User Effects in Beam-Space MIMO

Abstract

The performance and design of the novel single-RF-chain beam-space MIMO antenna concept is evaluated for the first time in the presence of the user. First, the variations of different performance parameters are evaluated when placing a beam-space MIMO antenna in close proximity to the user body in several typical operating scenarios. In addition to the typical degradation of conventional antennas in terms of radiation efficiency and impedance matching, it is observed that the user body corrupts the power balance and the orthogonality of the beam-space MIMO basis. However, capacity analyses show that throughput reduction mainly stems from the absorption in user body tissues rather than from the power imbalance and the correlation of the basis. These results confirm that the beam-space MIMO concept, so far only demonstrated in the absence of external perturbation, still performs very well in typical human body interaction scenarios.Comment: 4 pages, 7 figures, 2 table

Near-Field Perturbation Effect on Constellation Error in Beam-Space MIMO

“…The basis correlation is also increased to −11.9 dB in the worst case, which is still sufficiently good for MIMO operation. As concluded in [5], the impairments of the power imbalance ratio and the basis decorrelation show a less pronounced degradation effect on the multiplexing performance of the beam-space MIMO systems.…”

“…It has been shown that although the near-field interaction with transmit antennas in beam-space MIMO deteriorates the orthonormality of the basis patterns, throughput reduction is still mainly caused by the power absorption in user body tissues rather than by the distortion of the basis characteristics. While the conclusion in [5] confirms the suitability of using beam-space MIMO in near-field interaction scenarios under BPSK modulation, it cannot immediately be generalized to higher-order modulation schemes, where the external perturbation also causes the actual constellation points to deviate from their ideal locations, assumed when decoding under the assumption of a conventional MIMO system model. Such degraded modulation quality can then result in a bit error rate (BER) performance degradation.…”

“…Hence, the study of the near-field interaction influence on beam-space MIMO is distinct from studies carried out for the case of conventional MIMO systems. This issue was first considered in [5], where beam-space MIMO operation under BPSK signaling in the presence of the user body was studied. It has been shown that although the near-field interaction with transmit antennas in beam-space MIMO deteriorates the orthonormality of the basis patterns, throughput reduction is still mainly caused by the power absorption in user body tissues rather than by the distortion of the basis characteristics.…”

Design and Performance Evaluation of Load-Modulation MIMO System Using High-Order Modulation

“…지 문제점이 발생할 수 있다 [7] . 시스템에서 RF 단이 증가할수록 전체적인 시스템 복잡도가 증가하게 되고 이로 인하여 전력 소비 또한 급증하게 된다 [7] . 또한 RF 단이 증가하게 되면 RF 단간 간섭이 발생하여 전 체적인 시스템의 성능을 열화 시킬 수 있다.…”

“…또한 RF 단이 증가하게 되면 RF 단간 간섭이 발생하여 전 체적인 시스템의 성능을 열화 시킬 수 있다. 마지막으 로 RF 단의 증가는 전체적인 시스템 구성의 비용을 크게 증가시키게 된다 [7] . 이러한 RF 단의 증가에 따른 문제점을 해결하기 위하여 다양한 연구들이 진행되고 있다.…”