Analysis of increasing channel capacity of MIMO communication system by vortex electromagnetic wave

Abstract

Multiple-input and multiple-output (MIMO) communication technology which depends on multipath reflection can bring more efficient use of spectrum and higher channel capacity without expanding the bandwidth. This technology has been widely used in 5G communication system these days. However, under some circumstances which are lack of multipath reflection, the performance of traditional MIMO communication is not satisfying. Therefore, some researchers have pointed out that the technology of vortex electromagnetic wave can improve this situation efficiently. This article has done some researches on analyzing the channel capacity in traditional MIMO system and the MIMO system with vortex electromagnetic wave. Firstly, the spatial channel geometry model has been established with a 4-antenna transmit array and a 25-antenna receiving array in a three-dimensional rectangular coordinate system. In order to obtain the total channel capacity, the Los channel fading matrix should be calculated through calculating the distances between each two transmit and receiving antennas. After that the water filling algorithm has been used to decide the power allocation method to each subchannel to get the maximum capacity of the system. Finally, the relationship between maximum channel capacities and the signal-noise ratio (SNR) can be plotted as a line chart. The experiment first compared the capacities with and without the vortex electromagnetic wave of MIMO communication system under different SNR and found that the adding of vortex electromagnetic wave can increase the capacity efficiently. Next the influences of some variables to the channel capacity include the height of transmit antenna array, the distance between each two nearby transmit antenna elements and the variable Q which can change the phase complexity of wavefront have been discussed.