# Heterogeneous Wireless Networks for Smart Grid Distribution Systems: Advantages and Limitations
## 2 Related Works  
Currently, many researchers are investigating employing wireless communication in various smart grid applications due to its easy deployment, low cost, and high supported data rates [10; 11]. In [8], the author presents the design of sensor/data acquisition nodes that can be equipped with wireless transceivers in the system implementation of a predictive diagnosis scheme for safety-critical applications. Moreover, the authors in [3] discuss the need for the existence of sensor/control nodes with wireless capabilities that can be integrated into a building management system without disruptive changes to building controls. Indeed, the implementation of smart grid functions (such as predictive diagnosis for safety-critical applications [8], self-healing [12] or real-time system state estimation) at the distribution level mandates the exchange of a large data volume within a short period of time. This comes as a direct consequence of the very large number of distribution substations and/or monitored entities. Therefore, the underlying communication network needs to be highly reliable and fast. Due to the broadcast nature of wireless communications, identifying smart grid security vulnerabilities, attacks, and the mitigation of them are under focus of a multitude of research works as in [13] and the references therein. In addition, the authors in [14] present a comprehensive discussion and some proposed solutions to implement wirelessly-connected secure sensor/control nodes for a home area network, which represents an essential element in building smart power grids. Few research works address the proposal of supporting the distribution level of power grids with advanced communication capabilities. [PERSON] et al. [15] propose a satellite-based communication network to allow the exchange of control information among the 11 kV distribution substations in a single hop fashion. This infrastructure is nominally expensive, although the bandwidth is limited to only 9.6 kbps, which leads to a large latency. The author in [16] proposes a multihop wireless network with cellular frequency reuse as the communication infrastructure for low voltage distribution networks but without considering the reliability of data packet delivery. [PERSON] et al. [17] study the ability of employing hybrid communication technologies (such as WiFi, Zigbee, cellular, and power line carrier) to carry various data types with different quality-of-service (QoS) requirements in a microgrid. The authors proposed a multi-tier heterogeneous network to direct data packets to the most appropriate communication technology for their QoS requirements. However, each tier runs only one communication technology. [PERSON] [18] also studies the possibility of improving the QoS of grid data packets delivery. For this, a two-tier communication network combining the IEEE 802.15.4g standard and wired communication is proposed. This architecture, however, does not harness the capabilities of HWNs as it depends on disseminating sensed data wirelessly in the first tier by using only single-interface IEEE 802.15.4g-based devices. Per packet end-to-end reliability is realized at the transport layer by the TCP protocol. In addition to congestion and flow control mechanisms, TCP also provides end-to-end error-free packet delivery. These TCP schemes are vital for the efficient utilization of bandwidth and prevention of packet loss [19]. In fact, network congestion causes deviations in phasor measurement units (PMUs) and IEDs' real-time traffic, whose timeliness is essential in detecting and mitigating faults. Even with path bandwidthreservation, traffic congestion can still occur at times of increasing traffic demand and in transient traffic stress situations [20; 21]. A proxy-like TCP mechanism is introduced in [22] as a solution to the TCP scalability concerns given the large number of data sources in a smart grid.