Pairwise subcarriers weighting for suppressing out‐of‐band radiation of OFDM

Abstract

SUMMARYThis paper proposes a subcarrier weighting technique to suppress the out-of-band radiation of OFDM signals. By mapping and weighting the same data on an adjacent pair of subcarriers, the spectrum sidelobes are suppressed perfectly through sidelobes mutual cancellation. The optimum weighting factor is derived based on a rectangular pulse-shaped OFDM spectrum model. Compared with existing out-of-band suppression schemes, the proposed scheme not only requires less computational burden but also achieves better spectral roll-off. For example, when the cyclic prefix of a one-eighth OFDM-block length is added, the proposed scheme suppresses the 10-dB radiation at the center frequency between two subbands which are using cognitive radio. Analytical and simulation results also show that the proposed scheme improves the system carrier-to-interference ratio by 10 dB at a normalized frequency offset above 0.1, which leads to the performance improvement in terms of the BER on AWGN channel and multipath fading channel. Copyright

Joint carrier frequency offset and channel estimation for OFDM systems with two receive antennas

“…In the ideal case where the CFO is zero, the matrix E(ϕ) will be an identity matrix and hence (7) reduces to (8) and the subcarriers are obviously orthogonal easing the equalization and detection process. In practice, there will always be a certain amount of CFO.…”

“…Because of its interesting features, OFDM has received considerable interest and has been investigated extensively by researchers in its various aspects [1][2][3][4][5][6][7][8]. For an OFDM system, a frequency selective fading channel will appear as a large number of flat fading channels, thus significantly easing its equalization process.…”

Extended Subcarrier Weighting for Sidelobe Suppression in OFDM Based Cognitive Radio

“…A pairwise subcarrier weighting is presented in [18] by mapping a data symbol over adjacent subcarriers. It provides a low complexity solution to sidelobe suppression however throughput is reduced to half as compared to C-SW. Issues regarding complexity are also addressed in [19] where computation requirements are reduced by trading-off with sidelobe suppression capacity.…”

Efficient branch and bound algorithms for prototype filter optimization in OQAM‐OFDM systems

“…However, the OFDM system suffers from a few drawbacks, one of which is the high out-of-band radiation caused by the rectangular pulse shaping [1]. However, the OFDM system suffers from a few drawbacks, one of which is the high out-of-band radiation caused by the rectangular pulse shaping [1].…”