Abstract-Due to the site specific nature of microcellular operational environments, propagation models are required to take into account the exact position, orientation and electrical properties of individual buildings, and hence, ray tracing techniques have emerged as the dominant methods to predict propagation in such environments. A novel hybrid three-dimensional (3-D) ray tracing algorithm which can evaluate scenarios incorporating many thousands of objects by utilising the concept of "illumination zones," is presented in this paper.In order to evaluate the accuracy of the presented model, comparisons of narrow-band and wide-band predictions with measurements are performed for a variety of scenarios. First, power comparisons show that very accurate predictions can be achieved (rms errors less than 3.7 dB). Then, wide-band analysis shows that since the rms delay spread for systems with finite bandwidth is a function of the multipath phase, only average measured and predicted rms delay spread values can be compared and as a result, limited averaging can produce large rms errors. With sufficient averaging the achieved wide-band accuracy in terms of the predicted rms delay spread, is adequate for most planning purposes.Index Terms-Narrow-band and wide-band radio channel measurements and predictions, propagation modeling, ray tracing.

Abstract-A novel three-dimensional (3-D) ray-tracing model capable of supporting detailed representation of the indoor environment, as well as external building structures, is presented in this paper. The developed algorithm uses a hybrid imaging technique where the two-dimensional (2-D) image generations in vertical and horizontal planes are combined to produce 3-D paths. It also employs the concept of "illumination zones" of the images which greatly simplifies the image map and allows the evaluation of complex indoor scenarios.In order to investigate the accuracy of the presented model, comparisons of predictions with narrow-band and wide-band measurements are performed in line-of-sight (LOS), non-LOS (NLOS), and deep shadow areas, both for co-and cross-polarized antennas. The analysis shows that accurate power predictions can be achieved for both antenna polarizations with rms errors less than 7 dB, even when long sections of the test route are in deep shadow areas. There is a trend agreement between the simulated and measured channel impulse responses, while the rms delay spread in NLOS areas is predicted with less than 5-ns rms error (or better than 13% normalized mean error). The paper provides an insight into the real and the modeled radio channel.Index Terms-Narrow-band and wide-band indoor radio channel measurements and predictions, propagation modeling, ray tracing.

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The cost and complexity of a network is closely related to the number of base-stations (BSs) required to achieve the system operator's service objectives. The location of BSs is not an easy task and there are numerous factors that must be taken into account when deciding the optimum position of BSs. This paper discusses the performance of three different algorithms developed to solve the BS location problem: the greedy algorithm (GR), the genetic algorithm (GA) and the combination algorithm for total optimisation (CAT). These three methods are compared and results are given for a typical test scenario.

Tel: +44 (0) 1 17 954 5 169, Fax: +44 (0)117 954 5206 ABSTRACT This paper investigates the nature of the indoor radio channel at 60GHz, with regard to its use for future high bitrate broadband wireless networks. It is proposed that, for operation in the millimetre-wave indoor channel, directional antennas can be used to mitigate multi-path effects, thus reducing the need for complex equalisation or multi-carrier techniques. An image based, ray-tracing prediction model is used to study the channel Characteristics and to analyse the variation in received power, RMS delay spread and k-factor within a typical operating environment. The performances of different antenna combinations are investigated and narrowbeam, suitably aligned antennas are shown to reduce received delay spread for both LOS and non-LOS locations.The effects of non-optimal antenna alignment are observed, and system outage is determined for certain system design criteria. The results suggest that it will feasible to combat multi-path effects using switched-beam directional antennas.