2.1.4 Wired, Wireless and Satellite Communication
Every network needs a way to carry signals between devices. The most suitable method depends on the distance, required data rate, environment, mobility, security and available budget.
This section compares copper cable, fibre-optic cable, radio communication including WiFi, microwave links and satellite communication. It also examines the practical consequences of choosing a wired or wireless network.
By the end of this section, you should be able to:
- describe how copper, fibre and wireless media carry signals;
- compare copper cable with fibre-optic cable;
- explain how radio waves are used by WiFi;
- describe the characteristics of terrestrial microwave and satellite links;
- compare wired and wireless networks using relevant technical and practical factors;
- select and justify a suitable communication medium for a given situation.
Start with the communication requirement
A medium should not be selected simply because it is the fastest or newest option. The decision should begin with the requirements of the network.
| Decision factor | Question to ask |
|---|---|
| Bandwidth | How much data must be transferred each second? |
| Distance and attenuation | How far must the signal travel before it becomes too weak? |
| Interference | Could electrical equipment, other transmitters, weather or physical obstacles disturb the signal? |
| Mobility | Must users remain connected while moving? |
| Security | Can the signal be intercepted outside the intended physical area? |
| Installation and cost | Can cables be laid, towers installed or satellite equipment afforded? |
| Reliability | What should happen when a cable, link or transmitter becomes unavailable? |
Attenuation: the reduction in signal strength as a signal travels.
Exam tip
Use a three-part explanation: requirement → relevant characteristic → practical consequence. For example, fibre is suitable for a high-traffic building backbone because its high bandwidth allows many users' data to be carried at the same time.
How the different media carry data
| Medium | Signal carrier | Typical network role |
|---|---|---|
| Copper cable | Changing electrical signals in a conductor | Connections inside homes, offices and local networks |
| Fibre-optic cable | Pulses of light travelling through glass or plastic fibre | High-capacity backbones and long-distance links |
| Radio / WiFi | Radio-frequency electromagnetic waves through the air | Local wireless access and mobile connectivity |
| Terrestrial microwave | Highly directional radio-frequency signals | Point-to-point links between fixed locations |
| Satellite link | Radio or microwave signals relayed through an orbiting satellite | Wide-area coverage and access in remote locations |
Common mistake
A satellite is not a different kind of electromagnetic wave. It is a relay platform: ground stations communicate with it using radio-frequency or microwave signals.
Copper cable
Copper media represent binary data using changing electrical signals. Two common forms are twisted-pair cable and coaxial cable.
Twisted-pair cable
Twisted-pair cable contains insulated copper wires arranged in pairs. Twisting the conductors helps reduce the effect of interference and crosstalk. It is flexible, comparatively inexpensive and widely used for Ethernet connections inside buildings.
Coaxial cable
Coaxial cable has a central copper conductor surrounded by insulation and a conductive shield. The shielding provides stronger protection from interference than unshielded twisted pair. Coaxial cable is used in systems such as cable broadband and some specialist installations, although it is less common for modern desktop LAN connections.
| Characteristic | Implication of using copper |
|---|---|
| Cost and installation | Usually economical and familiar to installers, particularly for short building runs. |
| Electrical interference | Motors, power cables and other electrical sources can disturb the signal; shielding and correct installation reduce the risk. |
| Attenuation | Signal quality decreases with distance, so link length is limited and repeaters or switches may be required. |
| Bandwidth | Suitable copper standards can support fast LAN links, but fibre offers greater capacity over longer distances. |
| Physical access | An attacker normally needs access to the cable or network equipment to intercept the signal. |
Common mistake
“Copper is slow” is too vague. Performance depends on the cable standard, distance, installation quality and network equipment. Compare it with the requirement in the question.
Fibre-optic cable
Fibre-optic cable represents data using pulses of light. The light is guided through a thin core, allowing signals to travel quickly over long distances with relatively low attenuation.
| Characteristic | Practical consequence |
|---|---|
| High bandwidth | Large volumes of traffic can be carried, making fibre suitable for backbones and busy links. |
| Low attenuation | Signals can travel further before regeneration is required. |
| Immunity to electromagnetic interference | Nearby electrical machinery does not disrupt the light signal. |
| No electrical conductor in the fibre | It is useful where electrical isolation is important and does not radiate an electrical signal in the same way as copper. |
| Specialised installation | Termination, testing and repair may require specialist tools and trained technicians. |
| Higher initial cost in some settings | Replacing a satisfactory existing copper installation may not be economically justified. |
Example decision
A media company needs to connect two equipment rooms carrying many simultaneous high-resolution video transfers. Fibre is a strong choice because its bandwidth and low attenuation support a high-capacity backbone. The company must still consider installation cost and suitable network interfaces.
Common mistake
Fibre often provides the strongest performance, but it is not automatically the best answer. A short, low-traffic link may not justify replacing an existing copper connection.
Radio waves and WiFi
WiFi uses radio waves to carry data between a wireless device and a wireless access point. The access point then connects the wireless part of the network to the rest of the LAN.
Characteristics of WiFi communication
- Users can remain connected while moving within the coverage area.
- New devices can be connected without installing a separate data cable to every location.
- Radio signals are affected by distance, walls, building materials and other transmitters.
- Available capacity is shared by devices using the same wireless channel.
- The signal may extend beyond the building, so authentication and encryption are essential.
- Coverage can be expanded with additional access points, but their placement and channels must be planned.
Example decision
A museum in a protected historic building needs visitor tablets to connect in several galleries. WiFi avoids extensive new cabling and supports mobility. However, the network designer must test coverage around thick walls and use secure access controls.
Common mistake
Wireless does not mean that the entire network has no cables. Wireless access points normally connect to a wired network and require power.
