Multi-Carrier and Spread Spectrum Systems: From OFDM and MC ...

292 ApplicationsDVB-RCT channel bandwidth1k mode2k modeGuard band91Unused sub-carriers168Unused sub-carriersDC carrier(not used)Guard band91Unused sub-carriers168Unused sub-carriersFigure 5-54DVB-RCT channel organization for the 1 k and 2 k modeTable 5-52Sub-carrier organization for the 1 k and 2 k modeParameters 1 k mode structure 2 k mode structureNumber of FFT points 1024 2048Overall usable sub-carriers 842 1712Overall used sub-carriers– with burst structures 1 and 2 840 1708– with burst structure 3 841 1711Lower and upper channel guard band 91 sub-carriers 168 sub-carriers5.6.3.2 Time and Frequency FramesDepending on the transmission mode in operation, the total number of allocated subcarriersfor uplink data transmission is 1024 carriers (1 k mode) or 2048 carriers (2 kmode) (see Figure 5-54). Table 5-52 shows the main parameters.Two types of transmission frames (TFs) are defined:– TF1. The first frame type consists of a set of OFDM symbols, which contains severaldata sub-channels, a null symbol, and a series of synchronization/ranging symbols.– TF2. The second frame type is made up of a set of general purpose OFDM symbols,which contains either data or synchronization/ranging sub-channels.Furthermore, three different burst structures are specified as follows:– Burst structure 1 uses one unique sub-carrier to carry the total data burst over time,with an optional frequency hopping law applied within the duration of the burst.– Burst structure 2 uses four sub-carriers simultaneously, each carrying a quarter ofthe total data burst over time.– Burst structure 3 uses 29 sub-carriers simultaneously, each carrying 1/29 of the totaldata burst over time.These three burst structures provide a pilot aided modulation scheme to allow coherentdetection in the base station. The defined pilot insertion ratio is approximately 1/6,