Том 62, № 10 (2019)

Analytical consideration of lower bound (LB) analysis of the spectral efficiency (SE) of downlink transmission of Hyper MIMO (H-MIMO) system is important to obtain insights in the role of various factors that are involved. In this paper, we derived a mathematical expression for lower bound of the SE of an H-MIMO system with linear precoding techniques such as zero-forcing (ZF) and minimum mean square error (MMSE). The analysis of SE considers three joint user and antenna scheduling algorithms such as semi-orthogonal, random, and distance based user scheduling algorithms, whereas the antennas are selected based on maximum SNR with scheduled users. The channel between a user and a transmitter is assumed to have characteristics of small and large scale fading (SSF and LSF) with Rayleigh distributed block fading model. We investigate the effect of variation of transmit power, number of base station antennas M, and the radius of the cell on the SE. We simulate the downlink transmission of H-MIMO system and compare the simulation and analytical results. It is observed that the trends of variation of both results with the variation of different factors are similar, and the difference between the simulated and analytical LB-SE is approximately 1–1.5 bits. In this case the analytical LB is the smaller of the two.

A printed planar antenna having compact dimensions of 0.35×0.25λ, mm² and fed by a microstrip line for wideband applications is presented. The proposed antenna consists of a radiating patch, a new arc-shaped strip, microstrip feed line, and a rectangular stub loaded ground plane. Furthermore, the ground plane of the fundamental radiator is modified to improve the voltage standing wave ratio (VSWR) bandwidth. A rectangular stub is added inside the ground plane to provide the bandwidth to suit the modern automotive requirements. We have analyzed the proposed antenna in terms of VSWR, reflection loss, gain, radiation pattern, and the housing effect. The measured results indicate that the antenna achieves a wide useable fractional bandwidth ratio of 129% at VSWR ≤ 2, ranging from 4.8 to 21.7 GHz. A measured bandwidth of 119% at VSWR ≤ 1.5 (5.5–20.9 GHz) is obtained. Stable quasi-omnidirectional radiation patterns with an acceptable gain of 4.87 dBi are achieved.

The article presents the results of experimental studies of the TerraStar service, which implements autonomous real-time PPP (Precise Point Positioning) technology. The service provides high-speed orbital and clock data of GPS, GLONASS, GALILEO, BeiDou navigation satellites received from more than 100 global navigation satellite system (GNSS) ground stations. These data, together with the algorithms of the NovAtel dual-frequency (multi-system) navigation receiver with integrated TerraStar PPP technology provide solutions for high-precision (4–40 cm) position determination. The data is transmitted to the navigation receiver via radio channels of geostationary satellites.

The authors have evaluated the claimed positioning accuracy for Ukraine in difficult radio navigation conditions (urban canyon, the city of Kyiv and Kyiv region), which complements a number of existing studies on the accuracy of TerraStar service in different regions of the world.

An experimental technique is described that contains the procedures for initializing, recording, and storing data from a navigation receiver for subsequent comparison with a reference trajectory generated using GrafNav/GrafNet 8.70 software.

It was determined that the accuracy of estimating coordinates obtained in post-processing by PPP using GrafNav/GrafNet 8.70 software is comparable with the accuracy of coordinates calculated by the NovAtel OEM 719 receiver in real time using information from TerraStar.

It was experimentally confirmed that the positioning accuracy in the studied area corresponds to the accuracy declared by the TerraStar providers, which remains for 5 min even in the absence of TerraStar data.