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Age of Information (AoI) is a critical performance metric for measuring information freshness in task-oriented Internet of Things (IoT) applications. In this work, we investigate how AoI impacts task-oriented multicasting in multi-cell Non-orthogonal Multiple Access (NOMA) networks, while considering the effects of inter-cell interference and multicast group size. Our findings reveal that larger group sizes lead to increased instability in AoI, but lower inter-cell interference; while smaller group sizes result in higher inter-cell interference but a smaller increase in AoI when transmission fails. To balance inter-cell interference and group size, we propose a novel AoI-aware inter-cell interference mitigation (AIM) solution, which dynamically adjusts multicast group size, schedules multicast groups for transmission, and allocates transmit power to multicast groups. We derive the optimality for achieving the lowest AoI of the AIM scheduling strategy and the upper bound of the number of scheduling groups. Our simulation results show that AIM ensures more successful transmissions and low weighted sum AoI through grouping and AoI-aware inter-cell interference mitigation. We also show that our AoI-aware grouping scheme outperforms random grouping and fixed grouping, as well as evolutionary-based genetic algorithm grouping, by modeling the grouping problem as a multi-armed bandit problem and solving it using the $\epsilon $ -greedy method. To the best of our knowledge, this is the first study to examine the AoI problem of task-oriented IoT applications in multi-cell multicast NOMA networks.

Multi-view videos (MVV) have emerged to provide users with immersively interactive experiences with 3D multimedia content. Compared with traditional 2D videos, MVV offers multiple view angles to avoid generating occluded regions from a single viewpoint and allows users to receive different view angles, which consume much higher bandwidth. In this paper, we leverage multicast and view synthesis to effectively reduce the number of transmitted views and total bandwidth consumption in software-defined content delivery networks (SD-CDN). By exploiting the SDN architecture, SD-CDN can optimize traffic engineering and the selection of multi-view sources to serve users. We formulate a new optimization problem, Online Multicast with View Synthesis (OMVS), prove the NP-hardness, and design an online algorithm with the ideas of View Popularity Cost Ratio, View Watching Possibility, and synthesis tree, to achieve the tightest competitive ratio. The experiment on real networks and implementation in an experimental SDN manifest that the proposed algorithm outperforms state-of-the-art algorithms regarding the total cost, bandwidth consumption, synthesis quality, and link and node utilization.

Previous research on SDN multicast traffic engineering mainly focused on intra-domain optimization. However, the main traffic on the Internet is inter-domain, and the selection of border nodes and sharing of network information between domains are usually distributed but ignored in previous works. In this article, we explore multi-domain online distributed multicast traffic engineering (MODMTE). To effectively solve MODMTE, we first prove that MODMTE is inapproximable within $|D_{\max }|$|Dmax|, which indicates that it is impossible to find any algorithm with a ratio better than $|D_{\max }|$|Dmax| for MODMTE, and $|D_{\max }|$|Dmax| is the maximum number of destinations for a multicast tree. Then, we design a $|D_{\max }|$|Dmax|-competitive distributed algorithm with the ideas of Domain Tree, Dual Candidate Forest Construction, and Forest Rerouting to achieve the tightest performance bound for MODMTE. Experiments on a real SDN with YouTube traffic manifest that the proposed distributed algorithm can reduce more than 30% of the total cost of bandwidth consumption and rule updates for multicast tree rerouting compared with the state-of-the-art algorithms.

Widespread applications based on the Internet of Things (IoT) are driving the adoption of digital twins (DTs) to optimize operations and increase efficiency. However, the development of DT-empowered IoT systems has put forward a series of new requirements for the in-depth mining of comprehensive data. The first is how to ensure that the fusion results of data from a large number of connected physical and virtual entities scattered in heterogeneous networks are always better than data from the physical or virtual world alone. The second is how to effectively coordinate the interaction between physical entities and virtual entities to optimize the operation and management of IoT services. This article proposes a novel DT architecture to build various feature-rich virtual entities, and introduces a new concept of DT data liquidity to orchestrate physical-to-physical, physical-to-virtual, and virtual-to-virtual interactions of intelligent IoT functions. A federated learning method based on a two-phase optimization scheme is also developed to optimize the data liquidity of the DT system through orchestrated cloud-edge-device DT collaboration to provide high fault tolerance and reliability IoT services. Performance evaluation results on the CIRFAR10-LT benchmark and two real-world datasets show that the proposed method outperforms the state-of-the-art methods in terms of convergence, accuracy and generalization ability.

