The fast-growing M2M market presents a series of wireless design challenges (part 2)
Battery life is critical
The time between battery charging or replacement is critical to the success of some industrial computer products. A container-mounted tracking device, for example, in-vehicle system may be required to run for several days if it's being shipped by air or road, and up to several weeks if shipped by sea. Battery life must be adequate to support these timescales.
Mobile phones are typically expected to run for two or three days on a charge. Hence, consumer expectations for the operating life of health and fitness devices will be similar. When comparing modem and GNSS receiver specifications in these applications, both the operating and standby current consumption are important, as well as the power-saving functions. The latter may include auto-wakeup features and intelligent power-saving modes, such as the ability to log data autonomously without waking the host processor. Ideally, components should only wake up when needed.
Mobility demands multi-standards compliance
Global mobility is increasing for people and goods, so it's important to consider where a modem needs to function today and where it may be required to work in the future. GSM is supported by four main frequency bands worldwide, UMTS by six, and LTE over 30. An electricity meter is usually static whereas a resource management system may be required to work in all regions of the world and should include either a quad- or dual-band GSM modem (depending on the location), or six-band UMTS modem.
Certified modems accelerate embedded system approvals
Any cellular network device, whether for GSM, UMTS, or LTE, needs regulatory, industry, and operator certification. It significantly simplifies and speeds up the in-vehicle system certification process if the modem embedded in the device is certified.
What's needed today may be different tomorrow
While GSM/GPRS networks are perfectly capable of handling the small volumes of data transmitted in remote metering applications, GSM bands are already being considered for re-allocation to 3G and 4G services. To save the expense of future-proofing, it's a good idea to design with on-board computer standards in mind. Today, this means designing with UMTS/HSPA or LTE modems, or at least future-proofing hardware to simplify upgrades.
Nested design simplifies technology upgrading
Cellular M2M technologies are in embedded system continuous evolution and when designing a new device enabling cellular connectivity, it's important to consider its upgradability to newer technologies to optimize the design cost. Here, there's on-board computerlayout compatibility across the entire cellular on-board comouter modem range (GSM, UMTS, CDMA, and LTE). With this approach, as shown in Figure 2, one PCB layout can be used for all end-product variations, ensuring an easy migration between on-board computer and module generations, also thanks to the AT command compatibility within the different modules.