Low-Cost Cellular IoT Service: LTE Cat-M1 and NB-IoT
LTE Cat-M1 and LTE Cat-NB1 have been launched to replace 2G and 3G, which are slated for shutdown. What you need to know about these new LTE technologies for IoT: coverage, speed, cost, and the hardware to make them work.
Internet of Things (IoT) product claims typically describe ideal conditions, but not all IoT has access to a reliable wireless internet connection. After all, Wi-Fi still requires a router within range that is connected upstream to an internet service provider. Some IoT devices need an independent connection through cellular services, such as wide-ranging portable devices that do not have access to reliable, secure Wi-Fi (e.g., a smartwatch) or are located in extremely remote locations (e.g., a wilderness pipeline monitoring station). However, most IoT is driven to lowest cost, and IoT with cellular service is more difficult to arrange than a wireless connection to the Internet through a router. Typical IoT requires high-volume, low-cost sensing with some form of internet connectivity for communicating data to another, higher performance computer or server.
Cellular IoT is most easily accomplished with hardware modules that can provide global geographic coverage for the whole spectrum of Long Term Evolution (LTE) cellular communication technologies including 2G, 3G, and 4G LTE. There are many frequencies supported in subsets around the world. Once you figure out where you want to deploy an IoT device, you need to know what cellular frequencies are available in the location(s), which carrier(s) support those particular frequencies, and decide on the carrier(s) that best meet your needs. Then find a hardware module that supports those same particular frequencies. The hardware module and the carrier have to support the same frequencies.
Intel is working with Ericsson and China Mobile to deliver cellular IoT interoperable connectivity, incorporating the Intel® XMM™ 7115 NB-IoT modem chip (embedded in Fibocom’s module) into a factory setting.
There are several major carriers that provide infrastructure and coverage, called Mobile Network Operators (MNOs). In the United States, the MNOs with nationwide coverage are AT&T, Verizon, Sprint, and T-Mobile (with recent talk of merging for the latter two). Further down the food chain, a Mobile Virtual Network Operator (MVNO) provides service by essentially leasing access to the major carriers’ networks. MVNOs do not own infrastructure, often aggregate services across multiple carriers, and often take on markets that major carriers don’t find worthwhile. MVNOs tend to offer pre-paid contracts, are missing features offered by MNOs, and often do not offer the latest technology.
Expiration Dates for 2G and 3G
While 2G and 3G are excellent for many IoT applications, both networks are eventually going to be unavailable. The cost for carriers to maintain the 2G and 3G infrastructure is not worthwhile, as usage has steadily declined. However, since IoT benefits from the low bandwidth (BW) and low-cost 2G, T-Mobile has said that it will provide 2G and 3G service until 2021. AT&T has already shut down its 2G infrastructure, is no longer certifying new 3G products, and is speculated to end 3G by 2021 (unconfirmed). Verizon will end support for 2G and 3G networks by December 31, 2019. All the carriers are looking for ways to save on 2G and 3G infrastructure maintenance.
Both 2G and 3G, with slower bandwidths and existing infrastructure that is less expensive than LTE 4G, are good candidates for IoT. Depending on the technology used, 2G networks have a speed of 0.50 to 1.9 Megabits per second (Mbps) and 3G can deliver from 14 to 168 Mbps. Depending on the application, IoT device requirements can vary widely in terms of data rate bandwidth, the physical speed of a traveling IoT device, latency, range of reception, and in the number of reports the IoT device sends per time period (duty cycle). See Table 1 for a list of typical requirements for IoT devices across the spectrum of IoT applications.
The faster LTE (4G) option is nearly universal in coverage. (Note that coverage is not the same as reception; a mobile device may be in a location that has excellent coverage yet not receive a signal due to local conditions.) Since the term “LTE” is not trademarked or regulated in any way, it is marketed under many different names. LTE is also an umbrella term for many categories of LTE technology. For example, LTE Advanced (Cat 6 to Cat 20) is advertised under various names such as 4G+, LTE+, 4GX, 4.5G or 4G LTE Ultra. One of the advantages of LTE Advanced (LTE-A) is that several LTE carriers can combine resources to deliver a total bandwidth to increase data throughput with a mechanism called carrier aggregation. Carrier aggregation means users are less affected in a congested network, and carriers can operate networks more efficiently overall through aggregation agreements. For now, LTE offers significantly improved coverage over all others. LTE may include many protocols and frequencies, but LTE coverage is generally universal, whereas 2G coverage is much lower. Therefore, when considering developing cellular IoT, make sure that coverage for your area of services is on the carrier’s coverage map. Another consideration for Cellular IoT is that most carriers leverage roaming agreements with other carriers to provide worldwide coverage. Roaming plans bring an advantage because access to one carrier generally means access to global coverage plans. A carrier will have roaming agreements with global partners so that developers do not have to negotiate coverage with multiple carriers worldwide.
New Cellular Tech for IoT
Three new carrier network services explicitly intended for IoT use are Narrow-Band IoT (NB-IoT or LTE Cat-NB1), LTE Cat M1, and LTE Cat 1. It is important to note that the roaming agreements that carriers already have in place do not necessarily cover these LTE IoT technologies. Roaming also takes physically longer to connect. In June 2016, the telecommunications standards organization 3rd Generation Partnership Project (3GPP) announced that it had completed the NB-IoT, eMTC (a.k.a. LTE Cat-M1), and EC-GSM-IoT technologies standards to address the IoT market. The standards are part of Release 13 for LTE Advanced Pro networks.
