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Tone generation in OFDM transmitter

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Usman Hai

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Hi,
I wanted to generate tone in an already built OFDM transmitter model. I want to send one tone of like 3Ghz and receive it on receiver. The problem is i am not very much familiar with OFDM transmission and secondly I think Pilot tones before IFFT make more tones than expected in baseband.
My question is can I send one tone in OFDM tranmitter? I am using ADS model for this and bad thing i have no documentation of that OFDM tranceiver.
Regards,
/Noman
 

OFDM is a multicarrier signal and looks like a “bunch” of narrowband sub-carriers (e.g. in 802.11a are 52) transmitted in parallel at different frequencies. In 802.11a they are spaced 312.5 kHz apart from the same source. The four Pilots are modulated BPSK and he other 48 are modulated with BPSK, QPSK, 16QAM or 64QAM, depend by the speed of data.
 

Do u mean I cant generate single tone instead of real OFDM signal?
 

You can generate only a tone having one of the modulations listed above, but this will be not an OFDM signal.
In OFDM is not necessarily to be active all the carriers, but using only one active would be un-relevant test.
You can use only one carrier to find the P1dB of the amplifier, which can give you an idea of the linear dynamic range of the circuit.
 

Yes it is possible to generate one tone.. but this kills the beauty of OFDM that is multi-tone(carrier) system..
BUT YES IT IS POSSIBLE
 

In an realistic OFDM transmitter, put signal at one subcarrier and zero at others, then you would have the legal 'single tone' OFDM symbol.
 

If the OFDM transmit modle also contain the block encoding it is hard to identify an excact bit sequence which activate only one carrier. And because of the constallation for BPSK->64QAM there is no code which set one of the subcarrier to zero.

So no way!
 

in ofdm there is 48 data subcarriers, 4 pilots. if we use from 64-IFFT, subcarriers -21,-7,+7,+21 for pilots, 0 for DC cancellesion & (-32,-27)&(+27,32) null subcarrier for elimination high frequncy effects & other subcarrriers data. 48+4+12=64 or (-32,+32). :idea::D
 

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