This book deals with the under-utilization problem of medium access control in wireless collision channels and other closely related problems known in wireless networks. In particular, it deals with the design of random access protocols for wireless systems and provides a mathematical framework for performance evaluation of multihop- based heterogeneous wireless networks. A new modeling framework is also introduced for the analytical study of MAC protocols operating in multihop wireless ad hoc networks, i.e., wireless networks characterized by the lack of any pre- existent infrastructure and where participating devices must cooperatively provide the basic functionalities that are common to any computer network. To show the applicability of our modeling framework, we model wireless ad hoc networks that operate according to the IEEE 802.11 standard. To accomplish this, we present a comprehensive analytical modeling of the IEEE 802.11 and the derivation of many performance metrics of interest, such as delay, throughput, and energy consumption.