This paper presents a novel digital feedforward carrier recovery algorithm for arbitrary -ary quadrature amplitude modulation ( -QAM) constellations in an intradyne coherent optical receiver. The approach does not contain any feedback loop and is therefore highly tolerant against laser phase noise. This is crucial, especially for higher order QAM constellations, which inherently have a smaller ...

This paper investigates the construction of 8-QAM+ perfect arrays with at least an odd integer in their sizes, and gives the sufficient condition producing distinct 8-QAM+ perfect arrays. For different choices of odd integers in a given size of at least an odd integer, the resultant distinct 8-QAM+perfect arrays have their own sizes. For each choice, the number of the resultant distinct 8-QAM+p...

OFDM is a powerful multicarrier transmission technique used extensively for wireless applications. High PAPR is one of the deleterious problems of OFDM. This paper reviews basic OFDM system and PAPR problem associated with it. Also, the construction of M-QAM particularly 16-QAM sequences using QPSK Golay sequences over 4  is conferred. It is elucidated that a 16-QAM constellation can be writte...

We experimentally demonstrate a reconfigurable optical converter/encoder for quadrature amplitude modulated (QAM) signals. The system utilizes nonlinear wavelength multicasting, conversion-dispersion delays, and simultaneous nonlinear multiplexing and sampling. We show baud rate tunability (31 and 20 Gbaud) and reconfigurable conversions from lower-order QAM signals to higher-order QAM signals ...

A mutual information inspired nonbinary coded modulation design with non-uniform shaping is proposed. Instead of traditional power of two signal constellation sizes, we design 5-QAM, 7-QAM and 9-QAM constellations, which can be used in adaptive optical networks. The non-uniform shaping and LDPC code rate are jointly considered in the design, which results in a better performance scheme for the ...

In this paper, we propose a new selected mapping (SLM) scheme for reducing peak to average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signals modulated with quadrature amplitude modulation (QAM), called amplitude and phase variant SLM (APSLM). Contrary to the conventional SLM which rotates the phases of QAM symbols in the frequency domain, the proposed scheme change...

By using an approach other than usual, we derive an exact closed-form expression for the symbol error probability (SEP) for arbitrary rectangular M-QAM signaling over flat Rayleigh fading channels. This has never been achieved before as the best-known SER for QAM up to date is only the results obtained for the square M-QAM. Our rectangular M-QAM result can be readily extended to find the result...

This paper addresses automatic modulation classification for PSK and QAM signals under coherent and noncoherent conditions. In particular, the paper extends previous results by treating the classification of higher-state QAM signals. A maximum-likelihood algorithm is presented for coherent classification of PSK and QAM signals. We evaluate the algorithms performance for various PSK and QAM modu...

For low-rate trellis codes that do not utilize uncoded bits, a new approach to constellation labeling which maximizes the constellation edge proole can provide improved metrics. We investigate the edge proole optimality for 8-QAM and 32-QAM constellations. The labeling structures that achieve the optimal edge prooles for 8-QAM and 32-QAM are presented. Explicit proofs of the optimal edge proole...