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Accurate propagation characteristics are essential for future indoor millimeter-wave (mmWave) small cell network planning. This paper presents propagation measurements at 26 GHz and 38 GHz which are important candidate bands for fifth generation mmWave communication. Measurements are conducted in an indoor corridor, as well as a stairwell whose mmWave channel is seldom investigated before. In these measurements, an omnidirectional biconical antenna is used as transmitter and a steerable directional horn antenna is used as receiver. The directional and omnidirectional path loss exponents, shadow factors, cross-polarization discrimination ratios and root-mean-square delay spreads are analyzed for both line-of-sight and non-line-of-sight scenarios in both co-polarization and cross-polarization, and these characteristics are compared for different frequencies and environments. It is found obvious depolarization phenomenon in non-line-of-sight scenario for higher frequency. Compared to the corridor, the stairwell has larger path loss exponents and root-mean-square delay spreads, and the depolarization is also more evident in stairwell. The results in this paper are beneficial to building efficient and robust indoor mmWave communication systems.

In the millimeter-wave (mm-Wave) multiuser-multiple-input multiple-output (MU-MIMO) system, the interferences among different users generally degrade the system performance. In the meantime, orbital angular momentum (OAM) or radio vortex communication suffers significant fading due to the nature of divergence radiation. In this contribution, we utilize the divergence and propose an OAM-based independent analog beam selection (OAM-IABS) as well as a sub-optimal beam search solution to address all the above challenges. Simulation results demonstrate the superiority of the proposed scheme. [ABSTRACT FROM AUTHOR]

To determine the propagation characteristics in building for fifth-generation (5G) wireless communication, it is necessary to obtain the complex permittivities of the construction materials at millimeter wave (mmWave) band. Cloth materials are widely used in house, which have a great impact on the propagation of mmWave; however, their dielectric properties in mmWave band are rarely reported. In this communication, a new method for the estimation of the complex permittivities based on quantum-behaved particle swarm optimization (QPSO) algorithm and free-space measurement is proposed. Compared with classical particle swarm optimization (PSO) and chaos PSO (CPSO), QPSO is robust and efficient in searching the global optima. The complex permittivities of four cloth materials (linen, leatherette, polyester fiber, and latex mattress) are extracted from the measured transmission and reflection coefficients for perpendicular polarization over 40–50 GHz, and the accuracy is verified by comparing the calculated and measured reflection coefficients at other incident angles. The results presented in this communication are helpful for modeling the propagation of mmWave in indoor environment, and the proposed estimation method can serve as a good tool for the determination of dielectric properties of construction materials in wireless network planning. [ABSTRACT FROM AUTHOR]

Optical power splitter (OPS) as one of the basic elements in photonic integrated circuits (PIC) is widely used in many fields. The OPS with continuously adjustable power splitting ratio (PSR) can improve the flexibility of PIC and also simplify the PIC system. We propose and demonstrate an integrated OPS based on silicon-on-insulator. Our scheme combines several common structures such as 2 × 2 multimode interference coupler, waveguide grating and slot. The PSR of the OPS can be continuously adjustable by tuning the wavelength of the input signal or the voltages applied to the electrodes on the chip. The maximum tunable range of the PSR is from 28.2 dB to −1.7 dB when no voltages are applied to the electrodes and the wavelength of the input signal varies from 1542.62 nm to 1547.94 nm. And the maximum and minimum tunable ranges of the PSR are 35 dB and 0.4 dB, respectively, when the power consumption of the micro-heaters varies from 0 to 27 mW. So, our OPS can be both temperature-sensitive and temperature-insensitive. Our scheme has the advantages of compact structure and high flexibility, and it can be widely used in optical switching, signal channel division and power distribution. [ABSTRACT FROM AUTHOR]