MIMO capacity estimation based on single and dual-polarization MIMO channel measurements

Abstract

Multiple-Input Multiple-Output (MIMO) wireless system is one of the most promising technologies for providing a large transmission capacity without expanding the frequency band in cellular mobile systems. This paper focuses on 2x2 MIMO capacity estimation through propagation measurements at 2GHz band. The authors conducted the measurement campaign in two regions in Fujimino (Saitama prefecture) and Yokohama (Kanagawa prefecture) Japan. The former is a typical residential area and the latter is an urban area. The paper compares MIMO spatial multiplexing efficiency in terms of the eigenvalue ratio between the single and orthogonal dualpolarization antenna configurations. The eigenvalue ratio is characterized by two parameters. One is cross-polarization discrimination (XPD) and the other is the normalized received signal strength indicator (RSSI), which represents the difference from the RSSI when free space propagation is assumed. It is verified that the MIMO capacity of the dual-polarization can be estimated from just the SNR because the dependency of the eigenvalue ratio on the propagation environment is small. In contrast, that of the single-polarization needs to consider both the eigenvalue ratio and the SNR because the eigenvalue ratios change significantly due to the propagation environment.

2 × 2 MIMO channel characteristics under received power imbalance through indoor propagation measurements

“…Table 2 shows the channel capacity for each antenna spacing, which is normalized by that of single-inputsingle-output (SISO). Here, channel capacity is calculated from the eigenvalue ratios and the average SNR of received antennas as demonstrated in [6]. decreases when the received power imbalance increases; the decrement is greater than the improvement effect of antenna correlation due to the large antenna spacing.…”

“…The eigenvalue ratio is a measure expressing MIMO spatial multiplexing efficiency. MIMO capacity is calculated from the eigenvalue ratio and average signal-to-noise ratio (SNR) between receiver antennas [6]. MIMO capacity increases when the eigenvalue ratio increases under fixed SNR.…”

Channel capacity estimation method for 2 × 2 MIMO considering received power imbalance and antenna correlation

“…The 2 x 2 MIMO channel capacity can be derived by using the eigenvalue ratio and the average SNR of two receiver antennas [3]. …”

“…However, the derivation of eigenvalues requires matrix operation using singular value decomposition. We first proposed a calculation method of the channel capacity for 2 x 2 MIMO using an eigenvalue ratio, which is the ratio of the second eigenvalue to the first one [3]. After that, study [1] showed that the eigenvalue ratio can be estimated only from the received power imbalance.…”

Novel Cellular Active Array Antenna System at Base Station for Beyond 4G

“…Conventional two-branch MIMO could be easily implemented by a single antenna using orthogonal polarization [1]. On the other hand, for three branch MIMO (or more), more antenna poles are needed [2]. This is very expensive, resulting in high CAPEX levels.…”