There are various situations where a receiver or receiving end of a communication system must be synchronized with a received signal or channel in order to provide access to the communication system. One example is the cell search procedure in cellular systems. According to proposal R1-061651 for the 3rd Generation Partnership Project (3GPP) specification TR25.814, v.1.5.0, cell search is the first step for a terminal device (or user equipment (UE) in 3G terminology) to acquire the enhanced universal territory radio access (EUTRA) system with very limited prior information. This procedure includes detecting a synchronization channel (SCH) position, detecting a cell identity (ID), and reading a broadcast channel (BCH). Information a UE could use in this procedure comprise centre frequency (an operator related value which may be pre-stored in the UE), an SCH bandwidth (e.g. central 1.25 MHz regardless of the operating system bandwidth), part of the SCH sequence information, like repetition times, sequence formats and so on.
Besides other problems faced during synchronization, time division duplex (TDD) systems in which different periodic time periods or time slots are allocated to uplink (UL) and downlink (DL) channels will have additional problems due to their TDD nature. One of these problems is that there could be strong UE-to-UE interference between closely located UEs. As an example, such an UE-to-UE interferences may occur when one UE is doing cell search while the other UE is transmitting.
FIG. 2 shows a situation where a second UE (UE2) starts to search a cell when a close-by first UE (UE1) is transmitting data. Such kind of situations are quite usual in a real networks. The results of UE-to-UE interference could be that the interfered second UE (UE2) cannot detect the network just because there is strong interference in the UL period or slot of the whole frame of a broadcast signal received from a base station (BS) or other access device.