Leonardo Militano

Adaptive Resource Allocation to Multicast Services in LTE Systems

This paper addresses the design of an adaptive resource allocation policy for the efficient delivery of multicast services in Long Term Evolution (LTE) systems. The proposed approach overcomes the intrinsic inefficiencies of Conventional Multicast Scheme (CMS) related to the different channel quality experienced by the involved users. The basic idea is to split any multicast group into subgroups and apply subgroup-based adaptive modulation and coding schemes, which enable a more efficient exploitation of multi-user diversity. The distribution of users into subgroups is determined by the solution of an optimization problem, aiming to improve the network throughput while guaranteeing fairness among multicast members.

Single Frequency-Based Device-to-Device-Enhanced Video Delivery for Evolved Multimedia Broadcast and Multicast Services

Despite of the undisputed benefits of the long term evolution-advanced (LTE-A) networks, offering support for group-oriented services challenges the evolved multimedia broadcast multicast services (eMBMS) design in LTE-A. This is especially important when delivering video content with high bitrate requirements. The conventional multicast scheme (CMS) is proposed as a radio resource allocation solution for eMBMS to serve all multicast group members with the data rate supported by the receiver with the worst channel conditions. In this paper, we propose a novel radio resource management approach, the device-to-device (D2D)-enhanced CMS with single frequency (D2D-SF). This proposal extends the CMS with additional D2D communications in order to increase the aggregate data rate of the cell, while also maintaining the typical CMS short-term fairness. D2D-SF makes use of one or more mobile subscriber devices as forwarding devices (FD) to retransmit the data received from the base station (BS) over direct local links to other members of the multicast group. The proposed solution supports both high-rate modulation and coding schemes on the downlink from BS to FDs, and reaches cell-edge devices (hence, experiencing worse channel conditions) through high-performing D2D links (improving this experience). Testing shows how the single frequency-based D2D CMS paradigm proposed, complemented by two novel strategies for selecting FDs, achieves significant enhancements of the overall performance when delivering video content compared to both the state-of-the-art multicast solutions and novel solutions that do not employ a single-frequency paradigm.

A Constrained Coalition Formation Game for Multihop D2D Content Uploading

This paper investigates relay-based schemes in cellular systems, where multihop device-to-device (D2D) communications are exploited for content uploading toward the eNodeB. All user equipments (UEs) are sources of their own content and form a multihop D2D chain, with the head of the chain being in charge of uploading all the generated content to the eNodeB. By pooling the cellular radio resources assigned to the D2D chain and by using high-quality short-range radio links, the proposed cooperative content uploading scheme guarantees lower upload delays than in the traditional cellular mode operation. To model the D2D chain formation in a cell and to best characterize self-interested users concerned about their own payoff, a constrained coalition formation game is defined, where each UE is a player whose cost is identified as the content upload time. The solution of the game determines the stable feasible partition for the UEs in the cell. We demonstrate through simulations that with this solution the content uploading time is reduced by 52% with respect to the traditional cellular mode.

Fair Cost Allocation in Cellular-Bluetooth Cooperation Scenarios

A promising paradigm, that answers crucial needs raised by emerging wireless applications, foresees the cooperation of multiple terminals over short-range wireless links while downloading multimedia contents over long-range cellular connections. Energy consumption reduction is just one of the potential benefits the cited communication paradigm might offer. Undoubtedly, the main issue raised by the new paradigm is to develop a model of cooperative behavior, which can best meet the expectations of all the cooperating entities. Unfortunately, classic minimization problem solutions are usually conflicting with the concept of fairness, as it is sensed by rational players. A joint use of classical optimization and game theory based approaches may contribute to overcome the highlighted dichotomy between user satisfaction and stable minimal energy cost allocations. This paper studies the interactions among users in the presence of a cooperative file-sharing service and seeks appropriate solutions to achieve the lowest energy consumption is possible while motivating users to cooperate.

Energy Efficient IoT Data Collection in Smart Cities Exploiting D2D Communications

Fifth Generation (5G) wireless systems are expected to connect an avalanche of “smart” objects disseminated from the largest “Smart City” to the smallest “Smart Home”. In this vision, Long Term Evolution-Advanced (LTE-A) is deemed to play a fundamental role in the Internet of Things (IoT) arena providing a large coherent infrastructure and a wide wireless connectivity to the devices. However, since LTE-A was originally designed to support high data rates and large data size, novel solutions are required to enable an efficient use of radio resources to convey small data packets typically exchanged by IoT applications in “smart” environments. On the other hand, the typically high energy consumption required by cellular communications is a serious obstacle to large scale IoT deployments under cellular connectivity as in the case of Smart City scenarios. Network-assisted Device-to-Device (D2D) communications are considered as a viable solution to reduce the energy consumption for the devices. The particular approach presented in this paper consists in appointing one of the IoT smart devices as a collector of all data from a cluster of objects using D2D links, thus acting as an aggregator toward the eNodeB. By smartly adapting the Modulation and Coding Scheme (MCS) on the communication links, we will show it is possible to maximize the radio resource utilization as a function of the total amount of data to be sent. A further benefit that we will highlight is the possibility to reduce the transmission power when a more robust MCS is adopted. A comprehensive performance evaluation in a wide set of scenarios will testify the achievable gains in terms of energy efficiency and resource utilization in the envisaged D2D-based IoT data collection.

