Improve of the ATDD in Cognitive Radio Wireless Network

The radio spectrum is limited, but in urban and rural areas some bands of radio spectrum are idle in most of the time. Some bands of radio spectrum are occupied occasionally. On the other hand, some bands are excessively used. This paper propsed an adaptive time division Duplex (ATDD) technology to effectively improve the transmission delay in the large range ,such as the rural network in 802.22 network.