Panayiotis Kolios

Future Wireless Mobile Networks

In this article, the authors outline some key benefits that stem from the use of mechanical relaying within or across the cells in future wireless mobile networks. The authors have argued that, when information messages that can be stored are elastic enough and subsequently carried by mobile nodes, before relayed to other terminals or the BS at a later time, interference and energy consumption levels can be dramatically decreased during network operation due to the locality of the transmissions. In addition, mechanical relaying allows for innovative resource-management techniques to be deployed in the network, such as providing load balancing or switching-off BSs with low levels of utilization. To fully understand the issues regarding mechanical relaying, it is necessary to examine in a more detailed manner the required architectural changes together with the implementation aspects of integrating the mechanical relaying paradigm with the current and emerging mobile networks such as LTE advanced. This will be part of our future line of enquiry.

Energy-Efficient Relaying via Store-Carry and Forward within the Cell

In this paper, store-carry and forward (SCF) decision policies for relaying within the cell are developed. The key motivation of SCF relaying stems from the fact that energy consumption levels can be dramatically reduced by capitalizing on the inherent mobility of nodes and the elasticity of Internet applications. More specifically, we show how the actual mobility of relay nodes can be incorporated as an additional resource in the system to achieve savings in the required communication energy levels. To this end, we provide a mathematical programming formulation on the aforementioned problem and find optimal routing and scheduling policies to achieve maximum energy savings. By investigating structural properties of the proposed mathematical program we show that optimal solutions can be computed efficiently in time. The tradeoffs between energy and delay in the system are meticulously studied and Pareto efficient curves are derived. Numerical investigations show that the achievable energy gains by judiciously storing and carrying information from mobile relays can grow well above 70 percent for the macrocell scenario when compared to a baseline multihop wireless relaying scheme that uses shortest path routes to the base station.

Switching off low utilization base stations via store carry and forward relaying

Recent research studies on green cellular networking indicate that most of the traffic is serviced by a few cell sites while the rest of the cells remain under-utilized, contributing to significant energy consumption levels. Previous proposals suggest turning off Base Stations (BSs) during low utilization periods to save energy by allowing neighboring cells to increase their coverage to provide the necessary connectivity. In this paper, an alternative (and also complimentary) method is proposed, based on the store-carry and forward (SCF) relaying paradigm that allows BSs with low utilization levels to be switched-off. The proposed SCF relaying scheme exploits the mobility of relay nodes to migrate traffic from BSs of very low utilization to neighbour BSs, allowing in that respect these sites to be switched off. To this end, a joint routing and scheduling problem is formulated to maximize the number of cell sites that can be switched off by also taking into account the communication cost of operating the network. Numerical investigations reveal that significant energy gains can be attained using the proposed SCF relaying scheme for switching off BSs.

Ultra Low Energy Store-Carry and Forward Relaying within the Cell

In this paper we address the issue of store-carry and forward (SCF) relaying within a cell in a mobile network. The proposed scheme can be considered as a generalization of various multihop wireless relaying schemes, where storing and carrying an information message by a mobile relay node is not allowed. The key motivation of utilizing SCF relaying within the cell is that energy consumption levels can be dramatically reduced by capitalizing on the inherent mobility of nodes and the elasticity of Internet applications. In that respect, we consider a novel multihop cellular architecture to achieve energy savings both at the network side (i.e., Base Stations) and at the user terminals. The proposed scheme makes use of mobility information of relays (vehicles) while roaming inside the cell to device flows that could achieve maximum energy savings. We show that under SCF relaying large energy savings can be achieved by tolerating a controlled delay over the initiated service.

Load Balancing via Store-Carry and Forward Relaying in Cellular Networks

We bring to the fore a novel load balancing tech- nique based on delay tolerant message forwarding that relies on the store-carry and forward paradigm by utilizing the mobility of vehicular nodes in multi-cell wireless networks. Considerations are made not only on the achievable load balancing performance but also on the en route energy consumption. That accounts for the optimal trade-offs between load balancing, communication energy consumption and message delivery delay in the cellular network. A mathematical program is formulated for finding optimal forwarding decision policies for the proposed store-carry and forward (SCF) relaying scheme for load balancing. Furthermore, a low complexity on-line algorithm for the proposed network setup is derived and its performance is compared with the optimal solution. To sharpen the understanding of the proposed message forwarding techniques, a wide set of numerical investigations are presented revealing that by trading-off message delivery delays, the variance of the load across cells can be dramatically reduced.

