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This thesis is an extension of a recent study into the relationship between merger size and profitability. It studies a class of Cournot oligopoly with linear cost and quadratic demand. Its focus is to analyze how a mergers profitability is affected by its size and by the demand elasticity. Such results have not yet been reported in previous studies, perhaps due to the complexity of the equilibrium equation involved. It shows an increase in the demand elasticity also raises a mergers profitability. Consequently, an increase in the demand elasticity reduces merged members critical combined per-merger market share for the merger to be profit enhancing. Comparing with 80% minimum market share requirement for a profitable merger in Salant, Switzer, and Reynolds (1983), a greater market share is needed when the demand function is concave (demand is relatively inelastic), while a smaller market share may still be profitable when the demand function is convex (demand is relatively elastic). In our model, mergers are generally detrimental to public interests by increasing market price and reducing output. However, the merger will be less harmful when the goods are very inelastic.

This thesis is an extension of a recent study into the relationship between merger size and profitability. It studies a class of Cournot oligopoly with linear cost and quadratic demand. Its focus is to analyze how a mergers profitability is affected by its size and by the demand elasticity. Such results have not yet been reported in previous studies, perhaps due to the complexity of the equilibrium equation involved. It shows an increase in the demand elasticity also raises a mergers profitability. Consequently, an increase in the demand elasticity reduces merged members critical combined per-merger market share for the merger to be profit enhancing. Comparing with 80% minimum market share requirement for a profitable merger in Salant, Switzer, and Reynolds (1983), a greater market share is needed when the demand function is concave (demand is relatively inelastic), while a smaller market share may still be profitable when the demand function is convex (demand is relatively elastic). In our model, mergers are generally detrimental to public interests by increasing market price and reducing output. However, the merger will be less harmful when the goods are very inelastic.

We consider a partial equilibrium Cournot-oligopolistic model in which the domestic market of two differentiated goods is served by a number of identical domestic firms and exports by foreign firms. In chapter 1, we characterize the optimality conditions with an emission standard and lump-sum tax to target the distortions, and we find the optimal instrument that targets the emission or pollution most efficiently. Through our study we find out that the use of right mix of environmental and non-environmental policy instruments could decrease emissions and increase welfare of the economy at the same time, even when there is foreign competition. Next, we introduce cross-border pollution and model pollution content tariff imposed on the imports from foreign country as one of the instruments for the domestic country in chapter 2. We first characterize the optimal values of the policy instruments and then design multilateral piecemeal policy reforms that unambiguously improve the welfare of the countries involved and reduce emissions. In chapter 3, we compare the effectiveness of two policy instruments in reducing pollution: subsidies tied to R&D and tariffs as trade barriers. Our paper shows that multilateral piecemeal policy reforms could be designed where 'carrots' in the form of tied subsidies to R&D would prove to be more beneficial than 'sticks' in the form of tariffs, in reducing the pollution and increasing the welfare for the two countries.

