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Hi,
The maximum allowable bandwidth for transmission is 19Mhz. For my spectrum sense application , I need to restrict the Tx data to a lower bandwidth such that data in one channel does not overlap with other channels frequency. Can I reduce the Tx bandwidth to around 8-10Mhz ? How can it be done ?
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The RF bandwidth is approx. 40MHz (19MHz is the corner frequency of the Tx LPF). You can transmit signals of any bandwidth up to 40MHz by constructing the bandlimited signals digitally. If you work through the WARPLab exercises (especially the comm example) from the workshop, you'll see they use exactly this approach.
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Hi,
I want to reduce my transmission bandwidth from 20MHz to 5MHz when using the ofdm video streaming example.
Do I need to switch off some data carriers in ofdm in the warpphy_set_modulation() function ?
What should I do ?
I also need to modify the LPF filter settings in MAX2829 chip, right ?
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The current reference design uses 10MHz bandwidth (40MHz sampling, 4x interpolation/decimation at the PHY front-end). You can disable subcarriers in code to reduce this. I strongly recommend trying this in simulation first. There are a number of parameters that need to be updated when changing the subcarrier mapping (like number of bytes per OFDM symbol, which affects how many OFDM symbols are required to send a given payload). If you find the right combination of parameters in simulation, it will be much easier mapping these into changes to the warpphy/warpmac C code.
Also, the preamble and training symbols are hard-coded in the Sysgen model and will span the full 64 subcarriers by default. You can change these at build-time (by modifying the PHY init script), but not run-time.
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Could you help me out with some material on training symbols and the concept of number of ofdm symbols per payload. I don't understand what these parameters depend upon.
How do I simulate the design ? which tool is to be used ?
Last edited by Rohan Surana (2009-Jun-22 01:15:29)
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The OFDM core is a System Generator model. It is built in Sysgen v10.1.03.
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Hi,
I searched the entire code (warpphy.c and warpmac.c) but could find how to change the number of bytes per odfm symbol. Please help.
To switch of sub-carriers its the only parameter that has to be changed apart from changing the modulation masks, right ?
Last edited by Rohan Surana (2009-Jun-24 02:15:56)
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