The IEEE 802.15.4 standard has no provisions for rate sensitive applications because of its ability to operate in pure CSMA/CA or TDMA modes. Some operating scenarios for rate-sensitive applications arise when one considers wireless video surveillance and target detection applications for wireless sensor networks. To support such rate-sensitive applications in wireless sensor networks, we present a Multirate-based Service Differentiation (MRSD) based on unslotted CSMA/CA. Unlike existing

more »

... y-based service differentiation models, the MRSD defines independent virtual MACs, each of which consists of Adaptive Backoff Window Control (ABWC) and Virtual Collision Avoidance (VCA) algorithms. The ABWC dynamically adjusts the backoff window to reflect the local network state in the local collision domain. The VCA prevents virtual collisions and preempts packets with the minimal utility in the virtual collision domain. By analyzing these algorithms, we prove that the ABWC enables the achieved transmission rate to converge to the rate requirement and the VCA produces a virtual collision-free schedule to avoid degradation of the achieved transmission rate. Through the simulation, we validate our analysis and show the MRSD outperforms existing algorithms in terms of convergence to the rate requirement.