As successfully adopted in standard long code scenarios, belief propagation (BP) decoding has been considered a promising universal decoding candidate for next-generation wireless communications. However, when applied to short codes, BP decoding suffers from poor error correction performance due to harmful cycle structures in the Tanner graph. In this paper, we address this issue by designing a structured, sparse parity-check matrix (ssPCM) framework, composed of multiple cycle-free parity-check row blocks (PCRBs). The resulting ssPCMs feature regular row weights and perform better than the state-of-theart 4 -cycle-free row redundant PCMs across Bose-Chaudhuri-Hocquenghem (BCH) codes of length 63.

Belief propagation (BP) decoding has been recognized for its capacity-approaching performance and high throughput when decoding long low-density parity-check (LDPC) codes. However, the application of BP decoding for short codes is hindered by dense parity-check matrices (PCMs) and prevalent short cycles in the Tanner graph. In this paper, we introduce a general method to extract an optimized sparse PCM for short binary block codes, which removes length-four cycles and enhances the connectivity of short cycles to enable BP decoding with improved performance. Notably, for short binary codes with lengths up to 64, our BP decoding performance approaches the maximum likelihood bound and surpasses the best-reported BP results with reduced computational complexity. Compared with other universal decoding algorithms, BP decoding using our extracted sparse PCMs is competitive in terms of both error-rate performance and computational complexity. These promising results suggest that our method to improve BP decoding for short codes is a step toward a practical universal BP decoder for next-generation communication systems.

Next-generation channel coding has stringent demands on throughput, energy consumption, and error rate performance while maintaining key features of 5G New Radio (NR) standard codes such as rate compatibility, which is a significant challenge. Due to excellent capacity-achieving performance, spatially-coupled low-density parity-check (SC-LDPC) codes are considered a promising candidate for next-generation channel coding. In this paper, we propose an SC-LDPC code family called edge-spreading Raptor-like (ESRL) codes. Unlike other SC-LDPC codes that adopt the structure of existing rate-compatible LDPC block codes before coupling, ESRL codes maximize the possible locations of edge placement and focus on constructing an optimal coupled matrix. Moreover, a new graph representation called the unified graph is introduced. This graph offers a global perspective on ESRL codes and identifies the optimal edge reallocation to optimize the spreading strategy. We conduct comprehensive comparisons of ESRL codes and 5G-NR LDPC codes. Simulation results demonstrate that when all decoding parameters and complexity are the same, ESRL codes have obvious advantages in error rate performance and throughput compared to 5G-NR LDPC codes in some specific scenarios (low and high number of iterations), making them a promising solution towards next-generation channel coding.

In this paper, we describe a frame-interleaving hardware architecture for a generalized node-based successive cancellation list (SCL) decoder. By efficiently reusing otherwise idle computational units, two independent frames can be decoded simultaneously, resulting in a significant throughput gain. Based on this new architecture, we also exploit graph ensembles to diversify the decoding, enhancing the error-correcting performance by 0.28 dB and reducing the worst-case latency for serial graph processing by over 32%. Implementation results show that the proposed SCL decoder with frame-interleaving architecture achieves a throughput of 7.15 Gbps and an area efficiency of 37.63 Gbps/mm2, which is 1.56× and 1.11× better than the state-of-the-art node-based SCL decoders.

5G New Radio (NR) has stringent demands on both performance and complexity for the design of low-density parity-check (LDPC) decoding algorithms and corresponding VLSI implementations. Furthermore, decoders must fully support the wide range of all 5G NR blocklengths and code rates, which is a significant challenge. In this paper, we present a high-performance and low-complexity LDPC decoder, tailor-made to fulfill the 5G requirements. First, to close the gap between belief propagation (BP) decoding and its approximations in hardware, we propose an extension of adjusted min-sum decoding, called generalized adjusted min-sum (GA-MS) decoding. This decoding algorithm flexibly truncates the incoming messages at the check node level and carefully approximates the non-linear functions of BP decoding to balance the error-rate and hardware complexity. Numerical results demonstrate that the proposed fixed-point GA-MS has only a minor gap of 0.1 dB compared to floating-point BP under various scenarios of 5G standard specifications. Secondly, we present a fully reconfigurable 5G NR LDPC decoder implementation based on GA-MS decoding. Given that memory occupies a substantial portion of the decoder area, we adopt multiple data compression and approximation techniques to reduce 42.2% of the memory overhead. The corresponding 28nm FD-SOI ASIC decoder has a core area of 1.823 mm$^{2}$and operates at 895 MHz. It is compatible with all 5G NR LDPC codes and achieves a peak throughput of 24.42 Gbps and a maximum area efficiency of 13.40 Gbps/mm$^{2}$at 4 decoding iterations.

