1090  LoRaWAN Review: Architecture and Device Classes

This review covers the LoRaWAN network architecture and device classes. Here’s what you need to remember:

The Three Device Classes:

Class Downlink Capability Power Usage Best For
Class A Only after uplink (RX1/RX2 windows) Lowest Sensors, meters
Class B Scheduled ping slots (beacon sync) Medium Actuators, alarms
Class C Continuous listening Highest Smart plugs, HVAC

Quick Trade-off Summary:

Decision Trade-off
Higher Spreading Factor (SF) Longer range BUT slower data rate and more battery use
More Frequent Transmissions Fresher data BUT shorter battery life
Lower TX Power Longer battery BUT shorter range

1090.1 Learning Objectives

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

  • Understand LoRaWAN Architecture: Describe the star-of-stars network topology and component roles
  • Compare Device Classes: Select appropriate device class (A, B, C) based on latency and power requirements
  • Identify Protocol Parameters: Reference key LoRaWAN settings for spreading factors, security, and regional bands

1090.2 Prerequisites

Before using this review, ensure you have completed:

Required Chapters: - LoRaWAN Overview - Core concepts and architecture - LoRaWAN Architecture - Network components and topology

Recommended Background: - LPWAN Introduction - Context for low-power wide-area networks

1090.3 LoRaWAN Architecture Overview

Time: ~15 min | Level: Advanced | Unit: P09.C09.U01

This diagram provides a visual summary of the LoRaWAN network architecture and key components.

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graph TB
    subgraph Devices["End Devices"]
        ClassA[Class A Devices<br/>RX after TX<br/>Lowest Power]
        ClassB[Class B Devices<br/>Scheduled RX<br/>Beacon Sync]
        ClassC[Class C Devices<br/>Continuous RX<br/>Lowest Latency]
    end

    subgraph Physical["Physical Layer"]
        SF[Spreading Factors<br/>SF7-SF12<br/>Range vs Data Rate]
        BW[Bandwidth<br/>125/250/500 kHz]
        CR[Coding Rate<br/>4/5 to 4/8]
    end

    subgraph Network["LoRaWAN Network"]
        GW[Gateways<br/>Multi-SF Reception<br/>8+ Channels]
        NS[Network Server<br/>ADR, Deduplication<br/>Authentication]
        AS[Application Server<br/>Decryption<br/>Processing]
    end

    subgraph Security["Security Layer"]
        OTAA[OTAA<br/>Dynamic Keys<br/>Join Procedure]
        AES[AES-128<br/>Dual Layer<br/>Network + App]
    end

    ClassA & ClassB & ClassC -->|LoRa Modulation| GW
    SF & BW & CR -.->|Parameters| ClassA & ClassB & ClassC
    GW -->|IP Backhaul| NS
    NS -->|MQTT/HTTP| AS
    OTAA & AES -.->|Secure| NS

    style Devices fill:#2C3E50,color:#fff
    style Physical fill:#16A085,color:#fff
    style Network fill:#E67E22,color:#fff
    style Security fill:#7F8C8D,color:#fff

Figure 1090.1: LoRaWAN end-to-end architecture with device classes and security

{fig-alt=“LoRaWAN end-to-end architecture diagram with four colored layers. Navy blue End Devices layer contains three device classes: Class A with RX after TX and lowest power consumption, Class B with scheduled RX and beacon synchronization, Class C with continuous RX and lowest latency. Teal Physical Layer shows three parameter groups: spreading factors SF7 through SF12 trading range versus data rate, bandwidth options of 125, 250, and 500 kilohertz, and coding rates from 4/5 to 4/8. Orange LoRaWAN Network layer shows gateways with multi-SF reception and 8 plus channels connecting via IP backhaul to network server handling ADR, deduplication, and authentication, which connects to application server for decryption and processing. Gray Security layer shows OTAA with dynamic keys and join procedure, plus AES-128 providing dual-layer encryption for network and application data.”}

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flowchart TD
    START(["ADR Check"]) --> Q1{"Link margin<br/>> threshold?"}

    Q1 -->|Yes| INC["Increase Data Rate<br/>Lower SF"]
    Q1 -->|No| Q2{"Packet loss<br/>> acceptable?"}

    Q2 -->|Yes| DEC["Decrease Data Rate<br/>Higher SF"]
    Q2 -->|No| KEEP["Keep Current Settings"]

    INC --> APPLY["Apply ADR Request<br/>to Device"]
    DEC --> APPLY
    KEEP --> WAIT["Wait for<br/>next uplink"]

    style INC fill:#16A085,stroke:#2C3E50,color:#fff
    style DEC fill:#E67E22,stroke:#2C3E50,color:#fff
    style KEEP fill:#7F8C8D,stroke:#2C3E50,color:#fff

This flowchart shows how Adaptive Data Rate (ADR) dynamically optimizes spreading factor based on link quality, balancing range needs against airtime and battery consumption.

1090.4 Device Class Comparison

LoRaWAN defines three device classes (A, B, C) that trade power consumption for downlink latency.

