# NB-IoT

## Summary


Narrowband IoT (NB-IoT) is a cellular low-power wide-area (LPWA) connectivity standard that enables IoT devices to send their data directly to the cloud without a gateway in between. By low power, we mean that IoT devices can run on battery for 10+ years. By wide area, we mean that cell coverage is improved so that, for example, smart meters in basements can connect to the network reliably. 

Traditional cellular standards were focused on either voice or bandwidth-intensive low-latency data applications. These are not scalable for IoT due to reasons of cost, coverage, device density and power. NB-IoT reduces complexity, limits bandwidth, and caps maximum data rates. This is possible because IoT sensor devices are tolerant to delays, require minimum mobility and operate at low data rates.

## Discussion

### What are some use cases of NB-IoT?

In general, applications that send small amounts of data occasionally from sensor nodes that run on batteries, of limited mobility and installed in remote locations will benefit by using NB-IoT. NB-IoT fills the gap between cellular technologies such as 3G/4G and short range technologies such as Wi-Fi/ZigBee/Bluetooth. In other words, it solves the last-mile problem for IoT devices. Applications that require high device density (50,000 device per cell) can use NB-IoT. 

Smart metering, asset tracking, wearables including health monitoring, facilities management, intruder and fire alarms, smart dustbins, smart street lighting, connected appliances at home or factories... these are some use cases of NB-IoT. 

GSMA has published detailed case studies on smart metering, smart parking, wildlife tracking and environmental monitoring. Likewise, successful implementations of smart metering, smart parking and smart agriculture have been reported. 


### What are the techniques enabling NB-IoT?

Since sensor nodes require low data rates, bandwidth is reduced to 180 kHz. Many of the supported bands are in sub-GHz so that better range is obtained. Range is also increased by repeating transmissions. Further reduction in device cost and complexity is due to supporting only FDD, single antenna (no MIMO) and half-duplex mode.

Multitone uplink is optional. Single-tone uplink uses the power amplifier more efficiently. More devices can be supported within the same cell. 

For lowering power requirements, Release 12 introduced both *Power Saving Mode (PSM)* and *Discontinuous Reception (DRX)*. With PSM, device is registered with network but can go into deep sleep for up to 12.1 days. Device can wakeup to send data or do a Tracking Area Update. With DRX, device need not monitor control channels most of the time. Release 13 improves this with *extended DRX (eDRX)* in which the device can go to sleep for up to 3 hours. 

For unscheduled mobile terminated data, DRX is better. DRX also avoids unnecessary signalling, whereas PSM would still require a TAU even when device has no data to send. 


### What are the key parameters of NB-IoT?

In Release 13, NB-IoT is supported in many bands, many of which are sub-GHz. NB-IoT uses only one physical resource block (PRB) of 180 kHz. Coverage is better than GPRS by 20dB. Support is only for FDD, half-duplex without any MIMO. Since sensor devices will mostly be sending data and occasionally receiving commands, uplink data rate is higher than downlink. Uplink can be single-tone or multitone. 


### What are the modes in which NB-IoT can be deployed?

NB-IoT has three modes:

    + **In-band Mode**: This is easiest for operators since no changes to hardware are needed. LTE spectrum is used. Many operators in Europe have adopted this. Internal interference (inter-PRB) can be a problem and this has to be managed effectively.
    + **Guardband Mode**: NB-IoT is served by the same eNodeB that serves the LTE cell, thus sharing the power. There's no spectrum cost since operation is in the guard band. Interference is better managed than in in-band mode.
    + **Standalone Mode**: By refarming unused GSM bands, NB-IoT can be deployed in these bands. Frequency planning incurs a cost. New RF modules are needed but more power may be available since this is independent of the LTE cell.

### Who are the chipset vendors for NB-IoT?

Among the major vendors are ARM, Altair Semiconductor (acquired by Sony), Huawei, Intel, Qualcomm, Sequans Communications and Nordic Semiconductor. ARM is a relatively new entrant to this space. It's Cordio-N IP includes Cortex-M33 that could run both the stack and application. 

