The 3GPP has proposed a narrowband version of LTE for inclusion in Rel. 13, which will probably reach finalization in early 2016. Known as Narrowband IoT LTE, this would mainly target IoT applications with very low data rate requirements.  Narrowband IoT LTE would be approved in addition to LTE Cat. 1, Cat. 0, and LTE MTC, which are all low-rate, lower-cost versions of LTE suitable for M2M.  Narrowband IoT would support even lower data rates and lower power consumption.

Technical details under consideration:

• 180 kHz bandwidth for UL and DL (compared to 20 MHz for full LTE and 1 MHz for LTE MTC).
• DL: OFMDA with 15 kHz and 3.75 kHz sub-carrier spacing.
• UL: FDMA or GMSK, with possible SC-FDMA option.

Narrowband IoT LTE would provide improved indoor coverage and could support a massive number of low throughput devices, especially those not very sensitive to latency.  The narrow bands would allow very low-cost chipsets and devices, and very low power consumption for extended battery operation, probably allowing a year or more of use with a large button cell or small alkaline battery in many applications.  The standard could be deployed in existing LTE bands using resource blocks within a normal LTE carrier, or in the unused resource blocks within a LTE carrier’s guard-band. Stand-alone deployments in narrow slices of dedicated spectrum would also be possible.

Given that much of the spectrum used for legacy GSM is licensed in relatively narrow channels, narrowband IoT could be very useful to some wireless operators for refarming GSM spectrum.

Narrowband IoT LTE appears to be a response to huge operator and municipality interest in low-rate, low-power wide area networking (or LPWAN) for M2M and IoT, and a response to proprietary air interfaces for LPWAN that have recently started to gain momentum:

• SIGFOX raised $115 million in funding earlier this year from Telefonica, GDF Suez, NTT DoCoMo Ventures, SK Telecom, Air Liquide, Elliott Management, and Samsung.SIGFOX plans to roll out LPWA across 60 countries using the 868 MHz (Europe) or 900 MHz (US) ISM bands.
• LoRaWAN (aka LoRa or Long Range Wide Area Networking), was originally developed by Cycleo SAS, later acquired by SEMTECH.  Dutch operator KPN plans to introduce LoRa this year.  The proprietary air interface operates in the 433 MHz, 868 MHz or 915 MHz bands using a form of chirp spread spectrum modulation with an adaptive link layer.
• Plextek offers its UNB (Ultra Narrow Band) mainly for industrial telemetry and automatic meter reading.  The air interface transmits at only 62.5 kbps over the 868 MHz or 915 MHz ISM bands.

Narrowband IoT LTE will have a big advantage over these in that it will soon have global support over existing LTE cellular networks.  Applications envisioned for Narrowband IoT LTE include metering, environmental & industrial monitoring, object location tracking, e-health, wearables and sensors.  Narrowband IoT LTE would compete with other LPWAN air interfaces, but could complement local area wireless mesh networks using ZigBee, Bluetooth Smart or Z-Wave for example.

The only concern we have heard so far is that including Narrowband IoT LTE in 3GPP Rel. 13 could delay the 3GPP release.  Eager chip suppliers note that LTE MTC is already well defined, and provides low cost, low power consumption and coverage gains compared to LTE Cat. 0 and above, so perhaps the cellular industry should move Narrowband IoT LTE to Rel. 14.

3GPP members supporting Narrowband IoT LTE include Alcatel-Lucent, Alcatel-Lucent Shanghai Bell, AT&T, CATT, Deutsche Telekom, Ericsson, Huawei, HiSilicon, Intel, Interdigital, LG Electronics, Nokia Networks, OPPO, Panasonic, Qualcomm Incorporated, Samsung, Sony, SouthernLINC, Sprint, Telecom Italia SPA, Telefonica, TeliaSonera, T-Mobile US, u-blox, US Cellular, Verizon, Vodafone and ZTE Corporation.