Cooperative transmissions emulating multi-antenna systems may help reduce the total energy consumption in wireless networks. In this book, we define a virtual Multiple-Input Single-Output (vMISO) link to be established when a group of transmitters jointly enable space-time communications with a single receiver. We present a novel approach in characterizing the optimal multi-hop vMISO routing in ad hoc networks. The key advantages of vMISO links are the increase in transmission range and the decrease in the required transmission energy due to diversity gain. Specifically, we solve a nonlinear program that minimizes the total energy cost of reliable end-to-end transmissions by selecting the optimal cooperation set. Our results indicate that a multi-hop vMISO system is energy efficient only when a few nodes cooperate at each hop. We design a new greedy geographical vMISO routing protocol. Also, we formulate the network lifetime maximization with vMISO routing as a nonlinear program. Then, we present a novel cooperation set selection and flow augmentation based routing heuristic that can significantly increase the network lifetime compared to Single-Input Single-Output systems.