OFDM Transmitter: Difference between revisions
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| Line 7: | Line 7: | ||
; FFT Length | ; FFT Length | ||
: The | : The number of sub-carriers. | ||
; Cyclic Prefix Length | ; Cyclic Prefix Length | ||
: The length of | : The maximum possible length of multi-paths in their time dispersion | ||
; Packet Length Tag Key | ; Packet Length Tag Key | ||
| Line 25: | Line 25: | ||
; Sync Word 1 | ; Sync Word 1 | ||
: The first sync preamble symbol. This has to be with zeros on alternating carriers. Used for fine and coarse frequency offset and timing estimation. | : The first sync preamble symbol. This has to be with zeros on alternating carriers (0., 1.536, 0., -1.536, 0., ...). Used for fine and coarse frequency offset and timing estimation. Length of sync sequence must be the same as the value of FFT length. | ||
; Sync Word 2 | ; Sync Word 2 | ||
: The second sync preamble symbol. This has to be filled entirely. Also used for coarse frequency offset and channel estimation. | : The second sync preamble symbol. This has to be filled entirely. Also used for coarse frequency offset and channel estimation. Length of sync sequence must be the same as the value of FFT length. | ||
; Header Modulation | ; Header Modulation | ||
: | :* BPSK | ||
:* QPSK | |||
; Payload Modulation | ; Payload Modulation | ||
: | :* BPSK | ||
:* QPSK | |||
:* 8-PSK | |||
; Rolloff length (samples) | ; Rolloff length (samples) | ||
Revision as of 05:51, 18 February 2022
Hierarchical block for OFDM modulation.
The input is a byte stream (unsigned char) and the output is the complex modulated signal at baseband.
Parameters
- FFT Length
- The number of sub-carriers.
- Cyclic Prefix Length
- The maximum possible length of multi-paths in their time dispersion
- Packet Length Tag Key
- The name of the tag giving packet length at the input.
- Occupied Carriers
- A vector of vectors describing which OFDM carriers are occupied.
- Pilot Carriers
- A vector of vectors describing which OFDM carriers are occupied with pilot symbols.
- Pilot Symbols
- The pilot symbols.
- Sync Word 1
- The first sync preamble symbol. This has to be with zeros on alternating carriers (0., 1.536, 0., -1.536, 0., ...). Used for fine and coarse frequency offset and timing estimation. Length of sync sequence must be the same as the value of FFT length.
- Sync Word 2
- The second sync preamble symbol. This has to be filled entirely. Also used for coarse frequency offset and channel estimation. Length of sync sequence must be the same as the value of FFT length.
- Header Modulation
-
- BPSK
- QPSK
- Payload Modulation
-
- BPSK
- QPSK
- 8-PSK
- Rolloff length (samples)
- The rolloff length in samples. Must be smaller than the CP.
- Scramble Bits
- Activates the scramblers (set this to True unless debugging)
- Log Debug Info
- Write output into log files (Warning: creates lots of data!)
Example Flowgraph
This flowgraph can be found at https://github.com/gnuradio/gnuradio/blob/master/gr-digital/examples/ofdm/ofdm_loopback.grc
Source Files
- Python files
- [1]
- Block definition
- [2]