We investigate the reverse link power control of the cdma2000 system where multiple traffic channel signals of different data rates are code-multiplexed and transmitted in a multipath Rayleigh fading environment. In particular, we evaluate the performance of a closed-loop power control scheme utilizing one power control command for all traffic channels. Simulation results show that the use of one common power control command may not be optimal for all code-multiplexed channel signals of different data rates. This is largely due to the different variations in the effective bit signal-to-interference-plus-noise ratios (SINRs) for a given fading rate in a multipath fading channel. With an observation of the performance improvement by more than 1 dB, we propose to use independent power control for each channel signal.

Given a quasi-cyclic code with minimum Hamming distance d, a set of convolutional codes is derived with free distance equal to d. It is shown that an increase in the rate of these codes results in a decrease in the memory length. The connection between these codes is illustrated with several well-known quasi-cyclic codes. The free distance of some partial unit memory convolutional codes can be determined using the results in this correspondence.

This paper presents an analytical model to evaluate the performance of the multistage multicarrier demultiplexer/demodulator (M-MCDD) for satellite communications in the presence of additive white Gaussian noise (AWGN) and adjacent channel interference (ACI). The probability of bit error is derived. A procedure for numerical computation of the probability of bit error based on the Gauss quadrature rule (GQR) is introduced. Effects of imperfect filtering and channel separation on the performance are discussed.

This paper examines the effect of timing errors on QPSK/FDMA signals regenerated by a SAW-based group demodulator. The presence of a timing offset not only degrades the performance of that channel, but also increases the amount of its interference into other channels. Time windowing of the input to the chirp Fourier transform is shown to reduce the impact of the timing errors, but at the cost of an increased output noise variance. Measurements are presented for the bit-error rate (BER) performance of a single channel with a fixed timing offset using a surface acoustic wave (SAW) group demodulator based on the convolve-multiply-convolve (CMC) configuration with Kaiser-Bessel windowing.

The largest quasi-cyclic subcode of the Reed-Muller code R(r,m), invariant under the shift T/sup 2m-l/ is determined. This code, denoted QCR(r,m,l), is presented through its module decomposition into cyclic submodules. The smallest regular trellis diagram (SRTD) is defined for block codes. This trellis and its construction algorithm are given for the class of cyclic-form codes. Using the cyclic-form structure of QCR(r,m,l), the 2/sup l/-section SRTD of this code is determined. The eight-section SRTD is given for the Reed-Muller codes R(r,m). The quasi-cyclic subcodes of R(r,m) with regular 2/sup l/-section minimal trellis diagrams are presented.

A construction of the Gosset lattice is considered that has practical advantages over other constructions of the same lattice. Codes derived from this construction have been shown to exhibit a null at DC in their baseband spectrum. A two-stage approach to the demodulation of this construction of the Gosset lattice is discussed. This demodulator consists of an initial stage which may declare erasures and a secondary stage designed to correct erasures. A study of erasure events is made and then used to reduce the number of steps in the second-stage correction algorithm. While the overall demodulator is somewhat more complex than a straight forward maximum-likelihood demodulator designed for this construction, the present structure has the advantage of greater speed.>

A rarely used definition of the Gosset lattice is revived to construct codes which (unlike other Gosset lattice codes) have a null at DC in their baseband spectrum. A closed-form expression for the code spectrum is derived, and the bandpass spectrum of this code is compared to the spectrum of an E/sub 8/ construction of the same code. A fast sequential method of demodulation is described. This two-stage demodulator consists of a simplified algorithm that can declare erasures to provide speed in demodulation and a maximum-likelihood algorithm used to maintain error performance.>