# Research on Performance Metrics and Environmental Conditions for 5G MIMO OTA
## 2 Experimental Specification  
In this paper, 10 commercial smartphones available on the Chinese market have been randomly selected and a MIMO OTA measurement has been performed at the China Academy of Information and Communications Technology (CAICT) Multi-probe Anechoic Chamber (MPAC) using test methods adopted by the 3 GPP LTE MIMO OTA specification TR37.977 and the CTIA MIMO OTA Test Plan [17]. The system configuration and measurement environment are illustrated in Figure 1, where 8 dual-polarized probes are uniformly distributed around the DUT as an azimuth ring with 16 channels of spatial channel emulation. All DUTs are measured with both UMi and UMa channel models under different environmental conditions. The \"white box\" test approach has been adopted for LTE MIMO OTA at frequency bands higher than 1 GHz in order to ensure consistent DUT placement, whereas a black box approach has been selected for 5G Band 5 (881.5 MHz) scenarios with larger than 30 cm test zones. All DUTs are fully contained within the test zone, the physical center of which is aligned with the center of the test zone. The experimental setup is summarized in Table 2. For a comprehensive analysis, the measured raw data are averaged in both TRMS and MARSS manners, respectively.  
Figure 1: The system configuration (**a**) and measurement environment (**b**) of MPAC with multiple channel emulators and output amplifiers.  
The average TRMS of free space data mode portrait (FS DMP), free space data mode landscape (FS DML) and free space data mode screen up (FS DMSU), is defined as the FoM of LTE MIMO OTA in 3 GPP. The average shall be done in a linear scale for the TRMS results at these device positions, as shown in Equation (1):  
\[\mathrm{TRMS_{average,x}}=10\log\biggl{[}3\bigg{/}\biggl{(}\frac{1}{10^{5_{ \mathrm{FS}}\ \mathrm{DMP_{x}}/10}}+\frac{1}{10^{5_{\mathrm{FS}}\ \mathrm{DML_{x}}/10}}+\frac{1}{10^{5_{\mathrm{FS}}\ \mathrm{DML_{x}}/10}}\biggr{)}\biggr{]} \tag{1}\]  
where:  
\[\mathrm{S_{MODE,x}}=10\log\biggl{[}12\bigg{/}\biggl{(}\frac{1}{10^{5_{\mathrm{ MODE,x}}/10}}+\frac{1}{10^{5_{\mathrm{MODE,x}}/10}}+\cdots+\frac{1}{10^{5_{ \mathrm{MODE,x}}/10}}\biggr{)}\biggr{]} \tag{2}\]  
Such that MODE is one of {FS DMP, FS DML, FS DMSU}, x is one of thresholds (for example [[70%, 90%, 95%]]), and {P\({}_{MODE,x}\),0,..., P\({}_{MODE,x}\),11} are the measured sensitivity values at each azimuth position.  
The MARSS is defined as the FoM of LTE MIMO OTA in CTIA. The sensitivity point is defined as the SIR value (in dB) required to reach 70%, 90%, and 95% of the theoretical maximum throughput of the test case. The SIR value (in dB) associated with each outage point at the m\({}_{\mathrm{th}}\) EUT rotation is defined as the effective throughput SIR sensitivity (P\({}_{\mathrm{ETS,70,m}}\), P\({}_{\mathrm{ETS,90,m}}\), and P\({}_{\mathrm{ETS,95,m}}\)).  
The MARSS is computed as a linear average from the effective radiated sensitivity measurements across all EUT rotations and is given as follows:  
\[\mathrm{P_{MARSS,x}}=10\log_{10}\left(\frac{1}{\mathrm{M}}\sum_{m=1}^{\mathrm{ M}}10^{P_{\mathrm{ETS,x}}\sim m}\right) \tag{3}\]  
where M is the total number of azimuth positions, i.e., 12, x is one of thresholds (for example {[[70%, 90%, 95%]]), and P\({}_{\mathrm{ETS,x}}\),m is the measured effective throughput SIR sensitivity at each azimuth position.