Great introduction to LoRaWAN by Andreas Spiess: LoRaWAN De-Mystified
LoRa is a Low Power Wide Area Network (LPWAN).
- Network - Multiple devices communicating between each other
- Wide Area - Longer range than WiFi (and less power) and much longer range than Bluetooth
- Low Power - Comes at cost of bandwidth
Not a replacement for wifi. Great for low bandwidth sensor networks.
Link Budget: Measured in dB.
- Sender can have Amplifier.
- Receiver can use optmized antenna for additional Antenna Gain.
Regional "free band" frequences
- 868 MHz for Europe - only 25mW allowed power restriction for output broadcast
- 915 MHz for US -
- 433 MHz for Asia -
Data rates, in Europoe, can range between: 250bps - 50kbps
LoRaWAN is a distributed network of gateways. Many devices connect to one gateway, many gateways connect to broker infrastructure, many clients connect to the brokers.
Capacity:
- 8 parallel channels == 8 devices
- 50% duty cycle per device = 16 devices
- 1% duty cycle per cycle = 800 devices (for one gateway) -- this is the rule - each device is only allowed 1% duty cycle
- 250 bits per second / 100 = 2.5 bps
LoRa uses same channel for both ways (to/from) traffic which further limits bandwidth.
Andreas's Summary:
- LoRa is a new transmission standard between distributed devices and distributed gateways
- Extermely low channel capacity, a very low power consumption, and therefore a very high link budget.
- Ideal for low power sensors distributed everywhere, also far from the next gateway
- Two different approaches for the network: A comemrcial and a community approach
- The community approach is based on pricatedly built and operated gateways and an infrastructure whtich transfers the messages from the gateway to your application
- build sensor node - churp churp
- Build a gateway and join thethingsnetwork.org.
DIY things:
- RAK7243 Gateway Upgrade Raspberry Pi amazon link
- RAK7243 Gateway for RPi with Cell amazon link
- Alan note: One thing on your cellular version. I see that the cell modem is based on the Quectel BG96/EG95 . I looked at the specs on the EG95, and it looks like it needs to be an EG95-NA or EG95-NAX in order to support Band 4, which is GCI's LTE band. I'm not sure what ATT's LTE band is. From the Amazon link, I'm not sure what model of the EG95 or BG95 they are shipping.
Easy Button things (used by Alan):
- Laird RG191 ($250)
- Alan note: The Laird gateway has been fairly rock solid. I have an external antenna about 35' off the ground. I've done 10 mile links. Most of the links shown on https://ttnmapper.org/ are from my drive-around link testing.
- Things Indoor Gateway, now available through Adafruit ($85)
- Alan note: put it through some abuse by disconnecting the WiFi router and reconnecting, and the gateway does seem to reconnect automatically. Only has WiFi backhaul, and no external LoRa antenna, although people on the Things forum show you how to hack the case and install an external antenna connector.
Antenna notes: Alan has done some antenna testing:
Built four of these 1/4 wave ground plane antenna's: https://www.thethingsnetwork.org/labs/story/simple-homemade-outdoor-868mhz-antenna-groundplane and they work very well relative to a number of commercial whips and dipoles tested.