The problem of meeting the proliferating demands for mobile telephony within the confinements of the limited radio spectrum allocated to these services is addressed. A multiple beam adaptive basestation antenna is proposed as a major system component in an attempt to solve this problem. This novel approach is demonstrated here by employing an antenna array capable of resolving the angular distribution of the mobile users as seen at the hase-station site, and then using this information to direct beams toward either lone mobiles, or groupings of mobiles, for both transmit and receive modes of operation. The energy associated with each mobile is thus confined within the addressed volume, greatly reducing the amount of co-channel interference experienced from and by neighboring co-channel cells. In order to ascertain the benefits of such an antenna, a theoretical approach is adopted which models the conventional and proposed antenna systems in a typical mobile radio environment. For a given performance criterion, this indicates that a significant increase in the spectral efficiency, or capacity, of the network is obtainable with the proposed adaptive base-station antenna.

This paper addresses the problem of meeting the proliferating demands for mobile telephony within the confinements of the limited radio spectrum allocated to these services. A multiple beam adaptive base-station antenna is proposed as a major system component in an attempt to solve this problem. This novel approach is demonstrated here by employing an antenna array to resolve the angular distribution of the mobile users as seen at the base-station site, and then using this information to direct beams towards the mobiles in both transmit and receive modes. The energy associated with each mobile is thus confined within the addressed volume, greatly reducing the amount of co-channel interference experienced from and by neighbouring co-channel cells. For a given performance criterion, this results in an increase in the spectral efficiency or capacity of the network.

Recent work at Bristol has considered the application of adaptive antenna technology to a mixed cell architecture employing DS-CDMA as the air interface. In the scenario considered, both the Umbrella cells and the underlying Micro cells operate within the same RF bandwidth in an attempt to support a seamless handover between different cell t Y Pes. This paper will present an overview of the proposed mixed cell architecture employing adaptive antenna technology at the Umbrella cell site, as well as the benefits that can be obtained from such a deployment. This will be expressed in terms of the critical near-far problem and the system's capacity. Simulation and propagation results provide evidence for the claimed capabilities of the proposed system and estimates of the likely increased spectrum efficiency.

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This paper considers the performance of a DS-CDMA system which employs adaptive antenna technology at the basestation site of a microcell. By utilising the capability of ray-tracing to provide the complex channel impulse response, a new ray-based simulation methodology for an adaptive antenna in a DS-CDMA system is presented. Results for a typical microcellular environment highlight the behaviour of the adaptive antenna. Finally, with the help of a Monte-Carlo type DS-CDMA capacity analysis, the potential performance enhancement and the sensitivity of the system upon the misspointing of the main beam, are evaluated.