This paper addresses the problem of robust control design for a DC-DC Buck converter by means of a parameter dependent state feedback gain. Sufficient conditions are given for the existence of a robust stabilizing con...
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This paper addresses the problem of robust control design for a DC-DC Buck converter by means of a parameter dependent state feedback gain. Sufficient conditions are given for the existence of a robust stabilizing control law which assures to the uncertain closed-loop system a prespecified pole location inside a circle on the left-hand half of the complex plane. The output load is considered as an uncertain parameter belonging to a known interval (polytope type uncertainty). The control gain changes as the load varies, allowing to impose to the closed-loop system a dynamic behavior that cannot be achieved through a fixed gain. The robust stabilizability condition is formulated in terms of a set of linear matrix inequalities involving only the vertices of the uncertainty polytope. Simulation results illustrate the proposed method.
The polynomial model is commonly used in predistorter design. However, the conventional polynomial model exhibits numerical instabilities when high-order terms are included. In this paper, we introduce a novel set of ...
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The polynomial model is commonly used in predistorter design. However, the conventional polynomial model exhibits numerical instabilities when high-order terms are included. In this paper, we introduce a novel set of orthogonal polynomial basis functions for predistorter modeling. Theoretically, the conventional and the orthogonal polynomial models are "equivalent" and thus should have the same performance. In practice, however, the two approaches can perform quite differently in the presence of quantization noise and with finite precision processing. Simulation results show that the orthogonal polynomials can alleviate the numerical instability problem associated with the conventional polynomials and generally yield better predistortion linearization performance.
Soft-output equalizers that exploit a priori information on the channel inputs play a central role in turbo equalization. Such equalizers are traditionally implemented with the forward-backward or BCJR algorithm, whos...
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Soft-output equalizers that exploit a priori information on the channel inputs play a central role in turbo equalization. Such equalizers are traditionally implemented with the forward-backward or BCJR algorithm, whose complexity is prohibitive for channels with large memory. Many reduced-complexity alternatives to the BCJR algorithm have been proposed that use a linear equalizer and use the a priori information to perform soft intersymbol interference cancellation. In this work, we propose a soft-feedback equalizer (SFE) that combines the equalizer output and the a priori information to improve interference cancellation. Also, by assuming a statistical model for the a priori information and the SFE output, we obtain an equalizer with linear complexity, as opposed to the quadratic complexity of some similar structures. Simulation results show that the SFE may perform within 1 dB of a system based on an BCJR equalizer, within 0.3 dB of quadratic complexity sch.mes, and consistently outperforms other linear complexity sch.mes.
This paper is concerned with the problem of double struck D sign-stability of linear systems. New sufficient conditions formulated as linear matrix inequalities are presented for both continuous-time and discrete-time...
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This paper is concerned with the problem of double struck D sign-stability of linear systems. New sufficient conditions formulated as linear matrix inequalities are presented for both continuous-time and discrete-time systems. These conditions encompass recently appeared results from the literature and provide less conservative double struck D sign-stability evaluations, as illustrated by means of numerical examples.
This paper reports on the design, implementation and characterization of high-frequency single crystal silicon (SCS) block resonators with piezoelec.ric elec.romechanical transducers. The resonators are fabricated on ...
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This paper reports on the design, implementation and characterization of high-frequency single crystal silicon (SCS) block resonators with piezoelec.ric elec.romechanical transducers. The resonators are fabricated on 4μm thick SOI substrates and use sputtered ZnO as the piezo material. The centrally-supported blocks can operate in their first and higher order length extensional bulk modes with high quality factor (Q). The highest measured frequency is currently at 210MHz with a Q of 4100 under vacuum, and the highest Q measured is 11,600 at 17MHz. The uncompensated temperature coefficient of frequency (TCF) was measured to be -40ppm/°C and linear over the temperature range of 20-100°C.
We describe a novel method for authenticating multicast packets that is robust against packet loss. Our focus is to minimize the size of the communication overhead required to authenticate the packets. Our approach is...
