  Wireless Sensor Networks (WSNs) emerge as underlying infrastructures for new
classes of large scale net- worked embedded systems. However, WSNs system
designers must fulfill the Quality-of-Service (QoS) requirements imposed by the
applications (and users). Very harsh and dynamic physical environments and
extremely limited energy/computing/memory/communication node resources are
major obstacles for satisfying QoS metrics such as reliability, timeliness and
system lifetime. The limited communication range of WSN nodes, link asymmetry
and the characteristics of the physical environment lead to a major source of
QoS degradation in WSNs. This paper proposes a Link Reliability based Two-Hop
Routing protocol for wireless Sensor Networks (WSNs). The protocol achieves to
reduce packet deadline miss ratio while consid- ering link reliability, two-hop
velocity and power efficiency and utilizes memory and computational effective
methods for estimating the link metrics. Numerical results provide insights
that the protocol has a lower packet deadline miss ratio and longer sensor
network lifetime. The results show that the proposed protocol is a feasible
solution to the QoS routing problem in wireless sensor networks that support
real-time applications.
