Throughput modeling in multiple-input multiple-output (MIMO) systems has attracted widespread attentions. Nevertheless, the current throughput model is confined to the case of fixed data streams (layers) and modulation and coding scheme (MCS). In the proposed study, we expand the conventional throughput model based on the transmit selection diversity and threshold translation mapping techniques to enable its use in systems, where the MCS and layers are adaptively modified depending on channel quality. Excellent agreement between the simulation and measurement results confirms the effectiveness and accuracy of the suggested throughput model.

The exploration of Internet-of-things has led to widespread of short-range multiple-input multiple-output (MIMO) communications. However, traditional throughput models, limited by the far-field propagation assumptions, often fail to accurately evaluate the spatial multiplexing capability and throughput performance in short-range line-of-sight (LOS) scenarios. Against this backdrop, this letter reveals the limitations of the conventional plane wave model (PWM) based throughput model from the perspective of effective degree of freedom (EDOF) and develops a MIMO throughput model for short-range LOS scenarios using a spherical wave model (SWM). The relationship between EDOF and throughput is analyzed and discussed. Our results show that EDOF can effectively indicate throughput variations across different transceiver layouts in short-range LOS scenarios. Throughput measurements of MIMO devices are conducted to show the superiority of the proposed SWM-based throughput model to the traditional one.

Part II investigates phase modulation as a low-complexity alternative to conventional phase shifters in pattern-reconfigurable antenna arrays. In the proposed architecture, phase formation originates from the direct reconfiguration of the driven radiation current and the induced parasitic current within each radiating element. This is achieved through a dual-phase control mechanism that independently tunes the intrinsic and deflection phases using separately biased PIN diodes integrated into the feeding branches and parasitic comb structures. The resulting discrete phase states provide a phase tuning range of up to 116° and enable subarray-level beamforming without continuous element-wise phase synthesis. Based on this concept, a 6-element discretized subarray is developed as the fundamental beamforming unit, offering three fixed beam states with simplified bias control. By adopting subarray-level beam-state selection, an 8×24 sparse dual-polarized array is constructed, enabling wide-angle two-dimensional scanning (±60° azimuth, ±10° elevation) while significantly reducing the number of RF chains. Despite the reduced channel count, the proposed architecture maintains comparable channel capacity, as validated through simulations and measurements, demonstrating its practicality for large-scale base station antenna arrays.

In multipath environments, multiple-input multiple-output (MIMO) terminals typically suffer from non-zero correlations due to limited handset space and power imbalances due to different antenna efficiencies or partial hand blockage. These antenna–channel impairments can lead to significant throughput performance degradation of MIMO terminals. The multiplexing efficiency was proposed to quantitatively assess this performance degradation. Previous work only derived the analytical expression of the throughput-based multiplexing efficiency of two-port MIMO antennas for user equipment (UE). However, the fifth-generation (5G) UE dictates four or more antennas. In this paper, we extend the multiplexing efficiency metric to high-order MIMO UEs. Both correlation-based channel models and geometry-based stochastic channel models were used for validation. Besides dipole antennas, two representative terminal antennas were also employed for simulation verifications in this work.

The plane wave synthesis (PWS) method is conventionally considered superior to the spherical vector wave (SVW) technique for two-dimensional (2-D) multiple-input multiple-output over-the-air (OTA) testing. This letter consummates this perception by identifying that the degradation of the conventional SVW stems primarily from sensitivity to the mode truncation number. To address this, we propose a robust enhanced SVW scheme formulated directly in the electromagnetic field domain. By exploiting the natural low-pass filtering property of the spherical sampling matrix, the proposed method inherently avoids the overfitting issue of high-order modes, thereby eliminating the truncation sensitivity. Our simulation results demonstrate that the proposed scheme ensures numerical stability and consistently outperforms the classic PWS in terms of reconstruction accuracy, rotational invariance, and test zone size. This work effectively revitalizes the SVW technique for high-precision 2-D OTA testing.