Dimitrios Karvounas

5G on the Horizon: Key Challenges for the Radio-Access Network

Toward the fifth generation (5G) of wireless/mobile broadband, numerous devices and networks will be interconnected and traffic demand will constantly rise. Heterogeneity will also be a feature that is expected to characterize the emerging wireless world, as mixed usage of cells of diverse sizes and access points with different characteristics and technologies in an operating environment are necessary. Wireless networks pose specific requirements that need to be fulfilled. In this respect, approaches for introducing intelligence will be investigated by the research community. Intelligence shall provide energy- and cost-efficient solutions at which a certain application/service/quality provision is achieved. Particularly, the introduction of intelligence in heterogeneous network deployments and the cloud radio-access network (RAN) is investigated. Finally, elaboration on emerging enabling technologies for applying intelligence will focus on the recent concepts of software-defined networking (SDN) and network function virtualization (NFV). This article provided an overview for delivering intelligence toward the 5G of wireless/mobile broadband by taking into account the complex context of operation and essential requirements such as QoE, energy efficiency, cost efficiency, and resource efficiency.

Smart management of D2D constructs: an experiment-based approach

This article considers the concept of device-to- device communications for the resolution of persistent issues in mobile networks. Specifically, two scenarios are described, the opportunistic coverage expansion of the infrastructure, where an access point transits to offline mode (and hence its terminals shall exploit the presence of neighboring devices in order to reroute their traffic to alternative APs), as well as the opportunistic capacity expansion scenario where an AP faces congestion issues due to the excessive traffic of its terminals or the use of an obsolete RAT with low capacity. In the same manner, part of the traffic shall be offloaded to alternative APs through the creation of D2D links with neighboring devices. In order to realize the proposed solutions, the network elements exchange information regarding their capabilities and their status so as to identify the best path from all the potential ones. Therefore, control channels for cognitive radio systems will be utilized since the information that is conveyed through them comprises information from all the layers of the protocol stack. Furthermore, the article focuses on the coverage expansion scenario, which is implemented at the w.iLab-t testbed. In order to realize the D2D constructs, the devices of the testbed will be configured to communicate through WiFi technology, and specifically the 802.11s standard for wireless mesh networks, in order to enable multihop communications. In this respect, the D2D constructs that will be created are mesh networks that comprise the problematic terminals, their neighboring terminals that offload their traffic, and the APs that receive the traffic. In order to evaluate the proposed solution, the signaling loads of the conveyed messages are measured, as well as the performance of the mesh network that is created after the solution enforcement through the use of a ping, a file transfer, and a video streaming application.

Cognitive Networks for Future Internet: Status and Emerging Challenges

This work provided an overview of the cognitive networks and systems for a wireless FI by considering the current status and looking forward at the emerging challenges. Emphasis was placed on the opportunistic networking paradigm to provide an insight on research regarding operator-governed ONs that are assumed to be coordinated extension of the infrastructure. For the coordination of operator-governed ONs, cognitive management entities are introduced. Moreover, further emphasis was placed on an operator-governed, end-to-end, autonomic, joint network and services management, which was elaborated as a part of this work. Network and services management is enabled through the definition of a UMF, which has a main goal to unify and federate various research outcomes and will advance the routine management tasks to the level of governance of the entire network.semantic.

Multi-Objective Traffic Engineering for Future Networks

An important goal towards the design of Future Networks is to achieve the best ratio of performance to energy consumption and at the same time assure manageability. This paper presents a general problem formulation for Energy-Aware Traffic Engineering and proposes a distributed, heuristic Energy-Aware Traffic Engineering scheme (ETE) that provides load balancing and energy-awareness in accordance with the operators needs. Simulation results of ETE compared to the optimal network performance confirm the capability of ETE to meeting the needs of Future Networks.

Cognitive cloud-oriented wireless networks for the Future Internet

It is expected that the wireless world will migrate towards an era that will comprise more local/ temporary structures for the provision of services. A networking paradigm towards this direction is the opportunistic networking. Operator-governed ONs are dynamically created, temporary, coordinated extensions of the infrastructure. Operator governance is being realized through the use of Cognitive Management Systems which acquire the context, policies and profiles of the environment and make decisions on the creation of opportunistic networks. The paper presents an approach for exploiting such ONs in order to extend the capacity in wireless access and backhaul segments for efficient application provisioning, as well as an evaluation of indicative test cases as a proof of concept of the aforementioned approach. All these scenarios will enable the cognitive cloud-oriented vision of wireless networks for efficient application provisioning in the Future Internet era.

