oseconds. The cyclic prefix provides a time-domain guard band between symbols to compensate for delay spread in the radio channel. A 4.69-microsecond cyclic prefix allows a delay spread Terrestrial Broadcast/Cellular Network Integration Table 15.4 Broadcast technology comparisons Cellular Broadcast Wide Area Cellular broadcast System DVB-T LTE MBSFN Frequency <30 MHz 100 MHz, 700 MHz Between 700 and 2.6 GHz 220 and 1400 MHz Range 500 km 74 km 67 km 5, 30, (100 km) Channel spacing 9 kHz 1.536 MHz 7.6 MHz 1.4, 3.0, 5, 10, 15, 5 MHz 20 MHz Max gross data rates 25 kbps 2.304 Mbps 5 to 31.7 10 to 30 Mbps or above depending on cell size Modulation 16 QAM 16 QAM 64 QAM 64 QAM Number of subcarriers 1705 k) 300 across 4.5 600 across 6817 (4 k) 4.5 MHz Subcarrier spacing 41.66 Hz 1 kHz 4.46 kHz 15 kHz 7.5 kHz 1.116 kHz Symbol duration in 26 660 133.4 microseconds Guard interval in 7 to 224 33.33 microseconds of 1.5 km; a 33.33 microsecond cyclic prefix allows a delay spread of 10 kilometres. The delay spread is the difference in path length caused by multipath in cellular networks. In SFN broadcast networks, the delay spread is also a function of receiving the same signal from more than one transmitter. The 33-microsecond cyclic prefix used in MBSFN means that TV transmissions can be broadcast simultaneously from multiple node B cellular base stations without causing inter- carrier symbol interference in the receiver. Table 15.4 compares DRM, DAB, DVB broadcast networks with LTE and LTE MBSFN. The number of subcarriers defined for DVB T and LTE excludes edge-of-band subcarriers used to provide a frequency domain guard band. For example the 8 K DVB- T multiplex has 6817 one-kHz subcarriers nestled within 8 MHz (8 k times one kHz) channel spacing. In practice, a number of DVB-T networks were implemented as 2-k rather than 8-k networks due to receiver chip set limitations, for example in the UK where initial implementation was realised in 1997. This prevented the implementation of a (more spectrally efficient) single- frequen