Performance of an adaptive successive serial-parallel CDMA cancellation scheme in flat Rayleigh fading channels

The performance of a successive concatenated cancellation scheme for code-division multiple-access (CDMA) uplink transmission in cellular mobile radio is presented. Both serial and parallel cancellation stages are employed. The serial cancellation stage is first used to obtain initial data estimates followed by the parallel cancellation stages to enhance the accuracy of the estimates. The performance of this scheme is evaluated via analysis and simulation. In our analysis, we develop a model to consider the impact of wrongly estimating the phase and amplitude of the channel impulse response on the successive concatenated cancellation scheme. Analysis and simulation results in flat Rayleigh fading asynchronous channels with both perfect and nonperfect channel estimation and with perfect ranking confirms the accuracy of our analytical model as well as the significant improvement in performance compared to the conventional single-user matched filter (MF) detection and the stand-alone parallel cancellation schemes. Analytical results also show that the concatenated scheme has the potential to reach the single-user performance bound for a wide range of user base size, up to K = 120 users, with a processing gain of 127 using one serial and three parallel cancellation stages. Finally, we propose a method whereby the receiver adapts with the number of users in order to retain the bit error ratio (BER) performance while decreasing the processing delay

A STUDY OF DOUBLE-LAYERED WALL AND PRISM DEFLECTOR TO IMPROVE NATURAL VENTILATION IN A CONFINED SPACE

Natural ventilating and cooling strategies need to be considered as a substitute to the present  air conditioning system. However, the effectiveness of the natural air ventilation in providing cooler environment still needs further investigation. This study proposed a new method, using a double-layered wall and a prism deflector to improve air ventilation in a confined space. Experimental and simulation approaches were used in this study. The results yielded that  the double-layered wall and prism deflector configuration can be used to improve air ventilation in the confined space. The significant effect of the prism deflector was dependent on the combination of parameters used. The use of a 45° hole angle inner wall, and a higher prism deflector ratio were able to enhance the air ventilation more effectively