时隙ALOHA二进制指数回退算法

Binary exponential backoff algorithm for slotted ALOHA

时隙ALOHA由于简单而被广泛应用于无线通信中,但时隙ALOHA本质上是不稳定的,各种控制算法被应用以保证系统的稳定吞吐量。在建立二进制指数回退(BEB)算法的马尔可夫模型基础上,分析了系统的稳定性调节过程。数值计算和仿真测试表明二进制指数回退算法能够保证系统的稳定性,且当节点数在一定范围内时能获得时隙ALOHA的理论极限吞吐量。比较了二进制指数回退算法与伪贝叶斯算法在平均吞吐量的性能差异,结果表明,BEB算法受窗口值的影响,当用户数较大(大于128)或较小(小于32)时,吞吐量均较伪贝叶斯算法低。

Slot-ALOHA is widely used in wireless communications due to its simplicity. However, because slot-ALOHA is not stable in essence, many algorithms have been used to provide steady throughput. After founding the Markov model for Binary Exponent Backoff （BEB） algorithm, this paper analyzed the adjusting progress, The numerical computation and simulation results demonstrate that BEB algorithm can guarantee the system steady and the theoretic throughput can be derived when the number of modes is within certain range. By comparing throughput of BEB to that of Pseudo-Bayesian Control Algorithm （ PBCA）, it can derive that the throughput of BEB is less than PBCA when the number of users is either too big or small because of being influenced by the baekoff window size.