Advanced noise abatement procedures such as the three degree decelerating approach (TDDA) can significantly reduce the noise impact of aircraft during approach. With existing aircraft performance and flight operation uncertainties, however, implementation of the TDDA would require an increase in the initial separation between aircraft that would result in significant reduction in runway capacity. Simulation results indicate that this reduction in runway capacity is on the order of 50%, which is not acceptable for any procedure that must be used n high traffic scenarios. In this paper, we introduce a modified three degree decelerating approach (MTDDA) that provides the same noise benefits as the TDDA with little or no loss in capacity relative to conventional approach procedures. Simulation results indicate that for a representative aircraft mix, the capacity of the MTDDA is within 2% less of the maximum possible capacity using conventional approach procedures. View full abstract»

Advanced noise abatement procedures such as the three degree decelerating approach (TDDA) can significantly reduce the noise impact of aircraft during approach. With existing aircraft performance and flight operation uncertainties, however, implementation of the TDDA would require an increase in the initial separation between aircraft that would result in significant reduction in runway capacity. Simulation results indicate that this reduction in runway capacity is on the order of 50%, which is not acceptable for any procedure that must be used n high traffic scenarios. In this paper, we introduce a modified three degree decelerating approach (MTDDA) that provides the same noise benefits as the TDDA with little or no loss in capacity relative to conventional approach procedures. Simulation results indicate that for a representative aircraft mix, the capacity of the MTDDA is within 2% less of the maximum possible capacity using conventional approach procedures. View full abstract»

In Multiple-Input Multiple-Output (MIMO) systems, Sphere Decoding (SD) can achieve performance equivalent to full search Maximum Likelihood (ML) decoding with reduced complexity. Several researchers reported techniques that reduce the complexity of SD further. In this paper, a new technique is introduced which decreases the computational complexity of SD substantially, without sacrificing performance. The reduction is accomplished by deconstructing the decoding metric to decrease the number of computations and exploiting the structure of a lattice representation. Simulation results show that this approach achieves substantial gains for the average number of real multiplications and real additions needed to decode one transmitted vector symbol. As an example, for a 4 × 4 MIMO system, the gains in the number of multiplications are 85% with 4-QAM and 90% with 64-QAM, at low SNR. View full abstract»

In experimental and observational sciences, detecting atypical, peculiar data from large sets of measurements has the potential of highlighting candidates of interesting new types of objects that deserve more detailed domain-specific followup study. However, measurement data is nearly never free of measurement errors. These errors can generate false outliers that are not truly interesting. Although many approaches exist for finding outliers, they have no means to tell to what extent the peculiarity is not simply due to measurement errors. To address this issue, we have developed a model-based approach to infer genuine outliers from multivariate data sets when measurement error information is available. This is based on a probabilistic mixture of hierarchical density models, in which parameter estimation is made feasible by a tree-structured variational expectation-maximization algorithm. Here, we further develop an algorithmic enhancement to address the scalability of this approach, in order to make it applicable to large data sets, via a K-dimensional-tree based partitioning of the variational posterior assignments. This creates a non-trivial tradeoff between a more detailed noise model to enhance the detection accuracy, and the coarsened posterior representation to obtain computational speedup. Hence, we conduct extensive experimental validation to study the accuracy/speed tradeoffs achievable in a variety of data conditions. We find that, at low-to-moderate error levels, a speedup factor that is at least linear in the number of data points can be achieved without significantly sacrificing the detection accuracy. The benefits of including measurement error information into the modeling is evident in all situations, and the gain roughly recovers the loss incurred by the speedup procedure in large error conditions. We analyze and discuss in detail the characteristics of our algorithm based on results obtained on appropriately designed synthetic data experimen- - ts, and we also demonstrate its working in a real application example. View full abstract»

