By allowing to utilize the unlicensed spectrum band, the New Radio Unlicensed (NR-U) is a key technology of the fifth-generation (5G) wireless system to relieve the shortage issue of licensed spectrum bands. In this p...
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ISBN:
(纸本)9781728173276
By allowing to utilize the unlicensed spectrum band, the New Radio Unlicensed (NR-U) is a key technology of the fifth-generation (5G) wireless system to relieve the shortage issue of licensed spectrum bands. In this paper, we investigate the WiFi and 5G NR coexisted network, where the NR base stations implement the mode selection procedure to use either the licensed spectrum band or the unlicensed spectrum band. Leveraging the stochastic geometry, we present a tractable mathematical framework to characterize the medium access probability, the conditional coverage probability for different types of access points and the overall coverage probability. The accuracy of the analytical evaluations is validated by simulations. Our results show that the incorporation of NR-U can improve the overall network performance by comparing with the performance of the stand-alone cellular network. In addition, there is an optimal mode selection probability (i.e., the probability of switching to use the unlicensed spectrum band) which maximizes the overall coverage probability.
The ant system algorithm （ASA） has proved to be a novel meta-heuristic algorithm to solve many multivariable problems. In this paper, the earth coverage of satellite constellation is analyzed and a n ＋ 1^ -fold cov...
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The ant system algorithm （ASA） has proved to be a novel meta-heuristic algorithm to solve many multivariable problems. In this paper, the earth coverage of satellite constellation is analyzed and a n ＋ 1^ -fold coverage rate is put forward to evaluate the coverage performance of a satellite constellation. An optimization model of constellation parameters is established on the basis of the coverage performance. As a newly developed method, ASA can be applied to optimize the constellation parameters. In order to improve the ASA, a rule for adaptive number of ants is proposed, by which the search range is obviously enlarged and the convergence speed increased. Simulation results have shown that the ASA is more quick and efficient than other methodV211.71s.
Unmanned aerial vehicles (UAVs) can be used as low-altitude flight base stations to satisfy the coverage requirements of wireless users in various scenarios. In practical applications, since the transmitted power and ...
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Unmanned aerial vehicles (UAVs) can be used as low-altitude flight base stations to satisfy the coverage requirements of wireless users in various scenarios. In practical applications, since the transmitted power and energy resources of the UAVs are limited and the propagation environments are complicated and time-variant, it is challenging to control a group of UAVs to ensure coverage performance while preserving the connectivity and safety of the UAV networks. To this end, a two-step environment-learning-based method is proposed for the intelligent deployment of the UAVs. First, a machine learning algorithm is used to establish an accurate prediction model of the link qualities from the UAVs to the users under a specific scenario for the next step. Then, a modified deep deterministic policy gradient (DDPG) algorithm is employed to control the movements of the UAVs according to the predicted link qualities and to maximize the proportion of covered users. The prioritized experience replay mechanism is introduced to the standard DDPG algorithm to accelerate the deployment procedure. The coverage performance is analyzed in both the interference-free situation and the situation with co-channel interference. Simulation results have shown that the proposed method has a higher convergence speed than the standard DDPG method. Additionally, the proposed deployment method can achieve higher coverage performance and better adaptability to the dynamic environment than three commonly used methods, the random method, the K-means-based method, and the statistical-channel-model-based method.
At present,Earth observation satellites mainly rely on the ground stations to upload mission instructions,and only use their own payloads to complete data *** is no cooperation based on real-time collected information...
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At present,Earth observation satellites mainly rely on the ground stations to upload mission instructions,and only use their own payloads to complete data *** is no cooperation based on real-time collected information between satellites,thus the system response ability is *** is difficult to achieve continuous monitoring of hot spots and continuous tracking and confirmation of sensitive targets,so the intelligence of space-based systems is not *** present,with the rapid increase in the number of satellites in orbit,the gradual establishment of inter-satellite communication network,and the continuous improvement of satellite storage and computing capabilities,space systems have the basis to achieve swarm *** at the requirement of intensive observation in hot spots,this paper designs a low orbit hybrid *** on the realization of the information sharing in the cluster,this paper studies how to rationally configure the cooperative relationship and spatial layout of various satellites to realize the requirement of continuous monitoring of hot spots and continuous tracking and confirmation of sensitive targets.
When environmental monitoring and target tracking are carried out in harsh and unattended environment, the deployment of nodes in wireless sensor networks affects the monitoring effect and deployment cost of the netwo...
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ISBN:
(纸本)9781450384087
When environmental monitoring and target tracking are carried out in harsh and unattended environment, the deployment of nodes in wireless sensor networks affects the monitoring effect and deployment cost of the network. In order to effectively improve network coverage and utilization of network resource, and achieve the best coverage effect by deploying the least number of network nodes, a coverage optimization strategy for wireless sensor networks based on adaptive virtual force disturbance sparrow search algorithm is proposed. Firstly, the adaptive virtual force algorithm is designed for different scale deployment, and the sparrow search algorithm is disturbed by the adaptive virtual force algorithm, which accelerates the convergence speed of the algorithm. Secondly, by analyzing the scrounger characteristics of the sparrow search algorithm, an elite selection strategy is designed to improve the sparrow search algorithm, which overcomes the disadvantage that the algorithm is easy to fall into local optimum in the later iteration stage and improves the global convergence performance of the algorithm. The simulation results indicate that compared with the coverage efficient virtual force algorithm, the sparrow search algorithm and the virtual force-directed particle swarm optimization, this final coverage rate of this algorithm increased by 8.6%, 4.6%, 4.1%, and coverage efficiency improved by 6.3%, 3.3%, 2.9%, respectively. In addition, the algorithm has obvious performance advantages in terms of moving distance of nodes.
To guarantee the rapidly increasing applications of electrical consumer, ultra small cells have been proposed to provide high spectral efficiency. However, which are severely constrained by the inter-cell interference...
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ISBN:
(纸本)9781467398152
To guarantee the rapidly increasing applications of electrical consumer, ultra small cells have been proposed to provide high spectral efficiency. However, which are severely constrained by the inter-cell interference (ICI) when the system load is high, and the enhanced inter-cell interference coordination (eICIC) is key to improving performance. To quantify the performance gains from eICIC to the load-varied small cells, a stochastic-geometry model is established in this paper, and the successful coverage probability with a dynamic frequency resource allocation (DFRA) scheme adaptive to the varied system load is researched, in which the small cell base station (SCBS) location is modeled as a Poisson point process. The proposed DFRA scheme can decrease ICI through the cooperation of adjacent SCBSs, which results in the correlated spectral usage in adjacent SCBSs. Several approximations are used to handle this kind of correlation, and a Bayesian theory based evaluation method is proposed to derive the asymptotic expression of successful coverage probability. Simulation results show that these approximated expressions match well with the simulated results, and the proposed DFRA can effectively decrease ICI and significantly increase the success coverage probability.
This paper shows us the coverage performance and Doppler shift of the IGSO constellation with 2,3 or 4 satellites,and then contrasted with the GEO *** IGSO constellation is better than GEO satellite in average elevati...
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This paper shows us the coverage performance and Doppler shift of the IGSO constellation with 2,3 or 4 satellites,and then contrasted with the GEO *** IGSO constellation is better than GEO satellite in average elevation angle and multi-satellite *** is concluded after simulation and analysis that the IGSO constellation with 3 or 4 IGSO satellites can provide higher coverage performance for the Chinese areas and nearby,especially communication elevation in high latitude area,just with a small Doppler shift *** IGSO satellite constellation can be used more properly as the regional mobile satellite communication constellation.
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