the entire broadband channel and provides continuous signaling from AT to AN, the access network can easily make broadband measurements required for improved interference and resource management. The result is enhanced robustness of reverse link signaling and continuity of the signaling channel even during transitions such as access and handoffs [4,5]. 6.5.1.2.1 Superframe and OFDM Symbol Structure Similar to Access Network, the transmission on the uplink is divided into superframes but without a preamble. In the FDD mode, each superframe consists of a sequence of 25 uplink PHY frames. The consecutive uplink PHY frames are separated by a guard interval Tg in the FDD mode when FDD- HalfDuplexTDDPartition = 1, whereas there is no separation when FDDHalfDuplexTDDPartition = 0, where, FDDHalfDuplexTDDPartition is a field of the Overhead Messages Protocol. Each superframe has an associated SuperframeIndex that is incremented every superframe. Each of the uplink PHY frames consists of a sequence of OFDM symbols. The index 0 PHY frame consists Inverse Superframe Fourier Overlap- Upconversion Preamble Windowing and-Add Transform Operation Operation Operation Figure 6.7 Channel structure for the single-transmit-antenna case. Reproduced with permission from © 2008 IEEE [4] Next Generation Mobile Communications Ecosystem Reverse Link Reverse Link Reverse Link PHY Frame PHY Frame PHY Frame 16 OFDM 8 OFDM 8 OFDM Symbols Symbols Symbols Figure 6.8 FDD Reverse Link superframe structure if FDDHalfDuplexTDDPartition = 0. Reproduced with permission from C 2008 IEEE [4] of 16 OFDM symbols while each of the remaining PHY frames only has eight OFDM symbols. The structure of an FDD Reverse Link superframe is shown in Figure 6.8 for FDDHalfDuplexTDDParti- tion = 0 and in Figure 6.9 for FDDHalfDuplexTDDPartition An OFDM symbol consists of NFFT individually modulated sub-carriers that carry complex-valued data. Complex-valued data are represented in the form d = (dre, dim), where dre and dim represent the real and imaginary components, r