nils-herrmann/clean_scirepeval huggingface dataset:
A time-efficient contributory key agreement scheme for secure group communications

Group-oriented services are attractive to both customers and service providers since they allow for potential markets that exploit user collaboration and shared experiences. In order to protect the content of a group service, the content must be encrypted using a key shared by group members. With the advancement of network technologies, customers will access group services from different networks using different terminals. The computational capabilities of the group members will vary. Contributory key agreement schemes have been developed to support secure communication between many senders and many receivers, but do not consider that users might require different amounts of time to perform a round of key establishment. In this paper, we develop a contributory key agreement scheme to setup the customer group which achieves a smaller latency for group key generation than existing schemes. We then address the latency needed to rekey the group during member joins and departures. A protocol that determines the location to place a joining member is presented that considers the time needed for rekeying the joining member as well as the effect the joining member has upon the departure times of the other group members. Simulations are presented that compare our algorithms with existing schemes for different group sizes, as well as different user join rates.
Distributed Space-Frequency Coding over Relay Channels

In this paper, the design of distributed space- frequency codes (DSFCs) implementing the decode-and-forward (DAF) protocol for wireless relay channels is considered. The proposed DSFCs are designed to achieve the frequency and cooperative diversities of the wireless relay channels. A two-hop system model, where there is no direct link from the source node to the destination node, is considered. We propose to use two stages of coding, namely, source node coding and relay nodes coding. The proposed DSFCs are proved to achieve full diversity of order NL where N is the number of relay nodes and L is the number of paths per channel.
Enhancement of microcalcifications on mammograms using a fractal modeling approach

The objective of this research is to model the mammographic parenchymal, ductal patterns and enhance microcalcifications using a fractal approach. According to the theory of deterministic fractal geometry, images can be modeled by deterministic fractal objects which are attractors of sets of two dimensional affine transformations. In this paper, a methodology based on fractal image modeling is developed to analyze and extract various mammographic textures. We show that general mammographic parenchymal and ductal patterns can be well modeled by the proposed approach. Therefore, microcalcifications can be enhanced by taking the difference between the original mammogram and modeled mammogram. Our results are compared with those of the partial wavelet reconstruction and morphological operation approaches. The results demonstrate that the fractal modeling method is an effective way to enhance microcalcifications, and thereby facilitate the radiologists' diagnosis. It is also able to improve the detection and classification of microcalcifications in a computer system.
Diversity analysis of space-time modulation over time-correlated Rayleigh-fading channels

Most space-time codes in the literature were proposed based on two ideal channel conditions: either quasistatic or rapid fading. However, these codes may suffer performance degradation due to temporal correlation caused by the movement of the mobile terminal or imperfect interleaving. In this correspondence, we provide a novel analytical framework for the diversity analysis of space-time modulation in time-correlated fading environment. We show that the space-time signals of square size achieving full diversity in quasistatic fading channels also achieve full diversity in time-correlated fading channels, independently of the time correlation matrix. Consequently, various classes of space-time signals designed for quasistatic fading channels can also be used for full-diversity transmission over time-correlated fading channels. Moreover, we show that if the time correlation matrix is of full rank, the design criteria for time-correlated fading channels are the same as those for rapid fading channels. To illustrate the theoretical results, some simulations were also performed under various temporal fading conditions.
Detectability of the Order of Operations: An Information Theoretic Approach

As it is more and more convenient to manipulate multimedia content, the authenticity of multimedia content becomes questionable. While there are many forensic techniques developed to identify the use of a single manipulation operation, a few has considered the cases where multiple operations may be involved. In these cases, investigators not only need to identify the use of each operation, but also need to detect the order of these operations. However, due to the interplay among operations, the order of operations may not always be detectable. This leads to a fundamental question of when we can and cannot detect the order of operations. In this paper, we formulate the problem of detecting the order of operations as a multiple hypotheses testing problem. Then, we propose an information theoretical framework to model the relationship between the detected hypothesis and the true hypothesis. Under this framework, we propose a mutual information-based criterion to obtain the best detector and use it to determine whether we can or cannot detect the order of operations based on certain set of features. A case study of detecting the order of resizing and blurring has been examined to demonstrate the effectiveness of the proposed framework and criteria. In addition, two known forensic problems are considered in the simulations to show that the results obtained from the proposed framework and criteria match those of the existing works.
Power minimization under real-time source distortion constraints in wireless networks

