Cellular Narrow Band IoT- using LTE

Mohit Luthra, Rahul Atri, Mehdi Sadeghian,SukhvinderMalik , PreetRekhi October 11, 2016
Long Term Evolution for IoT
(Narrow Band LTE-Cellular IOT)
A Short Note on Design, Technology and Applications
1. Introduction to IoT
The Internet of Things (IoT) is a network of physical objects, machines, people and
other devices that enable connectivity and communications to exchange data for
intelligent applications and services. These devices consist of smartphones, tablets,
consumer electronics, vehicles, motors and sensors which are all capable of IoT
communications.
The IoT allows objects to be sensed and controlled remotely across existing network
infrastructure, creating opportunities for direct integration between the physical and
digital World resulting in improved efficiency, accuracy and economic benefits.
There is an expectation that IoT communications will present tremendous
opportunities for creating new devices and applications in the coming decade.
IoT communications will undergo unprecedented growth in the coming five years;
it is predicted that over 50 billion IoT devices are expected to be connected with as
much as US$8.9 trillion in annual revenue by the year 2020. With increased
pervasiveness of mobile broadband, cellular connectivity is becoming even more
valuable as an important access methodology for IoT. A significant part of IoT
communications are planned over cellular networks.
According to GSMA studies and forecasts,cellular IoT are predicted to account for
over 10 percentof the global market by 2020. Cellular technologies are already being
used for IoT today in severaluse cases and are expected to be used even more in the
future as these use cases have a need for ubiquitous mobility, resilient networks,
robust security, economic scale and/or communications independent using customer
DSL, fixed lines, etc.
Introduction to Internetof Thing Page 1
Table of Content
1. Introduction to IoT
2. IoT Evolution and Market
3. IoT Applications and Its
Requirements
4. IoT Network Architecture and
Requirements
5. Access Technology Available
for IOT
6. Evolution in 3GPP Standards
to support IoT
7. Narrow Band LTE Technology
8. Requirements, Challenges, and
Solutions for IoT
9. NB-LTE Physical Layer
10. NB-IOT Call Setup and
Procedures
11. Summary and Conclusion
12. References

Mohit Luthra, Rahul Atri, Mehdi Sadeghian,SukhvinderMalik, PreetRekhi October 11, 2016
The challenge for the cellular industry now is to unlock the value of this interconnected web of devices in a manner that is
secured, flexible, low power and easy to provision, manage and scale while delivering robustness and acceptable latencies in
performance. The goal is to identify a framework of promising solutions and cover a set of innovative approaches and
technologies as building blocks to meet these challenges.
In this paper authors will discuss about evolution of Internet of Thing, its architecture, its requirements, application and 3GPP
evolution to support IoT.
2. IoT Evolution and Market
Majority of industries recognize that M2M and IoT has become the key growth opportunities for telecommunication service
providers and enterprises of various sizes in the next decade. Many of us may have questions about M2M and IoT, which can
be:
 How IoT started?
 What are the key market drivers for IoT?
 What is the market size?
Evolution of IoT started with consumer devices where Mobile Handsets, Tablets, Computers are connected with the networks
and sharing the information among eachother.The first phase of IoT is related to Home automation and control. A short example
is that home appliance is controlled using mobile. During this phase the normal device i.e. Mobile Phone no special devices are
required.
Figure # 1: IoT Evolution
In the next phase of IoT is expended to the industry automation, Video surveillance and Health Monitoring types of applications.
This phase of IoT is known as machine type communication where sensor collects the data, sends it over the network to remote
server where it is being processed.
The current phase of IoT is where everything is connected to everything and this phase is known as Internet of Everything. To
support such kind of connectivity special devices, networks are required. Many of such devices placed indoor so strong indoor
coverage is needed. Another there might be billions of devices, so the network should have large capacity. Device for Internet
of Everything does not require high data but these requires long battery life.
IoT market is expectedtrillion dollar market and it is setfor aggressive growth in coming future. The totalIoT market is estimated
to be 30 billion connected devices by 2025 a researched published by Machina Research,May 2015. Fixed and short range
communication will be a significant part of IoT communications although cellular technology is forecasted to grow as the
technology of choice for IoT applications as well, 3GPP and 3GPP2 is working for standardization. These billion connected
devices can covered market of Health Care, video and surveillance, retail, transportation and utilities sectors. Rapidly growing
IoT adoption in different industries presents significant market opportunities for telecom operators. IoT connectivity revenue is
expected to increase from US$6 billion in 2011 to more than US$50 billion by 2021.
IoT Evolution and Market Page 2

Figure #2: Billion global connections, 2015-2025 (Machina Research, May 2015)
The key IoT market drivers for telecom operatorand larger enterprises is a generation of new revenue stream,tremendous volumes
of devices to be deployed, and a drastic increase of operational efficiencies required for operation of IoT solutions. From a business
perspective, the adoption of IoT is driven by factors such as:
 Optimization of utilization of physical and financial assets
 Predictive maintenance and industrial control
 Asset Tracking and Management
 Smart Metering
 Differentiation of products and services to increase customer satisfaction through connectivity and Devices
 Tracking Weather condition for shipping companies
 Proactive Monitoring of Diesel in Electric Generator
 Garbage Bin Empty and Full Status and location tracking
 Transformation of customer engagement
 Relocation Services
 Gym Training Consultation analyzing data captured by wearable devices
3. IoT Application and Requirements
Based on the requirements for connectivity, many naturally see IoT in the domain of the Mobile Network Operators (MNOs),
although connectivity is a readily available commodity and therefore,low value. In addition, some IoT use cases are introducing
different requirements on connectivity, both economically and technically (low power consumption, limited traffic, mobility or
bandwidth), which means that a new type of connectivity option is possible to maximize efficiency and Return of Investment of
such use cases; for example, Sigfox or LoRA, LPWAN.
However,the value creation is less on connecting devices and having them available, but rather on collecting their data,validating
and analyzing, mixing it with other sources, and finally, exposing it to the applications that enable enterprises to derive business
value from these services. Many use applications will be successful and benefit from cellular 3GPP technology connectivity.
The requirements for this application is actually vary from application to application. A common list of requirements for IoT use
application for Cellular Technology is listed:
 Data Rate for Both uplink and downlink
 Mobility Requirement of the IoT device where the application is used
 Latency response required for the application
 Number of reports or readings that are required from the IoT device for the corresponding application
 Battery requirements for devices that are necessary for a given application
 Security requirement to preserve the content
LTE-Advanced technology, the chief vehicleof 4G cellularconnectivity,started to and will continueevolvingto providenew features that
IoT Applicationand Requirements Page 3

