Patent ID: 9661663
Date: 2017-05-23
CPC Classifications: H04B,H04L,H04W

Claim:
1. A method performed by a user equipment (UE) to access a communications network, wherein the UE is associated with a coverage class from a set of two or more coverage classes, each coverage class being associated with transmission of a different number of repetitions of a random access preamble sequence for performing network access, the set of two or more coverage classes sharing a frequency band for performing network access, the method comprising: generating a Single-Carrier Frequency-Division Multiple Access (SC-FDMA) random access preamble signal comprising two or more consecutive preamble symbol groups, each preamble symbol group comprising a cyclic prefix portion and a plurality of symbols occupying a single subcarrier of the SC-FDMA random access preamble signal, wherein the single subcarrier for at least one of the preamble symbol groups corresponds to a first subcarrier frequency and the single subcarrier for an immediately subsequent one of the preamble symbol groups corresponds to a second subcarrier frequency; determining a starting opportunity, at which the user equipment is to transmit the random access preamble signal, that avoids collision of the random access preamble signal with any other random access preamble signal transmitted by another user equipment associated with a different coverage class, by checking whether one or more possible starting opportunities related to the coverage class with which the user equipment is associated collide with one or more possible starting opportunities related to at least one higher coverage class and backing off from any possible starting opportunities that collide according to the checking, wherein the at least one higher coverage class is associated with a greater number of repetitions of a random access preamble sequence than the number of repetitions associated with the coverage class of the user equipment; and initiating network access by transmitting the random access preamble signal at the determined starting opportunity and in the shared frequency band.