Wireless Communications (Edexcel IGCSE Ict)

Wi-Fi

Spec point — 2.1.4

What is Wi-Fi?

• Wireless fidelity (Wi-Fi) is a common standard for wireless networks

• Wi-Fi is common in most homes and offices to connect devices such as laptops, tablets& smart phones

• Using Wi-Fi, devices communicate with a hotspot or a wireless access point (WAP), which can be a standalone device or built into a router or switch

• Wi-Fi may be preferred over Bluetooth when:

  • High speed data transfer is required
  • Long range communication is required
  • Many devices are needed to be connected at the same time

Bluetooth

Spec point — 2.1.4

What is Bluetooth?

• Bluetooth is another common standard for wireless networks
• Bluetooth is common in most homes and offices to connect devices such as headphones, controllers, keyboards& mice
• Bluetooth is used typically for a direct connection between two devices
• When two devices pair, they both exchange a cryptographic key
• The keys are used to generate a secret shared key which is used to encrypt the data between the two devices and create a Wireless Personal Area Network (WPAN)
• Connected devices continuously change their transmitting frequency between 79 different channels to avoid interference and improve the reliability of the connection
• This is known as the frequency hopping spread spectrum (FHSS)

Differences between Bluetooth and Wi-Fi

GPS

Spec point — 2.1.3

What is GPS?

• Global Positioning System (GPS) is a satellite system used to track the exact location of an object
• GPS uses orbiting satellites to receive, amplify and transmit signals
• **Radio frequencies are used **to communicate between satellites and ground stations
• GPS** requires a direct line of sight**

Case Study Sat nav in a car

• The position/location of the car is calculated using GPS software
• Data is transmitted every few seconds
• An algorithm calculates the speed/location of the car
• The map is updated every few seconds

3G & 4G

Spec point — 2.1.3

What is 3G & 4G?

• 3G and 4G are references to the 3rd and 4th generation of mobile data networks

• They provide mobile devices with wireless access to the internet

• Each generation has a faster transfer rate and an improved capacity for more users

  • 3G - 256 Kbps (kilobits per second)
  • 4G - 100+ Mbps (megabits per second)

• The current generation (5G) has even faster speeds and lower latency

Infra-red (IR)

Spec point — 2.1.3

What is infra-red?

• Infra-red is a wireless communication method used to transfer very small amounts of data to a device in direct line of sight

• Commonly used in remotes to control devices such as:

  • Televisions
  • Audio receivers
  • Home entertainment equipment etc.

• Uses light waves which can cause:

  • Walls or obstacles to block the signal
  • Sunlight to affect the signal

• It is a reliable and cost effective solution for many short-range wireless communication needs

NFC

Spec point — 2.1.3

What is NFC?

• Near field communication (NFC) is a subset of RFID which allows communication between two devices in very close proximity

• NFC can be either:

  • Passive- uses energy from the reader
  • Active- has it's own power source

• Smartphones use **active NFC to allow contactless payments **by tapping a smartphone on a reader

• Smartphones can also** exchange data using NFC** by tapping together (usually back to back)

Worked Example George uses a smartwatch when he exercises outside.

The smartwatch connects to a wireless health monitor to track his heart rate.

The health monitor uses Wi-Fi to transfer data to the smartwatch.

A. Speed is not a concern. Explain why Wi-Fi is a better choice than infrared for this transfer

[2]

B. Explain why distance might affect the speed of the transfer

[2]

Answers

*A. **An explanation such as: *

• Wi-Fi does not require line of sight / Infrared requires line of sight** [1] which is not always possible when moving/exercising [1]

OR

• Infrared is / Wi-Fi is not affected by sunlight [1] (which will affect the data transfer because) the health monitor will be used outside [1]

B. An explanation to include two from:

• More packets of data have to be requested again [1]
• ...because a signal degrades / gets weaker as it travels [1]
• ...due to (more opportunities for) interference / spreading out of the radio waves [1]