A generalized list of application with above requirements is given table below.
Table#1: IoT Applications with Requirements
4. IoT Network Architecture and Requirements
The Internet of Things (IoT) is a network of physical objects, machines, people and other devices that enable connectivity and
communications to exchange data for intelligent applications and services. These devices consist of smartphones, tablets,
consumer electronics, vehicles, motors and sensors that are all capable of IoT communications. The end to end IoT network can
be seen in figure # 3. IoT network is consist of following;
 Connected Device and Short Range Access
 Access network and Data Gateways
 Transport Core Network
 IoT Connectivity Platform
Connected Devices/Short Range Access
In an IoT solution, a machine like camera,bicycle, wearable or Car is embedded with a communication device that connects to
a network, that enables these machine to interact with a cloud based connectivity platform and applications on other devicessuch
as smart phones and tablets, or other various machines.
The communication device may be connected to a short range access network such as WiFi, or Bluetooth or directly to a wide
area Accessnetwork like 3G/4G cellular network. The Access Network may be connected through a wireline Core network. The
Access Network enables the local communication between the connected devices and bridges it to Connectivity Platform.
LTE-Advanced technology, the chief vehicleof 4G cellularconnectivity,started to and will continueevolvingto providenew features that
supporta range of high and lowperformance and cost-optimized IoT device categories.Such devices also supportextended coverage for
challenginglocations,lowenergy consumption for applicationsrequiringlongbattery lifeand optimizations to supportvery large
numbers of devices per cell.LTE-Advanced technology, the chief vehicleof 4G cellular connectivity,started to and will continueevolving
IoT Network Architecture and Requirements Page 4

Mohit Luthra, Rahul Atri, Mehdi Sadeghian,SukhvinderMalik ,PreetRekhi October 11, 2016
Figure # 3: IoT Network Architecture
Access Network
In IoT, the access network is often wireless. The choice of the network depends on the application requirements such as mobility
requirement, commercial or private networks are desirable. The convenience of the mobile cellular network is driving wide area
IoT applications towards mobile operator networks. In mobile networks, the radio access network (RAN) is shared across
consumer and IoT traffic. Mobile networks have been designed for low latency, high throughput consumer traffic and not
optimized for IoT. However, since 2011, 3GPP has been defining several IoT/MTC optimizations to 2G/3G/4G for extending
coverage for low throughput devices deployed deepwithin buildings such asin basementswhich consequentially reduce signaling
traffic and device cost and improve battery life. Technologies like EC-GSM, NB-GSM, LTE-M, NB-IOT is resulted of this 3GPP
efforts.
Wireline Core Network
Core network functions are not defined separately for IoT, a large amount of effort has been made and will continue to be made
to optimize the 3GPP core network for IoT applications. The application of NFVand SDN technologies in the mobile core network
will provide new capabilities to support a variety of use cases including IoT more efficiently.
NFV and SDN technologies allow a modular and software based core network architecture where the core network can be
dynamically ‘sliced’ and ’scaled’ based on use cases,types of devices and other parameters. It is conceivable that a network
operator can create mobile core instances suitable for IoT rather than one core network that has to fit all of the current scenarios.
The combination of these new technologies will result in an access agnostic and software-based next generation mobile core
network that will support the diverse use cases of telecommunications in the near future.
Connectivity Platform
Low average revenue per user associated with IoT and some unique requirements like need for bulk provisioning have driven
mobile operators to reduce their operations cost by deploying a platform for handling SIM pre-provisioning, provisioning,
activation, deactivation and self-diagnosis of device communication issues. The requirements for IoT have required substantial
flexibility depending on the specific enterprise and the number and usage of devices. The connectivity platform typically includes
a configurable systems that connects to the operator’s traditional charging systems. The connectivity platform also includes
communications server that performs, stores and forwards message routing and protocol translation, essentially gathering data
from devices and making them available for applications. In many cases the servers included in the application platform. The
connectivity management platform includes device management functions for firmware upgrades, configuration and diagnostics,
and application life cycle management.
IoT Network Architecture and Requirements(Continue….) Page 5

The platform also includes the serverfor processing data and a database forstoring devices. Application ProgramInterfaces(APIs)
in the form of a software development kit are provided to easily use the services of the platform. Standalone applications or
applications running on the platform are sometimes integrated into enterprise backend systems and users.
To support IoT application Devices and Network need some special requirements. Some of these are listed below:
Devices Requirement
 Smart Sensing
 Low Cost Devices should be less than $5
 Long Battery Life in order of 10 Years
 Extreme low data rate support
Network Requirement
 Extended Coverage link budget similar GPRS about 164 dB Maximum Coupling Loss (MCL)
 Support for Massive no. of Device Connectivity requires High Cell Capacity (40 devices per household, ~55k devices
per cell)
 Low data and low latency support (few kbps and < 10 second)
 Low Deployment , Operation Cost and Very High Network Availability
 Dynamic provisioning of Users in the network with high Security and Integrity of Data
 Consistent and Meaningful User Experience using of appropriate QoS
5. Access Technology Available for IoT
IoT Access Technology is spread across licensed and unlicensed spectrum and there are several number of Radio technologies
and some of these are listed in below table:
Table #2: Access Technology for IoT
At high these access can be classified in two categories:
 Non –Cellular Technologies
 Cellular Technologies
Each of the technologies available for IoT connectivity has its own advantages and disadvantages. However, the range of IoT
connectivity requirements – both technical and commercial – means cellular technologies can provide clear benefits across a wide
variety of applications.
Figure# 4: Cellular IoT Advantages
.
.
Access TechnologiesAvailable forIoT Page 6

