A robust feedback control design method is proposed for a class of uncertain time delay systems. Linear transformation is applied to convert the systems to new systems whose spectra embed all the unstable poles of the...
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A robust feedback control design method is proposed for a class of uncertain time delay systems. Linear transformation is applied to convert the systems to new systems whose spectra embed all the unstable poles of the original systems for given stability margin. A feedback control is then designed based on the new systems and reflected back to the original systems. It is proved that the designed control can asymptotically stabilize both the new and the original systems provided a set of sufficient conditions are satisfied.
A special complex sequence, called a complex quadratic sequence, is proposed as the frequency-spreading sequence for multicarrier spread spectrum (MC-SS) modulation sch.me. The resulting MC-SS signal has constant enve...
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A special complex sequence, called a complex quadratic sequence, is proposed as the frequency-spreading sequence for multicarrier spread spectrum (MC-SS) modulation sch.me. The resulting MC-SS signal has constant envelope in both time and frequency domains. This feature provides flexibility for the MC-SS system to mitigate the effects of both partial-band jamming and pulse jamming. For partial-band jamming, the MC-SS system with frequency domain detection and combining can outperform DS/SS. For pulse jamming, the MC-SS system with time-domain detection and combining can outperform other MC-SS systems. The proposed MC-SS signal has a constant envelope thus reducing linearity requirements on the power amplifier. A simple jammer state estimation sch.me for both partial-band and pulse jamming channel is also proposed and analyzed. Further-more multi-access with the MC-SS system is possible by assigning users with different cyclic-shifts of the complex quadratic sequence. Simulation results are provided to verify our analysis.
In this paper, we develop a hybrid control algorithm that produces control values for processes where only a limited number of function evaluations are available for the control law generation. This situation arises, ...
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In this paper, we develop a hybrid control algorithm that produces control values for processes where only a limited number of function evaluations are available for the control law generation. This situation arises, for example, in stencil printing processes in printed circuit board manufacturing, where the cost associated with multiple function evaluations is prohibitive. The proposed control algorithm is given by a modified version of a constrained conjugated-gradient method, transitioned into a windowed-smoothed block-form of the least-squares affine estimator.
As the size and complexity of VLSI circuits increase, the need for faster floorplanning algorithms also grows. In this work we introduce Traffic, a new method for creating wire- and area-optimized floorplans. Through ...
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As the size and complexity of VLSI circuits increase, the need for faster floorplanning algorithms also grows. In this work we introduce Traffic, a new method for creating wire- and area-optimized floorplans. Through the use of connectivity grouping, simple geometry, and efficient data structures, Traffic achieves higher result quality than Simulated Annealing (SA) in a fraction of the time. This speed allows designers to explore a large circuit design space in a reasonable amount of time, rapidly evaluate small changes to big circuits, and quickly produce initial solutions for other floorplanning algorithms.
We propose an adaptive token bucket algorithm for achieving proportional sharing of bandwidth among aggregate flows in differentiated service (DiffServ) networks. By observing the simulation results obtained in a stud...
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We propose an adaptive token bucket algorithm for achieving proportional sharing of bandwidth among aggregate flows in differentiated service (DiffServ) networks. By observing the simulation results obtained in a study of the throughput of TCP flows in a DiffServ network, we note that the aggregate flow with a lower target rate occupies more bandwidth than its fair share, while the aggregate flow with a higher target rate gets less than its fair share. The proposed algorithm solves this unfairness problem by adjusting the target rate according to the edge-to-edge feedback information. This algorithm does not require any additional signaling protocol or measurement of per-flow states, since it can be implemented in a distributed manner using only two-bit feedback information carried in the TCP acknowledgement. Using ns-2 simulations, we show that the proposed algorithm provides fair bandwidth sharing under various network conditions.
Numerous transport protocols have been proposed in related work for use by mobile hosts over wireless environments. A common theme among the design of such protocols is that they specifically address the distinct char...
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ISBN:
(纸本)9781581137538
Numerous transport protocols have been proposed in related work for use by mobile hosts over wireless environments. A common theme among the design of such protocols is that they specifically address the distinct characteristics of the last-hop wireless link, such as random wireless errors, round-trip time variations, blackouts, handoffs, etc. In this paper, we argue that due to the defining role played by the wireless link on a connection's performance, locating the intelligence of a transport protocol at the mobile host that is adjacent to the wireless link can result in distinct performance advantages. To this end, we present a receiver-centric transport protocol called RCP (Reception Control Protocol) that is a TCP clone in its general behavior, but allows for better congestion control, loss recovery, and power management mechanisms compared to sender-centric approaches. More importantly, in the context of recent trends where mobile hosts are increasingly being equipped with multiple interfaces providing access to heterogeneous wireless networks, we show that a receiver-centric protocol such as RCP can enable a powerful and comprehensive transport layer solution for such multi-homed hosts. Specifically, we describe how RCP can be used to provide: (i) a scalable solution to support interface specific congestion control for a single active connection;(ii) seamless server migration capability during handoffs;and (iii) effective bandwidth aggregation when receiving data through multiple interfaces, either from one server, or from multiple replicated servers. We use both packet level simulations, and real Internet experiments to evaluate the proposed protocol.
