Media Layers - Wired Network Protocols
While the IoT ecosystem is usually considered to be composed of wireless devices, it is still possible to connect IoT solutions using a wired connection.
When wireless-enabled SoCs were about to be delivered to the market (e.g. ESP8266), extension devices were already available for popular embedded systems, like Ethernet Shield for Arduino boards (figure 1).
Copper-based wired networks also bring an extra feature to the IoT designers – an ability to power the device via a wired connection, e.g. PoE (Power over Ethernet) – 802.3af, 802.3at, 802.3bt [1]. Long-distance connections may be implemented using optic-based, fibre connections, but those require physical medium converters that are usually quite complex, pretty expensive and power consuming; thus, they apply only to the niche IoT solutions.
The mentioned optical connections do not cover so-called LiFi, as those are considered to be of a wireless nature[2].
A non-exhaustive list of some present and former wired networking solutions is presented in table 1.
Table 1: A Short Review of the Most Popular Wired Networking Standards
| Name | Communication medium | Max speed | Topology | Max range (single segment, passive) |
|---|---|---|---|---|
| Ethernet | Twisted pair: 10BaseT Coaxial: 10Base2/10Base5 Fibre: 10BaseF | 10 Mbps | Bus, Star, Mixed (Tree) | 10Base2: 0.5–200 m (185 m) 10Base5: 500 m 10BaseT: 100 m (150 m) 10BaseF: 2 km (multimode fibre) |
| Fast Ethernet | Twisted pair: 100BaseTx Fibre: 100BaseFx | 100 Mbps | Star | 100BaseTx: 100 m (Cat 5) 100BaseFx: 2 km |
| Gigabit Ethernet | Twisted pair: 1000BaseT Fibre: 1000BaseX (LX/CX/SX) | 1000BaseT: 1 Gbps 1000BaseX: 4.268 Gbps | Star | 1000BaseT: 100 m (Cat 5) 1000BaseLX: 5 km |
| Local Talk (Apple) | Twisted pair | 0.23 Mbps | Bus, Star (PhoneNet) | 1000 ft |
| Token ring | Twisted pair | 16 Mbps | Star wired ring | 22.5 m / 100 m (cable dependent) |
| FDDI | Fibre | 100 Mbps (200 Mbps on two rings, but no redundancy) | Dual ring | 2 km |
The most popular wired networks are 10/100/1000 BaseT – twisted pair with Cat 5, 5e and 6 cables. They require the IoT system to implement a full TCP/IP stack to operate seamlessly with conventional Internet/Intranet/Extranet networks. Because it is usually out of the scope of standard Arduino Uno processor capabilities to implement a full TCP stack, there are typically dedicated processors on the network interfaces that assist the central processor or even handle all networking tasks themselves.