Mohit Luthra, Rahul Atri, Mehdi Sadeghian,SukhvinderMalik, PreetRekhi October11, 2016
Evolutionin 3GPP to support IoT Page 7
In terms of global reach,cellular networks already cover 90 percent of the world’s population. WCDMA and LTE are catching
up, but GSM will offer superior coverage across the Globe. Cellular networks have been developed and deployed over three
decades,and they will be around for the foreseeable future. The cellular mobile industry represents a huge and mature ecosystem,
incorporating chipset, device and network equipment vendors, operators, application providers and others.
The global cellular ecosystem is governed by the 3GPP standardization forum, which guarantees broad industry support for future
development. When it comes to scalability, cellular networks are built to handle massive volumes of mobile broadband traffic;
the traffic from most IoT applications will be relatively small and easily absorbed. Operators are able to offer connectivity for IoT
applications from the start-up phase and grow this business with low TCO and only limited additional investment and effort.
Cellular connectivity offers the diversity to serve a wide range of applications with varying requirements within a network. QoS
mechanisms is essential for many IoT applications and cellular systems have mature QoS functionality, and this enables critical
IoT applications to be handled together with traffic from sensors, voice and mobile-broadband traffic on the same carrier.
Traditionally, the security mechanisms of cellular networks have been based on a physical SIM attached to the device, referred to
as a Universal Integrated Circuit Card (UICC). This has also enabled roaming between operators,which has been one of the main
factors behind the huge success of mobile networks. The SIM will also be essential in future IoT applications, with SIM
functionality embedded in the chipset (eUICC) or handled as a soft-SIM solution running in a trusted run-time environment of the
module. One network connecting the whole diversifying IoT market will guarantee the lowest possible TCO as well as fast time
to market.
6. Evolution in 3GPP Standard to Support IoT
To meet the new connectivity requirements of the emerging IoT segment, 3GPP has taken evolutionary steps on both the network
side and the device side. A single technology or solution cannot be ideal to all the different potential IoT applications, market
situations and spectrumavailability. As a result, the 3GPP standardizing severaltechnologies, including Extended Coverage GSM
(EC-GSM), LTE-M and NB-IoT.
LTE-M, NB-IoT and EC-GSM are all superior solutions to meet IoT requirements as a family of solutions, and can complement
eachother basedon technology availability, use case requirementsand deployment scenarios.The evolution for these technologies
is shown in figure #5. Technical studies and normative work for the support of Machine Type Communication (MTC) as part of
3GPP LTE specifications for RAN began in 3GPP Release 12 and are continuing with the goals of developing features optimized
for devices with MTC traffic.
Figure#5: Evolution of 3GPP Standards for IoT

Narrow Band LTE Technology Page 8
3GPP Rel.12 has specified low cost M2M devices (Cat-0). In Rel.13, standardization is continuing to further enhance coverage
and battery life and reduce complexity compared to existing LTE devices. 3GPP has the following objectives:
 Specify a new device category for M2M operation in all LTE duplex modes based on the Rel.12
 Low complexity device category supporting
- Reduced device bandwidth of 1.4MHz in downlink and uplink
- Reduced maximum transmit power of 20dBm.
 Provide an LTE coverage improvement of 15dB
 Enhance the DRX cycle in LTE to allow for longer inactivity periods to optimize battery life.
The narrow band NB-IoT proposal is set for approval in 3GPP Rel.13 with the following improvements over eMTC:
 Reduced device bandwidth of 180 KHz in downlink and uplink
 Reduced throughput based on single PRB operation
 Provide LTE coverage improvement corresponding to 20dB (5dB better than LTE-M).
 Powersaving mode and enhanced DRX to increase battery life and fulfill the “minimum 10 yearsbattery life” requirement
Similar to LTE Network evolution, we have seen LTE device evolution in two direction, one high and higher throughput based
on Carrier Aggregation and other lower throughput with low power consumption. The other direction is kicked off because of IoT
application and known as Machine Type Communication Devices. Cat. 1 UE can be considered as first and reference MTC Type
device which further can be optimize to Cat 0, Cat-M or Cat-NB devices. A Short comparison for the these devices in given in
Table # 3
Table# 3: UE Category for IoT Application
7. Narrow Band LTE Technology- Narrow Band IoT
NB-IoT or NB-LTE is a new 3GPP radio-access technology. It is not fully backward compatible with existing 3GPP devices
however it is designed to achieve excellent co-existence performance with legacy GSM, GPRS and LTE technologies. NB-LTE
requires 200 kHz minimum system bandwidth for both downlink and uplink, respectively. The choice of minimum system
bandwidth enables a number of deployment options like a GSM operator can replace one GSM carrier (200 kHz) with NB-IoT or
a LTE operator can deploy NB-LTE inside an LTE carrier by allocating one of the Physical Resource Blocks (PRB) of 180 kHz
to it. This minimum bandwidth 200 KHz requirement enables three possible modes of operation of NB-LTE which are mentioned
as below and illustrated in figure #6.
 In-band Operation using one PRB of a LTE carrier
 Guard band Operation by using used Resource Blocks within LTE carrier Guard Band
 Standalone Operation by using a GSM 200KHz carrier
In-Band NB-LTE NB-LTE in Guard Band NB-LTE as Standalone in GSM Carrier
Figure#6: NB-LTE Modes of Operations

