Mr. Amol Dambhare Prof. Bhavna Ambudkar
M.E.(E&TC) (E&TC Dept)
Pune, India Pune, India
For spectrum sensing, primarily three signal processing techniques are designed i.e. Matched filter Energy Detection and Cyclo-stationary feature detection technique. Matched filtering is best. However it requires detailed knowledge of primary signaling. But when no knowledge about the primary user signal is assumed, an Energy Detector is most favorable. Also IEEE 802.22 will provide for spectrum sensing via energy detection. . In this paper we are dealing with different types of sensing techniques (1) energy-based sensing, (2) cyclo stationary feature-based sensing, (3) matched filter-based sensing (4) cooperative sensing.
Spectrum sensing, threshold, PCA technique, bandwidth
Spectrum sensing is a radio process for determining whether a signal is present across a specified RF bandwidth. This process has many applications and usages, including dynamic spectrum access networks, which are designed to maximize spectrum efficiency and capacity within congested wireless transmission environments. Dynamic spectrum access temporarily exploits spectral white spaces in order to transmit data. What this means is that if a licensed primary user is allocated a predetermined frequency to function on, an unlicensed secondary user can temporarily “borrow” the unoccupied spectrum for transmission. In a system consisting of many primary users and secondary users, the secondary users need to be able to jump into and utilize the unused spectrum of the primary users as it becomes available. In order to achieve this action, spectrum sensing techniques are engaged to avoid spectral collisions.
Spectrum Sensing With Energy Detection
The energy based spectrum sensing and detection is the simplest method for detecting primary users in the environment in easily. The energy detector is computationally efficient and could also be used conveniently with analog and digital signals that are at the RF/IF stages or at the base band. It also has a well-known drawback in the detection performance when the noise variance is unknown to the sensing node. When the signal-to-noise ratio is very low, it would be hard distinguish between the radio signal and noise signal, therefore the knowledge of the noise power can be used to improve the detection performance of the energy In energy-based detectors, the energy-metric of the received signal is determine for a given time period T, or consistently over N samples in the discrete domain, and is used as the test statistic for the detection, where T = NTs and Ts is the signal sampling period. It can be shown that the energy detector is optimum when s(t) is zero mean complex Gaussian.
Volume -01, Issue -05 , December 2013.