The joint performance of a turbo decoder and RAKE receiver using the MAP algorithm depends on the accuracy of the channel reliability factor. In a high data rate/low processing gain environment, inherent interference that results from non-idealities of the RAKE receiver complicate the estimation of the channel reliability factor. The combined performance of a turbo decoder and RAKE receiver is analyzed in a time dispersive and time-varying channel with distinct multipath components. Approaches are examined for estimating the channel reliability factor using the limited information that is known by the RAKE receiver. The sensitivity of performance to SNR mismatches is computed. The impact of the processing gain and the number of multipath components on BER performance is analyzed along with the effect of the channel time coherence. By accounting for the non-ideal RAKE interference effects, improvements in the channel reliability factor calculation result in BER performance improvements on the order of 0.5-2 dB.

Receiver structures for an optimal noncoherent receiver when a transmitted signal experiences a random frequency shift are derived. Error rate performance, obtained by simulation, is then developed and compared with the standard noncoherent correlator. Results indicate that 1) ignoring the frequency shift by using a standard noncoherent correlator leads to severely degraded performance relative to the optimal noncoherent receiver and 2) even the optimal noncoherent receiver accommodating a random frequency shift exhibits degraded performance as the unknown frequency range grows.

This paper re-introduces the concept of service provider choice within hierarchical wireless networks of the future. The service provider does not have to be a PCS, cellular, or satellite carrier. The service provider might have agreements with multiple PCS, cellular, or satellite carriers to provide wireless services to its subscribers. The concepts of location billing and third generation networks have been studied in the past, but the concept of enabling users to switch between service providers based on their location is certainly novel. The objective is to present a generic service description of this concept and to propose a basic architecture that may foster future study. This paper is not a feasibility study, although it identifies the issues that may need to be considered to determine the viability of service provider choice based on a subscriber's location.

A new technology is suggested for emergency services which allows immediate aid to be provided using an accurate estimate of the incident location. The user can activate the request for assistance by simply pressing a button. The technology is based on the integration of an innovative FM location technique and a smart mobile phone. The system architecture described in this paper permits both voice and data to be jointly transmitted over the same standard cellular channel without redialing.

Intelligent network (IN) and non-IN architectures are described that support personal communications services (PCS) number portability independent of the service provider (SP) that is used. Database query rates and call setup times are computed for selected architectures. To attain number portability, it is concluded that Common Channel Signaling System 7 is the principal ingredient for successful operation no matter which architecture is selected.

This paper describes the design and performance of a spread-spectrum medium frequency (MF) radio network. The network utilizes a simulcast time slotted transmission scheme in which radios that receive a data message in one time slot repeat the message in the next slot. Spread-spectrum radio designs that operate efficiently with simulcast under a variety of channel conditions are investigated. The performance of the radio network is characterized in terms of radio connectivity and message reaction time.

Narrowband jamming and interference due to other users in spread spectrum communication systems can be effectively suppressed by using digital whitening. As a result, an impressive improvement in receiver performance can be obtained. The digital whitening is accomplished using a transversal filter whose coefficients are selected by either a Wiener algorithm or a maximum entropy algorithm. Filters obtained by use of these algorithms are evaluated for various jamming and signaling conditions and are found to exhibit comparable performance over a wide range of input signal-to-noise ratios.

Adaptive mean-square error (mse) and maximum-likelihood detection (MLD) algorithms for a dual-channel digital communication system in the presence of interchannel interference and white Gaussian noise are presented. The mse algorithm forms estimates of the transmitted symbols from a linear combination of received symbols using weights that minimize the mse between transmitted and estimated symbols. The nonlinear MLD algorithm minimizes the probability of symbol error by maximizing the probability of the received signal samples on the two channels over ail possible transmitted symbol pairs. The probability of error is derived for the two algorithms when quadrature phase-shift keying (QPSK) is used as a modulation technique, and is compared with that of a dual-channel QPSK system having no compensation for the crosstalk.