IoT in licensed spectrum: a game changer?


If you’re following the news regarding the Internet of Things, chances are you’ve come across some reading material on NB-IOT lately. After the launch of the ‘Mobile IoT Initiative’ by the GSMA last August to promote the use of licensed spectrum for the development of Low Power Wide Area Networks (LPWAN), the 3GPP announced in September that it had taken the matter in its hands. The standards body is indeed working on a standard (NB-IoT) that will enable LPWAN on radio frequencies usually used by mobile networks.

The NB-IOT standard will support three modes of operation:

  • ‘Stand-alone operation’, using dedicated spectrum (including GSM frequencies refarming);
  • ‘Guard band operation’, using unused resources in the guard band, that is to say the frequency range used to separate channels used for traditional communications;
  • ‘In-band operation’, using available resources within a communication channel.

By enabling the development of LPWAN in licensed spectrum, this standard may help mobile operators get back in the IoT race. Most of the existing LPWA networks take advantage of unlicensed frequency bands: industrial, scientific, and medical (ISM) bands. Both standard and proprietary protocols are being used in these bands, and the sustainability of an intense use is unknown (although collision avoidance techniques do exist to limit interferences).

The use of licensed spectrum may thus bring a solid alternative for critical IoT applications requiring reliable transmissions.
What’s more, if the mobile operator was to use resources in the 700 MHz and 800 MHz LTE bands, with remarkable transmission properties, the NB-IOT could also be able to cover wide areas from a single site.

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The most significant virtue of the NB-IOT is however its potential fast implementation:

  • mobile operators can use their own poles,
  • even though the standard has yet to be finalized, it seems that it could be implemented by means of a firmware change to the base station, and use existing radio heads and antennas.

The mobile operators could thus benefit from a wide footprint as early as day 0, and pose a credible threat to existing LPWAN operators: nationwide competing solutions could appear almost overnight alongside existing solutions of the crowded ISM bands.

In dense cities, where most of the IoT market is located, mobile operators may however have to use dedicated spectrum to ensure a better QoS (‘Stand-alone operation’ mode), instead of using scarce unused LTE resources. To use this ‘Stand-alone operation’ mode, mobile operators will however most likely have to negotiate with regulatory authorities, as licenses usually specify which technology is to be used on the band by the operator. In particular, refarming GSM frequencies comes at a cost. Mobile operators will have to keep this cost down, if they want to compete with LPWAN operators using ISM bands.

The NB-IOT is a threat current LPWAN operators shouldn’t underestimate. It is however unlikely that the associated costs (refarming, firmware upgrade, structure costs) allow for the development of a ‘low-cost’ solution such as the ones existing today. All in all, this standard may enable a complementary solution, for more critical uses of the Internet of Things.