UAV-Assisted Dynamic Avatar Task Migration for Vehicular Metaverse Services: A Multi-Agent Deep Reinforcement Learning Approach

Avatars, as promising digital representations and service assistants of users in Metaverses, can enable drivers and passengers to immerse themselves in 3D virtual services and spaces of UAV-assisted vehicular Metaverses. However, avatar tasks include a multitude of human-to-avatar and avatar-to-avatar interactive applications, e.g., augmented reality navigation,which consumes intensive computing resources. It is inefficient and impractical for vehicles to process avatar tasks locally. Fortunately, migrating avatar tasks to the nearest roadside units(RSU)or unmanned aerial vehicles(UAV) for execution is a promising solution to decrease computation overhead and reduce task processing latency, while the high mobility of vehicles brings challenges for vehicles to independently perform avatar migration decisions depending on current and future vehicle status. To address these challenges, in this paper, we propose a novel avatar task migration system based on multi-agent deep reinforcement learning(MADRL) to execute immersive vehicular avatar tasks dynamically. Specifically, we first formulate the problem of avatar task migration from vehicles to RSUs/UAVs as a partially observable Markov decision process that can be solved by MADRL algorithms. We then design the multi-agent proximal policy optimization(MAPPO) approach as the MADRL algorithm for the avatar task migration problem. To overcome slow convergence resulting from the curse of dimensionality and non-stationary issues caused by shared parameters in MAPPO, we further propose a transformer-based MAPPO approach via sequential decision-making models for the efficient representation of relationships among agents. Finally, to motivate terrestrial or non-terrestrial edge servers(e.g., RSUs or UAVs) to share computation resources and ensure traceability of the sharing records, we apply smart contracts and blockchain technologies to achieve secure sharing management. Numerical results demonstrate that the proposed approach outperforms the MAPPO approach by around 2% and effectively reduces approximately 20% of the latency of avatar task execution in UAV-assisted vehicular Metaverses.

Achieving 500X Acceleration for Adversarial Robustness Verification of Tree-Based Smart Grid Dynamic Security Assessment

Dear Editor,This letter presents a novel and efficient adversarial robustness verification method for tree-based smart grid dynamic security assessment(DSA).Based on tree algorithms technique,the data-driven smart grid DSA has received significant research interests in recent years.

Federated Learning for 6G Communications:Challenges,Methods,and Future Directions

As the 5G communication networks are being widely deployed worldwide,both industry and academia have started to move beyond 5G and explore 6G communications.It is generally believed that 6G will be established on ubiquitous Artificial Intelligence(AI)to achieve data-driven Machine Learning(ML)solutions in heterogeneous and massive-scale networks.However,traditional ML techniques require centralized data collection and processing by a central server,which is becoming a bottleneck of large-scale implementation in daily life due to significantly increasing privacy concerns.Federated learning,as an emerging distributed AI approach with privacy preservation nature,is particularly attractive for various wireless applications,especially being treated as one of the vital solutions to achieve ubiquitous AI in 6G.In this article,we first introduce the integration of 6G and federated learning and provide potential federated learning applications for 6G.We then describe key technical challenges,the corresponding federated learning methods,and open problems for future research on federated learning in the context of 6G communications.

基于区块链和贝叶斯博弈的联邦学习激励机制

联邦学习通过聚合多方本地模型成为数据共享的新模式.现有的联邦学习激励机制有效缓解了完全信息下的数据供给不足问题,但仍面临搭便车、不公平、不可信等挑战.为此,本文提出了一种基于区块链和贝叶斯博弈(Bayesian game)的不完全信息联邦学习激励机制,通过量化数据供给方的成本效用与数据需求方的支付报酬对数据交易过程建模,采用沙普利值(Shapley value)实现了数据供给方报酬分配的公平性.在交易模型中考虑到参与个体的异质性与隐私保护,将数据供给方的资源配置策略构建为不完全信息的贝叶斯博弈模型,通过优化本地模型训练策略实现对数据供给方的激励作用.本文进一步分析了激励机制的有效性与行动策略的可信性,提出一种隐私保护的贝叶斯博弈行动策略共识算法(privacy-preserving Bayesian game action strategy consensus algorithm,PPBG-AC),该算法使数据供给方在基于区块链的数据交易平台下实现了贝叶斯纳什均衡.方案对比与理论分析表明本文提出的不完全信息联邦学习激励机制保障了数据供给方利益分配的公平性与资源配置的可信性,基于实际公开数据集的仿真实验与性能评估验证了激励机制的有效性.

6G-Enabled Edge AI for Metaverse:Challenges, Methods,and Future Research Directions

Sixth generation(6G)enabled edge intelligence opens up a new era of Internet of everything and makes it possible to interconnect people-devices-cloud anytime,anywhere.More and more next-generation wireless network smart service applications are changing our way of life and improving our quality of life.As the hottest new form of next-generation Internet applications,Metaverse is striving to connect billions of users and create a shared world where virtual and reality merge.However,limited by resources,computing power,and sensory devices,Metaverse is still far from realizing its full vision of immersion,materialization,and interoperability.To this end,this survey aims to realize this vision through the organic integration of 6G-enabled edge artificial intelligence(AI)and Metaverse.Specifically,we first introduce three new types of edge-Metaverse architectures that use 6G-enabled edge AI to solve resource and computing constraints in Metaverse.Then we summarize technical challenges that these architectures face in Metaverse and the existing solutions.Furthermore,we explore how the edge-Metaverse architecture technology helps Metaverse to interact and share digital data.Finally,we discuss future research directions to realize the true vision of Metaverse with 6G-enabled edge AI.

A trustless architecture of blockchain-enabled metaverse

Metaverse has rekindled human beings’desire to further break space-time barriers by fusing the virtual and real worlds.However,security and privacy threats hinder us from building a utopia.A metaverse em-braces various techniques,while at the same time inheriting their pitfalls and thus exposing large attack surfaces.Blockchain,proposed in 2008,was regarded as a key building block of metaverses.it enables transparent and trusted computing environments using tamper-resistant decentralized ledgers.Currently,blockchain supports Decentralized Finance(DeFi)and Non-fungible Tokens(NFT)for metaverses.How-ever,the power of a blockchain has not been sufficiently exploited.In this article,we propose a novel trustless architecture of blockchain-enabled metaverse,aiming to provide efficient resource integration and allocation by consolidating hardware and software components.To realize our design objectives,we provide an On-Demand Trusted Computing Environment(OTCE)technique based on local trust evalua-tion.Specifically,the architecture adopts a hypergraph to represent a metaverse,in which each hyper-edge links a group of users with certain relationship.Then the trust level of each user group can be evaluated based on graph analytics techniques.Based on the trust value,each group can determine its security plan on demand,free from interference by irrelevant nodes.Besides,OTCEs enable large-scale and flexible application environments(sandboxes)while preserving a strong security guarantee.