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Cognitive Radio is a promising solution for the problem of spectrum under utilization. Cognitive Radio Network consists of licensed(Primary) and unlicensed (Secondary) users. Secondary users can occupy the licensed bands till the arrival of a primary user. Due to the features of cognitive radio network the TCP performance is greatly affected. In this project, intra-flow network coding and Dynamic...
Cognitive radio is the one of the technique which used to solve the problems of spectrum inefficiency and limited spectrum availability in wireless networks. However, while designing the availability and efficiency of spectrum in wireless network the security in cognitive radio is one of the key challenge. The selfish attack is one of major security issue found in cognitiveradio. The selfish attack...
The emergence of cognitive radio network technology provides network nodes with abundant licensed and unlicensed channels to select for routing. Traditional routing methods that minimize hop count often do not leverage the full capabilities of cognitive radio users. They may select high lossy links or choose arbitrarily among the different paths of the same minimum length, regardless of the often...
Cognitive Radio (CR) networks allow users to opportunistically transmit in the licensed spectrum bands, as long as the performance of the Primary Users (PUs) of the band is not degraded. Consequently, variation in spectrum availability with time and periodic spectrum sensing undertaken by the CR users have a pronounced effect on the higher layer protocol performance, such as at the transport layer...
In cognitive radio settings with highly dynamic primary activities and with small opportunities for secondary access, the requirement to fairly distribute the temporarily available spectral ranges among the unlicensed users turns out to be of particular relevance. The current paper addresses this issue by presenting a new design formulation that aims to optimize the performance of an orthogonal-frequency-division-multiple-access...
Cognitive radio (CR) technology is a promising solution to enhance the spectrum utilization by enabling unlicensed users to exploit the spectrum in an opportunistic manner. Since unlicensed users are considered as temporary visitors to the licensed spectrum, they are required to vacate the spectrum when a licensed user appears. Due to the randomness of the appearance of licensed users, disruptions...
The cognitive cooperative system with coexisting scenario of multiple primary users and one secondary capable of relaying is considered. The primary users transmit packets in orthogonal sub-channels. According to the cognitive principle, the secondary activity cannot interfere with the primary performance. Therefore, in this paper, the secondary user makes use of the spectrum when sensed idle. Based...
In this paper, we propose a dynamic TDMA slot reservation (DTSR) protocol for cognitive radio ad hoc networks. Quality of Service (QoS) guarantee plays a critically important role in such networks. We consider the problem of providing QoS guarantee to users as well as to maintain the most efficient use of scarce bandwidth resources. A dynamic frame length expansion and shrinking scheme that controls...
Recently, multichannel protocols have been proposed and shown to significantly improve the aggregate throughput compared to single channel protocols. However, some existing proposals still suffer from low channel utilization or unfair bandwidth allocation between different flows in a multihop wireless network. In this paper, we design an asynchronous multichannel MAC called the cooperative multichannel...
Cognitive radio (CR) is a promising solution to improve the spectrum utilization by enabling unlicensed users to exploit the spectrum in an opportunistic manner. However, because unlicensed users are considered as temporary visitors to the licensed spectrum, they are required to vacate the spectrum when a licensed user reuses the current spectrum. Due to the randomness of the reappearance of licensed...
How to realize the cognitive capability is a key point to realize the cognitive wireless network. The research of cognitive wireless network is still at the primary stage, even not having a unique, accepted network architecture and implementation method. The construction of knowledge base in cognitive wireless network based on network situation-aware in the paper is deeply investigated in unfixed...
Cognitive radio is a promising technology aiming to improve the utilization of the radio electromagnetic spectrum. A cognitive radio device uses general purpose computer processors that run radio applications software to perform signal processing. The use of this software enables the device to sense and understand its environment and actively change its mode of operation based on its observations...
We study two distinct, but overlapping, networks which operate at the same time, space and frequency. The first network consists of n randomly distributed primary users, which form either an ad hoc network, or an infrastructure supported ad hoc network in which l additional base stations support the primary users. The second network consists of m randomly distributed secondary or cognitive users....
The recent advance in the intelligent transportation system (ITS) has led the FCC to allocate 7 channels at 5.9 GHz band for wireless access for vehicular environments (WAVE) systems. The key challenge of multi-channel access in vehicular ad-hoc networks (VANET) is to cope with the dynamic channel condition due to highly mobile nodes, while providing fair spectrum share among nodes. In this paper,...
Fixed multiplexed access radio networks can realize collision-free transmission while suffering low flexibility, especially in ad hoc communication. This paper demonstrates that a dynamic spectrum access based cooperative relay technology, defined as cognitive relay, contributes toward improving the flexibility of fixed radio networks to bursty heavy traffic, unbalanced traffic loads and terminal...
Cognitive radios permit dynamic control of physical layer resources such as transmission power and constellation size; these degrees of freedom can be employed to achieve significant improvements in network throughput above that obtainable using conventional radios (with fixed transmission power and constellation size). In this paper we present a unified framework for coordinated resource allocation...
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