In this paper we introduce a new structured channel impulse response (CIR) estimation method for sparse multipath channels where we demonstrate a robust way of restoring the pulse shape into the composite CIR. We call...
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In this paper we introduce a new structured channel impulse response (CIR) estimation method for sparse multipath channels where we demonstrate a robust way of restoring the pulse shape into the composite CIR. We call this novel CIR estimation method Time-Of-Arrival based Blended Least Squares (TOA-BLS) which uses symbol rate sampled signals, and it is based on blending correlation processing followed by TOA estimation in the frequency domain by the least squares based channel estimation. TOA estimation in the frequency domain is accomplished by estimating the AR model parameters by solving the forward and forward-backward linear prediction equations in the least squares sense. Simulation examples are drawn from the ATSC digital TV 8-VSB system. The delay spread for digital TV systems can be as long as several hundred times the symbol duration;however digital TV channels are sparse where there are only a few dominant multipaths.
Popularity of the Internet and the availability of broadband links (e.g., xDSL and Cable) to residential consumers have initiated a demand for high quality video streaming. In video-on-demand-like (VoD) applications, ...
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Popularity of the Internet and the availability of broadband links (e.g., xDSL and Cable) to residential consumers have initiated a demand for high quality video streaming. In video-on-demand-like (VoD) applications, a server responds to a client's request by streaming a multimedia object. However, the delivered media quality is usually limited by the lowest-bandwidth link on the network path to the client. An approach that stores multi-rate (scalable) video sequence at a proxy can enhance the video quality and bandwidth efficiency. In this paper, we present Bandwidth Sensitive Caching (BSC) strategy where variable-rate streams are cached into a proxy in order to maximize the perceived video signal quality. The proxy determines the optimum rate at which a video needs to be stored base on the client capabilities and network link characteristics. Simulation results show that the proposed BSC algorithm is adaptive and robust to change in delivery condition, yet it is still simple and efficient for deployment onto proxies.
In this paper we consider a DFE-based soft decision detector for the BCJR front-end for a PRML coded magnetic recording channel. A practical implementation, however, requires a reduced-complexity soft equalizer as the...
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ISBN:
(纸本)0780376471
In this paper we consider a DFE-based soft decision detector for the BCJR front-end for a PRML coded magnetic recording channel. A practical implementation, however, requires a reduced-complexity soft equalizer as the BCJR detector has an exponential complexity as channel lengths increase. In previous work a bidirectional-arbitrated DFE(BAD)[1] was shown to perform in between a BCJR detector and MMSE-DFE. In this paper we propose a soft -output BAD(S-BAD) which takes advantage of the original structure, This new equalizer produces soft information in terms of extrinsic information suitable for iterative decoding when used with outer codes such as turbo/ turbo-like codes. The S-BAD can be employed when channel coefficients are known, and we show that when used with a serially-concatenated turbo code, it performs close to the BCJR detector and comparable to Turbo-DAE[2] but uses no BCJR-based decoder for any of the iterations. Figure 1 shows an S-BAD structure. It runs a forward and reverse MMSE-DFE and generates hard decisions at time k, xˆk,f and xˆk,b, then a final decision is made based on computed Euclidean distance λk,f, λk,b. Extrinsic information, Lext(xk is computed as Lext(x k) = {(xˆk,f (λk,b - λ k,f)/ 2σ2, if xˆk,f ≠ xˆk,b 2Ai(zk,f + zk,b)/ σ2, otherwise where σ2 is the noise variance of AWGN, Ai is the equalizer gain for iteration i, and z k,f/, zk,b are slicer inputs. During the iterative decoding process, the slicers are adjusted according to the new intrinsic information provided by the outer code. The MMSE-DFE coefficients are fixed at all iterations of decoding.
In this paper we consider theoretical and practical aspects of an M-ary optical recording channel. Specifically we address the performance tradeoffs between conventional pulse amplitude modulation (PAM) and M-ary runl...
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In this paper we consider theoretical and practical aspects of an M-ary optical recording channel. Specifically we address the performance tradeoffs between conventional pulse amplitude modulation (PAM) and M-ary runlength limited (RLL) coding in an optical disc system with compact disc parameters. Using a linear-tune invariant channel model with white and nonwhite noise components, we see that for signal-to-noise ratios found in typical CD systems, coded PAM outperforms M-ary RLL codes for a range of storage densities. In addition, this work also shows that for systems that require moderate-to-small values of M, M-ary RLL codes can provide significant advantages.
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