There are several competing standards for ubiquitous wireless connection of the Internet of Things, including two specific to LTE alone. Operators are actively deploying both on a nationwide basis. We summarise what these are, review their commercial status and consider the implications.
3GPP standards for Internet of Things
The Internet of Things is all about adding wireless connectivity into large numbers of our everyday objects. These range from the more obvious (e.g. utility meters), the more frivolous (e.g. toasters) to the sublime (e.g. your umbrella). Once connected and paired up with an App and some intelligence in the Cloud, you can expect some useful insights that help lifestyle management – powering down unused electrical equipment, ordering more bread or reminding you to take your umbrella when rain is forecast.
Perhaps the bulk of these connected devices will be inside the home or office, where a local area/very short range solution might work. Low power consumption is key because many of these devices will be battery powered, with some devices intended to have lifetimes of up to 10 years. That rules out standard cellular or Wi-Fi, and both have developed optimised versions to squeeze out many years of service from a coin sized solution.
There are too many different short range wireless technologies to list here, but I’d pick out ZigBee (based on 802.15.4) operating in the 2.4GHz band at up to 250kbps and Z-wave operating at around 900MHz.. These both use mesh architectures, so messages can be passed through any nearby device until it reaches the local hub. Here’s a useful comparison between the two.
Outdoor IoT requires very wide area coverage and this is where cellular should come out on top. There are some competing wide area services, such as SIGFOX or LoRa, which can use large towers to cover very wide areas. These both need their own dedicated networks with the associated cost and complexity.
3GPP standards for Internet of Things
The cellular standards body has adopted two separate solutions based on LTE. These are intended to run on existing LTE basestations, using the same LTE licenced spectrum, modulating the signal and bandwidth to improve range (and especially in-building penetration) and battery life. The downside is a much slower data rate and lack of mobility (i.e. handover between sites during a session). That tradeoff is very worthwhile for something that doesn’t move or send much data (like an electricity meter) or even a tracker device (like a shipping container daily reporting its latest location, temperature, G-force experienced etc.)
The main difference between normal LTE signals and an IoT one is the breadth of spectrum band used. Typical LTE would consume 5, 10 or even 20MHz in each direction, enabling high data rates of many 10Mbps. Narrowband IoT in 3GPP Release 13 squeeze signals into 1.4MHz (Cat-M) or 200kHz (NB-IoT).
This reduced spectrum also reduces the data rate to 1Mbps or 10s of kilobits/sec but greatly improves battery life and in-building penetration. NB-IoT can gain as much as 20dB over standard LTE which would compensate for much of the shielding in the outer walls of a typical office building.
Two specific features help extend battery life:
- PSM (Power Save Mode). Puts devices to sleep when they aren’t required and don’t need to be woken up. Ideal for smart metering etc.
- eDRx (Extended Discontinuous Receive): More like power-naps or dozing, reducing active monitoring for incoming messages and so extending the time it takes to wake-up from 2.5 seconds to as much as 40 minutes.
These services can be deployed within the existing LTE spectrum. Cat-M can be overlaid in either FDD or TDD while NB-IoT is FDD only but can be allocated to guard bands or even standalone (refarming previously used GSM frequencies).
NB-IoT (Narrow Band Internet of Things) is best for the lowest power, lowest cost, lowest throughput, delay-tolerant devices and provides the greatest coverage/range and longest battery life. There are three spectrum choices – in-band alongside LTE, guard-band at the edges of existing LTE carriers and separately assigned spectrum such as partially repurposed GSM bands.
Cat-M supports the broadest range of IoT capabilities, including voice support, limited mobility and data rates up to 1Mbps. Coverage is much better than for regular LTE (about 15dB margin) but power consumption will be higher than for NB-IoT.
There is a role for both but we are seeing some operators take a strong lead on one or other option.
Verizon and ATT both vied to be the first with Cat-M service, with ATT switching on October 2016 and Verizon in December 2016. Verizon recently claimed to have nationwide coverage (2.4 million square miles), with 14,000 developers using their ThingSpace IoT platform and pricing as low as $2 month. AT&T expects to match that by end June and is also rolling out the technology in Mexico before end 2017.
Other Cat M deployments worldwide include:
- KDDI Japan - nationwide during 2017
- KPN - nationwide by end 2017
- NTT DoCoMo Japan
- Orange - Pan-European starting with Belgium and Spain
- Telefonica - launch by Q2 2017
- Telstra Australia - nationwide planned but no dates given
- Telus Canada - launch during 2017
Other multi-national operators have chosen to focus on NB-IoT, with Vodafone strongly championing the technology. With at least an extra 5dB, these signals are going to penetrate more widely and deeply into places that Cat M won’t reach.
Vodafone plans to deploy NB-IoT throughout Europe at 800MHz and has already commercially launched in Spain, although launch dates have slipped for Ireland and Netherlands.
The GSMA forecasts at least 20 networks will be live before end 2017, with 24 actively committed to deployment.
Multiple technology deployments but cellular IoT positioned for long term market domination
Several leading operators plan to deploy both Cat M and NB-IoT including AT&T, Verizon and Orange. It’s not an either/or scenario.
Some operators have chosen to deploy proprietary non-cellular IoT systems, sometimes in parallel with cellular IoT. SK Telecom deployed natiowide LoRa and Cat M last year throughout South Korea. Telefonica, NTT DoCoMo and SK Telecom have invested directly in the SIGFOX company itself.
This thought provoking article argues that because the cellular industry took so long to provide a commercial service, it allowed proprietary systems to gain a foothold. However, once cellular IoT is widely available at low cost, the potential for rapid deployment means they could quickly gain dominant market share. The author argues that cellular IoT will win in the long term but that long term revenues may be disappointing. Some of the devices with a 10 year battery life may outlast the proprietary networks they connect with.
Ensuring ubiquitous service coverage
No network provides truly ubiquitous coverage in every single geographic area.
Innovative IoT equipment vendors have developed Smart SIM smartmeters, which can connect to any of the national cellular networks and select the best or only available one automatically.
But there are remote and rural areas where no service provider reaches – mines, oil platforms etc. – as well as deep inside or below buildings. These will require additional coverage solutions and this is an aspect that small cells can address. It is also quite feasible in the future that private LTE systems might be used within industrial complexes for this purpose, either in the CBRS band or (in remote areas) in co-operation with mobile operators themselves.
Ubiqutious always-on connectivity is essential for most IoT devices and small cells will have a part to play as the industry matures.