Effect of variable guard time length on mobile WiMAX system performance

Guard time length (GT) is one of the key OFDMA parameters. It is implemented as cyclic prefix (CP) to completely alleviate intersymbol interference (ISI) and to preserve orthogonality among OFDMA subcarriers as long as the guard time length is sufficiently greater than channel delay spread. In conventional OFDMA systems a fixed GT length is chosen to be much longer to tolerate worst case condition irrespective of current propagation channel state. This technique, however, degrades the overall spectral efficiency as well as consumes transmitter energy proportional to the length of the guard time. This fact motivates the need to vary the guard time length for mobile applications based on channel parameters. The primary goal of this paper is to investigate the effect of varying the GT length based on channel delay spread for mobile WiMAX technology. The overall system performance and resultant packet error rate (PER) are slightly improved as function of the guard time length

Optimization of guard time length for mobile WiMAX system over multipath channel

Guard time length (GT) is one of the key OFDM parameters. It is implemented as Cyclic Prefix (CP) to completely alleviate Intersymbol Interference (ISI) and to preserve orthogonality among OFDM subcarriers as long as the guard time length is sufficiently greater than channel delay spread. Conventional OFDM system uses a large GT length to tolerate worst case channel condition irrespective of its current state. This technique, however, degrades the overall spectral efficiency as well as consumes transmitter energy proportional to the length of the guard time. In this paper, we optimize the guard time length for mobile WiMAX system over ITU-R M.1225 multipath fading channel. The overall system performance and resultant packet error rate (PER) are slightly improved as function of the guard time length

Antenna design using left-handed materials

Smart antenna technologies are emerging as an innovative way to meet the growing demand for more powerful, cost-effective and highly efficient wireless communication systems. In this project, from broad category of smart antenna techniques, the switch beam digital-beamforming technique in the downlink is deployed to improve the fidelity and performance of WiMax application. In this regards, the designed system forms and steer the beam according to the user location which is known to the system. In addition, the system performs sidelobe cancellation base on the chebyshev algorithm to optimize the antenna radiation pattern. The design and implementation steps are as follow: the system is firstly modeled by MATLAB software. After modeling, the algorithm is implemented in DSP by using C and Code Composer Studio. After DSP hardware implementation, the signal management is performed in DSP before transmission to the FPGA board. This management is necessary, in order to make processed signal in DSP suitable for channel separation process in FPGA. FPGA is deployed to split the data stream into sixteen channels corresponding to number of antenna elements. Next, the FPGA and DSP are integrated together to form the baseband switch beam smart antenna system. After integration process, the hardware is tested; the results prove that the system functions properly as we expected from simulation model. In this project, lastly, the initial design of IF, RF-front-end and their necessary circuits are also portrayed to be used in the next smart antenna research project