In Wireless Sensor Network (WSN), nodes are limited in mobility, energy resources, computational capacity and memory. When these extreme limitations are combined with strict traditional architecture, both the network performance and lifetime are compromised by consuming more amount of energy. Network lifetime is the fundamental concern of WSN due to the fact that each node in network operates with extremely limited energy. Recent research has shown that the Open System Interconnection (OSI) model is not necessarily the correct approach for WSN. Researchers have made modifications to communication protocols which violate the OSI model, but achieve specific optimization goals. These modifications are termed as Cross-Layer Design (CLD). CLD allows direct communication between protocols at nonadjacent layers or sharing variables between layers. This paper presents a detailed investigation of CLD and discusses different cross-layer proposals given by researchers.

A Wireless Sensor Network (WSN) consists of spatially distributed autonomous sensors to monitor physical or environmental conditions such as temperature, sound, vibration, pressure, motion or pollutants and to cooperatively pass their data through the network to a main location. The modern networks are bidirectional mostly, also enabling control of sensor activity. The development of WSN was motivated by military applications such as battlefield surveillance; today such networks are used in many industrial and consumer applications such as industrial process monitoring and control, machine health monitoring and so on.

A WSN is a collection of sensor nodes interconnected by wireless communication channels. Each sensor node is a small device that can collect data from its surrounding area, carry out simple computations and communicate with other sensors or with the Base Station (BS). Such networks have been realized due to recent advances in micro electromechanical systems and are expected to be widely used for applications such as environment monitoring, home security and earthquake warning.

Telecommunications Journal, Cross-Layer Designs (CLDs), Quality of Service (QoS), Cross-Layer Design (CLD), Wireless Sensor Network (WSN).