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Infrared (IR)

19 January, 2016 - 15:03

It is a common experience for us to use infrared (IR) signalling to change channels on a TV via a TV remote. IR signals depend on a line-of-sight transmission path between the sender and receiver. This has in fact hindered the application of IR from advancing beyond remote controlling and peripherals connection. IR signals occur at very high frequencies, in the 300- to 300,000-Ghz range, just above the visible spectrum of light.

Table 1.2 offers a comparison of the common wireless networking standards, their ranges and throughputs.

Table 1.2 Comparison of the common wireless networking standards


Frequency range

Theoretical maximum throughput

Effective throughput (approximate)

Average geographic range

802.11b   ("Wi-Fi")

2.4 GHz

11 Mbps

5 Mbps

100 meters   (or approximately 330 feet)


5 GHz

54 Mbps

11–18 Mbps

20 meters   (or approximately 66 feet)


2.4 GHz

54 Mbps

20–25 Mbps

100 meters   (or approximately 330 feet)

Bluetooth ver. 1.x

2.4 GHz

1 Mbps

723 Kbps

10 meters   (or approximately 33 feet)

Bluetooth ver. 2.0

2.4 GHz

2.1 Mbps

1.5 Mbps

30 meters   (or approximately 100 feet)


300–300,000 GHz

4 Mbps

3.5 Mbps

1 meter   (or approximately 3.3 feet)


Source: Dean 2006. 4e

Now, read the following material to learn more about wireless network protocols:


Dean (2010) 373–83.

To see if you have understood the topics we have covered so far, attempt Self-test 2 on your own before checking the Suggested answers to Self-test 2.

In practice, 802.11b and 802.11g wireless transmission technologies are more commonly used in business LANs than Bluetooth. Can you think of some underlying reasons? Complete Activity 2 and take a look at its Feedback to Activity 2 afterwards.