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We describe a novel method for authenticating multicast packets that is robust against packet loss. Our focus is to minimize the size of the communication overhead required to authenticate the packets. Our approach is to encode the hash values and the signatures with Rabin's Information Dispersal Algorithm (IDA) to construct an authentication sch.me that amortizes a single signature operation over multiple packets. This strategy is especially efficient in terms of space overhead, because just the essential elements needed for authentication (i.e., one hash per packet and one signature per group of packets) are used in conjunction with an erasure code that is space optimal. Using asymptotic techniques, we derive the authentication probability of our sch.me using two different bursty loss models. A lower bound of the authentication probability is also derived for one of the loss models. To evaluate the performance of our sch.me, we compare our technique with four other previously proposed sch.mes using empirical results.
The singular-value decomposition can be used to transform a MIMO fading channel into an equivalent bank of scalar subchannels, a strategy known as eigenbeamforming or closed-loop MIMO, provided that the transmitter kn...
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The singular-value decomposition can be used to transform a MIMO fading channel into an equivalent bank of scalar subchannels, a strategy known as eigenbeamforming or closed-loop MIMO, provided that the transmitter knows the channel. We consider the problem of allocating bits to subchannels after such processing, and propose simple strategies, which achieve near-optimal performance, by exploiting statistical properties of singular values. For large antenna arrays, a fixed bit-allocation becomes an attractive choice without any significant performance loss. For example, on the 6-input 6-output Rayleigh-fading channel, the fixed allocation strategy performs only 0.25 dB worse than the optimal bit-allocation.
In this paper we consider rate compatible puncturing of low density parity check (LDPC) codes. We present a general density evolution-based procedure which finds the optimal puncturing of a base code. We show that pun...
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In this paper we consider rate compatible puncturing of low density parity check (LDPC) codes. We present a general density evolution-based procedure which finds the optimal puncturing of a base code. We show that puncturing can be performed across a range of rates and code lengths in a manner that produces punctured codes with good thresholds. This allows one to implement a single optimal LDPC code of a low rate that can be punctured across a wide range of rates without loss of threshold performance. Simulation results show that the error floors of the codes do not degrade after puncturing.
This paper presents a distributed video streaming framework using unbalanced multiple description coding (MDC) and forward error correction. In the proposed video streaming framework, two senders simultaneously stream...
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This paper presents a distributed video streaming framework using unbalanced multiple description coding (MDC) and forward error correction. In the proposed video streaming framework, two senders simultaneously stream complementary descriptions to the receiver over different paths. To minimize the overall distortion and exploit the benefits of multi-path transport when the characteristics of each path are different, an unbalanced MDC method for wavelet-based coders combined with a TCP-friendly rate allocation algorithm is proposed. The proposed rate allocation algorithm adjusts the transmission rates and the channel coding rates for all senders in a coordinated fashion to minimize the overall distortion. Simulation results show that the proposed unbalanced MDC combined with our rate allocation algorithm achieves about 1 - 3 dB higher PSNR compared to conventional balanced MDC when the available bandwidth along each path is different in time-varying network conditions.
We improved Kerberos authentication protocol for wireless communication using elliptic curve cryptographic operations. Proposed protocol offers the strength of public key cryptography and costs only 68.7 ms extra load...
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We improved Kerberos authentication protocol for wireless communication using elliptic curve cryptographic operations. Proposed protocol offers the strength of public key cryptography and costs only 68.7 ms extra load to standard Kerberos without using pre-computation tables for 160-bit curve and scalable architecture, whereas with customized curve library it costs 57.3 ms extra load for the same key length. Using pre-computation tables reduces these timings to 55.8 ms and 51.6 ms respectively. Proposed protocol requires less bandwidth than other public key cryptography enabled Kerberos solutions. Results were obtained using 32-bit StrongARM1 processor runs 206 MHz. Due to its bandwidth efficiency and fast execution performance ECC supported Kerberos protocol can be an important option among other user authentication protocols for wireless networks.
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