Target Error Rate Research Articles

Optimal implementation of novel WCDMA uplink outer loop power control algorithm

Wideband code division multiple access (WCDMA) uplink outer loop power control has been responsible for changing the signal to interference ratio (SIR) target value according to the SIR target control algorithms. Thus maintains the desired block error rate (BLER) for voice connections and transmission to target error rate (TTE) for data connections. During a call, the SIR target varies between implemented lower (sirMin) and upper boundaries (sirMax), which are fixed values on radio network control station (RNC). As possible solution for WCDMA uplink overload problems, a novel uplink outer loop power control algorithm with dynamic change of sirMax has been proposed. In this paper optimal implementation for dynamic change of sirMax has been investigated. Performance management statistic and general performance event handling (GPEH) data, for current uplink received signal strength indicator (UL RSSI) and required SIR target, have been obtained. Based on analysis from obtained data optimal implementation for dynamic change of sirMax has been proposed.

I/Q-Imbalance Self-Interference Coordination

In this paper, we present a novel low-complexity scheme, which improves the performance of single-antenna multi-carrier communication systems, suffering from in-phase and quadrature (I/Q)-imbalance (IQI) at the receiver. We refer to the proposed scheme as I/Q-imbalance self-interference coordination (IQSC). IQSC does not only mitigate the detrimental effects of IQI, but, through appropriate signal processing, also coordinates the self-interference terms produced by IQI in order to achieve second-order frequency diversity. However, these benefits come at the expense of a reduction in transmission rate. More specifically, IQSC is a simple transmit diversity scheme that improves the signal quality at the receiver by elementary signal processing operations across symmetric (mirror) pairs of subcarriers. Thereby, the proposed transmission protocol has a similar complexity as Alamouti's space-time block coding scheme and does not require extra transmit power nor any feedback. To evaluate the performance of IQSC, we derive closed-form expressions for the resulting outage probability and symbol error rate. Interestingly, IQSC outperforms not only existing IQI compensation schemes but also the ideal system without IQI for the same spectral efficiency and practical target error rates, while it achieves almost the same performance as ideal (i.e., IQI-free) equal-rate repetition coding. Our findings reveal that IQSC is a promising low-complexity technique for significantly increasing the reliability of low-cost devices that suffer from high levels of IQI.

동일대역 전이중 방식 통신 시스템에서 자기간섭 제거에 따른 성능 분석

본 논문은 자기간섭 (self-interference, SI) 신호가 존재하는 환경에서 동일대역 전이중 방식 통신 시스템의 성능과 SI 제거 기법에 대해서 분석하였다. 동일대역 전이중 방식 통신 시스템이 원하는 오율 성능을 달성하기 위해서는 SI 신호를 제거해야 하며, 이는 전파 영역과 아날로그 영역, 디지털 영역에서 차례로 수행되어야 한다. 전파 영역에서 안테나의 송수신 빔을 물리적으로 분리시켜서 신호 감쇄를 달성할 수 있다. 아날로그 영역과 디지털 영역에서는 SI 신호의 채널 추정값과 송신 신호를 기반으로 SI 신호를 재생한 후에 원하는 수신 신호로부터 제거할 수 있다. 본 논문에서는 전파 영역에서의 SI 신호를 충분히 감쇄시킬 수 있다고 가정하고, Least squares 방식으로 SI 신호의 채널을 추정하고 그 추정값을 기반으로 아날로그 영역과 디지털 영역에서 SI 신호를 순차적으로 제거하여 동일대역 전이중 방식 통신 시스템이 원하는 오율 성능을 달성할 수 있음을 확인하였다. In this paper, we analyze performances of in-band full-duplex communication system and self-interference (SI) suppression methods in environment where there exists the SI signal. The SI has to be removed to achieve required error rate performance of the system in order - propagation domain, analog domain and digital domain. In propagation domain, the SI signal is attenuated by separating transmitted and received beams physically. In analog and digital domain, after reconstruction of the SI signal using channel estimates and transmit signal, the SI signal can be cancelled from the desired signal. In this paper, assuming that the SI signal can be sufficiently reduced in propagation domain, we demonstrate that the in-band full-duplex communication system can achieve the target error rate by suppressing the SI signal in order - analog and digital domain, based on channel estimates that can be obtained by the method of Least squares.

