Abstract
Wireless sensor networks based on the IEEE 802.15.4 standard are able to achieve low-power transmissions in the guise of low-rate and short-distance wireless personal area networks (WPANs). The slotted carrier sense multiple access with collision avoidance (CSMA/CA) is used for contention mechanism. Sensor nodes perform a backoff process as soon as the clear channel assessment (CCA) detects a busy channel. In doing so they may neglect the implicit information of the failed CCA detection and further cause the redundant sensing. The blind backoff process in the slotted CSMA/CA will cause lower channel utilization. This paper proposes an additional carrier sensing (ACS) algorithm based on IEEE 802.15.4 to enhance the carrier sensing mechanism for the original slotted CSMA/CA. An analytical Markov chain model is developed to evaluate the performance of the ACS algorithm. Both analytical and simulation results show that the proposed algorithm performs better than IEEE 802.15.4, which in turn significantly improves throughput, average medium access control (MAC) delay and power consumption of CCA detection.
Highlights
The IEEE 802.15.4 standard [1] is uniquely designed to meet the requirements of low rate wireless personal area networks (LR-WPANs) to enable wireless sensor network applications [2,3,4]
We further compare with the IEEE 802.15.4 standard for throughput, average medium access control (MAC) delay and the number of clear channel assessment (CCA) sent before packet transmission, where the analytical results are obtained from [14]
The results show that additional carrier sensing (ACS) has the smaller number of CCAs than IEEE 802.15.4, which means that ACS uses less power consumed by CCAs than IEEE 802.15.4
Summary
The IEEE 802.15.4 standard [1] is uniquely designed to meet the requirements of low rate wireless personal area networks (LR-WPANs) to enable wireless sensor network applications [2,3,4]. The IEEE 802.15.4 medium access control (MAC) protocol employs slotted carrier sense multiple access with collision avoidance (CSMA/CA) to access the channel and uses a random backoff algorithm to reduce the collision probability. A node performs carrier sensing only when the backoff process is completed, and this causes lower channel utilization and longer average delays. Algorithm based on the IEEE 802.15.4 acknowledgement mode to detect the channel condition whenever the second CCA detects a busy channel. It can provide accurate information that the busy channel is caused by data or an acknowledged packet transmission in the second CCA detection. We develop a Markov chain model for ACS algorithm by integrating the models from [13,14]. By analysis and simulation experiments, ACS improves the throughput and delay performance but does not increase the energy consumption
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