Flexible Rays

This article shows that an efficient implementation of the 3-D GO/UTD propagation model allows planning tools of adjustable accuracy to be developed. The accuracy versus CPU time can be balanced to reach the different degrees of radio channel knowledge required for the different stages of development of wireless systems, from the initial design stage to the final planning tasks for systems deployment. The effective planning of the new communications systems-where broadband systems will predominate and more and more sophisticated diversity techniques and MIMO systems will be used-will require accurate and flexible planning tools which allow detailed knowledge of the channel, considering both its macro and micro structure. In fact, the 3-D GO/UTD propagation model enables not only the exact estimation of the mean power value of an area of interest to be made but also the detailed characterization of the radio channel in local environments. For coverage calculations, mean errors of less than 3 dB can be achieved with reasonable CPU time-less than 1 s per point in the case of a complex model. In addition, by means of ray-tracing, a statistical characterization of the channel can be obtained both in broadband and in narrowband, estimating parameters which are fundamental for the design of various subsystems of interest in wireless systems such as the crossing rate per level and the mean duration of the windings, or the mean square delay and the coherence bandwidth of the channel. Finally, using a realistic case study, it is shown that the deployment of a WLAN in a large- or medium-size building requires detailed radio planning to enable the number and positioning of the APs to be optimized, guaranteeing a minimum quality of service to the users in regard to the coverage, reliability, and capacity of the network.