Method for Transmission of Synchronization Signal in a Cluster-Tree Structured Wireless Communication System

A signal transmission method in a wireless communication system comprising an access point (AP) that is a main communication device managing the wireless communication system, routers that can have their child devices, and end devices that cannot have their child devices, where the AP and each router may operate as a cluster head (CH), a CH and its child devices form a cluster network, the wireless communication system is formed in a multi-hop cluster-tree structure in which a plurality of the cluster networks are connected to each other in a tree structure, and the CH transmits a synchronization signal at the beginning of each transmission frame so as to transmit and receive a signal by using a periodic transmission frame comprising a synchronization signal transmitting interval, a data signal transmitting interval and an idle interval in which no signal is transmitted, the signal transmission method comprising:

• determining, by the CH, whether a channel scan is required or not based on performance of signal transmission to and from its child devices;
• when it is determined that the channel scan is required, estimating, by the CH, characteristics of interference signal by performing the channel scan in the idle interval and determining whether to use the same channel as being in use to transmit the synchronization signal or not;
• and
• depending on a decision whether the channel scan is required or not and the channel being in use is used or not, repeatedly transmitting, by the CH, the synchronization signal by taking into consideration of the performance of signal transmission to and from its child devices, the estimated characteristics of interference signal, and target transmission performance of the wireless communication system.