a method of facilitating a user equipment communicating with a base station via a cell of a mobile communications system is disclosed . the ue selects a random access preamble sequence from a set of random access preamble sequences and transmits the random access preamble sequence to the bs . the bs receives the random access preamble sequence and estimates a time of arrival of the random access preamble sequence . a pre - defined set is used in generating the set of random access preamble sequences via at least one zadoff - chu sequence . the pre - defined set including all of the following values : 0 , 13 , 15 , 18 , 22 , 26 , 32 , 38 , 46 , 59 , 76 , 93 , 119 , 167 , 279 , 419 .