nils-herrmann/clean_scirepeval huggingface dataset:
Optimal OFDMA Resource Allocation with Linear Complexity to Maximize Ergodic Weighted Sum Capacity

Previous research efforts to optimize OFDMA resource allocation with respect to communication performance have focused on formulations considering only instantaneous per-symbol rate maximization, and on solutions using suboptimal heuristic algorithms. This paper intends to fill gaps in the literature through two key contributions. First, we formulate weighted sum ergodic capacity maximization in OFDMA assuming the availability of perfect channel state information (CSI). Our formulations exploit time, frequency, and multi-user diversity, while enforcing various notions of fairness through weighting factors for each user. Second, we derive algorithms based on a dual optimization framework that solve the OFDMA ergodic capacity maximization problem with O (MK) complexity per OFDMA symbol for M users and K subcarriers, while achieving data rates shown to be at least 99.9999% of the optimal rate in simulations based on realistic parameters. Hence, this paper attempts to demonstrate that OFDMA resource allocation problems are not computationally prohibitive to solve optimally, even when considering ergodic rates.
Robust transceiver to combat periodic impulsive noise in narrowband powerline communications

Non-Gaussian noise/interference severely limits communication performance of narrowband powerline communication (PLC) systems. Such noise/interference is dominated by periodic impulsive noise whose statistics varies with the AC cycle. The periodic impulsive noise statistics deviate significantly from that of additive white Gaussian noise, thereby causing dramatic performance degradation in conventional narrowband PLC systems. In this paper, we propose a robust transmission scheme and corresponding receiver methods to combat periodic impulsive noise in OFDM-based narrowband PLC. Towards that end, we propose (1) a time-frequency modulation diversity scheme at the transmitter and a diversity demodulator at the receiver to improve communication reliability without decreasing data rates; and (2) a semi-online algorithm that exploits the sparsity of the noise in the frequency domain to estimate the noise power spectrum for reliable decoding at the diversity demodulator. In the simulations, compared with a narrowband PLC system using Reed-Solomon and convolutional coding, whole-packet interleaving and DBPSK/BPSK modulation, our proposed transceiver methods achieve up to 8 dB gains in Eb/N0 with convolutional coding and a smaller-sized interleaver/deinterleaver.
A Mostly Digital PWM-Based $\Delta\Sigma$ ADC With an Inherently Matched Multibit Quantizer/DAC

A mostly digital pulsewidth-modulator-based delta-sigma (ΔΣ) analog-to-digital converter is proposed. This system takes advantage of the duration of pulses, rather than voltage or current, as the analog operand used in its closed-loop operation. Therefore, circuits that process the pulses are digital in nature and improve with scaling. Furthermore, the architecture allows inherently matched multibit quantizer/digital-to-analog converter (DAC) blocks by taking advantage of delay lines reusable in both quantization and DAC operation. A second novelty of this architecture is the modulator's adaptive excess delay, which synchronizes the asynchronous loop with an external reference clock. This mitigates the problems associated with nonuniform sampling. A first-order 3-b prototype of this architecture is presented. The core occupies an area of 0.0275 mm2 in a 0.18-μm CMOS process, consumes 2.7 mW, and measures a 45.1-dB SNR over a 2-MHz bandwidth.
Characterizing Decentralized Wireless Networks with Temporal Correlation in the Low Outage Regime

Communication in decentralized wireless networks is limited by interference. Because transmissions typically last for more than a single contention time slot, interference often exhibits a strong statistical dependence over time that results in temporally correlated communication performance. The temporal dependence in interference increases as user mobility decreases and/or the total transmission time increases. We propose a network model that spans the extremes of temporal independence to long-term temporal dependence. Using the proposed model, closed-form single hop communication performance metrics are derived that are asymptotically exact in the low outage regime. The primary contributions are (i) deriving the joint temporal statistics of network interference and showing that it follows a multivariate symmetric alpha stable distribution; (ii) utilizing the joint interference statistics to derive closed-form expressions for local delay, throughput outage probability, and average network throughput; and (iii) using the joint interference statistics to redefine and analyze the network transmission capacity that captures the throughput-delay-reliability tradeoffs in single hop transmissions. Simulation results verify the closed-form expressions derived in this paper and we demonstrate up to 2× gain in network throughput and reliability by optimizing certain parameters of medium access control layer protocol in view of the temporal correlations.
Inferring path sharing based on flow level TCP measurements

