Yilin Ji

Measurement-Based Characterization of 15 GHz Propagation Channels in a Laboratory Environment

In this paper, measurements in a laboratory characterizing the 15-GHz band propagation channels are introduced. Both an omnidirectional antenna (ODA) and a 10° half-power-beamwidth (HPBW) pyramidal horn antenna are deployed at the transmitter (Tx) in different measurements. The receiver (Rx) is equipped with a 10° HPBW horn antenna. A direction-scanning sounding method is applied by rotating the Rx horn antenna in steps of 5° to collect channel impulse responses (CIRs) in the angular domains. Clusters are extracted based on power concentration from the 3-D power spectrum in delay, azimuth, and zenith arrival angles. Each cluster represents the contribution of specular paths with similar delay, azimuth, and zenith arrival angles, and of the diffuse-scattering components spreading around these paths. The mapping of the propagation paths reconstructed from the extracted clusters to the physical interacting objects in the environment is found to be reasonable. Differences on channel characteristics are compared for both a horn antenna and an ODA at the Tx. Finally, a stochastic cluster model is provided based on five measurements in the laboratory for the case where the ODA is used at the Tx.

Experimental Evaluation of User Influence on Test Zone Size in Multi-Probe Anechoic Chamber Setups

Over-the-air (OTA) radiated testing for multiple-input multiple-output (MIMO) capable mobile terminals has been actively discussed in the standardization in recent years, where multi-probe anechoic chamber (MPAC) method has been selected, together with the radiated two-stage method. The supported test zone size is a key parameter to determine for an MPAC design, and the test zone size is restricted by the number of OTA antennas. A larger test zone would necessitate more OTA antennas, each port of which is driven by an expensive channel emulator radio frequency interface. Results available in the literature are typically limited to free space scenarios, where no user effect in the vicinity of MIMO terminal is present. There is a concern whether or not the test zone size should encompass the user phantom, together with the mobile terminal in the MPAC setup. To address this issue, an extensive measurement campaign was carried out in this paper. Two realistic long term evolution mockups were designed and their performance were evaluated under standard spatial channel models with and without the presence of user phantom. The measurement results have shown that the nearby user phantom can significantly affect the MIMO performance. However, its impact on the test zone size of the MPAC system is negligible, since emulation accuracy in terms of received power, branch power ratio, antenna correlation, and measured throughput under the target and the emulated channels is not affected by the presence of user phantom. Moreover, results measured with the synthetic MPAC method generally match those obtained with the reference two-stage method. These findings are valuable inputs for the ongoing MIMO OTA harmonization work in the standardization.