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Yayın Maximum likelihood blind channel estimation for space-time coding systems(Hindawi Publishing Corporation, 2002-05) Çırpan, Hakan Ali; Panayırcı, Erdal; Çekli, ErdinçSophisticated signal processing techniques have to be developed for capacity enhancement of future wireless communication systems, In recent years, space-time coding is proposed to provide significant capacity gains over the traditional communication systems in fading wireless channels. Space-time codes are obtained by combining channel coding, modulation, transmit diversity, and optional receive diversity in order to provide diversity at the receiver and coding gain without sacrificing the bandwidth. In this paper, we consider the problem of blind estimation of space-time coded signals along with the channel parameters. Both conditional and unconditional maximum likelihood approaches are developed and iterative solutions are proposed. The conditional maximum likelihood algorithm is based on iterative least squares with projection whereas the unconditional maximum likelihood approach is developed by means of finite state Markov process modelling. The performance analysis issues of the proposed methods are studied. Finally, some simulation results are presented.Yayın A role-based service level NFC ecosystem model(Springer, 2013-02) Ok, Kerem; Coşkun, Vedat; Özdenizci Köse, Büşra; Aydın, Mehmet NafizNear Field Communication (NFC) is a short range wireless communication technology allowing to communicate mobile devices within close proximity. It provides opportunity for service providers to offer various value added services to customers. NFC technology allows the usage of wide range of applications and eliminates the obligation to carry additional components other than the mobile device such as credit or payment cards, tickets, identification cards or keys. Despite its technological advantages over alternative ones, the NFC business ecosystems and services are yet to take off. The problems mainly arise with the business issues triggered by different and mostly conflicting needs of many actors in the ecosystem and several additional technical issues. In this study, by adopting a role-based service ecosystem modeling, we propose an NFC ecosystem model which perfectly specifies the roles in the ecosystem, and defines set of activities for each role, and communication structure. We analyzed NFC ecosystem in three phases as pre-installation, installation, and service usage. We have defined the activities and communication structure in the first two phases, and finally investigated the service usage phase in three different operating modes of NFC. After giving the details of the proposed ecosystem model, two use cases are given to validate the developed ecosystem model. We complete our study by discussing the requirement satisfaction.
