CDMA/TDD cellular systems for the 3rd generation mobile communication

Abstract

We propose CDMA/TDD cellular systems utilizing a base-station-based diversity scheme. A significant reduction in the required Eb/No resulting from the use of a hybrid diversity scheme combining the effects of space diversity and path diversity is shown. Because TDD uses only one radio frequency band and transmission diversity at the base station can be employed, space diversity is unnecessary at the mobile station and thus the mobile station can be made smaller. CDMA/TDD systems can also realize effective transmission power control with only the use of open-loop control. A single antenna and no duplexer are advantageous in CDMA/TDD for terminal size and battery life. This system is especially effective in an environment such as microcellular systems or indoor office systems where the spreading bandwidth is narrower than the coherent bandwidth, and path diversity gain by itself is small.