A review of time division duplex-CDMA techniques

The basic concepts of a time division duplex system are introduced. The advantages of using TDD-CDMA for mobile radio communications is shown to be related to its ability to handle asymmetric data and benefits resulting from the reciprocal nature of the channel. Synchronisation difficulties and the associated interference problems are seen as the primary limiting factors. The use of TDD-CDMA in UMTS is highlighted and the proposal for sharing FDD bandwidth allocations with the TDD system is explained and outage problems are identified.