NB-IoT reuses the conventional LTE design extensively, including the numerologies, downlink OFDMA, uplink SC-FDMA,
channel coding, rate matching, interleaving, etc. This significantly helps to reduce the time required to develop full design
specifications. Also, it is expectedthat the time required for developing NB-IoT products will be significantly reducedfor existing
LTE OEMs and ODMs.
NB-LTE also use the same Networks architecture as of conventional LTE Network with some optimization required to support
IoT Massive user requirements. The basic architecture for NB-LTE is shown in figure#7 and similar to LTE network consist of
two part namely Access Network and Evolved Packet System (EPS) Core Network. In access network architecture there is no
change, but at Core network the both user plane and control plane, some other optimizations are done to support IoT application.
A new node has been introduced as SCEF (Service Capability Exposure Function). The SCEF is designed especially for machine
type data.It is usedfor delivery of non-IP data overcontrol plane and provides an interface for the network services(authentication
and authorization, discovery and access network capabilities).
Figure#7: NB-LTE Network Architecture
A list of common optimization required for IoT support at EPS are listed below:
 On the Control Plane, UL data can transferred from the eNB to the MME. From there, it may either be transferred via the
Serving Gateway (SGW) to the Packet Data Network Gateway (PGW), or to the Service Capability Exposure Function
(SCEF) which however is only possible for non-IP data packets. From these nodes they are finally forwarded to the
application server or IoT Services. The same is depicted by Orange line. DL data is transmitted over the same paths in the
reverse direction. This approach does not requires radio bearers, data packets can be sent on the signaling radio bearer
instead. Consequently, this solution is most appropriate for the transmission of infrequent and small data packets.
 With the User Plane EPS optimization, data is transferred in the same way as the conventional data traffic, i.e. over radio
bearersvia the SGW and the PGWto the application server.Thus it createssome overhead on building up the radio bearer
connection, however it facilitates a sequence of data packets to be sent. This approach requires supports delivery of both,
IP and non-IP data packets with EPS.
 Another possible optimization can be done for reducing signaling by guiding IoT devices to perform periodic location
updates less frequently and by optimizing paging. Reducing signaling can help avoiding overload situations in massive
device network.
 Subscriber data storage handling in the HSS also need to be optimized to support a large number of IoT.
Narrow Band LTE Technology(Continue …) Page 9

8. Requirements, Challenges and Solutions for NB-LTE
In this paper we have listed the IoT requirements from NB-IoT many times and listing again here. In this section we will discuss
how NB-IoT as a technology can provide solution for the same.
Requirements:
 Cheap Device
 Long Battery Life
 Low Data Requirements
 Extended Coverage
 Massive no. of Device Support in a Cell
Solutions:
 Cheap Devices:The cost of devices is depends on its RF Hardware design and complexity of the software design. 3GPP
has come with following solution to achieve this.
- Reduced RF bandwidth
The many of the ODM experience that 40-50% of cost can be saved by reducing the bandwidth, so 3GPP has
reduced the bandwidth from 20 MHz to 200 KHz for NB-LTE.
- Reduced support of Transmission Mode
3GPP has recommended the NB-IoT Device may support only TM1 and TM2 which reduce the software
complexity of the system, this results in cost reduction for the device
- Reduced No. of Antenna
3GPP has recommended the NB-IoT device to have single antenna which reduce the size and addition RF path
in the device, hence cost is reduced by some amount.
- Reduction in uplink transmit power
Uplink transmit poweris controlled by the power amplifier stage in a device. If the device use less transmit power,
which can be achieved by a cheaper power amplifier. The Cat. M devices are expected to have 20 dBm uplink
power. The reduction in uplink power can have a reverse impact as it will impact the uplink budget of the system.
- Single RAT support
Device cost also depends on no. of RAT supported by it, because it required different RF hardware to support
multi RAT (2G, 3G and 4G) in different bands and different software to decode different RATs. 3GPP
recommended NB-IoT device shall support only one RAT i.e. LTE.
 Long Battery Life: IoT devices expected to have long battery life in order of 10 of years. 3GPP standard evolution has
proposed following solutions to lower the power consumption of the UE.
- Extended DRX Cycle in IDLE Mode
On increasing DRX cycle length in idle mode i.e. paging cycle length, UE can go to sleep for longer duration but
can remain attached. This extended DRX cycle length can impact SIB reading. Suppose extended DRX cycle
length is longer than the modification period, in such situation eNB would change SI and start broadcasting SIB’s
but UE may not listen. In conventional LTE BCCH modification period is a default DRX value resulting UE do
not miss modified SIBs. To avoid UE shall perform cell search and SI reading before the active time
Figure#8 SystemModification Broadcast
Requirements,ChallengesandSolutionsforNB-IoT Page 10

