Improvement for the B-CDMA PCS links in an urban environment by using a directional antenna at the mobile terminal

Since the early days of mobile communications researchers have attempted to improve the link performance by using directional antennas. Previous research focused on the cell site antennas, for the following reasons: (1) It makes economical sense to improve the cell antenna that supports a multitude of users. (2) Knowledge of the direction of arrival (DOA) of the signal at the mobile is necessary to facilitate an effective use of a directional antenna. (3) A relatively large antenna (20 cm by 20 cm) is required for an efficient directional antenna (at 800 MHz). That size is not suitable for mobile or portable terminals.;Moreover, researchers that tried to use highly directional antennas for the mobiles reported only a marginal improvement. That created a myth that only an omni-directional antenna can be used at the mobile.;Increased demand for more efficient use of the spectrum, requires an innovative fresh look at this old problem. Current technology makes it possible to have more processing power in the mobile terminal at reasonable size and cost. Allocation of higher frequencies for personal communication (1.9 GHz), enables the use of a compact, yet a highly directional antenna.;Attempting to increase system capacity, proposals have been made to build an urban infrastructure of smaller cells. The low cost low power transmitters will be installed on utility polls, and will have a limited range. This microcellular (urban) environment has not been investigated until recently.;This research is focused on the improvement of the B-CDMA links in an urban microcellular environment, by using a directional antenna at the mobile terminal. First, I present a model for the distribution of the directions of arrival of the signal. The model shows that signals arrive from distinct directions. Thus having an adaptive system that directs the mobile antenna will improve the received signal. A direction finding technique is presented and analyzed. Field measurements have verified the validity of the model, and proved the advantage of the directional antenna for the mobile.