In this paper, a new circuit topology to realize a stacked self-oscillating LNA-Mixer is proposed. The basic idea has been to recognize that in a high-performance down-conversion mixer its RF input-stage gain, linearity, and noise tradeoff is often improved by feeding it with a bypass current source. This current source could be isolated with an inductor so as to allow free implementation of the oscillator block on top of it. Using these guidelines, the presented circuit achieves high-performance without sacrificing compatibility with modern low-voltage CMOS implementations. To further demonstrate usefulness of the circuit, an entire single-stage quadrature (IQ) RF front-end using this circuit as a core has been developed. The IQ front-end, targeted for the Galileo satellite navigation system, has been designed using a 65-nm CMOS technology, and it achieves NF=4.4 dB, IIP3=-15 dBm and A_v=25 dB at 1.575 GHz, while using only 1 mA from the low 1.2-V supply. View full abstract»

Summary form only given. Both dispersion management and the use of a nonlinear optical loop mirror (NOLM) as a saturable absorber can improve the performance of a soliton-based communication system. Dispersion management gives the benefits of low average dispersion while allowing pulses with higher powers to propagate, which helps to suppress Gordon-Haus timing jitter without sacrificing the signal-to-noise ratio. The NOLM suppresses the buildup of amplifier spontaneous emission noise and background dispersive radiation which, if allowed to interact with the soliton, can lead to its breakup. We examine optical pulse propagation in dispersion-managed (DM) transmission system with periodically inserted in-line NOLMs. To describe basic features of the signal transmission in such lines, we develop a simple theory based on a variational approach involving Gaussian trial functions. It, has already been proved that the variational method is an extremely effective tool for description of DM solitons. In the work we manage to include in the variational description the point action of the NOLM on pulse parameters, assuming that the Gaussian pulse shape is inherently preserved by propagation through the NOLM. The obtained results are verified by direct numerical simulations. View full abstract»

This paper investigates SiGe profile design tradeoffs for low-noise RF applications at a given technology generation (i.e., fixed minimum feature size and thermal cycle). An intuitive model relating structural parameters and biases to noise parameters is used to identify the noise limiting factors in a given technology. The noise performance can be improved by pushing more Ge into the base and creating a larger Ge gradient in the base. To maintain the SiGe film stability, the retrograding of the Ge into the collector has to be reduced, leading to a stronger f_T-I_C roll-off at high injection. Two low-noise profiles were designed and fabricated explicitly for improving minimum noise figure (NF_min) without sacrificing gain, linearity, frequency response, or the stability of the SiGe strained layer. A 0.2 dB NF_min was achieved at 2.0 GHz with an associated gain (G_assoc) of 13 dB View full abstract»

Wireless communication systems are expanding rapidly leading to the proliferation of RF applications in the UHF band (0.9-3 GHz). However stringent requirements are placed to make it essential for these applications to conform to strict technical standards and attain a high level of integration. These demands including low cost, low voltage, low power dissipation, low noise and low distortion cannot be achieved without fabricating high quality passive devices in the same substrate using the same technology. Therefore, recent advances in Bipolar, CMOS and BiCMOS processes have stimulated new approaches to circuit integration and architecture. This has included high conductivity multi-metal layers, low loss substrates and thick oxide to isolate components from lossy substrates. In parallel, with the insight gained from these investigations, simplified physical models and various numerical techniques have been developed to assess the performance of passive devices such as transmission lines and spiral inductors. Unfortunately, these approaches are not easily implemented in CAD tools and sometimes suffer from incompleteness. In fact, in many instances, circuits are successfully simulated but actual prototypes often fail to match the simulated results because of parasitic effects. This work describes the characterization of embedded transmission lines (ETL) and spiral inductors using scattering parameter measurements. A simple approximation allows for the extraction of the devices characteristics, taking into account capacitive and inductive coupling as well as losses. Thus calculations can be easily and quickly performed using these models. View full abstract»

