For normal operation of a wireless system and a terminal device, the downlink access signal and the uplink access signal need to be provided respectively. The access signal is an essential signal for the wireless system. In the practical operation of the communication system and the terminal, the access signal needs to be continuously swept and transmitted. In addition to the access signal, other signals, such as reference signals used to measure, maintain, and track synchronization and channel conditions, also need to be swept and transmitted, so a time segment likewise carrying the sweep signal and other signals required to be swept in an access process may be referred as a sweep time interval (STI), and is classified into a DL TX sweep time interval and an UL RX sweep time interval from the perspective of a base station. Correspondingly, the time segment is classified into a DL RX sweep time interval and an UL TX sweep time interval from the perspective of a terminal. A subframe or a time interval for sending a sweep signal is generally used for sending a downlink access signal or an uplink access signal, and thus the subframe or the time interval for sending the sweep signal may also be referred as a subframe or a time interval for sending an access signal. The access signal herein include, but is not limited to, a synchronization signal, a signal in a broadcast channel, a random access signal, a scheduling request signal, and the like. In a real system definition, the time segment is not necessarily named as the STI, but belongs to the category of the STI as long as the time interval is related to the sweep and the access. The DL TX sweep time interval and the DL RX sweep time interval, although are not likely to be coincided in absolute time, are both correlated with a certain segment of a sweep signal transmitted by the base station. Similarly, the UL TX sweep time interval and the UL RX sweep time interval are also correlated. Here, the base station and the terminal are defined in a broad sense. Any possible network device such as a base station, a cell, a micro base station, a pico base station, a relay, a cellular, a transmit-receive point (TRP), a transmit point (TP) or the like belongs to the category of the base station, and any possible user equipment belongs to the category of the terminal.