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Yayın Cooperative strategies and achievable rates for two user OFDMA channels(IEEE-INST Electrical Electronics Engineers Inc, 2011-12) Bakım, İsmail Sezi; Kaya, OnurWe propose three encoding strategies for a two user cooperative Orthogonal Frequency Division Multiple Access (OFDMA) system, based on block Markov superposition encoding (BMSE). We obtain the expressions for the resulting achievable rate regions for all three encoding strategies. We show that, by allowing for re-partitioning and re-encoding of the cooperative messages across subchannels, it is possible to better exploit the diversity created by OFDMA, and higher rates can be achieved. We demonstrate potential rate gains attained by cooperative OFDMA, through simulations.Yayın Joint space time block code and modulation classification for MIMO systems(Institute of Electrical and Electronics Engineers Inc, 2017-02) Bayer, Özgür; Öner, Mustafa MengüçNon-cooperative identification of unknown communication signals is a popular research area with widespread civilian and military applications. Multiple input multiple output (MIMO) systems employing multi-antenna transmission pose new challenges to signal identification systems, such as the classification of the employed space time block code (STBC) and modulation in the presence of the self-interference inherent to the multi-antenna transmission. In the existing literature, these two classification problems have been handled separately, despite the fact that they are interrelated. This letter presents a novel approach to MIMO signal identification by considering the modulation type and the STBC classification tasks as a joint classification problem.Yayın Design and performance analysis of a novel trellis coded space-time-frequency OFDM transmission scheme(Wiley-Blackwell, 2008-01) Oğuz, Onur; Aygölü, Hasan Ümit; Panayırcı, ErdalIn this paper a new transmit diversity technique is proposed for wireless communications over frequency selective fading channels. The proposed technique utilises orthogonal frequency division multiplexing (OFDM) to transform a frequency selective fading channel into multiple flat fading subchannels on which first space-frequency coding and then additional space-time coding are applied resulting in a space-time-frequency OFDM (STF-OFDM) scheme. This scheme provides a quasi-orthogonal 4 x 4 transmission matrix but relax the constraint on channel fading parameters to be constant over four time or frequency slots into two time and two frequency slots. The pairwise error probability of the new scheme is evaluated and new code design criteria are obtained to improve the error performance. 64-, 128- and 256-state 4-PSK trellis codes for STF transmission scheme are generated based on these criteria and their frame error performances in an OFDM system are evaluated by computer simulations.
