# Efficient Cluster Tree Topology Operation and Routing for IEEE 802.15.4-Based Smart Grid Networks
## 3 Related Works  
The use of WSNs in general monitoring applications has been discussed widely in the literature [21; 22; 23; 24]. However, only a few publications apply WSNs to smart grid monitoring applications, where the traffic intensity is high and the time delay is a critical issue. For example, the provision of QoS for smart grid monitoring applications was studied in [24; 25; 26; 27]. In [12], the authors proposed the addition of QoS to IEEE 802.15.4, which provides differentiated services for traffic with different priorities in the MAC layer. In [25], the authors proposed modifying the clear channel assessment (CCA) performed by the sensor node to provide service differentiation for high-priority traffic. In [27], the authors presented an adaptive QoS scheme for WSNs to provide service differentiation and reduce the latency of critical data in smart grid applications. In [21], the authors proposed an algorithm for adaptively assigning a single GTS to nodes with important data. However, a single GTS may not be sufficient to reduce delays in smart-grid monitoring applications with high traffic intensity. In [28; 29; 30; 31], the authors discussed channel access techniques for multi-hop WSNs. These studies discussed the scheduling of cluster-tree topologies. Most of this work assumes that all the sensor nodes in the network use one-channel access technology to improve network performance. In [31], the authors proposed a multi-channel cluster tree algorithm to prevent beacon frame collisions and GTS collisions between multiple clusters. When the traffic is concentrated, these tree topology algorithms cause bottlenecks in the root and adjacent nodes and increase the latency. In addition, there is a disadvantage in that the routing path is prolonged when nodes at a distance from the root node transmit data between these. The use of WSNs to support QoS for smart-grid applications has been studied. For example, a method for using WSNs for monitoring purposes in smart-grid applications was studied in [1; 32; 33]. The challenges and opportunities of using WSNs in smart grid applications have been discussed extensively in [1]. In [32], the authors applied wireless multimedia sensors for monitoring purposes in smart-grid environments. The use of WSNs to reduce and control household electricity consumption was proposed in [33; 34]. The authors of [34] proposed a time-of-use (TOU) recognition energy management scheme to reduce the peak load of smart-grid applications based on WSN. The performance of WSNs in smart grid environments has been described in detail in several studies. For example, the authors in [35] studied various efficient routing schemes of WSNs to provide QoS in smart grid applications. The authors discussed potential areas in which WSNs could be deployed for efficient operational monitoring and control of smart grid applications such as electric transport, distributed energy resources, and storage. In [36], the authors proposed a fiber-wireless sensor network (Fi-WSN) gateway that can prioritize packets in smart grid environments and support QoS for fibre-to-x (FTTX) users. In [37], the authors proposed an adaptive QoS (AQoS) scheme and adaptive guaranteed time-slot (AGTS) allocation scheme for IEEE 802.15.4-based WSNs used in high-traffic intensive smart-grid monitoring applications. In addition, cross-layer protocols for WSNs have been studied. In [38], the authors proposed the cross-layer protocol (XLP) for efficient communication in WSNs. It provides media access, routing, and congestion control. The authors studied the throughput, latency, Goodfoot, and routing failure rates of the XLP for existing cross-layer protocols in WSNs. The authors of [39] also developed an XLP protocol that combines the physical, MAC, routing, and transport layer functions into an integrated communication framework. The XLP was compared with current state-of-the-art cross-layer protocols for WSNs.