Wireless Compared, and Wired vs
The three wireless media differ in one thing above all: frequency. As the frequency rises from radio to microwaves to infrared, the waves stop spreading in all directions, stop passing through walls, and work over shorter distances.
1The three waves, lowest frequency to highest
| Radio waves | Microwaves | Infrared waves | |
|---|---|---|---|
| Frequency (NCERT) | 3 KHz – 1 GHz | 1 GHz – 300 GHz | 300 GHz – 400 THz |
| Direction | Omni-directional: all directions | Unidirectional: one direction | Point-to-point, one direction |
| Line of sight needed? | No | Yes | Yes |
| Through walls? | Yes (low frequencies) | No — nor hills or mountains | No |
| Distance | Long | Long, with towers, repeaters or satellites | Short |
| Antenna | Simple antenna, any direction | Dish antennas facing each other | A small bulb, pointed at the receiver |
| Uses | AM/FM radio, television, cordless phones | Radar, satellites, long point-to-point links | TV remote control |
Compare radio, microwave and infrared between the same two blocks. Drag sideways to turn.
Not to scale. In the infrared view the two blocks are much too far apart for infrared, which is the point.
2Wired vs wireless
| Wired (guided) | Wireless (unguided) | |
|---|---|---|
| Signal travels | Along a cable | Through the air, as electromagnetic waves |
| Speed and reliability | Usually faster and more reliable | Can be slower; affected by distance, walls and weather |
| Interference | Less (and none for fibre) | More |
| Security | More secure: someone must reach the cable | Less secure: anyone in range can pick up the signal |
| Setting up | Cables must be laid: costly and slow over long or difficult routes | No cables: easier across rivers, hills and cities |
| Moving around | Devices stay where the cable is | Devices can move: phones, laptops |
▶Show the answer
Advantage: wired communication is more reliable and secure, and faster, because the signal is guided along a cable and suffers less interference.
Disadvantage: cables must be laid to every device, which is costly and difficult over long distances or difficult ground, and devices cannot move freely.
3Name the medium
Read the situation and pick the medium.
4Check yourself
Which wireless medium can travel in all directions and pass through walls?
A company wants a wireless link between offices in two cities. Which medium fits best?