Traffic offloading to the millimeter-wave hotspots is an efficient way to increase the throughput and spectral efficiency of existing LTE networks. Such approach can be considered as first step towards 5G systems, but before the millimeter-wave overlay realize its full potential, several important problems should be solved. Firstly, the millimeter-wave coverage should be increased up to several hundred meters - and this is possible not only with implementation of high-gain steerable antennas, and usage of special beamforming algorithms. Secondly, the MU-MIMO should be introduced in the mmWave standards, which lead to significant increase of simultaneously served stations and therefore, substantial increase probability of collisions between them. In this paper we will show that both mentioned problems may be resolved with the proposed asymmetric links beamforming procedure. This enhanced beamforming was initially submitted and accepted as part of upcoming next-generation millimeter-wave standard: IEEE 802.11ay.

In this paper we introduce the performance evaluation of the isolated millimeter-wave (mmWave) small cell. The potential performance of the mmWave small cells is evaluated on the base of PHY layer technique with parameters similar to IEEE 802.11ad standard. Two important practical tasks are addressed in this paper: the efficiency of mmWave spectrum utilization and the small cell optimal coverage. Two approaches for spectrum utilization are considered: frequency reuse-1 (each cell sector operates in three channels) and frequency reuse-3 (each of three cell sectors operates in only one channel). We start from the comparison of these scenarios spectral efficiency. At the next step the interference mitigation techniques are applied in order to improve the system performance for both scenarios. Also we discuss the mmWave small cell coverage and its limits due to the regulator requirements. The impact of small cell radius on MU-MIMO mode performance is addressed and evaluated. Finally, the discussion and recommendations on the small cell size, frequency reuse scenario and interference mitigation techniques are provided.

In this paper we provide detailed system level performance analysis of MU-MIMO mode in the millimeter wave (mmWave) small cells (Wi-Fi hotspots) environment. Traditional way of MIMO implementation assumes a single RF chain per antenna element, with all spatial processing done in the baseband. To overcome high pathloss in the mmWave bands, the large-aperture, very high gain arrays with a large number of elements (several hundreds) are required. Therefore we introduce partially adaptive arrays with reduced number of degrees of freedom which are implemented based on the modular antenna arrays (MAA) architecture. The scalable practical design of MAA allows creation of large-aperture, high-power antenna arrays with reduced number of RF chains at cost of decreasing the adaptability. Employing recently proposed quasi-deterministic (Q-D) model for millimeter-wave channels, it was shown that partially adaptive MAA have very small degradation in comparison with ideal fully adaptive array (FAA) in a realistic scenarios. It was shown that application of MU-MIMO mode in a mmWave small cells allows achieving up to 15-30 Gbps total throughput per cell in a multipath environment (university campus scenario) with practical antenna array design.

This paper presents a detailed analysis of the impact of power amplifier (PA) non-linearity on the performance of single carrier (SC) and OFDM systems in 60 GHz spectrum. The efficiency of the considered systems was analyzed by estimating values of the power amplifier output backoff needed to meet the requirements on the transmit spectrum mask (TSM) compliance and error vector magnitude (EVM). Different models of the PA including an experimentally measured model for the 60 GHz PA were considered. It was estimated that for many types of modulations and PA models, SC system can have up to 1.5 dB higher output power than OFDM system. However, for the experimental PA model accounting for amplitude modulation-phase modulation distortion in addition to amplitude modulation amplitude modulation distortion, the difference between the OFDM and SC output power levels was minimal, and OFDM even had approximately 1 dB better performance than SC for the BPSK modulation. A potential improvement in the transmit power due to application of digital predistortion techniques was estimated for both systems to be in the range from 1.5 to 3.4 dB.

This paper presents the results of an experimental investigation of 60 GHz wireless local area network (WLAN) systems in an office environment. The measurement setup with highly directional mechanically steerable antennas and 800 MHz bandwidth was developed and experiments were performed for conference room and cubicle environments. Measurement results demonstrate that the 60 GHz propagation channel is quasioptical in nature and received signal power is obtained through line of sight (LOS) and reflected signal paths of the first and second orders. The 60 GHz WLAN system prototype using steerable directional antennas with 18 dB gain was able to achieve about 30 dB baseband SNR for LOS transmission, about 15-20 dB for communications through the first-order reflected path, and 2-6 dB SNR when using second-order reflection for the office environments. The intra cluster statistical parameters of the propagation channel were evaluated and a statistical model for reflected clusters is proposed. Experimental results demonstrating strong polarization impact on the characteristics of the propagation channel are presented. Cross-polarization discrimination (XPD) of the propagation channel was estimated as approximately 20 dB for LOS transmission and 10-20 dB for NLOS reflected paths.

This paper presents the results of the spatial reuse mode performance analysis for millimeter-wave (mmWave) WPAN systems with steerable high-directional antennas. The practical approach to the spatial reuse problem solution is proposed and two spatial scheduling algorithms for spatial reuse mode implementation are presented. The system level simulations are used to estimate the performance of the proposed algorithms. It is demonstrated that the introduction of the spatial reuse mode for the indoor mmWave WPAN system with 8 parallel communication links will increase the overall mmWave WPAN system throughput in 3-5 times in comparison with conventional time division mode.

The novel CORDIC-based architecture of the triangular systolic array for QRD of large size complex matrices is presented. The proposed architecture relies on QRD using a three angle complex rotation approach that provides significant reduction of latency (systolic operation time) and makes the QRD in such a way that the upper triangular matrix R has only real diagonal elements.

In this letter, the generalized likelihood ratio test (GLRT) is used for the detection of multidimensional Gaussian complex signals with unknown spatial covariance matrix on a background of additive Gaussian complex noise of a unknown power is solved. The exact analytical expressions for test-statistical moments were found for any numbers of observations. The expansion in a series of probability density functions of a resolving statistic for orthogonal Jacobi polynomials were obtained by method of moments. The accuracy of the GLRT-statistic cumulative distribution function approximation and the accuracy of threshold calculations for the given false alarm probability for various numbers of approximating series terms were checked by simulation. The results are correct for any number of samples.