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2013 - 20142
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Yazar: Edemen, Çağatay × Konu: Cooperative communication ×

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  • Küçük Resim
    Yayın
    Cognitive cooperative MAC with one primary and two secondary users: achievable rates and optimal power control
    (IEEE-INST Electrical Electronics Engineers Inc, 2014-11) Edemen, Çağatay; Kaya, Onur
    We consider a three-user fading cognitive cooperative multiple access channel (MAC) with one primary and two secondary transmitters. We propose two encoding/decoding strategies with varying levels of cooperation, based on block Markov superposition encoding and backward decoding. The first is an overlay model, where the secondary users (SUs) aid the transmission of the primary user (PU) by causally decoding the PU message and forwarding it while also cooperating among each other. The second is an underlay model, where the SUs cooperate by decoding and forwarding each other's messages while treating the signal received from the PU as noise. In either case, the PU is guaranteed to operate at its maximum achievable single user rate. We characterize the achievable SU rate region for both models and maximize this region as a function of the transmit powers. The simulation results show that the SU rate region can be significantly enlarged, particularly using the overlay model.
  • Küçük Resim
    Yayın
    A new block Markov coding strategy for pairwise and collective cooperation in the three user MAC
    (IEEE, 2013) Edemen, Çağatay; Kaya, Onur
    For a three user cooperative multiple access channel (MAC), we propose a new block Markov superposition encoding strategy, which enables all three users to cooperate collectively as well as in pairs. We obtain the resulting achievable rate expressions and compare them with existing two and three user cooperative strategies. We demonstrate that significant rate gains may be possible, without resorting to adaptive encoding/decoding techniques. We investigate the contributions from pairwise and collective cooperation signals while achieving tuples on the rate region boundary, and compare by simulations the sum rates achievable by two user versus three user grouping in cooperative MACs with fixed total resources.