IST-2003-507581 WINNER D2.5 v1.0 Duplex ... - Celtic-Plus

WINNER D2.5 v1.02.5.4 Pure TDDTDD based equipment does not need any duplex filters and users are separated in the time domain, seeFigure 2-10. Furthermore, from a link perspective, there is a possibility to change the allocation of ULand DL resources flexibly by changing the location of the switching point within the frame. However, asobserved with reference to Figure 2-4, this might cause severe AP-AP or MT-MT interference if theneighboring cells or TDD systems in adjacent carriers have a different UL/DL configuration (see Section5).frequencyAPTRMT2MT3R T R TtimeFigure 2-10: Overview of TDD2.5.5 DL and UL oriented HybridIn this case, the base station may be seen as operating in FDD but capable to transmit/receive in theuplink/downlink channel as well to cope with traffic asymmetries. Obviously, the use of an uplinkchannel for downlink transmission and vice versa leads to the same interference situations as in a TDDsystem, see Figure 2-11.frequencyDLDuplexdistanceULDLtimeFigure 2-11: Overview of a DL oriented Hybrid TDD/FDD system from a spectrum perspectiveWhereas the access points get more complex, the terminals need not be more complex than inconventional TDD or FDD systems. From the mobile terminal point of view, the following basicduplexing variants are applicable:a) Only (T+F)DDb) Only TDD + FDDc) Mixed (T+F)DD and TDD+FDD.Again Figure 2-12 shows a specific example for the mixed mode case. Here, MT1 communicates in FDDmode and MT3 in (T+F)DD mode. Since MT2 is only receiving data in this example, it could be either a(TDD+FDD) terminal or a (T+F)DD terminal.Page 26 (121)