9 IoT Frequency Bands and Licensing

In 60 Seconds

IoT devices primarily use three frequency bands: 2.4 GHz (globally available but congested), 5 GHz (more bandwidth, shorter range), and sub-GHz (868/915 MHz for long-range, low-power). Spectrum is either licensed (cellular, guaranteed QoS, carrier fees) or unlicensed (ISM bands, free but shared), with regional regulations governing power limits, duty cycles, and channel access.

Key Concepts

ISM Bands: Industrial, Scientific, and Medical unlicensed frequency bands (2.4 GHz, 915 MHz, 868 MHz) available globally without licensing
Sub-GHz Bands: Frequencies below 1 GHz (433 MHz, 868 MHz, 915 MHz); provide better wall penetration and longer range than 2.4 GHz
Duty Cycle Restriction: Regulatory limit on transmission time in unlicensed bands; e.g., Europe limits to 1% duty cycle in 868 MHz band
EIRP (Effective Isotropic Radiated Power): Maximum allowed transmit power including antenna gain; e.g., +20 dBm EIRP in many unlicensed bands
Channel Plan: Allocation of specific frequencies within a band for different applications; prevents inter-system interference
Licensed Spectrum vs Unlicensed: Licensed bands provide interference protection at cost of regulatory fees; unlicensed bands are free but shared
IoT Band Selection Criteria: Coverage range, penetration, regulatory compliance, device cost, power consumption, and data rate requirements
5G NR for IoT: Standalone 5G NR IoT bands; includes Redcap (Reduced Capability) for simplified IoT devices

9.1 Introduction

⏱️ ~8 min | ⭐⭐ Intermediate | 📋 P08.C16B.U01

Building on the electromagnetic fundamentals from the previous chapter, this chapter explores the specific frequency bands used for IoT communication and the regulatory frameworks that govern their use. Understanding these bands and their trade-offs is essential for selecting the right wireless technology for your application.

Learning Objectives

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

Evaluate the trade-offs among 2.4 GHz, 5 GHz, and sub-GHz bands in terms of range, penetration, interference, and data rate for a given IoT deployment
Analyse channel allocation conflicts and coexistence strategies in the 2.4 GHz ISM band (Wi-Fi vs Zigbee vs BLE)
Differentiate licensed and unlicensed spectrum models, justifying when each is appropriate for an IoT use case
Map regional spectrum regulations (FCC Part 15, ETSI EN 300 220) to specific compliance requirements for multi-region product design
Calculate free-space path loss and apply ISM band constraints (EIRP limits, duty cycle) to validate a wireless link budget

For Beginners: IoT Frequency Bands

Different IoT technologies use different radio frequencies, just like different radio stations use different FM channels. Some frequencies travel far but carry little data (like AM radio), while others carry lots of data but only over short distances (like Bluetooth). Understanding frequency bands helps you choose the right wireless technology for your project.

Sensor Squad: The Radio Frequency Neighborhood

“Imagine all radio signals live in a big neighborhood,” said Max the Microcontroller, pointing to a colorful map. “Each technology gets its own block. Wi-Fi lives on the 2.4 GHz and 5 GHz blocks. Bluetooth lives next door to Wi-Fi on 2.4 GHz. And our long-range IoT friends like LoRa live way down on the sub-GHz blocks at 868 or 915 MHz.”

Sammy the Sensor looked at the map curiously. “Why does it matter which block you live on?” Lila the LED jumped in. “Higher frequencies are like narrow, fast streets – lots of data flows through but only for a short distance. Lower frequencies are like wide country roads – data moves slower but travels much farther and even passes through walls!”

“And there are rules!” added Bella the Battery. “Some blocks are licensed – you have to pay a phone company to use them, but you get guaranteed service with no noisy neighbors. Other blocks are unlicensed ISM bands – free for everyone, but you have to share. That is why your Wi-Fi sometimes gets slow when all the neighbors are streaming movies.”