In multiple access wireless networks with co-channel interference, allocating resources such as transmitted powers and source rates is a task critical to improve performance. In this paper, we introduce a new technique aimed at minimizing the overall transmitted power subject to constraints on the incurred source distortion. The technique is based on the use of real-time source codecs with externally adaptable output rate and rate compatible punctured convolutional (RCPC) channel encoders. We develop an adaptive algorithm to find the optimal power and source rate allocation to the different users according to their channel conditions and under distortion constraints. We present simulation results to show that it is possible to reduce the overall transmitted power significantly with a relatively small distortion increases for some users, and while keeping the network average distortion unchanged.
Multiuser distortion management of layered video over resource limited downlink multicode-CDMA

Transmitting multiple real-time encoded videos to multiple users over wireless cellular networks is a key driving force for developing broadband technology. We propose a new framework to transmit multiple users' video programs encoded by MPEG-4 FGS codec over downlink multicode CDMA networks in real time. The proposed framework jointly manages the rate adaptation of source and channel coding, CDMA code allocation, and power control. Subject to the limited system resources, such as the number of pseudo-random codes and the maximal power for CDMA transmission, we develop an adaptive scheme of distortion management to ensure baseline video quality for each user and further reduce the overall distortion received by all users. To efficiently utilize system resources, the proposed scheme maintains a balanced ratio between the power and code usages. We also investigate three special scenarios where demand, power, or code is limited, respectively. Compared with existing methods in the literature, the proposed algorithm can reduce the overall system's distortion by 14% to 26%. In the demand-limited case and the code-limited but power-unlimited case, the proposed scheme achieves the optimal solutions. In the power-limited but code-unlimited case, the proposed scheme has a performance very close to a performance upper bound
A cartel maintenance framework to enforce cooperation in wireless networks with selfish users

In distributed wireless networks without centralized control, each user is its own authority to maximize its own performance. This distributed characteristic provides the users with the incentives of greedy competitions for the network resources such as bandwidth and transmission time. Such competitions deteriorate the system performance dramatically and result in low non-cooperative performances. Ensuring cooperation among selfish users can improve the performances and thus becomes an important issue for such wireless networks. In this paper, a Cartel Maintenance repeated game framework is proposed to enforce the cooperation among selfish users. The soul of Cartel Maintenance is to construct contracts among independent individuals for cooperative benefits and non-cooperative punishment, so as to limit inefficient competitions. In the proposed framework, a trigger-punishment game rule is designed to encourage the users to follow the cooperative strategy. First, all users agree to cooperate. Then in the following time slot, if users observe the others play cooperatively, cooperation will be played. If some users detect that others may defect based on the observed information, these users will play punishment phases for a certain period of time. This punishment is optimized so that the gain obtained by the deviation users is outweighed by the future punishments. Therefore, no user has the incentives to deviate, and the cooperation among selfish users is enforced. Then, the framework is employed to the multiple random access scenarios in wireless networks with selfish users, where the closed-form optimal solutions of cooperation enforcement are derived. The simulation results show that the proposed scheme can achieve significant performance gains over the non-cooperation scheme by having enough punishment threat to keep the cooperation among users.
A data embedded video coding scheme for error-prone channels

We propose a novel data embedding scheme for fractional-pixel based video coding algorithms such as H.263 and MPEG-2. By modifying the motion estimation procedure at fractional-pixel precision, two bits data can be embedded in a motion vector (MV) for an inter-mode coded macroblock (MB). For half-pixel precision motion estimation, the resulted bitstream is compatible with the current video coding standards. Performance of the proposed data embedding scheme in terms of compression efficiency is also studied. As an application example of the proposed data embedding scheme, an error-resilient video coding scheme is also presented where some redundant information, which is used to protect MVs and coding modes of MBs in one frame, is embedded into the MVs in the next frame. When errors occur in one group of blocks (GOB), the decoder can exactly recover the MVs of the corrupted GOB if the next frame can be received correctly. Simulations show that the proposed scheme has better performance than standard H.263 coding scheme for transmission over error-prone channels.
Cooperation stimulation in cooperative communications: An indirect reciprocity game

The viability of cooperative communications largely depends on the willingness of users to help. However, in future wireless networks where users are rational and pursue different objectives, they will not help relay information for others unless this can improve their own utilities. Therefore, it is very important to study the incentive issues when designing cooperative communication systems. In this paper, we propose a cooperation stimulation scheme for multiuser cooperative communications using indirect reciprocity game. By introducing the notion of reputation and social norm, rational users who care about their future utilities get the incentive to cooperate with others. Different from existing works on reputation based schemes that mainly rely on experimental verifications, we prove theoretically that cooperating with users having good reputation can be sustained as an equilibrium. Moreover, by modeling the action spreading as an evolutionary game, we show through simulations that the equilibria we found are evolutionarily stable and can be reached with proper initial conditions. Finally, simulation results are shown to verify the efficiency and effectiveness of the proposed scheme.
Joint link quality and power management over wireless networks with fairness constraint and space-time diversity

