When it comes to capacity, a LoRaWAN network can support millions of messages. However, the number
of messages supported in any given deployment depends upon the number of gateways that are installed.
A single eight-channel gateway can support up to 1.5M messages over the course of a 24-hour
period. If each end device sends a message every hour, such a gateway can support up to 60,000
devices
1
. If the network includes 10 such gateways, the network can support roughly 100,000 devices
and one million messages. If more capacity is required, all that is needed is to add additional gateways to
the network.
And then, there is cost. Given the capabilities of LoRa-based end nodes and gateways, only a few
gateways – configured in a star network – are required to serve a multitude of end nodes. This means
that capital and operational expenses can be kept relatively low. Also, when the cost-effective LoRa RF
modules that are embedded in inexpensive end nodes are used in conjunction with the open LoRaWAN
standard, the return on investment can be considerable.
Radio Modulation and LoRa
A proprietary spread-spectrum modulation technique derived from existing Chirp Spread Spectrum (CSS)
technology, LoRa offers a trade-off between sensitivity and data rate, while operating in a fixed-
bandwidth channel of either 125 KHz or 500 KHz (for uplink channels), and 500 KHz (for downlink
channels). Additionally, LoRa uses orthogonal spreading factors. This allows the network to preserve the
battery life of connected end nodes by making adaptive optimizations of an individual end node’s power
levels and data rates. For example, an end device located close to a gateway should transmit data at a
low spreading factor, since very little link budget is needed. However, an end device located several
miles from a gateway will need to transmit with a much higher spreading factor. This higher spreading
factor provides increased processing gain, and higher reception sensitivity, although the data rate will,
necessarily, be lower.
LoRa is purely a physical (PHY), or “bits” layer implementation, as defined by the OSI seven-layer
Network Model, depicted in Figure 3. Instead of cabling, the air is used as a medium for transporting
LoRa radio waves from an RF transmitter in an IoT device to an RF receiver in a gateway, and vice versa.
