Simultaneous Users Research Articles

Environmentally Controlled Microfluidic System Enabling Immune Cell Flow and Activation in an Endothelialised Skin-On-Chip.

Integration of reconstructed human skin (RhS) into organ-on-chip (OoC) platforms addresses current limitations imposed by static culturing. This innovation, however, is not without challenges. Microfluidic devices, while powerful, often encounter usability, robustness, and gas bubble issues that hinder large-scale high-throughput setups. This study aims to develop a novel re-usable multi-well microfluidic adaptor (MMA) with the objective to provide a flexible tool for biologists implementing complex 3D biological models (e.g., skin) while enabling simultaneous user control over temperature, medium flow, oxigen (O2), nitrogen (N2), and carbon dioxide (CO2) without the need for an incubator. The presented MMA device is designed to be compatible with standard, commercially available 6-well multi-well plates (6MWPs) and 12-well transwells. This MMA-6MWP setup is employed to generate a skin-on-chip (SoC). RhS viability is maintained under flow for three days and their morphology closely resembles that of native human skin. A proof-of-concept study demonstrates the system's potential in toxicology applications by combining endothelialised RhS with flowing immune cells. This dynamic setting activates the monocyte-like MUTZ-3 cells (CD83 and CD86 upregulation) upon topical exposure of RhS to a sensitizer, revealing the MMA-6MWP's unique capabilities compared to static culturing, where such activation is absent.

Parenting style of parents undergoing substance abuse treatment having adolescent children (12–20 years old) referring to addiction treatment clinics in Bojnurd

BackgroundConsidering the adverse effect of drug abuse on Parenting, this study was conducted to determine the parenting style of parents undergoing substance abuse treatment who were referred to addiction treatment clinics in Bojnurd in 2021. MethodsThe type of cross-sectional study was descriptive-analytical. The sample size was 360 parents with adolescent children (12–20 years old) undergoing substance abuse treatment who were included in the study by simple random sampling. A two-part questionnaire, including personal characteristics questions and Bamrind's parenting style questionnaire, was used to collect information. Data analysis was done using SPSS 23 software with parametric T-test, ANOVA, and non-parametric equivalent tests of Spearman's correlation at a significance level of 0.05. ResultsThe average score of permissive, authoritarian, and authoritative parenting styles was (16.15±5.92), (18±6.34) and (24.89±7.09) respectively. Men used permissive and authoritarian parenting styles significantly more than women. The people living in the village, compared to the city residents, and the people in the Turkish and Kurdish ethnicities, compared to Fars, significantly used authoritarian parenting style more. People using opioids significantly less preferred the permissive method and the authoritarian method compared to stimulant drug users and simultaneous users of stimulant and opioid drugs. ConclusionChildren of parents with substance abuse disorders are at risk of various adverse consequences, and it seems that inconsistent behavior of parents is an essential cause of this risk; therefore, the need for public education regarding Parenting, especially in addicted parents, is raised.

Enhancing the Multi-User Experience in Fully Autonomous Vehicles Through Explainable AI Voice Agents

Fully autonomous vehicles (FAVs) operated by AI voice agents create a unique multi-user environment without a traditional driver, allowing users to engage in diverse activities such as entertainment and rest. In addition to the convenience of vehicle control, these agents face the challenge of resolving conflicts arising from multiple simultaneous user commands. This study investigates whether AI voice agents can effectively manage these command conflicts and enhance the multi-user experience (MUX). The research was conducted in two phases: In the preliminary study, online focus group interviews (FGIs) were conducted with 10 participants to explore their perceptions of using AI voice agents in FAVs. Participants shared their experiences and watched a concept video to discuss their expectations of FAV agents. Based on the FGI results, explainable AI voice agents were designed to prevent user conflicts between user commands, focusing on user tendencies and conflict contexts. In the main study, multi-user interactions with these agents were evaluated through online experiments with 89 participants. Two specific experiments were conducted based on the sources of conflict identified in the preliminary study: the first focused on control authority and the second on speech overlap. Participants watched scenario videos and assessed five variables, including sense of agency, trust, problem-solving ability, disappointment, and safety. The findings suggest that explanations provided by AI voice agents can effectively mitigate conflicts and improve MUX in FAVs. However, the effectiveness of these explanations varied across different contexts, indicating the need for alternative approaches. This research provides valuable insights for designing MUXs that prevent multi-user conflicts and meet user expectations in FAV.

