Efficient Globally Optimal Resource Allocation in Wireless Interference Networks

Radio resource allocation in communication networks is essential to achieve optimal performance and resource utilization. In modern interference networks the corresponding optimization problems are often nonconvex and their solution requires significant computational resources. Hence, practical systems usually use algorithms with no or only weak optimality guarantees for complexity reasons. Nevertheless, asserting the quality of these methods requires the knowledge of the globally optimal solution. State-of-the-art global optimization approaches mostly employ Tuy's monotonic optimization framework which has some major drawbacks, especially when dealing with fractional objectives or complicated feasible sets. In this thesis, two novel global optimization frameworks are developed. The first is based on the successive incumbent transcending (SIT) scheme to avoid numerical problems with complicated feasible sets. It inherently differentiates between convex and nonconvex variables, preserving the low computational complexity in the number of convex variables without the need for cumbersome decomposition methods. It also treats fractional objectives directly without the need of Dinkelbach's algorithm. Benchmarks show that it is several orders of magnitude faster than state-of-the-art algorithms. The second optimization framework is named mixed monotonic programming (MMP) and generalizes monotonic optimization. At its core is a novel bounding mechanism accompanied by an efficient BB implementation that helps exploit partial monotonicity without requiring a reformulation in terms of difference of increasing (DI) functions. While this often leads to better bounds and faster convergence, the main benefit is its versatility. Numerical experiments show that MMP can outperform monotonic programming by a few orders of magnitude, both in run time and memory consumption. Both frameworks are applied to maximize throughput and energy efficiency (EE) in wireless interference networks. In the first application scenario, MMP is applied to evaluate the EE gain rate splitting might provide over point-to-point codes in Gaussian interference channels. In the second scenario, the SIT based algorithm is applied to study throughput and EE for multi-way relay channels with amplify-and-forward relaying. In both cases, rate splitting gains of up to 4.5% are observed, even though some limiting assumptions have been made

Resource Allocation for Energy-Efficient 3-Way Relay Channels

Throughput and energy efficiency in 3-way relay channels are studied in this paper. Unlike previous contributions, we consider a circular message exchange. First, an outer bound and achievable sum rate expressions for different relaying protocols are derived for 3-way relay channels. The sum capacity is characterized for certain SNR regimes. Next, leveraging the derived achievable sum rate expressions, cooperative and competitive maximization of the energy efficiency are considered. For the cooperative case, both low-complexity and globally optimal algorithms for joint power allocation at the users and at the relay are designed so as to maximize the system global energy efficiency. For the competitive case, a game theoretic approach is taken, and it is shown that the best response dynamics is guaranteed to converge to a Nash equilibrium. A power consumption model for mmWave board-to-board communications is developed, and numerical results are provided to corroborate and provide insight on the theoretical findings.Comment: Submitted to IEEE Transactions on Wireless Communication

Energy Efficiency in MIMO Underlay and Overlay Device-to-Device Communications and Cognitive Radio Systems

This paper addresses the problem of resource allocation for systems in which a primary and a secondary link share the available spectrum by an underlay or overlay approach. After observing that such a scenario models both cognitive radio and D2D communications, we formulate the problem as the maximization of the secondary energy efficiency subject to a minimum rate requirement for the primary user. This leads to challenging non-convex, fractional problems. In the underlay scenario, we obtain the global solution by means of a suitable reformulation. In the overlay scenario, two algorithms are proposed. The first one yields a resource allocation fulfilling the first-order optimality conditions of the resource allocation problem, by solving a sequence of easier fractional problems. The second one enjoys a weaker optimality claim, but an even lower computational complexity. Numerical results demonstrate the merits of the proposed algorithms both in terms of energy-efficient performance and complexity, also showing that the two proposed algorithms for the overlay scenario perform very similarly, despite the different complexity.Comment: to appear in IEEE Transactions on Signal Processin

Intelligent Reflecting Surface Operation under Predictable Receiver Mobility: A Continuous Time Propagation Model

The operation of an intelligent reflecting surface (IRS) under predictable receiver mobility is investigated. We develop a continuous time system model for multipath channels and discuss the optimal IRS configuration with respect to received power, Doppler spread, and delay spread. It is shown that the received power can be maximized without adding Doppler spread to the system. In a numerical case study, we show that an IRS having the size of just two large billboards can improve the link budget of ground to Low Earth Orbit (LEO) satellite links by up to 6 dB. It also adds a second, almost equivalently strong, communication path that improves the link reliability.Comment: 5 pages, 4 figure

Globally Optimal Spectrum- and Energy-Efficient Beamforming for Rate Splitting Multiple Access

