We investigate the performance of BPSK and QPSK with coherent detection and matched filtering in the presence of both time and phase asynchronous cochannel interfering signals. More precisely, we analyze the role played by different channel statistics on the distribution of the decision variable at the output of the matched filter. The results show that the Gaussian approximation is accurate not only in the (obvious) case of a large number of interferers, but also when the desired signal is subject to fading, whatever the number of interferers is. For example, when the desired signal is subject to Rayleigh fading, even in the presence of only one unfaded interferer the Kullback-Leibler distance between the exact distribution of the decision variable and that obtained with the Gaussian approximation on the interference is lower than 0.01 [nats] for all cases of practical interest.

Influence of fading on the Gaussian approximation for BPSK and QPSK with asynchronous cochannel interference

A framework for the performance characterization of short-range communications systems is developed with the intention of investigating the feasibility of new multimedia wireless services at millimeter waves (MMWs). Both narrow- and wide-band systems are considered for mobile and/or fixed users. This paper aims at defining and evaluating proper metrics to characterize the service quality for the user and jointly takes the propagation characteristics, the transmission techniques, and the multiple access protocols into account. The definition of service-oriented metrics is emphasized. Three different real scenarios operating at MMW are investigated with a unified perspective: intelligent transport systems, wide-band local-area networks, and local multipoint distribution systems for interactive video services. The role played by the MMW band in the development of these services is discussed. In each scenario, accurate propagation analysis is carried out and suitable countermeasure techniques are pointed out in order to join suitable service-quality levels. The methodology considered is based on both analytical and semianalytical tools for performance evaluation.

Millimeter waves for short-range multimedia communication systems

We derive a new expression for the exact bit-error probability for the detection of a coherent binary phase-shift keying signal experiencing a number of asynchronous interferers having unequal power levels in Rayleigh fading channels. The new expression is readily computed in terms of the coefficients of a Hermite polynomial.

Exact probability of error of BPSK communication links subjected to asynchronous interference in Rayleigh fading environment

The role played by the number of interferers and the modulation choice in the performance of slotted Aloha networks with Rayleigh fading is investigated and discussed; the case of multiple transmitted power classes is also considered. A new capture model which takes the number of actual interferers into account is proposed. The network capacity is analytically estimated, and significant differences (depending on the modulation scheme) are found with respect to previously published results carried out by means of more common (and less accurate) capture models, also when the case of different transmitted power classes is considered.

On the capacity of slotted Aloha with Rayleigh fading: the role played by the number of interferers

In this paper, we evaluate the performance of fully distributed power control algorithms (PCAs) for cellular mobile radio systems based on frequency-time division multiple access; the goal is to show that the optimization of the PCA requires a suitable definition of the performance figure and proper consideration of user mobility and the implemented handover algorithm (HA). Signal-level-based and carrier-to-interference-ratio (CIR) balancing schemes are investigated. Both uplink and downlink are taken into account. The optimization is carried out by observing both the outage probability and the drop-out probability, which is related to the duration of outage events. It is shown that the difference between the performance evaluated through the two metrics is related to the presence of suitable HAs. The average number of handovers per call is also considered, as a measure of network stability when using the different PCAs.

On the optimization of fully distributed power control techniques in cellular radio systems

This paper presents a general methodology for performance characterization of digital transmission systems in the presence of cochannel interference, as a function of the actual number of interferers (ranging from zero to infinity). The bit error probability in time-invariant channels and outage probability in time-varying quasi-stationary channels are discussed. More precisely, a general approach to an outage probability definition based on the concept of the outage domain is introduced. This allows the discussion of the relation to the other definitions which have appeared in the literature and the proposal of some new more accurate methods for the evaluation of outage probability. A suitable comparison between exact evaluation, the well-known Gaussian approximation, and the other new approaches proposed in this paper, is carried out to evaluate performance, bit error probability is suitably obtained for linearly modulated signals by adopting a semianalytical approach, and for nonlinear (e.g., continuous phase) modulation signals, by means of simulation. Finally, as an example, the different approaches to derive performance discussed in the paper have been applied to a linear microcellular scenario.

V. Tralli

Papers

Performance characterization of digital transmission systems with cochannel interference