In an integrated services network, resources are shared by multiple traffic classes. Service classes that deliver quality-of-service (QoS) to applications have priority over others that do not. In such a multi-service network, routing decisions for high priority QoS traffic will affect what resources are available for lower priority traffic: poor route selection can result in congestion for, or even starvation of, lower priority traffic. Whereas many studies have focused on routing algorithms that optimize the network throughput for individual service classes, little effort has been devoted to routing algorithms that address inter-class resource sharing. In this paper, we propose a routing algorithm that allows dynamic sharing of link resources among multiple traffic classes. The algorithm is based on the concept of “virtual residual bandwidth”, which is derived from the link residual bandwidth by taking the congestion condition of low priority traffic into account. By using the virtual residual bandwidth in the link cost function for QoS sessions, we discourage QoS sessions from using links that are heavily loaded with low priority traffic. Our approach is simple in the sense that besides changing the link cost function, no other changes to the routing algorithms for individual service classes are required. An extensive simulation study shows that when the traffic load is unevenly distributed, significant performance improvements can be achieved for low priority traffic without sacrificing performance for high priority traffic. The result demonstrates that QoS routing is important even when the QoS traffic load is light and call blocking is not an issue View full abstract»

To save the precious wireless resources in wireless networks, we investigate cross-layer optimization schemes to reduce wireless resource consumption (WRC) for reliable mobile multicast. We characterize WRC by signal-to-noise ratio (SNR) per information bit and by power-delay product for scenarios without and with delay quality of service (QoS) constraints, respectively. Aiming at decreasing WRC, we develop a cross-layer parameter-selection (CLPS) algorithm, which dynamically adjusts the parameters of the physical layer and the medium access control (MAC) layer according to the variations of multicast group size, transport-layer error-control parameters, and delay QoS constraints. In particular, we first derive the optimal physical-layer parameters, including constellation size and transmit SNR, to minimize WRC for Threshold-0 multicast policy, where the sender transmits data regardless of channel qualities. Then, we develop a suboptimal approach for the selection of MAC-layer multicast threshold to achieve low power-delay product. In addition, we study the effects of pure automatic repeat request (ARQ) and hybrid ARQ-forward error correction (FEC) based error-control schemes on the CLPS algorithm. Also conducted is a set of numerical analyses to show the performance gain achieved through the cross-layer design and the impacts of various system parameters on the WRC optimization. View full abstract»

A novel Low Noise Amplifier (LNA) topology with a transformer-based input integrated matching is here proposed and its application to 60-GHz. This new architecture achieves both input matching and gain boosting in cascode amplifier without requiring the conventional inductive source degeneration, which is known for gain decreasing at high frequency. The transformer has been designed with the 3-D electromagnetic simulator HFSS^TM and is fully compatible with a CMOS bulk general purpose process design flow. Implemented in a 65 nm, post-layout simulations exhibit a -17 dB input matching and a 7.5 dB Noise Figure (NF) at 60 GHz. Biased under 1.2 V, this two-stage LNA reaches a 12.5 dB S₂₁ for a 34 mW power consumption. Thanks to a lumped component design approach, the final circuit takes place in a 540 mum x 690 mum silicon area with PADs. View full abstract»

An optimal digital signal combining algorithm for arraying is proposed. Our approach is a blind combining technique, which doesn't require any training sequence. In achieving coherence among various receivers, the combining algorithm attempts to maximize the combined output signal-to-noise ratio (SNR). It's shown in numerical simulations that the combining loss of an 8-element array could limited to about 0.7 dB at 2000 symbols/interval in low SNR, which is about 2.5 dB combining loss less than the traditional MMSE adaptive weight estimation using a single reference signal. This results suggests that the combining algorithm proposed here is capable of improving the combining SNR without complex computation. View full abstract»

A novel sub-harmonic pumping direct conversion receiver (SHP-DCR) employing antiparallel diode pair (APDP) is proposed for high instantaneous dynamic range receivers used in mobile communications. The proposed SHP-DCR can suppress even harmonic mixing products, such as second order intermodulation (IM2) and LO noise that interfere a desired baseband signal. Moreover, the design condition of load resistance is indicated by analytical and experimental approaches for improving diode mixer disadvantages of lower conversion gain and higher LO power. A developed L-band SHP-DCR without a low noise amplifier achieves NF of 18.5 dB, IP3 at input port of 3 dBm and IM2 is below -90 dB in the actual input range. View full abstract»

