Linear precoding and adaptive multi-taper spectrum detector for cognitive radios

In recent years, cognitive radios are regarded as a valid solution to solve the problem of inefficient spectrum utilization. A cognitive radio system which has the ability of spectrum sensing and transmission adjustment is proposed in this paper. An optimal detector applied for Thomson's adaptive multitaper spectrum estimation (AMTSE) is presented. The detector is based on Neyman-Pearson Theorem and it can adjust the detection threshold according to the environment change. The simulation shows that the detection rate can outperform energy detection by 40%. On the other hand, adjusting the transmission parameter is required after spectrum sensing. By knowing the interference channel, block diagonalization is applied for canceling the interference when primary user exists. If the primary user is idle, the secondary user's Tx may can estimate the channel state information (CSI) due to the channel reciprocity. So the extra antennas can be used to antenna selection to improve the secondary user's BER performance. Further, the AMTSE spectral detector is implemented by ASIC and the power consumption of this detector is 30.9 mW at 122 MHz. The core area is 1057 × 1057 jm
²
and total chip area is 1557 × 1557 μm
²
.