What is NB-IoT? Current NB-IoT status and settings for South Africa

NB-IoT (Narrowband IoT) is a type of Low Power Wide Area Network (LPWAN) used by mobile network operators. 

LPWAN is a special type of telecommunication network specifically designed for long range communications at a low bit rate of about 0.3 kbit/s to 50 kbit/s per channel.

NB-IoT operates in licensed spectrum to guarantee customers quality of service, provides strong coverage over large areas – even when devices are underground or deep within buildings (+20 decibels coverage vs GSM) and provides greater power efficiency, so devices can run on batteries for many years. It also allows networks to support upwards of 50,000 devices in a single cell without congestion for the first time. It is specifically designed for low-data IoT connectivity.

Key benefits of NB-IoT

• Backed by financially secure Telcos - NB-IoT networks are recognised as 5G technologies, and, unlike other LP-WAN technologies are future-proofed and offered by financially sound telco's.
• Battery Life – Optimised for the infrequent transmission of small amounts of data, NB-IoT enables extremely long battery life (30x battery life on NB-IoT versus 2G)
• Range – Excellent range and coverage to match 4G deployments, including extended-range indoors
• Performance – Cellular-grade wireless technology in licensed spectrum ensures enterprise grade performance
• Two-way communication - Enables over-the-air (OTA) firmware updates and remote debugging

For detailed technical information about the NB-IoT standard, including comparisons to other LPWAN technologies,  go here. 

LP-WAN options compared

Which network SIMs can be used for NB-IoT connectivity?

In South Africa, Vodacom has launched their NB-IoT network. Business Prepaid, Business Flexi or any existing Vodacom contract SIMs can be used for NB-IoT connectivity in South Africa, as long as it is provisioned on a specifically enabled APN, either on the public APN or on the SIMcontrol managed private APN. 

The Managed Private APN service offered on SIMcontrol is NB-IoT enabled. This allows prepaid, Business Flexi or contract SIMs to be activated for NB-IoT connectivity, feeding off a single pooled data bundle. Billing increments are in 1kb from the data pool, which is an important consideration as NB-IoT sessions can be very small. 

For NB-IoT connectivity outside of SA you can consider a Global Roaming IoT SIM that will roam on specific NB-IoT networks in specific countries (where available). Contact us to assist with advice on the latest roaming NB-IoT connectivity options. 

What is the current status of NB-IoT rollout in South Africa?

Vodacom has launched NB-IoT services to many sites across the country. Coverage (as at May '22) is claimed to be over 8,000 sites covering at least 80% of the population. All sites are on NB-IoT Rel14 (NB2) and have the PSM and eDRX (power saving) features active as from March 2023.

Further deployments continue, with the aim of having most of the current Vodacom LTE sites enabled for NB-IoT by 2025. NB-IoT is deployed in the LTE spectrum and therefore areas that only have 2G/3G coverage today would be enabled once these sites are upgraded to LTE.

There are no confirmed plans to roll out LTE-M spectrum in South Africa, but this is currently under review by Vodacom and should be activated at some stage in the future. 

MTN South Africa's NB-IoT rollout is still in limited testing phase and is not commercially available yet. When the servcie launches on MTN it will be activated on our Managed Private APN. 

Coverage Map
For the latest Vodacom NB-IoT coverage map, please go here.
(NB: Click on the "IoT" filter)

What does NB-IoT SIMs and data cost?

The billing model for NB-IoT is similar to normal cellular data, although the data usage is very small. On IoT-focused Managed APN's, data is billed on a per per-kb rate from one central pool of data. Contact us for detailed Managed Private APN pricing. On the public ("internet") APN, billing is in 10kb increments, so this is not advised for larger deployments.

NB-IoT does not have a per-message fee as per some other LPWA technologies. The key difference is that in contrary to other LPWA technologies, NB-IoT does not have a limit in data size that can be transmitted. Thus a message on NB-IoT could be a few bytes to over 1 kB. 

