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Andrea Finardi Iot simulations with Cisco Packet TracerBog'liq 2.3 (3)2.3.1 LoRaWAN Overview
LoRaWAN is a technology created by the non-profit, multi-vendor LoRa Alliance
TM
[10],
and relies in a star-of-star infrastructure where many devices are connected with a single
hop to a receiver gateway, that then relays the messages via traditional IP networks to
the central backend servers.
Figure 1 - LoRaWAN Infrastructure
LoRaWAN offers bi-directional connectivity over multi-kilometres range and with bitrate
between 0.3 kbps to 50 kbps. Even if communication is bi-directional the uplink traffic,
from device to network, is preferred. [11]
LoRaWAN allows three classes (A, B and C) of transmitting devices based on throughput
and power needs of the IoT devices [12] [13] [14].
A class devices are low-power devices that require bi-directional communication and rely
on an ALOHA (Additive Links On-line Hawaii Area) type of protocol. Uplink and downlink
communications are in fact asynchronous and communication is triggered by the IoT
device sending a frame to the uplink channel and then listening for an answer, for few
seconds, in the next two downlink windows. Once uplink communication is acknowl-
edged by the gateway the downlink traffic can start. As the communication is triggered
14
by the device and does not require any other periodical transmission, this allows the
device to be in a constant sleep mode, saving batteries, and communicating only when
necessary.
B class devices are designed for applications where additional downlink is required. A
periodical beacon message is in fact sent by the gateway to the IoT device to schedule
additional downlink windows without the need to previous successful uplink communica-
tions. Device battery lifetime is impacted due to the receiving of the additional synchro-
nization messages.
Class C communications ensure a low-latency communication as, as opposite of class
A devices, class C devices are always listening for downlink traffic. Gateway is able to
know the status of the device and start the sending data to the device at any time.
Battery optimization in such cases is achieved by switching the device from class A to
class C when necessary.
Apart from the downlink limitation for the lower class devices the LoRaWAN biggest per-
formance issue is due to the duty-cycle limitation imposed in the ISM bands regulation.
[15] Typically the regulations, for instance in Europe [16], dictates that only 1% of the
time the device is allowed to transmit in each sub-band. This limits the traffic for each
device but also add extra complexity to the network when big amount of device are con-
nected to the same network.
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