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Pruned DFT spread FBMC is a novel modulation scheme with the remarkable properties of a low PAPR, low latency transmissions and a high spectral efficiency. It is closely related to FBMC, OFDM and SC-FDMA, and I first proposed it in my PhD thesis, see Chapter 6. A more detailed description can be found in “Pruned DFT Spread FBMC: Low PAPR, Low Latency, High Spectral Efficiency”, IEEE Transactions on Communications, 2018. Note that pruned DFT spread FBMC can equivalently be interpreted as extremely windowed pruned DFT-s-OFDM.
- Matlab code: allows to reproduce all figures from my journal paper.
- Python code: limited features (but also less overhead).
Basic Properties of Pruned DFT Spread FBMC
Basic Properties of Pruned DFT Spread FBMC
Same PAPR as SC-FDMA:
Same PAPR as SC-FDMA:
The ramp-up and ramp-down period of FBMC is reduced, allowing low-latency transmissions:
The ramp-up and ramp-down period of FBMC is reduced, allowing low-latency transmissions:
Very low out-of-band emissions, comparable to FBMC:
Very low out-of-band emissions, comparable to FBMC:
Outperforms SC-FDMA in doubly-selective channels:
Outperforms SC-FDMA in doubly-selective channels:
Block Diagram of Pruned DFT Spread FBMC
Block Diagram of Pruned DFT Spread FBMC
Block diagram of pruned DFT spread FBMC at time position k. Compared to conventional FBMC-OQAM transmissions, the complex-to-real transformation is replaced by precoding with C_f, the real-to-complex transformation by C_f^H, and the protoype filter must be shorter than approximately 1.5/F, with F denoting the subcarrier spacing. Note that in conventional FBMC-OQAM, the data symbols x_k are real-valued.
Alternative Interpretation: Extremely Windowed Pruned DFT-s-OFDM
Alternative Interpretation: Extremely Windowed Pruned DFT-s-OFDM
Power of the underlying basis pulses over time for an FFT size of 512 and 16 subcarriers.
(a) Conventional OFDM.
(b) Conventional SC-FDMA, that is, OFDM + precoding by a DFT matrix.
(c) Only 8 basis pulses, close to the center, are utilized. Thus, the DFT matrix is replaced by a pruned DFT matrix.
(d) Multiplication by a window/prototype function p(t), so that OFDM transforms into FBMC.
(e) One-tap scaling of the basis pulses so that the transmit power is approximately constant over time.
References
References
- R. Nissel, "Filter Bank Multicarrier Modulation for Future Wireless Systems", Dissertation, TU Wien, 2017.
- R. Nissel, M. Rupp, "Pruned DFT Spread FBMC: Low PAPR, Low Latency, High Spectral Efficiency", accepted for publication in IEEE Transactions on Communications.
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