Optimization of Multimedia Progressive Transmission Over MIMO Channels

This paper studies the optimal transmission of multimedia progressive sources, which require unequal target error rates in their bitstream, over multiple-input–multiple-output (MIMO) channels. First, we derive the information outage probability expression of a space–time code for an arbitrarily given piecewise-linear diversity–multiplexing tradeoff (DMT) function and the conditions for the existence of a crossover point of the information outage probability curves of the space–time codes. We prove that as long as the crossover point of the outage probabilities exists, as spectral efficiency increases, the crossover point in the signal-to-noise ratio (SNR) monotonically increases, whereas that of the outage probability monotonically decreases. This analysis can be applied to any space–time code, receiver, and propagation channel with a given DMT function. As a specific example, we analyze the two-layer diagonal Bell Labs space–time architecture (D-BLAST) with a group zero-forcing receiver, the vertical BLAST (V-BLAST) with a minimum mean-square error receiver, and orthogonal space–time block codes (OSTBCs), and prove the monotonic behavior of the crossover point for those codes. Based on that, with respect to D-BLAST, V-BLAST, and OSTBC, we derive a method for the optimal space–time coding of a sequence that contains numerous progressive packets. We show that by employing the optimization method rather than exhaustive search, the computational complexity involved with optimal space–time coding can be exponentially reduced without losing any peak SNR performance.

On Reducing Power Consumption of Transmitting Stations in 802.11 MIMO Networks

We propose an online algorithm for energy minimization of transmitting stations in IEEE 802.11 wireless local area networks (WLANs). Our algorithm configures radio frequency (RF) parameters such as the number of transmitting antennas based on the real-time traffic demand and channel condition so that the power consumption of the device is reduced, and the minimum data rate requirements of the stations at a target error rate are satisfied. The process of the transition between different RF configurations is investigated by employing a two-dimensional Markov chain model. Using an IEEE 802.11ac hardware testbed, we experimentally demonstrate that with our algorithm the power consumption of a transmitting station can be reduced upto 33%. We also validate that the experimental result and the simulation result obtained with our Markov model closely match.

RS-LDPC Concatenated Coding for the Modern Tape Storage Channel

In modern tape storage, user data are recorded and retrieved along multiple tracks of rapidly moving, flexible magnetic medium that give rise to a variety of channel impediments including occasional long erasures, more frequent amplitude fades as well as a large amount of random errors. This work considers reliable recovery of data from such tape channels using a novel concatenation of an inner Reed-Solomon (RS) code and an outer nonbinary low-density parity-check (LDPC) code. This particular concatenation scheme and a highly tailored iterative decoding algorithm are chosen to efficiently handle the assortment of the tape channel impediments while meeting the stringent target error rate constraint as well as key practical requirements of the mass tape storage system. Despite the use of a nonbinary LDPC code, the proposed scheme allows excellent performance-complexity tradeoffs. In stark contrast to any existing coding schemes that involve LDPC codes, the proposed concatenation strategy allows semianalytic error rate performance evaluation at rates below what is possible using modern computers, thus providing an ability to ensure satisfactory low-error-rate performance.

A Rescue Strategy for Handling Unevaluable Patients in Simon's Two Stage Design.

For phase II oncology trials, Simon’s two-stage design is the most commonly used strategy. However, when clinically unevaluable patients occur, the total number of patients included at each stage differs from what was initially planned. Such situations raise concerns about the operating characteristics of the trial design. This paper evaluates three classical ad hoc strategies and a novel one proposed in this work for handling unevaluable patients. This latter is called the rescue strategy which adapts the critical stopping rules to the number of unevaluable patients at each stage without modifying the planned sample size. blue Simulations show that none of these strategies perfectly match the original target constraints for type I and II error rates. Our rescue strategy is nevertheless the one which best approaches the target error rates requirement. A re-analysis of one real phase II clinical trials on metastatic cancer illustrates the use of the proposed strategy.

SECRET

DRAMs are used as the main memory in most computing systems today. Studies show that DRAMs contribute to a significant part of overall system power consumption. One of the main challenges in low-power DRAM design is the inevitable refresh process. Due to process variation, memory cells exhibit retention time variations. Current DRAMs use a single refresh period determined by the cell with the largest leakage. Since prolonging refresh intervals introduces retention errors, a set of previous works adopt conventional error-correcting code (ECC) to correct retention errors. However, these approaches introduce significant area and energy overheads. In this article, we propose a novel error correction framework for retention errors in DRAMs, called SECRET (selective error correction for refresh energy reduction). The key observations we make are that retention errors are hard errors rather than soft errors, and only few DRAM cells have large leakage. Therefore, instead of equipping error correction capability for all memory cells as existing ECC schemes, we only allocate error correction information to leaky cells under a refresh interval. Our SECRET framework contains two parts: an offline phase to identify memory cells with retention errors given a target error rate and a low-overhead error correction mechanism. The experimental results show that among all test cases performed, the proposed SECRET framework can reduce refresh power by 87.2% and overall DRAM power up to 18.57% with negligible area and performance overheads.

