Considering a multicell environment, a distributed user selection scheme for uplink multiuser multiple-input multiple-output (MU-MIMO) system is proposed. In the proposed scheme, each user determines their own transmit beamforming vector based on the locally available channel state information (CSI), and informs the associated base station (BS) of the amount of inter-cell interference (ICI) affecting adjacent cells and the resulting beamforming vector. With the identical first-order statistic between the ICI from adjacent cells and the ICI that affects adjacent cells, a set of users can be selected, which the BS will simultaneously serve based on either the achievable sum rate maximization or proportional fairness achievement. Simulation results show that compared with prior distributed user-selection schemes, the proposed method provides a significant improvement in terms of achievable sum rates.

In coordinated multi-point (CoMP) transmission systems, coordinated base stations (BSs) are geographically separated and have their own oscillators, thereby causing multiple carrier frequency offsets (CFOs) at the receiver. Therefore, perfect synchronization cannot be obtained at the mobile station (MS), resulting in severe interference. To resolve this problem, this study proposes a novel transceiver structure with improved robustness toward interference. With the knowledge of CFO and channel frequency response, a closed-form solution is derived for the sub-optimal CFO compensation value to minimize the approximated upper bound of the inter-carrier interference (ICI) plus noise power for environments with large-scale fading. The results reveal that the sub-optimal CFO compensation value is a function of both the degree of large-scale fading and the value of CFOs. Simulation results demonstrate that the proposed method significantly outperforms the existing structures and exhibits improved performance in terms of bit error rate.

A low-complexity blind data detector is proposed in this paper for orthogonal frequency division multiplexing (OFDM) systems, where the generalized likelihood ratio test (GLRT) approach is adopted. Traditional GLRT data detector (GDD) can be viewed as a combinatorial optimization problem, which suffers from prohibitively high computational complexity. The proposed scheme reduces the search space by exploiting the phase ambiguity. In addition, the computational complexity is further reduced by properly decoupling the GDD into several sub-group GDDs (SGDD). Mathematical analysis is adopted to evaluate the complexity of the proposed scheme. Simulation experiments are conducted to verify the system performance.

Bandwidth efficiency is a critical concern in wireless communications. To fully utilize the available bandwidth, this paper adopts the superimposed training (ST) scheme in orthogonal frequency division multiplexing (OFDM) systems without using cyclic prefix (CP) and guard interval (GI). If the pilot pattern is fixed, it is shown that the performance of the channel estimation using the ST scheme is the same for both the proposed architecture, denoted as OFDM-ST, and the OFDM system with CP and ST scheme, denoted as CP-OFDM-ST. In addition, since the CP is not adopted in the proposed system, the performances of channel estimation and data detection are degraded because of the inter-symbol interference (ISI) and the inter-carrier interference (ICI). Therefore, a novel data detector, which includes ICI cancellation, is proposed to improve the channel estimation in OFDM-ST systems. The simulation results show that the proposed algorithm substantially enhances the systems performance.