Xie Shuanglong, Low Kay Soon, Gunawan Erry
School of Electrical and Electronic Engineering, Nanyang Technological University, 639798 Singapore.
Sensors (Basel). 2015 Mar 26;15(4):7434-53. doi: 10.3390/s150407434.
Distributed transmission rate tuning is important for a wide variety of IEEE 802.15.4 network applications such as industrial network control systems. Such systems often require each node to sustain certain throughput demand in order to guarantee the system performance. It is thus essential to determine a proper transmission rate that can meet the application requirement and compensate for network imperfections (e.g., packet loss). Such a tuning in a heterogeneous network is difficult due to the lack of modeling techniques that can deal with the heterogeneity of the network as well as the network traffic changes. In this paper, a distributed transmission rate tuning algorithm in a heterogeneous IEEE 802.15.4 CSMA/CA network is proposed. Each node uses the results of clear channel assessment (CCA) to estimate the busy channel probability. Then a mathematical framework is developed to estimate the on-going heterogeneous traffics using the busy channel probability at runtime. Finally a distributed algorithm is derived to tune the transmission rate of each node to accurately meet the throughput requirement. The algorithm does not require modifications on IEEE 802.15.4 MAC layer and it has been experimentally implemented and extensively tested using TelosB nodes with the TinyOS protocol stack. The results reveal that the algorithm is accurate and can satisfy the throughput demand. Compared with existing techniques, the algorithm is fully distributed and thus does not require any central coordination. With this property, it is able to adapt to traffic changes and re-adjust the transmission rate to the desired level, which cannot be achieved using the traditional modeling techniques.
分布式传输速率调整对于诸如工业网络控制系统等多种IEEE 802.15.4网络应用而言至关重要。此类系统通常要求每个节点维持一定的吞吐量需求，以保证系统性能。因此，确定一个能够满足应用需求并补偿网络缺陷（如丢包）的合适传输速率至关重要。由于缺乏能够处理网络异构性以及网络流量变化的建模技术，在异构网络中进行这样的调整十分困难。本文提出了一种异构IEEE 802.15.4 CSMA/CA网络中的分布式传输速率调整算法。每个节点利用空闲信道评估（CCA）的结果来估计忙信道概率。然后开发一个数学框架，在运行时利用忙信道概率来估计正在进行的异构流量。最后推导一种分布式算法来调整每个节点的传输速率，以准确满足吞吐量需求。该算法无需对IEEE 802.15.4 MAC层进行修改，并且已使用带有TinyOS协议栈的TelosB节点进行了实验实现和广泛测试。结果表明该算法准确且能够满足吞吐量需求。与现有技术相比，该算法是完全分布式的，并因此不需要任何中央协调。具备此特性，它能够适应流量变化并将传输速率重新调整到期望水平，而这是传统建模技术无法实现的。
