| 1. |
- Angelakis, Vangelis, et al.
(author)
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A distributed, load-aware, power and frequency bargaining protocol for LTE-based networks
- 2012
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In: 2012 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC). - Piscataway, NJ, USA : IEEE. - 9781457720529 - 9781457720512 ; , s. 6525-6529
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Conference paper (peer-reviewed)abstract
- A distributed, load-aware, joint power and frequency allocation protocol is introduced for LTE-based cellular networks, and system-level simulations are performed. Our proposed scheme aims to cooperatively limit the impact of Fractional Frequency Reuse (FFR) on the center users throughput compared to the Reuse 1 scheme, while providing sufficient throughput for the edge users. This is achieved through an asynchronous, lightweight scheme of local message exchange between neighboring LTE eNodeBs. The proposed scheme facilitates a type of "bargain" where an overloaded sector requests permission to utilize its neighbors edge bands for its center users at a limited set of transmit power levels. Grants are generated at each neighbor by solving a small-scale optimization problem. Using an LTE simulator we evaluate our scheme on a network with 21 sectors of varying load patterns. The proposed schemes performance for center users is consistently improved with respect to FFR-3, while for edge users the performance degradation is controlled by a parameter we set in the optimization problems definitions; compared to Reuse 1 edge users still have gains. Specifically, we observed up to a 46% gain in the sectors center throughput with a cost below 9% at the edges when compared to the classic FFR scheme, while the overall system throughput goes up by up to 26% in heavily loaded scenarios.
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| 2. |
- Angelakis, Vangelis, 1977-, et al.
(author)
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A Fully Decentralized and Load-Adaptive Fractional Frequency Reuse Scheme
- 2011
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In: Modeling, Analysis & Simulation of Computer and Telecommunication Systems (MASCOTS), 2011 IEEE 19th International Symposium on. - 9781457704680 ; , s. 425-428
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Conference paper (peer-reviewed)abstract
- A new fully decentralized dynamic fractional frequency reuse (FFR)-based scheme for cellular OFDMA networks is introduced. FFR is a technique to mitigate inter-cell interference to improve the throughput of interference-limited users on the cell edge, to the expense of the rest of the cell's users and the aggregate throughput. The proposed scheme aims to limit the FFR-incurred loss of the center users' throughput, while still providing sufficient bandwidth for the cell edge users' communication. This is done by local information sharing and distributed optimization. The resulting flexibility of frequency reuse can be especially beneficial in scenarios with non-uniform and time-varying load. The optimization task is accomplished by solving a knapsack problem in each cell, where the goal is to maximize the center throughput while maintaining acceptable degradation on the cell edge with respect to the original FFR allocation. The performance improvement resulting from the distributed and dynamic FFR scheme is demonstrated by snapshot simulations on an 81-cells network with asymmetric cell load. The proposed scheme achieves up to a 62% gain in cell-center throughput with a cost of no more than 18% at the edges when compared to the classic FFR scheme. The overall system throughput improvement ranges from 22% to 58%.
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| 3. |
- Angelakis, Vangelis, et al.
(author)
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Adjacent Channel Interference in 802.11a Is Harmful: Testbed Validation of a Simple Quantification Model
- 2011
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In: IEEE COMMUNICATIONS MAGAZINE. - : IEEE Institute of Electrical and Electronics. - 0163-6804. ; 49:3, s. 160-166
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Journal article (peer-reviewed)abstract
- Wireless LAN radio interfaces based on the IEEE 802.11a standard have lately found widespread use in many wireless applications. A key reason for this was that although the predecessor, IEEE 802.11b/ g, had a poor channelization scheme, which resulted in strangling adjacent channel interference (ACI), 802.11a was widely believed to be ACI-free due to a better channelization combined with OFDM transmission. We show that this is not the case. ACI does exist in 802.11a, and we can quantify its magnitude and predict its results. For this, we present minor modifications of a simple model originally introduced by [1] that allow us to calculate bounding values of the 802.11a ACI, which can be used in link budget calculations. Using a laboratory testbed, we verify the estimations of the model, performing experiments designed to isolate the affected 802.11 mechanisms. This isolation was enabled by not using the wireless medium, and emulating it over cables and attenuators. Our results show clear throughput degradation because of ACI in 802.11a, the magnitude of which depends on the interfering data rates, packet sizes, and utilization of the medium.
