Applications on the Internet of Things (IoT) tend to be very different from those that the LTE network was originally built for.
Your smartphone’s voice and data used large amounts of bandwidth; IoT applications use far less. Cat 1 and Cat M1 modems allow a lot more IoT traffic to fit in the same LTE network bandwidth. LTE Cat 1 uses less network bandwidth than traditional LTE modems, and Cat M1 uses significantly less. The two types of modems differ in three primary areas: bandwidth, power requirements and complexity. Once you define your needs it should be relatively easy to select the right one for any IoT-based application.
The first of the criteria when choosing an IoT modem type is the upload and download data rates. If the Cat M1 rates are sufficient for your application, that would be the obvious choice. If you need more bandwidth than Cat M1 provides, then Cat 1 would be the best choice.
Power consumption can be very critical for applications that run on battery or that may need to run for extended periods on backup power if grid power fails (Actual power consumption depends heavily on the nature of the application). Both modems, but especially Cat M1, have power-saving modes they can enter when not actively sending or receiving data. The more sporadic your data transmissions, the more you will benefit by using Cat M1. For more information on power-saving features go to How LTE Cat M1 Saves Power and Money for the Internet of Things and From the Workshop: About LTE Cat M1 and Use Cases.Complexity of the modem affects power draw and modem cost. Cat M1 draws significantly less power than Cat 1 and simplifies device design. It also allows chipset, module, and modem manufacturers to use fewer, and less powerful components, resulting in lower hardware costs.
Data can be downloaded and uploaded simultaneously by selecting full duplex mode, which is available on either type of modem. Half duplex mode, available only on the Cat M1 modem, allows data to travel in only one direction at a time. This limits the speed to 375kbps instead of 1 Mbps for full duplex. The advantage of half duplex mode is that it requires less power for situations where there is no need to both send and receive at the same time. For this reason, most carrier implementations of Cat M1 have been limited to half-duplex only.
Choice of modem will depend on your application, but the following sample applications should give an idea of the capabilities of each type of modem.
Cat 1: Digital signage, ATMs, kiosks, video surveillance, vehicle telematics, cellular gateways.
Cat M1: Personal/asset trackers, sensor nodes, utility meters, monitoring systems.
In the future, another IoT-specific option will be NB1 (NB-IoT). It will differ from Cat M1 in several ways. The NB1 data rate will be smaller still than that of Cat M1 and will not work for mobile applications. NB1’s power consumption will be low, but will depend on how frequently the modem goes through the sleep/wake cycle and its latency will be higher than that of M1. But, again, this is for the future; today the best choice of modem for IoT connectivity is the LTE Cat 1 or Cat M1.
In summary, there is not one ideal IoT modem that is one-size-fits-all. The type of application will determine the appropriate type of modem, and it is likely that as the technology develops, the capabilities of modems and range of modem options will expand as well. Depending on your requirements, which modem works best for your application, LTE Cat 1 or Cat M1?