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In cognitive radio networks, secondary users need to conduct spectrum sensing to properly detect the presence of primary signals that may have much lower power than noise plus interference power. In such a case, time-varying noise plus interference, which is briefly called noise uncertainty in this paper, can substantially degrade the sensing reliability of hard information combining (HIC) and soft...
An adaptive power control scheme for cognitive radio system (CRS) in Rayleigh fading channel is proposed. The transmit power of a secondary user (SU) is adjusted in Rayleigh fading to maximize the constant output signal-to-noise ratio (SNR) at an SU receiver while keeping the interference to a primary user (PU) under given constraints. To calculate the maximum constant output SNR at the SU receiver...
In this paper we investigate spectrum sensing for cognitive radio (CR) by using multiple spectrum sensors. We explore sensing schemes based on soft information combining, hard information combining and a two-stage detection scheme that uses both soft information combining and hard information combining. The two-stage detection scheme is shown to provide improved performance compared to sensing based...
AbstraAbThis study addresses detection of primary users (PUs) for cognitive radio system (CRS) with distributed spectrum sensors (DSSs) in Rayleigh fading environment. Two sensing schemes using DSSs that employ energy detection (ED) are investigated as cooperative sensing and collaborative sensing. For the cooperative sensing, each DSS makes hard decision after sensing and transmits the information...
Cognitive radio(CR) has become an enabling technology to realize dynamic spectrum access through its spectrum sensing and reconfigurable capability. Robust and reliable spectrum sensing is needed to discover spectrum opportunity. Single cognitive radios often fail to provide such reliable information due to their inherent sensitivity limitation. Primary signals that are subject to detection by cognitive...
This paper introduces two cognitive radio (CR) systems: (a) heterogeneous type CR and (b) spectrum sharing type CR regarding its definition, usage model, fundamental system architecture, and developed prototype.
The function of a cognitive radio system (CRS) can be classified as cognitive engine (CE) and sensing. The CE fulfills spectrum analysis and decision making of spectrum access. The sensing function is realized by either a CR node or distributed spectrum sensors. In this paper, we propose a sensing architecture, which adds new functional entities, sensing controller (SC) and sensing information processor...
Recent studies on spectrum sensing for cognitive radio (CR) reveal that sensing based on single CR may not provide reliable information due to the fact that signals degrade as a result of fading and shadowing. Hence, spectrum sensing based on multiple CR has been considered. In this paper we investigate a distributed sensing based on multiple spectrum sensors where the sensors are located outside...
Non-coherent UWB receivers provide robustness against multi path fading at low complexity. The analog front-end of these receivers, however, is susceptible to narrowband interference (NBI), thus requiring NBI mitigation capability. NBI identification and NBI parameter estimation is the first step towards implementing effective NBI mitigation. We propose an NBI detection and its center frequency identification...
One of the unique feature of cognitive radio systems is they can make use of temporarily idle spectral bands in an opportunistic manner. To achieve this however, robust sensing algorithm is required which otherwise incumbent services could suffer from interference. In this paper sensing algorithms based on energy detection and self-correlation detection are presented and compared. The self-correlation...
Non-coherent UWB receivers are cost-effective and robust against multipath propagation. However the analog-front end of such receivers is highly susceptible to narrowband interference (NBI), which could undermine the overall performance of the receiver. To cope with this, we propose a multichannel energy detection scheme. The receiver uses a bank of correlators with different short delays to capture...
Transmitted Reference (TR) UWB using an autocorrelation receiver (AcR) provides a simple architecture and yet robust functionality against multipath propagation. Narrowband interference (NBI), however, can easily jam and saturate the AcR front-end and degrade the performance severely. To cope with this problem, we propose a front-end NBI cancellation technique followed by a linear combining stage...
Transmitted-reference ultra-wideband (TR-UWB) systems, in conjunction with autocorrelation-receivers (AcR), can collect all energy of the multipath channel response at low complexity. Unfortunately the AcR front-end also collects the energy of narrowband interference (NBI) signals, which severely degrades its performance. We present an elaborate statistical analysis of the NBI for a multichannel AcR...
Autocorrelation receiver (AcR) front-ends promise to provide a low-complexity, sub-optimal alternative to coherent reception for differentially modulated impulse radio (IR) ultra-wideband (UWB) signals (transmitted-reference (TR) systems). Due to the high processing gain of UWB-IR signals, these are normally quite robust against narrowband interference (NBI). Much of this robustness is unfortunately...
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