基于802.11ah井下监测传感网的RAW重分组研究

Research on RAW regrouping in underground monitoring sensor network based on 802.11ah

现有的ZigBee、超宽带、WiFi等井下无线传感网通信技术或传输距离短,或传输速率较低,或覆盖范围与接入设备数量受限,而IEEE 802.11ah协议满足井下无线传感网对传输范围、功耗、网络容量、传输速率等的要求,可用于井下监测传感网传输周期性监测数据。针对802.11ah协议中MAC层标准限制接入窗口(RAW)机制在进行传感节点分组时不灵活、易导致组间负载不平衡的问题,提出了一种基于时延优化的RAW重分组方法:根据数据包预计传输时间对所有传感节点重新分组,通过3次分组来减少RAW组内节点碰撞、降低传输时延。为实现RAW重分组,提出了关联标识符(AID)分组重分配方法:采用部分传感节点断开关联的方式,按重分组后的RAW组分批次为节点重新分配AID,并将AID与节点MAC映射,从而减小RAW重分组时间开销,避免AID重分配过程中因数据无法传输而导致网络性能下降。仿真结果表明,随着井下监测传感网中传感节点增多,RAW重分组方法较标准RAW机制的网络时延更小、吞吐量更大、丢包率更低,且重分组过程对网络性能影响较小。

Existing communication technologies of underground wireless sensor network such as ZigBee,ultra wide band,WiFi and so on have some shortcomings,for example,transmission distance is short,transmission rate is low,or coverage and access devices are limited.However,IEEE 802.11ah protocol meets requirements of transmission range,power consumption,network capacity and transmission rate of underground wireless sensor network,and can be used for underground monitoring sensor network to transmit periodic monitoring data.For problems of inflexible grouping for sensor nodes and load imbalance among groups existed in standard restricted access window(RAW)mechanism of MAC layer in 802.11ah protocol,a RAW regrouping method based on time delay optimization was proposed,which regrouped all the sensor nodes for three times according to projected transmission time of data packages,so as to decrease node colliding in a RAW group and transmission time delay.In order to realize RAW regrouping,an assignment identifier(AID)group reassignment method was proposed,which redistributed AID to sensor nodes group by group according to regrouped RAW group and made the AID map to MAC of the nodes by use of part nodes disconnecting access point,so as to decrease RAW regrouping time consumption and avoid network performance degradation caused by no data transmission during AID redistribution.The simulation results show that when underground monitoring sensor network adopts the RAW regrouping method,the network has less time delay,larger throughput and lower packet loss rate than the standard RAW mechanisms with sensor nodes increase,and regrouping process has little influence on the network performance.