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graph TB
    subgraph ClassA["Class A: Bi-directional (All Devices)"]
        A1[Uplink TX]
        A2[RX1 Window<br/>+1 sec]
        A3[RX2 Window<br/>+2 sec]
        A4[Deep Sleep<br/>0.5 µA]
        A5[Battery Life<br/>2-10 years]
        A1 --> A2 --> A3 --> A4
        A5 -.->|Lowest Power| A1
    end

    subgraph ClassB["Class B: Scheduled (Beacon Sync)"]
        B1[Beacon RX<br/>Every 128 sec]
        B2[Scheduled RX<br/>Ping Slots]
        B3[Uplink TX]
        B4[Deep Sleep<br/>Between Slots]
        B5[Battery Life<br/>6-18 months]
        B1 --> B2
        B3 --> B2
        B2 --> B4
        B5 -.->|Medium Power| B1
    end

    subgraph ClassC["Class C: Continuous (Mains Powered)"]
        C1[Continuous RX<br/>12-15 mA]
        C2[Uplink TX<br/>When Needed]
        C3[Immediate DL<br/><1 sec latency]
        C4[No Sleep<br/>Always On]
        C5[Battery Life<br/>Hours to Days]
        C1 --> C2 --> C3
        C4 -.->|Highest Power| C1
        C5 -.->|Mains Required| C4
    end

    subgraph Comparison["Use Case Selection"]
        UA[Sensors<br/>Meters<br/>Trackers]
        UB[Actuators<br/>Alarms<br/>Controls]
        UC[Smart Plugs<br/>HVAC<br/>Lighting]
    end

    ClassA -.->|Best For| UA
    ClassB -.->|Best For| UB
    ClassC -.->|Best For| UC

    style ClassA fill:#2C3E50,color:#fff
    style ClassB fill:#16A085,color:#fff
    style ClassC fill:#E67E22,color:#fff
    style Comparison fill:#7F8C8D,color:#fff

Figure 1090.2: LoRaWAN Class A, B, C comparison: power vs downlink latency

Key Insights:

Class Downlink Latency Power (mA) Sleep Mode Battery Life Use Cases
Class A Seconds to minutes 0.0005 (sleep) Yes 2-10 years Battery sensors, meters
Class B Sub-second (scheduled) 0.5 (sleep + beacon) Partial 6-18 months Smart alarms, actuators
Class C <1 second (instant) 12-15 (continuous) No Hours to days Mains-powered controls

Trade-off Analysis: - Class A uses 24,000x less power than Class C (0.5 uA vs 12 mA) - Class B adds 5% overhead for beacon synchronization vs Class A - Class C provides instant downlinks but requires mains power for practical operation

1090.5 LoRaWAN Quick Reference Table

NoteProtocol Parameters Summary
Component Key Characteristics Trade-offs
Device Classes
Class A RX after TX only, lowest power Downlink latency: seconds to minutes
Class B Scheduled RX slots, beacon sync Medium power, deterministic latency
Class C Continuous RX listening Lowest latency, highest power (mW range)
Spreading Factors
SF7 5.5 kbps, 2-5 km range, 41 ms ToA Best data rate, shortest range
SF9 1.8 kbps, 5-10 km range, 206 ms ToA Balanced performance
SF12 0.3 kbps, 10-20 km range, 991 ms ToA Maximum range, 24x power vs SF7
Network Topology
End Devices Sensors/actuators with LoRa radio Battery-powered, <50 mA TX
Gateways Multi-channel (8+), multi-SF receivers IP backhaul required, <10W power
Network Server ADR, deduplication, routing Manages 1000s-100,000s devices
Application Server Decryption, processing, APIs End-to-end payload access
Security
OTAA Dynamic session keys, scalable Requires join procedure
ABP Pre-configured keys, simple Manual key management, less secure
Encryption AES-128, dual-layer (network + app) End-to-end security
Regional Bands
EU868 863-870 MHz, 1% duty cycle 36 sec/hour TX limit per device
US915 902-928 MHz, no duty cycle FCC Part 15, 64 channels + 8 uplink
AS923 920-923 MHz, regional variants Country-specific regulations
Performance
Range (Urban) 2-10 km typical Depends on SF, obstacles, antenna
Range (Rural) 10-40 km typical Line-of-sight, SF12 optimal
Battery Life 2-10 years on coin cell Class A, infrequent TX, ADR enabled
Payload 51-222 bytes (depends on SF/DR) Smaller at higher SF
Latency 1-10 seconds typical (Class A) Class B/C for lower latency

Use This Table For: - Quick parameter lookup during network planning - Comparing device classes for your use case - Understanding SF selection impact on range/battery/throughput - Reference during troubleshooting and optimization

1090.7 Summary

This section covered the LoRaWAN architecture fundamentals:

  • Network Topology: Star-of-stars architecture with end devices, gateways, and servers
  • Device Classes: Class A (lowest power), Class B (scheduled), Class C (continuous RX)
  • Physical Layer: Spreading factors SF7-SF12 trading range for data rate
  • Security: OTAA/ABP activation with AES-128 encryption

1090.8 What’s Next

Continue to the next review section to learn about common configuration pitfalls: