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New Member

Wireless Frequency Question

This may sound rather naive...however, in my pursuit to understand the PHY layer, if a Radio is transmitting at a frequency of 2.4GHz, then this means 2.4 billion sine waves per second. Hmmm...then how come you cannot place a bit on each sine wave and get 2.4Gbps???? All of the modulation techniques talk about placing as many bits as possibe on the freqencies so that is what brings me to this question.

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New Member

Re: Wireless Frequency Question

I have not seen any documentation explaining why this is not possible. What you are suggesting makes sense. If you find out any additional info, please share it with the forum. Here is a pretty good link that explains different types of modulation techniques.

http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/wireless.htm

Cisco Employee

Re: Wireless Frequency Question

You are confusing carrier wave frequency and modulation frequency.

You can not modulate a carrier wave with a signal of the same frequency as when you demodulate this signal you need to seperate the 2 signals

New Member

Re: Wireless Frequency Question

So, the modulation frequency is different than the carrier frequency? OK. I thought that to modulate was to "change" the carrier frequency in some way that allows the reciever to interpret this as data. Carrier frequencies are just "waves" and modulation is the act of manipulating these waves in order to encode data on them...this is how I drew the conclusion that if you manipulated a wave, which was coming out at 2.4Ghz., then you should be able to get much higher data rates???? Is this sound correct?

Cisco Employee

Re: Wireless Frequency Question

Hey this non Cisco site may help you

http://electronics.howstuffworks.com/radio.htm

"modulation is the act of manipulating these waves " yes but you use a signal to manipluate these waves and that can not be at the same frequency as the carrier.

Think of a AM radio

The carrier frequency is say 90Mhz

The modulation signal is voice aprox 0hz to 4khz

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