We develop methods to infer path or bottleneck sharing among TCP flow classes based on flow level measurements available from the current traffic monitoring tools. Our premise is that flows that temporally overlap on the congested resources have correlated throughputs. We propose to use factor analysis to explore the correlation structure of flow class throughputs in order to hypothesize which flow classes might share congested resources. The effectiveness of this "black box" approach is studied using the empirical data. We show that making such inferences based on flow level statistics is viable in practice, and can serve as an effective, novel tool for network design and configuration decisions. Our work on inferring bottleneck sharing differs significantly from the previous work in that we consider flow level instead of packet level statistics, and hence may potentially influence research in that area. Possible applications of this technique include network monitoring and root cause analysis of poor performance.
Tuning JPEG2000 image compression for graphics regions

The new image compression standard, JPEG2000, provides higher compression rates for the same visual quality for grayscale and color images than JPEG. JPEG2000 is being adopted for image compression and transmission, eg, in mobile telephones, PDA, and wearable computers. Depending on the application, images may contain formatted text and graphics data. For graphics images at the same low bit rates, graphics compression methods, such as the graphics interchange format (GIF) and portable network graphics (PNG), outperform JPEG2000 in visual quality. In this paper, we describe problems associated with compressing graphics data with JPEG2000, and propose modifications to a JPEG2000 encoder to minimize distortion for color graphics data by using a model of the human visual system. The visual improvements are quantified by a new measure of distortion.
Data wordlength reduction for low-power signal processing software

Reducing power consumption prolongs battery life and increases integration. In digital CMOS designs, switching activity is closely connected with the total power consumption. Switching activity on programmable processors implementing linear filters, fast Fourier transforms, and other signal processing operations is dominated by the hardware multiplier. In this paper, we employ wordlength reduction of multiplicands to reduce switching activity in hardware multipliers using truncation and signed right shift methods. For 32 bit /spl times/ 32 bit Wallace and radix-4 modified Booth multipliers, truncation by 16 bits achieves a 4:1 and 2:1 reduction, respectively, in switching activity, whereas signed right shift gives little or no reduction. The key contribution of this paper is the reduction of power consumption by altering multiplicands in software without any hardware modifications.
FPGA implementation of a message-passing OFDM receiver for impulsive noise channels

Conventional orthogonal frequency division multiplexing (OFDM) communication systems are typically designed assuming additive white Gaussian noise and interference statistics. However, in many applications, such as Wi-Fi and powerline communications (PLC), impulsive statistics are often observed. Impulsive noise can degrade the signal-to-noise ratio (SNR) of all subcarriers and impair communication performance. In this work, we design and implement a real-time OFDM receiver with approximate message passing (AMP) to estimate and mitigate impulsive noise. The goal is to meet throughput and latency requirements while guaranteeing improved communication performance in impulsive noise. Our contributions include (i) modeling functional parallelism in an AMP OFDM receiver in synchronous dataflow, (ii) converting an AMP OFDM PLC receiver to using only fixed-point data and arithmetic, and (iii) mapping the receiver in fixed-point onto a Field Programmable Gate Array (FPGA) target using a high-level graphical synthesis tool. Our FPGA OFDM transceiver testbed achieves full streaming throughput at G3-PLC rates and recovers up to 8 dB SNR of impulsive noise over a wide SNR range.
A voice-band audio processor IC for CDMA applications