In this work, we study secure and trusted authentication of unmanned aerial vehicles (UAVs) in 5G networks. Existing centralized UAV identity authentication mechanisms may only be able to verify the identity of the UAV itself or manage pilots, which are far from complete protection of legal access. Some recent works on UAV identity management are based on blockchain technology, in which UAV identities are generated through the blockchain software wallets, so they may be vulnerable to UAV identity forgery. To tackle the challenges described above, we propose an authentication mechanism based on a dual-identity (dual-ID) model for UAVs in 5G networks via a cross-layer design of SIM cards, blockchain, and smart contracts. The proposed self-sovereign UAV identity management procedure will then jointly process the authentications of both the UAV device and its pilot through the blockchain hardware wallets embedded in 5G SIM cards. In this way, a global registry of a unique identifier of each UAV device and each pilot can be ensured, and the identity forgery problem can also be avoided. Due to the limited power and processing capacity of UAV devices and the need of quick response for authentication, we employ 5G and multi-access edge computing (MEC) servers for communication and processing. To validate the proposed solution, a developed proof-of-concept system is tested through the 5G MEC testbed at National Taiwan University to demonstrate the flexibility and usability of UAV authentication.

The 5G private network is expected to provide low latency, high data rate, and improved security to meet various key requirements of enterprise vertical applications. However, existing 4G LTE or 5G private network multi-access edge computing solutions mainly focus on homogeneous systems and ignore the interoperability of various coexisting access technologies in the enterprise area. Therefore, their access domains are independent, and to communicate directly with each other is difficult without additional network components. In this article, we propose a novel mobile edge platform called multi-access intelligent A+ (MIA+), which has built-in support for service continuity and consistency of wireless connections in private 5G heterogeneous networks (HetNets). We particularly demonstrate how to ensure that MIA+ provides customers with promised services in different access domains, including Wi-Fi, 4G LTE, 5G public bands, and 5G private bands. The services promised to MIA+ users include consistent service provisioning, seamless handover, interworking among various access domains, and seamless integration between 5G private band and public band systems. To demonstrate the flexibility and usability of the MIA+ system, a proof of concept has been tested in the Chunghwa Telecom (CHT) 5G experimental network in Taiwan. The results show that MIA+ is indeed an excellent solution for realizing private 5G HetNets.

This paper explores the issues of multicasting for mobile hosts using IETF Mobile IP. Mobile IP suggests two approaches for mobile multicasting, namely, remote subscription (MIP-RS) and bi-directional tunneling (MIP-BT). While having the advantage of optimal routing efficiency, MIP-RS uses a naive join-and-leave policy for mobile hosts to participate in the groups of interest and causes serious packet losses while roaming. MIP-BT is free from packet losses due to roaming; however, MIP-BT and its modification MoM suffer from the triangle routing problem, resulting in inefficient routing and wastage of system resources. In this paper, we propose a new mobile multicasting protocol called Mobile Multicast with Routing OPtimization (MMROP) that employs a modified join-and-leave mechanism, and routes the missing data sequence due to the 'out-of-synch' problem to other agents in the adjacent networks via tunneling for roaming terminals. With MMROP, the mobility agent (foreign or home agent) in Mobile IP, in addition to mobility management, is extended to assist multicasting for mobiles. The mobility agent is not necessarily a multicast router. From the perspective of the multicast router, the mobility agent is a group participant, and from the mobiles, the agent serves as the proxy of multicast services. As a result, MMROP enjoys no packet losses from roaming as in MIP-BT, and optimal routing efficiency as in MIP-RS. We also conducted a simulation study and developed a cost analytical model to evaluate the performance of MMROP, in comparison to MIP-RS, MIP-BT, and MoM. The results demonstrate that MMROP has optimal routing efficiency, low delivery cost and high robustness, as compared to other approaches.

