User's Manual

8
SMARTMESH NETWORK OVERVIEW
A SmartMesh network consists of a self-forming multi-hop mesh of nodes, known as motes, which
collect and relay data, and a network manager that monitors and manages network performance and
security, and exchanges data with a host application.
SmartMesh networks communicate using a time slotted channel hopping (TSCH) link layer, pioneered by
Dust Networks. In a TSCH network, all motes in the network are synchronized to within less than a
millisecond. Time in the network is organized into time slots, which enables collision-free packet
exchange and per-transmission channel-hopping. In a SmartMesh network, every device has one or
more parents (e.g. mote 3 has motes 1 and 2 as parents) that provide redundant paths to overcome
communications interruption due to interference, physical obstruction or multi-path fading. If a packet
transmission fails on one path, the next retransmission may try on a different path and different RF
channel.
A network begins to form when the network manager instructs its on-board Access Point (AP) radio to
begin sending advertisements—packets that contain information that enables a device to synchronize to
the network and request to join. This message exchange is part of the security handshake that
establishes encrypted communications between the manager or application, and mote. Once motes
have joined the network, they maintain synchronization through time corrections when a packet is
acknowledged.
Figure 1. Mesh Network
An ongoing discovery process ensures that the network continually discovers new paths as the RF
conditions change. In addition, each mote in the network tracks performance statistics (e.g. quality of
used paths, and lists of potential paths) and periodically sends that information to the network manager
in packets called health reports.