“Different countries have different rules too,” Max noted. “In Europe, the sub-GHz ISM band is at 868 MHz with strict duty cycle limits. In America, it is 915 MHz with higher power allowed. So when designing an IoT product for the global market, you need to check the local regulations!”

9.2 Prerequisites

Before diving into this chapter, you should be familiar with:

Electromagnetic Waves and Spectrum Basics: Understanding of EM wave properties
Mobile Wireless Technologies Basics: Where common IoT technologies operate

Related Chapters

Series Navigation:

Previous: Electromagnetic Waves and Spectrum Basics
Next: Cellular Spectrum for IoT
Next: Propagation and Design

Specific Technologies:

Wi-Fi Fundamentals - 2.4 GHz and 5 GHz details
Bluetooth Overview - 2.4 GHz frequency hopping
LoRaWAN Overview - Sub-GHz LPWAN
LPWAN Fundamentals - Sub-GHz technology comparison

9.3 IoT Wireless Frequency Bands

⏱️ ~20 min | ⭐⭐ Intermediate | 📋 P08.C16B.U02

9.3.1 The 2.4 GHz ISM Band

The 2.4 GHz band (2.400 - 2.4835 GHz) is the most commonly used frequency range for local and personal area IoT networks. It’s part of the Industrial, Scientific, and Medical (ISM) radio bands, which are unlicensed and available worldwide.

Advantages:

Globally unlicensed (no licensing fees)
Widespread device support
Mature technology ecosystem
Good balance of range and bandwidth

Challenges:

Heavy congestion (Wi-Fi, Bluetooth, Zigbee, microwave ovens)
Interference from multiple sources
Limited number of non-overlapping channels

Putting Numbers to It

Calculate the wavelength at 2.4 GHz and its impact on antenna design:

\[\lambda = \frac{c}{f} = \frac{3 \times 10^8}{2.4 \times 10^9} = 0.125 \text{ m} = 12.5 \text{ cm}\]

A quarter-wave antenna is $\lambda/4 = 3.1$ cm, fitting easily inside any device. For 868 MHz: $\lambda = 34.5$ cm, requiring $\lambda/4 = 8.6$ cm antenna—still compact but $2.8\times$ larger than 2.4 GHz, explaining why 2.4 GHz dominates consumer IoT despite worse propagation.

Chart showing 2.4 GHz ISM band channel allocations with Wi-Fi channels 1, 6, and 11 overlapping multiple 2 MHz Zigbee channels, highlighting safer Zigbee channels 15, 20, 25, and 26 — Figure 9.1: How wide Wi-Fi channels can overlap multiple Zigbee channels in the 2.4 GHz ISM band (and which Zigbee channels tend to be safer).

Common IoT protocols using 2.4 GHz:

Wi-Fi (IEEE 802.11 b/g/n)
Bluetooth and Bluetooth Low Energy (BLE)
Zigbee (IEEE 802.15.4)
Thread (IPv6-based mesh)

9.3.2 Why 2.4 GHz Became the Default IoT Band (Despite Being the Most Congested)

The 2.4 GHz ISM band is simultaneously the worst radio environment (microwave ovens, Wi-Fi, Bluetooth, Zigbee, cordless phones, baby monitors all share it) and the most popular choice for IoT. This seeming contradiction has a clear explanation rooted in physics, economics, and history.

Physics made it the sweet spot. At 2.4 GHz, the wavelength is 12.5 cm – small enough for compact antennas (a quarter-wave antenna is just 3.1 cm, fitting inside any device) yet long enough for reasonable indoor penetration (6-10 dB per concrete wall versus 15-20 dB at 5 GHz). Sub-GHz frequencies (868/915 MHz) penetrate better and travel farther, but their 8.6 cm quarter-wave antennas are larger, and critically, the bands are regionally fragmented (EU868, US915, AS923), requiring different hardware SKUs per market.

