An adaptive modulation and relaying scheme in WiMAX systems

IEEE 802.16, which supports adaptions among different modulation and coding schemes, flexibly adjusts to complicated tactical scenarios. In this paper, by modeling the problem and determining proper metrics, we investigate the bit error ratio, spectrum efficiency, and the length of cyclic prefix under different modulation schemes, thus concluding that choosing a proper modulation and coding scheme adaptively according the channel SNR can achieve higher spectrum efficiency. Furthermore, we have considered a one-hop relay scenario where relays are leveraged to enlarge the transmission range and increase the capacity. Simulation results show that the amplifying and forwarding relays can evidently enhance the capacity of the system. If the forwarding power of a relaying node were raised, the capacity would be improved even more. The simulation validates the design, supporting the employment of relays in tactical communications.