Network Media
Data and information can be encoded in electromagnetic signals and exchanged either physically (wired) or through space (wirelessly). Modern electronic devices can then decode those signals and communicate with other such devices. 1
Wired Connections
When using wired connections, electromagnetic waves are sent along physical conductors (typically copper) to carry data from one end to another. In this section we will mainly discuss the transfer of data, but note that this principle can also be used to carry electric power in the form of a steady current (either AC or DC). Some cables are designed to only carry either data (like standard Ethernet) or power (like DC adapters), while others (like USB) are designed to carry both.
Twisted Pair Cable
The most popular form of traditional copper-wired cables is the twisted pair cable, which can also be called a CAT# cable. Standard CAT5 cable contains 4 pairs of wires, and older phone cable is CAT3, with 2 pairs of wires. There is also CAT5E, an upgraded version of CAT5, and CAT6 which is recommended for gigabit Ethernet.
Figure 1a: Twisted Pair Cable
These copper wires are crimped into a plastic RJ-45 connector, which is similar to a telephone cable connector.
Twisted pair is susceptible to interference, therefore CAT5 can only run a maximum of 100m or 320 ft. before signal loss occurs. CAT5E can run to 350m and CAT6 to 550m.
Coaxial Cable
Coaxial cable is the second form of commonly used wired media. Coaxial cabling has a single copper conductor at its center, and a plastic layer that provides insulation between the center conductor and a braided metal shield. The metal shield helps block any outside interference from fluorescent lights, motors, or other computers.
Figure 2: Coaxial Cable
Coaxial cable provides good insulation and durability. This wire is best suited for long, one way connections between devices. Coaxial cable is less susceptible to interference than twisted pair cable. High quality coax cable supports a maximum length of 500m before signal loss is experienced.
Fiber Optic Connections
Fiber optic cables are the fastest option for wired and wireless connections. These cables use pulses of light traveling at or near the speed of light for long distances inside small strands of translucent fibers. The translucent plastic or glass fibers form the core of the cable, and are encased in a plastic coating for cushioning. Around the cushion are Kevlar fibers that protect the cable from breaking. Beyond the Kevlar is an outer Teflon or PVC coating that contains the wire system.
Figure 3: Fiber Optic Cable
Fiber optic cabling is not susceptible to electronic interference like traditional copper wired connections because data travels as light pulses. Fiber optic cables can run 145km (90mi) without signal loss.
| Feature | Twisted-Pair Cable | Coaxial Cable | Fiber Optic Cable |
|---|---|---|---|
| Structure | Two insulated copper wires twisted together | Central conductor, insulating layer, metallic shield, outer insulating layer | Core of glass or plastic fibers, cladding, protective outer layer |
| Bandwidth | Up to 1 Gbps for Cat 5e, higher for Cat 6, Cat 7 | Up to 10 Mbps (traditional), higher for modern cables | 10 Gbps to 100 Gbps and beyond |
| Distance | Up to 100 meters | Up to 500 meters for broadband, 185 meters for baseband | Up to 40 km for single-mode, 2 km for multi-mode |
| Interference | Susceptible to electromagnetic interference | Better resistance to interference than twisted-pair | Immune to electromagnetic interference |
| Cost | Low | Moderate | High |
| Security | Moderate (can be tapped with physical access) | Higher security due to shielding | Very secure (difficult to tap) |
| Applications | Local Area Networks (LANs), telephone networks | Cable TV, internet, and telecommunications | Backbone networks, long-distance communication |
Wireless Connections
802.11 Wireless Standards
Wireless communications typically use radio frequencies to broadcast a signal. The development of wireless computer communication is controlled and documented by the Institute of Electrical and Electronics Engineers (IEEE) 802.11 wireless standards. The 802.11 standard specifies an over-the-air interface between a wireless client and a base station, or between two wireless clients. This method of communication is known as Wi-Fi.
There are several specifications in the 802.11 family:
| Standard | Frequency (Ghz) | Max Speed (Mbps) | Range (ft) |
|---|---|---|---|
| 802.11a | 5 | 54 | 115 |
| 802.11b | 2.4 | 11 | 100 |
| 802.11g | 2.4 | 54 | 140 |
| 802.11n | 5 | 450 | 230 |
| 802.11ac | 5 | 1300 | 230 |
| 802.11ax | 5 – 6 | 9608 | variable |
For a more detailed table about the 802.11 wireless standard variations, see: https://en.wikipedia.org/wiki/Wi-Fi
Other Wireless Methods:
Multiple-Input and Multiple-Output (MIMO) is a type of “smart antenna” technology implemented in the 802.11n wireless standard. MIMO uses multiple antennas on both the receiving end and the transmitting end of a connection to boost communication performance.
Bluetooth allows for short ranged wireless networks to be established, and is used most often to establish networks between devices and a computer, or a similarly controlled device. Keyboards, mice, and joysticks can all have Bluetooth capability. Additionally, nearly all cell phones are Bluetooth capable for hands-free use of the device, or to sync the device to a computer. Most Bluetooth devices have a range of 10m, but the technology does allow for ranges up to 100m. Bluetooth operates in the 2.45 GHz band. Bluetooth 2.0 allows transmissions speeds up to 2.1 Mbit/s. Bluetooth 3.0 supports speeds up to 24 Mbit/s.
Cell Phone Internet/WiMax
Cell Phones use the same protocols as computers when accessing a network, but the physical network they connect to is different. The main standard for cell phone network connections is the G standard, such as 3G or 4G. This refers to a standard set by the International Telecommunication Union, and is based on a minimum speed to transfer data between the phone and a cell phone tower. 3G has a base of 200kb/s, and 4G has a minimum speed of 100 Mb/s. Speeds up to approximately 1 Gb/s are possible.
Worldwide Interoperability for Microwave Access (WiMAX) is a form of broadband internet, which operates over the same signals cell phones use. It’s defined under IEEE protocol 802.16 and offers 40MB/s of data transfer. A pending version will offer up to 1GB/s of bandwidth. Using existing cell phone towers and additional hardware, WiMAX is being used in many metropolitan areas, with the intent of making it the first national broadband system in the US.