1. Field of the Invention
This invention relates to cooperative transmission mechanisms in wireless communication techniques, and, more particularly, to a cooperative transmission system and a cooperative transmission method used in multiple access points in a wireless local network.
2. Description of Related Art
Recently, as the wireless communication technique develops rapidly, it is more and more popular that access points (APs) are used to construct a Wi-Fi network, in which each AP forms a basic service set (BSS). In order for users to use wireless Internet services quickly and conveniently, a great amount of Wi-Fi wireless APs are installed. The more the APs are installed, the distance between a user and the AP is shorter and thus the less the path loss of wireless signal energy becomes. As a result, the signal-to-noise ratio (SNR) of signals received by users within basic service sets constructed by the wireless APs is increased, and more people can use the services at the same time. However, too dense deployment of the wireless APs forms overlapped BSSs (OBSS), which results in bandwidth contention and channel interference among the APs. As a result, the throughput performance of the wireless network system reduces. To address the issue, IEEE 802.11ac standard regulates a new multi-user multiple input multiple output (MU-MIMO) transmission technique, which, however, is limited to be applied to a single BSS, and thus cannot solve the problem generated by the OBSSs.
Therefore, a cooperative transmission mechanism for a plurality of APs in a dense Wi-Fi wireless network to solve the problems of channel contention and interference among a plurality of adjacent APs and spectrum resource contention and signal interference among APs in OBSSs is one of the most urgent issues in the art.