110 research outputs found

    Impact of Primary Network on Secondary Network With Generalized Selection Combining

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    Resource Allocation in OFDM-Based Cognitive Two-Way Relay Networks

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    Cognitive radio (CR), nowadays, is considered as one of the most promising techniques which introduce the flexible usage of radio spectrum and improve the spectral efficiency by enabling unlicensed users to exploit the licensed spectrum in an opportunistic manner. Moreover, the two-way relay communication has attracted a great attention as it introduces a relaying scheme with a bidirectional transmission to exchange information between two nodes. This strategy assumed to improve the overall capacity, since less time slots are needed than the one-way strategy, besides extending the radio coverage range of networks. Another common technique that improves the bandwidth efficiency and spectrum utilization is the orthogonal frequency division multiplexing (OFDM) technique which exhibits a distinctive efficiency in mitigating inter-symbol interference (ISI) and combating frequency selective fading. Therefore, two-way relay CR communication among OFDM terminals can take advantage of these three techniques to boost up the capacity together with the networks quality. In this thesis, an OFDM-based amplify and forward (AF), cognitive two-way multiple-relay network is considered where two transceiver nodes exchange information via relay nodes. The full transmission happens in two time slots. In the first time slot, multiple access phase (MA), the transceiver nodes send their signals to the relay nodes while in the second time slot, broadcast phase (BC), the relay nodes broadcast the received signals to the transceivers. In this dissertation, the problem to jointly optimize the network resources is considered. The first is the transmission power of transceivers and relay nodes to ensure suitable allocated power for best signals transmission besides ensuring no harmful interference is caused to the primary system. The other important resource to be optimized is the subcarrier pairing where the first and second time slots subcarriers have to be matched such that the subcarriers with the best conditions is reserved. The final tuned resource, in this work, is the relay selection where the relay node that assures the best transition of the received signal is selected. The dual decomposition technique is applied to get the optimal resource allocation. Moreover, suboptimal algorithms are proposed to perform the resource allocation reducing, significantly, the computational complexity compared with the optimal solution with small performance degradation. Finally, simulation results of the suggested AF OFDM cognitive relaying network are shown to compare the performance gain of the different algorithms which reveals that the proposed suboptimal algorithm achieves good performance with much less computational complexity than the optimal one

    Insights on Significant Implication on Research Approach for Enhancing 5G Network System

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    With the exponential growth of mobile users, there is a massive growth of data as well as novel services to support such data management. However, the existing 4G network is absolutely not meant for catering up such higher demands of bandwidth utilization as well as servicing massive users with similar Quality of service. Such problems are claimed to be effectively addressed by the adoption of 5G networking system. Although the characteristics of 5G networking are theoretically sound, still it is under the roof of the research. Therefore, this paper presents a discussion about the conventional approach as well as an approach using cognitive radio network towards addressing the frequently identified problems of energy, resource allocation, and spectral efficiency. The study collects the existing, recent researches in the domain of 5G communications from various publications. Different from existing review work, the paper also contributes towards identifying the core research findings as well as a significant research gap towards improving the communication in the 5G network system

    Recent Advances in Wireless Communications and Networks

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    This book focuses on the current hottest issues from the lowest layers to the upper layers of wireless communication networks and provides "real-time" research progress on these issues. The authors have made every effort to systematically organize the information on these topics to make it easily accessible to readers of any level. This book also maintains the balance between current research results and their theoretical support. In this book, a variety of novel techniques in wireless communications and networks are investigated. The authors attempt to present these topics in detail. Insightful and reader-friendly descriptions are presented to nourish readers of any level, from practicing and knowledgeable communication engineers to beginning or professional researchers. All interested readers can easily find noteworthy materials in much greater detail than in previous publications and in the references cited in these chapters

    On performance analysis of cognitive radios

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    Performance assessment of Narrowband IoT for Intelligent Cargo Transportation

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    Narrow Band Internet of Things (NB-IoT) is the most advanced technology standard for short message services, such as sensor data, developed by 3GPP Release 13 and beyond. The NB-IoT is deployed over Long Term Evolution (LTE) Advanced Pro infrastructure and theoretically, it offers extended coverage up to 40 km from the base station. The objective of this thesis is to analyze the performance of NB-IoT technology in cargo shipment tracking using LTE cellular networks across the coastal line. Currently, about fifty thousand cargo ships use onboard Satellite communication system for all sorts of information exchange with the onshore data centers. The Satellite communication will continue to exist, even after deployment of NB-IoT. Apart from the machine critical data of the cargo ships, the non-emergency periodic short messages for polling meteorological and container metadata such as temperature, humidity, gaseous detection, etc. will be crucial for the quality of the shipment and the traceability. In this thesis, we analyze deployment of NB-IoT sensors for cargo container to track and provide metadata about the condition of goods. We evaluate three implementation methods of NB-IoT for cargo ships, optimize the coverage and enhance the battery life of the sensor equipment. The main idea is to offload non-critical information that would otherwise use expensive Satellite links, thus embrace the NB-IoT technology at offshore and reduce the financial stress on the cargo shipments. In the first method, all the sensors transfer the periodic data directly to the coastal LTE network when the ships sail in close proximity to the shore. In the second method, the sensors transfer data to an LTE base station installed locally on the ship and then accumulated information will be relayed to onshore LTE network over NB-IoT channel. In the third method, an Unmanned Aerial Vehicle (UAV/ Drone) base station will collect the data from the onboard sensors; it then relays the information to the onshore LTE network. For all methods, when there is no LTE coverage, the accumulated data will be sent over the Satellite link, which will be available onboard. The assessment confirms the hypothesis that the packet loss probability reduces when the base station is located close to the sensor, where the number of retransmissions will be reduced, and more uplink resources will be available. For direct access scenario, a large number of users contend for Random Access Channel (RACH) simultaneously after entering into the LTE coverage. The packet will be dropped after reaching the maximum number of attempts for the RACH resources. As per the simulated results, mean lifespan of a sensor is greatly affected by the LTE network availability and random access procedure, during which the sensor spends most of the energy for transmissions. The mean transmit delay will be higher with second and third methods where the ship BS, UAV BS accumulate packets until they find the LTE network or relays the data to the Satellite link if the LTE outage is longer. This performance assessment provides technical insights for the maritime industry to embrace the NB-IoT for tracking and condition monitoring of shipment

    NASA compendium of satellite communications programs

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    A comprehensive review of worldwide satellite communication programs is reported that ranges in time from the inception of satellite communications to mid-1971. Particular emphasis is placed on program results, including experiments conducted, communications system operational performance, and technology employed
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