Pool Of Users Research Articles

Dynamic Inter Arrival Time Based Seamless Handoff for Mobile WIMAX Ping-Pong Calls Bypassing PKMv2 EAP Authentication

The rapid growth of wireless communication and its persistent use influences all walks of life. Mobile WiMAX IEEE 802.16e standard enabled convergence of mobile and fixed broadband networks through a common wide-area radio-access technology and flexible network architecture. It aims to provide seamless support to its users but an inevitable is that the long delay which occurs during the handoff management in every network process. This paper proposes a Dynamic Interval based Processing Algorithm to separate ping-pong users from the pool of users and to process them separately thus reducing the overhead of network re-entry process. Incoming users are divided into three categories like new user, old user and ping pong user. New user should undergo all the phases of network entry process, old user is provided with authentication key which leads to skipping of steps in generation of keys. Proposed algorithm deals with identifying the ping pong users by calculating the inter arrival duration and rate with same base station. When assured authenticated ping-pong users enter the network next time within the allotted time they will be provided with last used Traffic Encryption Key (TEK) thus bypassing key generation phase . It is observed that the proposed work performs the authentication phase and cancels the key generation phase which leads to minimum network entry delay and it saves to the maximum of 80% processing time. The network model was developed using Network Simulator and the algorithm was implemented in MATLAB GUIDE which gets connected to the database developed in MYSQL.This approach is justified through its timing analysis result which proves the efficient swift in the handoff processes.

HCV seroconversion among never-injecting heroin users at baseline: No predictors identified other than starting injection

BackgroundHeroin users who do not inject constitute a large pool of drug users with a potentially important impact on public health. We aimed to estimate the incidence of hepatitis C virus (HCV) among heroin users who had never injected (NIDUS) at baseline, and the effect of starting injecting during follow-up, other percutaneous exposures, sharing snorting paraphernalia, cocaine/crack use, and risky sexual behaviour on HCV-seroconversion. MethodsProspective cohort of 305 HCV-negative NIDUs at baseline, aged 18–30 and street-recruited in three Spanish cities in 2001–2003. Computer-assisted personal interviews were conducted and dried blood-spot samples were collected. Bivariate and multivariable Poisson models were used. ResultsAmong the 305 never-injectors who were HCV-negative at baseline, 197 (64.6%) were followed-up and 21 seroconverted [HCV-incidence rate=5.8/100 person-years at risk (pyar) (95% CI: 3.6–8.9)]. HCV incidence in new-injectors was 28.4/100pyar [(95% CI, 14.7–49.7) vs. 2.8/100pyar (95% CI, 1.3–5.4)] among NIDUs. Of the risk exposures considered, starting injecting was the only predictor of HCV-seroconversion [adjusted relative risk=10.1, 95% CI: 3.8–26.7]. ConclusionThe HCV-seroconversion rate was 10 times higher among new-injectors than never-injectors. No predictors other than starting injecting were found for HCV-seroconversion. Harm reduction interventions to prevent HCV infection should include prevention of drug injection.

Creating low vision and nonvisual instructions for diabetes technology: an empirically validated process.

Nearly 20% of the adults with diagnosed diabetes in the United States also have visual impairment. Many individuals in this group perform routine diabetes self-management tasks independently, often using technology that was not specifically designed for use by people with visual impairment (e.g., insulin pumps and pens). Equitable care for persons with disabilities requires providing instructions in formats accessible for nonreaders. However, instructions in accessible formats, such as recordings, braille, or digital documents that are legible to screen readers, are seldom available. This article includes a summary of existing guidelines for creating accessible documents. The guidelines are followed by a description of the production of accessible nonvisual instructions for use of insulin pens used in a study of dosing accuracy. The study results indicate that the instructions were used successfully by 40 persons with visual impairment. Instructions in accessible formats can increase access to the benefits of diabetes technology for persons with visual impairment. Recorded instructions may also be useful to sighted persons who do not read well, such as those with dyslexia, low literacy, or who use English as a second language. Finally, they may have important benefits for fully sighted people who find it easier to learn to use technology by handling the equipment while listening to instructions. Manufacturers may also benefit from marketing to an increased pool of potential users.

Method madness

This case study was created to analyze the methodology and procedures used during a pilot study on mobile usability and preferences conducted at a small Midwestern state college. The pilot study set forth to test features of the pre-redesign University of Wisconsin-Stout website as seen through the screen of a mobile device and then ascertain what students wanted to see in a redesigned version of the mobile interface. The findings of the pilot study were less surprising to the researcher than the problems encountered during the research itself. Future researchers would be well advised to attend to passing trends in mobile technology, as well as avoiding limitations on sample size caused by choice of delivery method and choice of user pool.

