RF Technology OFDM for 802.11g ?

[John]

Hi

I am confused why in the book it states that the RF technology for 802.11g is DSSS and OFDM and that the modulation for 802.11g is DBPSK and DQPSK. I know it is backward compatible to an extent so it would use DBPSK and DQPSK but OFDM is still a modulation technique even though it is called Orthogonal frequency-division multiplexing.

So OFDM is a modulation technique used by 802.11g to reach the higher data rates so why does it state that the only modulation is DBPSK and DQPSK ?


Regards
John

[eehinesee]

I'm not sure whether the errata sheets addressed this particular error (I assume the book to which you're referring is Carroll's official exam guide), but the sheets are quite extensive. See https://learningnetwork.cisco.com/message/53891#53891 for the URLs for the errata sheets.

I think he had phase shift keying confused with modulation.


Eric Hines

[John]

Thanks Eric.

I downloaded those yesterday but i never saw anything on that part. I read this book twice last year, this time i am double checking everything, slow process but i learn a bit more each time i do it.


Regards
John

[eehinesee]

Count yourself lucky for having accumulated some actual experience. I'm switching from systems/test engineering to networking, so my CCNA is a purely paper cert--and I wound up reading the books 5 times before I felt like I had a chance at the exam.


Eric Hines

[John]

Hi Eric

My wireless experience is mobile phone wireless, similar concept to 802.11 but different equipment and different rules/protocols.

I am studying Cisco wireless because it is what interests me most but if i get into this game as a profession it will be either because my company moves that way which i don't think they will or i start my own company one day. The latter is a possible end game, i have started my own business a few times over the past 28 years with various things.

This is why i am also studying R&S as it is now becoming part of my profession as the mobile phone business is moving to full ethernet and routers and switchs are now hanging off almost everything rather than using IP over ATM.

I aim to pass CCNA Wireless then do CCNP R&S, during this i will study CCNP wireless as well but concentrate on R&S mostly and just hope something comes from the wireless side of things.

What do you do in systems/test engineering ?


Regards
John

[eehinesee]

John,

What I did do (I got fed up with my company's management and took my pension and walked out the door--right before the current economic unpleasantness--wonderful timing) was work for a defense contractor building aircraft simulators--mostly fighter simulators. My specific role was requirements analysis (both the real requirements and those the customer thought he was asking for), writing test procedures to assess whether those requiremetns were being satisfied, and then executing those procedures on delivery (and, of course, at the various stages of development). I got to play some really fantastic video games--sitting inside a sphere of visualization centered on the cockpit, for instance; the F-16 game for your PC really is quite, umm, simplistic. But after awhile, no matter the breadth of simulators, it becomes variations on a theme, and I got bored (which lowered my threshold for getting fed up with management).

You at least come to CCNA wireless being able to spell radio and networking. I have a facility for analysis, but everything else is new. And interesting.


Eric Hines

[John]

Hi Eric

You must do what you think is right mate and you can changes jobs and still end up on top.

When left the army in 1999 i got a job in Holand designing 2g microwave then 3g microwave in Sweden, i studied every day and learnt as fast as i could. I got bored with that and i could see it was getting too easy with software doing most of the work.

I then moved onto working on the main servers that control mobile phone networks, again i studied every night for 3 years and became good at it. Most people did not know anything about the 1,000 plus parameters and avoided it, i studied it and became good at it.

I then spent a few thousand on optimisation courses and studied that and ended up doing that as well. I am now on 3g and RU10 mobile phone networks and as it is almost full IP over ethernet i am now studying Cisco R&S and wireless.

It is a lot of work but i know if you study hard enough you can do anything and be good at it.

From what i can see happening in this communications game the past 10 years, 802.11 wireless will grow very fast but their won't be enough engineers
to do the job. That means there will be plenty of jobs for those that know it and high salaries for quite some time. I saw that happen in Microsoft in the 90's and in my game the past 10 years.


Best of luck Eric.
Regards
John