Asymptotic spectral behavior of spectrally precoded OFDM signal with arbitrary input statistics

In this letter, we study the asymptotic spectral behavior of the spectrally precoded orthogonal frequency-division multiplexing (SP-OFDM) signal with arbitrary input statistics. It is shown that all constraints and spectral precoders previously developed for SP-OFDM with independent and identically distributed and zero-mean data provide fast decaying spectral sidelobes for SP-OFDM with arbitrary input statistics.     

Differentially amplitude and phase-encoded QAM for the correlatedRayleigh-fading channel with diversity reception

This paper studies the differentially amplitude and phase-encoded (DAPE) quadrature amplitude modulation (QAM) transmission over correlated Rayleigh channels with diversity reception. Operating over two successive received symbols, the optimum and an asymptotic maximum-likelihood (AML) differentially coherent receiver are developed and compared with a conventional switched diversity combining (SDC) grid receiver. It is shown that the AML and SDC grid receivers are much simpler in complexity than the optimum receiver in that no channel side information is required in their realization. An exact expression of the bit-error probability (BEP) is obtained for the SDC grid receiver. Based on a union bound argument, a BEP upper bound for the AML receiver is also derived and verified by simulation. Numerical results on 16- and 64-point constellations show that the AML receiver exhibits an almost optimum performance and the SDC grid receiver with a small level of diversity is nearly optimum. It is also shown by simulation that the conventional equal-gain diversity receiver is almost optimal for demodulating a 16-point DAPE QAM signal     

Diversity codes for differential phase modulation in a correlatedRayleigh fading channel

This paper proposes a simple diversity scheme that makes use of nonlinear block coding, symbol interleaving, and differential phase modulation. The resultant signaling mechanism merits intrinsic time diversity within each codeword, which is resistant to correlated fading. The maximum-likelihood noncoherent receiver which operates over correlated Rayleigh fading is developed. Exact and approximate upper bounds are derived to assess the codeword-error probability characteristics of the proposed system     

Spectral precoding for rectangularly pulsed OFDM

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.     

Suboptimum coherent detection of orthogonal phase-modulated signals

A suboptimum scheme for coherent demodulation of orthogonal phase-modulated signals in the additive white Gaussian noise channel is proposed and analyzed in terms of bit error probability. It is analytically shown that the suboptimum scheme provides the bit error performance competitive to the conventional optimum scheme, while requiring much less implementation complexity.     

Coherent frequency/phase modulation scheme

An L-phase-levelled coherent frequency/phase modulation (LCFPM) scheme is proposed and analysed for additive white Gaussian noise channels. The optimised LCFPM scheme with L>2 is found to have superior bandwidth efficiency to the conventional dual-frequency quadrature frequency/phase modulation scheme     

Noncoherent block detection in the presence of DC offset

In this paper, we deal with noncoherent detection of a digitally phasor block-modulated signal in the additive white Gaussian noise channel when a direct-current (DC) offset is present in the receiver baseband processing. By processing the received baseband signal block by block, a generalized linear transform is used to remove the offset prior to data detection, thereby releasing the succeeding detection process from the threat of DC offset. Operating on transform output blocks, a generalized maximum-likelihood scheme is developed for noncoherent data detection without a priori knowledge of channel amplitude and phase. When all the signaling blocks are confined within the space expanded by the basis vectors obtained from the onset-removal transform matrix, the proposed detection scheme can exploit the advantage of performing data detection and estimation on channel amplitude and phase jointly in the maximum-likelihood sense. It is analytically shown that the block detection scheme provides the bit error performance asymptotically approaching that of the corresponding ideal coherent phase-shift-keyed (PSK) detection in the absence of DC offset when the block length is increased. An iterative detection scheme is also modified from the block detection scheme to simplify the realization complexity. Both block and iterative detection schemes are shown to outperform the conventional training-sequence-aided PSK detection scheme under the same transmission throughput efficiency.     

Orthogonally multiplexed orthogonal amplitude modulation family

A family of coherent orthogonally multiplexed orthogonally amplitude-modulated (OMOAM) signals is presented. The OMOAM signal is constituted by orthogonally multiplexing AI component signals, each constructed by a data-chosen group of L orthogonal pulse-amplitude-modulated basis signals. A generalized signal format is proposed to model the OMOAM signal in a unified way that the family contains not only classical orthogonally multiplexed modulations as special embodiments, but also a multitude of new modulations. A generalized optimum receiver for coherently demodulating OMOAM signals is developed and analyzed in terms of the bit error probability for the additive white Gaussian noise channel. The spectral characteristics of the OMOAM signals constructed from various time-limited and band-limited basis sets are studied in terms or the fractional out-of-band power containment. Several general trends of error and spectral performance characteristics are exploited     

Adaptive differentially coherent orthogonally multiplexed orthogonal phase modulation over flat fading channels

A constant-power adaptive transmission technique adopting differentially coherent orthogonally multiplexed orthogonal phase modulation (DOMOPM) signals is studied for flat fading channels. Numerical results show that the constant-power adaptive DOMOPM system significantly outperforms the constant-power adaptive noncoherent frequency shift keying system in average spectral efficiency.     

Noncoherent detection of preamble-signal-assisted differentiallyphase-encoded APSK signals

A noncoherent detection scheme for differentially encoded amplitude- and phase-shift-keyed data transmission, assisted with differentially phase-shift-keyed preamble signals, is presented and analyzed for an additive white Gaussian noise channel. It is analytically shown that, despite a controllable reduction in bandwidth efficiency, the proposed scheme yields an error performance approaching that of the quadrature amplitude modulation scheme with ideal coherent detection within a loss of approximately 1 dB