Abstract

We investigate in this paper the effects of the user's presence on the performance of a multiple-input multiple-output (MIMO) system in data and in voice usage scenarios. The investigation studies the user effects on the antenna performance and how these are incorporated into the MIMO channel and the link characteristics. The antennas and the user are deterministic. These are then integrated into the statistical 3GPP spatial channel model (SCM) for a typical macrocell propagation environment setting. The channel performance is analyzed based on the average channel capacity, the average power transfer, the correlation, and the cumulative distribution function of the channel capacity as well as the link throughout and the error performance. The mentioned channel and link properties are tied to the MIMO antenna properties that are represented in the mutual coupling between the antennas, the power loss, the total radiated power, the mean effective gain (MEG), as well as the efficiency with emphasis on how the user affects each. It was found that the presence of the user contributed to a loss of up to 50% in the average channel power transfer. The data position was found to be the lowest in terms of channel capacity performance. The voice position performance showed a large dependence on the user orientation with respect to the line of sight path while the data position showed less dependence on the user's orientation. We also discuss through the examined antenna and channel properties the importance of the channel multipath on the MIMO performance. In some scenarios, it was found that a well-conditioned channel can compensate for losses due to the presence of the user, improving the overall system performance. The presented investigation at the link level also discusses the user effects in different MIMO transmission schemes.

Highlights

  • There is growing research activity investigating the interaction between the electromagnetic (EM) fields radiated from a wireless device and the human tissues

  • The presence of the user on the examined multiple-input multiple-output (MIMO) system performance is investigated first based on the antenna properties

  • We describe these in detail in the following two sections

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Summary

Introduction

There is growing research activity investigating the interaction between the electromagnetic (EM) fields radiated from a wireless device and the human tissues. The second aspect is the influence of the user’s body on the radiation properties of the mobile phone, which is significant from the antenna design point of view. The investigation presented in this paper focuses on the second aspect, the user effects on the wireless antenna device performance. Factors influencing performance in real MIMO fading scenarios include a realistic propagation channel, mutual coupling between the antennas, the antenna radiation efficiencies, and the presence of the user, among other factors. The user can have a different effect on each of the MIMO antennas in the mobile device depending on the usage scenario This causes a gain imbalance that could affect the overall system performance.

Problem Definition
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