Modeling and Analysis of a Relay-Assisted Cooperative Cognitive Network
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We investigate a novel queueing system that can be used to model relay-assisted cooperative cognitive networks with coupled relay nodes. Consider a network of two saturated source users that transmit packets towards a common destination node under the cooperation of two relay nodes. The destination node forwards packets outside the network, and each source user forwards its blocked packets to a dedicated relay node. Moreover, when the transmission of a packet outside the network fails, either due to path-loss, fading or due to a hardware/software fault in the transmitter of the destination node, the failed packet is forwarded to a relay node according to a probabilistic policy. In the latter case a recovery period is necessary for the destination node in order to return in an operating mode. Relay nodes have infinite capacity buffers, and are responsible for the retransmission of the blocked/failed packets. Relay nodes have cognitive radio capabilities, and there are fully aware about the state of the other. Taking also into account the wireless interference, a relay node adjusts its retransmission parameters based on the knowledge of the state of the other. We consider a three-dimensional Markov process, investigate its stability, and study its steady-state performance using the theory of boundary value problems. Closed form expressions for the expected delay are also obtained in the symmetrical model.
KeywordsCooperative network Cognitive users Boundary value problem Stability conditions Performance
The author is grateful to the PC chairs and the anonymous referees for the valuable remarks, from which the presentation of the paper has benefited. He would also like to thank Dr. N. Pappas (Linköping University, Sweden), and Dr. T. Phung-Duc (University of Tsukuba, Japan) for their valuable comments.