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This paper investigates joint relay selection (RS) and power allocation (PA) in cognitive radio (CR) systems, in which relay nodes operate in amplify-and-forward (AF) mode. In contrast to the conventional schemes, we take into account the performance of the secondary user (SU) which acts as the relay. A two-step optimization scheme is proposed to maximize system throughput with minimum rate guarantees...
In this paper, we consider the problem of hierarchical bandwidth sharing in cognitive radio (CR) environment. In the system model under consideration, a primary service provider (PSP) can sell its available spectrum bandwidth to a secondary service provider (SSP). In contrast to the conventional schemes, the SUs served by the SSP can also share the unsold bands of the PSP through the approach of opportunistic...
Cognitive radio (CR) is a typical technology to allow secondary users use the licensed spectrum resource dynamically. Spectrum sensing is one of the important technics in CR. In this paper, optimal threshold for dual-stage spectrum sensing is researched. Two-threshold energy detection (ED) and one-threshold cyclostationary feature detection (CFD) are chosen as the coarse sensing technique and the...
In this paper, we consider the problem of joint relay selection and power allocation in a cognitive radio (CR) network, where a secondary user (SU) source communicates with a secondary access point (AP) assisted by a set of SU relays. Each SU in this set not only acts as a potential relay but also has its own data transmission requirement. Keeping the interference to the primary user (PU) below a...
Spectrum handover becomes one of the hot topics of Cognitive Radio recently. Spectrum handover happens when the primary users and secondary users collide on the same spectrum hole, and the secondary users need to switch to other spectrum holes to continue the communication. Therefore, the reliability of spectrum Q-learning handover, which is reflected by the quality of service of secondary users and...
Cognitive radio is used to improve spectrum utilization. Many theoretical achievements have been proposed in spectrum sensing, spectrum access, spectrum handover and so on. Hardware platforms have also been put forward. However, the traditional hardware device which is based on embedded system has the disadvantages of narrow band coverage and inflexibility. In this paper, we design and implement a...
Cognitive radio is the approach to increase the spectrum utilization for wireless applications. Control channel design is essential to improve the performance of the cognitive radio network. The control channel design scheme of Multi-channel Time domain Identification Rendezvous (MTIR) is proposed which adopts different signal patterns to abate the dependence on network-wide synchronized clock for...
As one of the hot topics in Cognitive Radio, the secondary user's capacity has been paid lots of attentions. The interference incurring in cognitive environment hides more information than current researches have discovered. This paper studies the process that individual primary users and secondary users interfering each other, based on which the capacity of each secondary user on every spectrum hole...
Channel reservation is used to decrease the drop ratio of secondary users caused by spectrum handover. This paper considers the maintainer of the reserved channels in one secondary system coexisting with multiple primary systems. The global channel reservation scheme, the user channel reservation scheme, and the user-updated channel reservation scheme are proposed, derived by different Markov models...
The frequency resource of mobile communication systems is intensive and it needs to combine with cognitive radio technology. The mobile telecommunication system subscribers are sensitive to interference, making the interference problem need prompt solution. This paper analyzes the inter-system and intra-system interference and proposes the approach of utilizing spectrum holes classification. The spectrum...
Spectrum hole has the time-varying characteristic in cognitive radio. The activity of the primary user is one of the concerned factors in time-varying characteristic. Another factor is that the second users, who monitor the activity of the primary user s in different geographic locations, could get various arrival rates of primary users on the same spectrum hole. The third factor is the probability...
The introduction of cognitive radio relieves the pressure brought by the lack of spectrum resources. However, it also brings new problems to the resources scheduling. The currently existed scheduling algorithms have not considered the different identities of primary users (PUs) and secondary users (SUs), delay urgency and implementation progress. Considering the different demands on the spectrum scheduling...
A cognitive radio should avoid interference from secondary users to primary users. However, the unknown location of primary receiver makes the problem hard to solve. This paper proposes a novel primary receiver detection to change the passive state of primary receivers. Primary receiver informs the secondary user it's licensed receive frequency according to semaphore architecture via mapping method...
The existing spectrum sharing schemes in cognitive radio have difficulties on guaranteeing the quality of service of secondary system. This paper proposes a risk-estimation based spectrum leasing (RESL) scheme which applies to cellular networks in cognitive radio. In RESL, primary systems are not privileged to take back the spectrum leased unconditionally, and determine whether to lease spectrum according...
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