A packet switched wireless cellular system with wide area coverage, high throughput and high spectral efficiency is proposed. Smart antennas at both base stations and mobiles improve the antenna gain and improve the signal to interference ratio. The small-scale fading is predicted in both time and frequency and a slotted OFDM radio interface is used, in which time-frequency bins are allocated adaptively to different mobile users, based on their predicted channel quality. This enables efficient scheduling among sectors and users as well as fast adaptive modulation and power control. We here estimate the spectral efficiency of the suggested downlink. The resulting channel capacity grows with the number of simultaneous users and with the number of antenna elements in terminals. A high efficiency, around 4 bits/s/Hz, is attained already for moderate numbers of users and terminal antennas. An outline is given of research pursued within the PCC Wireless IP Project to improve and investigate this type of system.