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Reed Solomon (RS) forward error correction (FEC) coding in conjunction with M-ary hyper phase-shift keying (MHPSK) and soft decision decoding is considered in order to improve the robustness of a high spectral efficiency, non-linear satellite communications link. In this paper, a system that utilizes RS encoding of the information symbols which are then transmitted with MHPSK is evaluated in terms...
The performance of a serially concatenated convolutional code (SCCC) for frequency hopped M-ary phase shift keying communication systems over an additive white Gaussian channel noise (AWGN) in the presence of a partial-band noise jammer is discussed in the paper. The scaling of the log-likelihood ratio (LLR) which improves the SNR dynamic range and the jamming strategy are also discussed in the paper...
The HF channel supports the wireless needs of expeditionary forces for both communication between nearby unit members (<5 km) and over-the-horizon reach-back to ship or rear base (OTH > 500 km). Cooperative communication combined with MIMO methods employing randomized space-time block coding (RST-BC) promise significant gain for over-the-horizon transmission which allows lower transmit power...
This paper investigates the invariant detection problem of quadrature phase-shift keying (QPSK) direct sequence spread spectrum (DS-SS) signals in additive white Gaussian noise (AWGN). Using the complex Gaussian mixture signal model and invariance principle, we consider the constant-false-alarm-rate (CFAR) invariant detectors and other sub-optimal invariant tests, including the uniformly-most-powerful-invariant...
As cellular technologies evolve, evaluation of modulation schemes with frequency selective fading is an important consideration. We present methods to evaluate a high data rate DS-SS BPSK reverse link, over a wideband channel, with filters and a modified delayed signature dual finger RAKE. For several years the standard Gaussian approximation has been used to estimate error rate of DS-SS BPSK. We...
In this paper, we present a single-carrier (SC) waveform with smart antenna and frequency domain equalization (FDE) technologies to effectively combat both urban multipath and radio interference. It is designed to be power efficient, spectrally efficient, high quality, and capable of operating at vehicular speeds with long range. It can work on a small form factor device to support transport of streaming...
The majority of prior work in signal-to-noise ratio estimation makes fairly strong assumptions concerning a priori knowledge of the channel state and signal. For instance, many of these estimators assume knowledge of the modulation scheme of the signal, or even complete knowledge of the transmitted set of modulated data symbols (typically through the use of training sequences). Even more universally,...
In this paper, the expression for symbol error rate (SER) or BER of linear modulation in Rayleigh fading as a function of signal-to-noise ratio (SNR), modulation scheme and diversity order, is inverted, thereby giving SNR as a function of SER. The key is to represent the PDF (or MGF) by a Maclaurin series and discard all but the first one or two terms. For large SNRs, the first term in the series...
Modern Unmanned Aerial Vehicles (UAVs) have the capability of carrying sensors that produce large amounts of data. A high speed wireless data link is required to transfer this data to other systems for processing. This paper presents an FPGA-based implementation of a high data-rate (350 Mbps) QPSK modulator and demodulator to support a high data rate relay from a UAV to a ground station. By using...
Efficient use of spectrum requires an accurate determination of interference effects. In this paper, we introduce a radio to radio (R2R) factor that quantifies the interference effects of one radio waveform on another based on multiple waveform properties instead of solely on intermediate frequency (IF) signal power. The R2R factor is formulated as a dimensionless correction term in the victims communication...
In military tactical communications, cognitive radio (CR) has been proposed as a potential technology. A CR network can support vital communications among troops and vehicles in an alien territory with unfamiliar or unknown radio environment that may be changing dynamically in time. We propose a new approach for dynamic detection of ??white spaces?? i.e. available radio channels, based on a novel...
In 2007, MIT Lincoln Laboratory began supporting the United States Air Force (USAF) MILSATCOM family of advanced beyond line of sight terminals increment 2 (FAB-T Inc 2) program. The Laboratory led the development and implementation of the Ka-band high data rate (Ka HDR) waveform for the transportation of airborne intelligence, surveillance, and reconnaissance (AISR) data from air assets to any number...
The Link-16 is the tactical data link utilized by the Joint Tactical Information Distribution System (JTIDS). The JTIDS system is important due to its wide use by U.S. armed forces, NATO, and other allied militaries. Link-16 is a hybrid frequency-hopped/direct sequence spread spectrum system that utilizes minimum-shift keying (MSK) to modulate the chips, cyclical code-shift keying (CCSK) to modulate...
We present a cross-layer and multilevel unequal error protection (UEP) approach for robust video transmission over noisy wireless channels. We combine the UEP schemes at the application layer (i.e., multi-level unequal importance of compressed H.264/AVC video data) and physical layer (multi-resolution asymmetric 8-PSK modulation). The proposed scheme multiplexes the video data by mapping it to the...
In this paper, we consider techniques for communicating in the presence of interference. In particular, we consider the simple scenario of a BPSK communication system in the presence of a constant modulus (CM) interferer. Using computer simulations and analytical approximations, we compare the performances of four detectors for recovering the communications signal in an additive white Gaussian noise...
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