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graph TB
App["Application Layer<br/>(MQTT, CoAP, HTTP)"]
Trans["Transport Layer<br/>(TCP, UDP)"]
Net["Network Layer<br/>(IP, RPL)"]
Access["Network Access Layer<br/>(MAC, LLC)"]
Phys["Physical Layer<br/>(Radio, Wired)"]
App --> Trans
Trans --> Net
Net --> Access
Access --> Phys
style App fill:#7F8C8D,stroke:#2C3E50,color:#fff
style Trans fill:#7F8C8D,stroke:#2C3E50,color:#fff
style Net fill:#7F8C8D,stroke:#2C3E50,color:#fff
style Access fill:#E67E22,stroke:#2C3E50,color:#fff,stroke-width:3px
style Phys fill:#2C3E50,stroke:#16A085,color:#fff,stroke-width:3px
796 Network Access and Physical Layer Protocols
NoteLearning Objectives
By the end of this section, you will be able to:
- Understand the role of network access and physical layer protocols in IoT
- Compare and contrast wired (Ethernet) and wireless (Wi-Fi, Zigbee, LoRa, Cellular) protocols
- Map IoT protocols to network classifications (PAN, LAN, WAN)
- Evaluate protocol selection based on bandwidth and coverage requirements
- Understand the evolution of cellular protocols for IoT (2G to 5G)
- Select appropriate protocols for different IoT deployment scenarios
796.1 Prerequisites
Before diving into this chapter, you should be familiar with:
- Networking Basics: Understanding fundamental networking concepts including the OSI model, protocol layers, and basic data transmission principles is essential for grasping network access layer functions
- Basic Electronics: Familiarity with radio frequencies, signal transmission, and electromagnetic spectrum helps you understand physical layer wireless technologies
- Communication Fundamentals: Knowledge of concepts like bandwidth, data rates, modulation, and error correction provides foundation for comparing different physical layer protocols
TipFor Kids: Meet the Sensor Squad!
Network access and physical layers are like the roads and vehicles that carry messages between friends who live far apart!
796.1.1 The Sensor Squad Adventure: The Great Message Relay Race
Sammy the Sensor had exciting news to share with his friend Max the Microcontroller, who lived all the way across Sensor City. But there was a problem - Sammy couldn’t just shout loud enough for Max to hear!
“I need to send my temperature reading to Max,” Sammy said. “But he’s SO far away!”
Lila the LED had an idea. “We need a MESSENGER! Like how people used to send letters on horseback!”
Just then, they met three different messengers, each with their own special transportation:
Ethel the Ethernet Cable said, “I travel on WIRES! I’m super fast and reliable, but I can only go where my cables are laid - like a train on tracks!”
Wally the Wi-Fi Wave said, “I fly through the AIR as invisible radio waves! I can reach anywhere in this room, but walls slow me down and I get tired after about 100 meters.”
Lori the LoRa Signal said, “I travel through the air too, but I use SPECIAL radio waves that can go REALLY far - even 10 kilometers! But I can only carry small messages, like postcards instead of packages.”
Sammy thought carefully. His temperature reading was just a small number, Max was on the other side of the city, and there were no wires between them.
“Lori the LoRa, you’re perfect for this job!” Sammy cheered.
The Sensor Squad learned that just like choosing between walking, biking, driving, or flying for a trip, IoT devices must choose the RIGHT way to send their messages based on how far, how fast, and how much data needs to travel!
796.1.2 Key Words for Kids
| Word | What It Means |
|---|---|
| Physical Layer | The actual “roads” that carry messages - wires, radio waves, or light beams |
| Wi-Fi | Invisible radio waves that let devices talk to each other through the air (short range) |
| Ethernet | Super-fast messages that travel through special cables (like telephone wires for computers) |
| LoRa | Special radio waves that can travel REALLY far but carry small messages |
| Bandwidth | How much “stuff” you can send at once - like a skinny pipe vs. a fat pipe for water |
TipFor Beginners: Network Access and Physical Layers
When you hear “networking,” you might think of Wi-Fi or Ethernet cables. But underneath those familiar terms are two critical OSI layers: the Physical Layer (Layer 1) and the Data Link/Network Access Layer (Layer 2). These are the foundation of all network communication.
Physical Layer answers: “How do bits physically travel?” Through copper wires? Radio waves? Fiber optic light? It defines voltages, frequencies, and physical connectors.
Network Access Layer answers: “How do devices share the physical medium and address each other locally?” It handles MAC addresses, frame formatting, and media access control.
| Term | Simple Explanation |
|---|---|
| Physical Layer | How bits physically travel—wires, radio waves, light pulses |
| Network Access Layer | How devices share medium and address each other locally |
| Ethernet (802.3) | Wired LAN protocol—reliable, high bandwidth, requires cables |
| Wi-Fi (802.11) | Wireless LAN—high bandwidth, short range (50-100m indoors) |
| 802.15.4 | Low-power wireless—foundation for Zigbee, Thread |
| LoRa | Long-range radio—kilometers of range on low power |
| Cellular | Mobile networks—ubiquitous coverage, higher power and cost |
TipMVU: Medium Access Control (MAC)
Core Concept: MAC protocols determine when devices can transmit on a shared medium - using methods like CSMA/CA (listen before talk) or TDMA (assigned time slots) to prevent collisions when multiple devices want to communicate simultaneously.
Why It Matters: In IoT networks with hundreds of sensors sharing one wireless channel, uncoordinated transmission causes collisions that waste energy and bandwidth. MAC efficiency directly impacts battery life and network capacity.
Key Takeaway: Choose CSMA/CA for low-traffic sporadic sensors (Wi-Fi, Zigbee), TDMA for deterministic industrial control (WirelessHART), and understand that MAC overhead can consume 20-50% of available airtime in dense IoT deployments.
796.2 Chapter Overview
The network access and physical layers form the foundation of IoT connectivity. These protocols define how devices physically connect to networks and how data is transmitted over communication media (wired or wireless).
This section is divided into four focused chapters covering all aspects of network access and physical layer protocols:
796.4 What’s Next?
Start with Wired Network Access: Ethernet for IoT to understand when and why wired connectivity remains essential for IoT, then progress through wireless technologies to build a complete understanding of network access options.