Net Throughput Maximization of Per-Chunk User Scheduling for MIMO-OFDM Downlink

Per-chunk user scheduling for multiple-input-multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) downlink is considered. By grouping adjacent subcarriers into chunks, the amount of required channel state information feedback is reduced. Based on the net throughput criterion, which accounts for the reduction in sum rate due to the feedback overhead, it is shown that there exists an optimal chunk size that maximizes the net throughput. To reduce the feedback requirement even further, an opportunistic feedback scheme is proposed, and a close approximation for its net throughput is derived. The net throughput of per-chunk user scheduling with optimized chunk size is compared to various other limited-feedback MIMO-OFDM downlink strategies. The results show that increasing the total number of users in the system results in the net throughput of most existing MIMO-OFDM downlink schemes decreasing to zero for moderate-size user pools, whereas the net throughput of per-chunk user scheduling with opportunistic feedback increases with the total number of users, even when that number is very large(>; 1000).

User QoE Influenced Spectrum Trade, Resource Allocation, and Network Selection

In future wireless networks, we envision more dynamic telecommunication paradigm, where the dynamics may be translated into dynamic service offerings and user profiles etc. We further expect that the wireless communication market will be influenced when the user-centric network selection vision is realized. By the user-centric network selection vision, we mean that users will be free to select any available network operator or service provider on short term contractual basis. This dictates that operators will compete for their share of a common user pool on much smaller time quanta when compared with the current long term user contacts with the operators. One intuitive strategy of operators will be to incentivize users by offering different QoS and service price offers. As the operators’ offers are influenced by their incurring costs. This necessitates to study the market behavior at different levels and investigate the operator and user behavior at these level. In this paper, we categorize and position the communication players and model the interaction between players at different levels. We introduce the learning aspects in the interaction and investigate the equilibrium strategies of involved stake-holders i.e., users and operators. We also model the utility functions of all the involved stake-holders. We also examine the risk-sensitive utility functions in order to cover both risk-seeking and risk-averse in the user QoEs. We implement the user-centric approach and compare it against our proposed network-centric resource utilization and call blocking.

O1-S06.02 Impact of pill sharing on drug-resistance and population-level effectiveness of a wide-scale oral PrEP intervention in resource-constrained settings

BackgroundIn 2010 two randomised trials suggested that pre-exposure prophylaxis (PrEP) products based on tenofovir, an antiretroviral drug either administered daily orally (oral PrEP) or applied topically (vaginal microbicides), significantly reduced...

Applications of Both Cloud Computing and E-government in Taiwan

Cloud computing helps improve E-government execution effectiveness and create new business opportunities. Cloud computing is an evolution of web based internet application and describes a new supplement, consumption, and delivery model for IT and ICT services based on the Internet. It enables sharing of resources and costs across a large pool of users while providing on-demand services with dynamic scalability. This paper takes a close look at global trend and studies global practices of egovernment projects and strategies. This so-called the “Next Generation Internet” in e-government makes use of the advancements in IT and GIS to improve the policy efficiency, effectiveness and knowledge management. Taiwan’s government has targeted cloud computing as the focus of both egovernment and industry development for further advance its technologies and applications. Egovernment projects focus on the build-up of Information Technology infrastructure and the delivery of web based government services. Its successful implementation can elevate the future of Taiwan will be to the rank of both information technology & information and communication technology leadership.

On the Convergence of Genetic Scheduling Algorithms for Downlink Transmission in Multi-User MIMO Systems

In a multi-user MIMO system using a successive precoding method such as dirty paper coding, it is combinatorially complex to determine the optimal set of users to schedule and the proper order to encode their signals in order to optimize a utility function in a scheduling algorithm. Genetic algorithms represent a fast suboptimal approach to reducing the complexity of the search. In this paper, we build upon prior work that implements scheduling via genetic algorithms. We examine the impact of parameter values within the adaptive mutation rate of the algorithm on its convergence time. We demonstrate that although there is a range of values for the parameters that yields similar near-minimum convergence times, it is nonetheless important to ensure that the parameters are tuned to be within that range. In one case, tuning the parameter values reduces the time of convergence to less than 30% compared to that achievable with the initial parameter values. We also demonstrate that the proper parameter values are dependent on both the number of transmit antennas and the number of users in the pool of users to be scheduled. A simple equation is proposed that is linear in the adaptive mutation parameters to tune the values for different numbers of transmit antennas and users.

