Massive MIMO (also known as the “Large-Scale Antenna System”) enables a significant reduction of latency on the air interface with the use of a large excess of service-antennas over active terminals and time division duplex operation. For large-scale MIMO, several technical issues need to be addressed (e.g., pilot pattern design and low-antenna power transmission design) and theoretically addressed (e.g., channel estimation and power allocation schemes). In this paper, we analyze the ergodic spectral efficiency upper bound of a large-scale MIMO, and the key technologies including channel uplink detection. We also present new approaches for detection and power allocation. Assuming arbitrary antenna correlation and user distributions, we derive approximations of achievable rates with linear detection techniques, namely zero forcing, maximum ratio combining, minimum mean squared error (MMSE) and eigen-value decomposition power allocation (EVD-PA). While the approximations are tight in the large system limit with an infinitely large number of antennas and user terminals, they also match our simulations for realistic system dimensions. We further show that a simple EVD-PA detection scheme can achieve the same performance as MMSE with one order of magnitude fewer antennas in both uncorrelated and correlated fading channels. Our simulation results show that our proposal is a better detection scheme than the conventional scheme for LSAS. Also, we used two channel environment channels for further analysis of our algorithm: the Long Term Evolution Advanced channel and the Millimeter wave Mobile Broadband channel.
Dense yttria, erbia and dysprosia films with thicknesses of 44.8 ± 1.7, 51.6 ± 0.9 and 36.8 ± 3.1 μm, respectively, were deposited on plasma sprayed alumina coating by aerosol deposition (AD). The rare earth oxide films remarkably enhanced the erosion resistance of the plasma sprayed alumina coating upon exposure to the halogen gas plasma. The enhanced plasma erosion resistances were related to their low surface porosity as well as the low vapor pressures of the rare earth fluorides and chlorides compared with those of corresponding aluminum halogenides. Electrical breakdown voltages of the samples with yttria, erbia and dysprosia films on the plasma sprayed alumina coating were 5.5, 6.2 and 5.3 kV, respectively, at room temperature and 4.0, 4.2 and 3.9 kV, respectively, at 573 K. The breakdown voltages at RT and 573 K were more than double that of the plasma sprayed alumina coating without the AD films. 相似文献
LiNi0.4Co0.3Mn0.3O2 thin film electrodes are fabricated from LiNi0.4Co0.3Mn0.3O2 raw powder at room temperature without pretreatments using aerosol deposition that is much faster and easier than conventional
methods such as vaporization, pulsed laser deposition, and sputtering. The LiNi0.4Co0.3Mn0.3O2 thin film is composed of fine grains maintaining the crystal structure of the LiNi0.4Co0.3Mn0.3O2 raw powder. In the cyclic voltammogram, the LiNi0.4Co0.3Mn0.3O2 thin film electrode shows a 3.9-V anodic peak and a 3.6-V cathodic peak. The initial discharge capacity is 44.6 μAh/cm2, and reversible behavior is observed in charge-discharge profiles. Based on the results, the aerosol deposition method is
believed to be a potential candidate for the fabrication of thin film electrodes. 相似文献
The analysis and design of relay protocols is a hot issue in 3GPP Long Term Evolution—Advanced. In this paper, we discuss interference cancellation in a multiuser MIMO environment using Amplify-and-Forward (AF), Decode-and-Forward (DF) and De-Modulate-and-Forward (DMF) as relay protocols, and using Thomilson Harashima Precoding and Dirty Paper Coding as precoding techniques, with Zero-Forcing, Minimum Mean Square Error, Successive Interference Cancellation and Ordered Successive Interference Cancellation detection techniques. By using a combination of classical precoding schemes and detection techniques with weighted matrix, we propose a new interference cancellation technique that is capable of cancelling interference. The interference cancellation is managed by AF, DF and DMF relay node protocols and the interference free codeword is transmitted to the selected User Equipment. The proposed algorithm when used with DMF protocol shows best performance, compared to the conventional system or the no-relay system case, it gives best performance. The observation results shows that DMF protocol gives the best results for BER and Throughput performance in a high interference environment. 相似文献
Wireless Personal Communications - Wireless solar blind ultraviolet (UV) scattering communication is a new type of atmosphere optics communication technology with the important and potential... 相似文献
Wireless Personal Communications - Generally, a ground telemetry station for a launch vehicle (LV) includes a tracking function only; therefore, position measurements for LV depend on received... 相似文献
IMT-Advanced mobile communication systems make it possible for any devices to access high-speed networks anytime and anywhere.
To meet the needs of IMT-Advanced systems, cellular systems must solve the problem of intercell interference caused by frequency
reuse. Intercell interference problems become severe when orthogonal frequency division multiplexing (OFDM) transmission,
which is a key technology for 4G communication systems, is used in a cellular system. In this paper, a zone-based intercell
interference coordination (ICIC) scheme with high flexibility and low cost is proposed, and its performance is evaluated through
multicell system-level simulations carried out according to the simplified 3GPP (3rd Generation Partnership Project) Long
Term Evolution (LTE) system parameters. In the proposed algorithm, each cell is divided into several regions based on threshold
values. Each region reuses frequencies in different ways, and the regions have different maximum transmit (TX) powers according
to the interference environment. Even though the proposed scheme can be implemented with low complexity by using only the
existing user equipment (UE) measurement, simulation results have confirmed that it provides significant improvements in geometry
distribution. 相似文献
This work presents the effect of oxynitriding process at different temperature on the corrosion resistance and wear behavior of the quenching-and-tempering-treated AISI 4140 steel. The AISI 4140 was plasma nitrided at 500°C. Subsequently, the plasma oxynitriding was performed on the nitrided AISI 4140 at different temperatures under H2O atmosphere. Microstructure and phases of the plasma-oxynitrided samples are investigated, indicating that phase formation of the oxide layer is strongly dependent on processing temperature during plasma oxynitriding: Formation of Fe3O4 is preferred over Fe2O3 at lower processing temperature. Also, it is believed that ε-Fe2–3N phase formed by nitriding process plays an important role to promote the formation of Fe3O4 phase during plasma oxynitriding. In order to investigate the mechanical, wear, and corrosion properties of the plasma-oxynitrided samples, Vickers hardness, friction coefficient, and potentiodynamic curves are evaluated, respectively. Compared to a plasma-nitrided sample, the Vickers hardness of the plasma-oxynitrided sample at optimal processing temperature shows a slight decrease of the hardness, but, improved wear and corrosion resistances were observed. It is suggested that wear and corrosion resistance of the oxynitrided sample is strongly dependent on the volume fraction of Fe3O4 phase in the oxide layer. 相似文献
SiZer (SIgnificant ZERo crossing of the derivatives) and SiNos (SIgnificant NOn-Stationarities) are scale-space based visualization tools for statistical inference. They are used to discover meaningful structure in data through exploratory analysis involving statistical smoothing techniques. Wavelet methods have been successfully used to analyze various types of time series. In this paper, we propose a new time series analysis approach, which combines the wavelet analysis with the visualization tools SiZer and SiNos. We use certain functions of wavelet coefficients at different scales as inputs, and then apply SiZer or SiNos to highlight potential non-stationarities. We show that this new methodology can reveal hidden local non-stationary behavior of time series, that are otherwise difficult to detect. 相似文献