Economics locked it in. The 2.4 GHz band is unlicensed and harmonized worldwide – a device designed in Shenzhen works in Stockholm, Sao Paulo, and San Francisco without hardware changes. This created a massive manufacturing ecosystem. By 2020, 2.4 GHz radio chips cost $0.30-0.50 in volume, while sub-GHz chips (which need regional variants) cost $0.80-1.50. For a $15 smart plug, that $0.50 savings per unit is decisive at scale.

History cemented it. When the IEEE 802.15.4 committee chose 2.4 GHz for Zigbee in 2003, Wi-Fi (802.11b, 1999) had already claimed the band but device density was low. Bluetooth (1998) was there too. By the time congestion became severe (2015+), billions of Zigbee, BLE, and Thread devices were deployed, and the protocol ecosystem was too mature to migrate.

The congestion tax is real but manageable. In a typical apartment with 2 Wi-Fi access points, 3 Bluetooth devices, and a microwave oven, a Zigbee sensor experiences 5-15% packet error rate on a fixed channel. Adaptive techniques (BLE’s 1,600 hops/sec, Zigbee’s channel 25/26 above Wi-Fi, Thread’s channel scanning) reduce effective error rates to 0.1-1%. The engineering effort goes into coexistence, not band migration.

9.3.3 The 5 GHz Band

The 5 GHz band (primarily 5.150 - 5.875 GHz) offers higher bandwidth and less congestion than 2.4 GHz. It’s used mainly for Wi-Fi (IEEE 802.11a/n/ac/ax) and provides:

Advantages:

Higher data rates (more bandwidth available)
Less interference from non-Wi-Fi devices
More non-overlapping channels (23+ in most regions)

Limitations:

Shorter range than 2.4 GHz
Reduced penetration through walls and obstacles
Higher power consumption
Not supported by all IoT devices

Diagram of 5 GHz Wi-Fi channel groups UNII-1, UNII-2, UNII-2 Extended, and UNII-3 showing frequency ranges, channel numbers, and DFS requirements by region — Figure 9.2: 5 GHz Wi-Fi channel groups (UNII-1/2/2e/3) and typical DFS considerations (region-dependent).

9.3.4 Sub-GHz Bands

Sub-GHz frequencies (below 1 GHz) are increasingly popular for IoT applications requiring long range and low power consumption. Common bands include:

868 MHz (Europe): LoRa, Sigfox, Z-Wave
915 MHz (North America): LoRa, Sigfox, Z-Wave
433 MHz (Worldwide): Simple remote controls, sensors

Characteristics:

Excellent range (kilometers in open areas)
Superior building penetration
Lower power consumption
Lower data rates
Regional frequency variations (licensing requirements vary)

Map of sub-GHz ISM band allocations by region showing EU868 in Europe, US915 in North America, AS923 in Asia-Pacific, and 433 MHz worldwide with power and duty cycle limits — Figure 9.3: Common sub‑GHz ISM allocations by region (e.g., EU868, US915, AS923) and why multi-region devices need configurable bands.

Quick Check: Frequency Band Selection

9.4 Spectrum Licensing

⏱️ ~12 min | ⭐⭐ Intermediate | 📋 P08.C16B.U03

Minimum Viable Understanding: ISM Band Regulations

Core Concept: ISM (Industrial, Scientific, Medical) bands are unlicensed frequency allocations where anyone can transmit without a license, but must follow strict rules on transmit power (EIRP), duty cycle, and channel access methods set by regional regulators (FCC in US, ETSI in Europe, etc.).

Why It Matters: Violating ISM regulations can result in product recalls, fines, and legal liability. The rules differ significantly by region: EU868 limits devices to 14 dBm EIRP with 1% duty cycle (36 seconds per hour), while US915 allows 30 dBm with no duty cycle limit but requires frequency hopping. A device certified for US deployment will be illegal in Europe, and vice versa.

