811  Mobile Wireless: Fundamentals

811.1 Introduction

⏱️ ~3 min | ⭐ Foundational | 📋 P08.C16.U01

Wireless connectivity is often where IoT deployments succeed or fail—not because a protocol is “good” or “bad,” but because frequency band choice, propagation, regulations, and power budgets were misunderstood. This section provides an overview of wireless fundamentals and guides you to detailed chapters on each topic.

NoteLearning Objectives

By the end of this section, you will understand:

  • The fundamental physics of electromagnetic waves for wireless communication
  • How different frequency bands (sub-GHz, 2.4 GHz, 5 GHz) trade off range, bandwidth, and penetration
  • The distinction between licensed and unlicensed spectrum
  • How cellular spectrum evolved and why NB-IoT/LTE-M exist
  • Practical design considerations for selecting a wireless band
NoteKey Takeaway

In one sentence: Frequency selection involves fundamental trade-offs - lower frequencies (sub-GHz) provide longer range and better penetration but less bandwidth, while higher frequencies (5 GHz+) offer more bandwidth but shorter range.

Remember this: Start with requirements (range, data rate, power budget) and work backwards to frequency - rural sensors need sub-GHz, smart home needs 2.4 GHz, video streaming needs 5+ GHz.

811.2 Chapter Overview

This comprehensive topic has been organized into four focused chapters for better learning:

811.2.1 1. Electromagnetic Waves and Spectrum Basics

Foundation concepts (~25 min reading time)

  • Electromagnetic wave properties: frequency, wavelength, energy
  • The wave equation: c = f × λ
  • The electromagnetic spectrum and where IoT operates
  • Radio frequency fundamentals for wireless communication

Start here if you need a refresher on the physics of wireless signals.

811.2.2 2. IoT Frequency Bands and Licensing

Practical band selection (~25 min reading time)

  • The 2.4 GHz ISM band: Wi-Fi, Bluetooth, Zigbee coexistence
  • The 5 GHz band: Higher bandwidth, shorter range
  • Sub-GHz bands: 433, 868, 915 MHz for long-range IoT
  • Licensed vs unlicensed spectrum trade-offs
  • Regional regulatory variations (FCC, ETSI, etc.)

Read this to understand which frequency band fits your IoT application.

811.2.3 3. Cellular Spectrum for IoT

Cellular IoT technologies (~20 min reading time)

  • Evolution from 1G to 5G: spectrum and efficiency
  • Multiple access techniques: FDMA → TDMA → CDMA → OFDMA
  • Low-band vs mid-band vs mmWave trade-offs
  • NB-IoT and LTE-M spectrum requirements
  • When to choose cellular over unlicensed spectrum

Read this if you’re considering cellular IoT technologies for wide-area coverage.

811.2.4 4. Wireless Propagation and Design

Design and deployment (~30 min reading time)

  • Free-space path loss (FSPL) calculations
  • Antenna trade-offs: directional vs omnidirectional
  • Interference sources and coexistence strategies
  • Frequency band selection framework
  • Practical design considerations for IoT

Read this when you’re ready to design and deploy a wireless IoT solution.

811.3 Prerequisites

Before diving into these chapters, you should be familiar with:

811.4 What’s Next After These Chapters

After completing the wireless fundamentals series:

811.5 Quick Reference

Frequency Band Range Bandwidth Penetration Best For
Sub-GHz (433/868/915 MHz) 10+ km 1-50 kbps Excellent Rural sensors, agriculture, meters
2.4 GHz 100-300m 250k-11M Good Smart home, wearables, building automation
5 GHz 50-100m 54M-1.2G Poor Video streaming, high-speed data
Cellular (low band) 10-30 km 5-20 Mbps Excellent Wide-area IoT, NB-IoT, LTE-M

Rule of thumb: Lower frequency = longer range + better penetration, but less bandwidth.