tailieunhanh - WIMAX, New Developments 2011 Part 9

Tham khảo tài liệu 'wimax, new developments 2011 part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Smart Antenna Systems for WiMAX Radio Technology 209 PC interface which exploits a variety of algorithms to estimate the bearings of users and interference sources. The algorithms are implemented in MATLAB and vary from spectralbased Bartlett Bartlett 1950 and Capon Capon 1969 to subspace-based Multiple SIgnal Classification MUSIC Schmidt 1986 . The next step consists of calculating the appropriate weights necessary to form a beam toward the wanted users and null the directions from which interference signals are originating from. The beamforming and nullsteering are achieved by translating the calculated weights into phase and magnitude settings which are sent to another DAQ card to the CPLD. The beamforming algorithms used are based on cophasal excitation and nullsteering. The WiMAX incoming or outgoing signals are fed to the beamforming board and become subject to spatial multiplexing. In DOA estimation the MUSIC algorithm was implemented to determine the bearing of the impinging signals. A detailed simulation study of different DOA estimation algorithms have been carried out showing that MUSIC offers the best resolution but is computationally expensive. An alternative algorithm namely the spatial-selective MUSIC Khallaayoun 2007 has been developed that use greatly reduces the computational cost while not affecting the resolution. By splitting the space into sections using a switched beam method computationally inexpensive and by using the symmetric property of the array one can reduce the number of element needed in performing DOA estimation. The PC interface is used to process the incoming signals after acquisition in order to determine DOA second it is used to beamform towards the users and null the interferences in addition to tracking mobile users Panique 2008 . LabVIEW is used to control all the instrumentation and hardware. A snapshot of the PC interface front panel is shown in Figure 4. The interface GUI contains the needed inputs needed to run the .