ARTICLE: Techcentral - NB-IoT roll-out will rapidly increase narrowband IoT adoption

ARTICLE: My Broadband - Flickswitch launches NB-IoT connectivity on its SIMcontrol platform

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TECHNICAL INFORMATION AND SETTINGS:

Vodacom Frequency Bands for the different radio technologies 

- 2G Service 

  o G900 – Band 8 

  o G1800 – Band 3 

- 3G Service 

  o U900 – Band 8 

  o U2100 – Band 1 

- LTE 

  o L900 – Band 8 

  o L1800 – Band 3 

  o L2100 – Band 1 

- NB-IoT 

  o L900 – Band 8 

  o L1800 – Band 3 

  o If more spectrum is allocated, may also deploy to lower bands

Device setup for NB-IoT only module on Managed APN:

NB-IoT only module:

The PDN connection over NB-IoT is established using either the Private APN name: "flickswitch" (Billing in 1KB increments) or Public APN name "internet"(Billing in 10KB increments).

(AT+CGDCONT=1,”IP”,”flickswitch”) or (AT+CGDCONT=1,”IP”,”internet”)

If no APN is specified, and the NB-IoT module connects to the PDN connection, the network will assign the default APN to the connection, which is "ltedefault.vodacom.za" (Billing in 10KB increments).

Device setup for Multi-Radio technology module on Managed APN:

The default connection will only be possible for a SIM that does not have other radio technologies active.
That is, if the SIM has 2G/3G/LTE as additional services active, you have to specify the specific APN which to connect to. If the SIM has 2G/3G/LTE as additional services active, the same APN name can be used.

If using public APN's

For 2G/3G/LTE/NB-IoT use APN: "internet" (Billing in 10KB increments).

If using the Managed Private APN, the same APN name can be used for either, i.e. "flickswitch"(Billing in 1KB increments)

For 2G/3G/LTE?NB-IoT use APN: "flickswitch"

Typical connection procedure
Each NB-IoT module has their specific connection procedure. For most modules though, the AT-command flow as per below can be used to establish a successful PDN connection for NB-IoT. This will assign an IP address to the device and allow access to a server via the internet.

 Typical AT-command sequence:

1. AT+CEREG=2  (Enable EPS* registration status check.)

2. AT+CFUN=1. (Enable mobile radio)

3. AT+CGDCONT=1,”IP”,”flickswitch". (Set APN to flickswitch APN)

4. AT+COPS=1,2,”65501” (Forces attempt to register on EPS network. Allow few seconds for device to establish connection)

5. AT+CGPADDR (Show IP address assigned)

* EPS Bearer is a virtual connection between the device (UE) and the mobile network element (PGW) allowing the UE to send/receive data

3GPP specifications

The Vodacom network is on NB2 or 3GPP Release 14.

NB-IoT power saving

All Vodacom sites are on NB-IoT Rel14 (NB2) and have the PSM and eDRX features active. 
NB-IoT devices are expected to be ‘sleepy’, meaning that they revert to a low energy consumption sleep mode whenever possible. While in this state they are unreachable from the network and so it is important to fully understand this behaviour when designing solutions. The basic pattern is similar to that for 2/3/4G technologies but the increase in its use means that the behaviour must be tightly managed.

The full range of T3324 and the T3412 timers are supported by the Vodacom network. No default values or specific values are pushed to the device. The device can thus select from the allowed range based on 3GPP standards.

Power Saving Mode (PSM) 

When the device sleeps the connection can appear still as valid but the device is unreachable from the network. During power save mode the module consumes very low current and the TX/RX interface is turned off. In this state it is still possible to maintain a serial connection from outside to the module so as to interact via AT commands. 

With NB-IoT it is possible to automate the power saving on the module via various timers which can configure the module from the network side. Traditional power management via the application processor will be still possible. The network configured timers enable the module to enter PSM a defined period of time after last transmission/receive. They can also periodically wake up the module to be reachable for incoming messages. Also in PSM the application processor can request to send a message at any time and wake up the module to do so. 

The time taken to wake from sleep mode depends on the state of the module when it went to sleep. If it was fully attached, then the wakeup time is minimised as an existing attach will still be available to use. If not, the module will need to run through a sequence of steps to establish a new attached which takes time as well as consuming power.

