IoT, Slower, Small and Lower is Better!

The use of cellular devices beyond traditional cellphones has exploded in recent years in Business to Business (B2B) and Machine to Machine (M2M) applications. These applications are more commonly known as the Internet of Things (IoT). Our thirst for more and more data has pushed the development of cellular technology from 2G to 3G and now 4G, with 5G being determined. 3G has Data/BIT rates as high as 2 Mbps, 4G LTE has rates up to 20 Mbps and now LTE Advanced is a staggering 300 Mbps. When 5G comes out, the data rates will be amazing compared to what we know today. Surprisingly though, there is a movement for lower data rates for cellular plans as well as smaller and cheaper devices.

If the cellular data rate trend is going from 2G to 3G, 4G and then 5G, why develop cellular technology for lower and lower data rates? The simple answer is cost of cellular, or more specifically the cost for a cellular data plan. For many IoT applications, the amount of data transmitted is substantially less than traditional cellular devices such as routers and smartphones. For example, a sensor node network in a Smart Factory may only wake up once an hour, take a reading and transmit it and then go back to sleep. The amount of data is very low. The cost of using existing data plans associated with 3G/4G technology comes at a prohibitive cost. It just does not make financial sense.

Let’s look at IoT cellular devices that are available today. The first devices that came out used 2G/3G and 4G technologies and existing cellphone infrastructure. These devices are large finished boxed units such as Digi International’s WR44-L5G4-AE1-MD. This router could be used to provide cellular service for a remote location or for the transportation industry like a bus or train. If used in the transportation industry, the cellular service could provide vehicle data for the service company, commercial marketing for the external displays and Wi-Fi service for the passengers. These devices can provide high data rates and, like traditional cellular services, plans are priced by the amount of data used. The more data, the more expensive the plan. Now using these devices in a lower data rate application like IoT is cost prohibitive.

Now companies are designing small cellular modules that can be incorporated into a finished device specifically for IoT. Here are few of the newer cellular technologies being used: LTE CAT1, LTE-M and NB-IoT.

LTE CAT 1 is the first generation of cellular specifically designed for IoT. It has data rates of 5 Mbps with products available today from a variety of companies such as Digi, NimbeLink and Multi-Tech.

LTE-M (CAT-M) has a maximum data rate of 1 Mbps. Yitaek Hwang, a product engineer at Leverege, said in an article for IoT For All that, “Cat-M is really targeting LPWAN applications like smart metering where only small amount of data transfer is required.” Both LTE CAT 1 and LTE-M work on existing LTE cellular infrastructure which makes implementation easy.

NB-IoT data rates are even lower at 144 kbps. The infrastructure is not nearly developed as LTE, but it is being developed by a variety of communication companies.

With these lower data rates, there will be cellular plans that are specifically designed for these devices, and the user cost will be substantially lower. This will result in huge cost savings per device.

Digi's XBC-V1-UT-001 is Available Today and Uses 4G LTE CAT Verizon Cellular Technology

Let’s look at a few examples of Cellular devices for IoT available now and coming soon. Digi has added cellular to the XBee® platform. For some people the XBee is just a module. According to Digi’s website: “Digi XBee is more than a module. In fact it’s a complete ecosystem of wireless modules.” XBees were first released in the early 2000s. These modules come in a variety of protocols such as ZigBee, 802.15.4, 802.11 bgn, and now cellular.

Digi has released one cellular model and has several more coming in the second half of 2017. The XBC-V1-UT-001 is available today and uses 4G LTE CAT Verizon Cellular technology. This is a very powerful device in a small package and is great for applications that need large data rates. An AT &T version is coming out soon. Other XBees coming out are designed for low data rate applications, which makes them ideal for IoT. This includes cellular technologies such as LTE-M and NB-IoT; for LTE M there is the XBC-V2-UT-001, and for NB-IOT there is the XBC-N1-UT-001. Since the data rates on these units are much smaller, the data plans to support these devices will be much less. These small footprint, small cost devices will make IoT more affordable which in turn will expand IoT into areas that we have never imaged before.

The IoT of today means slower data rates and smaller modules which will lower user cost. Slower, smaller and lower means that the IoT will become bigger, better and more widespread in our IoT world of today and tomorrow.

About this author

Image of Stephen Wegscheid Stephen Wegscheid, Senior Product Manager-Semiconductors at Digi-Key Electronics, specializes in analog/linear electronics, connectivity products, and single-board computers. He has a Master of Science degree from Bemidji State University and over 25 years of experience in design, manufacturing, and distribution. Additionally, he is the holder of a US patent.
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