Traffic differentiation in IEEE 802.15.4 networks: An analysis over the contention window

The increasing interest in developing solutions for applications, such as industrial automation, body sensor networks, natural risks management and prevention; without the need of a wired media has encouraged the development of a low data rate and low power consumption wireless communication systems, commonly known as Wireless Sensor Networks (WSN). Although many proprietary solutions have been proposed, the standard IEEE 802.15.4 is about to become the global standard for WSN, since utilizes energy-efficient schemes to access the channel, and to transmit information at low speeds. However, this standard does not have a strategy for information differentiation, in which packets from nodes with a higher priority need to be sent sooner than packets from other nodes. Consequently, this paper evaluates, by means of numerical simulations, the assumption of an information differentiation scheme, which consists in modifying the Contention Window (CW) in the slotted IEEE 802.15.4, considering that nodes with lower CW values have higher probabilities to access the channel than nodes with higher CW values. Partial results show that this information differentiation scheme increases the channel access probability, when two or three levels of CW are implemented within the network.