Abstract: Due to the characteristics of wireless mesh network (WMN) in terms of topology, transmission link and traffic, the conventional layered protocol designmethods forwired networks can notguarantee the QoS performance forWMN. To reach a tradeoff between the efficiency of radio resources andQoS requirements tomultimedia traffic, it is required to explore the new designmethod forWMN based on physical layer, MAC layer, routing layer, etc. A unified cross-layermanager forall the layers is a necessity tomonitor the transmission performances or requirements, thereby to controlor adjust the relevant algorithms dynamically. The protocol and algorithm in respective layers are optimized by sharing the information on theQoS requirements to higher layers and the network states in lower layers, and multiple protocols in relevant layers are co-designed and co-optimized after the targets to be cross-layer designed are reasonably chosen. The generalprinciples andmethods of cross- layer design from physica,l MAC and routing layers toTCP layerwere presented respectively, and the theory and key technologies to be deeply researched were outlined, including the design of adaptive rate control and energy-savingmechanism, QoS-basedMAC protocol and routing protocol.