LoRaWAN is unable to meet a key IoT network deployment requirement: bi-directional communication to upgrade firmware-over-the-air and update security patches to end-devices that have already been deployed in the field. The new LPWAN technology Weightless-P has taken position as the new catalyst to bring sustainable IoT networks to life.
Let’s first take a look at the three reasons why LoRaWAN is unable to support Firmware-Over-The-Air (FOTA) for a real IoT deployment.
1. With very stringent downlink limitations, LoRaWAN would take an unreasonably long time to update the firmware for a single end device. There are a few elements to take into consideration including the distance of gateway to end device and spreading factor utilised but It could potentially take weeks to send a 200K update to ONE end-device given 20 bytes on a 5-minute polling.
2. LoRaWAN gateway transmissions are uncoordinated. This means if a gateway attempts firmware downlink transmission, it will not be able to listen and receive messages from the rest of the end devices in the network. When you have thousands of end devices deployed, the end-devices won’t know the gateway is conducting a firmware upgrade and all messages being sent will be lost.
3. LoRaWAN gateways are duty cycle limited. LoRaWAN gateways can only transmit 1% of the time (ETSI), and will need all of the downlink resource for acknowledgements and MAC control messages. Very, very little would be left over for FOTA multicast. In the US, the 1% duty cycle limit does not apply so the network basically stops functioning to facilitate uplink.
Weightless-P is a narrowband LPWAN technology which supports FOTA and true bi-directional communication. Duty cycle limitations do not apply as Weightless-P utilises spectrally efficient narrowband operation and frequency hopping.
There have been so many early adopters who have rushed into deploying LoRa gateways without taking into consideration the major drawback of LoRa’s inability to support firmware-over-the-air.
Why the criteria of 48 messages / day ; 12 byte messages was chosen..
The Smart Metering data is used differently by different levels of the service chain.
Meter readings – for billing purposes
Half Hourly readings – for additional services or sophisticated products
Maintenance messages about the health of the meter – such as memory problems
Firmware messages – to update the software in the meter
Configuration messages – to set up new products
Pay As You Go messages – to top up PAYG credit
Tamper messages – to detect theft and security attacks
Export meter readings – to measure how much electricity your solar cells or wind turbine is passing back to the network for load management and to credit the customer depending on the commercial arrangement.
Distribution Network Operators
Power outage messages – to know when and where outages occur
Meter readings – for network billing to suppliers
Half Hourly readings – for network load planning
Voltage and Power Factor readings – for network operation and planning.
Export meter readings – for network operation and planning.
Other Authorised Parties
Meters readings – to analyse and show you your energy usage
Half Hourly readings – to analyse and show you your particular energy profile shape.
Smart Meter Capacity Calculations
Figure 1: Mac Throughput (Europe)
Figure 2: Number of Smart Meters supported per Base Station (Europe)
(based on criteria: 48 messages per day ; 12 byte messages )
Figure 3: Mac Throughput (United States)
Figure 4: Number of Smart Meters supported per Base Station (USA)
(based on criteria: 48 messages per day ; 12 byte messages )
Nearly all uplink messages are unacknowledged (you won’t know if the message was ever successfully delivered)
All gateways in range see all uplink traffic (not safe)
LoRaWAN requires an enormous amount of bandwidth (tough to scale, culprit for ISM band traffic, subject to interference from other LoRaWAN gateways)
1. Nearly all uplink messages are unacknowledged
LoRaWAN has 1% Duty Cycle Limit for both end devices and the gateway (A duty cycle is the fraction of one period in which a signal or system is active. A period is the time it takes for a signal to complete an on-and-off cycle) In order to support the 1% duty cycle limitation for the gateway, all uplink messages are unacknowledged and uncoordinated, LoRaWAN is considered a “pure-aloha” scheme.
What is pure-aloha: “The idea is applicable to systems in which uncoordinated users are competing for a single channel (shared resource). ALOHA permits users to transmit any time they feel like. Collisions will occur and therefore colliding frames will be destroyed. However, if feedback is available on the destruction, then users will be made aware of their frames have not been transmitted (received) successfully (1)”
“Such a network has about 18% efficiency. This means that 82% of packets are lost when a LoRaWAN network is fully utilized. Since most messages are unacknowledged, the end node does not know its message was missed”(2). The Things Network also confirms this statement by stating “the capacity for downlink messages is even lower than for uplink messages, so don’t waste it.”
2. All gateways in range see all uplink traffic (not safe)
No explanation required.
3. LoRaWAN requires an enormous amount of bandwidth
In wireless communication, the Hata Model for urban areas, also known as the Okumura–Hata model for being a developed version of the Okumura model, is the most widely used radio frequency propagation model for predicting the behaviour of cellular transmissions in built up areas. This model incorporates the graphical information from Okumura model and develops it further to realize the effects of diffraction, reflection and scattering caused by city structures. This model also has two more varieties for transmission in suburban areas and open areas. (source: Wikipedia)
The Hata Model simulation was conducted for Sigfox, LORA, and Weightless-P with the base station height set at 30m and the end devices heights set at 0.5m. The following simulation was conducted at Ubiik (hardware developers for Weightless-P) but we have checked their math and our team has confirmed the numbers are accurate and unbiased.
Let’s first take a look at the U.S Results (902-928MHz)
Now let’s take a look at the results in Europe (863-870MHz). The only difference is LORA is only able to use a smaller bandwidth.
One of 3GPP’s chief low-power, wide-area (LPWA) technologies under development is NB-IOT (narrowband IOT) . Many have been speculating over the differences between NB-IOT and the current LPWAN technologies in the unlicensed frequencies such as LORA, Weightless-P, Sigfox, RPMA. Some individuals have even gone as far as saying NB-IOT will be the death of LPWAN technologies. But that is likely not going to be the case as there will always be a huge difference in use-cases of licensed and unlicensed technologies. The best analogy is WiFi (unlicensed) vs 4G (licensed). The business models and use-cases built around WiFI and 4G are “night and day” .
NB-IOT may not be as robust as we are expecting it be. Check out the following features that are likely to be a slight let-down to NB-IoT enthusiasts
1.No full acknowledgement: By design (found in 3GPP Specification TR45.820) NB-IOT is planned to only acknowledge 50% of messages serviced by the wireless technology. This is due to limited downlink capacity. Unlicensed technologies like Weightless-P allows 100% full acknowledgement of every message. If every message is of high value, you will need to know if your messages are successfully sent/received via an acknowledgement.
2. Long Latency: Transmit packet aggregation from buffering of messages and data. NB IOT will not be able to support “real time” responses therefore not suitable for time sensitive applications.
3. IoT devices in the network will not be the priority. The licensed spectrum is EXPENSIVE. Ingenu mentioned “$4.6 billion in a recent auction for only 20 MHz of spectrum!” IoT traffic will always come second to high profit margin, cellular traffic.
4. Long battery Life? The actual battery life will remain unknown until the Cellular LPWA networks are commercially available.
5. Availability: NB IOT is a technology that will be ready a few years down the line.
6. Compatibility: NB-IOT will differ across regions and carriers. Huawei initially pushed for a clean slate NB-IOT technology that would not be backwards compatible with 4G etc. This actually makes a lot of sense as it would be eliminating a lot of the unnecessary overhead. But just as Huawei began making progress, Nokia and Ericsson began insisting on building upon the frameworks of LTE which means significantly more complexity and unnecessary overhead. Not a very nice foundation for such a huge project.