In multiaccess wireless networks, dynamic allocation of resource such as link qualities and transmitted powers is an important means to combat time-varying fading environments and cochannel interferences (CCIs). In most prior work, every link's quality is maintained by having a fixed signal-to-interference-noise-ratio (SINR) requirement. We discover that such a constraint is too strong and can degrade the performance of entire wireless networks, because a user with a bad channel response requires too much transmitted power and, therefore, causes unnecessary CCI to other users. In this paper, we alleviate this constraint and explore the time and multiuser diversity. For each user, the time-average link quality is maintained as a constant to ensure fairness. For the whole system, we want to minimize the overall transmitted power. In order to solve this problem, each user provides the system with a SINR range that is acceptable, according to the channel conditions and transmission history. Then, the system allocates the resources according to these ranges, channel conditions, and other practical constraints. Each time, some users may sacrifice their performances to reduce the overall network transmitted power. These users' temporary sacrifices will improve the system performance and will be paid back in the long term. This scheme can be conceived of as "water filling" the wireless network resources to different users at different times. In addition, by combining the proposed scheme with beamforming, we can have one more degree of freedom to combat CCIs in different directions of arrivals and different channel conditions over time.
Low complexity adaptive beamforming and power allocation for OFDM over wireless networks

In this paper, the performance of a multiuser wireless network using OFDM, combined with power control and adaptive beamforming for uplink transmission is presented. An adaptive power control algorithm is exploited to achieve the desired signal to noise and interference ratio (SINR) at each subchannel and increase the power efficiency of the mobile transmitter. Therefore, we can achieve a better overall error probability with a fixed total power. A distributed iterative algorithm is used to jointly update the transmission power and the beamformer weights at each subchannel so that it can converge to the optimal solution for both power and beamforming vectors at each subchannel. Another algorithm has been proposed to decrease the complexity resulting from the number of beamformers and FFT blocks. The algorithms use only the interference measured locally by the transmitter. Unlike most of the loading algorithms which optimize the bit distribution and subchannel power allocation for a single transmitter, this approach tries to optimize the power allocation and decrease the interference for the whole network.
Rate control for DS-CDMA channels using power control and short orthogonal pseudo random codes

Multimedia applications are increasingly seen in wireless service networks. The higher channel rate requirements of certain multimedia services, such as video, places constraints on wireless resources, which must provide high channel rates in the presence of high interference and noise. We propose to increase the channel rate of high rate multimedia users by controlling the effective signal to interference and noise ratio (SINR) for those users, and by breaking individual data streams into smaller substreams which each have lower capacity requirements.
Digital image source coder forensics via intrinsic fingerprints

Recent development in multimedia processing and network technologies has facilitated the distribution and sharing of multimedia through networks, and increased the security demands of multimedia contents. Traditional image content protection schemes use extrinsic approaches, such as watermarking or fingerprinting. However, under many circumstances, extrinsic content protection is not possible. Therefore, there is great interest in developing forensic tools via intrinsic fingerprints to solve these problems. Source coding is a common step of natural image acquisition, so in this paper, we focus on the fundamental research on digital image source coder forensics via intrinsic fingerprints. First, we investigate the unique intrinsic fingerprint of many popular image source encoders, including transform-based coding (both discrete cosine transform and discrete wavelet transform based), subband coding, differential image coding, and also block processing as the traces of evidence. Based on the intrinsic fingerprint of image source encoders, we construct an image source coding forensic detector that identifies which source encoder is applied, what the coding parameters are along with confidence measures of the result. Our simulation results show that the proposed system provides trustworthy performance: for most test cases, the probability of detecting the correct source encoder is over 90%.
Indoor Global Positioning System with Centimeter Accuracy Using Wi-Fi [Applications Corner]

In this column, we present a time-reversal method for indoor localization that achieves centimeter accuracy with a single pair of off-the-shelf Wi-Fi devices. The high accuracy for localization is maintained under strong NLOS scenarios. With the exploitation of the inherent frequency and spatial diversities in Wi-Fi systems, it is capable of creating a large effective bandwidth to enable centimeter accuracy. Extensive experiment results in a typical office environment show that the centimeter accuracy as well as robustness against dynamics can be simultaneously achieved with a large effective bandwidth. The global GPS can achieve 3-15 m of accuracy by mapping the world into latitude and longitude coordinates. The presented “indoor GPS” can achieve 1-2 cm accuracy when an indoor environment is fingerprinted and mapped.
Protection against reverse engineering in digital cameras

