M2M devices are devices which communicate with other devices or servers, without the need for human interaction. These kinds of devices are used in many application areas such as industrial automation, smart cities, health, etc. These devices are to be networked within a premise (intranet) or over the internet. Within intranet, these devices can communicate over short range connectivity technologies such as WiFi, Zigbee, and Bluetooth. These devices have to connect with the internet using WiFi or cellular. WiFi may not always be an option because of lack of access points at all places, especially outdoor premises. In cases where Wi-Fi is not suitable, cellular effectively provides the last-mile connectivity.
Traditional cellular connectivity has been used in high-end devices like smartphones, tablets, laptops and netbooks. For this, cellular modems have evolved mainly to handle many scenarios such as seamless mobility and high data rates. Since M2M devices need to be low footprint and less power consumption, there is a need for customizing cellular modems. Here are a few insights to possible optimizations of cellular modems for M2M applications.
No or very less Mobility
Since the mobility of M2M devices is less or none at all (especially the devices that are not mounted on vehicles), there is a possibility of reduction of complexity of handling mobility aspects. A large component of cellular modem software efforts and certification costs arise out of the need for seamless mobility of the cellular connectivity. For M2M applications/devices, which have a provision of resending data in case of short term disruption of internet connectivity, a tailored cellular modem can address only the coverage loss aspect embedded in seamless mobility procedures. This is minimally required even for fixed location devices, as radio coverage by individual base stations for any given location, is becoming more and more dynamic. At an extreme, the logic for regaining coverage can even be embedded in the application that uses the cellular modem.
Restricted application types
If there is a need for only data, the voice and video call aspects can be configured out. Currently, the SMS functionality is necessary to support FOTA, though this may change as operators migrate towards upgrades via direct APN access. If voice and SMS are not required, IMS stacks can be removed from the modem software. Support of applications such as MBMS and ETWS/CMAS can also be configured out in cellular modems for M2M applications.
SIM card
There will be many M2M applications where SIM card slot is not externally accessible. For such devices, it will be essential to support SIM functionality which is configurable and embedded in the memory of the cellular modem, as against SIM functionality embedded in an IC card.
Standardization enabling low-cost cellular modems
With the migration to all-IP LTE technology, cellular standards which have traditionally catered to handheld/phone form factors are also facilitating the realization of low-cost modems. Support of Category-0 devices and half-duplex FDD operation by 3GPP are good examples. 3GPP continues to evolve LTE specifications to allow for M2M devices that can have significantly reduced RF capability as compared to normal devices.
Though all the above customizations are technically possible, some of these may be realized only with relaxation of conformance requirements by either 3GPP, or carriers which support such tailored modems.
In addition to above optimizations, considering the need for M2M devices to be power efficient, Power Save Mode in modem can be adopted for devices that communicate infrequently.
Considering the need of modem software in various devices such as automotive and handsets, M2M devices in segments like industrial, healthcare, automotive ( with diverse requirements), etc., there will be a need to statically and/or dynamically reconfigure modem software to suit these diverse needs.
Authors: Krishna Kishore, Roney Kurien, Ambika Patil