:
A wireless sensor network is a collection of a large number of sensors nodes densely deployed.
Sensor nodes are used to sense environmental data and collect information at a central place.
Sensors have been a regular part in our daily life, they can be very much used in isolation to solve
many problems like in car, ac, and to measure temperature, sound, pollution levels, humidity, wind
speed direction and pressure. They can be used in isolation. But the important focus is on some crucial
applications where human life is associated, environmental is associated for example the
battlefields, earth quick monitoring, flood monitoring, weather forecasting etc. These are some of the
biggest applications which need the invention of sensor nodes rather than manual human forces. Here
sensor nodes cannot work in isolation because one sensor cannot gather appropriate data. Therefore,
it is needed to deploy a large number of sensor nodes, which can exchange data through some communication
strategy or protocol, and thereafter the data should be maintained to a common place
where some action should be taken. For providing efficient applications among these sensor nodes,
an efficient routing protocol or algorithm needs which could provide the QoS to the end user. Most
of the routing protocols for WSNs are designed without explicitly considering the Quality of Service
(QoS) of the generated routes. It has been observed that such routing protocols are inadequate at the
time of data delivery route which requires guaranteed QoS. QoS routing requires discovering a route
from source to destination to fulfill the QoS necessities. QoS is more complicated to assurance in
sensor network due to dynamic topology and energy constraints. In this paper, recent issues and challenges
have been considered in terms of research gap yet, QoS routing approaches have been deliberated,
distribution of literature over recent years and QoS parameters distribution over recent years
have been exposed, which are valuable for researchers for further investigation.
