Herein, we consider uplink multiuser massive multiple‐input multiple‐output systems when multiple users transmit information symbols to a base station (BS) by applying simple space‐time block coding ...

This study proposes implementation of two‐way amplify‐and‐forward relaying systems in practical environments where signals from two source nodes arrive at a relay with different propagation delays. The authors develop a self‐interference delay and channel estimation technique applicable for practical environments. Whereas receiver processing in conventional schemes is performed in the baud rate domain, in this work, oversampling (or Nyquist sampling) is introduced at the receiver to avoid any energy loss in the desired signal. They derive the proposed estimator in the oversampled domain on the basis of the least square criterion and also provide a design guide for the oversampling ratio and the application of a self‐interference canceller. They observe from the author's analysis and simulation results that an oversampling of 2 is sufficient, and it is not preferable to use a self‐interference canceller when L /( N· ISNR) is greater than 1, where the interference‐to‐signal‐plus‐noise ratio (ISNR) denotes the power ratio of the self‐interference to the desired signal plus noise, L is the channel length and N is the number of symbols in one time slot.

In this paper, we consider spatial beamforming for massive multiple-input multiple-output (MIMO) systems in frequency division duplexing (FDD). In order to reduce channel state information (CSI) feedback overhead of users, near-by users that have similar statistical channel correlation are put into a group and channel correlation matrix based precoding scheme is proposed. More specifically, we propose to employ two-stage precoder at a base station (BS): Outer precoder and inner precoder. The former is designed to minimize inter-group interference by considering the statistical channel correlation. The latter is designed to minimize intra-group interference by utilizing modified statistical channel correlation and instantaneous channel state information (ICSI). The inner precoder is composed of three steps: precoded pilot signal transmission phase at the BS, effective channel gain calculation and feedback stage at the mobile user, and data transmission stage at the BS.

We consider a hybrid combiner design for downlink massive multiple‐input multiple‐output systems when there is residual inter‐user interference and each user is equipped with a limited number of radi...

In this paper, we first analyze carrier-to-interference ratio performance of the space–frequency block coded orthogonal frequency-division multiplexing (SFBC-OFDM) system in the presence of phase noise (PHN) and residual carrier frequency offset (RCFO). From the analysis, we observe that conventional SFBC-OFDM systems suffer severely in the presence of PHN and RCFO. Therefore, we propose a new inter-carrier interference (ICI) self-cancellation method — namely, ISC — for SFBC-OFDM systems to reduce the ICI caused by PHN and RCFO. Through the simulation results, we show that the proposed scheme compensates the ICI caused by PHN and RCFO in Alamouti SFBC-OFDM systems and has a better performance than conventional schemes.