Abstruct- We describe novel interleaver and deinterleaver

architectures that support bandwidth efficient memory access for

decoders of turbo-like codes that are used in conjunction with

high order modulations. The presentation focuses on a decoder

for serially concatenated pulse-position modulation (SCPPM),

which is a forward-error-correction code designed by NASA to

support laser communications from Mars at more than 50 megabits-

per-second (Mbps). For 64-ary PPM, the new architectures

effectively triple the fan-in of the interleaver and fan-out of the

deinterleaver, enabling parallelization that doubles the overall

throughput. The techniques described here can be readily modified

for other PPM orders.