Terrestrial microwave communication
Microwaves are part of the radio-frequency spectrum, but they are commonly treated separately because they can be focused into a narrow, directional beam.
Characteristics
- Directional antennas can create a point-to-point link between fixed locations.
- A clear line of sight is normally required; buildings, terrain or poor alignment can block the path.
- The link can provide high data rates without laying a cable between the sites.
- Weather and atmospheric conditions can weaken some microwave links.
- Antennas, towers, alignment and permitted frequency use can increase cost and complexity.
Example decision
Two university buildings are separated by a river, and both rooftops are visible from each other. A directional microwave link could avoid the cost and permissions required to lay a new cable. It would be unsuitable if a future building were likely to obstruct the line of sight.
Exam tip
For a microwave answer, connect directional transmission to line of sight. The narrow beam can carry data between fixed points, but an obstacle in the path can interrupt the link.
Satellite communication
A satellite link uses an uplink from a ground station to a satellite and a downlink from the satellite to another ground station or user terminal. This allows communication over very large areas without a continuous terrestrial cable.
| Orbit group | General characteristic | Communication implication |
|---|---|---|
| Geostationary Earth orbit (GEO) | Appears fixed above one part of Earth and covers a very large area. | Ground antennas can point in one direction, but the long signal path creates noticeable latency. |
| Medium Earth orbit (MEO) | Operates below GEO and moves relative to the ground. | Offers a compromise between coverage and delay; also used by navigation systems. |
| Low Earth orbit (LEO) | Operates much closer to Earth and covers a smaller area at one time. | Can provide lower latency, but many satellites and handovers are required for continuous wide coverage. |
Benefits and drawbacks
| Benefit | Related drawback or limitation |
|---|---|
| Can reach remote, rural, maritime or disaster-affected locations | Terminals and service can be expensive compared with an available terrestrial connection. |
| Covers large geographical areas | Capacity is shared across users within the coverage area. |
| Does not require a cable along the full route | Weather, obstacles and antenna alignment may affect the radio-frequency link. |
| Can restore communication when ground infrastructure is damaged | Latency depends strongly on orbital altitude and the complete signal path. |
Common mistake
Satellite delay is mainly caused by the distance travelled, not because the signal moves slowly. GEO links have a much longer path than LEO links and therefore usually have greater latency.
Implications of using wired and wireless networks
| Factor | Wired network | Wireless network |
|---|---|---|
| Mobility | Devices are connected at fixed cable points. | Users can move within the radio coverage area. |
| Performance | Usually provides stable throughput and low latency; fibre offers very high capacity. | Throughput varies with distance, interference and the number of devices sharing the channel. |
| Installation | Requires cable routes, ports and physical access to the building. | Can reduce cabling to end devices, but access points and coverage planning are still required. |
| Reliability | Not affected by radio interference, but damaged cables or ports interrupt connections. | Can be disrupted by obstacles, competing transmitters and changes in the environment. |
| Security | Interception normally requires physical access to cabling or equipment. | Signals may be received outside the intended area, increasing the importance of encryption and authentication. |
| Expansion | New devices may need new cable runs and switch ports. | Devices can join without new data cabling, but extra access points may be needed as demand grows. |
Most real networks use both
A school might use fibre between buildings, copper Ethernet for fixed desktop computers, and WiFi for tablets and laptops. This is not a contradiction: each medium is selected for a different requirement.
Exam tip
Avoid writing “wired is better” or “wireless is easier”. State the relevant condition: wireless supports mobility, whereas a wired link usually provides more predictable performance and keeps the signal within a physical path.
Interactive: Transmission Media Explorer
Switch between cable, wireless and satellite views, then select a medium to compare its strengths, limitations and typical uses.
Extension note
The existing explorer may also include infrared for comparison. The main syllabus focus on this page is copper, fibre-optic cable, radio and WiFi, microwave and satellite communication.
Practice
Explain the technology
- Describe how copper cable and fibre-optic cable carry data differently.
- Explain why fibre is less affected by electromagnetic interference than copper.
- Explain two reasons why WiFi performance may vary as a user moves through a building.
- Explain why a terrestrial microwave link normally requires line of sight.
- Describe the uplink and downlink in a satellite communication system.
- Explain why GEO satellite communication normally has greater latency than LEO communication.
Select and justify a medium
- A factory needs a high-capacity backbone near powerful electrical machinery.
- A temporary outdoor event needs mobile network access without installing cables to every device.
- Two visible hilltop stations need a fixed link across difficult terrain.
- A remote island clinic has no practical terrestrial broadband connection.
- An office needs reliable fixed connections for desktop computers and mobile access for visitors.
For each scenario, choose a suitable medium and link one technical characteristic to the stated requirement.
Review
| Medium | Strong reason to use it | Important limitation |
|---|---|---|
| Copper cable | Economical and practical for many short local links | Electrical interference and greater attenuation than fibre |
| Fibre-optic cable | High bandwidth, low attenuation and immunity to electromagnetic interference | Specialist installation and potentially higher initial cost |
| Radio / WiFi | Mobility and flexible local access | Shared capacity, interference and security exposure beyond physical walls |
| Terrestrial microwave | Directional high-capacity link without laying cable | Requires line of sight and careful alignment |
| Satellite | Very wide reach, including remote locations | Cost, shared capacity, weather effects and propagation delay |
Quick self-check
- Can I compare copper and fibre through signal type, bandwidth, attenuation and interference?
- Can I explain how WiFi uses radio waves?
- Can I connect microwave directionality to line-of-sight requirements?
- Can I explain how a satellite relays a signal?
- Can I justify wired, wireless or mixed networking for a scenario?