IoT

IoT (Internet of Things) device can be explained as a small device with internet connectivity (over the Wi-Fi or Mobile Network) in the purpose of collecting and exchanging data. IoT device can be embodied with sensors (for measurement and collecting data), software and network connectivity which help them to communicate with other devices in the network and for remote control. So IoT network will be computing concept of all IoT devices.

Characteristics for IoT devices are long battery life, low device cost, low deployment cost, full network coverage and support to connect to a large number of devices. Maybe there will be more characteristics depending on the type of IoT Network and purpose.

Looking in the usage case categories we have a four groups Appliance, Public, Personal and Industry. 

In Industry there are logistic tracking (sensor data sent from tracking devices), asset tracking (user can get geographical location of his asset), Smart Agriculture (sensors for feeding). In the appliance, we have all kind of smart home application with short technologies but they need a gateway for connecting to the internet. In Personal group, we have wearables connected IoT devices related to health, fitness and wellness, smart bicycle (for bile rental companies - real-time tracking bikes), kids old person monitoring use case (real-time tracking kids and old persons) and so on. We also have operator reference cases like smart parking, smart metering.

The number of cellular IoT connections is grooving very fast and it is expected to reach 4.1 billion in 2024. Mobile operators have commercially launched 85 cellular IoT networks worldwide using Cat-M1 and/or NB-IoT regarding the last Ericsson Mobility report form November 2018. [1]

We can split IoT technology and devices in two big group eMTC (enhanced Machine Type Communication) also known as LTE Cat 1 and NB-IoT (Narrowband IoT). Through every group, we have evolution related with a release. Every release is specified by 3GPP group so please for more information visit the 3GPP group web page.

IoT technology is new, it exists only for 3 or 4 years. The first IoT devices (a device that satisfies all characteristics of IoT mentioned in beginning this article) are developed in Release 13. 

Below we can see the differences in performance for these two types of IoT Technology in Release 13.

eMTC Technology has higher BW (Bandwidth), higher order modulations and with that is coming higher throughput. It has also voice so for that it needs lower latency but is more expensive. Both IoT Technology can be integrated on LTE network and they will use resources form the local host LTE cells. One of the resources is PRB (Physical Resources Block) and eMTC with higher BW will use more PRBs than the NB-IoT. eMTC has 1.4 MHz BW and it will use 6 PRBs and Nb-IoT has 180 kHz BW so it will use only one PRB. Both technologies can work In-band with LTE but NB-IoT can also work in Gard-band with LTE without using any of PRB resources and like stand alone in GSM spectrum. But we will say more about that in the future section.

In Release 14 they have much better performance with some new features. In every new Release, there are improvements in functionality, better chipsets with some new features. The best way to track the improvements and Release is looking at services and products from companies who are producing IoT devices and services like Rohde Schwarz, Qualcomm Technologies, Keysight Technologies, and others. We can see from Rohde Schwarz web page a new feature in the Release 14 for NB2 –IoT.

It is also good to follow the 3GPP IoT page for more specifications of every release. Below we can see some of the IoT (eMTC and NB-IoT) devices. The devices are available as a complete product or like a module part that can be connected in the final IoT device. In almost all devices it is possible to change antenna with larger and better antenna gain. The SMA connectors are used for antenna connections.

In this article, I will focus more on NB-IoT technology because it is more interesting and more involved in our lives.

NB-IoT (Narrowband IoT)

Nb-IoT network is a Low-Power Wide Area Network that is using cellular telecommunication bands for connecting with wide range devices and services. From the 3GPP specifications, NB-IoT has 180 kHz BW, single antenna, they are a half duplex.

NB-IoT device transmitting power is 20dBm (100mW) or 23 dBm (200mW). The maximum coupling loss is 164 dB. In Urban area, it should have deep penetration in the buildings and in rural area long range until 15Km.

Below is the table with an example of Uplink link budget( from NB-IoT devices to base station).

NB-IoT can work in three types of mode looking at the frequency band (In-band, Standalone and Guard-band).

NB-IoT In-band cell is using PRBs from the host LTE cell (carrier) and Guard-band NB-IoT cell is using unused PRBs from LTE cell (carrier). Standalone NB-IoT cell doesn’t require an LTE host but it is using resource form digital/Baseband unit.

It is good to understand why Resource Blocks (or is we are looking in 1ms TTI, PRB Physical resource Block that contains two RB) are so important for Capacity and Throughput and why we so care about PRB consumption. For that please look at my last article Correlations between PRB, TTI, CQI Cell & User Throughput. 

Below is some high view of NB-IoT cell impact on Base-band (digital) unit, Radio Unit, CPRI interface, antenna equipment and Cell/User throughput on host LTE cell. There is deeper impact analysis with NB cell (because NB-IoT cell needs to be defined also) and host cell KPIs, but in this article I will not go deeper into NB-IoT Capacity analysis.

How does the NB-IoT device work?

We can look into NB-IoT device on the public recycling bin. It is standard recycling bin used for cans (metal), glass or general. Let’s integrate our NB-IoT device on that bin. We will need a sensor that is telling us is the bin full or not. This sensor can be integrated into Nb-IoT device, or it can be connected with wire on Nb-IoT device. The Nb-IoT device has a battery, small processor, RF module, eSIM/SIM and antenna or SMA connector to connect to the external Antenna. Also depending on the type of IoT product it can have more things like sensors, USB connector etc. Most of the time the device will be in sleep mode (there are PSM and eDRx main features for power consumption). It will wake up only ones per day to check if the bin is full, and if it is, it will set up connections over Control plane and sent only several bits of information. The same signal will be sent several times and using the nature of electromagnetic waves (Constructive Interference) it will easily propagate through reinforced concrete walls. Also multiple repetition will extend coverage (I will explain the nature of electromagnetic waves in my future article.)

The most important features of Nb-IoT devices are Power Consumption Features (PSM and eDRx) and Coverage Enhancement Feature (multiple numbers of repetition for extending coverage). (Also all this features will be explained in my feature article.) There are more small things to need to be explained, but this is a high review of IoT.

Descriptions:

eSIM (Embedded SIM) is a flexible solutions for SIM, SIM is already intergrade in to device and there is no need for physical SIM card. It contains with more ICCID profiles with different MSISDN and IMSI but only one profile can be activate at time. Profile can be downloaded and intergrade on the IoT device. With eSIM IoT device is flexible for changing operators and countries.

Control plane optimization is simple connections (there are no data radio bearers only Signalling radio bearers) from eNodeb to MME and from MME over SGW to PGW (using IP data delivery-packets) or to the Service Capability Exposure Function (SCEF) (using non-IP data delivery-packets).

Power Consumption Features, PSM -Power Saving mod and eDRx - extended Discontinuous reception. This features can be working together providing better power consumption. Also it is possible to manual set up PSM timers ( T3412, T3324) as a recommendations timer values on the NB-IoT devices and Mobile network will accept this new timers values if the values are in sported range of Mobile Network feature .

References:

•Ericsson Alex library

•Rohde Schwarz –Let’s talk IoT https://www.youtube.com/watch?v=VcJtkBu0deU , Narrowband Internet of Things Whitepaper

•Keysight Technologies –CAT-M & NB-IoTDesign and Conformance Test

•Qualcomm Technologies –Leading the LTE IoT evolution to connect the massive Internet of Things

[1] Ericsson Mobility Report November 2018