Multiple input multiple output (MIMO) is an effective method for increasing data rates and employs multiple antennas at the transmit and receive end. MIMO is used in state-of-the-art mobile radio standards such as 3GPP LTE/LTE-Advanced, HSPA+ and WLAN 802.11n. This is why the efficient testing and generation of LTE MIMO signals is crucial for makers of wireless communications infrastructure equipment such as base stations and small cells.  

The test setup from Rohde & Schwarz and ASTRI includes a high-end R&S SMU200A vector signal generator, which generates a faded EUTRA/LTE uplink signal with 2x2 MIMO. This MIMO signal is received and demodulated by ASTRI's LTE-Advanced small cell. The R&S RTO digital oscilloscope acquires the 2x2 MIMO downlink signal output by the small cell. The signal is analyzed on a PC using the R&S FS-K102PC EUTRA/LTE downlink MIMO software.   

The R&S RTO oscilloscope is well-suited for this application since it can acquire an up to 4x4 MIMO signal thanks to its four input channels. The frontends of the R&S RTO have outstanding characteristics such as high input sensitivity and extremely low noise. The high dynamic range of the R&S RTO delivers signal analysis results comparable with those of a mid-range signal analyzer.  

Thanks to its two-path architecture, the R&S SMU200A is ideal for carrying out receiver tests on 2x2 MIMO systems requiring two signal sources. In addition, standard-compliant MIMO fading must be simulated to determine the performance of the base station under realistic operating conditions. The R&S SMU200A combines RF and baseband signal generation and fading simulation for 2x2 MIMO in a single instrument, making it possible to carry out the 3GPP conformance testing on MIMO base stations with minimal use of hardware.  

The Hong Kong Applied Science and Technology Institute (ASTRI), the leader in LTE and LTE-Advanced small cell technology, provides the DUT for the test setup. The company has been developing reference designs for TD-LTE and LTE FDD small cells since 2008, including the first market-ready reference designs for small cells supporting both TD-LTE and LTE FDD. For development, ASTRI relies on Rohde & Schwarz test solutions. For example, ASTRI already characterized 4x4 MIMO antenna configurations with the help of an R&S RTO oscilloscope and two R&S SMU200A vector signal generators.  

Rohde & Schwarz and ASTRI demonstrate the test solution live at the Rohde & Schwarz booth (hall 6, booth E30) at the Mobile World Congress, which will be hosted at the new Fira Gran Via exhibition center in Barcelona.