A 2.7 V voice-band audio processor (VBAP/sup TM/) IC for CDMA wireless handsets as presented, The chip consists of transmit (uplink) and receive (downlink) audio channels and runs at a nominal current consumption of 9.1 mA. The transmit channel has two differential microphone inputs with external filtering and gain option for signal conditioning before a /spl Sigma//spl Delta/ ADC. The transmit channel pre-emphasis filter, receive channel filter, part of transmit gain, receive gain, receive volume control and sidetone gains are achieved by a single DSP core. The receive channel has a differential and a single-ended speaker interface which can deliver 35 mW and 10 mW to a 32 /spl Omega/ load respectively. The PCM encoding and decoding can be achieved in both linear and /spl mu/-law companded modes. Due to the PLL/clock recovery circuitry the 13-bit /spl Sigma//spl Delta/ voiceband codec is immune to system clock jitter up to 37%.
Fast rehalftoning and interpolated halftoning algorithms with flat low-frequency response

We present raster image processing algorithms for rehalftoning error diffused halftones and producing interpolated error diffused halftones. Rehalftoning converts a halftone created by one method into one created by another method. In interpolated halftoning, interpolation increases the image size before halftoning, e.g. for printing. Both rehalftoning and interpolated halftoning introduce blur and noise in the output image. To compensate for the blur, we use modified error diffusion, which has a variable gain parameter to control the sharpness. We derive optimal formulas for the sharpness control parameter to make the overall frequency response flat. The high-frequency noise is masked by error diffusion. The proposed algorithms yield halftones of high fidelity at a low computational cost.
Resolution-Adaptive Hybrid MIMO Architectures for Millimeter Wave Communications

In this paper, we propose a hybrid analog–digital beamforming architecture with resolution-adaptive ADCs for millimeter wave (mmWave) receivers with large antenna arrays. We adopt array response vectors for the analog combiners and derive ADC bit-allocation (BA) solutions in closed form. The BA solutions reveal that the optimal number of ADC bits is logarithmically proportional to the RF chain's signal-to-noise ratio raised to the  $1/3$ power. Using the solutions, two proposed BA algorithms minimize the mean square quantization error of received analog signals under a total ADC power constraint. Contributions of this paper include 1) ADC bit-allocation algorithms to improve communication performance of a hybrid MIMO receiver, 2) approximation of the capacity with the BA algorithm as a function of channels, and 3) a worst-case analysis of the ergodic rate of the proposed MIMO receiver that quantifies system tradeoffs and serves as the lower bound. Simulation results demonstrate that the BA algorithms outperform a fixed-ADC approach in both spectral and energy efficiency, and validate the capacity and ergodic rate formula. For a power constraint equivalent to that of fixed 4-bit ADCs, the revised BA algorithm makes the quantization error negligible while achieving 22% better energy efficiency. Having negligible quantization error allows existing state-of-the-art digital beamformers to be readily applied to the proposed system.
Joint space-time interference cancellation and channel shortening

In this paper, we present a framework for the design of space-time equalizers that perform joint interference cancellation and channel shortening in multi-user multiple-input multiple-output frequency-selective channels. The space-time filter coefficients and the shortened channel vectors are jointly optimized to minimize the interference-plus-noise using training data. The receiver design is completed by using an appropriate Viterbi equalizer in the second stage for inter-symbol interference equalization. The design is adapted to two different detection schemes- independent detection and ordered successive interference cancellation. Simulation results have shown acceptable symbol error performance with both detection schemes.
Efficient dual-tone multifrequency detection using the nonuniform discrete Fourier transform

The International Telecommunication Union (ITU) recommendations for dual-tone multifrequency (DTMF) signaling are not met by conventional DTMF detectors. We present an efficient DTMF detection algorithm based on the nonuniform discrete Fourier transform that meets all of the ITU recommendations. The key innovations are the use of two sliding windows and development of sophisticated timing tests. Our algorithm requires no buffering of input samples. To perform DTMF detection on n telephone channels, our algorithm requires approximately n MIPS on a digital signal processor (DSP), 75+30n words of data memory, and 1000 words of program memory. Using the new algorithm, a single fixed-point DSP can perform ITU-compliant DTMF detection on the 24 telephone channels of a T1 time-division multiple multiplexed telecommunications line.
Online calibration and synchronization of cellphone camera and gyroscope

