ABSTRACT
M.R. Palattella, A. Faridi, G. Boggia, P. Camarda, L.A. Grieco, M. Dohler,
A. Lozano
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 3.2 IEEE 802.15.4 WPANs: An Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
3.2.1 Superframe Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 3.2.2 The Slotted CSMA/CA Mechanism . . . . . . . . . . . . . . . . . . . . . . . . 59
3.3 Markov Chains for the Slotted CSMA/CA . . . . . . . . . . . . . . . . . . . . . . . . . . 61 3.4 System Model and Notation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
3.4.1 Markov Chain Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 3.4.2 Discussion of the Pollin Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
3.5 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 3.5.1 Average Delay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 3.5.2 Average Power Consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 3.5.3 Mean Number of Backoffs and CCAs . . . . . . . . . . . . . . . . . . . . . . 72
3.5.3.1 Mean Number of Backoffs . . . . . . . . . . . . . . . . . . . 72 3.5.3.2 Mean Number of CCAs . . . . . . . . . . . . . . . . . . . . . . 75
3.5.4 Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
. . . . . . . . . . . . . . . . . . . . . . . . . 3.6.1 Dependence of α and β on the Backoff Stage . . . . . . . . . . . . . . 79 3.6.2 Dependence of the Backoff Stage of a Node on That of Other
Nodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 3.7 Conclusion and Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
In this chapter, the IEEE 802.15.4 MAC layer is modeled using a per-node Markov
chain model. Using this model, expressions for various performance metrics includ-
ing delay, throughput, power consumption, and efficiency, are derived and such ex-
pressions are subsequently validated against the corresponding values obtained via
simulation. The simplifying assumptions required by the Markov-chain analysis are
studied and their impact on the performance metrics is quantified.
