A True-Time-Delay Array Architecture for Wideband Multi-Beam Tracking

The true-time delay(TTD)units are critical for solving beam squint and frequency selective fading inWideband Large-Scale Antenna Systems(LSASs).In this work,we propose a TTD array architecture for wideband multi-beam tracking that eliminates the beam squint phenomenon and filters out interference signals by applying a spatial filter and time delay estimations(TDEs).The paper presents a novel approach to spatial filter design by introducing a transformation matrix that can optimize the beam response in a specific direction and at a specific frequency.Using the variable fractional delay(VFD)filters,we propose a TDE algorithm with a Newton-Raphson iteration update process that corrects the arrival time delay difference between sensors.Simulations and examples have demonstrated that the proposed architecture can achieve beam tracking within 10 ms at the low signalto-noise ratio(SNR)and demodulation loss is less than 0.5 dB in wideband multi-beam scenarios.

Diversity–Multiplexing Tradeoff and Outage Performance for 2×2 Dual-Polarized Uncorrelated Rice MIMO Channels

In this paper, diversity-multiplexing tradeoff (DMT) curve for 2×2 Dual-Polarized uncorrelated Rice MIMO channels is studied. Exact expressions for statistic information of mutual information exponent are derived. Impacts of channel parameters such as signal to noise ratio (SNR), k-factor and cross polarization discrimination (XPD) on mutual information exponent are analyzed. Compared to conventional single-polarized (SP) Rice MIMO systems, a qualitatively different behavior is observed for DP Rice systems. The work in this paper, allows identifying quantitatively for which channels (k-factor) and SNR levels the use of dual polarization becomes beneficial. Gamma or lognormal distribution are used to describe mutual information component, and a theoretical formulation for finite-SNR DMT curve in 2×2 DP uncorrelated Rice channels is presented for the first time, which is valid in low and medium SNRs when multiplexing gain is larger than 0.75.

Signal Detection Based on Walsh Transform for Spectrum Sensing

Spectrum sensing is a key technology to improve spectrum efficiency. In this paper, we propose a novel signal detection method based on Walsh transform for spectrum sensing. The main idea behind is that the received signal is transformed into another domain by Walsh transform and the test statistic is obtained by exploiting the feature of the useful signal in the new domain. The new method can perform well at low signal-to-noise rate (SNR). Simulation results show that the proposed method has better performance than the spectral feature detection based on power spectrum.

Multiuser Receiver Scheme with SIC for PUCCH in High Speed Train Environment

A multiuser receiver scheme with successive interference cancellation (SIC) is proposed to suppress multiuser interference for physical uplink control channel (PUCCH) in high speed train (HST) environment. In the proposed algorithm, each user’s signal is detected iteratively in a descending order according to the signal strength at eNB. During each iteration, the strongest signal of all users’ is detected and regenerated, and then is subtracted from the composite signal before decoding the next user. Simulation results show that the proposed scheme obtains remarkable gains, e.g. 2 dB for PUCCH format 2 with 3 users in HST scenario 1. The improvement is more pronounced in the case of increasing number of users, e.g. 3.3 dB with 6 users.