Industry's design approach seems to be a dual-mode chip for both Cat-M1 and Cat-NB1. This is seen in Altair's ALT1250, Intel's XMM 7315, Qualcomm's MDM9206, Sequans' Monarch and Monarch SX, and Nordic's nRF91. . One reason for this dual-mode approach is the uncertainty of NB-IoT's adoption due to presence of LTE-M. 

MediaTek has integrated NB-IoT and GSM/GPRS into a single SoC MT2621 for IoT deployment in a GSM/GPRS network that can later be migrated to NB-IoT. The SARA-R4/N4 series from u-blox also dual-mode. 

At module level, Sierra Wireless supplies modules that use Altair's ALT1250. Murata will supply modules that integrate ALT1250 and MCUs from STMicroelectronics. 

Nick Hunn has given a thorough discussion of NB-IoT chipset landscape as of March 2018. 


### What are some considerations when designing for NB-IoT?

High levels of SoC integration are seen for example in Monarch SX that includes an ARM Cortex-M4, an ARM-based sensor hub, a graphics controller, and a media processing engine. Indeed, it's been said that while firms initially focused on making thin modems, the current battle is about SoC integration. Unlike the Monarch SX, Altair's ALT1250 doesn't have an MCU but includes GPS. 

It's been said of NB-IoT SoC that, 

> Design efforts need to be directed at optimizing power and cost rather than optimizing performance.

Cache memory sub-system involves a tradeoff between performance and area. The use of hardware accelerators are not preferred at NB-IoT's low data rates. 

With regard to the protocol stack, an optimized memory footprint can avoid the use of external flash and hence save on both cost and power consumption. Optimal RAM usage will most likely be achieved by designing from scratch rather than downscaling from legacy LTE design. Single-core solutions that integrate service layer, application and layer 1 is now possible, due to half-duplex operation and relaxed delay constraints. Applications must manage sleep and wakeup cycles for power optimization. 


### Could you compare NB-IoT against other LPWA technologies?

LPWA technologies competing with NB-IoT include the following: 

    + **LoRa**: By early 2018, LoRa had 60+ public networks and 350+ ongoing trials in 100+ countries. LoRaWAN is a networking stack that uses LoRa. Symphony Link and Haystack are alternatives that uses LoRa.
    + **SigFox**: Started in France, by September 2017, SigFox was deployed in 36 countries with national coverage in 17 of them.
    + **RPMA**: US company Ingenu has used *Random Phase Multiple Access* technology to provide its Machine Network in some areas of the US. The technology is now available for deployment outside the US.
    + **Weightless**: Weightless SIG has standardized three variants: Weightless-N, -P and -W. Weightless-P also uses licensed spectrum.NB-IoT has the advantage that it builds on existing cellular networks and enables global roaming. It also uses licensed spectrum implying that interference is better managed. As of February 2018, NB-IoT had 41 launches by 23 operators in 26 countries. 


### Could you compare NB-IoT against other cellular IoT standards?

There are two alternatives that 3GPP provides:

    + **LTE-M**: LTE-M is also known by the name *enhanced Machine Type Communications (eMTC)* or *LTE-MTC*. UE category that supports NB-IoT is named *Cat-NB1*; the same for LTE-M is called *Cat-M1*.
    + **EC-GSM-IoT**: *Extended Coverage GSM-IoT* optimizes GSM networks for IoT. Upgrade costs are expected to be minimal but there's also doubt if market will require this technology.LTE-M operates in LTE spectrum while NB-IoT can be deployment in three different modes. While LTE-M is a simplification of LTE, NB-IoT is really DSSS modulation. For operators, LTE-M is only a software upgrade from LTE but NB-IoT will require infrastructure upgrade. 

While NB-IoT is suited for low data rate applications, LTE-M targets content rich applications as well. LTE-M is suited for higher data rates and mobility than NB-IoT can provide. For example, LTE-M is suited for wearables while NB-IoT is suited for smart metering. Note that the 200+ kbps peak data rates in NB-IoT are at Layer 1 and peak throughputs are much lower. 


