Symbol interleaver which checks read and write address validity against variable number of sub-carriers for DVB/cable

摘要

The DVB-T2 standard has several operating modes which have different numbers (0.5-32k approx) of sub-carriers in the OFDM symbols, and systems can switch between modes. The systems interleave symbols on to sub-carriers and in order to minimise memory requirements operate a system wherein symbols for one time period are written into the memory locations where a symbol for the previous time period has just been read. Therefore symbols alternate between being written sequentially and then read out in a pseudo random order, and being written in the pseudo random order and read sequentiallys8. When systems switch modes the quantity of sub-carriers and therefore the use of the interleaver memory changes. The invention checks memory addresses generated against the mode of both the symbol being read outs10/12and the symbol being written ins22/24and only performs the read/write operation at the address if it is valid for the symbol mode. The system is also applicable to cable TV installations.