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We built a prototype of a closed-loop controlled (non-backlash gear: patent) microwave quadrant detector and succeeded in continuous capturing and tracking of a wild bird, based on weak pilot signals from transmitter on the wild bird to obtain the vital data.
In dynamic spectrum access networks, spectrum sensing plays a key role in determining the reliability and efficiency of opportunistic spectrum utilization. However, when treating the transmission over a licensed bandwidth as a black box, most energy detection-based sensing methods lack the ability of adapting the sensor to the changes in channel condition. This paper introduces a feedback mechanism...
In this paper, we investigate the benefit of joint network-channel (JNC) coding for the multiple-access full-duplex relay channel. We use superposition block Markov network-channel (distributed) coding and (iterative) joint decoding at the destination. Prominent amongst our system assumptions are the fact that the medium access is not orthogonal and that the source-to-relay links are not error-free,...
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 cooperative spectrum sensing, each cognitive radio (CR) user needs to report its local sensing results to a common CR user for a final decision. Most of existing contributions assume that such a reporting is perfect, i.e., there always exists an idle channel to accomplish an error free reporting. However, it is not true in practice since the reporting actually belongs to secondary transmission...
The well-known energy detector, due to its simplicity, has been proposed as an efficient spectrum sensing method for cognitive radio networks. However, shadowing and fading degrade performance of energy detector. In this paper, to combat these effects, we exploit multiple antennas for each user and cooperation among users. Moreover, we consider spatial correlation among users as well as among antennas...
In this paper we study the performance of space-time bit-interleaved coded modulation (ST-BICM) over block-fading multi-input multi-output (MIMO) channels with iterative receivers based on minimum mean square error (MMSE) detection. We show how full diversity can be achieved with a special class of space-time precoders. Performance in terms of symbol error rate (SER) and word error rate (WER), obtained...
The CR node in depth fading is possible to have serious false alarm or missed when using conventional collaborative spectrum sensing method. These error messages will be fully included in the final collaborative decision, which will seriously affect the performance of collaborative sensing. So, a new exponential weighted collaborative spectrum sensing based on SNR is proposed and studied as a means...
Code synchronization is a critical step for fast and reliable code search in direct-sequence spread-spectrum (DS-SS) system. In this paper, we propose a novel differentially coherent (DC) detection scheme for rapid code acquisition over a fast Rayleigh fading mobile radio channel with frequency offset, and compare the performance with the conventional I-Q noncoherent detection scheme. Numerical results...
In this paper, we consider spectrum sensing of DVB-T signals in different fading environments. We compare state-of-the-art detectors including detectors based on pilot subcarriers, as well as detectors for general OFDM signals that exploit the correlation structure incurred by the cyclic prefix. Energy detection is also included for comparison. We show numerically that the choice of detector depends...
Acoustic emissions found in underwater channels cover a broad spectrum of sources. Signals are often characterized by parameters such as amplitude, frequency, phase or modulation. However, once transmitted, and given that other sonars can also be simultaneously transmitting, it is generally difficult to identify the origin of a signal such as location and source of the transmission. A solution to...
This paper proposes a fast frequency-hopping M-ary frequency-shift keying dynamic multiple-access (FFH/MFSK DMA) scheme for application in cognitive radios (CRs). For characterising the performance of the FFH/MFSK DMA systems, primary users (PUs) are assumed to become active according to a Poisson process. In our FFH/MFSK DMA system, the noncoherent majority vote assisted single-user detector (MV-SUD)...
The last decades has seen a fast growth in published papers concerning the scientific investigation and design of digital communication systems. There is a well developed theory for this purpose, since long. Central here is the theory for Hypothesis Testing and Random Processes. This approach has been abandoned over the years, resulting in applying procedures used in the area of Signal Processing...
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 key enabling functionality of a cognitive radio is to ensure that it would not interfere with primary users, by reliably detecting primary user signals. Due to the low computational complexity, Energy detector is a widely used spectrum sensing method. The performance of energy detector in fading channels has been previously analyzed in some papers. However, these analyses are based on the exact...
The performance of spatial multiplexing-based multiple-input multiple output (MIMO) systems using zero forcing (ZF) detector in frequency selective fading channels is analyzed in this paper. The approximation of a linear combination of Wishart matrices is used to derive the probability density function (p.d.f.) of output signal-to-noise ratio (SNR) expression. Analytical error rate expressions for...
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...
In this paper, we applied genetic algorithm (GA) scheme as a suboptimal detection of a bit-synchronous code division multiple access (CDMA) systems over a Gaussian channel. The GA scheme attempts to search for the user's transmitted bit sequence that optimizes the correlation matrix employed. Simulation results showed that the Bit Error Rate (BER) performance of our proposed multiuser detector is...
A cognitive radio should be capable of finding the best spectrum band for communication depending on primary transmissions, the ambient noise level and interference. The first step in achieving this goal is to sense the existence of primary and secondary transmitters in various channels. In addition to the problem of signal detection, there is a need to distinguish between different signals at very...
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