smit Diversity Closed loop transmit diversity is described in [5]. bo b1 b2 b3 Antenna 1 bo b1 b2 Antenna 2 Channel bits STTD encoded channel bits for antenna 1 and antenna 2. Figure 4.15 The STTD encoder - block - diagram example. 4.3.8 Dedicated Downlink Physical Channels The only Downlink Dedicated Physical Channel (downlink DPCH) transmits dedicated data generated at Layer 2 and above, i.e. the dedicated transport channel (DCH), in time-multiplex with control information generated at Layer 1 (known pilot bits, TPC commands, and an optional TFCI). The downlink DPCH is therefore a time multiplex of a downlink DPDCH and a downlink DPCCH. Figure 4.16 illustrates the downlink DPCH frame structure, where each frame has 10 ms length split into 15 slots with Tslot = 2560 chips length, corresponding to one power- control period. As in earlier frame structures, the parameter k in Figure 4.16 determines the total number of bits per downlink DPCH slot. It is related to the spreading factor SF of the physical channel as SF = 512/2k. The spreading factor may thus range from 512 down to 4. DPDCH DPCCH DPDCH DPCCH Data 1 Data2 Pilot Ndatal bits NTPC bits NTECI bits Ndata2 bits Npilot Tslot : 2560 chips, 10*2k bits (k=0..7) Slot #0 Slot #1 Slot #i Slot #14 One radio frame, T = 10 ms Figure 4.16 Downlink DPCH frame structure. The UMTS Network and Radio Access Technology Appendix-A defines the exact number of bits of the different downlink DPCH fields, i.e. Npilot NTPC, NTFCI, Ndatal and Ndata2. Upper layers configure and reconfigure the slot format usage. The two basic types of downlink DPCH reflected in Appendix A, are the ones that con- tain TFCI (e.g. various simultaneous services) and those that do not contain TFCI (e.g. fixed-rate services). While support of downlink TFCI inclusion in the network may be optional, it is mandatory in all UEs. The UTRAN determines if a TFCI should be transmitted or not. 4.3.8.1 The Compressed Mode There are two compressed slot formats, i.e. A and B. Format B is possible by the spread- ing fa