The performance of one-bit hard combination decision scheme for cooperative spectrum sensing in cognitive radio has been studied in this paper. Energy detector model is used to observe the presence of primary user signal. Simulation result shows that the probability of missed detection is decreasing for both conventional hard combination and one-bit hard combination with OR rule according to the increasing of probability of false alarm. It also has demonstrated that one-bit hard combination decision scheme exhibits comparable performance with the conventional scheme and thus achieves a good tradeoff between performance and complexity.

A PC based data acquisition was designed and developed using GM detector and a programmable microcontroller 16F876 of PIC family. This unit was calibrated with the standard Canberra Counter. It gave prompt response directly and has low power consumption. It was tested for gamma ray measurement to continuously monitor a radiological resulting from the natural and man-made sources that threat site security and human health. The system was simple to use, required no additional hardware and allows the selection of data. The collected data were easily being exported to a PC via parallel port. A "C" language program was developed to control the function of the entire system, using PCWH compiler.

Spectrum sensing is a challenging task for cognitive radio. Energy detection is one of the popular spectrum sensing technique for cognitive radio. In this paper we analyze the performance of energy detection technique to detect primary user (PU). Simulation results show that the probability of detection increases significantly when signal to noise ratio increases. It is also observed that the detection probability decreases when the bandwidth factor increases.

Orthogonal Frequency Division Multiplexing (OFDM) is an attractive modulation technique for transmitting large amounts of digital data over radio waves. One major disadvantage of OFDM is that the time domain OFDM signal which is a sum of several sinusoids leads to high peak to average power ratio (PAPR) which leads to power inefficiency in RF section of the transmitter and increased complexity in the analog to digital and digital to analog Converter. Selected mapping (SLM) is a well-known method for reducing the PAPR in OFDM. In this paper, we have studied the performance of SLM for Different Number of Subcarriers. Simulation result shows that the PAPR is reduced significantly when the number of phase sequences is increased and PAPR is increased when the number of subcarriers is increased. It also shows that data speed increases when subcarriers increase where N-point IFFT/FFT circuit depends on N-subcarriers.