Research On High Gain And Wide Cover Wi-Fi Key Technologies

WiFi(Wireless Fidelity), a wireless network composed of AP(Access Point) and wirelss network card. As wireless network becomes indispensable in our daily life, the demands for better performance of WiFi devices is necessary. Therefore, the study on WiFi technology with the feature of no blindness, long-range cover, high power gain is becoming a hotspot.In this thesis, two key technologies of WiFi, which are adaptive beamforming and MIMO space-time coding are studied in this paper. A novel pre-coding orthogonal full diversity space-time block coding scheme for 4x4 MIMO system and a new adaptive beamforming algorithm with linear constrained minimum variance (LCMV) and multiple signal classification (MUSIC) algorithm are proposed and simulated.Among all the key technologies of the WiFi, we mainly study the adaptive beamforming and MIMO space-time coding. The main work of this paper is .as follows:1) Based on the thorough research on the basic theory of MIMO space-time coding technology and the analysis of the existing space-time coding methods, a new 4x4-transceivertime-space-time coding scheme combined with the precoding module is proposed. To overcome the deficiency of the existing space-time coding. This novel scheme can reach full speed orthogonality, which the orthogonal space-time block codes can not acquire when the number of the antenna is above 2.2) Based on the basic theory of adaptive beamforming of smart antenna and the analysis of the advantages and disadvantages of various adaptive beamforming algorithms, A new adaptive beamforming algorithm combining the Linear Constrained Minimum Variance (LCMV)and Multiple Signal Classification (MUSIC) is proposed to overcome the deficiency of other algorithms. In the phased-array antenna system, this scheme uses multiple-signal classification (MUSIC) adaptive algorithm to evaluate the direction of incoming wave, and Linear Constrained Minimum Variance (LCMV) to control the direction of the main lobe of the antenna in order to track the desired signal. The simulation results show that the scheme has improved the system performance.3) A high-gain, wide-coverage WiFi system is designed based on adaptive beamforming and MIMO techniques. The simulation results show the high gain and wide coverage of the designed WiFi system.