An efficient incremental face annotation for large scale web services

This paper proposes an incremental face annotation framework for sharing and publishing photographs which contain faces under a large scale web platform such as a social network service with millions of users. Unlike the conventional face recognition environment addressed by most existing works, the image databases being accessed by the large pool of users can be huge and frequently updated. A reasonable way to efficiently annotate such huge databases is to accommodate an adaptation of model parameters without the need to retrain the model all over again when new data arrives. In this work, we are particularly interested in the following issues related to increment of data: (i) the huge number of images being added at each instant, (ii) the large number of users joining the web each day, and (iii) the large number of classification systems being added at each period. We propose an efficient recursive estimation method to handle these data increment issues. Our experiments on several databases show that our proposed method achieves an almost constant execution time with comparable accuracy relative to those state-of-the-art incremental versions of principal component analysis, linear discriminant analysis and support vector machine.

Efficient Transmission Schemes for Multiuser MIMO Downlink with Linear Receivers and Partial Channel State Information

Downlink of a multiuser MIMO system is considered, in which the base station (BS) and the user terminals are both equipped with multiple antennas. Efficient transmission schemes based on zero-forcing (ZF) linear receiver processing, eigenmode transmission, and partial channel state information (CSI) at the BS transmitter are proposed. The proposed schemes utilize a handshaking procedure between the BS and the users to select (schedule) a subset of users and determine the precoding matrix at the BS. The advantage of the proposed limited feedback schemes lies in enabling relatively low-complexity user scheduling algorithms and high sum-rate throughput, even for a small pool of users. For large user pools and when the number of antennas at each user terminal is at least equal to the number of antennas at the BS, we show that the proposed scheme is asymptotically optimum.

A Distributed Protocol to Serve Dynamic Groups for Peer-to-Peer Streaming

Peer-to-peer (P2P) streaming has been widely deployed over the Internet. A streaming system usually has multiple channels, and peers may form multiple groups for content distribution. In this paper, we propose a distributed overlay framework (called SMesh) for dynamic groups where users may frequently hop from one group to another while the total pool of users remain stable. SMesh first builds a relatively stable mesh consisting of all hosts for control messaging. The mesh supports dynamic host joining and leaving, and will guide the construction of delivery trees. Using the Delaunay Triangulation (DT) protocol as an example, we show how to construct an efficient mesh with low maintenance cost. We further study various tree construction mechanisms based on the mesh, including embedded, bypass, and intermediate trees. Through simulations on Internet-like topologies, we show that SMesh achieves low delay and low link stress.

Unitary Beamforming Multi-User MIMO System with Efficient User Scheduling Algorithm

This letter proposes a new practical multiuser MIMO (MU-MIMO) scheme, which is an evolution of the well-known Per User Unitary beamforming Rate Control (PU2RC) proposed for 3GPP-LTE and IEEE802.16m standards. The proposed scheme includes an efficient user scheduling algorithm which alleviates the major weakness of the conventional PU2RC. Numerical results show that the proposed scheme provides notable performance improvement especially with small and medium user pool since it effectively exploits the benefit from large codebook size.

Where is the Missing Credit Card Debt? Clues and Implications

I create comparable estimates of aggregate credit card use based on household data from the Survey of Consumer Finances (SCF) and industry data. The two sources match up well on credit card charges and fairly well on account totals. But the SCF always yields much lower estimates of revolving debt. My estimated lower bound for the discrepancy in 2004 is half of the revolving credit card debt total implied by industry data. There is no obvious source for this remaining discrepancy and some evidence that the discrepancy has grown over time. Such growth is worrisome because it parallels substantial changes in credit card use and in the pool of credit card users, suggesting that the discrepancy could be driven by household underreporting that is correlated with unobserved heterogeneity. This correlation could confound inference on the relationship between credit card borrowing and outcomes of interest like household financial condition, consumption paths, and portfolio choice. Given this possibility it is critical to continue developing evidence on whether and why household surveys undercount credit card borrowing.

WHERE IS THE MISSING CREDIT CARD DEBT? CLUES AND IMPLICATIONS

I create comparable estimates of aggregate credit card use based on household data from the Survey of Consumer Finances (SCF) and industry data. The two sources match up well on credit card charges and fairly well on account totals. But the SCF always yields much lower estimates of revolving debt. My estimated lower bound for the discrepancy in 2004 is half of the revolving credit card debt total implied by industry data. There is no obvious source for this remaining discrepancy and some evidence that the discrepancy has grown over time. Such growth is worrisome because it parallels substantial changes in credit card use and in the pool of credit card users, suggesting that the discrepancy could be driven by household underreporting that is correlated with unobserved heterogeneity. This correlation could confound inference on the relationship between credit card borrowing and outcomes of interest like household financial condition, consumption paths, and portfolio choice. Given this possibility it is critical to continue developing evidence on whether and why household surveys undercount credit card borrowing.

