A method of operating a user equipment, UE , in a wireless communication system, the method comprising: receiving a narrowband primary synchronization signal, NPSS, based on a first Zadoff-Chu sequence, and a narrowband secondary synchronization signal, NSSS, based on a second Zadoff-Chu sequence; receiving an additional NPSS and an additional NSSS, wherein the additional NPSS is generated by changing at least one of a root index or a cover code applied to the first Zadoff-Chu sequence, and the additional NSSS is generated by changing at least one of a parameter, a binary sequence, or a resource mapping method applied to the second Zadoff-Chu sequence; and based on information indicated by at least one of the additional NPSS or the additional NSSS, performing at least one of cell search, acquisition of information about whether paging is transmitted and system information has been updated, or information about a duplex mode applied to the wireless communication system, wherein, based on the additional NPSS and the additional NSSS used for indicating whether paging is transmitted and system information has been updated: the additional NSSS is repeatedly transmitted in M consecutive subframes after the additional NPSS is repeatedly transmitted in N consecutive subframes, the additional NPSS is transmitted by applying a different cover codes per subframe, the additional NSSS is transmitted by applying at least one of a different cover code per subframe or a different resource mapping method per subframe, the M consecutive subframes are non-overlapped with the N consecutive subframes, and N and M are natural numbers equal to or larger than 1. receiving a narrowband primary synchronization signal, NPSS, based on a first Zadoff-Chu sequence, and a narrowband secondary synchronization signal, NSSS, based on a second Zadoff-Chu sequence; receiving an additional NPSS and an additional NSSS, wherein the additional NPSS is generated by changing at least one of a root index or a cover code applied to the first Zadoff-Chu sequence, and the additional NSSS is generated by changing at least one of a parameter, a binary sequence, or a resource mapping method applied to the second Zadoff-Chu sequence; and based on information indicated by at least one of the additional NPSS or the additional NSSS, performing at least one of cell search, acquisition of information about whether paging is transmitted and system information has been updated, or information about a duplex mode applied to the wireless communication system, wherein, based on the additional NPSS and the additional NSSS used for indicating whether paging is transmitted and system information has been updated: the additional NSSS is repeatedly transmitted in M consecutive subframes after the additional NPSS is repeatedly transmitted in N consecutive subframes, the additional NPSS is transmitted by applying a different cover codes per subframe, the additional NSSS is transmitted by applying at least one of a different cover code per subframe or a different resource mapping method per subframe, the M consecutive subframes are non-overlapped with the N consecutive subframes, and N and M are natural numbers equal to or larger than 1. the additional NSSS is repeatedly transmitted in M consecutive subframes after the additional NPSS is repeatedly transmitted in N consecutive subframes, the additional NPSS is transmitted by applying a different cover codes per subframe, the additional NSSS is transmitted by applying at least one of a different cover code per subframe or a different resource mapping method per subframe, the M consecutive subframes are non-overlapped with the N consecutive subframes, and N and M are natural numbers equal to or larger than 1. <EOS>