The e-SENSE project has the vision to enable new context-aware applications and services in beyond 3G mobile communication systems by providing the technology required to capture the context surrounding the service users and service-related objects through wireless sensor networks. This paper introduces a flexible protocol stack architecture for wireless sensor networks, which allows the incorporation of novel connectivity, management, and middleware concepts into the e-SENSE system, and thus provides advanced support functionality and high adaptability required for a wide range of application and deployment scenarios.