Rl Davies

Wireless propagation measurements in indoor multipath environments at 1.7 GHz and 60 GHz for small cell systems

Given the current interest being shown in the utilization of the frequency band around 1.7/1.8 GHz and 60 GHz, work has been undertaken to determine channel characteristics in these two ranges. The authors describe wideband measurements which have been conducted in a variety of indoor locations. RMS (root mean square) delay spreads were calculated and used to compare levels of multipath activity at the two frequencies. The levels of multipath measured at the two frequencies can be related to the size of the rooms involved and the measurement techniques. Any differences due to atmospheric absorption at 60 GHz were found to be negligible.<<ETX>>

Strength of Joints Involving Composites

Abstract A description is given of the stress and strain systems in adhesively-bonded joints; special attention is given to the new problems which arise when bonding advanced fibrous composites. The anisotropic properties of composites can give great strength in the fibre direction, but it must be remembered that the tensile strength transverse to the fibres is less than of the matrix. Finite element analysis is used to predict the stresses and strains. In the ultimate, 3-dimensional non-linear mechanics with anisotropic non-linear stress-strain properties must be used. Finally, when using the mechanics principles described here, improvements in actual joint strength of 3 to 5 times were obtained.

A Ray Launching Method For The Prediction Of Indoor Radio Channel Characteristics

Presented here is an analytical method for the prediction of power delay profiles within a room environment. The model works directly on a 3-D description of a room. Provided here is a brief discussion of the model and a presentation of both measured and modelled results for delay spread values, which are shown to be in good agreement. The model’s output for narrowband signal strength values was found to be well represented by the usual theoretical distributions.

Ad-hoc wireless networking: contention free multiple access using token passing

Discusses mobile broadband communications with project groups such as ETSI RES 10 and ESPRIT LAURA providing much of the input. The immediate application of such systems would hope to provide high speed data links for users within a small location area and as such would have to be capable of overcoming the significant problems that the radio channel imposes. The authors discuss LANs and MAC protocols.

Linearity considerations in adaptive antenna array applications

The use of adaptive antenna in mobile communications base stations is self-explanatory. It offers the potential of increased spectrum efficiency, extended range of coverage and reduced delay spread. However, one major concern for adaptive antenna system is the non-linearity effects of the RF/IF chain upon digital baseband beamforming network. This contribution investigates these effects on the performance of adaptive antennas and suggests the use of linearised transceiver system to tackle the nonlinearity problem.

Application of linearised amplifiers in adaptive antennas

The use of adaptive antennas in mobile communications base stations is self-explanatory. It offers the potential of increased spectrum efficiency, extended range of coverage and reduced delay spread. However, one major concern for adaptive antenna system is the non-linearity effects of the RF/IF chain upon digital baseband beamforming network. The article investigates these effects on the performance of adaptive antennas and suggests potential solutions to these non-linearity problems in base station transceiver systems.

WIN with OSI, the sequel: A Case Study of TETRA Digital Private Mobile Radio.

The increasing deployment of computer-networking services in fixed networks motivates the provision of similar services in wireless networks. In the case of PMR systems there are already several types of data communications service (MOBITEX, MPT1327, Motorola RD-LAP for example).

Prediction modelling of indoor radio propagation for the pico-cellular environment

An analytical method for the prediction of power delay profiles within a room environment is presented. The model works directly on a 3D description of a room. This simple geometry-based reflection model for the calculation of delay spread values has been shown to work well with measured results. The maximum and typical delay spreads have been found by both model and measurement to be largely determined by room size: the larger the room the greater the delay spread. The narrowband characteristics have been modeled and found to agree well with the standard theory.<<ETX>>