Node-based successive cancellation list (SCL) decoding has received considerable attention in wireless communications for its significant reduction in decoding latency, particularly with 5G New Radio (NR) polar codes. However, the existing node-based SCL decoders are constrained by sequential processing, leading to complicated and data-dependent computational units that introduce unavoidable stalls, reducing hardware efficiency. In this paper, we present a frame-interleaving hardware architecture for a generalized node-based SCL decoder. By efficiently reusing otherwise idle computational units, two independent frames can be decoded simultaneously, resulting in a significant throughput gain. Based on this new architecture, we further exploit graph ensembles to diversify the decoding space, thus enhancing the error-correcting performance with a limited list size. Two dynamic strategies are proposed to eliminate the residual stalls in the decoding schedule, which eventually results in nearly$2 \times $throughput compared to the state-of-the-art baseline node-based SCL decoder. To impart the decoder rate flexibility, we develop a novel online instruction generator to identify the generalized nodes and produce instructions on-the-fly. The corresponding 28nm FD-SOI ASIC SCL decoder with a list size of 8 has a core area of 1.28 mm2 and operates at 692 MHz. It is compatible with all 5G NR polar codes and achieves a throughput of 3.34 Gbps and an area efficiency of 2.62 Gbps/mm2 for uplink (1024, 512) codes, which is$1.41 \times $and$1.69 \times $better than the state-of-the-art node-based SCL decoders.

Recent developments in large language models open doors for Artificial Intelligence and robots to augment knowledge workers and teams in a variety of domains, such as customer service, data science, legal work, and software development. In this article, we review 317 articles from multiple disciplines and summarize the insights in a theoretical framework linking key robot attributes to human perceptions and behaviors. The robot attributes include embodiment, nonverbal and verbal communication, perceived gender and race, emotions, perceived personality, and competence. The outcomes include human perceptions, acceptance, engagement, compliance, trust, and willingness to help. We identify four differences between one human and one robot settings and team settings and use them as the springboard to generalize insights from the literature review to the design and impact of a robot in assisting humans in knowledge work teams. We report two high-level observations around the interplay among robot attributes and context dependent designs and discuss their implications.

Wikipedia has been the poster child for large-scale online open collaboration while few other online open collaboration initiatives have achieved similar success. How did Wikipedians do it? Besides the technical infrastructure, what social dynamics and processes are critical to its success? This essay reviews 217 articles that examined aspects of the behaviors of Wikipedia editors and the processes through which they coordinate and collaborate. Using the Input-Mediator-Output-Input model (IMOI) as the organizing framework, we summarized the key insights in an integrative review. The input factors include editors, their motivations, and the tools they use to support their work. The mediating factors include coordination, governance, leadership, conflict, newcomer socialization, and roles. The outcome focuses on measuring and predicting contribution quantity and quality. We hope our work serves as a road map for researchers who are interested in Wikipedia to learn about prior research and identify future research directions.

Turbo codes have been successfully adopted in 4G LTE, which can approach the channel capacity with Bahl-Cocke-Jelinek-Raviv (BCJR) decoding. With the evolution from 4G LTE to 5G NR, there is a demand to design a unified channel decoder that supports both LTE Turbo codes and NR low-density parity-check (LDPC) codes. One solution is to employ belief propagation (BP) decoding on the bipartite Tanner graph for both codes. However, although MacKay pointed out that Turbo codes have a sparse parity-check matrix, the existence of 4-cycles in such a matrix severely deteriorates the performance of BP decoding. In this paper, we propose two polynomial-based methods to optimize the parity-check matrix of Turbo codes by improving the sparsity while also removing 4-cycles and even 6-cycles compared to the original matrix. Simulation results show that the improved BP decoding for Turbo codes halves the error-correction performance gap between the original BP decoding and BCJR decoding, which is a promising step towards the unified channel decoder design based on the BP algorithm.

The recently proposed recursive projection-aggregation (RPA) decoding algorithm for Reed-Muller codes has received significant attention as it provides near-ML decoding performance at reasonable complexity for short codes. However, its complicated structure makes it unsuitable for hardware implementation. Iterative projection-aggregation (IPA) decoding is a modified version of RPA decoding that simplifies the hardware implementation. In this work, we present a flexible hardware architecture for the IPA decoder that can be configured from fully-sequential to fully-parallel, thus making it suitable for a wide range of applications with different constraints and resource budgets. Our simulation and implementation results show that the IPA decoder has 41% lower area consumption, 44% lower latency, four times higher throughput, but currently seven times higher power consumption for a code with block length of 128 and information length of 29 compared to a state-of-the-art polar successive cancellation list (SCL) decoder with comparable decoding performance.