Supporting VoIP communication in IEEE 802.11ax networks: A new admission control and scheduling resource allocation scheme

The current IEEE 802.11ax standard enhances Wi-Fi networks with a series of new features, such as multi-user (MU) transmission, an Orthogonal Frequency Division Multiple Access (OFDMA) scheme and the ability to multiplex traffic from different access categories (ACs). These features can be utilized to enhance the QoS support for VoIP traffic and optimize the usage of IEEE 802.11ax network resources. This work proposes a new scheme to multiplex VoIP calls in IEEE 802.11ax MU frames and a new scheduler and resource allocation algorithm specifically designed for VoIP data traffic. Our scheduler allocates VoIP packets requiring longer transmission times into the same frame(s), minimizing the channel air-time assigned to VoIP transmission. In addition, unused radio resources in the MU frame are leveraged to transmit best-effort packets along with VoIP packets. For completeness, we also define a call admission control (CAC) algorithm that anticipates channel saturation conditions to ensure VoIP users can maintain a guaranteed level of QoS. Based on simulation results, our scheme is more efficient in reducing channel utilization than other schedulers such as multi-user round-robin (RR) (implemented by ns-3) or single-user FIFO. For example, for 30 VoIP stations using the G.711 codec under mixed channel conditions, our scheme reduces by 30% the air-time required to transmit VoIP packets. When coupled with the ability to also send best-effort packets along with VoIP packets, this translates into a higher throughput (i.e. 10 Mbit/s vs 4 Mbit/s) and more simultaneous VoIP users with guaranteed QoS (up to 46 VoIP users vs 26 and 28 users for the multi-user RR and single-user FIFO scheduling algorithms, respectively).

Gazing Heads: Investigating Gaze Perception in Video-Mediated Communication

Videoconferencing has become a ubiquitous medium for collaborative work. It does suffer however from various drawbacks such as zoom fatigue. This paper addresses the quality of user experience by exploring an enhanced system concept with the capability of conveying gaze and attention. Gazing Heads is a round-table virtual meeting concept that uses only a single screen per participant. It enables direct eye contact, and signals gaze via controlled head rotation. The technology to realise this novel concept is not quite mature though, so we built a camera-based simulation for four simultaneous videoconference users. We conducted a user study comparing Gazing Heads with a conventional “Tiled View” video conferencing system, for 20 groups of 4 people, on each of two tasks. The study found that head rotation clearly conveys gaze and strongly enhances the perception of attention. Measurements of turn-taking behaviour did not differ decisively between the two systems (though there were significant differences between the two tasks). A novel insight in comparison to prior studies is that there was a significant increase in mutual eye contact with Gazing Heads, and that users clearly felt more engaged, encouraged to participate and more socially present. Overall, participants expressed a clear preference for Gazing Heads. These results suggest that fully implementing the Gazing Heads concept, using modern computer vision technology as it matures, could significantly enhance the experience of videoconferencing.