Key Takeaway: Before any IoT product deployment, identify your target regions and verify compliance with local regulations. For global products, design firmware that supports region-specific configurations (frequency, power, duty cycle). Use pre-certified radio modules (FCC/CE/IC marked) to simplify compliance testing, but remember that the final product still requires certification in most jurisdictions.

9.4.1 Licensed vs Unlicensed Spectrum

Radio frequency spectrum is a finite resource regulated by governmental bodies. Understanding the distinction between licensed and unlicensed spectrum is crucial for IoT deployment.

Licensed Spectrum:

Requires regulatory approval and fees
Exclusive use rights (cellular operators)
Protected from interference
Examples: 4G LTE (700-2600 MHz), 5G (3.5 GHz, mmWave)

Unlicensed Spectrum (ISM Bands):

Free to use (within regulatory limits)
Shared among many users and devices
Subject to power and duty cycle restrictions
Examples: 2.4 GHz, 5 GHz, 868/915 MHz

9.4.2 Regional Variations

Different countries allocate spectrum differently. IoT devices must comply with regional regulations:

Region	Sub‑GHz (common ISM)	2.4 GHz ISM	5 GHz Wi‑Fi	Notes
Europe	EU868 (863–870 MHz)	2.400–2.4835 GHz	Region-specific (5 GHz sub‑bands; DFS/power vary)	ETSI regulations
North America	US915 (902–928 MHz)	2.400–2.4835 GHz	Region-specific (5 GHz sub‑bands; DFS/power vary)	FCC Part 15
Asia-Pacific	Varies (e.g., AS923 / 920–928 MHz)	2.400–2.4835 GHz	Varies by country	Always check local rules
Global (short range)	315/433 MHz (region-dependent)	Universal	Varies by country	Common for simple remotes; verify allocations

Tradeoff: Sub-GHz (868/915 MHz) vs 2.4 GHz Band

Option A (Sub-GHz): Range 2-15 km outdoor, +157 dB link budget (LoRa SF12), excellent wall penetration (-3 dB per concrete wall), bandwidth 0.3-50 kbps, 10+ year battery life on 2xAA cells. Path loss at 1 km: ~92 dB.

Option B (2.4 GHz): Range 50-300m indoor/outdoor, +100 dB link budget (BLE), moderate penetration (-6 dB per concrete wall), bandwidth 250 kbps-2 Mbps, 1-5 year battery life. Path loss at 100m: ~80 dB.

Decision Factors: Choose Sub-GHz for rural deployments, outdoor sensors, smart agriculture, or utility metering where range exceeds 500m. Choose 2.4 GHz for smart home, building automation, wearables, or any application requiring >100 kbps throughput or existing Wi-Fi/BLE ecosystem integration.

9.5 Worked Example: Smart Building Frequency Plan — 800-Device Coexistence

Scenario: GreenTech Properties retrofits a 12-storey commercial office building in Amsterdam with 800 IoT devices across 4 systems. The RF environment includes 45 existing Wi-Fi 6 access points on channels 1, 6, and 11 (2.4 GHz) and channels 36, 52, 100, 149 (5 GHz).

System	Devices	Protocol	Data Pattern
HVAC monitoring	300 temp/humidity sensors	Zigbee	20-byte reading every 5 min
Lighting control	250 smart switches	Thread (over 802.15.4)	On/off commands, ~100 ms latency
Energy metering	200 sub-meters	LoRaWAN (EU868)	50-byte reading every 15 min
Occupancy detection	50 PIR + CO₂ sensors	BLE (beacons)	Advertising every 2 sec

9.5.1 Step 1: Identify Interference Zones

The 45 Wi-Fi APs on channels 1, 6, 11 occupy:

Ch 1: 2,401–2,423 MHz (overlaps Zigbee ch 11–14)
Ch 6: 2,426–2,448 MHz (overlaps Zigbee ch 15–19)
Ch 11: 2,451–2,473 MHz (overlaps Zigbee ch 20–24)

With Wi-Fi at +20 dBm and Zigbee at 0 dBm, the 20 dB power difference means Wi-Fi signals overwhelm Zigbee within 10 m of any AP — a zone covering approximately 60% of each floor.

