Abstract
We propose a novel analytical model to study fragmentation methods in wireless sensor networks adopting the Constrained Application Protocol (CoAP) and the IEEE 802.15.4 standard for medium access control (MAC). The blockwise transfer technique proposed in CoAP and the 6LoWPAN fragmentation are included in the analysis. The two techniques are compared in terms of reliability and delay, depending on the traffic, the number of nodes and the parameters of the IEEE 802.15.4 MAC. The results are validated trough Monte Carlo simulations. To the best of our knowledge this is the first study that evaluates and compares analytically the performance of CoAP blockwise transfer and 6LoWPAN fragmentation. A major contribution is the possibility to understand the behavior of both techniques with different network conditions. Our results show that 6LoWPAN fragmentation is preferable for delay-constrained applications. For highly congested networks, the blockwise transfer slightly outperforms 6LoWPAN fragmentation in terms of reliability.
Highlights
In the recent years, the Internet of Things (IoT) has emerged as one of the most promising developments of the Internet of the future
A greater size implies the use of 6LoWPAN fragmentation to send a single block, which would not allow analysing the behavior of Constrained Application Protocol (CoAP) blockwise transfer
In the rest of this section we present the expressions for the performance metrics that we use to evaluate CoAP blockwise transfer and 6LoWPAN fragmentation
Summary
The Internet of Things (IoT) has emerged as one of the most promising developments of the Internet of the future. This allows a client node to register to a resource exposed by a server node and to receive updates of its states The application of this model helps to reduce the request/response interaction and it is useful in WSN monitoring applications. Our model considers the presence of the Carrier-Sense Multiple Access with Collision Avoidance (CSMA/CA) mechanism defined by the IEEE 802.15.4 standard The inclusion of this mechanism is instrumental to understand the interaction between higher-layer protocols such as 6LoWPAN and. It is typically assumed that the application layer generates packets following a known traffic distribution (e.g., the Poisson distribution), the subsequent fragmentation or block division implies a bursty transmission at MAC layer.
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