# Towards an Efficient Method for Large-Scale Wi-SUN-Enabled AMI Network Planning
## 2 Smart Grid Network Architecture
### General Network Architecture  
This study considers the use of the Wi-SUN (Wireless Smart Utility Network) wireless communication standard (Wi-SUN Alliance(r) [8]). The Wi-SUN standard implements a mesh network architecture based on the IEEE 802.15.4g standard [9], using RPL (IPv6 Routing Protocol for Low Power and Lossy Networks, RFC6550) [10] as a routing protocol at the network layer. The mesh network allows multihop communication between meters, routers, and gateways.  
The network planning involves many elements, including smart meters, gateways, routers, poles, and backhaul network components, and it can be classified as an NP-hard problem [11]. Additionally, a set of constraints is associated with the network design, such as ensuring maximum throughput with the lowest possible latency at a reduced cost. The network performance is highly dependent on the placement of key elements for the communication process between the neighborhood area network (NAN) region of the smart grid, the gateways, and the wide-area network (WAN) region, where the CC is installed.  
Figure 1a presents an example of a smart grid scenario. Wireless communication between the elements of the NAN region takes place according to the messaging protocol used by the network. In this study, we consider using the RPL protocol, which allows the existence of different routes intending to minimize the points of failure using alternative parent nodes (backup nodes) for forwarding messages. Analyzing from the point of view of each meter, different communication options are possible, either by connecting the meter directly to a gateway, a router, or even using multihop forwarding messages through other meters.  
The smart meters, routers, gateways, and DA devices are in the NAN region. DA devices include voltage regulators, and automatic reclosers, among other equipment. All these elements must be connected to ensure communication with the backhaul network, which connects the main communication elements and establishes a reliable two-way access channel from NAN to the CC of the smart grid.  
In a typical smart grid scenario, the correct positioning of communication key elements, such as gateways and routers, assures communication between a large number of SMs and the CC and between the CC and DA devices. In addition, it is essential to highlight that, usually, these elements (smart meters and DAs) are dispersed over a large geographic area, introducing complexity to the positioning planning.  
In practice, gateways and routers are installed on poles. The installation is usually done in areas with a high concentration of meters and equipment to be connected. A set of candidate positions can be established from the set of poles. For the AMI planning and key devices positioning, special preference must be given to the use of poles hosting DAs, as they are usually already installed in the region and because of their importance in the electrical infrastructure. In some cases, the DAs may already be interconnected via fiber optic cable, thus reinforcing the use of these resources on a preferential basis.