1,074 research outputs found
An Analytical Model of Packet Collisions in IEEE 802.15.4 Wireless Networks
Numerous studies showed that concurrent transmissions can boost wireless
network performance despite collisions. While these works provide empirical
evidence that concurrent transmissions may be received reliably, existing
signal capture models only partially explain the root causes of this
phenomenon. We present a comprehensive mathematical model that reveals the
reasons and provides insights on the key parameters affecting the performance
of MSK-modulated transmissions. A major contribution is a closed-form
derivation of the receiver bit decision variable for arbitrary numbers of
colliding signals and constellations of power ratios, timing offsets, and
carrier phase offsets. We systematically explore the root causes for successful
packet delivery under concurrent transmissions across the whole parameter space
of the model. We confirm the capture threshold behavior observed in previous
studies but also reveal new insights relevant for the design of optimal
protocols: We identify capture zones depending not only on the signal power
ratio but also on time and phase offsets.Comment: Accepted for publication in the IEEE Transactions on Wireless
Communications under the title "On the Reception of Concurrent Transmissions
in Wireless Sensor Networks.
An Analytical Model for Wireless Mesh Networks with Collision-Free TDMA and Finite Queues
Wireless mesh networks are a promising technology for connecting sensors and
actuators with high flexibility and low investment costs. In industrial
applications, however, reliability is essential. Therefore, two time-slotted
medium access methods, DSME and TSCH, were added to the IEEE 802.15.4 standard.
They allow collision-free communication in multi-hop networks and provide
channel hopping for mitigating external interferences. The slot schedule used
in these networks is of high importance for the network performance. This paper
supports the development of efficient schedules by providing an analytical
model for the assessment of such schedules, focused on TSCH. A Markov chain
model for the finite queue on every node is introduced that takes the slot
distribution into account. The models of all nodes are interconnected to
calculate network metrics such as packet delivery ratio, end-to-end delay and
throughput. An evaluation compares the model with a simulation of the Orchestra
schedule. The model is applied to Orchestra as well as to two simple
distributed scheduling algorithms to demonstrate the importance of
traffic-awareness for achieving high throughput.Comment: 17 pages, 14 figure
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