They are usually used as a provision for rate stuffing in order to avoid the bottleneck of insufficient resources. Usually transport packets have to be declared in the PSI information tables. A NULL packet is a particular undeclared transport packet that belongs to nobody. Its payload is undefined. Some applications use NULL packets in order to insure a good and quick synchronization mechanism, as their modulation scheme is not aligned on the start of transport packets.
They are usually used as a provision for rate stuffing in order to avoid the bottleneck of insufficient resource. Usually transport packets have to be declared in the PSI information tables. A NULL packet is a particular undeclared transport packet that belongs to nobody. Its payload is undefined. Some applications use NULL packets in order to insure a good and quick synchronisation mechanism, as their modulation scheme is not aligned on the start of transport packets.