Gyroscope is playing a key role in helping estimate camera rotation during mobile video capture. The fusion of gyroscope and visual measurements needs the knowledge of camera projection parameters, the gyroscope bias and the relative orientation between gyroscope and camera. Moreover, the timestamps of gyroscope and video frames are usually not well synchronized. In this paper, we propose an online method that estimates all the necessary parameters while capturing videos. Our contributions are (1) simultaneous online camera self-calibration and camera-gyroscope calibration based on an implicit extended Kalman filter, and (2) generalization of coplanarity constraint of camera rotation in a rolling shutter camera model for cellphones. The proposed method is able to accurately estimate the needed parameters online with all kinds of camera motion, and can be embedded in gyro-aided applications such as video stabilization and feature tracking.
SOC CMOS technology for personal Internet products

Worldwide demand for Personal Internet Products is increasing rapidly, and will shape the directions of CMOS technology in the years ahead. Personal Internet Products are loosely defined in this paper as communication, computing and consumer products, which are enabled by the Internet: cell phones, PDAs, WLANs, Internet audio/video, ADSL, cable modems etc. Personal Internet Products are based on Digital Signal Processing (DSP) and analog functionality. They are made accessible to billions of people around the globe by intense focus on cost through SOC integration. In the Internet Age, Moore's Law will continue to be a technology imperative for the semiconductor industry. But SOC integration will be an additional technology imperative that drives down the cost of Personal Internet Product to mass market levels. SOC integration for Personal Internet Products requires the integration of analog, power analog, RF and memory onto the digital baseband processor, which is fabricated in high density, high performance, low cost digital CMOS technology. This paper describes the challenges and some of the solutions to achieve this vision.
Time-Frequency Modulation Diversity to Combat Periodic Impulsive Noise in Narrowband Powerline Communications

Non-Gaussian noise/interference severely limits communication performance of narrowband powerline communication (PLC) systems. Such noise/interference is dominated by periodic impulsive noise whose statistics varies with the AC cycle. The periodic impulsive noise statistics deviates significantly from that of additive white Gaussian noise, thereby causing dramatic performance degradation in conventional narrowband PLC systems. In this paper, we propose a robust transmission scheme and corresponding receiver methods to combat periodic impulsive noise in OFDM-based narrowband PLC. Towards that end, we propose (1) a time-frequency modulation diversity scheme at the transmitter and a diversity demodulator at the receiver to improve communication reliability without decreasing data rates; and (2) a semi-online algorithm that exploits the sparsity of the noise in the frequency domain to estimate the noise power spectrum for reliable decoding at the diversity demodulator. In the simulations, compared with a narrowband PLC system using Reed-Solomon and convolutional coding, whole-packet interleaving and DBPSK/BPSK modulation, our proposed transceiver methods achieve up to 8 dB gains in Eb/N0 with convolutional coding and a smaller-sized interleaver/deinterleaver.
Exploiting symmetry in channel shortening equalizers

Time-domain equalization is crucial in reducing intercarrier and intersymbol interference in multicarrier systems. A channel shortening time-domain equalizer (TEQ), which is a finite impulse response (FIR) filter, placed in cascade with the channel, produces an effective impulse response that is shorter than the channel impulse response. We show that finite length minimum mean squared error (MMSE) and maximum shortening SNR (MSSNR) TEQs are approximately symmetric, and infinite length MSSNR TEQs with a unit norm TEQ (UNT) constraint are exactly symmetric. A symmetric TEQ halves FIR implementation complexity, enables the frequency-domain equalizer and TEQ to be trained in parallel, and exhibits only a small loss in bit rate over nonsymmetric TEQs. In addition, a symmetric MSSNR-UNT TEQ reduces training computational complexity by a factor of 4 and doubles the length of the TEQ that can be designed.
Evaluating signal processing and multimedia applications on SIMD, VLIW and superscalar architectures