A Multi-User Virtual Reality Social Connecting Space for People Living with Dementia and Their Support Persons: A Participatory Action Research Study

Digital technologies such as virtual reality (VR) are increasingly designed and implemented to support people living with dementia who are at risk of loneliness and/or social isolation. Multi-user VR (MUVR), which involves simultaneous user engagement and a sense of being present together in VR, may promote and maintain social connectedness between people living with dementia and their support persons. This paper focuses on Phase 4 of a larger participatory action research (PAR) project, which aimed to explore the usability, acceptability and feasibility of a MUVR application and its potential to support the social connectedness of people living with dementia and their support persons. The study involved five people living with dementia and their five support persons, who trialed the application in their homes over two PAR cycles. The researcher gathered feedback through individual semi-structured interviews and observational field notes. Reflexive thematic analysis guided qualitative data analysis, and the findings suggested that MUVR is a usable, acceptable, and feasible application for this population. The findings also indicated that MUVR shows promise in promoting or maintaining social connectedness among people living with dementia and their support persons. Nonetheless, further refinement is necessary to enhance the usability, acceptability and feasibility of the MUVR application, and these areas of refinement are presented in this paper, through design recommendations for future work.

At the Heart of the Mothercrystal: Final Fantasy XIV’s Approach to Localization and Lore as a Virtual Contact Zone

<p>Virtual worlds by nature of their persistence and ability to have multiple simultaneous users in the same space can act as contact zones, defined by Mary Louse Pratt as a "social space where disparate cultures meet, clash, and grapple with each other, often in highly asymmetrical relations of domination and subordination," (1991, p. 34). One affordance of virtual worlds in constructing the contact zone is the ability for the developer to use localization to bridge language gaps between a user and the virtual world and, to some extent, between players who have a shared understanding of the virtual world. This understanding extends to the properties of objects and locations and any narrative lore or background in the world. However, localization can be a double-edged sword, with choices in translation and localization leading to confusion among virtual world users and conflict between users and developers. </p><p>Language impacts two aspects of the virtual contact zone. For one, players communicate using languages they are proficient in, using whatever affordances are available in the interface and paratextual platforms, such as the official forums and social mediaplatforms like Reddit and Tumblr. For another, the world itself is awash in language. That text manifests itself in gameplay elements from user abilities and item names to more narrative elements such as character names, dialogue, and written story and worldbuilding elements. These textual and narrative components, called "lore," are essential in contextualizing virtual spaces. Lore helps build the virtual world beyond the actual mechanics and interactions within a virtual space. Lore gives users a sense of not just place but of geography, not just time, but of history, and not just context for players but their place within the story of the virtual world. Lore offers players motivation for playing in addition to traditional gameplay motivators such as exploration, achieving, socializing, and defeating enemies or other players (Yee, 2006; Bartle, 1996) to interact with the world. </p><p>This paper focuses on the case of Final Fantasy XIV: A Realm Reborn (FFXIV), an MMORPG initially released in 2013, its production, approaches to localization,and how it contributes to building a "virtual contact zone." In looking at specific instances where controversies in translation and localization led to confusion and conflict among the participants and developers of the game, this case study illustrates the role of localization in games beyond translation and acculturation. Localization not only serves as the linguistic bridge among members of the contact zone but, in the case of online games where world-building and narrative are important aspects for immersion and play, creates shared experiences and understandings of that virtual world among all members of the virtual contact zone.</p>

Impact of Latency on QoE, Performance, and Collaboration in Interactive Multi-User Virtual Reality

