732 research outputs found
Cyclic redundancy check-based detection algorithms for automatic identification system signals received by satellite.
This paper addresses the problem of demodulating signals transmitted in the automatic identification system. The main characteristics of such signals consist of two points: (i) they are modulated using a trellis-coded modulation, more precisely a Gaussian minimum shift keying modulation; and (ii) they are submitted to a bit stuffing procedure, which makes more difficult the detection of the transmitted information bits. This paper presents several demodulation algorithms developed in different contexts: mono-user and multi-user transmissions, and known/unknown phase shift. The proposed receiver uses the cyclic redundancy check (CRC) present in the automatic identification system signals for error correction and not for error detection only. By using this CRC, a particular Viterbi algorithm, on the basis of a so-called extended trellis, is developed. This trellis is defined by extended states composed of a trellis code state and a CRC state. Moreover, specific conditional transitions are defined to take into account the possible presence of stuffing bits. The algorithms proposed in the multi-user scenario present a small increase of computation complexity with respect to the mono-user algorithms. Some performance results are presented for several scenarios in the context of the automatic identification system and compared with those of existing techniques developed in similar scenarios
Spatial Coded Modulation
In this paper, we propose a spatial coded modulation (SCM) scheme, which
improves the accuracy of the active antenna detection by coding over the
transmit antennas. Specifically, the antenna activation pattern in the SCM
corresponds to a codeword in a properly designed codebook with a larger minimum
Hamming distance than its counterpart conventional spatial modulation. As the
minimum Hamming distance increases, the reliability of the active antenna
detection is directly enhanced, which in turn improves the demodulation of the
modulated symbols and yields a better system reliability. In addition to the
reliability, the proposed SCM scheme also achieves a higher capacity with the
identical antenna configuration compared to the conventional spatial modulation
technique. Moreover, the proposed SCM scheme strikes a balance between spectral
efficiency and reliability by trading off the minimum Hamming distance with the
number of available codewords. The optimal maximum likelihood detector is first
formulated. Then, a low-complexity suboptimal detector is proposed to reduce
the computational complexity, which has a two-step detection. Theoretical
derivations of the channel capacity and the bit error rate are presented in
various channel scenarios, i.e., Rayleigh, Rician, Nakagami-m, imperfect
channel state information, and spatial correlation. Further derivation on
performance bounding is also provided to reveal the insight of the benefit of
increasing the minimum Hamming distance. Numerical results validate the
analysis and demonstrate that the proposed SCM outperforms the conventional
spatial modulation techniques in both channel capacity and system reliability.Comment: 30 pages, 17 figure
Single-RF spatial modulation requires single-carrier transmission: frequency-domain turbo equalization for dispersive channels
In this paper, we propose a broadband single-carrier (SC) spatial-modulation (SM) based multiple-input multipleoutput (MIMO) architecture relying on a soft-decision (SoD) frequency-domain equalization (FDE) receiver. We demonstrate that conventional orthogonal frequency-division multiplexing (OFDM)-based broadband transmissions are not readily suitable for the singleâradio frequency (RF) assisted SM-MIMO schemes, since this scheme does not exhibit any substantial performance advantage over single-antenna transmissions. To circumvent this limitation, a low-complexity soft-decision (SoD) FDE algorithm based on the minimum mean-square error (MMSE) criterion is invoked for our broadband SC-based SM-MIMO scheme, which is capable of operating in a strongly dispersive channel having a long channel impulse response (CIR) at a moderate decoding complexity. Furthermore, our SoD FDE attains a near-capacity performance with the aid of a three-stage concatenated SC-based SM architecture
RADAR-EMBEDDED SATCOM WITH DEEP NEURAL NETWORK DEMODULATION
Approved for public release. Distribution is unlimited.In this work, the feasibility, design, and implementation of radar-embedded communications with
satellite applications are investigated. We design a deep neural network (DNN) machine learning detector to
demodulate SATCOM data. The performance result is compared with the detection method of using
maximum likelihood estimation (MLE) to estimate the amplitude and phase of the radar signal, which is
followed by a maximum likelihood detection (MLD) receiver. Pulsed radar and linear frequency modulation
(LFM) waveforms are chosen to embed communications symbols. Quaternary phase-shift keying (QPSK)
and eight phase-shift keying (8PSK) modulations are used for illustration. In this work, three DNN
demodulators for radar-embedded communications are developed. One of the DNN detectors actually
outperforms the MLD demodulator and is shown to be robust for pulsed radar-embedded communications.
One of our goals is to embed satellite communications into LFM waveform, which is used in synthetic
aperture radar (SAR). The DNN works well for LFM radar-embedded communications when the received
LFM phase offset is removed a priori. However, the DNN symbol error rate (SER) performance suffers
when the LFM phase offset is introduced for large RCR. Lastly, we perform laboratory transmission and
reception tests: a) shielded cable and b) over-the-air (OTA) tests. It is shown that pulsed radar-embedded
communication is feasible with both MLE-MLD and DNN detectors with reasonable SER performance.Lieutenant, United States Nav
MIMO free-space optical communication employing subcarrier intensity modulation in atmospheric turbulence channels
In this paper, we analyse the error performance of transmitter/receiver array free-space optical (FSO) communication system employing binary phase shift keying (BPSK) subcarrier intensity modulation (SIM) in clear but turbulent atmospheric channel. Subcarrier modulation is employed to eliminate the need for adaptive threshold detector. Direct detection is employed at the receiver and each subcarrier is subsequently demodulated coherently. The effect of irradiance fading is mitigated with an array of lasers and photodetectors. The received signals are linearly combined using the optimal maximum ratio combining (MRC), the equal gain combining (EGC) and the selection combining (SelC). The bit error rate (BER) equations are derived considering additive white Gaussian noise and log normal intensity fluctuations. This work is part of the EU COST actions and EU projects
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