Quantifying the Impact of 4x4 MIMO in a Commercial LTE Network
In this Signals Ahead report we provide the results from the industry’s first and only independent performance analysis of 4×4 MIMO. For this study we used the T-Mobile commercial LTE network in the Minneapolis market where Nokia is the infrastructure supplier.
Highlights of the Report include the following:
Our Thanks. This study could not have been done without the support of Accuver Americas, who provided us with its XCAL-M drive test tool as well as its XCAP post-processing solution to analyze the data that we collected.
Our Approach. We burned through more than 9 SIM cards (28 GB each) while transferring data on Samsung Galaxy S7 smartphones. We purchased one S7 from a T-Mobile store. This phone supported 4×4 MIMO, 256-QAM, and a 4-way receive antenna architecture, as well as uplink 64-QAM. We also purchased an unlocked S7 from a Best Buy store. This phone did not support any of these features. We configured the phones so that they only operated in Band 4 to maximize the potential use of 4×4 MIMO. We used the Datum application from Spirent Communications in order to generate the downlink and uplink traffic.
The Tease. Over the course of all testing, including various morphologies and clusters of 4×4 and 2×2 MIMO sites, we observed that the median downlink data rate for the T-Mobile S7 was 55% higher than the Best Buy S7.
The Detailed Analysis. In the main body of the report we analyze the performance differences between the two smartphones in excruciating detail. We quantify the incremental benefits of RI = 3/4 only, 256-QAM only, and mixed use of 256-QAM and RI = 3/4, as well as the benefits of a 4-way receive antenna architecture.
What about Power? We quantify how the LTE-Advanced features that we tested impacted battery life, including normalized results which take into consideration differences in measured data speeds.
What about the Uplink? Following our major study of uplink performance, based on testing in Seoul, South Korea, we revisit the impact of uplink 64-QAM on the uplink performance with a particular focus on the probability that the mobile device uses the higher modulation scheme. The findings are surprising.