Mesh Over IEEE 802.11 for 2.4 GHz Wi-Fi Radio

Abstract

Wi-Fi network has one AP and limited STAs which are connected with AP. To form a large network, number of APs are required. There is the wired connection between these APs. So, this network is not pure Wireless network. This problem is solved if these APs are Wi-Fi mesh nodes. Multi-hopping mechanism of mesh network increases range and size of the network. ESP32 is a Wi-Fi module, which has the functionality to operate AP and STA mode simultaneously(AP-STA mode). Using this functionality, two APs can communicate with each other. So, the multi-hopping mechanism can be achieved. The default behavior of STA is to connect with AP which has strongest RSSI value. This default behavior causing some issue to form the pure mesh network. To resolve this case need to change connection behavior. This thesis explains connection policy which has been customized. Here STA chooses AP which is more suitable for Mesh Network even though its RSSI is not strongest one. ESP32 IDF is OS based FreeRTOS, major programming is done in C language. The ESP-NOW protocol is used to do communication with other nodes without establishing the connection. To set configuration before establishing a connection need to exchange data between other nodes, this protocol makes it possible. So, here basic connection configuration can be set at runtime instead of compile time. This functionality is achieved through Node Discovery process. ESP32 IDF provides Wi-Fi stack in MAC and PHY libraries, on which any other network layer can be ported. Here network module is LWIP, which has been removed to port another higher layer based on requirement. Like this IDF is customized to implement Wi-Fi mesh network.