Analysis of the Spatial Correlation of Indoor MIMO PLC Channels
In this letter, an analysis of the spatial correlation of multiple-input multiple-output (MIMO) power line communications (PLC) channels in the frequency range 1–80 MHz is provided, where the term spatial correlation refers to the relation between the paths that form the MIMO channel matrix. The study is based on a large set of $2\times 2$ MIMO channels measured in four different countries. The presented statistical analysis of the condition number reveals three important facts. First, the spatial correlation is almost independent of frequency, which has important implications in the development of top-down MIMO PLC channel models. Second, the use of an alternative injection method can notably reduce the spatial correlation and, consequently, increase the system bit-rate. Third, there exist countries whose channels have larger spatial correlation values than others. Since spatial correlation plays a key role in the performance of MIMO PLC systems, a hypothesis relating the type of wiring deployed in the indoor power grid to the spatial correlation is given and supported by simulations.