A Controlled Sensing Approach to Graph Classification

The problem of classifying graphs with respect to connectivity via partial observations of nodes is posed as a composite hypothesis testing problem with controlled sensing. An observation at a node is a subset of edges incident to the node on the complete graph drawn according to a probability model, which is a function of a fixed underlying graph. Connectivity is measured through average node degree and is classified with respect to a threshold. A simple approximation of the controlled sensing test is derived and simulated on Erdös-Rènyi graphs to characterize the error probabilities as a function of the expected stopping times. The test is also experimentally validated on a real-world example of the social structure of Long-Tailed Manakins. It is shown that the proposed test achieves favorable tradeoffs between the classification error and the number of measurements. Furthermore, the test outperforms existing approaches, especially at low target error rates. In addition, the proposed test achieves the optimal error exponent.

Optimal Transmission of Progressive Sources Based on the Error Probability Analysis of SM and OSTBC

This paper studies the optimal design of multimedia progressive communication systems that are combined with low-complex open-loop multiple-input multiple-output techniques. First, we analyze the behavior of the crossover point of the error probability curves for orthogonal space-time block codes (OSTBC) and spatial multiplexing (SM) with a zero-forcing linear receiver. We mathematically prove that, in the high signal-to-noise ratio (SNR) regime, for both the information outage probability and the uncoded bit error rate, as data rate increases, the crossover point for the error probability monotonically decreases, and the crossover point for the SNR monotonically increases. We prove that this holds, regardless of the numbers of transmit and receive antennas and the spatial multiplexing rate of OSTBC. We next show how those results can be exploited for the optimal transmission of progressive sources, such as embedded image, which require unequal target error rates in their bitstream. That is, the computational complexity involved with the optimal space-time coding of progressive bitstream can be decreased.

RS-Enhanced TCM for Multilevel Flash Memories

Multilevel flash memories store more than one bit per storage cell and are further characterized by large word (page) sizes and very low target error rates. In this paper, a high-rate error control scheme is presented that uses inner trellis-coded modulation (TCM) for storing two bits per cell with five possible charge levels. The coded subset-label bits and the uncoded signal-label bits of TCM are independently protected by separate outer Reed-Solomon (RS) codes. The resulting scheme permits multistage decoding. Errors made by the TCM decoder in the subset-label bits occur in bursts and are corrected by the associated first RS decoder prior to determining signal-label bits and correcting errors in those bits by the associated second RS decoder. The multi-stage decoding avoids the significant spread of errors from subset-label bits into the generally larger number of signal-label bits which is typical for conventional serial RS-TCM concatenation when the inner TCM system operates at relatively low SNR. The error performance of the proposed scheme is evaluated at low error rates by a mixed simulation-analytic method. It is shown that the proposed scheme exhibits highly favorable performance vs. complexity tradeoffs compared to the other schemes.

Adaptive bit loading for multi-relay cooperative orthogonal frequency division multiple with imperfect channel estimation

In this study, the authors introduce an adaptive bit loading scheme for an amplify-and-forward orthogonal frequency division multiple cooperative system with relay selection. The proposed bit loading scheme maximises the throughput for a target error rate taking into account the quality of imperfect channel estimation. It relies on estimated channel state information (CSI) at the destination node and partial CSI (which involves the number of loaded bits) at the source node. The authors provide extensive Monte Carlo simulation results to demonstrate the throughput and the no-transmission probability performance of the proposed scheme and discuss the effect of various system and channel parameters on the performance.

Joint iterative algorithm for optimal cooperative spectrum sensing in cognitive radio networks

In this paper, joint optimization of throughput and error rate via cooperative spectrum sensing in cognitive radio networks is investigated. An optimization problem is formulated, which aims to maximize the average achievable throughput of cooperating cognitive users while keeping the error rate at a lower level. This is a multi-variable nonconvex optimization problem. Instead of solving it directly, we propose an iterative algorithm which jointly optimizes the threshold and sensing time together to decrease the effect of the error and to increase the achievable throughput. We first prove that the local error rate of the cognitive user is a convex function of energy threshold and determine a closed-form for the optimal threshold which minimizes the error rate. Then we show that the AND rule is the optimal fusion rule to maximize the achievable throughput. Furthermore we determine the least number of cooperating cognitive users that can guarantee a minimum target error rate. This initial nonconvex problem is converted into a single variable convex optimization problem which can be successfully solved by common methods e.g. Newton’s method. Simulation results illustrate the fast convergence and effectiveness of the joint iterative algorithm.