Mohit Luthra, Rahul Atri, Mehdi Sadeghian, SukhvinderMalik, PreetRekhi October 11, 2016
- Extended DRX Cycle in Connected Mode
Extended DRX is also refers to increasing the DRX cycle length in the connected mode, similar to IDLE mode.
When the extended DRX is 10.24sec and the normal DRX is 2.56sec, the power consumption for the extended
DRXshall be less by 4 times.
3GPP recommended to observe the gain of Extended DRX over conventional DRX,
extended DRX shall be longer than 6 SFN or more.
The Use of longer DRX may result in following:
 The device would be delay tolerant since extending DRX cycle length would mean delay in
Downlink data.
 If there is no Data in DL and UL due to extended DRX cycle, the RRC inactivity timer may
expire resulting in UE declared as Idle and RRC connection may be released. So it is
recommended that the UE inactivity Timer shall be chosen properly.
- Power Saving Mode
When UE goes into idle mode, it releases RRC connection. It then starts an active timer while performing all idle
mode functions i.e. PLMN selection, cell selection/reselection, paging. When active timer expires, UE enters into
PSM and starts a Periodic Update Timer, expiry of which will indicate the end of Power Saving Mode.
In this time, the UE stops reading paging or performing any AS or NAS functions. Also, network should not send
any data or paging to device as device cannot be reached as it does not listen to any paging message but it is still
registered with the network. The device remains in PSM mode until a mobile originating requires it to initiate any
procedure toward network for example Periodic Tracking Area update or uplink data from Device.
When UE wants to use PSM, it'll request an active timer in attach/TAU request. If eNB supports PSM it'll select
a timer value from the UE given value or MME given configuration. Afterwards,if UE wants to change its value
due to certain condition changes, it'll request the value in TAU procedure. This procedure is shown in figure #9.
The maximum duration of Power saving mode is about 12.1 days means Timer T3412 can be configured with
12.1 days.
Figure#9: Power Saver Mode Procedure
Requirements,ChallengesandSolutionsforNB-IoT (Continue …) Page 11

 LowData Rates Requirements: Data rates for a device depends on Bandwidth, MIMO support and Modulation coding
scheme (MCS). LTE-M devices are expected to provided ~ 1 Mbps DL/UL data rate whereas NB-LTE UE are expected
to support DL-200 Kbps/UL-144 Kbps. To meet these low data rate 3GPP has provided following recommendation.
- Reduce bandwidth
- Reduce support of MIMO
- Reduce the support of MCS to 16 QAM or QPSK
The bandwidth for IoT devices like LTE-M and NB-LTE devices is reduce to 1.4 MHz i.e. 6 RB and 200 KHz i.e. 1 RB.
Furthermore IoT devices are not designed to support MIMO, these devices are recommended have to be single antenna
and 64-QAM is not supported in LTE-M devices as well NB-LTE UEs. Maximum Transport block size is defined as 680
bits and minimum TBS is 16 bits.
- Data rate calculation for IoT Devices:
LTE-M has 6 RB, consider one sub frame time duration we canhave 6*168=1008 Resource Elements (REs).Considering
QPSK modulation each RE can carry 2 Bits information.
 No. of Bits per mili Second = 1008*2= 2016 bits/mSec.
 No. of Bits per Sec= 2016 bits/sec = 1.9 Mbps
Similarly, NB-IOT we have 1 RB and in one sub frame 168 REs. With Peak QPSK it can achieve 168*2=316 Bits/mSec.
 No. of Bits per Sec = 316000 Bits/Sec = 300 Kbps
 Extended Coverage: IoT devices are expected to be deployed in indoor environment or in some application basements
e.g.Automated Parking system having multiple level of basements.To provide the strong indoor coverage LTE-M should
provide 15 dB and NB-LTE should provide 20 dB additional link budget compare to conventional LTE system. This
additional link budget can be achieved using a set of techniques like
 Reducing the system Bandwidth
 Power boosting of reference and data REs,
 Adding more redundancy by repetitions/retransmissions,
 Keeping low performance requirement (error targets etc.)
3GPP recommended to use lower bandwidth like 1.4 MHz and 200 KHz for IoT application to get the extended coverage.
By reducing bandwidth to 1.4 MHz in case of LTE-M 11dB and reducing to 200 KHz in case of NB-LTE 20dB
improvement can be seen in the Maximum coupling loss (MCL) or Maximum Allowable Path loss (MAPL) while
comparing with the conventional 20 MHz LTE system. An evidence of this is provided by table#4.
Table# 4: Link budget Comparison for Conventional LTE, LTE-M and NB-LTE
Requirements,ChallengesandSolutionsforNB-IoT (Continue …) Page 12

 Massive no. of Device Support in a Cell
As per the IOT requirements, there will be huge number of connected devices supporting different applications. NB-LTE
need to support this massive IoT capacity by using only one PRB in both uplink and downlink. NB-LTE with one PRB
supports more than 52500 UEs per cell. This calculation is done based on following parameters in consideration.
Figure#10: Cell site Sector Area Definition
 Inter-site Distance (ISD) = 1732m
 Cell site sector radius, R = ISD/3 = 577.3m
 Area of cell site sector (assuming a regular hexagon) =3*sqrt(3/2)*R^2 = 0.866 Sq Km
Number of devices per cell site sector = Area of cell site sector*Household density per Sq km*number of devices per
household = 0.866*1517*40= 52549 user/cell site
Table#5 No. of User support by a Cell Site
9. NB-LTE Physical Layer
NB-LTE physical layer study can be divided in Downlink and uplink.
Downlink Transmission:
The downlink of NB-LTE is based on OFDMA with the same 15 kHz subcarrier spacing and slot, sub frame,and frame durations
are 0.5 ms, 1 ms, and 10 ms, respectively, identical to those in LTE. Furthermore, slot format in terms of cyclic prefix (CP)
duration and number of OFDM symbols per slot are also identical to those in LTE.
NB-LTE carrier uses one LTE PRB in the frequency domain, i.e. twelve 15 kHz subcarriers for a total of 180 KHz,10 KHz is can
be used as guard band on both side. Reusing the same OFDM numerology as LTE ensures the coexistence deployments inside a
LTE carrier.
NB-LTE DL physical channels are also designed based on legacy LTE to a large extent and listed below.
For Downlink NB-LTE has two physical signals
 NRS, Narrowband Reference Signal
 NPSS and NSSS, Primary and Secondary Synchronization Signals.
And three physical channels
 NPBCH, the narrowband physical broadcast channel
 NPDCCH, the narrowband physical downlink control channel
 NPDSCH, the narrowband physical downlink shared channel
NB-LTE Physical Layer Page 13

