Spectral precoding for rectangularly pulsed OFDM

Abstract

Spectrally precoded orthogonal frequency-division multiplexing (OFDM) is a promising rectangularly pulsed OFDM signaling format which can provide very small power spectral sidelobes, while allowing for efficient implementation by fast Fourier transform and guard interval insertion. In this paper, general constraints on spectral precoding are developed for OFDM signals with zero padding (ZP-OFDM) or cyclic prefix (CP-OFDM) to warrant the desirable spectral property that the power spectral sidelobes decay asymptotically as f −2K−2 , where K is a preassigned positive integer. In accordance with the constraints, block partitioning is adopted to construct a general signaling format to facilitate the precoder design of the spectrally precoded CP-OFDM that can provide fast decaying sidelobes. New correlative and orthogonal precoders are also devised so that the desirable spectral property of fast sidelobe decaying is achieved with spectrally precoded ZP-OFDM and CP-OFDM signals.

Multiuser Spectral Precoding for OFDM-Based Cognitive Radio Systems

“…Spectral compactness is enhanced with low complexity and bandwidth efficiency is potentially improved with no or narrower guard bands. Unlike the existing spectral precoding schemes [18]- [20], it is always possible for CR users to utilize small spectrum segments consisting of only a few subcarriers without introducing BER performance loss.…”

“…Spectral precoding approaches [18]- [20] can reduce OOB radiation significantly and are applicable to multiple users. The precoding matrix for these approaches is constructed from delicately designed basis sets [18] or determined to render time continuity of adjacent OFDM symbols or spectrum nulls at notched frequencies [19], [20].…”

“…The precoding matrix for these approaches is constructed from delicately designed basis sets [18] or determined to render time continuity of adjacent OFDM symbols or spectrum nulls at notched frequencies [19], [20]. With a block diagonal precoding matrix, it is possible to ensure user independence.…”

“…With a block diagonal precoding matrix, it is possible to ensure user independence. However, the correlative precoder in [18], the projection precoder in [19], and the 1-continuous OFDM precoder in [20] are non-orthogonal and will cause significant bit-error rate (BER) performance degradation when only a few subcarriers are available and utilized by CR users. Spectral precoding dealing with the above challenges in the multiuser CR system needs to be investigated.…”

Suppressing the out-of-band power radiation in multi-carrier systems: A comparative study

“…The price to pay for both methods is an increased peak-to-average power ratio (PAPR) as well as a decreased average signal-to-noiseplus-interference ratio (SINR), resulting in a degraded bit-error rate (BER) performance. e) Spectral precoding: To avoid recalculating weights on a per-(OFDM)-symbol basis, a data-independent approach has firstly been proposed in [16], where the block of transmit symbols x k is transformed by a precoding matrix G prior to OFDM modulation as:x…”