Symbol to sub-carrier interleaver for DVB-T2 wherein the permutation matrix applied to the LFSR bits is varied from OFDM symbol to OFDM symbol

摘要

DVB-T and DVB-H (de)interleave symbols to/from sub-carriers using a pseudo random sequence generated using an LFSR (linear feedback shift register) 200 whose bits are fed through a permutation matrix 210 to generate the read/write address for the interleaver memory. The invention provides improved separation between symbols either by applying an offset to the addresses that changes from symbol to symbol, or by changing the permutation matrix from symbol to symbol. The invention normally uses a rotating sequence of offsets or matrices. The interleaver can also switch between a mode wherein a memory location is written to with the next symbol immediately after the current symbol has been read (Fig. 4), when the number of sub-carriers exceeds half the number of memory locations, and a mode where alternate symbols are each assigned their own memory locations otherwise (Figs. 9 and 10).