nils-herrmann/clean_scirepeval huggingface dataset:
Blind forensics of contrast enhancement in digital images

Digital images have seen increased use in applications where their authenticity is of prime importance. This proves to be problematic due to the widespread availability of digital image editing software. As a result, there is a need for the development of reliable techniques for verifying an image's authenticity. In this paper, a blind forensic algorithm is proposed for detecting the use of global contrast enhancement operations to modify digital images. Furthermore, a separate algorithm is proposed to identify the use of histogram equalization, a commonly implemented contrast enhancement operation. Both algorithms perform detection by seeking out unique artifacts introduced into an image's histogram as a result of the particular operation examined. Additionally, results are presented showing the effectiveness of both proposed algorithms.
Downlink beamforming for DS-CDMA mobile radio with multimedia services

Downlink beamforming is a promising technique for direct-sequence code-division multiple-access (DS-CDMA) systems with multimedia services to effectively reduce strong interference induced by high data rate users. A new downlink beamforming technique is proposed that converts the downlink beamforming problem into a virtual uplink one and takes into account the data rate information of all users. Since the main complexity of this method is due to the existence of multidelay paths, two simplified algorithms are suggested using an equivalent one-path channel vector to replace multipath channel vectors. Computer simulation results are given to evaluate the downlink capacity of DS-CDMA systems using a base station antenna array and the new algorithms proposed.
Algorithms and architectures for split recursive least squares

In this paper, a new computationally efficient algorithm for recursive least-squares (RLS) filtering is presented. The proposed split RLS algorithm can perform the approximated RLS with O(N) complexity for signals having no special data structure to be exploited. Our performance analysis shows that the estimation bias will be small when the input data are less correlated. We also show that for highly correlated data, the orthogonal preprocessing scheme can be used to improve the performance of the split RLS. The systolic implementation of our algorithm based on the QR-decomposition RLS (QRD-RLS) array requires only O(N) hardware complexity and the system latency can be reduced to O(log/sub 2/ N). A major advantage of the split RLS is its superior tracking capability over the conventional RLS under non-stationary environments.
Green Wireless Communications: A Time-Reversal Paradigm

Green wireless communications have received considerable attention recently in hope of finding novel solutions to improve energy efficiency for the ubiquity of wireless applications. In this paper, we argue and show that the time-reversal (TR) signal transmission is an ideal paradigm for green wireless communications because of its inherent nature to fully harvest energy from the surrounding environment by exploiting the multi-path propagation to re-collect all the signal energy that would have otherwise been lost in most existing communication paradigms. A green wireless technology must ensure low energy consumption and low radio pollution to others than the intended user. In this paper, we show through theoretical analysis, numerical simulations and experiment measurements that the TR wireless communications, compared to the conventional direct transmission using a Rake receiver, reveals significant transmission power reduction, achieves high interference alleviation ratio, and exhibits large multi-path diversity gain. As such it is an ideal paradigm for the development of green wireless systems. The theoretical analysis and numerical simulations show an order of magnitude improvement in terms of transmit power reduction and interference alleviation. Experimental measurements in a typical indoor environment also demonstrate that the transmit power with TR based transmission can be as low as 20% of that without TR, and the average radio interference (thus radio pollution) even in a nearby area can be up to 6dB lower. A strong time correlation is found to be maintained in the multi-path channel even when the environment is varying, which indicates high bandwidth efficiency can be achieved in TR radio communications.
Game-theoretic analysis of maximum-payoff multiuser collusion

Multiuser collusion is an effective attack against traitor-tracing multimedia fingerprinting, where a group of attackers collectively mount attacks to reduce their risk of being detected. During collusion, each attacker wishes to maximize his or her own payoff. To resolve the conflict, colluders have to negotiate with each other and achieve fair collusion. An attacker also needs to decide with whom he or she wants to collude. Though colluding with more people helps further reduce the risk, it also makes an attacker share with more people the rewards from illegal usage of multimedia. This paper uses game theory to model the complex colluder dynamics and analyzes the tradeoff between the risk and the rewards. We study how the selection of fellow attackers affects each colluder's utility, and analyze the optimum strategies that maximize colluders' payoffs.
Performance Analysis of Multiband OFDM UWB Systems With Imperfect Synchronization and Intersymbol Interference

