dd-wiki

• end devices
• Gateways
• lorawan network server
• applications

lora is the physical layer ultra low power consumption long range - small bandwidth lorawan mac media access control

devicese usually are asleep

only enable wifi when it needs to send a lot of information

frequency on a free spectrum for example:

eu 863 to 870 mhz, 433 to 434 mhz
china 779 to 787
us 902 to 928
australia 915 to 928
+ many others

modulation: chirp spectrum modulation

super robust on interference because ti change modulation, differently from narrowband

differences between end devices and a gateway is that the gateway can listen on multiple frequency at the same time

uplink from device to gateway

downlink from gateway to device

number of databit per second: the symbols that are modulated per time units the higher is the spreading factor, the slower is the communication

lower SF → Shorter range → less time on air → lower energy consumption → higher data rate

minute 13:00 2 lorawan fundamentals

=====what is lorawan=====lora lorawan is a protocol based on

example of frequency plan in usa

US915 is from 902 to 928 Mhz

fixed number of channels; for uplink on perspective of end device

• 64 channels of 125khz BW
• 8 channels of 500khz BW

for downlink

• 8 channles of 500khz BW (to end devices)

Class A:

• implemented by all end devices
• end devices start transmissions
• for example: every devices at any time can send an hearthbeat like : hey i'm here and my battery life is…

class B:

• transmission initiated by the end deice or o- n fixed interval - by network

beaconing - segnalazione - sent by network at fixed interval through the gateway

for example my end device wake up every 2 minutes to check if network want to start a downlink or not. 

class C:

• transmission initiated by the network at any time

continuos downlink: end devices continue to check if network wants to send a message to the end device

it can be an end devices connected to electrical source, like street light

handlinkg downlink based on different class:

• limited payload 51-241 bytes depending on data rate (they send json)
• low data rates - max 5.5kbps on 125khz
• region specific rules
  1. EU duty cycle restrictions
  2. US dwell time restrictions
• asynchronous communications - more uplink then downlink capacity

physical layer doesn't provide security mechanisms it only has an optional crc field that helps detecting transmission errors

lorawan provides security with the 3 pillars of security:

• Authenticity - every device are authenticate
• Integrity - no intermediate can modify the message
• Confidentiality - on the application layer we can encrypt the data so nobody can understand the payload

two layer security with aes encryption algorithm

• 128-bit network session key - authentication, integrity
• 128-bit for application session key - confidentiality

network sessions:

• device address devaddr
• network session key nwkskey
• frame counters fcntup fcntdown
• mac state - channels, data rate, etc

application session - between end device and application server

• application session key appskey
• frame counters fcntup fcntdown

during a lorawan session:

• session keys remain the same
• frame counters are incremented and never reused

a session can be

• dynamically established joining a network OTAA over the air activation
• hardcoded (apb activation by personalization)

devaddr and security keys are hardcoded into device