Interactive, multi-user experiences are meant to define the present and future of Virtual Reality (VR). Such immersive experiences will typically consist of remote collaborations where content is streamed and/or synchronized over a network connection. Thus, real-time collaboration will be key. In this light, the responsiveness of the system and the network will define the overall experience. As such, understanding the effect of network distortions, especially related to time delay, on end-user’s perception (in terms of Quality-of-Experience (QoE)), performance, and collaboration becomes crucial. The existing literature, however, has mostly focused on network requirements from a system point-of-view, where the key performance parameters are only provided in the form of Quality-of-Service (QoS) parameters (such as end-to-end latency). However, the translation of these network impairments to the end-user experience is often omitted. The purpose of this paper is to fill the gap by providing a thorough investigation of the impact of latency on the perception of users while performing collaborative tasks in multi-user VR. To this end, an experimental framework was designed, developed, and tested. It is based on a multi-device synchronizing architecture, enabling two simultaneous users to work together in a gamified virtual environment. The developed test environment also allows for the identification of the most prominent network requirements and objective analysis for each traffic link. To experimentally investigate the impact of latency on user perception, a user study was conducted. Participants were paired and asked to perform the collaborative task under different latency-prone scenarios. The results show that users are able to easily distinguish between distorted and non-distorted network configurations. However, making a distinction between different manifestations of latency is much less straightforward. Moreover, factors such as the user’s role in the experience and the required task, and the level of interactivity and movement have an important influence on the subjective level of perception, the strength of the user’s preferences, and the occurrence of cybersickness. In contrast, no significant differences in objective metrics, such as system performance and user completion time were observed. These results can support the creation of collective QoE metrics that model the group as a whole rather than each individual separately. As such, this work provides an important step to dynamically counteract any drops in group dynamics and performance by means of smart interventions in the transmission system and/or virtual environment.

Associations between simultaneous use of alcohol and cannabis and cannabis-related problems in 2014–2016: evidence from the Washington panel survey

BackgroundTo address the research question of how simultaneous users of alcohol and cannabis differ from concurrent users in risk of cannabis use problems after the recreational marijuana legalization in Washington State.MethodsWe used generalized estimating equations with a Poisson distribution to analyze the association between simultaneous use of alcohol and marijuana (SAM) and cannabis-related problems compared to concurrent use. The data is a longitudinal sample of drinkers and cannabis users (n = 257, 47% female) aged 18 years and older from Washington State in 2014–2016. We adjusted for survey weights to account for differential probability of selection and response rates. The primary outcome is the past-six-month CUDIT problem subscale (ranging from 0 to 28), which is the total score for seven CUDIT problem items, after excluding the three items that covered marijuana use frequency. Covariates include marijuana use frequency (daily/near daily use, regular use, or infrequent use), marijuana daily quantity, alcohol daily volume, panel survey cycle, medical marijuana recommendation, driving time to nearest marijuana outlet, age of marijuana use onset, and other demographics.ResultsAfter adjusting for covariates, we found that compared to concurrent use, SAM was significantly positively associated with CUDIT problem subscale (IRR = 1.68, 95% CI: 1.25–2.27, p < 0.001); daily/near daily use of marijuana was strongly significantly associated with CUDIT problem subscale compared with infrequent use (IRR = 5.1, 2.71–9.57, p < 0.001) or regular use (IRR = 3.05, 1.91–4.85, p < 0.001). Secondary analyses using CUDIT total score as the outcome also showed a significant positive association with SAM compared to concurrent use (IRR = 1.17, 1.02–1.34, p < 0.05).ConclusionsThis study highlighted the importance of SAM, in addition to cannabis use frequency for predicting cannabis-related problems.

Performance investigation of 1.5 Tb/s optical hybrid 2D-OCDMA/OFDM system using direct spectral detection based on successive weight encoding algorithm

In order to raise the performance of optical communication systems, it is imperative mainly to increase the number of available users while decreasing the bit error rate (BER) in the required spectral width. This can be challenging in optical multiplexing systems including incoherent optical code division multiplexing (OCDMA). In this respect, an interesting two-dimensional hybrid spectral/spatial OCDMA system using orthogonal frequency division multiplexing (OFDM) technology based on successive weight (SW) coding has been investigated. Using the zero cross-correlation (ZCC) feature, the novel approach declined the effect of phase-induced intensity noise (PIIN), and multi-user interference (MUI) at the receiver has been fully eradicated. When compared to systems with Modified Double Weight (MDW), Flexible Cross Correlation (FCC), and two-dimensional hybrid Flexible Cross-Correlation - Modified Double Weight 2D-MDW/FCC codes, numerical findings demonstrate that our proposed system is more efficient, increasing the number of simultaneous users to 350, and achieving a higher overall transfer rate towards 1.5 Tb/s under the required optical communication conditions.

