使用者遠離時,因為與基地台的距離發生變化,導致接收訊號越來越差,此時想要維持良好的服務品質(Quality of Services),基地台可以利用適應性調變與編碼(Adaptive Modulation and Coding)技術,適時的改變調變與編碼方式,以維持服務品質。
本論文主要在討論調變(Modulation)、編碼(Coding)以及多天線技術(Multiple-Input Multiple-Output),在高速環境下,對於系統效能的影響,並且提供在不同訊雜比(Signal Noise Ratio)、不同速度下,使用何種調變與編碼的建議表。 Most generation wireless communication systems are based on Orthogonal frequency-division multiplexing transmission technology. Besides the transmission technology changes, to avoid break down when users communicate by phone and support users in high speed environment are important. In a moving channel, doppler spread will cause inter carrier interference. It will affect performance seriously.
When the users far away form base station, the received signal will become weak. If we want to keep good quality of services, we can use adaptive modulation and coding technology to change the combination of modulation and coding.
In this paper, we will discuss the performance in different modulation, coding, and MIMO system in high speed environment and give an adaptive modulation and coding table in different speed and signal noise ratio.