Several variations of the sum-product algorithm (SPA) have been proposed for the decoding of the low density parity check (LDPC) codes. Among these, the log domain belief propagation algorithm (log-BPA or simply BPA) is widely adopted in most of the proposed LDPC decoder architectures. The check node unit (CNU), which computes the check-to-variable (C2V) messages, is computationally the most complex part of the decoder employing the belief propagation algorithm. The BPA can be approximated using a sub-optimal min-sum algorithm; however, it suffers from the performance loss. The min-sum algorithm can be easily implemented with comparators and multiplexers, thereby reducing the area and the power consumption of the decoder, critical for the high data-rate applications such as ultra wide-band (UWB) communications system. Due to the performance degradation, the decoder needs to perform more decoding iterations to reach the desired performance. This, in turn, increases the decoder latency and reduces the decoder throughput. One approach to improve the decoder throughput is to layout more parallel CNUs inside a decoder, but this offsets the advantage of the min-sum implementation. On the other hand, the performance of the min-sum algorithm can be improved by scaling the node-to-check messages and it is possible to find optimal scaling factor for a given channel. In this paper, we propose an improvement to the min-sum algorithm based on the analysis of the error term in the min-sum algorithm. The proposed algorithm achieves the performance similar to the scaled min-sum (SMS) approach with optimal scaling, in the additive white Gaussian noise (AWGN) channel. We also show min-sum utilized with different fading channels and LDPC codes without any further adjustments. Thus, the proposed MMS algorithm provides flexibility in real applications, which need to support multiple code rates, block sizes and have to operate in unknown fading channels. The performance of the proposed a- - lgorithm is evaluated for the MB-OFDM UWB systems with short distance indoor channel models. To meet the speed requirement of the of the UWB systems, a bit-level pipelined comparator is developed, which significantly reduces the latency of the critical path in the comparison circuit View full abstract»

This paper reports on the successful development of an efficient method of the power consumption reducing without recourse either to cooling or to transistor periphery scaling. An approach proposed is based on applying the field-effect transistor (FET) having (initially, in saturated I-V region) an excessive-high cut-off-frequency and sacrificing their gain after changing to linear I-V region. Discussions of the theoretical grounding and experimental results of the implementation of this method to the design of low-noise amplifiers (LNAs) for radiofrequency (RF) as well as microwave bands, are discussed. View full abstract»

For a network canceler, whose input is mainly speech, the proportionate affine projection algorithm (PAPA) is expected to present faster convergence speed than the existing proportionate NLMS algorithms. However, the performance criteria of fast convergence speed conflicts with low steady-state misalignment when a constant step-size parameter is applied. In this article we introduce a variable step-size technique into the PAPA in order to achieve both fast convergence speed and low steady-state misalignment. Simulation results show that the proposed approach can greatly improve the steady-state misalignment without sacrificing the fast convergence speed of the PAPA. View full abstract»

We report a series of experiments about how we can progress from Modern Standard Arabic (MSA) to Levantine ASR, in the context of the GALE DARPA program. While our GALE models achieved very low error rates, we still see error rates twice as high when decoding dialectal data. In this paper, we make use of a state-of-the-art Arabic dialect recognition system to automatically identify Levantine and MSA subsets in mixed speech of a variety of dialects including MSA. Training separate models on these subsets, we show a significant reduction in word error rate over using the entire data set to train one system for both dialects. During decoding, we use a tree array structure to mix Levantine and MSA models automatically using the posterior probabilities of the dialect classifier as soft weights. This technique allows us to mix these models without sacrificing performance for either varieties. Furthermore, using the initial acoustic-based dialect recognition system's output, we show that we can bootstrap a text-based dialect classifier and use it to identify relevant text data for building Levantine language models. Moreover, we compare different vowelization approaches when transitioning from MSA to Levantine models. View full abstract»

