Esp-Wifi-Mesh Concepts - Espressif ESP32-S2 Programming Manual

Chapter 4. API Guides
ESP-WIFI-MESH differs from traditional infrastructure Wi-Fi networks in that nodes are not required to connect to
a central node. Instead, nodes are permitted to connect with neighboring nodes. Nodes are mutually responsible for
relaying each others transmissions. This allows an ESP-WIFI-MESH network to have much greater coverage area as
nodes can still achieve interconnectivity without needing to be in range of the central node. Likewise, ESP-WIFI-
MESH is also less susceptible to overloading as the number of nodes permitted on the network is no longer limited
by a single central node.

4.8.3 ESP-WIFI-MESH Concepts

Terminology
Term
Node
Root Node
Child Node
Parent Node
Descendant Node
Sibling Nodes
Connection
Upstream Connection
Downstream Connection
Wireless Hop
Subnetwork
MAC Address
DS
Tree Topology
ESP-WIFI-MESH is built atop the infrastructure Wi-Fi protocol and can be thought of as a networking protocol that
combines many individual Wi-Fi networks into a single WLAN. In Wi-Fi, stations are limited to a single connection
with an AP (upstream connection) at any time, whilst an AP can be simultaneously connected to multiple stations
(downstream connections). However ESP-WIFI-MESH allows nodes to simultaneously act as a station and an AP.
Therefore a node in ESP-WIFI-MESH can have multiple downstream connections using its softAP interface,
whilst simultaneously having a single upstream connection using its station interface. This naturally results in a
tree network topology with a parent-child hierarchy consisting of multiple layers.
ESP-WIFI-MESH is a multiple hop (multi-hop) network meaning nodes can transmit packets to other nodes in the
network through one or more wireless hops. Therefore, nodes in ESP-WIFI-MESH not only transmit their own
packets, but simultaneously serve as relays for other nodes. Provided that a path exists between any two nodes
on the physical layer (via one or more wireless hops), any pair of nodes within an ESP-WIFI-MESH network can
communicate.
Note: The size (total number of nodes) in an ESP-WIFI-MESH network is dependent on the maximum number of
layers permitted in the network, and the maximum number of downstream connections each node can have. Both of
Espressif Systems
Description
Any device that is or can be part of an ESP-WIFI-MESH network
The top node in the network
A node X is a child node when it is connected to another node Y where the connection
makes node X more distant from the root node than node Y (in terms of number of
connections).
The converse notion of a child node
Any node reachable by repeated proceeding from parent to child
Nodes that share the same parent node
A traditional Wi-Fi association between an AP and a station. A node in ESP-WIFI-
MESH will use its station interface to associate with the softAP interface of another
node, thus forming a connection. The connection process includes the authentication
and association processes in Wi-Fi.
The connection from a node to its parent node
The connection from a node to one of its child nodes
The portion of the path between source and destination nodes that corresponds to a
single wireless connection. A data packet that traverses a single connection is known
as single-hop whereas traversing multiple connections is known as multi-hop.
A subnetwork is subdivision of an ESP-WIFI-MESH network which consists of a
node and all of its descendant nodes. Therefore the subnetwork of the root node
consists of all nodes in an ESP-WIFI-MESH network.
Media Access Control Address used to uniquely identify each node or router within
an ESP-WIFI-MESH network.
Distribution System (External IP Network)
1308
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