ExTraCT: Expediting Offloading Transfers Through Intervehicle Communication Transmissions

Vehicular connectivity is considered as one of the most highly anticipated emerging technologies since it promises to transform the automotive sector and have a significant impact on all related markets. Data gathered (and information generated) within and around vehicles will be used to improve road safety, travelling efficiency, and passenger comfort and convenience. However, delivering such data to the infrastructure (to process information and generate intelligence) is a challenging task, mainly due to the very large volume of data traffic produced. A promising approach to support these communication needs is to deliver data traffic opportunistically through the available WiFi APs. Evidently, the intermittent connectivity of these hotspots and the inherent mobility of the vehicles severely limit the volume of traffic sent at any one instance in time. The latter limitation is studied in this paper, where decision policies are derived for vehicle-to-vehicle-assisted offloading to maximize the transmission opportunities and thus expedite data traffic delivery. As illustrated in this paper, these policies are easy to implement in practice and offer significant improvement in vehicular data traffic offloading as compared with opportunistic offloading and basic relaying practices.

Optimising file delivery in a maritime environment through inter-vessel connectivity predictions

It is well known that the Internet infrastructure is experiencing an ever growing demand for large file/data transfers. To date, Delay Tolerant Networking (DTN) seems as the only economically viable over-the-sea communications paradigm to support bulk data transfers between seagoing vessels and the fixed Internet. In this work, we construct an architectural prototype of this DTN overlay to connect sailing vessels to the fixed Internet infrastructure. The proposed architecture integrates elements of the existing vessel Automatic Identification System (AIS) to fetch and manipulate mobility and trip related data of every vessel that could come into close contact (at any future instance in time) with a destination node and therefore assist in message forwarding. Considering both current and future contact opportunities all within the same optimization strategy allows for the maximization of routing performance. Ultimately, it is shown that the proposed architecture allows for computationally efficient routing solutions to be generated with variable optimization objectives. As an initial assessment of the performance of the routing functions of this architecture we illustrate the optimal minimum delay routing paths that deliver messages from an arbitrary infrastructure node to a target destination mobile host.

A Practical Approach to Energy Efficient Communications in Mobile Wireless Networks

Energy efficiency and capacity maximization are two of the most challenging issues to be addressed by current and future cellular networks. Significant research effort has been placed recently in reducing the total energy consumption while maintaining or improving capacity either by introducing more efficient hardware components or by developing innovative software techniques. In this paper we investigate a novel networking paradigm to address the aforementioned problems. By capitalizing on the inherent delay tolerance of Internet type services, we argue that significant energy savings can be achieved by postponing the communication of information for a later time instance with better networking conditions. We device decentralized algorithms for the proposed postponement schemes and show the superior performance of implementing such schemes over the traditional cellular operation.

Data-Driven Event Triggering for IoT Applications

Event-triggering (ET) is an up-and-coming technological paradigm for monitoring, optimization, and control in the Internet of Things (IoT) that achieves improved levels of operational efficiency. This paper first defines the envisioned ET architecture for the IoT domain. It then classifies and reviews the various different ET approaches obtained from the available literature for the three phases of ET, namely behavior modeling, event detection, and event handling. Thereafter, a novel data-driven technique is developed to address all three phases of ET in an efficient and reliable manner. Finally, the applicability of the proposed data-driven technique is showcased in a real-world public transport scenario, demonstrating a substantial improvement in energy and spectrum efficiency compared to existing periodic techniques.

ProximAid: Proximal adhoc networking to aid emergency response

Mobile adhoc networking is considered as one of the key technologies to support communication when different emergencies or disasters strike. Unfortunately, the majority of existing adhoc networking solutions are based on proprietary hardware and software which severely limits their use by only those competent authorities that are well trained and properly equipped. As a consequence, patients/victims and bystanders are excluded from this communication network. This work details a novel adhoc networking solution that is purposefully designed to operate on consumer electronics such as smartphones, tablets and laptops that support the WiFi-Direct standard. The networking solution proposed is shown to be both highly scalable, robust and energy efficient due to the distributed and purely local operation of all its functionalities. The proposed solution is implemented and tested on Android devices and experimental results demonstrate its favourable features.