IEEE 802.11 WiFi Standards Backward Compatibility: Study Notes for Kerala PSC, SSC, and IT Exams

The IEEE 802.11 standards are a core part of the Networking & Data Communication syllabus for the Kerala PSC Degree Level Exam, SSC Scientific Assistant, and ISRO VSSC Technical Assistant posts. Understanding frequency bands and backward compatibility is essential for the Technical Assistant and Computer Assistant exams.

SSC, DSSSB, and Kerala PSC conduct examinations for various IT posts.

Understanding IEEE 802.11 standards is essential for candidates appearing for the Kerala PSC Degree Level Exam, SSC Scientific Assistant (CS), and System Analyst posts. These networking fundamentals are core parts of the Computer Science syllabus.

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Kerala PSC Degree Level examinations have a Computer Science section where students can expect questions from this topic. You can check the Kerala PSC Degree Level Common Prelims Syllabus under the Computer Science section. I recommend you download the syllabus using this official link.

Reference: https://www.keralapsc.gov.in/sites/default/files/2021-02/syllubus.pdf

WiFi is the term used to denote Wireless Local Area Networks using IEEE802.11 wireless standards. Now, the term WiFi represents all Wireless Local Area Networks.

The first part of this tutorial checks the term WiFi and the major 802.11 standards. You can also see a list of WiFi devices that support them.

You will get a backward compatibility checker chart in the last part of this tutorial.

With the help of the chart, you can avoid buying a device with compatibility issues with existing devices (standards that are not backward compatible).

1. IEEE 802.11 A
   
   
2. IEEE 802.11 B
   
   
3. IEEE 802.11 G
   
   
4. IEEE 802.11 N
   
   
5. IEEE 802.11 AC

Not all 802.11 technologies are backward compatible because of the different frequencies supported. So, if you plan to extend your current WLAN with new devices, ensure the new devices are compatible with existing devices.

Once you have noted down the technologies (that are in your network), you may check which 802.11 standards are compatible with them. You can see a list of different WiFi standards that support each other.

If you see 'Yes' in that chart, the technologies in the row and column are backward compatible. On the other hand, if you see 'No' in the chart, it tells you the standards listed in rows and columns are not backward compatible.

WiFi Standard	IEEE802.11a	IEEE802.11b	IEEE802.11g	IEEE802.11n	IEEE802.11ac
11a	Yes	No	No	Yes	Yes
11b	No	Yes	Yes	Yes	No
11g	No	Yes	Yes	Yes	No
11n	Yes	Yes	Yes	Yes	Yes
11ac	Yes	No	No	Yes	Yes

You must be wondering why different wireless standards cannot connect. The frequency mode supported is the primary reason for the incompatibility between different IEEE 802.11 technologies.

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Let us check the frequencies supported by IEEE 802.11 WiFi connections.

1. IEEE 802.11 a ---5 GHz

2. IEEE 802.11 b ---2.4 GHz

3. IEEE 802.11 g ---2.4 GHz

4. IEEE 802.11 n -- Supports both 2.4GHz and 5GHz

5. IEEE 802.11 ac -- Supports 5GHz

1. https://www.keralapsc.gov.in/sites/default/files/2021-02/syllubus.pdf
2. https://standards.ieee.org/beyond-standards/the-evolution-of-wi-fi-technology-and-standards/