Event detection is a function common to many wireless sensor network (WSN) applications, e.g. intruder detection in surveillance networks, presence of people detection in building energy management applications, and crack detection in strain sensor networks. Cost of deployment and maintenance is considered by many to be the reason why WSN technology is not more widespread. While hierarchical or single-hop network architectures are attractive from a communication performance point of view, their required highly functional and long-transmission-range nodes are prohibitively expensive in large-area applications. This leaves multi-hop WSNs as the only possibility for large-area, cost-constrained WSN applications. However, multi-hop WSNs are still limited in terms of battery life. While ambient energy harvesting and rechargeable storage elements extend WSN lifetime, these technologies add to the cost of the network. Therefore, the demand still exists for extremely low-cost sensors that can run on low-cost non-rechargeable batteries. In this project, we investigate new routing and medium access control (MAC) protocols to optimize the lifetime of a WSN that does event detection, while taking advantage of a new cooperative transmission (CT) range-extension forwarding strategy. CT is a technique wherein one or more radios assist another radio, in the physical (PHY) layer (i.e. the radios form a ?virtual transmit array?), to transmit a single message. In the context of multi-hop WSNs, CT range extension becomes a very promising energy balancing mechanism. This project defines realistic energy consumption models and optimizes MAC and routing metrics that are specifically tied to event detection quality and WSN lifetime, assuming CT range extension is available, along with other life-extension strategies, such as such as in-network filtering, sleep scheduling, energy-aware routing, and non-uniform node deployment.