Now showing items 1-11 of 11

    • Çok kullanıcılı çok antenli sistemlerde iş birlikli iletim 

      Yazarel, Y. K.; Aktaş, Defne (IEEE, 2008-04)
      Bu çalışmada işbirlikli, çok kullanıcılı, ve çok antenli bir haberleşme sisteminde telsiz erişim terminallerinin en iyi veri iletimi tekniğine ortaklaşa karar vermeleri problemini inceliyoruz. Burada pek çok çalışmadan ...
    • Dikgen frekans bölmeli çoklu erişim sistemlerinde telsiz erişim terminallerinin işbirliği 

      Tokel, Turgut Barış; Aktaş, Defne (IEEE, 2009-04)
      Gelecek nesil kablosuz iletişim sistemlerinde öngörülen veri hızlarına ulaşabilmek için bu sistemlerde frekans yeniden kullanım oranının 1 olmasına ihtiyaç¸ vardır, bu ise özellikle hücre sınırlarındaki kullanıcıların ...
    • Downlink beamforming under individual SINR and per antenna power constraints 

      Yazarel, Y. K.; Aktaş, Defne (IEEE, 2007-08)
      In this paper we consider the problem of finding the optimum beamforming vectors for the downlink of a multiuser system, where there are individual signal to interference plus noise ratio (SINR) targets for each user. ...
    • Investigation of planar and conformal printed arrays for MIMO performance analysis 

      Tunç, Celal Alp; Ircı, Erdinç; Bakır, Onur; Aktaş, Defne; Ertürk, Vakur B.; Altıntaş, Ayhan (IEEE, 2006)
      MIMO channel capacity of printed arrays with dipole elements is analyzed. A MIMO channel model based on electric fields is used. The effects of mutual interactions among the array elements through space and surface waves ...
    • A model with electric fields for the inclusion of mutual coupling effects in the MIMO channel 

      Tunç, Celal Alp; Ircı, Erdinç; Bakır, Onur; Aktaş, Defne; Ertürk, Vakur B.; Altıntaş, Ayhan (IEEE, 2007)
      Multiple input multiple output (MIMO) wireless communication systems have been a focus of interest, due to their ability to increase the capacity in rich scattering environments by using multi-element antenna arrays both ...
    • On capacity and coding for segmented deletion channels 

      Wang, F.; Aktaş, Defne; Duman, T. M. (IEEE, 2011)
      We consider binary deletion channels with a segmentation assumption which appears to be suited for more practical scenarios. Unlike the binary independent and identically distributed (i.i.d.) deletion channel where each ...
    • On the number of clusters in channel model 

      Akkaya, Keziban; Tunç, Celal Alp; Aktaş, Defne; Altıntaş, Ayhan (IEEE, 2006-08)
      Typically, scatterers in an environment are not distributed uniformly but rather observed to occur in clusters. Identification of clusters is an issue under discussion. To this end, we study the effect of number of clusters ...
    • Optimization of linear wire antenna arrays to increase MIMO capacity using swarm intelligence 

      Olgun, Uğur; Tunç, Celal Alp; Aktaş, Defne; Ertürk, Vakur B.; Altıntaş, Ayhan (Institution of Engineering and Technology, 2007)
      Free standing linear arrays (FSLA) are analyzed and optimized to increase MIMO capacity. A MIMO channel model based on electric fields is used. The effects of mutual interactions among the array elements are included into ...
    • Particle swarm optimization for SAGE maximization step in channel parameter estimation 

      Bodur, Harun; Tunç, Celal Alp; Aktaş, Defne; Ertürk, Vakur .B.; Altıntaş, Ayhan (IET, 2007-11)
      This paper presents an application of particle swarm optimization (PSO) in space alternating generalized expectation maximization (SAGE) algorithm. SAGE algorithm is a powerful tool for estimating channel parameters like ...
    • Transmit beamforming with cooperative base stations 

      Ng, B. L.; Evans, J. S.; Hanly, S. V.; Aktaş, Defne (IEEE, 2005-09)
      We consider a cellular network where base stations can cooperate to determine the signals to be transmitted on the downlink. In such a scenario, it would be possible to use "macroscopic" transmit beamforming to improve ...
    • Turbo base stations 

      Aktaş, E.; Aktaş, Defne; Hanly, S.; Evans, J. (Cambridge University Press, 2011)
      Cellular communication systems provide wireless coverage to mobile users across potentially large geographical areas, where base stations (BSs) provide service to users as interfaces to the public telephone network. Cellular ...