中文摘要：

IEEE 802．16宽带无线接入系统在其上行媒体接入控制层采用时，分复用和资源竞争与预留的方式进行接入，各用户站（SS）之间存在着竞争与冲突，这将导致系统性能下降。该文针对SS在碰撞以后的冲突解决过程提出了一种快速有效的冲突解决算法——动态退避控制（Dynamical Backoff Control，DBC）算法。在该算法中，基站（BS）通过预测下一个上行帧中将会出现的带宽请求报文数，动态地控制SS的退避范围，以增大每帧中成功发送的带宽请求报文数，从而提高MAC层的数据吞吐，降低SS的平均接入延迟。利用OPNET对DBC和二进制指数退避两种算法进行了仿真。仿真结果显示DBC算法对系统性能有一定的改善和提高。

英文摘要：

IEEE 802.16 broadband wireless access system adopts TDMA （Time-Division Multiple Access） and contention-based reservation of resource in its uplink MAC layer. Thus there are contentions and collisions between SSs（Subscriber Stations）, and the performance is inevitably deteriorated. A fast and efficient backoff algorithm DBC （Dynamical Backoff Control） is proposed to solve the problem. In DBC, by predicting the number of request messages in next uplink frame, BS controls the optimal backoff ranges dynamically. As a result, the successful rate of sending request messages in each frame is increased, the data throughput of MAC layer is promoted, and the mean access delay of SS is reduced. Simulation is conducted in OPNET to compare DBC with binary exponential backoff. Simulation results demonstrate that proposed DBC algorithm makes a great improvement in system performance.