 4 bits indicating the most significant bits (MSBs) of the System Frame Number (SFN), the remaining least significant bits
(LSBs) are implicitly derived from the MIB-NB start
 2 bits indicating the two LSBs of the hyper frame number
 4 bits for the SIB1-NB scheduling and size
 5 bits indicating the system information value tag
 1 bit indicating whether access class barring is applied
 7 bits indicating the operation mode with the mode specific values (Inband-SamePCI, Inband-DifferentPCI, guard band
,standalone)
Figure#13: NBPBCH –MIB Resource Location
Narrowband Physical Downlink Control Channel:
NPDCCH carries scheduling information for both downlink and uplink data channels. It also carriers information about HARQ
for uplink and downlink channels, paging indication and RAR information. Different radio network temporary identifier (RNTI)
are assigned to each UE, one for random access (RA-RNTI), one for paging (P-RNTI), and a UE specific identifier (CRNTI)
provided in the random access procedure. These identifiers are implicitly indicated in the NPDCCH's CRC. So, the UE has to
look in its search space for that RNTI, and, if found, decodes the NPDCCH.
Three DCI formats are defined in NB-LTE,namely DCI format N0, N1 and N2
 N0: Its length is 23 bit and used for uplink grant
 N1: It is also 23 bits long and can be used for NPDSCH Scheduling/RACH Procedure Initiated by NPDCCH order
 N2: Its length is about 15 bit and used for Paging and NPDSCH
Figure#14: NPDCCH and NPDSCH transmission
The Transmission of NPDCCH can be seen in figure #14. When a UE receives a DCI,it can differentiate different formats in the
following way:
 DCI N2 is implicitly indicated in the way that the CRC is scrambled with the P-RNTI.
 If the CRC is scrambled with the C-RNTI,then the first bit in the message indicates whether DCI format N0 or N1 is
contained. For the case that the CRC is scrambled with the RA-RNTI,the content is a restricted DCI format N1
including only those fields required for the RACH response.
 Included in the DCI N0 and N1 is the scheduling delay, i.e. the time between the NPDCCH end and Start of NPDSCH t
or NPUSCH. This delay is at least 5 SFs for the NPDSCH and 8 for the NPUSCH. For DL transmission via DCI format
N2, the scheduling delay is fixed to 10 SFs.
Narrow Band LTE Physical Layer (Continue …) Page 14

Narrowband Physical Downlink Shared Channel:
An NPDSCH has the same structure as for NPDCCH shown in Figure #14. NPDSCH carries data from the higher layers as well
as Paging message, System information (SIB), and the RAR message. To reduce UE complexity, all the downlink channels use
the LTE tail-biting convolutional code (TBCC). A maximum transport block size (TBS) of 680 bit is supported by NB-LTE. The
mapping of this transport block spans NSF SFs.
The transport block is repeated providing NRep identical copies, using an SF interleaving for an optimized reception at the UE.
Both values, NSF and NRep are indicated in the DCI. The resulting SF sequence is mapped to NSF·NRep consecutive SFs defined
for NPDSCH. For the DL there is no automatic acknowledgement to a transmission, the eNB indicates this in the DCI. If this is
done, the UE transmits the acknowledgement using NPUSCH.
System Information Types #1:System information is transmitted over NPDSCH channel. NB-MIB contains all the
information required to acquire SIB1 (In legacy LTE, SIB1 decoding information is given by DCI 1A, not by MIB). NB-SIB1
contains all the information to acquire other SIBs (In legacy LTE, SIB1 carries only periodicity information of other SIBs, all
other information required to decode other SIBs are carried by DCI 1A, not by SIB1.
Like in convention LTE, NB-SIB1 also carries similar information as follows:
 Cell Access Related Information : PLMN Identity List, PLMN Identity, TA Code, Cell identity & Cell Status
 Cell Selection Information: Minimum Receiver Level ,Scheduling Information (Scheduling Information for other SIBs) -
SI message type & Periodicity, SIB mapping Info, SI Window length
 Transmitted at a fixed schedule with a periodicity of 2560 ms (256 Radio Frames) and in sub frame #4 of every other
frame in 16 continuous frames
 downlinkBitmap -This indicate which sub frame canbe usedfor downlink transmission. If this IE is missing, it is assumed
that any sub frame except NPSS/NSSS/NPBCH/SIB1-NB sub frame can be used for downlink transmission.
 eutraControlRegionSize : This applies only to in-band Operation mode. It indicates how many OFDM symbols are used
for control region i.e. NPDCCH, no PCFICH is required
 si-RadioFrameOffset : This indicates the Offset to calculate the start of the SI window in the unit of radio frames
 si-TB : This specifies the transport block size for all SI messages (SIB message other than SIB1) in the unit of bits
Uplink Transmission:
The uplink of NB-LTE supports both multi-tone and single tone transmissions. Multi-tone transmission is based on SCFDMA
with the same 15 kHz subcarrier spacing, 0.5 ms slot, and 1 ms sub frame as conventional LTE. Single-tone transmission supports
two numerologies, 15 kHz and 3.75 kHz. The 15 kHz numerology is identical to conventional LTE and thus achieves the best
coexistence performance in the uplink. Like the downlink, an uplink NB-LTE carrier also use a total system bandwidth of 180
kHz or one Resource Block.
For the uplink (UL),the two physical channels
 NPRACH,Narrowband physical random access channel
 NPUSCH, Narrowband physical uplink shared channel
And the
 DMRS, Demodulation Reference Signal
Narrowband Physical Random AccessChannel:
NPRACH is a newly designed channel in NB-LTE since the conventional LTE Physical Random Access Channel(PRACH) uses
a bandwidth of 1.08 MHz or 6 RBs which is more than NB-IoT uplink bandwidth. The preamble in NB-LTE is based on symbol
groups on a single subcarrier. Each symbol group has a cyclic prefix (CP) followed by 5 symbols and can be seen in Figure#15.
Figure#15: NPRACH Preamble Symbol Group

