimal two-stage resource allocation for maximizing the system sum-rate. In the first stage, assuming that only analog beamforming is available, a user grouping and antenna allocation algorithm is proposed to maximize the conditional system sum-rate based on the coalition formation game theory. In the second stage, with the zero-forcing (ZF) digital precoder, a suboptimal solution is devised to solve a non-convex power allocation optimization problem for the maximization of the system sum-rate which takes into account the quality of service (QoS) constraint. Simulation results show that our designed resource allocation can achieve a close-to-optimal performance in each stage. In addition, we demonstrate that the proposed multi-beam mmWave-NOMA scheme offers a higher spectral efficiency than that of the single-beam mmWave-NOMA and the mmWave-OMA schemes.

“…,∀k,i,n, (21) where Θ k,i,n = q 1 + N (ε n,k,i + θ n + ϕ n ). The optimal power allocation in (21) is the classic multiuser water-filling solution.…”

Section: Solution Of Layer 1 (Power Allocation and User Scheduling)mentioning

confidence: 99%

“…Note that c[n] in constraint (33) is non-convex. To design a tractable resource allocation, the successive convex approximation (SCA) is applied [5], [7], [21]. In particular, for a given feasible solution t (j Algo2 ) [n] in the j Algo2 -th main loop iteration for sub-problem 2, since c[n] ≥c (j Algo2 ) [n], we obtain a lower bound of equation (33), which is given by…”

Section: B Sub-problem 2: Optimizing Uav's Trajectory and Flight Velmentioning

confidence: 99%

Energy-Efficient Resource Allocation for Secure UAV Communication Systems

Cai

2019 IEEE Wireless Communications and Networking Conference (WCNC)

et al. 2019

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In this paper, we study the resource allocation and trajectory design for energy-efficient secure unmanned aerial vehicle (UAV) communication systems where a UAV base station serves multiple legitimate ground users in the existence of a potential eavesdropper. We aim to maximize the energy efficiency of the UAV by jointly optimizing its transmit power, user scheduling, trajectory, and velocity. The design is formulated as a nonconvex optimization problem taking into account the maximum tolerable signal-to-noise ratio (SNR) leakage, the minimum data rate requirement of each user, and the location uncertainty of the eavesdropper. An iterative algorithm is proposed to obtain an efficient suboptimal solution. Simulation results demonstrate that the proposed algorithm can achieve a significant improvement of the system energy efficiency while satisfying communication security constraint, compared to some simple scheme adopting straight flight trajectory with a constant speed.=R(U * ) − q * 2 P Eq (V * , Υ * ) = 0,