9.5.2 Step 2: Assign Channels

System	Band	Channel Assignment	Rationale
Zigbee (HVAC)	2.4 GHz	Channel 25 (2,475 MHz)	Above Wi-Fi ch 11 (ends at 2,473 MHz). Only 2 MHz gap, but Zigbee’s 2 MHz bandwidth fits. Measured interference: <1% PER
Thread (lighting)	2.4 GHz	Channel 26 (2,480 MHz)	Highest channel, completely clear of all Wi-Fi. Critical for lighting commands needing <100 ms response
LoRaWAN (energy)	868 MHz	EU868 default (868.1, 868.3, 868.5 MHz)	No interference with 2.4 GHz systems. 1% duty cycle allows 300 bytes/hour per device — sufficient for 4x 50-byte readings/hour
BLE (occupancy)	2.4 GHz	Adaptive hopping (37, 38, 39 advertising)	BLE advertising uses 3 fixed channels (2,402/2,426/2,480 MHz). Ch 37 overlaps Wi-Fi ch 1, ch 38 overlaps ch 6. Measured: 8% advertising packet loss — acceptable for 2-sec interval beacons (effective 2.16-sec average)

9.5.3 Step 3: Validate with Measurements

After deployment, a 24-hour spectrum sweep on Floor 7 (highest Wi-Fi density) confirmed:

Metric	Zigbee Ch 25	Thread Ch 26	LoRaWAN 868	BLE Adv
Packet Error Rate	0.8%	0.2%	0.01%	7.6%
Avg latency (one-hop)	12 ms	8 ms	N/A (async)	N/A (beacon)
Retransmission rate	1.2%	0.4%	0.1%	N/A
Verdict	Pass	Pass	Pass	Pass

Why Channel Planning Saved This Project

GreenTech’s initial deployment used Zigbee channel 15 (the commonly recommended “safe” channel). Packet error rates hit 23% during business hours because Wi-Fi channel 6 spectral leakage extended to 2,425 MHz in a dense 45-AP environment. Moving to channel 25 reduced PER from 23% to 0.8% — a configuration change requiring zero hardware replacement.

Lesson: The “safe” channels (15, 20, 25, 26) assume standard 3-channel Wi-Fi deployments. In high-density Wi-Fi environments, only channels 25 and 26 provide reliable separation. Always validate with a spectrum analyzer before finalizing channel assignments.

9.6 Interactive: Frequency Band Comparison Calculator

Show code

viewof freqBandSelect = Inputs.select(
  ["433 MHz (ISM)", "868 MHz (EU)", "915 MHz (US)", "2400 MHz (ISM)", "5000 MHz (Wi-Fi 5)", "5800 MHz (Wi-Fi 6E)"],
  {label: "Frequency Band", value: "868 MHz (EU)"}
)

viewof distanceKm = Inputs.range([0.01, 20], {label: "Distance (km)", step: 0.01, value: 1.0})

freqMap = ({
  "433 MHz (ISM)": 433,
  "868 MHz (EU)": 868,
  "915 MHz (US)": 915,
  "2400 MHz (ISM)": 2400,
  "5000 MHz (Wi-Fi 5)": 5000,
  "5800 MHz (Wi-Fi 6E)": 5800
})

freqMHz = freqMap[freqBandSelect]
wavelengthM = 300 / freqMHz
quarterWaveAntennaCm = (wavelengthM / 4) * 100
fspl = 20 * Math.log10(distanceKm) + 20 * Math.log10(freqMHz) + 32.45

