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We develop accurate and robust one-dimensional EXIT chart methods to design raptor codes with binary and higher-order modulations on AWGN channels over any desired range of SNRs. We formulate the check-node degree distribution optimization as a linear program that optimizes a suitable objective function of the desired operating points. The throughput curves predicted by the analysis are easily compared...
Unequal error protection (UEP) and rateless coding are both methods used to combat channel uncertainty. With a rateless code, the code rate automatically adapts to the channel quality through the use of incremental redundancy. However, a rateless code lacks the ability to differentiate priorities and all bits suffer the same long delay in poor channel conditions. In contrast, UEP ensures reliable...
A basis function expansion to reduce the demodulation complexity of continuous phase modulation (CPM) signals applicable for either coherent or non-coherent reception in tactical networks is presented. Results show that a signal space receiver based on B-splines approximates a wide variety of CPM signal sets with only a small number of basis functions and is particularly useful for spectrally efficient...
This paper introduces and analyzes scale-time offset robust modulation (STORM) for use in code division multiaccess (CDMA) systems using spread quadrature phase shift keying (QPSK) to increase the capacity of a CDMA network. Since current commercial CDMA systems have dedicated spectrum, the capacity is primarily limited by the interference of other CDMA users; thus, power control and multiuser interference...
This paper considers the case for using a ??digital IF?? (intermediate format) as an alternative to conventional analog IF (intermediate frequency) for distributing satellite uplink and downlink signals within modern high-capacity military satellite communications Earth terminals. ??Digital IF?? is defined as a purely digital format enabled by digital I & Q (in-phase and quadrature) sampling for...
This paper proposes a scheme of continuous phase modulation (CPM) receivers using frequency domain equalization and conventional parallel and serial CPM receiver structures. Frequency domain equalizers for CPM block transmissions provide spectral and power efficient wireless communications with less complexity than conventional time-domain processing receivers over frequency selective fading channels...
A multisymbol noncoherent receiver suitable for coded continuous-phase frequency-shift keying is developed and analyzed. Unlike coherently detected signals, the modulation index of the waveform does not need to be rational with a small denominator, and the oscillator only needs to be stable for the duration of a small group of symbols. The receiver is analyzed in terms of its symmetric information...
Tactical air-to-ground channels present a number of challenges for physical (PHY) layer waveform design including: (i) airborne platform dynamics (i.e., Doppler, frequency offset, jerk, etc.), (ii) benign to severe ground-level multipath, and (iii) partial to full blockage of the line-of-sight (LOS) path. Legacy military waveforms are not sufficiently robust to operate effectively in these severe...
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...
Carrier sense multiple access (CSMA) is the conventional medium access method used in wireless ad hoc networks. it can be enhanced as a space-division based CSMA (namely, SD-CSMA) by using multi-antenna techniques, which allows concurrent link communications in the network. In this paper, we present a MAC design that can adaptively switch between CSMA and SD-CSMA in multi-antenna based ad hoc networks...
We investigate a transmission scheduling protocol that exploits direct-sequence spread-spectrum (DSSS) modulation to improve the performance of a mobile, ad hoc network. Since DSSS allows for packet capture in the presence of other nearby transmissions, multiple-access interference is less detrimental to network performance. We design a new transmission scheduling protocol that takes advantage of...
The effects of adaptive-rate transmissions and routing on the total throughput of a slow-frequency-hop packet-radio network are considered. Adaptive rates are achieved through the use of error-control coding with perfect side information. Both fixed-length codes and variable-length codes are considered. Performance results are obtained for direct transmission (i.e., no routing), two-hop limited routing,...
There are many instances where it is desirable or even essential to rapidly build a functional radio receiver to recover symbols from an unknown modulated source. The term ??rapid radio?? refers to a demonstrable analysis environment and receiver implementation methodology for rapid deployment. An automated tool for signal analysis requires several stages for the estimation and classification of the...
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