This paper provides performance analysis of MB-OFDM UWB systems that not only captures the characteristics of realistic ultra-wideband (UWB) channels, but also takes into consideration of the imperfection of the frequency and timing synchronizations and the effect of intersymbol interference. The systems are considered in multipath fading channels, the IEEE 802.15.3a channel standard, with four channel models: CM1, CM2, CM3, and CM4. These channel models are characterized by cluster arrival rate, ray arrival rate within clusters, and cluster and ray decay factors. First, an average signal-to-noise ratio with imperfect synchronizations and intersymbol interference is derived. Then a closed-form bit error rate performance formulation that provides insightful understanding of the system performance in various synchronization conditions is obtained under Rayleigh fading assumption. This analytical performance formulation serves as an upper bound on the bit error rate performance of UWB systems. Finally, simulation results under various channel and synchronization conditions are provided to validate the theoretical analysis.
Distortion Exponents for Different Source-Channel Diversity Achieving Schemes over Multi-Hop Channels

The performance limits of multimedia systems combining source (multiple description) coding and channel coding with user cooperation diversity over multi-hop channels is studied. Performance is measured through the distortion exponent, which measures the rate of decay of the end-to-end distortion at asymptotic high SNRs. Two implementations for user cooperation are considered: amplify-and-forward and decode-and-forward. Results comparing different source and channel coding schemes show that optimum channel coding diversity provides the best performance, followed by source coding diversity. The results also show that at low bandwidth expansion factor, source encoding distortion is the main limiting factor. As the bandwidth expansion factor increases, user cooperation diversity is the main limiting factor, thus, the distortion exponent could be improved by increasing the number of relays.
A joint channel estimation and unequal error protection scheme for video transmission in OFDM systems

OFDM modulation, which has been adopted for the digital video broadcasting (DVB-T) standard in Europe, has been recognized for its good performance for high data rate wireless communications. Therefore, the study of the robust transmission of multimedia data over OFDM systems has attracted extensive research interest. In the past, channel estimation, which is an important aspect in OFDM systems, has not been exploited for multimedia transmission. When using block-training based channel estimation schemes, there exists a periodic variation of the error rates due to channel estimation imprecision. We use this property to provide unequal error protection (UEP) for video transmission. Compared with systems using pilot-training based channel estimation schemes, which are recommended in the DVB-T standard, a performance gain of about 2dB in the PSNR of the reconstructed images is achieved.
Adaptive channel estimation using cyclic prefix in multicarrier modulation system

Multicarrier modulation (MCM) is a promising technique for high rate data transmission and the channel estimation is very important for the implementation of MCM. We found that the cyclic prefix, originally used solely to reduce the intersymbol interference (ISI), can be viewed as a source of channel information. Based on this observation, we propose an adaptive channel estimation algorithm using the cyclic prefix. This algorithm can adaptively track the channel variation without additional training sequences.
Cooperative peer-to-peer streaming: An evolutionary game-theoretic approach

While peer-to-peer (P2P) video streaming systems have achieved promising results, they introduce a large number of unnecessary traverse links, which consequently leads to substantial network inefficiency. To address this problem and achieve better streaming performance, we propose to enable cooperation among “group peers,” which are geographically neighboring peers with large intra-group upload and download bandwidths. Considering the peers' selfish nature, we formulate the cooperative streaming problem as an evolutionary game and derive, for every peer, the evolutionarily stable strategy (ESS), which is the stable Nash equilibrium and no one will deviate from. Moreover, we propose a simple and distributed learning algorithm for the peers to converge to the ESSs. With the proposed algorithm, each peer decides whether to be an agent who downloads data from the peers outside the group or a free-rider who downloads data from the agents by simply tossing a coin, where the probability of being a head for the coin is learned from the peer's own past payoff history. Simulation results show that the strategy of a peer converges to the ESS. Compared to the traditional non-cooperative P2P schemes, the proposed cooperative scheme achieves much better performance in terms of social welfare, probability of real-time streaming, and video quality (source rate).
Understanding Sequential User Behavior in Social Computing: To Answer or to Vote?

Understanding how users participate is of key importance to social computing systems since their value is created from user contributions. In many social computing systems, users decide sequentially whether to participate or not and, if participate, whether to create a piece of content directly, i.e., answering, or to rate existing content, i.e., voting. Moreover, there exists an answering-voting externality as a user's utility for answering depends on votes received in the future. We present in this paper a game-theoretic model that formulates the sequential decision making of strategic users under the presence of such an answering-voting externality. We prove theoretically the existence and uniqueness of a pure strategy equilibrium. To further understand the equilibrium participation of users, we show that there exist advantages for users with higher abilities and for answering earlier. Therefore, the equilibrium has a threshold structure and the threshold for answering gradually increases as answers accumulate. We further extend our results to a more general setting where users can choose endogenously their efforts for answering. To show the validness of our model, we analyze user behavior data collected from a popular Q&A site Stack Overflow and show that the main qualitative predictions of our model match up with observations made from the data. Finally, we formulate the system designer's problem and abstract from numerical simulations several design principles that could potentially guide the design of incentive mechanisms for social computing systems in practice.
Topology-aware key management schemes for wireless multicast

