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Systems comprised of Cognitive Radio Networks (CRN) have been gaining attention in the current literature, given their ability to reduce spectrum scarcity by reusing parts of the spectrum band, while at the same time ensuring a minimum Quality of Service (QoS) margin. In this regard, it becomes important to consider the CRN's usage of multiple access protocols. In this paper, we consider a CRN with...
This paper investigates the performance of a Cognitive Radio Network, emphasizing the secondary users performance. Users are modeled by a priority M/G/1 queue, in which primary users have a higher priority than secondary users. The performance of the system is evaluated by a performance metric called Power Metric. We considered that transmissions occur over a Nakagami-m channel model. Different modulation...
This paper introduces an extension of a methodology for calculating the average delay in a cognitive radio network using the slotted aloha technique for medium access. This extension includes two new aspects: imperfect sensing and different transmission power levels in the secondary stations regarding the channel state decision. The performance of the network is evaluated and numerical results are...
In this paper we evaluate the performance of the opportunistic spectrum access in a cognitive radio network considering cooperative and non-cooperative spectrum sensing. For the case of cooperative sensing the hard decision fusion using the k-out of-N rule is considered. Furthermore, numerical results are presented comparing both approaches in terms of different parameters.
The combination of cognitive radios with adaptive modulation has been studied in order to improve the performance of wireless networks. The key issue when defining the performance of an adaptive modulation system is finding the switching point between neighboring modulations. In this paper, we investigated the performance of a Cognitive Radio Network, emphasizing the secondary user's performance,...
It is expected that the fifth generation (5G) of mobile networks will be standardized in 2020. For this new generation, there are several new performance requirements in addition to higher data rates. E-health and the Internet of Things (IoT) are two important applications that define the new requirements. In this paper, we discuss several technological trends in wireless communications towards 5G...
The Cognitive Radio Network is an important technology for next generation wireless networks. In [1], the performance of Cognitive Radio Networks, using Slotted Aloha multiple access protocol, is analyzed considering Capture Effect in the primary and secondary networks. The Packet Error Rate due to interference between primary and secondary stations is not considered. In this paper, we propose an...
The development of wireless networks can damage networks Transport Layer operation. There has been much research effort to solve these problems. One of the approaches is known as Cross-Layer Design (CLD), where interactions between non-adjacent layers, forbidden by the layered model, become possible. However, CLD proposals must be carefully tested in order to discover if a gain in one parameter does...
Random Access Channel (RACH) is the uplink common channel defined in the Universal Mobile Telecommunication System (UMTS). For a better utilization of UMTS resources is very important to predict the performance of this channel. In this paper we analyze RACH throughput, considering multiple demodulation resources in the Node B. New expressions to compute the success and collision probabilities in the...
In multi-carrier modulation (MCM) systems multiple relatively narrowband sub-carriers are used to alleviate the undesirable influence of frequency selective fading. This paper analyses the performance of MCM data links when forward error correction is employed either in each sub-carrier or in the main stream of bits. The influences on system performance of interleaving and suppression of the poorest...
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