Over the past decade, a number of digital forensic techniques have been developed to authenticate digital signals. One important set of forensic techniques operates by estimating signal processing components of a digital camera's signal processing pipeline, then using these estimates to perform forensic tasks such as camera identification or forgery detection. However, because these techniques are capable of estimating a camera's internal signal processing components, these forensic techniques can be used for reverse engineering. In this paper, we propose integrating an anti-forensic module into a digital camera's processing pipeline to protect against forensic reverse engineering. Our proposed technique operates by removing linear dependencies amongst an output images interpolated color values and by disrupting the color sampling grid. Experimental results show that our proposed technique can be effectively used to protect against the forensic reverse engineering of key components of a digital camera's processing pipeline.
Blind identification and equalization for multiple-input/multiple-output channels

To separate and recover multiple signals in data communications, antenna arrays and acoustic sensor arrays, the impulse responses of multiple-input/multiple-output (MIMO) channels have to be identified explicitly or implicitly. This paper deals with the blind identification of MIMO FIR channels based on second-order statistics of the channel outputs and its application in blind channel equalization and signal-separation. We first investigate the identifiability of MIMO FIR channels, and obtain a necessary and sufficient condition for MIMO FIR channels to be identifiable up to a unitary ambiguity matrix using second-order statistics. Next, we extend the identification algorithms for single-input/multiple-output (SIMO) FIR channels, such as the algebraic algorithm and the subspace algorithm to the identification of MIMO FIR channels. Since the ambiguity matrix cannot be estimated using second-order statistics, we then present a fourth-order cumulant based ambiguity matrix estimation algorithm. Finally, we demonstrate effectiveness of the algorithms in this paper by computer simulations.
Resource Allocation for Multiuser Cooperative OFDM Networks: Who Helps Whom and How to Cooperate

Cooperative transmissions have been shown to be able to greatly improve system performance by exploring the broadcasting nature of wireless channels and cooperation among users. We focus, in this paper, on leveraging cooperation for resource allocation among users such that the network performance can be improved. Two important questions are answered-who should help whom among the distributively located users, and how many resources the users should use for cooperation to improve the performance. To answer these questions, a power-optimization, subcarrier-allocation, and relay-selection problem is formulated over a multiuser orthogonal frequency-division multiplexing (OFDM) network, which is applicable to systems such as wireless local area networks (WLANs). In the multiuser OFDM network, cooperation among different users is conducted by assigning the subcarriers of the helping users to relay a certain part of the helped users' data, while maintaining the desired rates of both helping users and helped users by means of power control and rate adaption. This way, the bandwidth efficiency of the multiuser OFDM system with cooperation is the same as that of the noncooperative OFDM system. The formulated optimization problem is an assignment problem for subcarrier usage and corresponding bit loading as well as power control. We provide an approximate closed-form solution for a two-user two-subcarrier case. Then, a suboptimal heuristic algorithm for a multiple-user multiple-subcarrier case is proposed and implemented in the base station to solve the formulated NP-hard problem. From the simulation results, the proposed scheme achieves up to 50% overall power saving for the two-user system and 19%-54% overall power saving for the multiuser case with random locations, compared with the current multiuser OFDM system without cooperative diversity. The proposed scheme is also compared to a much more complicated orthogonal frequency-division multiple access (OFDMA) system.
Resource efficient multicast for 3G UMTS wireless networks

The European telecommunication standard Institute proposed IP multicast for third generation universal mobile telecommunication system (UMTS) broadband wireless networks. In their proposed approach, multicast messages are sent as multiple unicast messages to all active multicast group members in the UMTS network. As a result their proposed scheme is inefficient in terms of internal infrastructure and radio resource usage; and multicast packets incur significant delays. We propose a resource efficient IP multicast scheme, which significantly reduce radio resource usage and message delay. The proposed scheme uses IP tunnels and efficient unicast routing within the UMTS infrastructure to eliminate unnecessary message duplication and transmission. We also proposed the use common multicast channels in the efficient utilization of radio resources. Common multicast channels are designed to accommodate the varying and channel characteristics of active multicast users. We also propose a secure mechanism to distribute common radio group key to active multicast users.