Compared with the bit-wise successive cancellation list (SCL) decoding of polar codes, the node-based Fast SCL decoding significantly reduces the decoding latency by identifying special constituent codes and decoding these in parallel. To further reduce the latency of current Fast SCL decoders, we first propose a fast sequence repetition (SR) node-based SCL (Fast SR-SCL) decoding algorithm, which only involves one type of node in the SCL decoding tree. Furthermore, we employ the adaptive path splitting (APS) strategy to terminate the path splitting in the SR node early, without degrading the error-correcting performance. Numerical results show that for 5G uplink codes with a length of 1024 and rates of 1/4, 1/2, and 3/4, our decoder can deliver the same decoding performance while reducing the average latency by 34.5%, 38.0%, and 39.6% compared with the state-of-the-art Fast SCL decoder for a list size L = 8.

Since the inherent serial nature of successive cancellation list (SCL) decoding results in a long latency, belief propagation (BP) decoding for polar codes has drawn attention for high-throughput applications. However, its error correction performance is inferior to that of SCL decoding. Therefore, the bit-flipping strategy has been recently applied to BP decoding, which can approach the SCL decoding performance through multiple additional decoding attempts. The original BP flip (BPF) decoding suffers from an inaccurate identification of erroneous bits by a fixed flip set (FS), which has been improved by the generalized BPF (GBPF) decoding. In this article, the GBPF decoding is extended to support multiple bits being flipped in one decoding attempt. In addition, for two types of decoding errors: detected errors and undetected errors, we propose two novel methods to more effectively identify erroneous bits. For detected errors, the concept of loop sets is defined and a loopbased identification method is introduced based on the study of error patterns of BP decoding. On the other hand, a method to generate a more accurate fixed FS is proposed for undetected errors, which considers the bit error distribution under BP decoding. Combining the two methods, the GBPF with merged sets (GBPF-MS) decoding can achieve the SCL-8 performance and outperforms the state-of-the-art BPF, BP list, and SC flip (SCF) decoding, for polar codes with length 1024 and information rate 1/2. Implemented by 40nm CMOS technology, the proposed GBPF-MS decoder with ten flips exhibits an average throughput of 4.19 Gbps at 2.5 dB, which is 1.6× and 1.72× faster than the state-of-the-art SCL-4 and SCF decoders, respectively.

We study the impact and interplay of social design features on the engagement behaviors toward user-generated content on Facebook business pages. By examining the introduction of the “Reactions” feature on Facebook, we aim to understand how the introduction of a new engagement feature affects the overall engagement activities and the use of existing engagement features. We found evidence of a positive effect of Reactions on overall engagement levels. Furthermore, the introduction of the Reactions feature had heterogeneous effects on the use of existing engagement features. Posts that received Reactions also ended up receiving more Likes and Comments than what they would have received before the feature change. However, the opposite is true for posts that received no Reactions, although the effect sizes were small. These effects were detected within the first four weeks after the feature introduction, and persisted after six months, indicating long-term structural changes in users’ engagement behaviors.

Productive and dedicated members are critical to the success of online production communities like Wikipedia. Many communities organize in subgroups where members voluntarily work on projects of shared interest. In this paper, we investigate how members' pre-joining connections with the subgroup predict their productivity and withdrawal after joining. Drawing insights from attachment theories in social psychology, we examine two types of pre-joining connections: textit{identity-based} attachment (how much members' interests were aligned with the subgroup's topics) and textit{bonds-based} attachment (how much members had interacted with other members of the subgroup). Analyses of 79,704 editors in 1,341 WikiProjects show that 1) both identity-based and bonds-based attachment increased editors' post-joining productivity and reduced their likelihood of withdrawal; 2) identity-based attachment had a stronger effect on boosting direct contributions to articles while bonds-based attachment had a stronger effect on increasing article and project coordination, and reducing member withdrawal.

Nearly any group is subject to turnover : some people leave, while others join. Turnover can be especially high in online groups, since participation typically is strictly voluntary. We investigated the effects of member turnover in online groups, specifically in Wikipedia's WikiProjects. We based our studies on theories from organizational science, which suggest that it is not just the amount of turnover, but the characteristics of those leaving and those joining that matter. We characterized leavers and newcomers by their prior productivity, tenure (in the group or community), and participation in other groups within the larger community. Furthermore, we considered the moderating effect of group size on turnover. We analyzed data from 88,427 editors who participated in 1,054 WikiProjects, finding that (1) the positive effects of newcomers to a group were larger than the negative effects of leavers, (2) prior productivity, tenure, and participation in other groups all played significant roles, and (3) the effects of leavers and newcomers were amplified in larger groups.