Although LTE CAT-M1 and -NB1 are similar in costs, LTE M1 at a realistic 350 kbps is a little more expensive. LTE Cat-NB1 has a lower bandwidth of fewer than 150 kbps, with some modules promising 27 kbps. Unlike LTE M1, LTE NB1 is not able to smoothly hand off a connection between cell towers. However, if a device is deployed on LTE NB1 and must move about, a connection hand-off between towers is still possible at the application layer, even though stationary sensors using one tower are the target use case. LTE NB1 has a lower transmit current than LTE M1, a long sleep penalty (30s), and a latency of 1.4 to 10 seconds. LTE M1 has a higher transmit current, a latency of 10 to 15 ms, and is suitable for machine-to-human or vice-versa since LTE M1 supports Voice over LTE (VoLTE). Verizon introduced LTE Cat-M1 in late 2015 and also supports LTE Cat 1. T-Mobile launched the first plan for NB-IoT in January, 2018. T-Mobile also announced that the company has certified new NB-IoT modules from u-blox and Sierra Wireless for use on its network. Other LTE Cat-M1, -NB1, and Cat-1 hardware module suppliers include Sequans Communications, Link Labs, Gemalto, and Telit/Round Solutions, and more. Intel is working with Ericsson and China Mobile to deliver cellular IoT interoperable connectivity, incorporating the Intel® XMM™ 7115 NB-IoT modem chip (embedded in Fibocom’s module) into a factory setting.
For carriers, the choice to support NB1 or M1 has a financial impact in that LTE-M1 can be rolled out with just a software update to existing cellular towers, whereas NB1 requires both a software update and new radio hardware. Within North America, Verizon, AT&T, and Telus (Canada) have plans to support LTE M1. Most of the EU (Vodaphone), China, and Southeast Asia appear to be supporting LTE Cat-NB1. Australia’s Telstra has announced support for both LTE Cat-M1 and NB-IoT. Australia’s Optus looks like it will support NB-IoT, with Japan’s NTT DOMOCO supporting both LTE Cat-M1 and -NB1. Another cellular IoT development is the embedded SIM (eSIM) chip, which is surface mounted on a printed circuit board. Removeable SIM (Subscriber Identity Module) cards are bound to one carrier and have been the norm and are removed if a cell phone user wishes to change carriers (with an unlocked phone). eSIM chips are soldered onto a board and offer the promise of changing carriers without changing a SIM card. The advantage for an IoT developer with 10 thousand deployed IoT devices is that no manual SIM card change-outs are necessary in order to change carriers. Physically switching out a Sim card is a carrier’s leverage to prevent customers from switching. eSIM technology could possibly commoditize carrier service such that you could switch out carriers several times a day, depending on how the software works in the agreements with those carriers. Carriers are not going to adopt eSIM quickly. Nevertheless, installing an eSIM today is hope that the eSIM will someday be an option to switch carriers. Infineon’s eSIM chips, made with 40 nm technology, are in a miniaturized leadless package with dimensions of just 1.5 x 1.1 x 0.37 mm.
eSIM chips hold much promise for the IoT industry. Of huge promise for the IoT industry is a tiny board-mounted chip that can be activated with any carrier when it arrives at the customer’s doorstep. Similarly, eSIM can enable new business models where a carrier can more easily bundle services across many devices. One carrier package can enable a number of smart devices, with provisioning over the air.
As 2G and 3G age, they have a strong possibility of going completely extinct, supported by no one. Populate with eSIM now, even if it only has a single carrier, as you may be able to take advantage of profile provisioning down the road when it becomes available. Take advantage of companies like Particle.io and Link Labs, who provide everything from device to cloud, including carrier agreements, professional services, or DIY modules for these new LTE IoT technologies. (Particle is also an MVNO; Link Labs uses Verizon).
[i] “Machine to Machine Plans.” Unlimited Data Plans for Talk & Text | Verizon Wireless, www.verizonwireless.com/biz/plans/m2m-business-plans/ Accessed May 9, 2018.
[ii] “What You Need to Know About the 2G Network Shutdown.” Geotab Blog, 7 June 2017, www.geotab.com/blog/2g-network-shutdown/. Accessed May 9, 2018.
[iii] “T-Mobile Launches Nation’s First Plan for Narrowband IoT.” T-Mobile Newsroom, 9 Jan. 2018, newsroom.t-mobile.com/news-and-blogs/narrowband-iot.htm. Accessed May 9, 2018.
[iv] “Internet of Things NEWS.” T-Mobile Narrowband How IoT Stays Secure Comments, iot.t-mobile.com/narrowband-how-iot-stays-secure. Accessed May 9, 2018.
Lynnette Reese is Editor-in-Chief, Embedded Intel Solutions and Embedded Systems Engineering, and has been working in various roles as an electrical engineer for over two decades. She is interested in open source software and hardware, the maker movement, and in increasing the number of women working in STEM so she has a greater chance of talking about something other than football at the water cooler.