In this paper, we design capacity-approaching codes for partial response channels. The codes are constructed as concatenations of inner trellis codes and outer low-density parity- check (LDPC) codes. Unlike previous constructions of trellis codes for partial response channels, we disregard any algebraic properties (e.g., the minimum distance or the run-length limit) in our design of the trellis code. Our design is purely probabilistic in that we construct the inner trellis code to mimic the transition probabilities of a Markov process that achieves a high (capacity-approaching) information rate. Hence, we name it a matched information rate (MIR) design. We provide a set of five design rules for constructions of capacity-approaching MIR inner trellis codes. We optimize the outer LDPC code using density evolution tools specially modified to fit the superchannel consisting of the inner MIR trellis code concatenated with the partial response channel. Using this strategy, we design degree sequences of irregular LDPC codes whose noise tolerance thresholds are only fractions of a decibel away from the capacity. Examples of code constructions are shown for channels both with and without spectral nulls. View full abstract»

The discontinuous coverage of picocells causes the increased registration signaling overhead in the picocell/macrocell network where the dense picocells overlapped with a macrocell are partitioned into small Tracking Areas (TAs). The approach known as Delay Registration (DR) algorithm is proposed for overhead reduction with the expense of sacrificing the traffic offloading capability of the picocell in such case. However, its feasibility is greatly restricted because its effective implementation requires the accurate estimation of the mobile station (MS) information. We design a new scheme to enable both the low signaling cost location update without the complicated information estimation and the traffic offloading using the inter-cell handover. The theoretical analysis and the simulation experiments are conducted for the performance evaluation. The results show that our solution is superior to the DR algorithm in reducing the signaling cost while achieving the better adaptability to the high and diverse mobility environment. View full abstract»

This paper describes an approach to low level image noise reduction which uses non-linear comparisons to define which parts of the image are closely related to each individual pixel, i.e. what the local smoothing neighbourhood is. The resulting method achieves good smoothing without degrading edges, lines or corners in the image. It is also investigated for its multi-scale properties, and shown to give very little shift in edge position over multiple smoothing scales View full abstract»

Excerpt from the Preface The principal motivation for this work arose from the obvious desirability of finding a single quantity, a tag so to speak, to describe the noise performance of a two-terminal-pair amplifier. The possibility of the existence of such a quantity and even the general functional form which it might be expected to take were suggested by previous work of one of the authors on microwave tubes and their noise performance. This work showed that noise parameters of the electron beam set an ultimate limit to the entire noise performance of the amplifier that employed the beam. In the microwave tube case, however, the findings were based heavily upon the physical nature of the electron beam, and it was not immediately clear that a general theory of noise performance for any linear amplifier could be made without referring again to some detailed physical mechanism. In order to detach the study of noise performance from specific physical mechanisms, one had to have recourse to general circuit theory of active networks. Such a theory had grown up around the problems associated with transistor amplifiers, and important parts of it were available to us through the association of one of us with Professor S. J. Mason. This combination of circumstances led to the collaboration of the authors.Two major guiding principles, or clues, could be drawn from the experience on microwave tubes. One such clue was the general form of the probable appropriate noise parameter. The other was the recognition that matrix algebra and a proper eigenvalue formulation would be required in order to achieve a general theory without becoming hopelessly involved in algebraic detail.Essentially by trial and error, guided by some power-gain theorems in active circuit theory, we first found a few invariants of noisy networks. Afterward, while we were trying to decide around which quantities we should build a matrix-eigenvalue formulation leading to these same invariants, we were aided by the fact that Mr. D. L. Bobroff recognized a connection between the invariants which we had found and the problem of the available power of a multiterminal-pair network.Armed with this additional idea, we consulted extensively with Professor L. N. Howard of MIT's Department of Mathematics, in search of the appropriate matrix-eigenvalue problem. As a result of his suggestions, we were able to reach substantially the final form of the desired formulation.Once the proper eigenvalue approach was found, additional results and interpretations followed rapidly. In particular, the idea that the eigenvalue formulation should be associated with a canonical form of the noisy network was suggested in a conversation with Proessor Shannon.One of the principal results of the work is that it furnishes a single number, or tag, which may be said to characterize the amplifier noise performance on the basis of the signal-to-noise-ratio criterion. The novel features of this tag are two in number: First, it clears up questions of the noise performance of low-gain amplifiers or of the effect upon noise performance of degenerative feedback; second, it provides for the first time a systematic treatment of the noise performance of negative-resistance amplifiers. The latter results were not expected in the original motivation for the study but grew from insistent demands upon the internal consistency of the theory. It is interesting that the negative-resistance case will probably turn out to be one of the most important practical results of our work.Another result worth mentioning here, however, is the canonical form of linear noisy networks. This form summarizes in a clear, almost visual, manner the connection between the internal noise of a network at any particular frequency and its (resistive, positive, or negative) part. View full abstract»