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| 4. |
- Angelakis, Vangelis, et al.
(author)
-
Allocation of Heterogeneous Resources of an IoT Device to Flexible Services
- 2016
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In: IEEE Internet of Things Journal. - : Institute of Electrical and Electronics Engineers (IEEE). - 2327-4662. ; 3:5, s. 691-700
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Journal article (peer-reviewed)abstract
- Internet-of-Things (IoT) devices can be equipped with multiple heterogeneous network interfaces. An overwhelmingly large amount of services may demand some or all of these interfaces available resources. Herein, we present a precise mathematical formulation of assigning services to interfaces with heterogeneous resources in one or more rounds. For reasonable instance sizes, the presented formulation produces optimal solutions for this computationally hard problem. We prove the NP-completeness of the problem and develop two algorithms to approximate the optimal solution for big instance sizes. The first algorithm allocates the most demanding service requirements first, considering the average cost of interfaces resources. The second one calculates the demanding resource shares and allocates the most demanding of them first by choosing randomly among equally demanding shares. Finally, we provide simulation results giving insight into services splitting over different interfaces for both cases.
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| 5. |
- Angelakis, Vangelis, et al.
(author)
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BBTM: New life for old ATM
- 2016
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In: 2016 IEEE/AIAA 35TH DIGITAL AVIONICS SYSTEMS CONFERENCE (DASC). - : IEEE. - 9781509025237
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Conference paper (peer-reviewed)abstract
- This paper investigates algorithmic questions related to the possibility of managing UAV traffic with beacon-based navigation, which we dub BBTM - Beacon-Based Traffic Management. The specific problem addressed is: How to install the minimum number of beacons in a mountainous terrain to ensure connectivity among a given set of UAS terminals on the terrain? BBTM is relevant for low-cost UAVs operating in remote areas not on time-critical missions, and may also be used as a backup system for better-equipped UAS in case the precise positioning or control information is lost, spoofed or jammed. We give algorithms for the beacon tower placement and evaluate their performance both on synthetic and real-world terrain data; the experiments suggest that our solutions can be used to efficiently quantify costs of establishing direct-visibility routing networks for UAS management.
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| 6. |
- Angelakis, Vangelis, et al.
(author)
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Flexible allocation of heterogeneous resources to services on an IoT device
- 2015
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In: 2015 IEEE Conference on Computer Communications Workshops (INFOCOM WKSHPS). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781467371315 ; , s. 99-100
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Conference paper (peer-reviewed)abstract
- In the Internet of Things (IoT), devices and gateways may be equipped with multiple, heterogeneous network interfaces which should be utilized by a large number of services. In this work, we model the problem of assigning services' resource demands to a device's heterogeneous interfaces and give a Mixed Integer Linear Program (MILP) formulation for it. For meaningful instance sizes the MILP model gives optimal solutions to the presented computationally-hard problem. We provide insightful results discussing the properties of the results on the properties of the derived solutions with respect to the splitting of services to different interfaces.
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| 7. |
- Angelakis, Vangelis, et al.
