please mention which kind of blocking.
solution for sd blocking-
1.check weather high blocking site is on lac boundary(paging load+sd load+lac update).
2.check channel configuration weather combined or separated
3.try to change sd slot
4.add one more slot for sd
5.check sd health report(especially in nokia).
for tch blocking
1. if its due to high traffic ,enable half rate amr.
3.check for faulty trx/slots from tch health report