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Underlay ultra wideband (UWB) systems have to be able to detect the presence of primary systems operating in the same band for detect-and-avoid (DAA) operation. In this paper, the performances of joint and independent detection of multiple primary systems are investigated assuming that the primary systems are potentially dependent (e.g., frequency division duplex uplink-downlink communications). Joint...
This paper presents a design approach for high efficiency RF power amplifiers with dynamic biases for TDSCDMA systems. The design principle of a PA with dynamic bias is described in detail. The improvement of the power-added efficiency (PAE) is achieved by the drain bias control technique according to the variation of the input power. The simulation results illustrated that this PA can achieve high...
Multiuser diversity (MUD) underlies much of the recent work on both, unicast and multicast scheduling design in wireless networks. In that context, a large channel variation among users is not a drawback. In the case of unicast, the user with the best quality channel can access the medium while the other users can wait for a better quality channel. In the case of multicast, the sender transmitting...
We propose two phase constraining (PC) schemes using quantized feedback for multiple-input single-output (MISO) systems. The PC schemes are generalizations of the quadrature phase constraining (QPC) scheme. One PC scheme cophases channel gains with respect to the first transmit antenna channel gain, and the other PC scheme cophases channel gains by positioning all the channel gains into a fixed sector...
This paper analyzes the performance bound of variable gain relaying over non-identical Nakagami-m fading channel, and the closed-form expressions for average bit error probability (ABEP) of binary phase shift keying (BPSK)modulation and multiple amplitude modulation (M-AM) are derived. Numerical and simulation results show that the deduced performance bound is a tight lower bound especially at medium...
This paper aims at defining the expression of the probability of error of classification methods using a Synthetic Aperture Radar (SAR) intensity ratio as a classifier. The two SAR intensities involved in this ratio can be measurements from different dates, polarizations or possibly also frequency bands. Previous works provided a baseline expression of the probability of error addressing the two-class...
Having a piecewise linear fitting of gain, one can obtain a good approximation of phase. There are few ways to determine the slopes of a broken line approximation, but the most popular approaches need the breakpoints. In this paper we determine the breakpoints using a divide and conquer approach. Results of piecewise linear approximation of gain and of the resulting phase approximation are provided...
In this paper we study the impact of the overlapping between neighboring MPCs (multipath component) on the performance of channel estimation. We consider IR-UWB (impulse radio) signals, and the IEEE802.15.3a and IEEE802.15.4a UWB channel models. We show that for a pulse width (PW) sufficiently smaller than the average MPC rate of arrival (ROA) the probability to have more than three overlapping MPCs...
In this paper we consider the capacity of the cognitive radio (CR) channel in a fading environment under a ldquolow interference regimerdquo. This capacity depends critically on a power loss parameter, alpha, which governs how much transmit power the CR dedicates to relaying the primary message. We derive a simple, accurate approximation to alpha which gives considerable insight into system capacity...
This paper presents a technique for improving the gain characteristic by modifying the radiation elements. The resulting gain, obtained using the method of moments, is presented and discussed, together with the radiation pattern.
In this paper, we present an alternative and new interpretation of the Nyquist criterion in terms of Bode plots of the plant and the controller. This result gives a nonparametric characterization of the frequency response of arbitrary order stabilizing controllers. The result shows that the frequency response of any stabilizing controller must satisfy constraints on its magnitude, phase, and rate...
A graphene FET with a 0.5 ??m long gate an exceptional high power gain cut-off frequency fmax of 16 GHz is demonstrated. These preliminary results are very encouraging and demonstrate the potential of the epitaxially grown graphene devices for high-frequency applications as the quality of graphene on insulating substrates improve over time.
This paper analyzes the performance measures of amplify-and-forward (AF) relaying over non-identical Nakagami-m fading channel. The exact probability density functions (PDFs) of total signal-to-noise ratio (SNR) for variable gain relaying and fixed gain relaying are deduced, and the theoretical formulas of moment generating function (MGF) and moments for fixed gain relaying are presented. Since the...
Motivated by providing differentiated services on the Internet, we consider efficient online algorithms for buffer management in network switches. We study a FIFO buffering model, in which unit-length packets arrive in an online manner and each packet is associated with a value (weight) representing its priority. The order of the packets being sent should comply with the order of their arriving time...
Alpha-stable noise arises in many areas of electrical engineering including communications. However, no closed-form solution is known for its probability density function in general. Therefore, the maximum likelihood detector for alpha-stable noise is not known in general. A number of suboptimal detectors have been proposed based on various approximations for the alpha-stable distribution. However,...
Important insights can be gained by exploring the connections between project entities as recorded in the siloed databases maintained by software projects. We have developed Tesseract, a software archive browser that utilizes cross-linked displays to enable visual exploration of relationships between artifacts, developers, issues, and project communications.
We propose a robust maximum a posteriori probability (MAP) blind bit-rate detector (BBRD) for a fixed frame-length multiple access system which employs variable-gain receiver power and repetition encoding. this detector considers the rate detection (RD) as a multihypothesis test and maximizes the likelihood functions (LF)s to find the true bit-rate. Assuming that we have no knowledge about the receiver...
In this paper we propose a generalized GSR model of fair exchange for e-contracting. Based on the model, the methodology is narrated to implement e-contracting protocols that ensure fairness in true sense without using an additional trusted third party for which either party has to pay. The model provides the scope to include the validated contract and money atomicity properties within e-contracting...
Financial markets suggest new ways to design, organize and evolve user interfaces. In this paper we present an approach based on marketplace simulations, where UI resources are sold and acquired, attempting to prove that this metaphor can innovate the way we think about UI design and deployment, relying on self-ruling emerging properties of complex systems.
End-to-end telecommunication network simulator design and realization is described in the paper. The main applications of the simulator are conversational tests e.g. as per ITU-T P.800 and demonstrations. The simulator can be also used as a replacement of telecommunication chain part that is missing during end-to-end testing or measurements. Examples of achieved subjective test results are presented.
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