Mainstream approaches to content-based distributed publish-subscribe typically route events deterministically based on information collected from subscribers, and do so by relying on a tree-shaped overlay network. While this solution achieves scalability in fixed, large-scale settings, it is less appealing in scenarios characterized by high dynamicity, e.g., mobile ad hoc networks or peer-to-peer systems. At the other extreme, researchers in the related fields of multicast and group communication have successfully exploited probabilistic techniques that provide increased fault tolerance, resilience to changes, and yet are scalable. In this paper, we propose a novel approach where event routing relies on deterministic decisions driven by a limited view on the subscription information and, when this is not sufficient, resorts to probabilistic decisions performed by selecting links at random. Simulations show that the particular mix of deterministic and probabilistic decisions we put forth in this work is very effective at providing high event delivery and low overhead in highly dynamic scenarios, without sacrificing scalability View full abstract»

This paper takes an in-depth look at a technique for computing filtered matrix-vector (mat-vec) products which are required in many data analysis applications. In these applications, the data matrix is multiplied by a vector and we wish to perform this product accurately in the space spanned by a few of the major singular vectors of the matrix. We examine the use of the Lanczos algorithm for this purpose. The goal of the method is identical with that of the truncated singular value decomposition (SVD), namely to preserve the quality of the resulting mat-vec product in the major singular directions of the matrix. The Lanczos-based approach achieves this goal by using a small number of Lanczos vectors, but it does not explicitly compute singular values/vectors of the matrix. The main advantage of the Lanczos-based technique is its low cost when compared with that of the truncated SVD. This advantage comes without sacrificing accuracy. The effectiveness of this approach is demonstrated on a few sample applications requiring dimension reduction, including information retrieval and face recognition. The proposed technique can be applied as a replacement to the truncated SVD technique whenever the problem can be formulated as a filtered mat-vec multiplication. View full abstract»

We present in this paper a current mediated active pixel sensor (APS) with variable image size and resolution for power saving, electronic zooming, and data reduction at the sensor level. The circuit can perform averaging of output signals in blocks of adjacent pixels (kernels) of size 1×1, 2×2 and 4×4, allowing data reduction without aliasing effects. To achieve this, a current approach is used, thus enabling high speed operation and low power supply capacity. A novel fixed pattern noise (FPN) reduction scheme using a compact circuitry is presented. The circuit compensates for pixel transconductance mismatch in addition to offset error via analog to digital conversion reference current scaling. Hspice simulations using parameters of a 0.35 μm CMOS process illustrate the advantage of the new technique over usual correlated double sampling (CDS) in current mode sensors. Parallel integrated analog to digital converters (ADC), a data line-buffer and digital control complete the circuit making data transmission easy and simplifying hardware needed for using the image sensor View full abstract»