Abstract-In this paper we develop a framework for competition of future operators likely to operate in a mixed commons/property-rights regime under the regulation of a spectrum policy server (SPS). The operators dynamically compete for customers as well as portions of available spectrum. The operators are charged by the SPS for the amount of bandwidth they use in their services. Through demand responsive pricing, the operators try to come up with convincing service offers for the customers, while trying to maximize their profits. We first consider a single-user system as an illustrative example. We formulate the competition between the operators as a noncooperative game and propose an SPS-based iterative bidding scheme that results in a Nash equilibrium of the game. Numerical results suggest that, competition increases the user's (customer's) acceptance probability of the offered service, while reducing the profits achieved by the operators. It is also observed that as the cost of unit bandwidth increases relative to the cost of unit infrastructure (fixed cost), the operator with superior technology (higher fixed cost) becomes more competitive. We then extend the framework to a multiuser setting where the operators are competing for a number of users at once. We propose an SPSbased bandwidth allocation scheme in which the SPS optimally allocates bandwidth portions for each user-operator session to maximize its overall expected revenue resulting from the operator payments. Comparison of the performance of this scheme to one in which the bandwidth is equally shared between the useroperator pairs reveals that such an SPS-based scheme improves the user acceptance probabilities and the bandwidth utilization in multiuser systems.

The assumption that all nodes cooperate to relay packets for each other may not be realistic for commercial wireless ad hoc networks. An autonomous (selfish) node in a wireless network has two disincentives for forwarding for others: energy expenditure (real cost) and possible delays for its own data (opportunity cost). We introduce a mechanism that "fosters cooperation through bribery" in the context of forwarding in ad hoc networks. Using a microeconomic framework based on game theory, we design and analyze a pricing algorithm that encourages forwarding among autonomous nodes by reimbursing forwarding. Taking a joint network-centric and user-centric approach, the revenue maximizing network and utility (measured in bits-per-Joule) maximizing nodes interact through prices for channel use, reimbursements for forwarding, transmitter power control, as well as forwarding and destination preferences. In a three-node (two-sources, one-access-point) network, the network converges to an architecture that induces forwarding only when the network geometries are such that forwarding is likely to increase individual benefits (network revenue and node utilities). For other geometries, the network converges to architectures that do not favor forwarding. We then generalize to a multinode network, where it is seen that the nodes' willingness to forward decrease for large ratios of the average internodal distance to the smallest distance between the access point and any source node. Pricing with reimbursement generally improves the network aggregate utility (or aggregate bits-per-Joule), as well as utilities and revenue compared with the corresponding pricing algorithm without reimbursement.

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Abstract-Relay cooperation has been recognized as an important mechanism to enhance connectivity and throughput in multi-hop wireless networks, especially under varying channel conditions. One major problem of relay cooperation is that relaying always incurs energy and possibly delay costs. To a rational and selfish node these costs are worth incurring only if it receives at least comparable returns in the long term. In light of this, we propose a new incentive mechanism called bandwidth exchange (BE) where a node can delegate a portion of its bandwidth to another node in exchange for relay cooperation. In this paper we specifically study BE in the simple form of exchanging orthogonal frequency bands to provide incentives for relaying in a wireless network. Other forms of exchanging bandwidth such as delegation of time-slots or using spreading codes of different lengths are also possible. Using a Nash Bargaining framework, we explore the advantage of BE in both static and fading channels.

Abstract-In this paper we develop a framework for operator competition based on short term ownership of spectrum resources and devise a dynamic spectrum access method called "Dynamic Property Rights Spectrum Access (D-Pass)". In the D-Pass model, spectrum portions are allocated to operators on a short term basis (few sessions) by a SPS (Spectrum Policy Server) that serves as a controller/enforcer as well as a clearinghouse for spectrum allocations. Prior to each short term allocation, the SPS optimally determines a specific partition of spectrum resources among the operators to maximize a system related objective function. The operators are charged by the SPS for the amount of spectrum they are allocated. Given the spectrum allocation, the operators compete with each other for users present in the system through demand responsive pricing, in the form of an iterative bidding scheme reminiscent of simultaneous ascending auctions. At every iteration, the operators make rate and price offers for each user considering the bandwidth allocated to them and their costs associated with serving the users. The users respond by declaring the probabilities with which they will accept the service offers made. We consider two different objective functions for the SPS to maximize while determining the exact partition of the spectrum resources: (1) the total expected bandwidth utilization, (2) the minimum acceptance probability that a user accepts the offered service. We demonstrate several tradeoffs between these objectives through numerical experiments and illustrate the effect of bandwidth cost on these tradeoffs. Our results also suggest that employing short term allocation of resources could potentially lead to performance gains as opposed to static allocation of resources, especially in regimes where the bandwidth is relatively expensive.

OzetçeAlışveriş merkezi, havaalanı gibi binaiçi ortamlarda konumtabanlı servislere olan ihtiyaç giderek artmaktadır. Bu tür servisleri desteklemek için konum kestirim metodları gerekmektedir. Bu çalışmada, binaiçi ortamlarda mobil kullanıcının konumunu tespit etmek için alınan sinyal gücü (RSS) tabanlı RF parmakizi yöntemine dayalı K-Nearest Neighbor (K-NN) ve random decision forest (rastgele karar ormanı, RKO) iki algoritma sunulmuştur. Bu algoritmaların başarımlarını gerçek binaiçi ortamlarda elde etmek ve karşılaştırmak için Istanbul Ataşehir'deki Palladium alışveriş merkezinde GSM ag altyapısı kullanılarakölçümler yapılmıştır. Toplanılan GSM alınan sinyal gücü verileri kullanılarak her iki algoritma için CDF konum kestirim hata sonuçları elde edilmiştir. Yine, buölçüm verileri kullanılarak farklı iki telefon modeli olan Sony Ericsson ve Nokia telefonlarının konum kestirim hatasıüzerindeki etkileri araştırılmıştır. Elde edilen sonuçlara göre RKO algoritması K-NN algoritmasından az da olsa daha iyi başarım saglamıştır. Ayrıca, Sony Ericsson telefon modeli Nokia telefon modelinden daha iyi konum tespit başarımı göstermiştir. Abstract The demand for location-based services (LBS) in indoor environments such as shopping malls and airports has increasedrecently. In order to support such LBS applications accurate indoor localization systems are required. Therefore, in this paper, K-Nearest Neighbor (K-NN) and Random Decision Forest (RDF) algorithms for GSM RSS based RF fingerprinting method are presented in order find the location of mobile users in indoor environments. For studying the performance of these two algoritms in realistic indoor environments, a measurement campaign is conducted in Istanbul Ataşehir Palladium shopping mall using GSM cellular networks. The location estimation error performance of these two algoritms are obtained in the form of CDF results by using the collected GSM RSS data. Moreover, the effects of different mobile phone brands (Sony Ericsson and Nokia) on the location estimation error performance are investigated using the measurement data. According to the results, RDF method performs slightly better than K-NN method. Additionally, Sony Ericsson mobile phone provides better location estimation performance than that of Nokia mobile phone.

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