Extended Discontinuous Reception (eDRX) 

eDRX is an extension of an existing LTE feature which can be used by IoT devices to reduce power consumption. eDRX can be used without PSM or in conjunction with PSM to obtain additional power savings. eDRX allows the time interval during which a device is not listening to the network to be greatly extended compared to DRX as used by smartphones. This is because for an IoT application it might be quite acceptable for the device to not to be reachable for a longer period. eDRX is usually not providing the same levels of power reduction as PSM, therefore it is best used in conjunction with PSM for the best performance.

The best way to test power saving would be through monitoring tools (power measurement) on the device side.

More Information on eDRX and PSM (Source: Sierra Wireless)

So, what is eDRX? What differentiates it from the Power Saving Mode (PSM) feature? And in what types of IoT applications might a company want to use it?

What is eDRX?

Developed by mobile network standardisation body 3GPP and introduced in 3GPP Rel.13, eDRX enables application developers to set, and later change how long an edge device stays in low-power sleep mode before it wakes up to listen for any network indications for pending data.

With eDRX, the device can listen for pending data indications without having to establish a full network connection. By just listening for a pending data indication, eDRX uses less power than if it made a full network connection, so this process helps preserve the device’s power. The time needed for this listening process is also much shorter than the time it takes to make a full network connection.

The maximum sleep time for eDRX devices range from up to 43 minutes for devices using LTE-M LPWA networks, to up to three hours for devices using NB-IoT LPWA networks. The minimum sleep time can be as short as 320 milliseconds (ms) for LTE-M and 10.24 seconds for NB-IoT.

In the past (i.e. with eDRX’s predecessor, DRX), the length of time that a device would sleep before waking up was dictated by the network (typically 1.28 seconds or 2.56 seconds). With eDRX the device, rather than the network, chooses the length of time it will sleep, a period referred to as the eDRX cycle. Since a device is not reachable when it is sleeping, the time to reach a device depends on how long the application developer sets the eDRX cycle.

This ability to set the length of the eDRX cycle provides IoT application developers with a lot more flexibility when it comes to balancing a device’s reachability versus its battery consumption. For example, if the application chooses an eDRX cycle of 82 seconds, when a cloud service sends the device a command (e.g. report your location), it could take up to 82 seconds for the device to get that command before it would report back its location. This delay is often referred to as “mobile terminated latency”.

How sensitive an application is to mobile terminated latency depends highly on the application. For example, a pet finding application could tolerate a couple minutes to get a location fix for a pet — especially if this means the battery will last 1-year versus 1-week. With other applications, like a remote light, one might only want to wait a maximum of 5 seconds for the remote battery powered light to respond to an “ON” request — which means the eDRX cycle needs to be set to 5 seconds.

The other good thing about eDRX is that it is not static — the application can change it anytime it wants. For example, the application can set the original eDRX cycle for an hour (extending the life of the device’s battery) and then later, when the application needs to be more responsive, reduce the eDRX cycle to a couple of minutes (using more battery power, but allowing the device to be reached with a much shorter delay).

How is eDRX different from Power Saving Mode (PSM)?

PSM is another common feature used to reduce the power used by LPWA devices. In general, PSM sleep times are much longer than eDRX. These longer sleep times allow the device to enter into a deeper, lower power sleep mode than eDRX (e.g. PSM sleep power is a few microamps whereas eDRX sleep power is 10-30 microamps). However, a PSM device takes much longer to wake up out of sleep mode and it is active for a much longer period of time, because it must connect to the network before receiving any application data. For eDRX, the device needs to wake up and listen for 1 ms whereas for PSM, the device will need to wake up and receive and transmit control messages for about 100-200 ms before it can receive a message from the cloud application – a 100X difference!

Some IoT applications do not need to be reachable at all (e.g. they only transmit data to the cloud) or they can tolerate long reachability delays (e.g. they only need to be reachable once per day). For these types of applications, PSM is a good choice, since its sleep mode uses less power and is designed to be used when a device only has to wake up infrequently.

