A design of an ultra-wideband eight-port multiple-input multiple-output (MIMO) antenna array in a smartphone with an open-slot metal frame for fifth-generation (5G) communications is presented. Each element is fed by a microstrip line with a tuning stub, consisting of a U-slot on the ground plane and an open slot on the metal frame. Each slot element on the ground only occupies an area of 15 ×3 mm. The antenna array can operate in 3.3-6 GHz (S 11 < −6 dB) that is ultra-wide bandwidth for the future 5G communications. The antenna array is manufactured and measured. Measured antenna isolation is higher than 11 dB without any decoupling structures applied. Moreover, measured radiation patterns, antenna efficiencies, and envelop correlation coefficients are also given in this paper. High agreement between the measured and simulated results is obtained, which means that the proposed antenna is promising in engineering application. INDEX TERMS 5G communication, metal frame, MIMO antenna, smartphone, ultra-wideband.

Nitrogen-doped CDs (N-CDs) were firstly prepared by using pear juice as the carbon source and ethanediamine as a nitrogen doping precursor with a microwave assisted pyrolysis technique. Based on the fluorescence recovery induced by competitive adsorption and desorption, a label-free “turn on” fluorescence assay with high sensitivity and selectivity was proposed for the analysis of CA125.

Tone injection (TI) can effectively reduce the peakto-average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signals without incurring data rate loss and extra side information. However, the optimal TI scheme requires an exhaustive search over all combinations of the possible perturbations of the expanded constellation over all perturbed subcarriers, which is not suitable for practical applications. To reduce the complexity while still achieving good PAPR performance, a low-complexity TI scheme based on distortion signals is proposed in this paper. Motivated by the goal of mitigating the distortions when OFDM signals pass high power amplifiers, we intuitively get the perturbation information for OFDM signals directly from the distortion signals. By exploiting the distribution of the perturbation vectors depending on the distortion signals, we design a search range limited extended constellation. Then, based on the statistical information of perturbed subcarriers, the number of the subcarriers to be perturbed is restricted. Moreover, to further reduce the complexity, we choose a proper subcarrier perturbation sequence from candidate subcarrier sets according to the mutual information between the peak sample and the distortion signals. With the selected subcarrier perturbation sequence, the original problem is decomposed into a sequential search problem, which provides a dramatic complexity reduction. Simulation results demonstrate that the proposed scheme can achieve significant complexity savings while maintaining a good PAPR performance.

Massive multiple input multiple output (MIMO) is one of the promising technologies to address the growing capacity requirement in fifth-generation cellular systems. However, the massive MIMO deployed at base stations (BSs) or relay stations (RSs) brings new challenges on channel state information (CSI) feedback because of its large-scale complex channel matrix. In this paper, we propose a hybrid limited feedback with selective eigenvalue information (HLFSEI), which adopts the individual quantized feedback and the codebook-based feedback jointly. In HLFSEI, we feed back only selective eigenvalue elements for power allocation by individual quantized feedback and the precoding matrix by codebook-based feedback. Furthermore, we study the optimal feedback bit allocation of the aforementioned two feedback methods to minimize the throughput loss with the feedback-link capacity constraint. Specifically, the feedback bits are allocated according to the properties of the throughput loss in high-and low-signal-to-noise regimes. Both the BS-RS communications and the BS/RS-user-equipment communications in cellular systems are taken into consideration. Finally, we evaluate the performance of the proposed HLFSEI strategy by simulation and show its performance gain compared with conventional feedback strategies.Index Terms-Fifth-generation cellular systems, limited feedback, massive multiple input multiple output (MIMO), power allocation. Manuscript