controls whether ra transmission is orthogonal to shared data transmission or not rach format and associated parameters the rach burst in lte contains a cyclic prefix the rach preamble and a guard interval the cyclic prefix is in the beginning of the rach burst and is a copy of the last part of the rach preamble the cyclic prefix enables efficient frequency domain processing of the rach burst in the enode b rach receiver the guard interval accounts for the unknown round trip delay in the cell both cyclic prefix and guard interval must be larger then the maximum round trip delay to ensure proper operation 1 standard format 1 ms the preamble part of the rach burst is not repeated the cyclic prefix and guard period are balanced and enable cell sizes of approximately 15 km only considering round trip delay not link budget 2 format with extended cyclic prefix 2 ms this format provides extended cyclic prefix and guard periods but no repetition of the preamble the cyclic prefix and guard period are balanced and enable cell sizes of approximately 80 to 90 km only considering round trip delay not link budget 3 repeated preamble format the preamble is repeated to enable a higher received energy.