There are two preamble formats are defined namely format 0 and format 1 for NB-LTE.
 Preamble Format#0: TCP - 2048*Ts TSEQ- 5*8192*Ts Cell Radius – 10 Km
 Preamble Format#1: TCP - 8192*Ts TSEQ- 5*8192*Ts Cell Radius – 40 Km
Where Ts= 1/ (15000*2048),
Narrowband Physical Uplink Shared Channel:
NPUSCH channel used for uplink data and for sending HARQ Ack/Nack. NB-LTE does not have use PUCCH channel.
For NPUSCH also there are two format are defined by the standards.
 NPUSCH format#1 is used to carry uplink data with maximum Transport block size of 1000 bits. It uses the same slot
structure as conventional LTE PUSCH used with 7 OFDM symbols per slot and the middle symbol as the demodulation
reference symbol (DMRS).
Figure#16: NPUSCH Format#1
 NPUSCH format#2 is used for signaling HARQ acknowledgement for NPDSCH. This format use different slot structure
than LTE, has 7 OFDM symbols per slot, but uses the middle three symbols as demodulation reference symbol (DMRS).
Figure#17: NPUSCH Format#2
10. NB-LTE Call Setup and Higher Layer Procedure
When a UE accessesa cell, it follows the same principle as for LTE: It first searches a cell on an appropriate frequency. Decode
NPSS and NSSS for NCellID. After decoding NCellID, UE decode the NB-MIB Information transmitted over NPBCH,but there
it can get to know NB-LTE deployment mode i.e. In-band, Guard-band or Standalone, the schedulingInfoSIB1, SIB1-NB size
and number of repetitions, and its starting position. The message flow for complete call setup can be seen in Figure# 18
After getting information about NB-SIB1 UE get to know Cell Access Parameter – PLMN ID, TA Code, Cell identity & Cell
Status and cell selection information like minimum receiver level. SIB1 also provides Scheduling Information for other SIBs - SI
message type & Periodicity, SIB mapping Info, SI Window length. After successfuldecode of NB-SIB1,UE decodes further NB-
SIBs transmitted over NPDSCH. From SIB2 UEs get information about configuration of common logical channel, and Physical
Channel. Most information is NB-SIB2 is RACH configuration which is need for uplink synchronization.
After getting RACH configuration UE sends RACH Preamble, the UE first calculates its RA-RNTI from the transmission time.
It looks then in the NPDCCH for the DCI N1 scrambled with the RA-RNTI to get the Random Access Response. The UE expects
this message within the Response Window, which starts 3 SFs after the last preamble SF.
If Random Access Response message is not received, the UE transmits another Preamble. This is done up to a maximum number
of attempted depending on the CE level. If the total number of access attempts is reached,an associated failure is reported to the
RRC Layer. If RACH is successful, the UE gets in a temporary C-RNTI, timing advance command in RAR. Further, the RAR
provides the UL grant for msg3, containing all relevant data for msg3 transmission. The remaining procedure is done like in
conventional LTE, i.e. the UE sends an identification and upon reception of the Contention Resolution random access procedure
is completed.

Call Setupand Higher Layer Procedures(Continue …) Page 17
Figure#17: NB-LTE Attach Call Flow
UE sends RRCConnectionRequest indicating that it wants to connect to the network and stating establishment cause. In NB-LTE
it is restricted to mobile originated signaling, mobile originated data, mobile terminated access and exceptional reports. There is
no establishment cause fordelay tolerant traffic,because in NB-LTEall traffic is assumed to be delay tolerant. In response eNodeB
sends RRCConnectionSetup message providing configuration of the signaling radio bearer (SRB1), and the protocols.
If UE accept all the configuration provided by eNodeB, UE sends RRCConnectionSetupComplete message including selected
PLMN and MME, and can piggyback the NAS messages. After having set up the RRC connection, the next step is to establish
AS level security. eNodeB sends the SecurityModeCommand message, containing the ciphering algorithm to be applied on the
SRB1 and the DRB(s), and the integrity protection algorithm to protect the SRB1. All algorithms defined in LTE are also
supported by NB- LTE. With this message, the SRB1bis automatically changes to the SRB1, which is used for the next control
messages. After the security is activated, DRBs are set up using the RRC connection reconfiguration procedure.
In the reconfiguration message,the eNodeB sends the UE with the radio bearer,including the configuration of the RLC and the
logical channels, including a priority to balance the data transmission according to the actualrequirements. In MAC configuration
buffer status report (BSR), scheduling request (SR), time alignment and DRX are provided. Lastly, the physical channel
configuration provides the necessary parameters for mapping the data to the slots and frequencies.