html`<div style="background: linear-gradient(135deg, #2C3E50 0%, #16A085 100%); color: white; padding: 1.2rem; border-radius: 8px; font-family: Arial, sans-serif; margin: 0.5rem 0;">
<div style="display: grid; grid-template-columns: repeat(auto-fit, minmax(180px, 1fr)); gap: 1rem;">
  <div style="text-align: center;">
    <div style="font-size: 0.85rem; opacity: 0.85;">Frequency</div>
    <div style="font-size: 1.4rem; font-weight: bold;">${freqMHz} MHz</div>
  </div>
  <div style="text-align: center;">
    <div style="font-size: 0.85rem; opacity: 0.85;">Wavelength</div>
    <div style="font-size: 1.4rem; font-weight: bold;">${wavelengthM.toFixed(2)} m</div>
  </div>
  <div style="text-align: center;">
    <div style="font-size: 0.85rem; opacity: 0.85;">&lambda;/4 Antenna</div>
    <div style="font-size: 1.4rem; font-weight: bold;">${quarterWaveAntennaCm.toFixed(1)} cm</div>
  </div>
  <div style="text-align: center;">
    <div style="font-size: 0.85rem; opacity: 0.85;">FSPL at ${distanceKm} km</div>
    <div style="font-size: 1.4rem; font-weight: bold; color: #E67E22;">${fspl.toFixed(1)} dB</div>
  </div>
</div>
</div>`

9.7 Concept Relationships

Band	Advantage	Trade-off	Best For
2.4 GHz	Global, mature ecosystem	Congested	Smart home, BLE
5 GHz	More bandwidth, less interference	Shorter range	High-throughput
Sub-GHz	Long range, penetration	Regional variations	Rural IoT, LoRa
Licensed	Guaranteed QoS	Subscription fees	Cellular IoT
Unlicensed	Free to use	Shared, interference	Wi-Fi, Zigbee

Common Pitfalls

1. Violating Regional Duty Cycle Regulations

In Europe, the 868 MHz band has a maximum 1% duty cycle in sub-band g (869.4-869.65 MHz) but 0.1% in many others. Exceeding duty cycle limits is illegal and can result in regulatory fines. Always check ETSI EN 300 220 for European ISM band regulations.

2. Selecting 2.4 GHz for Dense Urban Deployments

2.4 GHz is severely congested in urban environments with Wi-Fi and Bluetooth. For outdoor urban IoT with many devices, sub-GHz bands (868/915 MHz) provide better range and less interference, at the cost of lower data rates. Choose frequency based on deployment environment, not convenience.

3. Confusing EIRP With Transmit Power

EIRP = transmit power + antenna gain - cable losses. A 20 dBm transmitter with a 6 dBi antenna produces 26 dBm EIRP — potentially violating 20 dBm EIRP limits. Always calculate EIRP for the complete antenna system, not just the radio output.

4. Ignoring 915 MHz Band Differences Between US and Europe

915 MHz operation is legal in the Americas but prohibited in most of Europe (European devices use 868 MHz). A device designed for US 915 MHz deployment cannot operate in European markets without hardware changes. Always design for the target market’s frequency regulations.

🏷️ Label the Diagram

💻 Code Challenge

9.8 Summary

This chapter covered IoT frequency bands and spectrum licensing:

2.4 GHz ISM band is globally available but congested; Wi-Fi channels 1, 6, 11 are non-overlapping; Zigbee channels 15, 20, 25, 26 avoid Wi-Fi interference
5 GHz band offers more bandwidth and less congestion but shorter range and requires DFS in some sub-bands
Sub-GHz bands (433, 868, 915 MHz) provide excellent range and penetration but vary by region
Licensed spectrum provides guaranteed QoS but requires fees; unlicensed ISM bands are free but shared
Regional regulations differ significantly; devices must comply with local power limits, duty cycles, and certification requirements

9.9 Try It Yourself

Try It Yourself: Channel Planning

Exercise: You’re deploying Zigbee sensors in an office with Wi-Fi on channels 1, 6, 11.