For other applications where one needs to reach the device more often (e.g. once per hour) eDRX is a better choice. As mentioned previously, with eDRX, the device can wake up and check for a pending data indication a lot faster than a device using PSM can (1 ms vs 100 ms), while using less power while it does so. eDRX can also help lower an application’s data transmission costs, since unlike PSM, which requires the device to connect and poll the cloud to see if there is data for it, eDRX only connects to the network and communicates with the cloud application when the device receives the pending data indication from the network, indicating there is data from the cloud application for it.

Though data transmission costs can be a factor, the most pertinent question of which power saving feature to use usually comes down to the use case’s reachability needs. Although it depends on many factors, in most cases the tipping point for when to use eDRX vs PSM is if the application needs to be reachable in a time period of approximately six hours or less.

What use cases is the eDRX feature best suited for?

eDRX is well suited for IoT application use cases where you want to preserve a low-cost edge device’s battery power, and the device’s reachability does not have to be instantaneous, between 5 seconds to six hours.

One example of such a use case is a smart gas meter monitoring IoT application. With many smart gas meter applications, government regulations mandate that the company responsible for the meter be able to quickly shut off the gas supply in a building, for example, after being informed that there is a fire nearby. While the company does not need to shut off the gas immediately, it does need to do so within a mandated time period, for example, two minutes from receiving the indication from the fire department of the fire spreading to the location where the smart gas meter is located.

With eDRX, the company can set up the smart gas meter to request an eDRX cycle of 82 seconds. This eDRX cycle ensures the meter can respond to a shut-off request within the required 2 minutes. In this way, the life of the device’s battery can be extended, the cost of the device can be reduced (since it needs a smaller battery), and the data transmission costs for the application are minimized (since the device only connects and transmits data when it is told to by the network). All while complying with the government regulation and helping ensure the building’s occupants are safe if there is a fire nearby.

Another example of a popular IoT use case that eDRX is well suited for are what I would call “finding” IoT applications – for things like pets, bikes, laptops, expensive tools and similar assets. Unlike asset tracking applications, where frequent, close to real-time updates are required, for these applications the user will usually only want to know where the asset is when the asset has been misplaced or lost. Of course, when they do want to find the asset, they will often want this information quickly — within 1 or 2 minutes is usually acceptable if this provides the device with an extra year of battery life. In a couple of minutes Fido can’t get into too much trouble – but give him an hour on his own, and he can get into a lot of trouble with the neighbor’s cat.

With eDRX, users can learn the current location of their pet, bike, laptop, tool, or other asset in a minute or two, using a small, low-cost, low-power device attached to the asset. In addition, since the device would only connect to the network when it was told to, data transmission costs for the application would be nearly zero.

As the two examples above illustrate, eDRX expands the IoT market by offering application developers the opportunity to deploy new kinds of IoT applications for use cases where they do not need to reach their edge device immediately, but also can’t wait six or more hours to do so. For these type of use cases, the Sierra Wireless HL7800 LPWA module provides best-in-class eDRX performance.

With an eDRX cycle of 82 seconds, the average current used by the HL7800 can be as low as 50 microamps (depending on mobility, temperature, coverage, and network configuration and of course application data transmissions). Assuming minimal application data transmissions, this means one alkaline AA battery could power the device for more than 2 years! Or if a rechargeable battery is preferred, a 2x1x1cm lithium Ion battery (small enough to fit around Fido’s neck) could power the device for more than 3 months!

RESOURCES

- Research Paper - Evaluation of next-generation low-power communication technology to replace GSM in IoT-applications:

https://ietresearch.onlinelibrary.wiley.com/doi/10.1049/iet-com.2019.0168

- Evaluating NB-IoT - A Guide: Here is a handy overview of NB-IoT for technical decision-makers: https://www.vodacombusiness.co.za/cs/groups/public/documents/document/vodafone_nb%E2%80%93iot_white_paper_fi.pdf

- Attached: Vodafone NB-IoT White Paper 

(Tags: nb-iot nbiot narrowband iot lp-wan lpwan vodacom mtn. Source: Vodacom, media, other)