Call Setupand Higher Layer Procedures(Continue …) Page 18
Cell Selection, Mobility and Paging Procedure
NB-LTE is designed for infrequent and few byte data transmission between the UE and the network. It is assumed that the UE
can exchange these information while being served from one cell, therefore, a handover procedure during RRC_CONNECTED
is not needed. If such scenario a cell change would be required, the UE has first go to the RRC_IDLE state and re-select another
cell therein.
For the RRC_IDLE state, cell re-selection is defined for both, intra frequency and inter frequency cells. Inter frequency refers
here to the 180 KHz carrier,which means that even if two carriers are used in the in-band operation embedded into the same LTE
carrier, this is still referred to as an inter-frequency re-selection.
In order to find a suitable cell, the UE first measures the received power and quality of the NRS. These values are then compared
to cell specific thresholds provided by the NB-SIB. The S-criteria states that if both values are above these thresholds, the UE
considers itself to be in coverage of that cell. If the UE is in coverage of one cell, it camps on it. Depending on the received NRS
power, the UE may have to start a cell re-selection. The UE compares this power to a re-selection threshold, which may be
different for the intra-frequency and the inter-frequency case. All required parameters are received from the actual serving cell,
there is no need to read NB-SIBs from neighbors’ cells. If multiple cell fulfill the S-criteria, the UE ranks the cells with respect to
the power excess over another threshold. A hysteresis is added in order to prevent too frequent cell reselection.
Unlike conventional LTE, there are no priorities for the different frequencies. The UE finally selects the highest ranked cell which
is suitable, i.e. from which it may receive normal service. When the UE leaves RRC_CONNECTED,it does not necessarily select
the same carrier to find a cell to camp on. The RRCConnectionRelease message may indicate the frequency on which the UE first
tries to find a suitable cell. Only if the UE does not find a suitable cell on this frequency, it may also try to find one on different
frequencies.
Paging is used to trigger an RRC connection and to indicate a change in system information for UE in RRC_IDLE mode.
It is sent over the NPDSCH and may contain a list of UEs to be paged and the information, whether paging is for connection setup
or whether system information has changed. Each UE who finds its ID in this list forwards to its upper layer that it is paged, and
may receive in turn the command to initialize an RRC connection.
If system information has changed, the UE starts to read NB-SIB1 and may obtain from there the information, which SIBs have
to be read again. The UE in the RRC_IDLE state only monitors some of the SFs with respect to paging, the paging occasions (PO)
within a subset of radio frames, the paging frames (PF).
If coverage enhancement repetitions are applied, the PO refers to the first transmission within the repetitions. The PFs and POs
are determined from the DRXcycle provided in NB-SIB2, and the IMSI. Due to the fact that paging is determine by the PFs and
POs values also depends on the IMSI, so different UEs have different paging occasions, which are uniformly distributed in time.
It is sufficient for the UE to monitor one paging occasion within a DRX cycle, if there are severalpaging occasions therein, the
paging is repeated in every one of them.

Comparisonof MBB-LTE and NB-LTE Page 19
Table#6 Comparison of MBB-LTE and NB-LTE

11. Summary and Conclusion:
The first release of LTE for cellular IoT has been provided in 3GPP Release 12,supporting long battery life and lower cost. 3GPP
Release 13 further reducesthe cost of devices and provides additional coverage by new cellular air interface which is fully adapted
to the requirements of typical machine type communications. The Release 13 specification provided a 180 KHz solution for
narrowband IoT deployment and a 1.08MHz solution for higher throughput IoT Application.
3GPP standardshas identified many optimization at air interface and PacketCore to support large number of devices and frequent
provisioning support for the IoT. Some of these are listed here and explained earlier in this paper
Layer 1 Optimization
 Highest modulation scheme QPSK
 Narrowband operation (200 kHz bandwidth)
 In-band (LTE), guard band (LTE) or standalone operation mode
 Half Duplex FDD operation mode
Higher Layer Optimization
 Maximum size of PDCP SDU and PDCP controlPDU is 1600 bytes
 In NB-IoT, data transfer is not only possible through DRB but also through NAS signaling.
 Also, AS optimization called RRC suspend/resume can be used to minimize the signaling needed to suspend/resume
user plane connection.
 Authentication between UE and core network and encryption and integrity protection of both AS and NAS signaling.
 Encryption of user plane data between the UE and radio network and key management mechanisms to effectively
support mobility and UE connectivity mode changes.
 New Features like eDRX and PSM has been recommended to make long UE battery life possible.
With 3GPP Release 14, the development of NB-IoT will continue. According to the current plans, NB-IoT will be extended to
include positioning methods, multicast services e.g. for software update or for messages concerning a whole group, mobility and
service continuity, as well as further technical details to enhance the field of applications for the NB-IoT technology.
12. References
While preparing this paper author have taken references form 3GPP resources and White papers available on Internet and which
are listed
 3GPP TR 45.820 Cellular system support for ultra-low complexity and low throughput Internet of Things (CIoT)
 3GPP TS 3GPP TS 36.321 V13 Medium Access Control (MAC) protocol specification
 3GPP TS 36.211 V13.2.0 (2016-06) E-UTRA Physical channels and modulation
 3GPP TS 36.331 V13.2.0 (2016-06) : E-UTRA RRC Protocol Specification
 TR 23.770 Study on system impacts of extended Discontinuous Reception (DRX) cycle for power consumption
optimization
 TR 37.888.Study on provision of low-cost Machine-Type Communications , User Equipment’s based on LTE
 TR36.824 Evolved Universal Terrestrial Radio Access (E-UTRA); LTE coverage enhancements
 RP-151621,RP-161919,RP-161042,RP-161067
 RAN approved REL-13 NB_IOT CRs (RAN#72)
 Machina Research, May 2015
 “Cellular networks for massive IoT,” Ericsson White Paper, Jan. 2016.
 www.sharetechnote.com
 www.slideshare.net/NehaKatyal3/iot-in-lte-63059787
 White Paper from 4G America, R&S and Samsung
Summary, Conclusionand References Page 20

Authors
Disclaimer
Authors state that this paperhas been compiled meticulously and to the best oftheir knowledge as of the date of publication. The in formation
contained herein the white paper is for information purposes only and is intended only to transfer knowledge about the re spective topic and
not to earn any kind of profit. Every effort has been made to ensure the information in this paper is accurate. Authors does not accept any
responsibility or liability whatsoever for any error of fact, omission,
Disclaimerand Authors Page 21

Cellular Narrow Band IoT- using LTE

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