Adaptive Modulation and Frame Length Method Based on Moore State Machine in LTE-R Communication System

In this paper, the problem of adaptive modulation and frame length (AMFL) is investigated in long-term evolution for railway (LTE-R) communication system. By considering the effect of frame length, a novel AMFL strategy based on Moore state machine (MSM) is proposed. The influence of the frame length on the goodput is discussed by simulation evaluation. According to modulation and frame length schemes (MFLS) adopted in LTE-R system, the finite state set of the MSM is designed. For different MFLSs, the frame error rate (FER) and signal-to-noise ratio (SNR) curve is obtained. By giving a target FER, the SNR thresholds corresponding to different MFLSs are achieved. From the perspectives of modulation priority and frame length priority, two different AMFL-MSMs are designed to change MFLSs dynamically. Simulation results show that the proposed two AMFL-MSMs have more stable normalized goodput and less symbol energy consumption than the high-order modulation scheme. Moreover, compared with common MFLS, two AMFL-MSMs have higher average normalized goodput at different speeds.