This paper aims to provide a quantitative understanding of the performance of DSP and multimedia applications on very long instruction word (VLIW), single instruction multiple data (SIMD), and superscalar processors. We evaluate the performance of the VLIW paradigm using Texas Instruments Inc.'s TMS320C62xx processor and the SIMD paradigm using Intel's Pentium II processor (with MMX) on a set of DSP and media benchmarks. Tradeoffs in superscalar performance are evaluated with a combination of measurements on Pentium II and simulation experiments on the SimpleScalar simulator. Our benchmark suite includes kernels (filtering, autocorrelation, and dot product) and applications (audio effects, G.711 speech coding, and speech compression). Optimized assembly libraries and compiler intrinsics were used to create the SIMD and VLIW code. We used the hardware performance counters on the Pentium II and the stand-alone simulator for the C62xx to obtain the execution cycle counts. In comparison to non-SIMD Pentium II performance, the SIMD version exhibits a speedup ranging from 1.0 to 5.5 while the speedup of the VLIW version ranges from 0.63 to 9.0. The benchmarks are seen to contain large amounts of available parallelism, however, most of it is inter-iteration parallelism. Out-of-order execution and branch prediction are observed to be extremely important to exploit such parallelism in media applications.
An all-digital PWM-based ΔΣ ADC with an inherently matched multi-bit quantizer

An all-digital PWM-based delta-sigma (ΔΣ) ADC is proposed. This system takes advantages of the duration of a pulse, rather than voltage or current, as the analog operand used in its closed-loop operation. Unlike VCO-based ADCs, this ADC as a linear input sampling stage with adequate uncalibrated performance. Furthermore, the architecture allows inherently matched multi-bit quantizer/DAC blocks by taking advantage of delay lines reusable in both quantization and DAC operation. A 3-bit prototype of this ADC in 0.18 μm CMOS process is implemented, tested, and presented. With an OSR of 72 and a bandwidth of 1 MHz, it achieves a dynamic range of 51 dB and SNDR of 49.6 dB while consuming 1.5 mA from a 1.8 V supply. The core occupies an area of 0.0275 mm2.
Automatic Floating-Point to Fixed-Point Transformations

Many digital signal processing and communication algorithms are first simulated using floating-point arithmetic and later transformed into fixed-point arithmetic to reduce implementation complexity. For the floating-point to fixed-point transformation, this paper describes two methods within an automated transformation environment. The first method, a gradient-based search for single-objective optimization with sensitivity information, provides a single solution, and can become trapped in local optima. The second method, a genetic algorithm for multi-objective optimization, provides a family of solutions that form a tradeoff curve for signal quality vs. implementation complexity. We provide case studies for an infinite impulse response filter. In the case study, implementation complexity is lookup table area for a field programmable gate array (FPGA) realization. We have made the transformation methods available in a software release on the Web.
Sum capacity of MIMO Gaussian broadcast channels with channel energy constraints

The motivation of this paper is to find the class of channels that provides the best sum capacity of a MIMO Gaussian broadcast channel with both transmit power and channel energy constraints when NtgesKNr, where Nt, Nr, and K denote the number of transmit antennas, the number of receive antennas, and the number of users in the system, respectively. The best sum capacity is achieved when the user channels are mutually orthogonal to each other. For each individual user, equal energy is distributed to all non-zero spatial eigenmodes. Further, we optimize the number of non-zero eigenmodes for all users and the optimal power distribution among users. Although, we only study the case of NtgesKN r in this paper, we conjecture that similar results still hold for Nt<KNr. The characteristics of the optimal channels can be used to direct antenna configurations
Multi-stage and sparse equalizer design for communication systems in reverberant underwater channels

Coherent underwater communication systems in shallow water must compensate for several impairments, including Doppler shift and reverberant channels. In this paper, we quantify tradeoffs in communication performance vs. computational complexity in designing receivers to compensate for these impairments. Our communication system is unidirectional, single-carrier, wideband, and packet-based. We use 1.5 hours of recorded data from an experimental system on a public lake with a moving transmitter and stationary receiver. Our contributions include acoustic channel modeling and a tradeoff analysis for Doppler shift estimation, multi-stage equalizers and sparse equalizers. We compare multi-stage and sparse equalizers against traditional equalizers.