In secure multicast applications, key management must be employed to provide access control to the multicast content In wireless networks, where the error rate is high and the bandwidth is limited, the design of key management schemes should place emphasis on reducing the communication burden associated with key updating and improving the reliability of key distribution. The topology-matching key management (TMKM) scheme has been proposed to reduce the communication burden associated with rekeying by matching the key tree to the network topology and localizing the transmission of rekeying messages. This scheme, however, is only suitable for homogeneous networks where mobiles users are uniformly distributed in the service area and experience similar delay and transmission error rates. In this paper, we present an improved topology-aware key management scheme that is suitable for a large-scale cellular wireless network where the heterogeneity of the network is taken into consideration. The proposed scheme not only reduces the communication overhead, but also improves the reliability of the key distribution.
Achieving Centimeter-Accuracy Indoor Localization on WiFi Platforms: A Frequency Hopping Approach

Indoor positioning systems (IPSs) are attracting more and more attention from the academia and industry recently. Among them, approaches based on WiFi techniques are more favorable since they are built upon the WiFi infrastructures available in most indoor spaces. However, due to the bandwidth limit in mainstream WiFi systems, the IPS leveraging WiFi can hardly achieve centimeter localization accuracy under strong nonline-of-sight (NLOS) conditions which is common for indoor environment. In this paper, to achieve the centimeter-level accuracy, we present a WiFi-based IPS that exploits the frequency diversity via frequency hopping. In the offline phase, the system collects channel frequency responses (CFRs) from multiple channels and from a number of locations-of-interest. Then, the CFRs are post-processed to mitigate the synchronization errors as well as interference from other WiFi networks. Then, using bandwidth concatenation, the CFRs from multiple channels are combined into location fingerprints which are stored into a local database. During the online phase, CFRs are formulated into the location fingerprint and is compared against the fingerprints in the database via the time-reversal resonating strength (TRRS). Finally, the IPS determines the location according to the TRRS. Extensive experiment results demonstrate a perfect centimeter-level accuracy in an office environment with strong NLOS using only one pair of single-antenna WiFi devices.
Differential space-frequency modulation for MIMO-OFDM systems via a "smooth" logical channel

In this paper, a differential space-frequency modulation (DSFM) scheme is proposed for MIMO-OFDM systems with assumptions that the channel keeps constant only within each OFDM block, and it may change independently from one OFDM block to another. The transmitted/received signals are differentially en/decoded in the frequency dimension within each OFDM block. The performance of the proposed scheme depends on the channel power delay profile. Moreover, if the statistics of the power delay profile are known at the transmitter, we further propose to permutate the channel frequency responses over subcarriers; by using Dijkstra's algorithm to increase the performance of the DSFM scheme. Simulation results show that the DSFM scheme with permutations performs very well for various channel profiles.
Unified parallel lattice structures for time-recursive discrete cosine/sine/Hartley transforms

Unified efficient computations of the discrete cosine transform (DCT), discrete sine transform (DST), discrete Hartley transform (DHT), and their inverse transforms employing the time-recursive approach are considered. Unified parallel lattice structures that can dually generate the DCT and DST simultaneously as well the DHT are developed. These structures can obtain the transformed data for sequential input time recursively with a throughput rate of one per clock cycle. The total number of multipliers required is a linear function of the transform size N, with no constraint on N. The resulting architectures are regular, modular, and without global communication so that they are very suitable for VLSI implementation for high-speed applications. It is shown that the DCT, DST, DHT and their inverse transforms share an almost identical lattice structure. The tradeoff between time and area for the block data processing is considered.
Space-time-frequency coded multiband UWB communication systems

In this paper, we propose a general framework to analyze the performance of multiband UWB-MIMO systems regardless of specific coding schemes. A combination of space-time-frequency (STF) coding and hopping multiband OFDM modulation is also proposed to fully exploit all of the available spatial and frequency diversities, richly inherent in UWB environments. We quantify the performance merits of multiband UWB-MIMO systems in case of Nakagami-m frequency-selective fading channels. We show that the maximum achievable diversity of the proposed system is the product of the number of transmit and receive antennas, the number of multipath components, and the number of jointly encoded OFDM blocks. Interestingly, theoretical result shows that the diversity gain does not severely depend on the fading parameter m.. Finally, simulation results are presented to support the theoretical analysis.
Wireless Network Cocast: Cooperative communications with Space-Time Network coding