The design of complex social systems, such as online communities, requires the consideration of many parameters, a practice at odds with social science research that focuses on the effects of a small set of variables. In this article, we show how synthesizing insights from multiple, narrowly focused social science theories in an agent-based model helps us understand factors that lead to the success of online communities. The agent-based model combines insights from theories related to collective effort, information overload, social identity, and interpersonal attraction to predict motivations for online community participation. We conducted virtual experiments to develop hypotheses around three design decisions about how to orchestrate an online community—topical breadth, message volume, and discussion moderation—and the trade-offs involved in making these decisions. The simulation experiments suggest that broad topics and high message volume can lead to higher member commitment. Personalized moderation outperforms other types of moderation in increasing members' commitment and contribution, especially in topically broad communities and those with high message volume. In comparison, community-level moderation increases commitment but not contribution, and only in topically narrow communities. These simulation results suggest a critical trade-off between informational and relational benefits. This research illustrates that there are many interactions among the design decisions that are important to consider; the particulars of the community's goals often determine the effectiveness of some decisions. It also demonstrates the value of agent-based modeling in synthesizing simple social science theories to describe and prescribe behaviors in a complex system, generating novel insights that inform the design of online communities.

Dedicated and productive members who actively contribute to community efforts are crucial to the success of online volunteer groups such as Wikipedia. What predicts member productivity? Do productive members stay longer? How does involvement in multiple projects affect member contribution to the community? In this paper, we analyze data from 648 WikiProjects to address these questions. Our results reveal two critical trade-offs in managing online volunteer groups. First, factors that increase member productivity, measured by the number of edits on Wikipedia articles, also increase likelihood of withdrawal from contributing, perhaps due to feelings of mission accomplished or burnout. Second, individual membership in multiple projects has mixed effects. It decreases the amount of work editors contribute to both the individual projects and Wikipedia as a whole. It increases withdrawal for each individual project yet reduces withdrawal from Wikipedia. We discuss how our findings expand existing theories to fit the online context and inform the design of new tools to improve online volunteer work.

The "wisdom of crowds" argument emphasizes the importance of diversity in online collaborations, such as open source projects and Wikipedia. However, decades of research on diversity in offline work groups have painted an inconclusive picture. On the one hand, the broader range of insights from a diverse group can lead to improved outcomes. On the other hand, individual differences can lead to conflict and diminished performance. In this paper, we examine the effects of group diversity on the amount of work accomplished and on member withdrawal behaviors in the context of WikiProjects. We find that increased diversity in experience with Wikipedia increases group productivity and decreases member withdrawal -- up to a point. Beyond that point, group productivity remains high, but members are more likely to withdraw. Strikingly, no such diminishing returns were observed for differences in member interest, which increases productivity and decreases member withdrawal in a linear fashion. Our results suggest that the low visibility of individual differences in online groups may allow them to harvest more of the benefits of diversity while bearing less of the cost. We discuss how our findings can inform further research of online collaboration.

Watching video online is becoming increasingly popular, and new video streaming technologies have the potential to transform video watching from a passive, isolating experience into an active, socially engaging experience. However, the viability of an active social experience is unclear: both chatting and watching video require attention, and may interfere with one another and detract from the experience. In this paper, we empirically examine the activity of chatting while watching video online. We examine how groups of friends and strangers interact, and find that chat has a positive influence on social relationships, and people chat despite being distracted. We discuss the benefits and opportunities provided by mixing chat and video, uncover some of the attentional and social challenges inherent in this combination of media, and provide guidance for structuring the viewing experience.

Many small online communities would benefit from increased diversity or activity in their membership. Some communities run the risk of dying out due to lack of participation. Others struggle to achieve the critical mass necessary for diverse and engaging conversation. But what tools are available to these communities to increase participation? Our goal in this research was to spark contributions to the movielens.org discussion forum, where only 2% of the members write posts. We developed personalized invitations, messages designed to entice users to visit or contribute to the forum. In two field experiments, we ask (1) if personalized invitations increase activity in a discussion forum, (2) how the choice of algorithm for intelligently choosing content to emphasize in the invitation affects participation, and (3) how the suggestion made to the user affects their willingness to act. We find that invitations lead to increased participation, as measured by levels of reading and posting. More surprisingly, we find that invitations emphasizing the social nature of the discussion forum increase user activity, while invitations emphasizing other details of the discussion are less successful.