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In this paper, we present a two phase cooperative relaying scheme for spectrum sharing in a 2 × 2 overlay cognitive radio. Secondary transmitter acts as decode and forward relay to the primary and employs hierarchical modulation to enhance primary SNR reception. Primary receiver employs cooperative maximal ratio combining to improve SNR and secondary receiver recovers its own data by successive interference cancellation. We have calculated symbol error rate (SER) analytically for such system and optimal power allocation factor between primary and secondary data in hierarchical modulation have been found out. The analytical result of SER is found close agreement with Monte-Carlo simulation.

This paper proposed the design of quantum cost efficient 4-bit reversible universal shift register(RUSR) using existing reversible logic gates. The proposed design is very useful in quantum computing due to its low quantum cost, less no. of reversible logic gate and low garbage outputs. The quantum cost(QC), garbage output(GO), number of gates are respectively 68, 20 and 16 for proposed work.

The avalanche noise performance of multiple quantum well (MQW) DDR IMPATT devices has been investigated. A self-consistent quantum drift-diffusion (SCDD) model is used for the simulation study. The noise performance of one Si based flat and two Si∼3C-SiC MQW DDRs have been studied in this paper. Results indicate that considerable low noise operation with high power output can be obtained at W-band by using the Si∼3C-SiC MQW DDR structures.

The effect of energy-loss due to electron-electron (e-e) and hole-hole (h-h) collisions on the avalanche noise performance of IMPATT diodes has been studied. Simulations have been carried out on DDR Si IMPATTs operating at 94, 140 and 220 GHz. Simulation results show that the noise measure of the diodes considerably increases due to e-e and h-h interactions within the space charge layer of the device. This is observed to be more influential at higher mm-wave frequencies.