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Cognitive users (CUs) are allowed to access licensed bands without causing harmful interference to primary users (PUs). However, the quality of service (QoS) of CUs can not be guaranteed when CUs experience bad channel conditions in direct transmission between the cognitive source and its destination. In this paper, we consider the problem of cooperative transmission in cognitive radio networks. The...
Radio spectrum resource is a finite resource and of fundamental importance for wireless communication. But the utilization of the spectrum became unbalanced, some spectrum is crowd with users and some is inefficiently used. The concept of cognitive radio is a good solution for this problem. One of the tasks to realize this technology is to design an efficient MAC protocol. OSA-MAC is one of the practical...
Based on free probability theory, a new scheme for frequency band sensing of spreading communication system is proposed. Unlike previous studies in the field, the new scheme does not require the knowledge of the spreading sequences of users and is related to the asymptotic free behavior of random matrices. Simulation result shows that the convergence characteristic holds true even for a small number...
Spectrum sensing is a crucial technology for cognitive radio networks. In this paper, we develop a novel spectrum sensing method for secondary users to sense the idle spectrum. The key idea of the proposed method is combining multiple slots energy detection. Firstly, we establish the probability model regarding the appearance of the primary user at each slot of a secondary user slots window structure...
Cognitive networks enable efficient sharing of the radio spectrum. Multi-hop cognitive network is a cooperative network in which cognitive users take help of their neighbors to forward data to the destination. Control signals exchanged through a common control channel (CCC) to enable cooperation communication. But, using a common control channel introduces a new issue like channel saturation which...
In this paper, we consider underlay cognitive radio systems in which secondary users coexist with users in primary networks whose radio band is licensed. The secondary subnetwork comprising the cognitive users utilizes the cognitive radio technology to make opportunistic access to the licensed spectrum that primary users own. In this scheme, we discuss the issue of joint user scheduling and beamforming...
Spectrum sensing is an important component of cognitive radio technology. Cooperative spectrum sensing is regarded as the most promising method to improve the reliability of spectrum sensing. However, such cooperation also introduces overhead traffic of control signaling and result transmission which consumes more power in battery operated mobile terminals. In this paper, an RLECSS (run-length encoding...
The following topics are dealt with: wireless sensor networks; MIMO system; multi-hop wireless ad hoc networks; cooperative cognitive radio networks; OFDMA systems; congestion control scheme and network coding.
In this paper, sensing algorithms to select the available sub-bands in the cognitive UWB system are proposed; grouped time division sensing technique and decision methods for sub-channel selection. We employ energy detection method for spectrum sensing, which has low complexity in the wide spectrum sensing. Grouped time division sensing technique is proposed to transmit training symbols and to measure...
Conflict-free power allocation for secondary user (SU) in cognitive networks is a challenging problem since the accessible spectrum of the SU is shared with the primary user (PU); the problem becomes to be especially difficult when it is wanted to achieve the maximum network capacity considering the mutual interference between PU and SU. In this paper, specifying the single SU case with multiple PUs,...
We study the problem of revenue management in a cognitive spectrum underlay network, where the primary user chooses the bandwidth and tolerable interference levels for the secondary users. We show that the interference received by each secondary user is the same in a large system regime, and a simple pricing scheme achieves the efficient resource allocation at the market clearing equilibrium. We further...
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