SS-OFDM: A low complexity method to improve spectral efficiency

Filtered orthogonal frequency division multiplexing (F-OFDM) system has a high computational complexity due to its high-order filter. In this paper, a subband superposed OFDM (SS-OFDM) scheme, utilizing a multistage polyphase subfiltering structure, is proposed to reduce the complexity. In the SS-OFDM system, the entire transmission channel is divided into several subbands and each subband employs relatively low order filtering to depress its out-of-band emission (OOBE). Moreover, all the subbands implement parallel transmission in time domain, which decreases the operating rate, meanwhile shortening the filter length. Simulation results show that the spectral efficiency (with respect to spectrum occupancy ratio) is increased up to about 99% for the LTE, DTMB, and DVB-T standards, while preserving a low implementation complexity.

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