Li Xujing, Liu Anfeng, Xie Mande, Xiong Neal N, Zeng Zhiwen, Cai Zhiping
School of Information Science and Engineering, Central South University, Changsha 410083, China.
The State Key Laboratory of Industrial Control Technology, Zhejiang University, Hangzhou 310027, China.
Sensors (Basel). 2018 Apr 16;18(4):1216. doi: 10.3390/s18041216.
The quality of service (QoS) regarding delay, lifetime and reliability is the key to the application of wireless sensor networks (WSNs). Data aggregation is a method to effectively reduce the data transmission volume and improve the lifetime of a network. In the previous study, a common strategy required that data wait in the queue. When the length of the queue is greater than or equal to the predetermined aggregation threshold ( N t ) or the waiting time is equal to the aggregation timer ( T t ), data are forwarded at the expense of an increase in the delay. The primary contributions of the proposed Adaptive Aggregation Routing (AAR) scheme are the following: (a) the senders select the forwarding node dynamically according to the length of the data queue, which effectively reduces the delay. In the AAR scheme, the senders send data to the nodes with a long data queue. The advantages are that first, the nodes with a long data queue need a small amount of data to perform aggregation; therefore, the transmitted data can be fully utilized to make these nodes aggregate. Second, this scheme balances the aggregating and data sending load; thus, the lifetime increases. (b) An improved AAR scheme is proposed to improve the QoS. The aggregation deadline ( T t ) and the aggregation threshold ( N t ) are dynamically changed in the network. In WSNs, nodes far from the sink have residual energy because these nodes transmit less data than the other nodes. In the improved AAR scheme, the nodes far from the sink have a small value of T t and N t to reduce delay, and the nodes near the sink are set to a large value of T t and N t to reduce energy consumption. Thus, the end to end delay is reduced, a longer lifetime is achieved, and the residual energy is fully used. Simulation results demonstrate that compared with the previous scheme, the performance of the AAR scheme is improved. This scheme reduces the delay by 14.91%, improves the lifetime by 30.91%, and increases energy efficiency by 76.40%.
关于延迟、生命周期和可靠性的服务质量（QoS）是无线传感器网络（WSN）应用的关键。数据聚合是一种有效减少数据传输量并提高网络生命周期的方法。在先前的研究中，一种常见策略要求数据在队列中等待。当队列长度大于或等于预定聚合阈值（Nt）或等待时间等于聚合定时器（Tt）时，数据将以增加延迟为代价进行转发。所提出的自适应聚合路由（AAR）方案的主要贡献如下：（a）发送方根据数据队列长度动态选择转发节点，这有效地减少了延迟。在AAR方案中，发送方将数据发送到数据队列长的节点。优点在于，首先，数据队列长的节点执行聚合所需的数据量少；因此，传输的数据可以得到充分利用以使这些节点进行聚合。其次，该方案平衡了聚合和数据发送负载；因此，生命周期得以延长。（b）提出了一种改进的AAR方案以提高QoS。聚合期限（Tt）和聚合阈值（Nt）在网络中动态变化。在WSN中，远离汇聚节点的节点具有剩余能量，因为这些节点传输的数据比其他节点少。在改进的AAR方案中，远离汇聚节点的节点Tt和Nt值较小以减少延迟，靠近汇聚节点的节点设置为较大的Tt和Nt值以减少能耗。因此，端到端延迟得以减少，实现了更长的生命周期，并且剩余能量得到了充分利用。仿真结果表明，与先前方案相比，AAR方案的性能得到了提升。该方案延迟降低了14.91%，生命周期提高了30.91%，能源效率提高了76.40%。
