Practical designs for out-of-band emission suppression and adjacent channel interference rejection for orthogonal frequency division multiplexing-based cognitive radios

Opposite to the conventional wisdom, practical considerations for out-of-band emission (OOBE) suppression and adjacent channel interference (ACI) rejection in orthogonal frequency division multiplexing (OFDM) -based cognitive radio systems are not completely alike. For example, ACI will increase after discarding the cyclic prefix (CP) because the interference signal is also truncated during the CP removal process. Furthermore, effective OOBE is much larger than the estimated OOBE if there is a timing offset (TO) between the primary and secondary users. To the best of our knowledge, these and some other practical issues have not been well addressed. Various important practical issues (including multipath delay spread, high peak-to-average power ratio (PAPR), spectral efficiency loss, high complexity, sensitivities to frequency and timing offsets, non-contiguous and dynamically changing spectrum, CP removal, spectral containment, etc.) concerning OOBE suppression and ACI rejection are studied in this paper. Numerical results show that none of the existing approaches can deal with all practical issues satisfactorily. Hybrid combinations of frequency-domain approaches (spectral precoding and PAPR precoding) and time-domain approaches (windowing and filtering) are developed to maintain the merits and mitigate the drawbacks of each constituent approach in order to deal with these practical challenges. It is shown that a combination of filtering and precoding provides the best OOBE suppression and a combination of windowing and precoding provides the best ACI rejection characteristics in our numerical examples.

[1]  Henrique S. Malvar,et al.  Signal processing with lapped transforms , 1992 .

[2]  I-Tai Lu,et al.  Resource Block Based Precoding Schemes for Suppressing Out-of-Band Emission , 2013, MILCOM 2013 - 2013 IEEE Military Communications Conference.

[3]  Michael Schnell,et al.  Subcarrier weighting: a method for sidelobe suppression in OFDM systems , 2006, IEEE Communications Letters.

[4]  Dominique Noguet,et al.  Advances in opportunistic radio technologies for TVWS , 2011, EURASIP J. Wirel. Commun. Netw..

[5]  Jaap van de Beek.  Orthogonal Multiplexing in a Subspace of Frequency Well-Localized Signals , 2010, IEEE Communications Letters.

[6]  Sai Shankar Nandagopalan,et al.  IEEE 802.22: An Introduction to the First Wireless Standard based on Cognitive Radios , 2006, J. Commun..

[7]  Imran Baig,et al.  PAPR Reduction in OFDM Systems: Zadoff-Chu Matrix Transform Based Pre/Post-Coding Techniques , 2010, 2010 2nd International Conference on Computational Intelligence, Communication Systems and Networks.

[8]  I-Tai Lu,et al.  Precoder designs for jointly suppressing out-of-band emission and peak-to-average power ratio in an orthogonal frequency division multiplexing system , 2014, IET Commun..

[9]  Jaap van de Beek.  Sculpting the multicarrier spectrum: a novel projection precoder , 2009, IEEE Communications Letters.

[10]  Char-Dir Chung,et al.  Spectrally Precoded OFDM , 2006, IEEE Transactions on Communications.

[11]  Roger Pierre Fabris Hoefel,et al.  A MAC and PHY Cross-Layer Analytical Model for the Goodput and Delay of IEEE 802.11a Networks Operating Under Basic Access and RTS/CTS DCF Schemes , 2006, J. Commun..

[12]  Piotr Cholda,et al.  Reliability, survivability, and quality of large scale telecommunications systems [Book Review] , 2004, IEEE Communications Magazine.

[13]  Friedrich Jondral,et al.  Spectrum pooling: an innovative strategy for the enhancement of spectrum efficiency , 2004, IEEE Communications Magazine.

[14]  D.J. Goodman,et al.  Single carrier FDMA for uplink wireless transmission , 2006, IEEE Vehicular Technology Magazine.

[15]  Yiyan Wu,et al.  Orthogonal Frequency Division Multiplexing: A Multi-Carrier Modulation Scheme , 1995, Proceedings of International Conference on Consumer Electronics.

[16]  Jun Wang,et al.  Sidelobe suppression for OFDM based cognitive radio systems , 2009, 2009 Fourth International Conference on Communications and Networking in China.

[17]  Siavash M. Alamouti,et al.  A simple transmit diversity technique for wireless communications , 1998, IEEE J. Sel. Areas Commun..

[18]  J. Zhang,et al.  PAPR Reduction in OFDM Systems: Zadoff-Chu Matrix Transform Based Pre/Post-Coding Techniques , 2010, 2010 2nd International Conference on Computational Intelligence, Communication Systems and Networks.

[19]  Rui Yang,et al.  Shaping Spectral Leakage: A Novel Low-Complexity Transceiver Architecture for Cognitive Radio , 2013, IEEE Vehicular Technology Magazine.

[20]  Neeli R. Prasad,et al.  Spectrum Aggregation with Multi-band User Allocation over Two Frequency Bands , 2009, 2009 IEEE Mobile WiMAX Symposium.

[21]  Hüseyin Arslan,et al.  Edge Windowing for OFDM Based Systems , 2011, IEEE Communications Letters.

[22]  Joseph Mitola,et al.  Cognitive radio: making software radios more personal , 1999, IEEE Wirel. Commun..

[23]  M. Schnell,et al.  Sidelobe suppression in OFDM systems by insertion of cancellation carriers , 2005, VTC-2005-Fall. 2005 IEEE 62nd Vehicular Technology Conference, 2005..

[24]  Rui Yang,et al.  Resource block Filtered-OFDM for future spectrally agile and power efficient systems , 2014, Phys. Commun..

[25]  Slimane Ben Slimane,et al.  Reducing the Peak-to-Average Power Ratio of OFDM Signals Through Precoding , 2007, IEEE Transactions on Vehicular Technology.