Near-Capacity Turbo Coded Soft-decision Aided DAPSK/Star-QAM

Low-complexity non-coherently detected Differential Amplitude and Phase-Shift Keying (DAPSK) schemes constitute an ideal candidate for wireless communications. In this paper, we derive the soft-output probability formulas required for the soft-decision based demodulation of DAPSK, which are then invoked for Turbo Coded (TC) transmissions. Furthermore, the achievable throughput characteristics of the family of M-ary DAPSK schemes are provided. It is shown that the proposed 4-ring based TC assisted 64-ary DAPSK scheme achieves a coding gain of about 4.2 dBs in comparison to the identical-throughput TC assisted 64-ary Differential Phase-Shift Keying (64-DPSK) scheme at a bit error ratio of 10?5

Code Design for Non-Coherent Detection of Frame Headers in Precoded Satellite Systems

In this paper we propose a simple method for generating short-length rate-compatible codes over $\mathbb{Z}_M$ that are robust to non-coherent detection for $M$-PSK constellations. First, a greedy algorithm is used to construct a family of rotationally invariant codes for a given constellation. Then, by properly modifying such codes we obtain codes that are robust to non-coherent detection. We briefly discuss the optimality of the constructed codes for special cases of BPSK and QPSK constellations. Our method provides an upper bound for the length of optimal codes with a given desired non-coherent distance. We also derive a simple asymptotic upper bound on the frame error rate (FER) of such codes and provide the simulation results for a selected set of proposed codes. Finally, we briefly discuss the problem of designing binary codes that are robust to non-coherent detection for QPSK constellation.Comment: 11 pages, 5 figure

M-ary Chirp Modulation for Data Transmission

M-ary chirp modulations, both discontinuous- and continuous-phase, for M-ary data transmission are proposed and examined for their error rate performances in additive, white, Gaussian noise (AWGN) channel. These chirp modulated signals are described and illustrated as a function of time and modulation parameters. M-ary chirp modula­ tion with discontinuous phase is first proposed and then the M-ary Continuous Phase Chirp Modulation (MCPCM) is considered. General descriptions of these modula­ tion systems are given and properties of signals representing these modulations are given and illustrated. Optimum algorithms for detection of these signals in AWGN are derived and structures of optimum receivers are identified. Using the minimum Euclidean distance criterion in signal-space; upper bounds on Signal-to-Noise Ratio (SNR) gain relative to Multiple Phase Shift Keying (MPSK) are established for 2-. *4-, and 8-ary MCPCM systems. It is observed that the maximum likelihood coherent and non-coherent receivers for MCPCM are non-linear and require multiple-symbol observations. Since symbol error probability performance analyses of these receivers are too complex to perform, union upper bounds on their performances are derived and illustrated as a function of SNR, number of observation symbols, and modulation parameters for MCPCM. Optimum 2-, 4-, and 8-ary modulation schemes that mini­ mize union upper bound on symbol error rates have been determined and illustrated. Our results show that 2-, 4-, and 8-ary optimum coherent MCPCM systems, with 5-symbol observation length, offer 1.6 dB, 3.6 dB, and 8 dB improvements relative to 2-ary, 4-ary, and 8-ary PSK systems, respectively. Also, it is shown that opti­ mum 2-ary and 4-ary non-coherent MCPCM systems can outperform 2-ary and 4-ary coherent PSK systems, respectively

Impact of wireless channel uncertainty upon M-ary distributed detection systems.

We consider a wireless sensor network (WSN), consisting of several sensors and a fusion center (FC), which is tasked with solving an $M$-ary hypothesis testing problem. Sensors make $M$-ary decisions and transmit their digitally modulated decisions over orthogonal channels, which are subject to Rayleigh fading and noise, to the FC. Adopting Bayesian optimality criterion, we consider training and non-training based distributed detection systems and investigate the effect of imperfect channel state information (CSI) on the optimal maximum a posteriori probability (MAP) fusion rules and detection performance, when the sum of training and data symbol transmit powers is fixed. Our results show that for Rayleigh fading channel, when sensors employ $M$-FSK or binary FSK (BFSK) modulation, the error probability is minimized when training symbol transmit power is zero (regardless of the reception mode at the FC). However, for coherent reception, $M$-PSK and binary PSK (BPSK) modulation the error probability is minimized when half of transmit power is allocated for training symbol. If the channel is Rician fading, regardless of the modulation, the error probability is minimized when training transmit power is zero

Constant-Envelope Multi-Level Chirp Modulation: Properties, Receivers, and Performance

Constant envelope multi-level chirp modulations, with and without memory, are considered for data transmission. Specifically, three sub-classes referred to as symbol-by-symbol multi-level chirp modulation, full-response phase-continuous multi-level chirp modulation and full-response multi-mode phase-continuous multi-level chirp modulation are considered. These modulated signals are described, illustrated, and examined for their properties. The ability of these signals to operate over AWGN is assessed using upper bounds on minimum Euclidean distance as a function of modulation parameters. Coherent and non-coherent detection of multi-level chirp signals in AWGN are considered and optimum and sub-optimum receiver structures are derived. The performance of these receivers have been assessed using upper and lower bounds as a function of SNR, modulation parameters, modulation levels, decision symbol locations, and observation length of receiver. Optimum multi-level chirp modulations have been determined using numerical minimization of symbol error rate. Closed-form expressions are derived for estimating the performance of multi-level chirp signals over several practical fading channels. Finally, spectral characteristics of digital chirp signals are presented and illustrated