1136  NB-IoT Technical Specifications

Bandwidth, Data Rates, and Deployment Modes

Prerequisites: NB-IoT Introduction | Cellular IoT Fundamentals

This enables: NB-IoT Architecture | NB-IoT Power Optimization

1136.1 Learning Objectives

By the end of this chapter, you will be able to:

  • Analyze technical specifications: Describe NB-IoT bandwidth, data rates, and latency characteristics
  • Compare deployment modes: Evaluate standalone, guard-band, and in-band deployment options
  • Understand coverage capabilities: Explain the 164 dB MCL and coverage enhancement mechanisms
  • Apply specifications to design: Select appropriate NB-IoT configurations for specific applications

1136.2 NB-IoT Overview

Narrowband IoT (NB-IoT) is a Low-Power Wide-Area Network (LPWAN) radio technology standardized by 3GPP (3rd Generation Partnership Project) specifically designed for IoT applications. Unlike LoRaWAN and Sigfox which use unlicensed spectrum, NB-IoT operates in licensed cellular spectrum, providing carrier-grade reliability and quality of service.

1136.2.1 Standardization and Evolution

NB-IoT was standardized by 3GPP in Release 13 (2016) to enable IoT connectivity over existing cellular infrastructure with focus on reliability, coverage, and long battery life.

Mermaid diagram

Mermaid diagram
Figure 1136.1
Architectural diagram depicting NB-IoT ecosystem: multiple IoT sensor devices (water meters, parking sensors, asset trackers) connect wirelessly to eNodeB cellular base stations, which route through Evolved Packet Core (EPC) network components including MME, S-GW, P-GW, and SCEF, ultimately connecting to cloud-based application servers and IoT platforms for data processing and visualization
Figure 1136.2: NB-IoT paradigm and architecture for cellular IoT

1136.3 Core Technical Specifications

1136.3.1 Key Parameters

Parameter Specification
Standard 3GPP Release 13+
Bandwidth 180 kHz (1 PRB)
Data Rate DL: 25 kbps (single-tone)
UL: 64 kbps (multi-tone)
Peak Rate ~250 kbps (multi-carrier)
Latency <10 seconds (normal)
<1 second (exception mode)
Duplex Half-duplex FDD
Max Coupling Loss 164 dB (MCL)
Power Class 23 dBm (200 mW)
Modulation QPSK (uplink), QPSK (downlink)

Graph diagram

Graph diagram
Figure 1136.3

1136.3.2 Data Rates and Capacity

NB-IoT supports different data rates depending on the configuration:

Downlink (Network to Device):

  • Single-tone: 25 kbps
  • Multi-tone: up to 200+ kbps

Uplink (Device to Network):

  • Single-tone (3.75 kHz): 16 kbps
  • Single-tone (15 kHz): 64 kbps
  • Multi-tone (15 kHz x 3): up to 160 kbps

Graph diagram

Graph diagram
Figure 1136.4

1136.4 Deployment Modes

NB-IoT can be deployed in three different modes, allowing operators to introduce IoT services without requiring entirely new spectrum.

The NPTEL IoT course from IIT Kharagpur describes a three-tier fog computing architecture that illustrates how NB-IoT devices integrate with edge and cloud infrastructure:

  • IoT Devices Tier (Bottom): Sensors, smart homes, vehicles, and wearables generate data
  • Fog Layer (Middle): Fog nodes (switches, routers, gateways) provide local processing for high-sensitivity data, with private server/cloud options for confidential information
  • Cloud Tier (Top): Processes less sensitive data and provides global analytics

This architecture demonstrates how NB-IoT sensors can leverage fog computing for local processing before sending aggregated data to the cloud, reducing latency and bandwidth requirements while maintaining data privacy.

