Supported by IEEE 802.15.4 standardization activities, embedded networks have been gaining in popularity in recent years. The focus of this paper is to quantify the behavior of key networking metrics of IEEE 802.15.4 beacon-enabled nodes under typical operating conditions, with the inclusion of packet retransmissions. We correct and extend previous analyses by scrutinizing the assumptions on which the prevalent Markovian modeling is generally based. By means of a comparative study, we single out which of the assumptions impact each of the performance metrics (throughput, delay, power consumption, collision probability, and packet discard probability). In particular, we show that—unlike what is usually assumed—the probability that a node senses the channel busy is not constant for all the stages of the backoff procedure and that these differences have a noticeable impact on backoff delay, packet discard probability, and power consumption. Similarly, we show that—again contrary to common assumption—the probability of obtaining transmission access to the channel depends on the number of nodes that are simultaneously sensing it. We evidence that ignoring this dependance has a significant impact on the calculated values of throughput and collision probability. Circumventing these and other assumptions, we rigorously characterize, through a semi-analytical approach, the key metrics in a beacon-enabled IEEE 802.15.4 system with retransmissions.

%8 10/2010