When using ultra-wideband signaling on massive multiple-input multiple-output (mMIMO) systems, the electromagnetic wave incurs an extra delay (across the array elements) comparable to or larger than the symbol duration, which translates into a shift in beam direction known as the beam squint effect. The beam squinting problem degrades the array gain and reduces the system capacity. This paper proposes a novel transceiver design based on lens antenna subarray and analog subband filters to compensate for the beam squinting effect. Specifically, the proposed design chunks the wideband signal from the phase shifters into groups of narrowband signals and controls their squints through an exhaustive search-based switching/precoding mechanism under the lenses. Furthermore, a simplified, thresholded search-based precoding algorithm is proposed, which demonstrates good performance while significantly minimizing complexity. The proposed system is analyzed in terms of beam gain, complexity, power consumption, and capacity. The numerical results demonstrate significant performance enhancement for the proposed system design as compared to the conventional mMIMO system with an uncompensated beam squinting problem.

Channel emulators are usually used to evaluate preliminary performances of the newly developed wireless algorithms in the laboratory without resorting to the on-site measurements which are generally complex and costly. In this study, a simple but effective channel emulator that features a benchtop-sized (small-sized) reverberation chamber (RVC), radio frequency (RF) cable, and power controller is proposed for emulating a Rician propagation environment with a flexibly controllable k-factor. The developed emulator has the ability to precisely introduce the Rician propagation effect (with the desired k-factor) to the input RF signal. The performance of the proposed emulator was evaluated through measurement and its accuracy was validated by conducting a Kolmogorov–Smirnov (KS) goodness-of-fit (GoF) test. The emulator is suitable for both algorithm/prototype testing and educational purpose in wireless laboratories.

Massive multiple-input multiple-output (mMIMO) systems implementing wideband signaling have been found to suffer from beam squinting problem. In multicarrier systems, beam squint causes spreading of the beam to multiple undesired directions, thereby degrading system capacity. This paper proposes user scheduling and precoding techniques that controls and exploit the beam squinting phenomenon to serve multiple users and improve the overall system capacity. The proposed techniques are based on the lens antenna subarray (LAS) mMIMO system. The proposed system design is explained and numerically evaluated in terms of beam gain and capacity with different number of users and RF chains. The simulation results exhibit significant performance enhancement in terms of beam gain and capacity, corroborating the idea of exploiting the beam squinting phenomenon to serve multiple spatially separated groups of users.

This work aims to address the timing synchronization issue which limits the applicability of coordinated multipoint schemes, specifically joint transmission, in practical wireless networks. Following a brief description of the issue itself, and its repercussions on the network performance, the various conditions/solutions that mitigate this problem are recapped. Following this, we provide the background of the proposed approach to be used for mitigating the timing synchronization issues, namely, common cyclic prefix (CP) technique. Then, a clustering algorithm is proposed aimed at balancing the cell load with timing synchronization as a constraint. In load balancing stage, the first priority is given to users with higher received power and lower number of base stations in the candidate set. The results obtained via simulations indicate that heterogeneous network (HetNet) deployments suffer from timing synchronization when smaller CP duration is used, and this performance degradation can be resolved quite effectively using the common CP configuration.