• Command-response traffic (triggered reporting), having latency of 10 seconds.
  • Exception reported by IoT module having latency of 3-5 seconds.
  • Periodic reports or Keep alive, insensitive to latency
In the near future, it is expected to enable a new use case as well
  • Ultra-low latency, command-response 'conversational' traffic having latency as low as a millisecond for tactile applications.
  On comparing the internet of things world with the present day internet, one thing that comes our clearly is that there will be a plethora of devices which will be asymmetric in their capabilities, thus there is a need to look at this diverse geometry and discuss a diverse connectivity portfolio. We are also talking about devices/things with specific use cases; thus a generic approach at IoT platform design at the device side could fail miserably. We can say that no one size fits all in this case – being addressed as ‘device profiles’ by some of the platform vendors.
  IoT necessitates the need for a low power solution, so that there is no need to worry about power backup and battery replacement hurdles during the lifecycle of the device. IoT though is a buzzword these days, the early deployment dates back to 80’s with proprietary connectivity solutions or through either industry alliances or standard developing organizations (SDO’s). Connectivity technologies were developed within the leading SDOs, i.e. the IEEE, ETSI, 3GPP, and IETF. In the current era, prominent low power short-range solutions are available including Bluetooth and IEEE 802.15.4 (promoted by Zigbee alliance). However the biggest misconception has been the understanding of low power and associated costs. While Zigbee or other short-range communication can keep the power consumption relatively low, the biggest drawback is the range, which necessitates the need for gateway components or aggregators in the system. This also requires additional cost in terms of management and maintenance of such components and services, thus while the chip/SoC cost could be as low ~ 5 USD, the total cost could be around ten times ~ 50 USD. Another way to look at the low power requirement is to view it as a holistic problem around energy, which means that we can intermittently transmit at high power (thereby achieving range), but keep the transmission time very less, thus the equation energy =  Power * Time, gives us a low energy requirement. This can help us remove the need of intermediate gateway components, and yet achieve a low energy target. This was clearly understood by IEEE 802.11 group, and they came up with a low power version (enhanced duty cyles) - 802.11ah to introduce low-cost connectivity in unlicensed bands. It is currently being developed to enable low-cost long-range (up to 1km) connectivity with high spectral and energy efficiencies. However it won’t be able to deliver the required reliability, for some of the IoT use cases, as there is neither a guaranteed QoS support, nor enough tools to combat severe interference in unlicensed bands.
   Another class of IoT connectivity technology has emerged lately termed Low-Power Wide Area (LPWA), which operates in unlicensed spectrum and supports low data rates with relatively smaller daily traffic volumes. Some of the famous ones are technologies by SigFox, LoRA, Neul (to name a few), which are usually non-compatible and proprietary alternatives. There is a clear advantage in using LWPA from time to market perspective, as we keep hearing announcements from several operators and telcos deploying trial networks using one or the other form of LPWA. Limitations of asymmetric link budgets between the uplink and downlink directions arising due to regulation on unlicensed spectrum poses a challenge for long range communication (explained in [2]). It also suffers due to scalability issues to support a massive number of devices with LPWA technology on unlicensed bands.
   Cellular technologies particularly LTE gives lot of advantages from coverage, cost, availability and ease of deployment perspective. We have learnt that in addition to the existing LTE MTC work item which defines Category-0 devices; with the advent of NB-IoT (narrow band IoT) a new way to slice the technology and deployment will come up this year. The technology can be deployed “in-band”, utilizing resource blocks within a normal LTE carrier, or in the unused resource blocks within a LTE carrier’s guard-band, or “standalone” for deployments in dedicated spectrum. NB-IoT is also particularly suitable for the re-farming of GSM channels. Customer pilots using pre-NB-IoT technology are already underway. Pre-commercial deployment is expected during the second half of 2016, with commercial rollout from early in 2017.
   While there are several connectivity solutions available for catering to the IoT market, there will be no clear winner for the same due to varied deployments and asymmetric capabilities of the ‘things’. We believe that while LPWA technologies can be used to enter the market early, a clear established solution will be using cellular due to associated accessibility and ease of deployment/management of devices and use. In a way, entering late into this market will give cellular a clear advantage in understanding the varied requirements for IoT (low latency/high latency, static/mobile, low power/extended coverage etc.). We also note that cellular standards in the current form also support unlicensed accesses (LTE-LAA), and short range communication (LTE D2D or side link). Thus, a wide profile for connectivity could be made available for IoT solutions. Provided, there is some focused effort to also standardize and establish LTE for IoT in unlicensed band and to enable D2D for IoT profile – we see a clear winner here.
Note:Some of the thoughts presented here are well established in the available literature on IoT or M2M, and has been quoted and re-quoted by several speakers at keynotes of conferences and summits around the world. The authors would like to share their deep regards for the work by Prof. Mischa Dohler and team, and the associated IoT MOOC by Mischa Dohler, which helped them in building and ratifying their understanding. (Please check out the references at the end).
References:
[1] The Internet of Things:  Learn how IoT works, and how to create a successful product or company using it, with this free online course. Educator – Mischa Dohler <https://www.futurelearn.com/courses/internet-of-things/1/steps/54817>
[2] Understanding the IoT Connectivity Landscape – A Contemporary M2M Radio Technology Roadmap, Sergey Andreevy, Olga Galinina, Alexander Pyattaev, Mikhail Gerasimenko, Tuomas Tirronen, Johan Torsner, Joachim Sachs, Mischa Dohler, and Yevgeni Koucheryavyhttp://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7263370&tag=1
By : Diwakar Sharma & Tushar Vrind, Samsung Semiconductor India R&D, Bangalore