The Structure Determined of Low Ill-condition Structure Constraint Spatial Modulation for Massive Multi-Color MIMO-VLC

Massive multi-color multiple-input multiple-output visible light communications (m-MCMIMO VLC) system sufficiently utilizing spatial resources is proposed to satisfy super-speed and high-density depth-coverage requirements of next generation indoor data connections. While high inter-channel interference and a gap between the number of LEDs and PDs are main factors limiting system performance. The activated LEDs layout is constrained to the structure with low ill-condition channel gain matrix to increase the system detection algorithm performance, and activated LEDs number matches the PDs. Based on the idea, low ill-condition structure constraint spatial modulation (LISCSM) taking the condition number as the objective function is proposed greatly dealing with the bottlenecks. This letter determine the constraint structure of LISCSM through comparing the circle closed structure with linear, because of the requirements for uniform illumination of LED layout in space. In this paper, the channel state information is known at the transmitter. The fitting curve of the optimal parameter of each structure and the channel parameters is obtained by simulating. And the circle closed structure performs better at wide suitability and BER performance than linear structure under the channel-adapted optimal parameter, so the circle closed structure determined to be the constraint structure of LISCSM.