A multichip package was developed to meet the market requirements for an advanced wireless telephone handset. The successful testing process of this multichip package, comprising test requirements, test strategy, test development and results from the production test is presented. A wireless telephone handset, containing the multichip package is currently in high volume production within Philips.

A code-division multiple-access (CDMA) communication system is studied where a trellis-based scheme is used for data encoding and modulation. The signature sequences (spreading codes), which are assigned to the direct-sequence spread-spectrum (DS/SS) modulator according to the encoding rule, are taken from a biorthogonal set. We derive the optimum detector by maximizing the likelihood ratio. In addition to the optimum multiuser detector with very high computational complexity, we present a multistage detector and a scheme based on a reduced tree search algorithm. The error probability is evaluated by deriving upper and lower bounds as well as by Monte Carlo simulations. We show that the optimum receiver is near-far resistant. The results from the numerical examples indicate that the suboptimum detectors are also capable of alleviating the near-far problem.

A multiuser communication system is considered where K users share a channel with multipath propagation by using code division for multiple access. Data modulation is carried out by binary phase shift keying and direct sequence spread spectrum signaling. The micro-cellular communication media is modeled as a frequency selective fading channel with multipath propagation. The multipath diversity of the received signals from the K users is exploited by a bank of K RAKE correlators. Algorithms based on the maximum likelihood rule have been developed for estimating the complex channel coefficients as well as for detection of the desired data packets from the sufficient statistics provided by the RAKE correlators. The performance of the resulting multiuser detector is evaluated analytically and via Monte Carlo simulations. The results indicate that the estimator of the channel coefficients has a variance close to the Cramer-Rao lower bound, and that the proposed multiuser detector is capable of eliminating the near-far effect as well as processing the signals propagated through multiple paths.>

A direct-sequence spread-spectrum (DSSS) coherent RAKE-receiver demodulating M-ary phase-shift keyed (MPSK) signals is presented for microcellular communication systems with frequency-selective fading channels. Since the channel fading is due to multipath propagation, the received signal contains multipath or time diversity which is resolved at the receiver by a RAKE-structure. The maximum-likelihood (ML) rule is invoked to estimate the phases, and the combining factors of the receiving paths, as well as the frequency offset between the carrier of the receiver and the transmitter. The ML algorithm is simplified by using decision-directed feedback. The resulting digital algorithms for synchronization, data demodulation, and frequency error detection (FED) are well suited for digital implementation because of their fairly low numerical complexity. Analytical expressions of the bit error probability versus signal-to-noise ratio (SNR) and versus frequency offset are presented. In addition, experimental results using Monte-Carlo simulations have also been carried out. The results show a negligible influence of the decision-direction above a certain SNR, as well as a "robust" transient behavior of the phase estimation and the automatic frequency control (AFC) scheme.>