IMetaTown: A Metaverse System with Multiple Interactive Functions Based on Virtual Reality.

This work aims to pioneer the development of a real-time interactive and immersive Metaverse Human-Computer Interaction (HCI) system leveraging Virtual Reality (VR). The system incorporates a three-dimensional (3D) face reconstruction method, grounded in weakly supervised learning, to enhance player-player interactions within the Metaverse. The proposed method, two-dimensional (2D) face images, are effectively employed in a 2D Self-Supervised Learning (2DASL) approach, significantly optimizing 3D model learning outcomes and improving the quality of 3D face alignment in HCI systems. The work outlines the functional modules of the system, encompassing user interactions such as hugs and handshakes and communication through voice and text via blockchain. Solutions for managing multiple simultaneous online users are presented. Performance evaluation of the HCI system in a 3D reconstruction scene indicates that the 2DASL face reconstruction method achieves noteworthy results, enhancing the system's interaction capabilities by aiding 3D face modeling through 2D face images. The experimental system achieves a maximum processing speed of 18 frames of image data on a personal computer, meeting real-time processing requirements. User feedback regarding social acceptance, action interaction usability, emotions, and satisfaction with the VR interactive system reveals consistently high scores. The designed VR HCI system exhibits outstanding performance across diverse applications.

Construction of Online Interactive Teaching Platform for Drama, Film and Television Majors Based on Fuzzy Multi-Objective Decision Making Algorithm

Abstract This study introduces a multi-objective decision-making model tailored for developing an educational platform, blending economic considerations with the platform’s operational constraints. It employs a fuzzy set approach for algorithm design, utilizing a method that minimizes deviations in membership values for solving. The research culminates creating an online interactive teaching platform for drama and film studies. This platform is architecturally founded on the B/S framework, incorporates functional modules derived from its educational objectives, and utilizes MySQL for data flow design. Comparing it to conventional teaching methods, a comprehensive evaluation demonstrates its practical application in real-world teaching scenarios. Performance tests reveal module response times between 2.7 to 3.0 seconds, with compatibility tests ranging from 0.11 to 0.36 seconds. Under a load of 200 simultaneous users, the database connection pool maintains an optimal size of about 35 connections, with thread counts near 50 and zero idle database connections. The study also quantifies the platform’s impact on various educational aspects, showing correlation coefficients for learning attitude (0.88), motivation (0.50), behavior (0.72), and teacher-student (0.15) as well as student-student interactions (0.27) with the learning effectiveness of the platform.

Bit Error Rate Performance in CDMA Free Space Optical Links with SIK Receiver under Fog Conditions

This article presents a novel analytical method for evaluating fog's impact on Bit Error Rate (BER) in an Optical Code Division Multiple Access (OCDMA) Free Space Optical (FSO) connection. The investigation employs an optical encoder and direct detection receiver employing a balanced photo detector with Sequence Inverse Keying (SIK) to explore fog effects. By scrutinizing multi-access interference (MAI) current and signal current values at the SIK receiver's output under varied fog conditions, we deduce BER expressions for diverse scenarios. These encompass different fog thickness levels, code lengths, simultaneous users, and system parameters. The results reveal substantial OCDMA degradation due to fog thickness and users. Also, the system incurs a marked power penalty at a specific BER, especially with higher fog and user density. However, we identify a potential solution: increasing code length, effectively mitigating fog-induced performance decline.