Source: NPTEL Internet of Things Course, IIT Kharagpur

1136.4.1 Standalone Mode

Operates in dedicated spectrum (e.g., refarmed GSM spectrum):

Graph diagram

Graph diagram
Figure 1136.5

Typical bands:

  • 900 MHz (former GSM)
  • 800 MHz
  • 700 MHz

Advantages:

  • No impact on existing LTE services
  • Full bandwidth available
  • Easier network planning

1136.4.2 Guard-Band Mode

Operates in the guard band between LTE carriers:

Graph diagram

Graph diagram
Figure 1136.6

Use case:

  • Maximize spectrum efficiency
  • Rapid NB-IoT introduction
  • No need for new spectrum

1136.4.3 In-Band Mode

Operates within an LTE carrier using one or more Physical Resource Blocks (PRBs):

Graph diagram

Graph diagram
Figure 1136.7

Trade-off:

  • Easy deployment (software upgrade)
  • Slightly reduces LTE capacity
  • Most common initial deployment mode

1136.4.4 Deployment Mode Comparison

Mode Spectrum LTE Impact Complexity Coverage
Standalone Dedicated (GSM) None Low Excellent
Guard-Band Between LTE Minimal Medium Very good
In-Band Within LTE PRB Some reduction Higher Very good

Artistic visualization of the three NB-IoT deployment modes - standalone, guard-band, and in-band - showing spectrum allocation strategies with color-coded frequency blocks, demonstrating how NB-IoT fits into different parts of the cellular spectrum landscape including refarmed GSM, LTE guard bands, and within LTE carriers.

NB-IoT Deployment Modes

Detailed NB-IoT deployment architecture showing the network topology from IoT devices through eNodeB base stations to the evolved packet core, illustrating how NB-IoT traffic is handled within the cellular infrastructure and integrated with existing LTE networks.

NB-IoT Deployment Architecture
Figure 1136.8: NB-IoT deployment modes enable flexible integration with existing cellular infrastructure
WarningCommon Misconception: “In-Band Mode Barely Impacts LTE Performance”

The Misconception: Many engineers assume that because NB-IoT uses only 180 kHz (1 PRB) of a 10-20 MHz LTE carrier, the performance impact is negligible (< 1%).

The Reality: In dense urban deployments, the actual capacity reduction can be 3-7% during peak hours, significantly higher than the theoretical 1-2% PRB allocation suggests.

Real-World Example: Major European Carrier (2019-2021)

A tier-1 European mobile operator deployed NB-IoT in in-band mode across 250 urban cell sites to support 500,000 smart meters:

Initial Assumptions (2019):

LTE carrier: 20 MHz (100 PRBs)
NB-IoT allocation: 1 PRB (180 kHz)
Expected LTE capacity loss: 1%
Expected customer impact: Negligible

Actual Results After 18 Months (2021):

Peak hour LTE throughput reduction: 5-7%
Off-peak reduction: 1-2%
Customer complaints: +12% (congestion)
Root cause: Scheduler overhead + guard tones

Why the Discrepancy?

  1. Scheduler Complexity (+2-3% overhead):
    • LTE scheduler must coordinate both LTE and NB-IoT transmissions
    • NB-IoT uses different timing (15 kHz subcarrier vs 15 kHz LTE)
    • Processing overhead: ~50 ms additional latency per frame
  2. Guard Tone Overhead (+1-2%):
    • NB-IoT requires 10-15 kHz guard tones on each side
    • Actual spectrum usage: 200-210 kHz (not 180 kHz)
    • Adjacent PRBs experience 5-10% throughput degradation
  3. Uplink Interference (+0.5-1%):
    • NB-IoT devices transmit at +23 dBm (200 mW max)
    • Some devices have poor RF filtering
    • Cross-interference into adjacent LTE PRBs
  4. Peak Hour Congestion Amplification (+1-2%):
    • NB-IoT messages during peak hours (6-9 PM)
    • Smart meters often report at fixed times
    • Coincides with residential LTE peak usage

Best Practice Recommendation:

For large-scale urban NB-IoT deployments (>100,000 devices per cell site):

  • Preferred: Standalone mode (refarmed GSM 900 MHz) - 0% LTE impact
  • Acceptable: Guard-band mode - 2-3% LTE impact
  • Avoid: In-band mode for > 50,000 devices/site - 5-7% peak hour impact

Takeaway: Always measure real-world performance under peak load, not just theoretical PRB allocation.

1136.4.5 NB-IoT Deployment Mode Selection (Decision Flowchart)

This decision flowchart provides an approach to selecting the optimal NB-IoT deployment mode based on operator constraints and spectrum availability:

Flowchart diagram

Flowchart diagram
Figure 1136.9: NB-IoT deployment mode selection flowchart guiding operators through spectrum availability assessment. Standalone (green) is optimal when GSM spectrum can be refarmed. Guard-band (orange) utilizes unused LTE guard bands. In-band (blue) sacrifices 1 PRB from LTE carrier for maximum flexibility. Hybrid deployment uses multiple modes across coverage areas.

