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The prevailing condition of forthcoming cognitive radio networks will be the existence of primary user and other unknown secondary users in a same band of interest. Thus to accommodate such situation, a combined spectrum sensing scheme is proposed which utilizes waveform detector(WD) and energy detector(ED) based on the available signal pattern of Primary User(PU) waveform. By not activating the second...
Secondary User (SU) has a responsibility to seek opportunities of spectrum access through spectrum sensing continuously. Spectrum sensing is a main task in Cognitive Radio (CR) that must be performed to avoid collision with Primary User (PU) and having seamlessly data transmission via license channel. To achieve sensing outcome correctly with tolerable error rate, SU requires sufficient time for sensing...
The required time for spectrum sensing is critical issue in cognitive radio (CR). Secondary User (SU) must sense license spectrum to seek opportunities as quick as possible. However, quick sensing decreases the fidelity of sensing outcome. Sensing time has a significant impact to the throughput performance. This paper studies the impact of sensing time to the throughput performance at low signal to...
Prior to access license channel, secondary user (SU) is supposed to sense available channel to confirm that channel spectrum is unoccupied by primary user (PU) in cognitive radio (CR). Secondary user necessarily performs spectrum sensing at a certain time. Longer time allocation for spectrum sensing is expected can increase the fidelity of sensing outcome that leads to improve detection performance...
Energy Detection is a popular technique to detect primary user (PU) in cognitive radio (CR) compared with others. Due to less complexity and easier to be implemented makes energy detector (ED) is a common technique in use for signal detection. This paper studies detection performance of primary signal under Additive White Gaussian Noise (AWGN) with low signal to noise ratio (SNR). The performance...
The current policies of spectrum allocation leads to inefficient use of spectrum, making it scarce but the truth is, spectrum is not scarce but is underutilized. In today's era dynamic spectrum access is the need of the hour and cognitive radio is a novel technology which improves spectrum utilization. In this paper overview of cognitive radio along with spectrum sensing techniques is taken into account...
Cognitive radio will drive the future of wireless/radio communication by efficient utilization of underutilized spectrum (vacant space). Spectrum sensing and primary user detection is the main challenge in cognitive radio systems. Energy based sensing is a common spectrum sensing method for cognitive radio since the information about the licensed user signal are not required for the detection process...
In this chapter we discussed various spectrum sensing aspects and issues related to TV white space. Special attention has been paid to ongoing TV white space standards i.e. IEEE 802.22 and the IEEE 802.11af. These standards were studied based on their ability to detect primary user (PU) or TV incumbent users and coexistence with other's signals and to avoid transmission in the busy and adjacent channels...
It is inevitable for cognitive radio to find unutilized portion of the spectrum more accurately for successful deployment of dynamic spectrum sensing. To achieve highly reliable spectrum sensing, usually cooperative spectrum sensing is employed but still there is a margin to improve local sensing decisions. Cooperative spectrum sensing improves reliability of sensing at the cost of cooperation overhead...
In this paper, performance of cooperative spectrum sensing with an improved energy detector is discussed. The Cognitive radios (CRs) utilize an improved energy detector for taking a decision of the presence of the primary user (PU). The improved energy detector uses an arbitrary positive power p of the amplitude of the received samples of the primary user's signals. The decision of each CR is orthogonally...
In order to quantify the impact of channel and/or diversity scheme on the probability of mission detection, a concept of sensing gain was defined recently by us, very similar to diversity gain, which determines the slope of probability of missing detection versus average signal-to-noise ratio (SNR) curve. The sensing gain is an important performance target, and very useful in the performance analysis...
In cognitive radio networks, secondary user (SU) does not have rights to transmit when the primary user (PU) band is occupied, that's why a sensing technique must be done. Recently, a new blind spectrum sensing technique based on distribution analysis was developed for sensing the spectrum holes in the PU band. Specifically, assuming that the noise of the radio spectrum band can still be adequately...
Limited available spectrum and the inefficiency in the spectrum usage necessitate the use of cognitive radio (CR) approach to exploit the existing wireless spectrum opportunistically. To achieve the goal of CR, it is a fundamental requirement that the cognitive user (CU) performs spectrum sensing to detect the presence of the primary user (PU) signal before a spectrum is accessed to avoid interference...
This paper addresses the problem of collaborative spectrum sensing using sequential detection (SD) in cognitive radios. The goal of sequential processing is to reduce the delay and amount of data needed in identifying underutilized spectrum. Each secondary user (SU) employs a simple and computationally efficient autocorrelation-based detector for orthogonal frequency division multiplexing (OFDM) signals...
Cognitive radio systems offer the opportunity to improve spectrum utilization by detecting unused spectrum bands while avoiding the interference to primary users. In this paper, we propose a new algorithm for spectrum sensing, which is energy detector using both adaptive and fixed threshold, in order to compensate the weak points of the existing energy detector in the distorted communication channel...
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