Differential Fade Margin and Handoff Gain in Wireless Cellular Networks

Communication links in a wireless cellular network are subject to random slow fading. Thus a link margin is required to guarantee a certain level of link reliability. It is well known that the required link margin is reduced due to mobile handoff at the cell edge. This is the handoff gain. Traditionally the handoff gain considers only the reduction of the link margin requirement due to the presence of multiple random slow fading paths; the error rate requirement is not taken into account. However, in the case of soft handoffs, when multiple links are available to the receiver simultaneously, for a given target overall error rate, a higher error rate target per link is allowed. This increases the handoff gain, but the possibility of imbalance at the handoff links requires an additional margin. This is the differential fade margin, which reduces the handoff gain. We show how to numerically calculate the differential fade margin and the overall handoff gain without resorting to simulations. Several illustrative examples are given. The approach is used to show that the benefit of being able to allow a higher per link error rate in the soft handoff far outweighs the drawback of requiring the additional differential fade margin. We show that the soft handoff gain is more than 3 dB higher than the traditional soft handoff gain widely used in the radio frequency (RF) design community. This approach also allows us to quantify the link budget gain when the target error rate is relaxed. In addition to quantifying the gains in theoretical Gaussian and Rayleigh channels, we have also shown that in CDMA2000 3G1× systems, regardless of whether the carrier frequency band is at 1900 MHz (PCS), 850 MHz (cellular), or 450 MHz, relaxing the target frame error rate (FER) from one percent to two percent provides a 1 dB gain in the link budget, while relaxing the target FER from one percent to five percent provides a 2 dB gain in the link budget. © 2012 Alcatel-Lucent.

Performance Analysis of Triangular Quadrature Amplitude Modulation in AWGN Channel

Recently, the triangular quadrature amplitude modulation (TQAM) whose signal points are regularly distributed at the vertexes of contiguous equilateral triangles was proposed. In this paper, we derive the general formula calculating the average energy per symbol of the TQAM and find out that the asymptotic power gain of the TQAM over the well-known square quadrature amplitude modulation (SQAM) is 0.5799 dB. We also analyze the symbol error rate (SER) and the bit error rate (BER) of the TQAM and compare them with the error performances obtained through computer simulation. Analytical and simulation results coincide at a wide range of signal to noise power ratio (SNR). The power gain increases gradually and approaches the asymptotic value as modulation order increases and target error rate decreases.

Recovery-Driven Design: Exploiting Error Resilience in Design of Energy-Efficient Processors

Conventional computer-aided design (CAD) methodologies optimize a processor module for correct operation and prohibit timing violations during nominal operation. We propose recovery-driven design, a design approach that optimizes a processor module for a target timing error rate (ER) instead of correct operation. The target ER is chosen based on how many errors can be gainfully tolerated by a hardware or software error resilience mechanism. We show that significant power benefits are possible from a recovery-driven design approach that deliberately allows errors caused by voltage overscaling to occur during nominal operation, while relying on an error resilience technique to tolerate these errors. We present a detailed evaluation and analysis of such a CAD methodology that minimizes the power of a processor module for a target ER. We show how this design-level methodology can be extended to design recovery-driven processors-processors that are optimized to take advantage of hardware or software error resilience. We also discuss a gradual slack recovery-driven design approach that optimizes for a range of ERs to create soft processors-processors that have graceful failure characteristics and the ability to trade throughput or output quality for additional energy savings over a range of ERs. We demonstrate significant power benefits over conventional design-11.8% on average over all modules and ER targets, and up to 29.1% for individual modules. Processor-level benefits were 19.0%, on average. Benefits increase when recovery-driven design is coupled with an error resilience mechanism or when the number of available voltage domains increases.

Research of Soccer Robot Target Tracking Algorithm Based on Improved CAMShift

According to the vision needs of robot soccer and CAMShift tracking inefficient in dynamic background, a new tracking algorithm is brought forward to improve the CAMShift in this paper. A real-time updating background model is build, by traversing the search area for all target pixels to statistic and calculate the color probability distribution of the color target, statistical principles and minimum error rate of Bayesian decision theory are used to achieve a more accurate distinction between the target and the background. By comparing with the CAMShift, the new algorithm provides a better robustness in the soccer robot game and can meet the purposes of fast and accurate tracking.

