LTE Testing
LTE Testing
LTE Testing - Channel Emulation Challenges
3GPP LTE testing introduces many changes to the current cellular systems. New technologies utilized in LTE such as MIMO, high order modulation schemes like 64 QAM and totally new air interface scheme SF-FDMA has to be tested and validated against realistic radio environment. Also, LTE will utilize much higher bandwidth compared to existing standards. The maximum bandwidth defined in the 3GPP specifications is 20 MHz. Due to higher bandwidth the system is more sensitive to different radio channel effects. New channel models like SCME have been defined for LTE testing to reach the next level of accuracy in the testing.
Product Performance and System Level Testing
The target of the testing with channel emulator is to ensure the best product performance in the live network. The testing with the EB Propsim channel emulators enables 100 % repeatability of the test scenarios in laboratory environment thus minimizing the need for field testing.
In the early LTE deployment systems will utilize 2x2 MIMO and later also 4x4 MIMO will be deployed. LTE standard defines conformance test models and testing with these the basic product performance and functionality can be verified. However, with conformance test scenarios it is not possible to find the LTE product performance limits. SCME radio channel model is designed to find the maximum product performance by modeling the radio environment with the highest accuracy. SCME model is fully supported by EB Propsim emulators and that will help LTE developers to improve competitiveness of their products in the market.
The testing and verification of single link (MS <- -> Node) performance is a must for successful business in LTE. However, the highest capacity and performance improvement in the network can be obtained by optimizing the parameters and algorithms at the system level. System level refers to test scenario with real terminals and eNodeB's connected together through real radio environment both in downlink and uplink. Very common test setup is handover testing (see figure below). Two eNodeB's and one terminal are connected together. Each connection utilizes 2x2 MIMO link and all together the setup has 16 channels. The functionality and performance of EB Propsim products are designed to meet the requirements in system level testing.
Product Conformance Testing
Product conformance testing refers to executing test cases defined in 3GPP LTE testing specifications. Channel emulators are needed in performance test cases. Currently planned test scenarios include 2x2, 2x4 and 4x4 MIMO setups. The channel models are derived from ITU models by adding MIMO dimension to the models. In the conformance testing the emulator usability and test automation capability are the most important elements. EB solution to LTE conformance testing is EB Propsim FE. Ready made test scenarios and model libraries enable smooth test execution through carefully planned user interface. In the typical LTE product lifecycle there are several SW releases and execution of conformance test cases after every SW update reveals possible problems in the design. Software is often updated, thus the same tests has to be executed regularly. Test automation features are therefore essential to enable for example overnight unmanned test runs. EB Propsim FE has two test automation interfaces: GPIB or LAN interface. Extensive test automation command library makes the test script programming very easy. Once the test scripts are created, only execution of the script is needed to get the LTE testing results.