The connection of generation to distribution networks may cause problems with existing protection sch.mes, while development of new protection sch.mes can facilitate an increase in generation capacity. The design and ...
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We consider a low-complexity adaptive MIMO transmission approach for spatially correlated channels. The proposed sch.me adaptively switches between different transmission modes depending on the changing channel condit...
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We consider a low-complexity adaptive MIMO transmission approach for spatially correlated channels. The proposed sch.me adaptively switches between different transmission modes depending on the changing channel conditions, as a means to enhance system capacity. Each mode is a combination of a transmission technique (i.e. statistical beamforming, double space-time transmit diversity and spatial multiplexing) and a modulation/coding sch.me. We first motivate our adaptive algorithm by deriving new closed-form capacity expressions, and demonstrating significant information theoretic improvements over non-adaptive transmission. We then present a practical method to switch between different modes, based on the channel statistics. Our approach is shown to yield significant improvements in spectral efficiency for typical channel scenarios
In this paper we present a comparative study of two adaptive algorithms applied to the impulse response estimation of the newly proposed space-time geometrical-based hyperbolic distributed scatterers (GBHDS) channel m...
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In this paper we present a comparative study of two adaptive algorithms applied to the impulse response estimation of the newly proposed space-time geometrical-based hyperbolic distributed scatterers (GBHDS) channel model. The two adaptive algorithms which form the basis of this study are the decision-directed recursive least square (RLS) and the decision-directed least mean square (LMS) algorithms. In this estimation task, the performance of the decision-directed RLS algorithm is found to be better than that of the decision-directed LMS algorithm.
When sensor nodes are organized in clusters, they could use either single hop or multi-hop mode of communication to send their data to their respective cluster heads. We present a systematic cost-based analysis of bot...
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Using a nonlinear filter to control a linear device has been studied in [1], and been proved to be effective in active noise control (ANC) when i) the secondary path has a linear and nonminimum phase transfer function...
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Using a nonlinear filter to control a linear device has been studied in [1], and been proved to be effective in active noise control (ANC) when i) the secondary path has a linear and nonminimum phase transfer function, and the reference noise is a nonlinear, predictable noise or non-Gaussian noise;ii) the primary path has a nonlinear effect. Tan et al. reinforced these statements and successfully implemented this idea with an adaptive Volterra filter, and developed an algorithm called the Volterra filtered-x LMS (VFXLMS) algorithm. However this VFXLMS suffers from a heavy computational burden as well as stability problems. In this paper, we provide several alternatives to VFXLMS: the modified Volterra LMS algorithm that increases the convergence rate by slightly increasing the computational burden, the filtered-error Volterra LMS algorithms (including the adjoint Volterra LMS algorithm and the secondary-path equalization Volterra LMS algorithm) that greatly reduce the computation complexity but also reduce the convergence rate, and the hybrid filtered-error Volterra LMS algorithm. This latter method reduces the computational complexity and improves the convergence rate. Analysis and simulation results prove the effectiveness of our proposed adaptive algorithms.
The distributed coordination function (DCF) mode of the IEEE 802.11 MAC standard, though proposed for medium access in wireless local area networks, is seen as the de-facto medium access standard in multi-hop wireless...
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Reducing energy consumption has become one of the major challenges in designing future computing systems. This paper proposes a novel idea of using program counters to predict I/O activities in the operating system. T...
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Reducing energy consumption has become one of the major challenges in designing future computing systems. This paper proposes a novel idea of using program counters to predict I/O activities in the operating system. The paper presents a complete design of Program-Counter Access Predictor (PCAP) that dynamically learns the access patterns of applications and predicts when an I/O device can be shut down to save energy. PCAP uses path-based correlation to observe a particular sequence of program counters leading to each idle period, and predicts future occurrences of that idle period. PCAP differs from previously proposed shutdown predictors in its ability to: (1) correlate I/O operations to particular behavior of the applications and users, (2) carry prediction information across multiple executions of the applications, and (3) attain better energy savings while incurring low mispredictions.
We consider the problem of reachback communication in wireless sensor networks: multiple sensors are deployed on a field, and they collect local measurements of some random process which then need to be encoded and re...
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We consider the problem of reachback communication in wireless sensor networks: multiple sensors are deployed on a field, and they collect local measurements of some random process which then need to be encoded and reproduced at a remote location. In this paper we present the design of a distributed modulation sch.me for reachback, dubbed dFSK (for distributed Frequency Shift Keying). In dFSK, all nodes in the network first agree on a common stream of bits to send. Then, nodes listen to a few transmissions by other nodes to form an estimate of when to sch.dule their own transmissions. The aggregate waveform that results from superimposing a large number of these weak transmissions has a pre-specified set of zero-crossings. It is through the location of these zeros that information is conveyed to the far receiver. This mode of operation is analogous to that of standard FSK, where it is through spectral properties of the transmitted symbol (and hence closely related to the rate of its zero-crossings) that information is conveyed to the far receiver.
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