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Orthogonal modulation, for example, frequency-shift keying (FSK) or pulse-position modulation (PPM), is primarily used in relatively-low-rate communication systems that operate in the power-limited regime. Optimal noncoherent detection of orthogonally modulated signals takes the form of sequence detection and has exponential (in the sequence length) complexity when implemented through an exhaustive search among all possible sequences. In this work, for the first time in the literature, we present an algorithm that performs generalized-likelihood-ratio-test (GLRT) optimal noncoherent sequence detection of orthogonally modulated signals in flat fading with log-linear (in the sequence length) complexity. Moreover, for Rayleigh fading channels, the proposed algorithm is equivalent to the maximum-likelihood (ML) noncoherent sequence detector. Simulation studies indicate that the optimal noncoherent FSK detector attains coherent-detection performance when the sequence length is on the order of 100, offering a 3–5 dB gain over the typical energy (single-symbol) detector. While the conventional exhaustive-search approach becomes infeasible for such sequence lengths, the proposed implementation requires a log-linear only number of operations, opening new avenues for practical deployments. Finally, we show that our algorithm also solves efficiently the optimal noncoherent sequence detection problem in contemporary radio frequency identification (RFID) systems. [ABSTRACT FROM AUTHOR]

In this letter, we have analyzed the Internet protocol transmission and routing over frequency-shift keying optical code division multiple access based on a novel optical code.This code enhances the system bit error rate, packet error rate, number of simultaneous subscribers, and security, as compared to the other prime codes. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2852-2856, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27213 [ABSTRACT FROM AUTHOR]

With the rapid growth of frequency-hopped (FH) wireless networks, interference due to frequency collisions has become one of the main performance-limiting challenges. This paper proposes a novel multiuser detection method for joint hop timing and frequency estimation, which is capable of unraveling and demodulating multiple FH transmissions in the presence of collisions and unknown hop patterns without retransmission. The method is based on the principle of dynamic programming (DP) coupled with two-dimensional harmonic retrieval (2-D HR) or low-rank trilinear decomposition, and it remains operational even with multiple unknown hop rates, frequency offsets, and asynchronism. The model is based on frequency-shift keying (FSK) and phase-shift keying (PSK) modulation, but the algorithms are also evaluated with Gaussian minimum-shift keying (GMSK) modulation and shown to be robust. [ABSTRACT FROM PUBLISHER]

A very simple design rule for parallel concatenated Turbo codes over GF(q) with q-ary orthogonal modulation is proposed. Unlike previously proposed exhaustive search methods, the proposed design rule allows straightforward and systematic code designs for any value of q ≥ 2 and any constraint length greater than 2. [ABSTRACT FROM PUBLISHER]