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Quiz on IEEE 802.11a specifications

by Krishna Sankar on October 7, 2009

The IEEE 802.11a specifications are used by many to understand a wireless communication link built using OFDM. In this post, I have put together a set of 10 multiple choice questions based on 802.11a specifications. The questions are on the building blocks in 802.11a specifications, preamble structure and so on. Upon completion of the quiz, you will be lead to a page showing the correct answers and their explanations.

Click here to download IEEE 802.11a specifications.

Note: The quiz might not be visible on RSS reader or over email. Please visit the site to access the quiz.

Good luck!

The spacing between subcarriers in 802.11a specifications is






The duration of an OFDM symbol in 802.11a specification is






The coding scheme used in 802.11a specifications is






The number of used subcarriers in 802.11a specification is






The modulation used in SIGNAL field in 802.11a specification is






The acronym CCA in 802.11a specification stands for





The number of short preambles used in 802.11a specification is






The duration of the long preamble in 802.11a specification is






The number of TAIL bits in 802.11a specification is






The transmitter center frequency tolerance in 802.11a specification is








Tagged as: 802.11a, OFDM

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{ 8 comments… read them below or add one }

1 Sudeep October 7, 2009 at 9:10 am

Regarding the question on symbol duration, the checkbox answer shows it as 3.2 us, where as in the explanation it is mentioned as 4 us including the GI. I think the check box should also show 4 us as the correct option to avoid confusion.

Reply

2 Krishna Sankar October 8, 2009 at 5:36 am

@Sudeep: Thanks for noticing it. I corrected.

Reply

3 Sudeep October 12, 2009 at 8:11 am

Regarding frequency offset tolerance, does it mean for 802.11g, this figure needs to be only around 100 KHz ~(2.4*40)? Or does the tolerance become +/- 40ppm in that case?

Reply

4 Krishna Sankar October 13, 2009 at 4:58 am

@Sudeep: For the 802.11g (ERP-PHY, see clause 19.4.7.2 in IEEE 802.11-2007 specifications), the tolerance specified is +/-25ppm. So the maximum frequency offset comes around to 2.5GHz * 50ppm = 125kHz.

Reply

5 preet July 31, 2010 at 10:11 pm

can you sujjest any method for solving sunchronization problem in ofdm,,,,,

Reply

6 Krishna Sankar August 2, 2010 at 5:52 am

@preet: Synchronization is quite an involved issue. Need to fidn algorithms for frequency/phase and time synchronization. Have brief post on frequency offset estimation in OFDM
http://www.dsplog.com/2008/03/03/frequency-offset-estimation-using-80211a-short-preamble/

Reply

7 preet August 4, 2010 at 11:22 am

please tell how to calculate all the parameters of IEEE 802.11a specification,

Reply

8 Krishna Sankar August 10, 2010 at 4:55 am

@preet: Plz use the IEEE specifications @ http://standards.ieee.org/getieee802/download/802.11a-1999.pdf

Reply

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