(author)
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Minimum-Time Link Scheduling for Emptying Wireless Systems: Solution Characterization and Algorithmic Framework
- 2014
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In: IEEE Transactions on Information Theory. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9448 .- 1557-9654. ; 60:2, s. 1083-1100
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Journal article (peer-reviewed)abstract
- We consider a set of transmitter-receiver pairs, or links, that share a wireless medium and address the problem of emptying backlogged queues with given initial size at the transmitters in minimum time. The problem amounts to determining activation subsets of links, and their time durations, to form a minimum-time schedule. Scheduling in wireless networks has been studied under various formulations before. In this paper, we present fundamental insights and solution characterizations that include: 1) showing that the complexity of the problem remains high for any continuous and increasing rate function; 2) formulating and proving sufficient and necessary optimality conditions of two baseline scheduling strategies that correspond to emptying the queues using one-at-a-time or all-at-once strategies; and 3) presenting and proving the tractability of the special case in which the transmission rates are functions only of the cardinality of the link activation sets. These results are independent of physical-layer system specifications and are valid for any form of rate function. We then develop an algorithmic framework for the solution to this problem. The framework encompasses exact as well as sub-optimal, but fast, scheduling algorithms, all under a unified principle design. Through computational experiments, we finally investigate the performance of several specific algorithms from this framework.
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| 8. |
- Angelakis, Vangelis, et al.
(author)
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Mobility modeling for transport efficiency : Analysis of travel characteristics based on mobile phone data
- 2013
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In: Netmob 2013.
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Conference paper (peer-reviewed)abstract
- Signaling data from the cellular networks can provide a means of analyzing the efficiency of a deployed transportation system and assisting in the formulation of transport models to predict its future use. An approach based on this type of data can be especially appealing for transportation systems that need massive expansions, since it has the added benefit that no specialized equipment or installations are required, hence it can be very cost efficient.Within this context in this paper we describe how such obtained data can be processed and used in order to act as enablers for traditional transportation analysis models. We outline a layered, modular architectural framework that encompasses the entire process and present results from initial analysis of mobile phone call data in the context of mobility, transport and transport infrastructure. We finally introduce the Mobility Analytics Platform, developed by Ericsson Research, tailored for mobility analysis, and discuss techniques for analyzing transport supply and demand, and give indication on how cell phone use data can be used directly to analyze the status and use of the current transport infrastructure.
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| 9. |
- Angelakis, Vangelis, et al.
(author)
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On Emptying a Wireless Network in Minimum Time
- 2012
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In: 2012 IEEE International Symposium on Information Theory Proceedings (ISIT). - Piscataway, NJ, USA : IEEE. - 9781467325806 - 9781467325783 ; , s. 2671-2675
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Conference paper (peer-reviewed)abstract
- We consider N transmitter-receiver pairs that share a wireless channel and we address the problem of obtaining a schedule for activating subsets of these links so as to empty the transmitter queues in minimum time. Our aim is to provide theoretical insights for the optimality characterization of the problem, using both a cross-layer model formulation, which takes into account the effect of interference on achievable transmission rates, as well as a collision-based model, which does not incorporate the physical layer realities into the problem. We present the basic linear programming formulation of the problem and establish that the optimal schedule need not consist of more than N subset activation frames. We then prove that the problem is NP-hard for all reasonable continuous rate functions. Finally, we obtain sufficient and/or necessary conditions for optimality in a number of special cases.
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| 10. |
- Angelakis, Vangelis, et al.
(author)
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Optimal and Collaborative Rate Selection for Interference Cancellation in Wireless Networks
- 2011
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In: IEEE Communications Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1089-7798 .- 1558-2558. ; 15:8, s. 819-821
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Journal article (peer-reviewed)abstract
- Analysis of wireless systems commonly assumes single-user detection at the receivers. Interference is typically treated as noise. On the other hand, multiuser detection has long been taking advantage of interference cancellation (IC) to increase capacity. We exploit IC by optimal rate selection. Transmission rates are collaboratively optimized to maximize the benefit of IC. A link reduces its rate, if that enables IC to significantly boost the SINR on other links. We provide a complexity analysis and an integer programming model to find the optimal IC pattern. Simulation results indicate that throughput improvement is over 30% in low SINR regimes.
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