In embedded systems operated by battery and interacting with the environment, a fundamental issue is the enforcement of real-Time and energy constraints to guarantee a desired lifetime with a given performance. A lot of research has focused on energy management at the communication level; however, not many authors considered both real-Time and energy requirements in wireless communication systems. This article proposes El-SMan, a power-Aware framework working in combination withMAC layer communication protocols for maximizing battery lifetime in wireless networks of embedded systems with real-Time constraints. Exploiting the flexibility in bandwidth requirements, El-SMan adapts stream parameters to balance performance versus energy consumption, taking both lifetime and message deadlines into account.