We used LTE-A  Vinna simulator to model and simulate the higher order modulation for LTE-A:https://www.researchgate.net/publication/301748508_Performance_analysis_of_LTE-A_with_256-QAM

For more information about Vienna LTE simulator please follow the link:https://www.nt.tuwien.ac.at/research/mobile-communications/vccs/vienna-lte-a-simulators/

Best wishes

Conference Paper Performance analysis of LTE-A with 256-QAM

We use NetSim (http://www.tetcos.com) and have found it easy to use with a GUI, and easy to modify the underlying source code for R & D work. NetSim v10 supports LTE, LTE-A, LE D2D and LTE Femto cell.

@Rahul Kumar is it expensive for professional researchers?is there available resources and helps?

You can use omnet and add a library to it