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System-level simulations for ad hoc networks require the mean power that is received by an arbitrary unit of the piconet as an input parameter. Since the radio channel in piconets depends strongly on the environment in which two communicating units are located, easily applicable models for the mean received power must be determined by a few relevant, explicitly geometrical quantities. Starting from a very general description of the stochastic radio channel by an integral equation, it is shown that these quantities are the surface area and the volume of the domain in which the transmitter and the receiver can move. On the basis of an exponential path loss model with path loss exponent q, a lower and an upper bound for the mean received power are derived. The resulting analytical expressions are highly flexible and allow a quick calculation of bounds for the mean received power in many practically relevant cases.

A novel approach of a parametric stochastic radio channel model describes the dispersive nature of the wave propagation in indoor and outdoor environments with regard to delay and incidence angle. Effects of large-scale fluctuations are considered, too. Channel dispersion is mathematically denoted by the delay-angle spread function which results from the coherent superposition of the contributions arising from a certain number of multipath components (MPC). A classification of the propagation scenarios can be achieved by means of their topological properties. Local parameters defining the instantaneous constellation of the impinging MPC as well as global parameters giving a statistical characterization of the propagation environment (PE) are derived and form the elements of the channel model. This paper focuses on two indoor PE characterized by a line-of-sight (LOS) and a nonline-of-sight (NLOS) connection between the transmitter and receiver, respectively. Measurements in the 24 GHz range (ISM band) are presented to demonstrate the physical properties of the propagation process in both PE and to determine their global parameters. LOS scenarios show "discrete" MPC arising from specular reflections. In case of a NLOS situation the MPC exhibit a clustering pattern due to building and wall structures which can be statistically described by means of a cluster model, an extension of the previously given modeling approach.

Detailed knowledge of radio propagation effects is a keystone for the development and performance assessment of mobile communication systems. Although a lot of investigations have already been carried out, there remains a need to gain deeper insight into the complex mechanisms which govern radio propagation. The authors first present a summary of the propagation mechanisms and discuss some issues related to radio channel parameters and measurement techniques. Then a systematic description of the propagation and simulation models developed within various European projects is given. The survey focuses on the main features of these models and the rationale behind their elaboration.

The properties of common transversal filters are well known. Transversal filters with continuously tapped delay lines have the advantage that they do not show a periodic continuation of the frequency characteristic. Therefore it is not necessary to use an additional filter for suppressing higher frequency components. After an introduction to CTT filter theory the realization of transversal filters with continuous inductive tapping (ICTT filters) is discussed. The description of the practical synthesis of a low-pass filter and a 90° wide-band phase shifter is followed by the interpretation of measured frequency characteristics.