1136.5 NB-IoT vs Other LPWAN Technologies

1136.5.1 Technology Comparison

Graph diagram

Graph diagram
Figure 1136.10

1136.5.2 Detailed Comparison

Feature NB-IoT LoRaWAN Sigfox
Spectrum Licensed cellular Unlicensed ISM Unlicensed ISM
Standard 3GPP Release 13+ LoRa Alliance Proprietary
Data Rate 25-250 kbps 0.3-50 kbps 0.1 kbps
Latency <10s (normal) 1-5s seconds-minutes
Range 10-15 km (urban) 2-5 km (urban) 3-10 km (urban)
Battery Life 10+ years 5-10 years 10-20 years
QoS Guaranteed (SLA) Best effort Best effort
Infrastructure Existing cellular Deploy gateways Operator network only
Cost (device) $5-15 $5-15 $5-10
Cost (service) $1-5/month $0 (private) or $1-3/month (public) $1-10/year
Mobility Full support Limited Limited
Security 3GPP security (256-bit) AES-128 Proprietary

1136.5.3 When to Choose NB-IoT

Choose NB-IoT when you need:

  • Guaranteed quality of service (SLA from mobile operator)
  • Existing cellular coverage (no gateway deployment)
  • Regulatory compliance (licensed spectrum)
  • Full mobility support (handoff between cells)
  • Higher data rates occasionally (firmware updates)
  • Carrier-grade security and authentication
  • No technical team to manage infrastructure

Consider alternatives when:

  • Deploying < 100 devices (LPWAN private network more economical)
  • Need very low cost per device long-term (Sigfox cheaper for simple apps)
  • Require complete data privacy (private LoRaWAN)
  • Want zero recurring costs (private LoRaWAN)

1136.6 Knowledge Check

Test your understanding of NB-IoT technical specifications.

Question 1: A cellular operator is deploying NB-IoT to support IoT devices. They have existing LTE infrastructure with 10 MHz carriers. Which deployment mode would allow the FASTEST time-to-market with minimal impact on existing LTE subscribers?

Explanation: In-Band mode enables fastest deployment with software-only changes:

In-Band Deployment Process:

  • No new spectrum - use existing LTE license
  • No new hardware - software upgrade only
  • Minimal planning - same tower locations
  • Quick testing - easy rollback if issues
  • Gradual rollout - enable per-cell as needed

Why other options are slower:

  • Standalone (GSM refarm): Requires migrating GSM users, regulatory approval (6-12 months)
  • Guard-Band: May need hardware filters, interference analysis (3-6 months)
  • New 700 MHz spectrum: Spectrum auction, new equipment (12-24 months)

Real-world example: Deutsche Telekom launched NB-IoT in Germany using In-Band mode - announcement to commercial service in ~6 months.

Question 2: NB-IoT can be deployed inside an LTE carrier using a single LTE Physical Resource Block (PRB). What is the bandwidth of one PRB?

Explanation: In LTE, one PRB occupies 180 kHz (12 subcarriers x 15 kHz each). NB-IoT can be placed in-band by allocating 1 PRB within an existing LTE carrier (software-configured on the eNodeB).

This narrow bandwidth is why it’s called “Narrowband” IoT - it uses a tiny fraction of the spectrum compared to regular LTE.

1136.7 Summary

  • NB-IoT is a 3GPP-standardized LPWAN operating in licensed cellular spectrum with 180 kHz bandwidth
  • Three deployment modes enable flexible spectrum utilization: standalone (dedicated spectrum), guard-band (between LTE carriers), and in-band (within LTE carrier using 1 PRB)
  • Data rates range from 25 kbps to 250 kbps depending on configuration, suitable for small IoT payloads
  • 164 dB Maximum Coupling Loss provides +20 dB better coverage than GPRS, enabling deep indoor penetration
  • Licensed spectrum operation provides interference protection, guaranteed QoS, and carrier SLA

1136.8 What’s Next

Continue your NB-IoT learning journey with these related topics: