Types of Network 2 - Wireless computer networks

Learning Outcomes:

Understand the basic features of a wireless computer network in terms of its underlying technologies and the hardware used.

The common industry standards for wireless computer networks should be introduced to students. Relevant concepts including frequency, bandwidth, interference, and roaming, etc. are required.

Explain the factors that need to be considered in choosing between wired and wireless computer networks.

The strengths and weaknesses of both network solutions should be considered. The possibility of a hybrid solution should also be introduced to students.

Wireless technologies

NFC (near field communication): application e.g. Octopus card
RFID (Radio frequency identification): application: e.g. trace or identify objects with the RFID tags
Bluetooth: application: e.g. wireless headset
Wi-Fi: application: formation of WLAN

Wireless network standard

IEEE 802.11 is a standard for WLAN.
Different versions developed since its implementation. Latest ones are 802.11ac (WiFi 5) and 802.11ax (WiFi 6).
Different versions may have different frequency, bandwidth, data rate, MIMO (multiple input multiple output) and channels.

Collision handling

Devices

Similar to network interface card, the adapter allows a device to connect to the wireless network.

A hardware that connects to a wired network. It allows wireless connections by other devices using Wi-Fi technology to access the wired network.
Number of APs:

inadequate number results in insufficient coverage, low throughput and cannot provide adequate number of connections
Excessive number results in high installation cost and more complicated network management.

SSID (Service Set Identifier)

Essentially the name of the wireless network. Different wireless networks can have the same SSID, just like 2 people can have the same name. You may choose to broadcast or not to broadcast the SSID. (So that the network can or cannot be seen by others)
BSSID (Basic Service Set Identifier) is the unique identifier, similar to the MAC address, that allows unique identification of the access point.
Avoid using default SSID and password: to avoid confusion and reduce chance of being hacked

Password

For authentication.
Implementing password: reduce unauthorized access and sharing of bandwidth.
Not implementing password: easy to use, decrease setup time and no decryption time needed.

Channel

Using the 2.4GHz of 802.11n (Wi-Fi 4) as an example, the frequency ranges from 2400-2499MHz. This range is divided into 14 channels. Channel 1 ranges from 2402-2422 and channel 2 from 2407-2427. There is certain overlap of frequencies among adjacent channels. Therefore, it is recommended to use non-overlapping channels i.e. channel 1, 6 and 11. (1: 2402-2422, 6: 2427-2447, 11: 2452-2472)
If a nearby AP is using, for example, channel 1, it is better to use channel 6 or 11 for your AP.
Another option is to use automatic channel selection, which selects channel with least inference.

Encryption

Roaming

A device can remain connected to a network when moving from one AP to another of the same network, without any interruption. This is known as seamless roaming.
Essential settings: the APs should have the same SSID, password and encryption methods.
For roaming to succeed, the adjacent APs should have certain overlapping signals so that connection is not lost when moving from one AP to another AP. Since there is overlapping signals, their channels should be non-overlapping. Otherwise interference occurs.

Relevant pastpaper:

DSE ICT Elec B(SP-2017): PP 1cii, 4abc. 2012 1bi,e. 2013 1d, 3aii,bcd. 2014 1e, 4cii. 2015 1bi, 3ei,ii. 2016 1abce. 2017 1d.

CE CIT Elec C(2005-2011): 2008 2bcd. 2009 1ef. 2011 1d, 2bc.

AS CA(2000-2013): 2007 9f. 2008 2b. 2011 1bc. 2012 7b, 10aii.