Implementation of Water-Filling algorithm for optimal power allocation in the wireless channel of a MIMO 2x2 system over SDR

In the present work a water-filling strategy algorithm is designed and implemented to apply the optimal power allocation for a MIMO 2x2 system using the channel state information (CSI), based on Software Defined Radio technology (SDR). First, it’s done a study of the background of MIMO communications, it’s quality depending on the CSI and power allocation method. And also is studied Orthogonal Frequency Division Multiplexing (OFDM), which is the most popular modulation used in various standards like LTE or WiFi. Then, the implementation of the algorithm is done with GNU Radio using the NI USRP 2950R and NI USRP 2920 Radios. And finally, distance-based tests were done to measure and compare the bit error rate (BER), getting an improvement of 25% on average between an ordinary system and a system with optimal power allocation at distances of 1, 1.5, 2 and 3 meters, where the power allocation are seen through waterbars graphics as a characterization of the wireless channel for MIMO 2x2.