Abstract The aim of this thesis is to devise new paradigms on radio resource sharing including cache-enabled virtualized large cellular networks for mobile network operators (MNOs). Also, self-organizing resource allocation for small cell networks is considered. In such networks, the MNOs rent radio resources from the infrastructure provider (InP) to support their subscribers. In order to reduce the operational costs, while at the same time to significantly increase the usage of the existing network resources, it leads to a paradigm where the MNOs share their infrastructure, i.e., base stations (BSs), antennas, spectrum and edge cache among themselves. In this regard, we integrate the theoretical insights provided by stochastic geometrical approaches to model the spectrum and infrastructure sharing for large cellular networks. In the first part of the thesis, we study the non-orthogonal multi-MNO spectrum allocation problem for small cell networks with the goal of maximizing the overall network throughput, defined as the expected weighted sum rate of the MNOs. Each MNO is assumed to serve multiple small cell BSs (SBSs). We adopt the many-to-one stable matching game framework to tackle this problem. We also investigate the role of power allocation schemes for SBSs using Q-learning. In the second part, we model and analyze the infrastructure sharing system considering a single buyer MNO and multiple seller MNOs. The MNOs are assumed to operate over their own licensed spectrum bands while sharing BSs. We assume that multiple seller MNOs compete with each other to sell their infrastructure to a potential buyer MNO. The optimal strategy for the seller MNOs in terms of the fraction of infrastructure to be shared and the price of the infrastructure, is obtained by computing the equilibrium of a Cournot-Nash oligopoly game. Finally, we develop a game-theoretic framework to model and analyze a cache-enabled virtualized cellular networks where the network infrastructure, e.g., BSs and cache storage, owned by an InP, is rented and shared among multiple MNOs. We formulate a Stackelberg game model with the InP as the leader and the MNOs as the followers. The InP tries to maximize its profit by optimizing its infrastructure rental fee. The MNO aims to minimize the cost of infrastructure by minimizing the cache intensity under probabilistic delay constraint of the user (UE). Since the MNOs share their rented infrastructure, we apply a cooperative game concept, namely, the Shapley value, to divide the cost among the MNOs. / Tiivistelmä Tämän väitöskirjan tavoitteena on tuottaa uusia paradigmoja radioresurssien jakoon, mukaan lukien virtualisoidut välimuisti-kykenevät suuret matkapuhelinverkot matkapuhelinoperaattoreille. Näiden kaltaisissa verkoissa operaattorit vuokraavat radioresursseja infrastruktuuritoimittajalta (InP, infrastructure provider) asiakkaiden tarpeisiin. Toimintakulujen karsiminen ja samanaikainen olemassa olevien verkkoresurssien hyötykäytön huomattava kasvattaminen johtaa paradigmaan, jossa operaattorit jakavat infrastruktuurinsa keskenään. Tämän vuoksi työssä tutkitaan teoreettisia stokastiseen geometriaan perustuvia malleja spektrin ja infrastruktuurin jakamiseksi suurissa soluverkoissa. Työn ensimmäisessä osassa tutkitaan ei-ortogonaalista monioperaattori-allokaatioongelmaa pienissä soluverkoissa tavoitteena maksimoida verkon yleistä läpisyöttöä, joka määritellään operaattoreiden painotettuna summaläpisyötön odotusarvona. Jokaisen operaattorin oletetaan palvelevan useampaa piensolutukiasemaa (SBS, small cell base station). Työssä käytetään monelta yhdelle -vakaata sovituspeli-viitekehystä SBS:lle käyttäen Q-oppimista. Työn toisessa osassa mallinnetaan ja analysoidaan infrastruktuurin jakamista yhden ostaja-operaattorin ja monen myyjä-operaattorin tapauksessa. Operaattorien oletetaan toimivan omilla lisensoiduilla taajuuksillaan jakaen tukiasemat keskenään. Myyjän optimaalinen strategia infrastruktuurin myytävän osan suuruuden ja hinnan suhteen saavutetaan laskemalla Cournot-Nash -olipologipelin tasapainotila. Lopuksi, työssä kehitetään peli-teoreettinen viitekehys virtualisoitujen välimuistikykenevien soluverkkojen mallintamiseen ja analysointiin, missä InP:n omistama verkkoinfrastruktuuri vuokrataan ja jaetaan monen operaattorin kesken. Työssä muodostetaan Stackelberg-pelimalli, jossa InP toimii johtajana ja operaattorit seuraajina. InP pyrkii maksimoimaan voittonsa optimoimalla infrastruktuurin vuokrahintaa. Operaattori pyrkii minimoimaan infrastruktuurin hinnan minimoimalla välimuistin tiheyttä satunnaisen käyttäjän viive-ehtojen mukaisesti. Koska operaattorit jakavat vuokratun infrastruktuurin, työssä käytetään yhteistyöpeli-ajatusta, nimellisesti, Shapleyn arvoa, jakamaan kustannuksia operaatoreiden kesken.