A downlink beamforming assisted by locally positioned communication devices

Recently, multiple cell types with overlapping coverage have been deployed simultaneously to increase cellular network capacity. Cross‐tier interference is one of the key technical challenges in the use of this method. A simple and practical beamforming scheme assisted by locally positioned communication devices for the downlink of a multi‐cell wireless hierarchical cell structure system is proposed in this paper to maximize the capacity of the embedded small cell and simultaneously ensure minimal impact on the performance of existing macrocells. The locally positioned communication devices can be implemented with low complexity and at low cost and can continuously provide helpful and accurate information to base stations for the proper configuration of geographical cell coverage, allowing neighboring cells to cooperate effectively with each other. Simulation results verify that the proposed scheme can provide a significant gain over conventional systems not using the proposed algorithm. Copyright © 2013 John Wiley & Sons, Ltd.     

Novel Detection Scheme for LSAS Using Power Allocation in Multi User Scenario with LTE-A and MMB Channels

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.

     

Halogen plasma erosion resistance of rare earth oxide films deposited on plasma sprayed alumina coating by aerosol deposition

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.     

LiNi<Subscript>0.4</Subscript>Co<Subscript>0.3</Subscript>Mn<Subscript>0.3</Subscript>O<Subscript>2</Subscript> thin film electrode by aerosol deposition

LiNi_0.4Co_0.3Mn_0.3O₂ thin film electrodes are fabricated from LiNi_0.4Co_0.3Mn_0.3O₂ 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 LiNi_0.4Co_0.3Mn_0.3O₂ thin film is composed of fine grains maintaining the crystal structure of the LiNi_0.4Co_0.3Mn_0.3O₂ raw powder. In the cyclic voltammogram, the LiNi_0.4Co_0.3Mn_0.3O₂ 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.     

Design and Analysis of an Interference Cancellation Algorithm for AF,DF and DMF Relay Protocol in Multiuser MIMO Scenario Based on the LTE-Advanced System

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.     

Performance Enhancement of Hybrid TDOA/AOA Using Multipath Delay Estimation

Wireless Personal Communications - Wireless solar blind ultraviolet (UV) scattering communication is a new type of atmosphere optics communication technology with the important and potential...     

3D Localization for Launch Vehicle Using Virtual TOA and AOA of Ground Stations

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...     

Intercell Interference Coordination Using Threshold-Based Region Decisions

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.     

Effect of plasma oxynitriding temperature on wear and corrosion resistance of the AISI 4140 steel

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-Fe_2–3N 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.     

Adaptive Channel Estimation Scheme Based on LTE Uplink in V2V Environments

Wireless Personal Communications - Vehicle communication can facilitate efficient coordination among vehicles on the road and enable future vehicular applications such as vehicle safety...