Choosing the right technology for long-range M2M — 2G/3G, LTE or Weightless?
It covers a number of different markets and verticals that have diverse specifications for parameters that include throughput, mobility, power, cost, real-time application and ease of deployment. So which is the best technology to use for M2M?
Although short range communications, served by technologies such as ZigBee, Bluetooth-LE and Wi-Fi, represent an important part of the M2M connectivity domain, long range cellular standards are more appropriate for a wide range of applications and markets, and are expected to grow substantially over the next year.
The reasons for using cellular for M2M obviously include mobility and coverage, but cellular technology also offers advantages to the operator in terms of widespread deployment and ease of device management. Nevertheless it is clear that M2M poses many additional challenges to traditional cellular networks that use technologies like GSM, UMTS and LTE. In particular, some M2M use cases require devices to be deployed deep in buildings, where the coverage limitations of cellular technologies can adversely impact deployment feasibility and costs. Many applications also require battery-operated equipment ideally to survive for many years, which could be critical in certain application domains in order to keep down deployment and maintenance costs. Minimising the cost of the devices is also an important enabler for the widespread deployment of the Internet of Things (IoT) business model.
One of the most promising profiles of M2M is expected to what 3GPP defines as ‘low-cost, low-power, high-coverage non-real time applications using infrequent small bursts and limited mobility’. The cellular technology that best serves this requirement is GSM/GPRS, and more than 60% of today’s M2M modules (and a much higher proportion than this in Europe) are using 2G connectivity, with SMS most commonly used as a simple and efficient data communication service.
Traditionally it has been assumed that the use of UMTS and LTE connectivity will increase as more data is required by the final applications. For example, the average M2M module is forecast to generate 330MB of mobile data traffic per month in 2017, up from 64MB per month in 2012, and M2M connections will grow from 5% to 17% of all cellular connections over the same period. Comparatively higher ARPU users will require the much more expensive 3G and 4G devices.
Although certain vertical sectors, e.g. automotive M2M modules, will make more use of data for entertainment and infomatics, and M2M security devices for example will require real-time video, the low-cost 3GPP-defined M2M profile will still be prominent in device numbers, and to suit these applications M2M devices will require a lower cost profile. As more M2M modules are deployed, the reliance on 2G networks will pose a problem for operators who need optimal spectrum efficiency and consolidation of access technologies, since decommissioning of GSM/GPRS in the US is expected in 2016-2017, while new wireless operators without access to 2G or the relevant spectrum allocation may need to enter the M2M market. These operators would not be able to wait until 2017 for the mainstream LTE modem devices compliant to Release 12 or Release 13 specification, when cost reductions of MTC (machine type communication) devices in the LTE radio interface will have been implemented. Release 12 M2M devices will be able to identify themselves as ‘Category 0’ LTE UEs, and a number of specification adaptations, such as single RF chain, reduced bandwidth and peak rate, are estimated to reduce the cost of the device by up to 60%.
Even this 60% cost reduction may not be sufficient for the identified M2M profile, since LTE module costs are currently several times higher times than those for GSM/GPRS. Furthermore the specification work will not be ready until end of 2014, and mass market devices are not expected before 2016–2017. However some additional cost drivers such as module footprint reductions for Category-0 feature set and SoC device integration have not been included in the 3GPP calculation, so implementation-specific optimizations may actually achieve higher cost reductions even before this time frame, and the push from operators for pre-standard specific Release 12 implementations may accelerate the time-to-market for LTE M2M first deployments of this M2M profile.
Mainstream LTE chipset vendors have focused their development efforts on mainstream, full-specification modems for LTE, to include for example 2G/3G Inter-RAT, high throughput and VoLTE, and may not have the scale and motivation for early adoption of this M2M profile.
Meanwhile new non-3GPP cellular standards are emerging that are fully optimized for M2M and similar applications, and which promise to dramatically bring down the barrier of cost and power consumption. One of these is Weightless (www.weightless.org), which has a specially-designed radio interface and network architecture to specifically serve this M2M profile needs. Centralized scheduling, coverage enhancing spreading and very long frame timing are among the many design techniques employed which, irrespective of the white space or licensed frequency used, can dramatically benefit the M2M business case.
The best technology for M2M depends on the specific application. NextG-Com is committed to supporting both low-cost LTE solutions and emerging new technology standards including Weightless. Our LTE M2M Protocol Stack, ALPS-Lite, has been specifically designed to meet the needs of a low-footprint, low-cost M2M platform, with its modular architecture providing greater flexibility in terms of the features that need to be supported for specific M2M platform requirements. To address the requirement for minimal memory and minimal cost, ALPS-Lite is available with a highly optimized ASN.1 data stack and ultra lightweight SE-RTOS, specially designed for M2M applications. This reduces both dependency on third party software and licensing costs, and enables faster product development. Also it does not require a specific MCU or DSP for its execution, but can be ported to the same core as the application or LTE PHY to minimise cost.
NextG-Com is also a Core Member of the Weightless SIG, and has developed the technology blocks PHY, Protocol Stack, Test framework compliant to the Weightless standard, 1.0.
The next few years will be an exciting time for M2M, and providing the industry with the optimum technology for the widest range of applications will be crucial in ensuring that the ambitious growth forecasts will be achieved.