APPLICATION OF ANTENNA-ARRAYS TO MOBILE COMMUNICATIONS .2. BEAM-FORMING AND DIRECTION-OF-ARRIVAL CONSIDERATIONS

Array processing involves manipulation of signals induced on various a ntenna elements. Its capabilities of steering nulls to reduce cochanne l interferences and pointing independent beams toward various mobiles, as well as its ability to provide estimates of directions of radiatin g sources, make it attractive to a mobile communications system design er. Array processing is expected to play an important role in fulfilli ng the increased demands of various mobile communications services. Pa rt I of this paper showed how an array could be utilized in different configurations to improve the performance of mobile communications sys tems, with references to various studies where feasibility of an array system for mobile communications is considered. This paper provides a comprehensive and detailed treatment of different beam-forming scheme s, adaptive algorithms tl? adjust the required weighting on antennas, direction-of-arrival estimation methods-including their performance co mparison-and effects of errors on the performance of an array system, as well as schemes to alleviate them. This paper brings together almos t all aspects of array signal processing. It is presented at a level a ppropriate to nonexperts in the field and contains a large reference l ist to probe further.