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Under the constraints of limited bandwidth and exponentially rising user demand, there is a dire need to maximize throughput. Maintaining Quality of Service (QoS) in a communication network demands congestion control with high accuracy. This paper focuses on this challenging task that incorporates design of effective congestion controller to reduce packet loss in cognitive radio networks. Limited...
Increasing the flexibility in spectrum access is a key to enhanced efficiency in radio spectrum utilization. Noncontiguous carrier aggregation (CA) is one enabling technology towards more flexible spectrum access, but can also lead to serious implementation challenges in terms of transmitter lin-earity. Especially when a single power amplifier (PA) is deployed for all carriers, serious intermodulation...
Recently various cognitive radio network models are suggested and analyzed. In particular, cooperative cognitive radio network model considers cooperative relaying of secondary users in cognitive radio networks, which utilize the spectrum occupancy efficiently. However, such cooperation may not occur when secondary users have a better alternative, spectrum leasing. Therefore, in this paper, we study...
Data fusion has been a key technology of cooperative spectrum sensing in cognitive radio. To solve network collaborative information compression distortion under limited bandwidth, we proposed a nonuniform quantization scheme for each sensing nodes. Simulation results show that the proposed scheme could improve detection probability compared to conventional uniform quantization. And the fusion performance...
This paper investigates the call-level performance of a cognitive radio network for dynamic spectrum access providing multimedia service to secondary users. The serving system is modeled by a two-dimensional state-transition diagram and a novel approximate but computationally efficient analytical approach for solving its state probabilities is developed. A new precise formula for evaluation of the...
Cognitive radios (CR) provides a promising solution to the problem of spectrum scarcity by increasing spectrum efficiency. CR coexists with the licensed users in a network. The network is assumed to be ad-hoc in nature where the master/controller of this ad-hoc network coordinates for spectrum allocation with the surrounding CR. In this paper, a two level hierarchical fuzzy system for adaptive bandwidth...
Spectrum sensing is the key functionality of cognitive radio. To combat with the effects of destructive channels, cooperative spectrum sensing technique among multiple secondary users has been proposed in cognitive radio networks. In this paper, we present an optimal cooperative spectrum sensing strategy to maximize the sensing efficiency, which not only concerns with the system overhead of spectrum...
Dynamic Spectrum Access (DSA) has the potential to vastly improve spectrum utilizations among heterogeneous networks. We present a continuous-time Markov chain (CT-MC) model to analyze the performance of three co-located cognitive systems with various priority classes and bandwidth requirements. The maximum spectrum utilization and minimum blocking probability are derived in a one-channel band scenario...
To fully utilize radio resources by intelligently filling in as much radio spectrum gaps as possible, the concept of cognitive radio network has been well accepted. A challenge inherent in this technology is how to build a mechanism that can allocate resource by learning and adapting to a specific radio transmission environment. In this paper, we propose a cognitive resource management scheme that...
In this paper, an energy efficient adaptive modulation scheme is proposed for a wireless cognitive radio ad hoc network, where each node is equipped with cognitive radio and the network is an OFDMA system operating on time slots. In each slot, the users with new traffic demand will sense the spectrum and locate the available subcarrier set. Then they choose subcarriers with favorable channel condition...
Cognitive radio presents a new approach to wireless spectrum utilization and management. In this work, the potential performance improvement gained by applying cognitive radio to multiple-provider wireless systems is investigated. It is shown that virtual wireless networks can be created, utilizing only the residual wasted bandwidth of the primary service providers. These virtual networks are able...
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