The probability of symbol error (P/sub E/) performance is studied for cross-polarized M-QAM (M-ary quadrature amplitude modulation) and L-QPRS (L-ary quadrature partial response signal) systems operating in the depolarization crosstalk and differential phase shift environment. Explicit general formulas are provided and results presented for dual-channel 4-QAM (QPSK-quadrature phase-shift keying) and 9-QPRS. It is demonstrated that the P/sub E/ varies with a period of 90 degrees with differential phase shift and that L-QPRS systems are less sensitive to differential phase shift than the corresponding M-QAM systems; the sensitivity is measured by the ratio of maximum to minimum P/sub E/.< >
A method of calculating the probability of symbol error for the four-dimensional (4-D) diagonalizer using arbitrary constellations is presented. The method is applied to a 4-D constellation introduced by A. Gersho and V.B. Lawrence (1984), which is called the GL4-256 constellation. The probability of symbol error performance for GL4-256 is compared to that for the dual-channel 16-QAM case, and it is concluded that GL4-256 performs better for low crosstalk values, i.e., below -9.5 dB, with, the reverse being true for high crosstalk levels. Graphical results are presented for the case of uniform distribution.< >
The adaptive maximum-likelihood detector (MLD) is used to combat the deleterious effects of depolarization crosstalk in dual-channel M-QAM (quadrature-amplitude modulation) systems. The authors use a truncated union upper bound to calculate the probability of symbol error (P/sub es/) for dual-channel 16-QAM. The frequency of occurrence of P/sub es/ versus crosstalk phase shift, with crosstalk level as a parameter, and a 3-D plot of P/sub es/ as a function of the two crosstalk phase shifts, is presented. Assuming uniform distributions for the phase shifts, the average probability of symbol error is determined, and the performance of the MLD is compared to that of the diagonalizer canceller. It is shown that the MLD gains about 1.5 dB improvement in signal-to-noise ratio above that of the diagonalizer for crosstalk values above -10 dB, and that it actually uses the crosstalk to decrease the below the zero crosstalk value for crosstalk levels less than -10 dB.< >
Three different adaptive diagonalizers are compared on a probability of symbol error performance basis for dual-channel M-QAM systems. One diagonalizer (D3) greatly outperforms the other two, and any comparison of the performance of the diagonalizers to that of the minimum mean square error (MMSE) canceller should be based on D3. Receiver structures are also presented.< >
The application of an adaptive baseband canceller to dual-polarized 16-QAM systems operating in the presence of moderate to severe crosstalk is considered. Concentrating on a method which minimizes the mean square error in the estimation of received symbol values, a computational method is presented by means of which exact values of symbol error probability, P e , can be easily obtained for any specific values of relative crosstalk phase shift. Using this method, results are obtained which predict P e versus crosstalk and signal-to-noise levels for uniform distributions of the crosstalk phase shift angles. Results are given which show the frequency of occurrence of different P e values for uniformly distributed crosstalk phase shifts, and which show the maximum, minimum, and average values of P e over all values of relative phase angles. The receiver performance is seen to be acceptable, so far as average P e is concerned, in the presence of crosstalk levels that would make the system totally inoperable if no canceller were used. However, it is noted that for high crosstalk levels, values of P e can have a range of 100:1 or more as different values of relative phase shift are encountered.
Point-of-use chemical analysis holds tremendous promise for a number of industries, including agriculture, recycling, pharmaceuticals and homeland security. Near infrared (NIR) spectroscopy is an excellent candidate for these applications, with minimal sample preparation for real-time decision-making. We will detail the development of a golf ball-sized NIR spectrometer developed specifically for this purpose. The instrument is based upon a thin-film dispersive element that is very stable over time and temperature, with less than 2 nm change expected over the operating temperature range and lifetime of the instrument. This filter is coupled with an uncooled InGaAs detector array in a small, rugged, environmentally stable optical bench ideally suited to unpredictable environments. The resulting instrument weighs less than 60 grams, includes onboard illumination and collection optics for diffuse reflectance applications in the 900-1700 nm wavelength range, and is USB-powered. It can be driven in the field by a laptop, tablet or even a smartphone. The software design includes the potential for both on-board and cloud-based storage, analysis and decision-making. The key attributes of the instrument and the underlying design tradeoffs will be discussed, focusing on miniaturization, ruggedization, power consumption and cost. The optical performance of the instrument, as well as its fit-for purpose will be detailed. Finally, we will show that our manufacturing process has enabled us to build instruments with excellent unit-to-unit reproducibility. We will show that this is a key enabler for instrumentindependent chemical analysis models, a requirement for mass point-of-use deployment.
The performance of dual-polarized M -QAM systems is studied. By assuming coherence between the crosstalk and the desired signal, results are obtained for systems up to the modulation level of 64 QAM in each channel. Both balanced systems, with equal modulation levels in each channel, and unbalanced systems, with different modulation levels in each channel, are considered. Graphs are presented which show possible design tradeoffs to improve performance and suggest methods of system optimization. Each system is found to have an optimum value of relative transmitter power in the two channels. Analyses include the application of empirically based channel models giving relations between depolarization crosstalk, coplanar path attenuation, and differential fading levels.
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