Cooperative wireless communications: A cross-layer approach

"Denise and her husband Mitch are at opposite ends of a living room at a crowded party. Denise tries to attract Mitch's attention and shouts something at him. All Mitch can hear is the word 'Let's.' Celine, in the middle of the room, who overhears Denise and notices their predicament, repeats to Mitch the part she hears: 'Go home.' This time, all Mitch hears is the word 'home.' Mitch finally figures out that his wife wants to go home." This analogy from everyday life vividly portrays the essential element of cooperative wireless communications, namely, utilizing information over-heard by neighboring nodes to provide robust communication between a source and its destination. Cooperative communication exhibits various forms at different protocol layers and introduces many opportunities for cross-layer design and optimization, some of which will be explored in detail in this article.