The concept of STNC is very general. Fundamentally, it involves combining information from different sources at a relay node, which gives rise to the concept of network coding, and transmitting the combined signals in dedicated time slots from various locations in a network, which makes the space-time concept. Various traditional combining techniques can be used, including CDMA-like and OFDMA-like techniques, transform-based techniques with the use of Hadamard and Vandermonde matrices, and traditional network coding. However, a major distinction is that the combining of symbols from different sources happens inside a transmitter instead of through the air. Below is an overview of the developed STNCs.
Forensic estimation and reconstruction of a contrast enhancement mapping

Due to the ease with which convincing digital image forgeries can be created, a need has arisen for digital forensic techniques capable of detecting image manipulation. Once image alterations have been identified, the next logical forensic task is to recover as much information as possible about the unaltered version of image and the operation used to modify it. Previous work has dealt with the forensic detection of contrast enhancement in digital images. In this paper we propose an iterative algorithm to jointly estimate any arbitrary contrast enhancement mapping used to modify an image as well as the pixel value histogram of the image before contrast enhancement. To do this, we use a probabilistic model of an image's pixel value histogram to determine which histogram entries are most likely to correspond to contrast enhancement artifacts. Experimental results are presented to demonstrate the effectiveness of our proposed method.
Optimal rate allocation for video coding and transmission over wireless channels

An integrated framework of optimal rate allocation for video coding is presented in the case of transmission over wireless channels without feedback channels. For a fixed channel bit rate and finite number of channel coding rate, the proposed scheme can find the optimal source and channel coding pair and corresponding robust video coding scheme such that the expected end-to-end distortion of video signals can be minimized. With the, assumption that encoder has the stochastic channel information, the proposed scheme takes into account robust video coding, channel coding and packetization, error concealment techniques altogether. Simulation results show the accuracy and optimality of the proposed method.
Adaptive overlapping approach for DCT-based motion estimation

The feedback loop for temporal prediction of traditional implementations of an MPEG-compliant video coder requires conversion of images from the spatial domain to the transform domain and then back to the spatial domain due to the restriction of motion estimation schemes performed only in the spatial domain, severely limiting the throughput of the coder. However, the availability of the low-complexity DCT-based motion estimation scheme (DXT-ME) that we proposed in the past can remove this bottleneck and concurrently reduce the complexity of the overall coder structure. We adopt an adaptive overlapping approach to further improve this DCT-based motion estimation scheme, as demonstrated in the simulation results. Furthermore, the analysis of stability of DXT-ME is presented and the case of a uniformly bright environment is also discussed. Finally, the parallel architecture of DXT-ME is outlined.
A Component Estimation Framework for Information Forensics

With a rapid growth of imaging technologies and an increasingly widespread usage of digital images and videos for a large number of high security and forensic applications, there is a strong need for techniques to verify the source and integrity of digital data. Component forensics is new approach for forensic analysis that aims to estimate the algorithms and parameters in each component of the digital device. In this paper, we develop a novel theoretical foundation to understand the fundamental performance limits of component forensics. We define formal notions of identifiability of components in the information processing chain, and present methods to quantify the accuracies at which the component parameters can be estimated. Building upon the proposed theoretical framework, we devise methods to improve the accuracies of component parameter estimation for a wide range of forensic applications.
Connectivity-aware network maintenance and repair via relays deployment

In this paper we address the network maintenance problem, in which we aim to maximize the lifetime of a sensor network by adding a set of relays to it. The network lifetime is defined as the time until the network becomes disconnected. The Fiedler value, which is the algebraic connectivity of a graph, is used as an indicator of the network health. The network maintenance problem is formulated as a semi-definite programming (SDP) optimization problem that can be solved efficiently in polynomial time. First, we propose a network maintenance algorithm that obtains the SDP-based locations for a given set of relays. Second we propose a routing algorithm, namely, Weighted Minimum Power Routing (WMPR) algorithm, that significantly increases the network lifetime due to the efficient utilization of the deployed relays. Third, we propose an adaptive network maintenance algorithm that relocates the deployed relays based on the network health indicator. Further, we study the effect of two different transmission scenarios, with and without interference, on the network maintenance algorithm. Finally, we consider the network repair problem, in which we find the minimum number of relays along with their SDPbased locations to reconnect a disconnected network. We propose an iterative network repair algorithm that utilizes the network maintenance algorithm.
Unitary Design of Radar Waveform Diversity Sets

This chapter contains sections titled: Introduction 2 ? 2 Space-Time Diversity Waveform Design 4 ? 4 Space-Time Diversity Waveform Design Waveform Families Based on Kronecker Products Introduction to Data-Dependent Waveform Design 3 ? 3 and 6 ? 6 Waveform Scheduling Summary References