MIMO Over The Air testing Quantifiable Business Benefits to Device OEM's and Operators
Quantifiable business benefits can be achieved by testing your LTE products with the EB Propsim F8/F32 and its MIMO OTA feature, be it a dongles or smartphones. Properly developed and tested MIMO feature enable greater throughput that can ultimately drive end user satisfaction in networks, smartphones and services thus drive growth in revenue in the whole wireless ecosystem.
MIMO in radio technology stands for multiple-input and multiple-output. It is the use of multiple antennas at both the transmitter and receiver. OTA, or Over The Air in testing means the use of an anechoic chamber in combination with an emulator, like the EB Propsim, and relevant number of antennas to make the performance measurement without cables connected to the device under test (DUT). The system is scalable from a single cluster to full 3D. The EB MIMO OTA solution consists of a test transmitter, the EB Propsim F8/F32 MIMO OTA emulator with the EB MIMO OTA application, an anechoic chamber equipped with OTA antennas and required accessories such as cabling.
The picture illustrates an entry Level single cluster MIMO OTA set up with three antennas. As a 42MHz bandwidth system, the solution consists of three dual polarized antennas, a 6 channel EB Propsim F8/32 radio channel emulator and required accessories. The system uses pre-defined realistic and repeatable single cluster channel models. With these models, the performance of a MIMO-capable device can be easily tested, allowing operators and OEMs to swiftly check devices to determine their quality and suitability for LTE mobile broadband networks. As a three antenna system, it can be installed in a small anechoic chamber.
The picture illustrates a full MIMO OTA test solution giving operators, OEM's and chipset vendors the possibility to verify the true performance of the device under test (DUT) under multicluster radio channel environment. These multicluster radio channels models such as SCM, SCM and WINNER are based on field measurements and thus using them in the laboratory testing will increase the confidence to the performance of DUT in field conditions. In addition user defined channel models can be created with specific parameters in order to test certain features in the design such as polarization performance.
Typically MIMO is used to increase the spectral efficiency, i.e. more data on same bandwidth enabling high data rate services. The MIMO feature can improve capacity of a handset as signal can be sent via multiple antennas. A badly tested dongle or smartphone released to market with bad antenna design can result in bad performance and thus be disappointing to customers.
The picture above illustrates how the reduction in signal strength from a basestation impacts on the (wireless broadband) capacity of the handset. Phones 1 and 3 still have good wireless broadband capacity as the signal from the base station gets weaker. Ultimately this means that the phone can work better in the minds of the end user, the MIMO feature ultimately driving higher data throughput enabling smooth use of services and applications which again can drive customer satisfaction enabling further sales thus accelerating ROI and profit.
Research done by EB together with the French CEA-LETI Research Center (picture above), demonstrates how a MIMO optimised antenna can send double the capacity compared with a non optimised one. The black circle on the blue line indicates that antenna capacity and throughput on a given radio channel condition is less than 0.5 bps/Hz when the red line shows a MIMO optimised antenna having over double of the capacity, over 1bps/Hz.
Performance of a MIMO device is determined by the antenna design and the radio channel. To evaluate the real performance of a MIMO device, the testing needs to be done in a realistic radio channel propagation environment with antennas integrated to final product.
Field tests give you the right result on a particular moment, i.e. when the testing is done. Here repeatability is an issue. Laboratory testing again is repeatable - this being a key requirement for debugging. Enhanced smartphone capacity driven by MIMO performance is dependent on antenna design. Testing the MIMO designs over the air is the best way to verify the antennas performance.
By testing a MIMO feature Over The Air, Operators can compare phones performance and choose the optimal smartphones and dongles for their network. By choosing right phones an operator is able to drive improved customer satisfaction with better capacity driving services and application usage - raising the Average Revenue Per User. By using MIMO optimized products, operators are able to reduce CAPEX as greater coverage can be achieved with less network elements. To enable full use of mobile broadband services, it is clearly in the interest of the operator to demand for the MIMO feature to be implemented into products.
A smartphone with higher receive sensitivity can extend its connectivity range. The picture above illustrates a bad urban network coverage example and the impact of 1 decibel improvement in signal strength. Here a MIMO optimized smartphone or dongle is capable of receiving the signal at a longer range giving the network a better coverage for less network elements. Improved network element range and capacity are keys for driving end-user satisfactions in mobile service usage, being a key enabler for accelerated ROI.