Multi-side incentive compatible transaction fee mechanism

Propelled by ongoing advances in blockchain technologies, transaction volumes of major cryptocurrencies like Bitcoin and Ethereum have surged, causing strain on network capacities—a challenge known as the scarcity of transaction inclusion resources. While the widely adopted Transaction Fee Mechanism (TFM) efficiently allocates transaction resources, existing research falls short in achieving simultaneous user incentive compatibility (UIC), miner incentive compatibility (MIC), and miner-user side contract proofness (SCP), essential for blockchain security. In response, we propose the Optimal Revenue Burning (ORB) mechanism, adjusting reserve price and burning rate to deter deviations from honest strategies. Our theoretical analysis strongly supports that ORB mechanism simultaneously satisfy UIC, MIC, and SCP. We also outline conditions for equilibrium strategies. Through simulations, ORB mechanism not only ensures stable miner revenue but also reduces user payments by an average of 5.34%, addressing exorbitant transaction fees. Our research has significant implications for guiding blockchain TFM design.

Optimization and Scalability of Educational Platforms: Integration of Artificial Intelligence and Cloud Computing

The intersection between technology and education has taken on unprecedented relevance, driven by the promise of transforming teaching and learning through advanced digital tools. This study proposes a comprehensive exploration of how cloud computing and artificial intelligence converge to impact education, focusing on accessibility, efficiency, and quality of learning. A mixed-research design identified a 25% improvement in the personalization of educational content thanks to AI and a 60% increase in simultaneous user capacity through cloud computing. Additionally, a significant reduction in administrative errors and improvements in scalability were observed without sacrificing quality. The results demonstrate that these technologies not only improve efficiency and accessibility in education but also enrich the learning experience. By comparing these findings with previous research, this study highlights the synergistic value of these technologies and positions itself as a critical resource to guide future developments and improvements in the education sector in a digitally advanced world.

Design of smart farming communication and web interface using MQTT and Node.js

Abstract The sustainable development goals (SDGs) are a UN agenda that has been approved by all UN member states. The SDGs have 17 targets, one of which is to eliminate hunger. In 2050, the world’s population is expected to reach 9.7 billion people. Improved soil and water management, according to the World Resources Institute, is one of the options for feeding 10 billion people sustainably by 2050. In comparison to conventional farming, smart and precision farming produces higher productivity at a lower cost. Based on the search for literature studies related to the development of agricultural technology, it was found that communication methods and online interfaces still require further improvement. The steps for developing the system are designing the architecture and end-to-end communication flow, designing use case diagrams, designing entity-relationship diagrams, designing user flow diagrams, implementing the system through code development, and finally testing the system. Planned communication and web design for precision smart agriculture are implemented effectively. The MQTT is used to communicate with the Node.js server worker. Data from numeric image feeds and images are directly processed by the system. The server will store all received data, including numeric data and live feeds, for future use. The back end of the website has many functions such as dataset management, device management, user administration, firmware management, control management, and live image feed management are some of the capabilities available. When 100 users access the system simultaneously, the RAM usage on the server is 167 MB. RAM utilization reaches 389 MB when 400 users access the system simultaneously. The limit for simultaneous user connections to the web interface is 400 users. The maximum number of devices that can be connected simultaneously via MQTT communication is 900.

Simultaneous Alcohol and Cannabis Use and High-Risk Sexual Behaviors.

Alcohol and cannabis use rates are highest in college-aged young adults, and both alcohol and cannabis use are independently related to high-risk sexual behaviors (HRSBs). HRSBs (e.g., sex without protection against sexually transmitted infections) are a prevalent public health problem in college students, with little research examining simultaneous alcohol and cannabis use (i.e., using both alcohol and cannabis at the same time so the effects overlap) and HRSBs. We examined simultaneous alcohol and cannabis-related HRSB frequency, gender differences in simultaneous alcohol and cannabis-related HRSBs, and differences in HRSBs between simultaneous and non-simultaneous users. Alcohol and cannabis using college students (N = 534; Average Age = 19; 66.9% reported identifying as female) were recruited through a psychology department's human subjects research pool and completed a one-time, online, self-report survey. One-third of participants engaged in simultaneous alcohol and cannabis use prior to sexual intercourse in the past 3 months. Additionally, over one-third of participants reported heavy drinking (4/5 or more drinks for women/men) simultaneously with cannabis use prior to sexual intercourse in the past 3 months. Simultaneous alcohol and cannabis use was significantly and positively related to sexual intercourse after simultaneous use and after heavy drinking simultaneously with cannabis use. Past year simultaneous alcohol and cannabis users, relative to non-simultaneous users, reported increased incidents of sex without protection against sexually transmitted infections. No gender differences in simultaneous alcohol and cannabis-related HRSBs were found. Future research should continue examining simultaneous alcohol and cannabis use and HRSBs.