Resource allocation to femtocells for coordinated capacity expansion of wireless access infrastructures

As the Internet has penetrated everyday life, more and more users will demand high-quality services. However, the Internet was not designed to handle such heavy usage. Thus, networks need to be enhanced in order to deal with the increased traffic. In this study, the use of opportunistic networks (ONs) is studied. ONs are operator-governed, coordinated extensions of the infrastructure and are created dynamically for a limited time frame. The problem studied is the capacity extension of congested infrastructure via resource allocation to femtocells. More specifically, a macro base station (BS) is considered with deployed femtocells within its area. As soon as a problematic situation is discovered, the congested BS notifies the network management entity which will determine the solution method. In our case, a proportion of terminals that cause the congestion will be offloaded to the nearby femtocells relieving the macro BS. This is achieved through two approaches: a greedy algorithm that allocates the minimum possible power level to femtocells in order to acquire as much terminals as possible, and an energy-efficient algorithm that assigns the minimum possible power level to the femtocells that are required to cover specific terminals. Femtocells that are not needed are switched off.

Management of opportunistic networks through cognitive functionalities

The emerging wireless world will migrate towards an era that will comprise more local/ temporary structures for the provision of services. Opportunistic networking would be used as a networking paradigm towards this direction. Specifically, operator-governed opportunistic networks (ONs) are dynamically created, temporary, coordinated extensions of the infrastructure. Operator governance is being realized through the use of Cognitive Management Systems (CMSs) which acquire the context, policies and profiles of the environment and make decisions on the creation, maintenance or termination of opportunistic networks. This work presents an approach for elaborating on the concept of the management of opportunistic networks through cognitive functionalities. Two main CMSs are proposed namely, the Cognitive management System for the Coordination of the infrastructure (CSCI) and the Cognitive system for the Management of the Opportunistic Network (CMON). CSCIs and CMONs are making use of the common components of CMSs, i.e., the acquisition of context, policies and profiles, decision making, enforcement and learning and are used in order to manage the creation, maintenance and termination of an ON.

Evaluation of signalling load in control channels for the cognitive management of opportunistic networks

This paper proposes the data structures needed for the cognitive management of operator-governed opportunistic networks ONs, which are coordinated extensions of the infrastructure and are created dynamically and temporarily through operator policies when they are needed. The data structures are divided in five categories: profiles, context, decision, knowledge and policy. Profile information provides information on the capabilities of devices and infrastructure elements, the characteristics of applications and the requirements and preferences of users. Contextual information comprises information regarding the current status of the terminal and the infrastructure devices as well as their environment, whereas decisions include information about the creation and re-configuration of ONs, as well as information for the re-configuration of infrastructure and terminals. Knowledge information focuses on the storage of the decisions made for each occurred context, whereas the policies provide rules for context handling, in terms of objectives to be achieved, strategies to be used for the optimization and constraints to be respected. The data structures are evaluated through the capacity extension scenario, where network elements exchange messages based on the IEEE 802.21 standard in order to relieve a congested base station through the ON creation that will offload a proportion of terminals to alternative base stations. For a small network, the evaluation proves that the signalling load is around 60KB, whereas for a large network, the load is around 260KB. Copyright

Enriching self‐organizing networks use cases with opportunistic features: a coverage and capacity optimization paradigm

SUMMARY Self-organizing networks (SONs) have been introduced into long-term evolution in order to configure and optimize the network in an autonomic manner. However, in some situations the reconfiguration of the entire network is not the most cost-efficient solution. Consequently, opportunistic networks have been introduced as operator-governed, coordinated extensions of the infrastructure that are created dynamically where and when they are needed, exploiting the radio environment. This work proposes an enhanced SON functional architecture (FA) with opportunistic features in order to handle such situations through the manipulation of ONs. In addition, the proposed FA is utilized in a coverage and capacity optimization use case, where small cells are deployed in order to extend the capacity of a macro base station (BS). Users opportunistically exploit the resources (i.e. resource blocks) of the small cells. In addition, the small cells are configured to the optimal power level in order to maximize the users’ throughput without causing interference to the other users. Two different approaches of controlling the interference among the macro BS and the small cells are presented, namely soft constraint and hard constraint cases. Furthermore, apart from maximizing the users’ throughput, emphasis is given to the fairness among the users and on the quality-of-service provision through a proper resource allocation. The evaluation proved that when small cells are introduced the systems throughput is increased by 12.76% when the macro BS and the small cells cannot use the same resource blocks simultaneously (hard constraint case) and by 8.25% when the reuse is possible. Copyright

Opportunistic exploitation of resources for improving the energy-efficiency of wireless networks

Unequivocally, one of the main challenges of the arising wireless world is to support the QoS-demanding services. However, the solutions that will be considered should not only take into account the optimization of the network performance, but should also be energy efficient both for the operator and the end-user. This paper presents the concept of Opportunistic Networks (ONs) as an energy efficient method to exploit wireless networks. The case studied in this work comprises a macro base station which faces congestion issues. The proposed solution will offload the traffic from a proportion of the macro-terminals to nearby femtocells, through the creation of an ON. Therefore, the femto-terminals will operate to lower power levels leading to less energy consumption and battery savings. In addition, femtocells will operate to the minimum transmission power that is needed in order to serve the users resulting in operational expenditure savings. Results from simulations are provided to confirm the proposed solution.