Rate splitting multiple access (RSMA) is a promising non-orthogonal transmission strategy for next-generation wireless networks. It has been shown to outperform existing multiple access schemes in terms of spectral and energy efficiency when suboptimal beamforming schemes are employed. In this work, we fill the gap between suboptimal and truly optimal beamforming schemes and conclusively establish the superior spectral and energy efficiency of RSMA. To this end, we propose a successive incumbent transcending (SIT) branch and bound (BB) algorithm to find globally optimal beamforming solutions that maximize the weighted sum rate or energy efficiency of RSMA in Gaussian multiple-input single-output (MISO) broadcast channels. Numerical results show that RSMA exhibits an explicit globally optimal spectral and energy efficiency gain over conventional multi-user linear precoding (MU-LP) and power-domain non-orthogonal multiple access (NOMA). Compared to existing globally optimal beamforming algorithms for MU-LP, the proposed SIT BB not only improves the numerical stability but also achieves faster convergence. Moreover, for the first time, we show that the spectral/energy efficiency of RSMA achieved by suboptimal beamforming schemes (including weighted minimum mean squared error (WMMSE) and successive convex approximation) almost coincides with the corresponding globally optimal performance, making it a valid choice for performance comparisons. The globally optimal results provided in this work are imperative to the ongoing research on RSMA as they serve as benchmarks for existing suboptimal beamforming strategies and those to be developed in multi-antenna broadcast channels

Sisältöyhteistyö kaupallisen televisioviihteen rahoituskeinona

Tässä opinnäytetyössä selvitetään, miten kumppaniyritykset osallistuvat kaupallisen television viihdeohjelmien tuotannon rahoitukseen ja sisältöön sekä millainen vaikutus sisältöyhteistyöllä on suomalaiseen viihdetelevisiotuotantoon. Teoriaosuudessa perehdytään sisältöyhteistyön määritelmään ja sen eri muotoihin. Tässä opinnäytetyössä sisältöyhteistyöllä viitataan ensisijaisesti brändien esiintymiseen televisio-ohjelman sisällössä. Teoriaosuudessa kerrotaan brändisijoittelun kehityksen keskeiset virstanpylväät, minkä lisäksi syvennytään brändinäkyvyyden vaikutuksiin ja tavoitteisiin katsojien mielikuvissa. Tutkimusosaan haastateltiin yhteensä yhdeksää yrityksen, kaupallisen kanavan ja tuotantoyhtiön työntekijää, jotka ovat työskennelleet merkittävässä asemassa sisältöyhteistyön avulla rahoitetuissa viihdeohjelmakumppanuuksissa. Tutkimus toteutettiin Delfoi-menetelmällä, jossa jokainen henkilö vastaa samoihin kysymyksiin anonyymisti. Ensimmäisen kyselykierroksen vastauksien analyysin pohjalta toteutettiin uusi, kohdistetumpi kyselykierros samoille henkilöille. Tutkimustuloksien pohjalta voidaan todeta, että kumppaniyrityksillä on kasvava rooli viihdeohjelmien rahoituksessa. Vastuu sisällöstä pysyy kuitenkin sisällöntekijöillä, vaikka kumppanin rahoitus olisi tuotannon kannalta ratkaiseva. Kokonaan kumppanien rahoittamien ohjelmien määrä lähitulevaisuudessa tulee jäämään vähäiseksi. Tärkeimmät suomalaisen sisältöyhteistyön laadun kehitykseen vaikuttavat tekijät ovat tuotantoihin sijoitetun budjetin suuruus sekä hyväksi havaittujen toimintatapojen vakiintuminen eri osapuolien välillä.This Bachelor's thesis studies how partner companies participate in the funding and creative processes of commercial entertainment television shows in Finland and how their involvement affects the Finnish television entertainment industry. This type of collaboration is known as content partnership. The theoretical part of this thesis focuses on the definition of content partnership and its different forms. In this thesis, content partnership generally refers to a brand placement in television programs. In addition, the thesis examines the evolution of the brand placement in audiovisual content and explains the effects and objectives of the branded content. A total of nine professionals from different partner companies, commercial channels and production companies were interviewed for the research. The selected experts have had a significant role in past content partnership productions. The research was conducted following the Delphi method where each person answers a questionnaire anonymously. After analyzing the first-round answers, another more specific set of questions was presented for the experts. Based on the results, the importance of partner companies as a funding and creative partner for commercial entertainment television shows is growing. Content creators will still be in charge of the content itself even if the partner companies' funding is crucial to the program's existence. Programs that are completely funded through partnerships will stay minimal in the near future. The most important development points for the Finnish content partnerships are the size of the television show's budget and establishing solid working methods among the parties involved