2.The Methods
(7) Connected transmission

( 1 ) Efficient transmission

・ Connected transmission is defined as a transmission of multiple segments (i.e. multiple programs) from the same transmitter with no guard band.

・ In addition, the channels of independent broadcasters can be transmitted together without guard bands from the same transmitter as long as the frequency and bit synchronisation are kept the same between the channels.

・ But, broadcasters can have their own RF channel in which they can select transmission parameters independently.

・ The following two advantages are available from connected transmission.

１ Facility and maintenance costs are low because only a single broadcasting facility is required.

２ Effective use of the frequency is enabled because no guard band between segments is required.

To operate connected transmission is for the first time in the world.

An example of connected transmission for three TS’s (TS1, TS2, and TS3) is shown in Figure 3. Each TS signal is independently channel-coded. After OFDM-frame adaptation, all segments symbol data are adapted for OFDM-signal generation by single IFFT.

FIGURE ３ Example of connected transmission (three TS’s)

( 2 ) CP carrier in connected transmission

・ In an ordinary transmission, one CP (Continual Pilot) carrier is added to the upper end of the band as shown in Figure 4. This additional CP carrier is used as a reference signal for the coherent demodulation.

FIGURE ４ CP-carrier in an ordinary transmission

・ In connected transmission, on the other hand, the first carrier of the upper adjacent segment can be treated as a CP of the desired segment.

・ Accordingly, only one CP is enough for the connected transmission as shown in Figure 5.

FIGURE ５ CP-carrier in connected transmission

( 3 ) Parameter restrictions in connected transmission

・ The same mode should be applied for all segments. Mode means an identification of transmission mode based on the carrier spacing of OFDM carriers.

・ The same guard interval length must be used for segments. Because all OFDM symbols in connected transmission should be synchronised with each other, modes having different symbol lengths cannot be mixed.