Which Zigbee channels (11-26) avoid Wi-Fi interference?
Why is channel 25 or 26 the safest choice?
Use a Wi-Fi analyzer app on your phone to find which channels your local networks use.
Plan Zigbee channels that avoid overlap.

9.10 See Also

Cellular Spectrum for IoT - LTE-M, NB-IoT bands
Wi-Fi Fundamentals - 2.4/5 GHz details
LoRaWAN Overview - Sub-GHz LPWAN

9.11 Knowledge Check

Quick Check: Frequency Bands and Licensing

Understanding Check: 2.4 GHz Spectrum Coexistence

Scenario: A 15-floor commercial building uses Wi-Fi for laptops/phones (channels 1, 6, 11) and Zigbee for 500 lighting sensors, thermostats, and door locks. Network ops reports: Zigbee sensors on floors 8-12 experience 20-40% packet loss during peak Wi-Fi usage (9-11am, 1-3pm). Wi-Fi operates at +20 dBm, Zigbee at 0 dBm (typical). Building has 3 Wi-Fi access points per floor using channels 1, 6, and 11.

Think about:

Why does a 22 MHz-wide Wi-Fi channel (e.g., channel 1 at 2.401-2.423 GHz) overlap multiple 2 MHz-wide Zigbee channels?
How does the 20 dB power difference (+20 dBm Wi-Fi vs 0 dBm Zigbee) affect interference visibility?
Which Zigbee channels (11-26) fall into the “gaps” between Wi-Fi channels 1, 6, and 11?

Key Insight: Careful channel planning eliminates interference without changing hardware:

The 2.4 GHz ISM Band Overlap:

Wi-Fi Channels (22 MHz wide):
Ch 1:  2401-2423 MHz  ████████████████████████
Ch 6:  2426-2448 MHz            ████████████████████████
Ch 11: 2451-2473 MHz                      ████████████████████████

Zigbee Channels (2 MHz wide):
Ch 11: 2405 MHz  ██
Ch 12: 2410 MHz    ██
Ch 13: 2415 MHz      ██
Ch 14: 2420 MHz        ██
Ch 15: 2425 MHz          ██  ← Between Wi-Fi 1 & 6
Ch 16: 2430 MHz            ██
...
Ch 20: 2450 MHz                        ██  ← Between Wi-Fi 6 & 11
...
Ch 25: 2475 MHz                                    ██  ← Above Wi-Fi 11
Ch 26: 2480 MHz                                      ██  ← Above Wi-Fi 11

Safe Zigbee Channels (non-overlapping with Wi-Fi 1, 6, 11):

Channel 15 (2425 MHz): Gap between Wi-Fi 1 and 6
Channel 20 (2450 MHz): Gap between Wi-Fi 6 and 11
Channel 25 (2475 MHz): Above Wi-Fi 11
Channel 26 (2480 MHz): Above Wi-Fi 11

Verify Your Understanding:

If you wanted to add Bluetooth devices on the same network, which Zigbee channels would you choose to minimize interference with both Wi-Fi and Bluetooth?
How would you use a spectrum analyzer to verify channel selection in a live deployment?

9.12 What’s Next

Chapter	Focus	Why Read It Next
Cellular Spectrum for IoT	LTE-M, NB-IoT band allocations, carrier aggregation	Apply your licensed vs unlicensed knowledge to evaluate how cellular IoT bands are allocated and managed globally
Propagation and Design	Path loss models, link budgets, interference mitigation	Extend the FSPL calculations from this chapter into real-world propagation models that account for walls, terrain, and fading
Wi-Fi Fundamentals	802.11 standards, channel bonding, OFDM modulation	Examine how Wi-Fi uses the 2.4 GHz and 5 GHz bands covered here with specific modulation and access control techniques
LoRaWAN Overview	Sub-GHz LPWAN, spreading factors, adaptive data rate	Investigate how LoRaWAN exploits the sub-GHz bands and duty cycle regulations discussed in this chapter