Multi-access edge computing (MEC) is a key technology for enabling various services in 5G applications. Existing works mainly focus on the key technologies of MEC. In this article, we, as a mobile operator, share our experience with a self-developed MEC system, called 5G Intelligent A+, for 5G private networks. This system is inline and transparent, and is located between the base station (BS) and the mobile core network. Therefore, it is not affected by changes in the BS and core network, and does not require pre-configuration. We demonstrate the key functions of the system, including versatile conditions for local breakout, flexible network access management, on-demand bandwidth allocation based on mobile subscriber ISDN number, time, and location. We also show how to support inter-region access via an innovative tunneling mechanism called tunnel MEC (T-MEC). We then demonstrate that the system can efficiently provide enterprises with diverse services, which can be performed online and in real time. This MEC system works well with many types of access networks and is applicable to non-standalone and standalone (SA) 5G networks. The proof of concept has been tested in Taiwan to prove the flexibility and usability of the MEC system. In addition, some functions and applications were also demonstrated at the Mobile World Congress 2018 and 2019.

Energy efficiency is an important focus area of 5G mobile technology. Due to global warming, it is important to lower the global CO2 footprint, even with the expectation of massively increasing cellular data traffic. The ability of HetNets to support high capacity makes it a significant driver for the success of 4G and indispensable in 5G. Small cells equipped with cognitive radio (CR) techniques could improve spectrum utilization by opportunistic spectrum access and intelligent interference mitigation. In this article, we propose an RF-CoHetNet, a novel heterogeneous cellular network system where small cells possess CR capabilities and are wirelessly powered by electromagnetic RF-energy. Under this system architecture, both energy efficiency and spectral efficiency can be achieved by properly switching small cells to harvesting mode or allocating channels/power to serve their users. We show that RF-energy harvesting can provide a promising solution to further improve the energy efficiency of the whole system. Through RF-energy harvesting, the unavoidable interference turns out to be a useful energy resource to support partial power consumption in the small cell. We further propose a heuristic algorithm to minimize the total system energy consumption under the system capacity constraint. From the numerical results, we give some insights into the possibility of RF-CoHetNet deployment.

AbstractIn this paper, we develop a formal framework for what a good community should look like and how strong a community is (community strength). One of the key innovations is to incorporate the concept of relative centrality into structural analysis of networks. In our framework, relative centrality is a measure that measures how important a set of nodes in a network is with respect to another set of nodes, and it is a generalization of centrality. Building on top of relative centrality, the community strength for a set of nodes is measured by the difference between its relative centrality with respect to itself and its centrality. A community is then a set of nodes with a nonnegative community strength. We show that our community strength is related to conductance that is commonly used for measuring the strength of a small community. We define the modularity for a partition of a network as the average community strength for a randomly selected node. Such a definition generalizes the original Newman's modularity and recovers the stability in as special cases. For the local community detection problem, we also develop efficient agglomerative algorithms that guarantee the community strength of the detected local community.

This paper proposes a new protocol called MQ, Multicast with QoS, which supports multimedia group communications with QoS guarantees for heterogeneous recipients. With MQ, while resource reservation is de-coupled from QoS multicast routing, they are integrated in a way to avoid the problem of “sender-oriented” path determination, a problem that occurs when RSVP is used in conjunction with QoS routing for heterogeneous reservations. Being a truly receiver-oriented and integrated scheme for multimedia multicasting, MQ supports such integration in a robust, scalable and loop-free way, accommodates heterogeneous users with varied QoS, dynamically adjusts QoS trees to improve resource utilization, and benefits from being an integrated mechanism to ensure end-to-end QoS services. We have also conducted simulations to evaluate the performance of MQ. MQ demonstrates its advantages to conventional loosely coupled integration of IP multicasting, resource reservation and QoS routing, in terms of better accommodation of heterogeneous users, higher scalability, lower blocking probability for users to join groups with service guarantee, and more efficient resource utilization to enhance system performance.

Abstract.: Without user interactions, multimedia presentations are just fancy slide shows with sound and video supports. User interactions by themselves do not change the temporal relationships among multimedia objects, such as texts, graphics, images, audio, and video, but affect the playback schedules. In this paper, we propose a synchronization mechanism to guarantee the quality of multimedia presentation with user interactions. In our protocol, each presentation site requests media transmission from the required media servers at certain time intervals prior to the playback deadlines, where these time intervals are the response times to cover possible experienced end-to-end delays and packet losses, and waits for an initial setup time to ensure intermedia synchronization before starting the presentation. Users may interact with the presentation. This synchronization mechanism solves the problems incurred by user interactions by determining the new presentation scenario produced by the interactive operation, calculating the corresponding setup time, and then rendering the new playback and retrieval schedules.