Wireless Sensor Networks (WSNs) are used in variety of fields which includes military, healthcare, environmental,
biological, home and other commercial applications. The adoption of WSNs by specific applications that require
complex operations, ranging from health care to industrial monitoring, has brought forward a new challenge of
fulfilling the quality of service (QoS) requirements of these applications. However, providing QoS support is a
challenging issue due to highly resource constrained nature of sensor nodes, unreliable wireless links,dynamic
network topology and distributed architecture. We explore QoS challenges and perspectives for Wireless Sensor
Networks, compare the current QoS research issues and classify the state of the art QoS-aware protocols to
understand the properties and limitations of existing protocols
