 is flexible and has many transmission modes, 4.98-31.67 Mbps at C/N = 25 dB. The COFDM multicarrier modulation with 2k and 8k modes is applied and in the countries where the phase-alternating line (PAL) standard is adopted (e.g. Europe), the bandwidth of one DVB channel is ~8MHz. Some parameters characteristics are: 1705 subcarriers (spacing, 4464 Hz) for the 2k mode; 6817 subcarriers (spacing, 1116 Hz) for the 8k mode; carrier modulation: QPSK, 16-QAM or 64-QAM; error correction: convolution code and Reed-Solomon encoder. A classic example mode can be: 64-QAM, code rate = 2/3, guard interval 1/8, which gives a 22.12 Mbps capacity when C/N = 19.2dB with an 8 MHz channel bandwidth. DVB-T includes hierarchical modes where two transport streams can be sent simultaneously with low and high priorities. DVB-T can also be used for broadcasting to mobile devices, altough a suitable mode has to be selected: 8k 64-QAM: < 50 km/h; 2k QPSK: > 400 km/h tolerable. Neverthless, a separate network for DVB-H is desired in order to achieve optimisation of speed, coverage and capacity. DVB-H Introduction Transport Stream Inner coder Transport Solomon Receiver encoder and Interleaver module Scramble Modulation Precorrector Hierarchical IFFT (2k or 8k) and D/A Multiplexer converter and guard converter interval Transport Inner coder Transport Stream Solomon Receiver encoder and Interleaver module Scramble Figure C.1 Hierarchical encoding Hierarchical Encoding Three possible constellation offsets, a = 1, and 4, are defined, but the principle is the same. Two transport streams are fed into the modulator; one of the transport stream controls which is the quadrant where the constellation is placed (high priority stream) and the other defines the 16-QAM signal (low priority stream). The benefit of hierarchical encoding (see Figure C.1) is that the system allows one programme for a mobile or portable application together with a service supporting typically three programmes to be picked up in a stationary application. SFN operation represen