Beef Up Your Competitor: A Model of Advertising Cooperation Between Internet Search Engines

We propose a duopoly model of competition between internet search engines endowed with different technologies and study the effects of an agreement where the more advanced firm shares its technology with the inferior one. We show that the superior firm enters the agreement only if it results in a large enough increase in demand for advertising space at the competing firm and a relatively small improvement of the competitor's search quality. Although the superior firm gains market share the agreement is beneficial for the inferior firm as the later firm's additional revenues from a higher advertising demand outweigh its losses due to a smaller user pool. If the cooperation takes place it is likely to be in line with the advertisers' interests and to be detrimental to users' welfare.

Serials indexing: from journals to databases

The user pool for these publications is vast, with access varying from professional-mediated searching to search-engine keyword searching by individuals at their home PC - just one consideration to be borne in mind during the indexing process, a process which differs in many aspects from back-of-the-book indexing. For example, terminology that develops over time needs to be cross-referenced in detail. Locators have to include year or volume number. Indexing of journal articles for databases requires the use of controlled vocabularies and thesauri. Newspaper indexes may include reference to columns, individual sections and different editions. And the cumulation of serials indexes needs careful management if consistency is to be maintained, something which may militate against interim indexing through the year, although this does have advantages. Negotiation of staged payments is acceptable. An experienced serials indexer helps you through the maze.

Mobile termination and collusion, revisited

The standard model by Laffont et al. (RAND Journal of Economics, 29(1): 1–37, 1998a; 38–56, 1998b) treats termination fees as an instrument to increase market power in a one-shot game of horizontal product differentiation. A prediction (Gans and King, Economics Letters, 71: 413–420, 2001) within this framework is that, with non-linear tariffs, firms should be interested in low termination fees. This seems to be at odds with regulatory experience in many countries. We offer an alternative approach, using an infinitely repeated Bertrand competition. We focus on symmetrical calling patterns and investigate simple two-part tariffs for two customer types, as well as general non-linear tariffs for two types and for a continuum of types. In this framework, when looking also at collusion in retail prices, termination fees make deviations from the collusive outcome less attractive. The optimum deviation strategy is usually to try to attract the high valuation customers since they exhibit the highest profits. Thus, a deviator will have a pool of heavy users which will have more outgoing than incoming calls, implying net termination payments. A cooperatively chosen termination rate can increase the deviator’s cost and thereby always stabilizes collusion.

Efficient Sum Rate Maximization and Resource Allocation in Block-Diagonalized Space-Division Multiplexing

For space-division multiplexing (SDM) via block diagonalization on multiuser multiple-input multiple-output (MIMO) wireless downlink, it is shown that receive antenna selection (RAS) is necessary for maximizing the achievable sum rate. This is true even when all receive antennas are equipped with radio frequency (RF) chains and RAS reduces the upper bound on the broadcast sum capacity, and when the orthogonalized channels use optimal processing. Similarly, spatial-mode selection (SMS) is necessary for sum rate maximization when receive-weight matrices are used for spatial-mode allocation. RAS/SMS may release transmission resources that can fully be utilized via additional user scheduling to yield further sum rate gains. Optimal user selection for sum rate maximization is subsumed within an exhaustive RAS/SMS process for multiantenna terminals, and both selection processes become identical for single-antenna terminals. RAS/SMS thus helps reduce the performance gap from the optimal sum capacity even for small user pool sizes. A block antenna/mode selection approach is introduced to help overcome the drawbacks of existing algorithms. Since RAS/SMS involves antenna/mode ranking, a systematic method for resource allocation with sum rate loss minimization is inherently provided. This way, a streamlined process that combines user selection, RAS/SMS, and resource allocation is developed for sum rate maximization of block-diagonalized SDM.

Performance of Orthogonal Beamforming for SDMA With Limited Feedback

On the multiantenna broadcast channel, the spatial degrees of freedom support simultaneous transmission to multiple users. The optimal multiuser transmission, which is known as dirty paper coding, is not directly realizable. Moreover, close-to-optimal solutions such as Tomlinson-Harashima precoding are sensitive to channel state information (CSI) inaccuracy. This paper considers a more practical design called per user unitary and rate control (PU2RC), which has been proposed for emerging cellular standards. PU2RC supports multiuser simultaneous transmission, enables limited feedback, and is capable of exploiting multiuser diversity. Its key feature is an orthogonal beamforming (or precoding) constraint, where each user selects a beamformer (or precoder) from a codebook of multiple orthonormal bases. In this paper, the asymptotic throughput scaling laws for PU2RC with a large user pool are derived for different regimes of the signal-to-noise ratio (SNR). In the multiuser interference-limited regime, the throughput of PU2RC is shown to logarithmically scale with the number of users. In the normal SNR and noise-limited regimes, the throughput is found to scale double logarithmically with the number of users and linearly with the number of antennas at the base station. In addition, numerical results show that PU2RC achieves higher throughput and is more robust against CSI quantization errors than the popular alternative of zero-forcing beamforming if the number of users is sufficiently large.