Xia Chen

Comparison of Antenna Arrays for MIMO System in High Speed Mobile Scenarios

The impact of antenna array geometry on MIMO (Multiple-input Multiple-output) system in high speed railway scenario is investigated in this paper. The capacity of different antenna arrays and the effect of ULA (uniform linear array) azimuthal orientation on capacity are studied with a double-directional channel model including antenna effects and Doppler shift.

Waveform Design for 5G Networks: Analysis and Comparison

The next-generation cellular network is to provide a large variety of services for different kinds of terminals, from traditional voice and data services over mobile phones to small packet transmission over massive machine-type terminals. Although orthogonal-subcarrier-based waveforms are widely used nowadays in many practical systems, they can hardly meet the requirements in the coming 5G networks. Therefore, more flexible waveforms have been proposed to address the unprecedented challenges. In this paper, we will provide comprehensive analysis and comparison for typical waveforms. To offer an insightful analysis, we will not only introduce the basic principles of the waveforms, but also reveal the underlying characteristics. Moreover, a comprehensive comparison in terms of different performance metrics will also be presented in thispaper, which provides an overall understanding of the new waveforms.

Fade Duration Distribution and Minimum Duration Outage in Weibull Fading Channels

During almost fifty years, fade duration distribution (FDD) of random signals has been an open research topic. However, for Weibull fading channels, closed form solutions are still unknown. Minimum duration outage (MDO) definition is decisive to complement the traditional outage concept and it has been reported, up to now, only for Log-normal shadowing, Rayleigh fading and Nakagami fading. In this paper, FDD and MDO in Weibull channels are studied. By utilizing the relation between Weibull distribution and Rayleigh distribution, analytical results are derived for FDD as well as the performance measures under MDO principle such as frequency of outage, average duration of outage, and probability of outage. Numerical results are presented to illustrate the analytical results.

Delay-Aware Dynamic Resource Allocation in High-Speed Railway Networks

With the rapid development of high-speed railway (HSR) system, there is an increasing demand on providing high quality multimedia services for HSR passengers. In this paper, we investigate the downlink resource allocation problem for multimedia services delivery in HSR orthogonal frequency division multiple access (OFDMA) system. Taking the statistical delay-QoS requirements into account, we formulate the problem as a mixed integer non-linear programming (MINLP), which aims at maximizing the system throughput over a trip of the train. With the help of integer constraint relaxation, this problem can be simplified into a convex optimization problem. To solve it, a stochastic approximation based dynamic resource allocation algorithm is developed. Finally, the numerical results are presented to show the effectiveness of the proposed resource allocation algorithm.