Abstract— The Quality of Service (QoS) in smart grid communications especially in monitoring smart grid assets is becoming significantly important for emerging smart grid applications. Wireless Sensor Networks (WSNs) are expected to be widely utilized in a broad range of smart grid applications due to their numerous advantages along with their successful adoption in various critical areas including military and health. WSNs protocols are not designed to provide QoS provisioning for monitoring applications. Thus, the use of WSNs in transmitting delay-critical data from smart grid assets calls for data prioritization and delay-mitigation schemes. In this paper, we propose a delay-responsive, cross layer scheme with linear backoff (LDRX) mechanism to address delay and service requirements of the smart grid monitoring applications. The LDRX scheme is designed to operate in cluster-tree WSN topology that is suitable for monitoring wide areas such as electrical substations or large installations. We show that LDRX has greater impact on delay reduction compared to previously proposed WSNs delay reduction schemes. Index Terms— QoS, medium access control, smart grid, wireless sensor networks, cluster-tree topology, monitoring applications. I. INTRODUCTION Wireless sensor networks (WSNs) are considered as potential tools for monitoring and controlling the smart grid. WSN comprises of a large number of low-power, low-cost and small size sensor nodes. Sensor nodes communicate wirelessly over short distances. One of the major applications of sensor nodes is to collect different types of data, e.g. voltage, temperature, vibration and etc. WSNs are favored for monitoring applications because they are able to operate in harsh environmental conditions, a very low fault tolerance, extremely low power consumption, self-configuration. In environments where high voltages are in use, WSN can also provide necessary insulation. Despite the advantages of WSNs, they have not been utilized extensively for monitoring smart grid assets. This is mostly due to the inherent limitations of WSNs in real-time data delivery. This is due to the fact that WSNs utilize low power communication links in high node density. The abovementioned challenges raise reliability concerns in the smart grid. In fact, reliable data delivery has been widely studied in the WSN literature where the term “reliable” generally refers to ensuring data is delivered from source to destination or sink. In the smart grid, asset monitoring and control varies in importance and criticality, for instance monitoring the temperature of an oil filled transformer is considered neither delay critical nor the packet delivery ratio needs to be 100% all of the times. This is because the instance of temperature monitoring is a continuous process and does no quickly vary with time. On the other hand, transformer partial discharge (PD) monitoring is a highly delay critical monitoring application and the data needs to be transmitted in near real time fashion with highest reliability values. The need for near real time transformer PD monitoring arises in situations where the operator need to analyze all the PD peaks as they happen and without loss of any important data. The significance of predictable reliability, timeliness and Quality of Service (QoS) in smart grid communications has been also outlined in the recent studies [1]. In addition, it is well-known that protocols designed in an application-specific manner improve the performance of the WSN [2-3]. For this reason, we focus on the use of WSNs in the smart grid domain and aim to improve their performance in terms of delay and QoS. In this paper, we propose a delay-responsive, cross layer scheme with linear back-off (LDRX) mechanism to address delay and service requirements of the smart grid monitoring applications. The LDRX scheme is designed to operate in cluster-tree WSN topology that is suitable for monitoring large smart grid assets such as electrical substations or large installations. We propose to implement the LDRX scheme in a WSN with cluster-tree topology to monitor an electrical substation, as shown in Fig. 1 [4]. The proposed scheme can easily be extended to cluster-tree topologies with any size and depth. We show that LDRX has greater impact on delay reduction compared to previously proposed WSNs delay reduction schemes. Fig.1 WSN-based substation monitoring. A Delay Mitigation Scheme for WSN-based Smart Grid Substation Monitoring Irfan Al-Anbagi, Melike Erol-Kantarci, Hussein T. Mouftah School of Electrical Engineering and Computer Science University of Ottawa, Ottawa, ON, Canada ialan055@uottawa.ca, melike.erolkantarci@uottawa.ca, mouftah@uottawa.ca