Wi-Fi cooperation or D2D-based multicast content distribution in LTE-A: A comparative analysis

Exploiting short-range technologies like Wi-Fi for achieving benefits in terms of throughput and energy consumption, has been among the first proposals to enhance the data transfer performance in cellular environments. Today, with the advent of high performing Long Term Evolution-Advanced (LTE-A) systems, Device-to-Device (D2D) communication, supporting proximity based services in both licensed and unlicensed bands, has recently come into play. In the context of LTE-A systems, this paper proposes different solutions with reference to a “multicast content distribution service”. A comparative analysis between Wi-Fi cooperation and the proposed D2D-based solutions is presented and their pros and cons will be illustrated. The cases where the early conceived wireless cooperation paradigm may still be of interest will be highlighted, while service delivery enhancements obtained with D2D-based solutions will be evaluated. In particular, when compared to standard multicast solutions, content delivery time and energy savings up to respectively 40% and 80% can be obtained.

When D2D communication improves group oriented services in beyond 4G networks

The design of effective radio resource management policies for group-oriented services in beyond-4G networks is attracting the interest of the research community. Along this line, this paper analyzes some novel approaches that take advantages of the Device to Device (D2D) communication paradigm with the aim of improving the session quality experienced by mobile users in terms of delay and energy consumption. The basic idea is to enable receivers with a bad cellular link from the evolved Node B (eNodeB) to receive the multicast service through another mobile device located in proximity over a direct link. Two schemes are proposed that exploit different radio technologies to enable nearby multicast subscribers to establish direct local links, either Long Term Evolution-Advanced (LTE-A) or Wi-Fi Direct. The effectiveness of the proposed solutions is demonstrated through a comprehensive simulative analysis and compared with traditional techniques that only exploit point-to-multipoint communication from the eNodeB to all the group members not taking advantages of the multi-user diversity or alternative network technologies to serve the multicast users.

Social Virtual Objects in the Edge Cloud

The social Internet of Things (SIoT) paradigm, in which objects establish social-like relationships, presents several interesting features to improve network navigability, object trustworthiness, and interactions between elements across IoT platforms. Implementations of the SIoT model envision cyber counterparts of physical objects--social virtual objects--virtualized in the cloud. Such an approach has several advantages but suffers from a few major problems. In fact, objects might be located far from the datacenter hosting the cloud, resulting in long delays and inefficient use of communication resources. This article investigates how to address these issues by exploiting the computing resources at the edge of the network to host the virtual objects of the SIoT and provides early experimental results.

Network coding and evolutionary theory for performance enhancement in wireless cooperative clusters

SUMMARY Cooperation over short-range wireless links among user devices, which download remote contents through cellular links, is a paradigm quickly gaining ground, given that it can answer several technological and design issues that next-generation wireless applications will raise. Among others, energy consumption, data rate and data transfer time are parameters that will likely benefit from this novel communication concept. This paper presents a WLAN-based cooperative scenario, conceived to support file-sharing services, in which a sub-set of cluster nodes access, through their cellular radio interface, portions of a file to be successively exchanged among all cluster members over wireless local area network (WLAN) links. Besides showing the beneficial effects of cooperation, this paper also focuses on the performance enhancement that can be achieved when using the network coding paradigm, whose deployment revealed to be very effective in the depicted scenario. The selection of the nodes acting as sources for file injection into the cluster is a critical aspect for the effectiveness of the whole system. Therefore, the potentialities offered by the evolutionary theory applied to the specific problem are investigated and an ad hoc conceived Genetic Algorithm (GA) designed. Either the service time (the time needed for all nodes to receive the complete file) or the energy consumption for the nodes is used as objective function, showing in both cases the fast convergence for the algorithm that makes it preferable to either exhaustive searches or random choices. Copyright

Effects of Heterogeneous Mobility on D2D- and Drone-Assisted Mission-Critical MTC in 5G

mcMTC is starting to play a central role in the industrial Internet of Things ecosystem and have the potential to create high-revenue businesses, including intelligent transportation systems, energy/ smart grid control, public safety services, and high-end wearable applications. Consequently, in the 5G of wireless networks, mcMTC have imposed a wide range of requirements on the enabling technology, such as low power, high reliability, and low latency connectivity. Recognizing these challenges, the recent and ongoing releases of LTE systems incorporate support for lowcost and enhanced coverage, reduced latency, and high reliability for devices at varying levels of mobility. In this article, we examine the effects of heterogeneous user and device mobility -- produced by a mixture of various mobility patterns -- on the performance of mcMTC across three representative scenarios within a multi-connectivity 5G network. We establish that the availability of alternative connectivity options, such as D2D links and drone-assisted access, helps meet the requirements of mcMTC applications in a wide range of scenarios, including industrial automation, vehicular connectivity, and urban communications. In particular, we confirm improvements of up to 40 percent in link availability and reliability with the use of proximate connections on top of the cellular-only baseline.