链路自适应技术在IEEE 802.16系统中的应用

Link adaptation technology and its application in IEEE802.16 system

针对IEEE 802.16系统提出了一种链路自适应方案,该方案属于自适应调制与编码方案。对于信道条件好的用户,采用高效前向纠错编码FEC(forw ard error code)方案和高阶调制方式,以提高传输效率;对于信道衰落或干扰严重的用户,分配抗噪声性能好的FEC和低阶调制方式,以保证数据的可靠传输。仿真结果表明:无论在高信噪比还是在低信噪比条件下,自适应算法均比单一的编码调制方案吞吐量有明显的提升。在高信噪比条件下,采用自适应方案后系统吞吐量比固定16 QAM调制与RS和卷积码编码的方案提高了一倍多,且误块率低于1-0 2。因此,该自适应方案在保证一定的通信可靠性的前提下,能够更有效地利用频谱资源和提高系统吞吐量。

A link adaptation scheme to the 802.16 system was presented by the physical standard of IEEE802.16. The proposed scheme could be classified into adaptive modulation and coding （AMC）. Higher code rate and modulation orders methods were assigned to the users under better channel conditions to increase the transmission efficiency, and lower code rate and modulation orders methods were applied to the users under poor channel conditions to reduce the transmission errors. The simulation results show that the proposed algorithm improved the throughput more obvious than any single modulation and coding scheme whether under high or low SNR conditions. For example, the throughput of link adaptation scheme more than doubled compared with 16QAM with RS and conventional encode method under high SNR condition. Therefore, the proposed scheme can keep the communications reliability and use the frequency resource more effectively.