### Are there any concerns about NB-IoT?

LoRa and SigFox have been deployed in many countries. For example, Netherlands and South Korea both deployed nationwide LoRa networks in September 2016. The Dutch KPN commented that they chose LoRA "based on quality, technology readiness and industry adoption." NB-IoT is therefore a late entrant in the LPWAN space. If it has to succeed, it has drive down costs; get the pricing right; devices have to be interoperable. There have been concerns of interoperability between Ericsson and Huawei devices. 

NB-IoT Release 13 is available in 14 bands and Release 14 added another 4 bands. This may lead to market fragmentation. Support for all bands may result in higher cost and power consumption. From the point of power availability at eNodeB, either eNodeB has to be upgraded or NB-IoT has to resort of retransmissions. The former incurs cost while the latter drains end-device battery. 

On the business side, business models are far from clear. Will people buy NB-IoT product and separately subscribe to a connection? Or will NB-IoT offer end-to-end services or solutions including perhaps data analytics? Issues of data privacy and regulations also matter. 


### Is LTE-M competing against NB-IoT?

NB-IoT was created because LTE-M was seen too 'broadbandish' to compete against SigFox or LoRa. However, differences between LTE-M and NB-IoT are no longer seen to be significant. If LTE-M achieves high volumes and drives down costs, then this could be bad news for NB-IoT. LTE-M is a simple software upgrade to the RAN while NB-IoT is perceived to require new infrastructure and a new core network. France's Orange instead uses a combination of LTE-M and LoRa. In March 2018, AT&T reported that it's deploying LTE-M but is keeping an eye on NB-IoT developments. 

Others believe that both will coexist since their use cases are different. As of June 2017, operators worldwide are showing interest in both technologies. From the standardization perspective, both technologies have a roadmap that include single-cell multicast (for over-the-air upgrades), enhance device positioning (for asset tracking) and TDD support in NB-IoT. 


### What support can developers expect in the NB-IoT space?

*GSMA NB-IoT Forum* is promoting NB-IoT and membership is open to non-GSMA members as well. In April 2016, Vodafone and Huawei set up the world's first NB-IoT Open Lab as a testbed for manufacturers and app developers. Since then many others have been set up worldwide. 

Since 2012, Deutsche Telekom has been running an incubator named hub:raum to support early stage startups. As part of WARP NB-IoT accelerator program, hub:raum selected 12 startups whose ideas will be piloted to customers around December 2017. 

## Milestones

2014

A new study item titled "Cellular System Support for Ultra Low Complexity and Low Throughput Internet of Things" (GP-140421) is proposed in 3GPP. This kickstarts the work on NB-IoT. The document states that 3GPP M2M devices use legacy GPRS but there are competing technologies that provide better coverage and efficiency at lower cost. Document proposes looking into evolving GERAN plus designing a new access system. 

2015

3GPP Release 12 introduces Cat-0 UE category. This is targeted towards the IoT market. Neul releases the first pre-standard NB-IoT chip named Iceni. The same year u-blox uses Iceni to produce the first NB-IoT module. Huawei later acquires Neul. 

Jun  
2016

3GPP completes the standardization of NB-IoT, which is part of Release 13 (LTE-Advanced Pro). Further changes to the specifications can be done only in a backward-compatible manner. 

Oct  
2016

World's first commercial NB-IoT network goes live in Deutsche Telekom's German and Dutch networks. The first application is a smart parking system. Deutsche Telekom had launched a pre-standard NB-IoT on a commercial network back in October 2015. 

Jun  
2017

Enhancements to NB-IoT is introduced as part of 3GPP Release 14. These include improved positioning capabilities, enhanced Multicast DL transmission, new band and power class support, mobility enhancements, support of higher data rates, and non-anchor PRB enhancements. UE category Cat-NB2 is introduced. 

Dec  
2020

A GSMA report notes that 111 operators have deployed NB-IoT networks, of which 34 operators have also deployed LTE-M networks. Whereas 32 countries have both NB-IoT and LTE-M networks, 28 countries have only NB-IoT networks. Among NB-IoT compliant devices, 347 Cat-NB1 devices and 63 Cat-NB2 devices are now available in the market.