The adaptive techniques for links are usually performed within the layers,often resulting in the optimization of local performance,but not of the entire system.This paper first presents a cross-layer design scheme for LTE systems by using two adaptive transmission techniques,i.e.Adaptive Modulation and Coding(AMC) at the physical layer and Hybrid Automatic Retransmission Request(HARQ) at the Medium Access Control(MAC) sublayer.Then,it analyzes the relationship between the cross-layer coupling parameters and...