Hi all,
802.11g provides the different data rate of 1,2,6,9,12,18,24,36,48 and 54 Mbps. Each of the different data rate has a different data modulation scheme in physical layer.
My question is that, is there any way to figure our the possible size of the transmitted data packets after modulation. For example, if I generate a UDP packet of size 1250 bytes and try to transfer it at these different data rates, what should be the approximately possible packet size after modulation or while transmitting.
If there is any reference is provided then that also would be much helpful.
Thanks in advance.
LG,
Chandra
Please refer to this study:
http://www4.ncsu.edu/~mlsichit/Research/Publications/tmt_nca03.pdf
Hope it helps to answer your question.
Dear Chandra,
If you deliver UDP packet of size N=1250 byets to the physical layer,there will be overhead which is added to the input data. If there is forward error correction, parity bits will be added to the input data according to used FEC encoder. The output rate of the FEC encoder will be Nx the code rate, where the code rate r fec = n/k is the ratio of the length of the output message to the the length of the input message.
During modulation you add the pilot carriers with specific date modulated upon them for channel estimation. These are overhead data with the rate say r pilot. In addition a cyclic prefix must be added to every OFDM symbol with the rate r cyclic prefix to overcome inter symbol interference..
These rates are standardized and are known. So the final size of the packet at the output of the physical layer= N(1 + r fec + r pilot + r cyclic prefix.)
It is so that every network layer adds overhead to the the protocol data unit such that it can perform its function and for encapsulation.
You can find more information in the LINK:http://research.ijcaonline.org/volume64/number8/pxc3885415.pdf
and the link: www.cnrood.com/public/.../WiFi_Physical_Layer_and_Transm_Meas.pd...
Best wishes
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