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The development of next-generation networks has been driven by a number of use cases aimed at supporting innovative applications and services. Among these drivers the Internet of Things has gained momentum due to its potential to leverage Machine Type Communications (MTC), a term used to denote machine-centered communications among sporadic, bursty traffic generating devices. While scalability issues...
Maximum a posteriori (MAP) sequence detection for channels with intersymbol interference (ISI) has previously required knowledge of the channel sampled impulse response (SIR). Generally the SIR coefficients are determined via least mean square (LMS) or recursive least squares (RLS) estimation algorithms. For many unguided media channels such as mobile radio and high frequency radio which exhibit a...
This paper addresses the problem of multiuser detection in multipath fading code-division multiple-access (CDMA) channels with non-Gaussian noise. A robust multipath decorrelator is proposed to mitigate the multiple-access interference and the multipath interference, and to ameliorate non-Gaussian ambient noise. The performance of the proposed multiuser detector is assessed via computer simulations...
In this paper a new spectrum sensing technique for multiple antenna cognitive radio network is proposed. While a large majority of the existing literature assume that the signal is corrupted by additive white Gaussian noise, this assumption is not always true in practice. In the present work, slow Rayleigh fading channel in the presence of impulsive noise is considered and BPSK modulation is employed...
Recent studies have shown that, while the available licensed radio spectrum becomes more occupied, the assigned spectrum is significantly underutilized. To alleviate the situation, cognitive radio (CR) technology has been proposed to provide an opportunistic access to the licensed spectrum areas. CR systems are able to serve the secondary users for detecting and utilizing so called spectrum holes...
This paper presents a new M-estimator based robust multi-user detection technique in asynchronous direct sequence-code division multiple access systems over Nakagami-m fading channels with impulsive noise. A new M-estimator, which performs well in the heavy-tailed impulsive noise, is proposed and analyzed for robustifying the detector. Average probability of error is derived and the performance of...
This paper proposes an efficient design strategy for sequential detectors to reliably detect primary user's signals, especially in a fast fading scenario. We study computation of the log-likelihood ratio for coping with fast changing sample variances of received signal and noise, which are considered random variables. First, we analyze the detectability of the conventional generalized log-likelihood...
A fading Multiple Access Channel (MAC) between distributed sensors and multiple antennas yields incoherent fusion in Wireless Sensor Networks. With limited on-board energy, an overall sensor power constraint is not only reasonable and desirable but indeed, inevitable. With unknown/varying channel gain envelope, Uniform Power Allocation (UPA) to sensors is suboptimal. The problem is compounded if,...
Spectrum sensing design for Cognitive Radio systems is challenged by the nature of the wireless medium, which makes the detection requirements difficult to achieve by standalone sensors. To combat shadowing and fading, distributed strategies are usually proposed. However, most distributed approaches are based on the energy detector, which is not robust to noise uncertainty. This phenomenon can be...
This paper considers cooperative spectrum sensing in Cognitive Radios. In our previous work we have developed DualSPRT, a distributed algorithm for cooperative spectrum sensing using Sequential Probability Ratio Test (SPRT) at the Cognitive Radios as well as at the fusion center. This algorithm works well, but is not optimal. In this paper we propose an improved algorithm- SPRT-CSPRT, which is motivated...
Motivated by the demand and the low utilization of spectrum resource, cognitive radio appears as an alternative for the present spectrum distribution policy. Spectrum sensing is the key procedure and energy detector is the most commonly used algorithm in spectrum sensing. The communication signal often varies by time, which causes the spectrum sensing to be inaccurate. In this paper, we use window...
In this paper, optimal detection of PSK signals with pilot symbol assisted modulation (PSAM) in Rayleigh frequency-flat fast fading channels is investigated. We prove that in spatially uncorrelated single-input multiple-output channels, the optimal symbol-by-symbol detector is equivalent to a mismatched detector with minimum mean square error (MMSE) channel estimation. However, this is not the case...
The use of side information can dramatically improve the performance of fast frequency hopping (FFH) spread spectrum systems. Unfortunately, little paper discussed how to get this information. In this paper, the generation of side information for FFH systems in the presence of partial-band jamming is investigated. We focus on the slowly changing interference and propose an FFH receiver model with...
In cognitive radio networks, spectrum sensing is a key technology to detect the presence of the primary user. In this paper, a joint energy and autocorrelation based spectrum sensing algorithm is proposed. The proposed detection algorithm is based on the assumption that the primary user's signal is not white. We compare the performance of the proposed detector and the conventional energy detector...
We derive detection metrics for soft-output diversity combining for the case of imperfect channel state information at the receiver. We treat in particular the case when the noise variance at the receiver is unknown. We contrast conventional training-based methods to a detector based on the generalized likelihood-ratio (GLR) test paradigm. We study the performance of the detectors via EXIT chart analysis...
Cognitive radio systems must robustly sense spectrum holes if they want to use spectrum opportunistically. A traditional sensitivity based time-domain perspective on this sensing problem is relatively straightforward and such sensitivity based sensors are easy to certify. However, this problem is more subtle than it first appears. To really understand the question of what should be the right level...
Spectrum sensing is a key enabling technology of cognitive radio. Reliable detection increases access opportunity to temporarily unused bands and prevents harmful interference to the licensed users. Due to the receiver noise, signal attenuation, and multi-path fading effect, however, it is usually not possible to determine the existence of primary signal with absolute certainty. By extracting a global...
A hybrid PN-code acquisition scheme is proposed and studied for direct sequence code division multiple access communications in frequency-selective Rayleigh fading channels. The most important feature of the proposed system is its ability to dynamically estimate the number of multipath signals that may lie in the reference channel. The basic idea of the considered algorithm is to sort the partial...
In this paper, we investigate cooperative sensing schemes to identify primary signals in fading environment for cognitive radio (CR) networks employing energy detectors. We consider a parallel fusion architecture in which all the sensing devices send their quantized sensing information to an access point, which then applies a fusion rule to determine the presence of the primary signal. We assume independent...
In this paper, we address the problem of improved robust CDMA signal detection in asynchronous non Gaussian flat-fading channels. Since the performance of robust multiuser detector depends on the selection of M-estimator and the spreading sequences, the new influence function proposed in with spatio-temporal chaotic spreading is considered to develop a new better performing robust detector for the...
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