Examining Differences in Emotion Dysregulation Between Emerging Adult Alcohol-Only Users, Abstainers, and Simultaneous Users.

Simultaneous use of alcohol and cannabis is associated with more negative consequences than use of either substance alone. Research suggests that emotion dysregulation is linked to alcohol, cannabis, and polysubstance use. However, no previous research has examined whether emotion dysregulation scores differ among individuals without past month substance use (abstainers), individuals who report past-month alcohol use only (no past month cannabis or simultaneous use; alcohol-only users), and individuals who engage in past-month simultaneous alcohol and cannabis use (simultaneous users). Our aim was to examine differences in overall levels of emotion dysregulation and emotion dysregulation subscales between these groups. The sample included 468 college students. Participants completed an online survey assessing demographics, emotion dysregulation, average number of drinks per week, days of monthly cannabis use, and simultaneous use of alcohol and cannabis. A one-way ANOVA showed significant differences in emotion dysregulation between alcohol-only users, abstainers, and simultaneous users. A Bonferroni post hoc analysis revealed significant differences in emotion dysregulation for simultaneous users (p = .004) compared to alcohol-only users and abstainers. A series of ANOVAs were run to examine emotion dysregulation subscale scores and significant differences were found for impulse control difficulties (p = .003) and limited access to emotion regulation strategies (p = .005) for simultaneous users compared to alcohol-only users and abstainers, and for non-acceptance of emotional responses (p = .018) for simultaneous users compared to and alcohol-only users. These findings indicate that simultaneous users have higher levels of emotion dysregulation, higher levels of impulse control difficulties, greater non-acceptance of emotions, and greater lack of access to emotion regulation strategies compared to abstainers and alcohol-only users.

Maximal (v, k, 2, 1) Optical Orthogonal Codes with k = 6 and 7 and Small Lengths

Optical orthogonal codes (OOCs) are used in optical code division multiple access systems to allow a large number of users to communicate simultaneously with a low error probability. The number of simultaneous users is at most as big as the number of codewords of such a code. We consider (v,k,2,1)-OOCs, namely OOCs with length v, weight k, auto-correlation 2, and cross-correlation 1. An upper bound B0(v,k,2,1) on the maximal number of codewords of such an OOC was derived in 1995. The number of codes that meet this bound, however, is very small. For k≤5, the (v,k,2,1)-OOCs have already been thoroughly studied by many authors, and new upper bounds were derived for (v,4,2,1) in 2011, and for (v,5,2,1) in 2012. In the present paper, we determine constructively the maximal size of (v,6,2,1)- and (v,7,2,1)-OOCs for v≤165 and v≤153, respectively. Using the types of the possible codewords, we calculate an upper bound B1(v,k,2,1)≤B0(v,k,2,1) on the code size of (v,6,2,1)- and (v,7,2,1)-OOCs for each length v≤720 and v≤340, respectively.

Efficiency enhancement of long-reach passive optical network using the polarization coding

Abstract This paper, propose a new passive optical network (PON) system structure based on the two orthogonal polarization states of the same wavelength. This method is usually applied to increase the number of simultaneous users in the network, it can double the number of potential users. The proposed technique utilized to increase split ratio and consequently increase the reach and the split ratio. This can be achieved by implementing technologies such as power splitter. In terms of bit rate, the proposed PON offers a bit rate of 10 Gbps for downstream transmissions. The results obtained in this work are shown that the proposed system can accommodate more users simultaneously for the typical Q factor is greater than 6.