Finding All Small Error-Prone Substructures in LDPC Codes

It is proven in this work that it is NP-complete to exhaustively enumerate small error-prone substructures in arbitrary, finite-length low-density parity-check (LDPC) codes. Two error-prone patterns of interest include stopping sets for binary erasure channels (BECs) and trapping sets for general memoryless symmetric channels. Despite the provable hardness of the problem, this work provides an exhaustive enumeration algorithm that is computationally affordable when applied to codes of practical short lengths <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> ap 500. By exploiting the sparse connectivity of LDPC codes, the stopping sets of size <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">les</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">13</i> and the trapping sets of size <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">les11</i> can be exhaustively enumerated. The central theorem behind the proposed algorithm is a new provably tight <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">upper</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">bound</i> on the error rates of iterative decoding over BECs. Based on a tree-pruning technique, this upper bound can be iteratively sharpened until its asymptotic order equals that of the error floor. This feature distinguishes the proposed algorithm from existing non-exhaustive ones that correspond to finding <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">lower</i> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">bounds</i> of the error floor. The upper bound also provides a worst case performance guarantee that is crucial to optimizing LDPC codes when the target error rate is beyond the reach of Monte Carlo simulation. Numerical experiments on both randomly and algebraically constructed LDPC codes demonstrate the efficiency of the search algorithm and its significant value for finite-length code optimization.

Artificial Neural Network-Based Glaucoma Diagnosis Using Retinal Nerve Fiber Layer Analysis

To develop, train, and test an artificial neural network (ANN) for differentiating among normal subjects, primary open angle glaucoma (POAG) suspects, and persons with POAG in Asian-Indian eyes using inputs from clinical parameters, optical coherence tomography (OCT), visual fields, and GDx nerve fiber analyzer. One hundred eyes were classified using optic disc examination and perimetry into normal (n=35), POAG suspects (n=30), and POAG (n=35). EasyNN-plus simulator was used to develop an ANN model with inputs including age, sex, myopia, intraocular pressure (IOP), optic nerve head, and retinal nerve fiber layer (RNFL) parameters on OCT, Octopus 30-2 full threshold visual field, and GDx parameters. With two outputs (POAG or normal), specificity was 80% and sensitivity was 93.3%. Ninety percent of POAG suspects were labeled as abnormal in this analysis. ANN assigned the highest importance to Smax/Imax RNFL on OCT followed by cup-area (OCT) and other RNFL parameters (OCT) for two outputs. With three outputs (normal, POAG, and POAG suspect), ANN gave an overall classification rate of 65%, specificity of 60%, and sensitivity of 71.4% with a target error rate of the training set at 1%. The parameters for three outputs, in decreasing order of relative importance, were Savg, vertical cup-disc ratio, cup-volume, and cup-area on OCT. An ANN taking varied diagnostic imaging inputs was able to separate POAG eyes from normal subjects and POAG suspects. The network had reasonable sensitivity with three outputs; however, it had a tendency to mislabel POAG suspects as POAG.

Energy-efficiency and transmission strategy selection in cooperative wireless sensor networks

Energy efficiency is one of the most critical concerns for wireless sensor networks. By allowing sensor nodes in close proximity to cooperate in transmission to form a virtual multiple-input multiple-output (MIMO) system, recent progress in wireless MIMO communications can be exploited to boost the system throughput, or equivalently reduce the energy consumption for the same throughput and BER target. However, these cooperative transmission strategies may incur additional energy cost and system overhead. In this paper, assuming that data collectors are equipped with antenna arrays and superior processing capability, energy efficiency of relevant traditional and cooperative transmission strategies: Single-input-multiple-output (SIMO), space-time block coding (STBC), and spatial multiplexing (SM) are studied. Analysis in the wideband regime reveals that, while receive diversity introduces significant improvement in both energy efficiency and spectral efficiency, further improvement due to the transmit diversity of STBC is limited, as opposed to the superiority of the SM scheme especially for non-trivial spectral efficiency. These observations are further confirmed in our analysis of more realistic systems with limited bandwidth, finite constellation sizes, and a target error rate. Based on this analysis, general guidelines are presented for optimal transmission strategy selection in system level and link level, aiming at minimum energy consumption while meeting different requirements. The proposed selection rules, especially those based on system-level metrics, are easy to implement for sensor applications. The framework provided here may also be readily extended to other scenarios or applications.