Kenneth V. Cartwright

Blind phase recovery in general QAM communication systems using alternative higher order statistics

Blind phase recovery for square QAM communication systems using higher order statistics is well established. It is demonstrated that this method can be adapted for cross QAM constellations, if alternative fourth-order statistics are used. However, a four quadrant inverse tangent function must now be used. Monte Carte simulation provides evidence of the usefulness of the approach.

Blind phase recovery in cross QAM communication systems with eighth-order statistics

A new method for blind phase estimation that uses eight-order statistics is described. For cross QAM constellations, it provides about the same root mean square error (RMSE) as the fourth power method with about one-sixth to one-fourth the number of samples. Monte Carlo simulations are provided to demonstrate the usefulness of the method.

TCM without constellation expansion penalty

We present a family of constant-amplitude constellations of even dimensions 8 and above. These constellations allow trellis coded modulation to be implemented without the usual penalty paid for constellation expansion. The new constellations are generated by concatenating either n QPSK points or n QPSK points rotated by 45 degrees, for any n > 4. Our constellations double the number of points available for transmission without decreasing the distance between points and without increasing the average or peak energies, introducing asymmetry, or increasing the modulation level. Effective gains of 2.65 dB with minimum complexity through 6.42 dB with moderate complexity are demonstrated using the 8D constellation.

Fourth power phase estimation with alternative two-dimensional odd-bit constellations

It is well established that the fourth power phase estimator does not perform well for QAM cross (i.e., odd-bit) constellations. In this paper, new two-dimensional rectangular constellations are presented that give much improved performance, at a reasonably low increase in required constellation energy. For example, the 128B-COB constellation reduces the variance by an order of magnitude, while increasing the constellations average energy by only 0.28 dB and the peak to average energy ratio by 1.25 dB, relative to 128-QAM.

A Novel Expanded 16-Dimensional Constant Envelope Q 2 PSK Constellation

We introduce a 16-dimensional constant-amplitude constellation that is generated by concatenating either four constant envelope quadrature-quadrature phase shift keying (CEQ2PSK) symbols from Saha and Birdsall or four CEQ2PSK symbols recently discovered by Cartwright and also introduced here. Our new constellation doubles the number of points available for data transmission without decreasing the distance between points or increasing energy, and may therefore be used in a trellis coded modulation (TCM) system without constellation expansion penalty. Because the new constellation has constant envelope, the modulation scheme becomes very attractive for nonlinear channels such as the magnetic recording channel or the satellite channel with traveling wave tube amplifiers.

An optimum hardware detector for constant envelope quadrature-quadrature phase-shift keying (CEQ/sup 2/PSK)

A hardware detector for constant envelope quadrature-quadrature phase-shift keying (CEQ/sup 2/PSK) is proposed. It uses appropriate hard decisions; yet, it achieves optimum probability of bit error performance, unlike the suboptimum detector of Saha and Birdsall. This optimum performance is verified through Monte Carlo computer simulations. Additionally, a more correct expression is given for the probability of bit error performance for CEQ/sup 2/PSK, which gives the gain over nonconstant Q/sup 2/PSK as 1.44 dB, rather than the previously published value of 1.76 dB.

Blind phase recovery in cross QAM communication systems with the reducedconstellation eighth-order estimator (RCEOE)

A new method for blind phase estimation that uses eight-order statistics is described. For cross QAM constellations, it provides about the same root mean square error (RMSE) as the fourth power method with about one-sixth to one-fourth the number of samples. Monte Carlo simulations are provided to demonstrate the usefulness of the method.The eighth-order (EOE) phase estimator (K.V. Cartwright, 1999) is modified to work for an eight-symbol symmetrical constellation, so that the large signal-to-noise (SNR) performance is not limited by self-noise. By using only the eight highest energy points of cross-QAM constellations, a reduced constellation eighth-order estimator (RCEOE) is proposed. Computer simulations for 128-QAM show that this new method performs substantially better than the recently introduced APP phase estimator of Wang et al. (2003). However, simulations with 32-QAM show little performance advantage of the RCEOE over the APP estimator, for SNR values normally of interest, whereas for low SNR, the improvement is significant. Application to any constellation which can be reduced to an 8-symbol quadrant symmetrical sub-constellation is straight-forward

A Trellis-Coded Modulation Scheme with a Novel Expanded 16-Dimensional Constant Envelope Q2PSK Constellation

This paper presents a TCM scheme that uses a new expanded 16-Dimensional Constant Envelope Q2PSK constellation along with a simple convolutional encoder of rate 2/3. An effective gain of 2.67 dB over uncoded CEQ2PSK is achievable with low complexity, and without suffering from constellation expansion penalty. Larger coding gains are easily achieved with encoders of higher rates. In addition, an optimal hardware implementation of the required decoders is described.

A comparison of three diagonalizers, adaptive crosstalk cancellers, in dual-polarized M-QAM systems

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. >

GENp2-1: A Simple Improvement to the Viterbi and Viterbi Monomial-Based Phase Estimators

It is well known that the Viterbi and Viterbi Monomial-Based Phase Estimator, which includes the Mth Power Estimator, performs poorly for cross QAM signals. However, it is shown here that by allowing the power of the monomial to be negative, much improved performance can be realized at medium to high signal- to-noise ratios (SNR). Monte Carlo simulations are used to demonstrate the efficacy of this novel simple extension, for 32- and 128-QAM systems. In principle, this extension can also be applied to other constellations, e.g., (4,12)-PSK.