The book presents a first systematic approach for the cross layer design in wireless sensor networks, where the optimizations for energy efficiency and application QoS are required. A reference model of the network architecture, Embedded Wireless Interconnect, is firstly concluded from the presented studies, as a potential standardized way of the cross layer design in wireless sensor networks. This architecture is also later extended to large-scale cognitive wireless networks beyond pure wireless sensor networks. `The research in wireless sensor networks is boosted by the embedded system hardware advances and a broad range of potential applications. Wireless offers flexibility. The wirelessly interconnected sensor nodes can revolute our perception of the physical world and ourselves, and closely bound the physical world with the cyber-world. We believe our research is on the right track for harmonizing the relationship between human being and the planet that we are living on. The prosperity of embedded wireless sensor networks can also be the next major innovation in the IT industry after Personal Computers (PC) and the Internet.` - from the text.