—Sensor networks have been investigated in many scenarios and a good number of protocols have been developed. With the standardization of the IEEE 802.15.4 protocol, sensor networks became also an interesting topic in industrial automation. Here, the main focus is on real-time capabilities and reliability. We analyzed the IEEE 802.15.4 standard both in a simulation environment and analytically to figure out to which degree the standard fulfills these specific requirements. Our results can be used for planning and deploying IEEE 802.15.4 based sensor networks with specific performance demands. Furthermore, we clearly identified specific protocol limitations that prevent its applicability for delay bounded realtime applications. We therefore propose some protocol modifications that enable real-time operation based on standard IEEE 802.15.4 compliant sensor hardware.