共查询到5条相似文献,搜索用时 0 毫秒
1.
Resource allocation in orthogonal frequency division multiple access‐based cognitive radio systems with minimum rate constraints 下载免费PDF全文
Li Li Changqing Xu Pingzhi Fan Jian He 《International Journal of Communication Systems》2014,27(8):1147-1159
In this paper, resource allocation problem in orthogonal frequency division multiple access‐based cognitive radio (CR) systems to maintain minimum transmission rate constraints of CR users (CRUs) with the specified interference thresholds is investigated. Firstly, a single primary user (PU) CR system is considered, and a suboptimal resource allocation algorithm to maximize the sum transmission rate of all CRUs is proposed. Secondly, the single‐PU scenario is extended to multiple‐PU case, and an asymptotically optimal resource allocation algorithm is proposed using dual methods subject to constraints on both interference thresholds of PUs and total transmit power of all CRUs. Analysis and numerical results show that, in contrast to classical resource allocation algorithms, the proposed algorithm can achieve higher transmission rate and guarantee each CRU's minimum transmission rate in both scenarios. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
2.
Two‐tier heterogeneous networks (HetNets), formed by deploying small cell base stations (SBSs) over existing macrocells, can enhance the network performance in future fifth generation network. However, the cross‐/co‐tier interference in HetNets also will severely influence the user throughput of both tiers. In this paper, we investigate the resource allocation and interference mitigation problem in cluster based orthogonal frequency division multiple access (OFDMA) two‐tier HetNets. In a typical cluster, one SBS is selected as the cluster head to allocate resources among all small cells to guarantee their throughput requirements. Hybrid access policy enables small cells to suppress the cross‐tier interference and earn additional revenue from macrocells, but it also leads to decrease of available resources for small cell users (SUs). To compensate hybrid access SBSs for their resources loss, we impose hierarchical SU throughput constraints on the optimization problem, which guarantee these small cells more resources than closed access ones. Besides, the cross‐tier interference constraint is also considered to protect the transmissions of macrocell users. Accordingly, a subgradient iteration based resource allocation algorithm is proposed. Numerical results show that the proposed algorithm can satisfy SU throughput constraints of all small cells with different access policies and guarantee quality of service requirements of all accessed macrocell users in hybrid access small cells. 相似文献
3.
Rung‐Shiang Cheng Chung‐Ming Huang Guan‐Shiun Cheng 《Wireless Communications and Mobile Computing》2016,16(16):2477-2494
The Long Term Evolution‐advanced cellular network is designed for human‐to‐human communication. When a large number of machine‐to‐machine (M2M) devices are trying to access the network simultaneously, it leads to a low random access (RA) successful rate and high congestion problem, which may cause the waste of radio resources, packet loss, latency, extra power consumption, and the worst, M2M service error. There is an urge to propose an efficient method for M2M communication on the LTE‐A network to resolve the congestion problem. In this paper, we propose a congestion reduction mechanism, which can analyze and model the RA procedure on the Long Term Evolution‐advanced network, to find out the collapse point in the RA procedure and then design a scheme named device‐to‐device cooperative relay scheme to relieve the congestion problem. Meanwhile, this work also adds a relay access barring algorithm to improve performance and an RA resource separation mechanism for human‐to‐human communication. The proposed method can effectively reduce the network congestion problem. Simulation results show that the network throughput and the congestion can be significantly improved using the proposed mechanism. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
4.
Qianxi Lu Tao Peng Wei Wang Wenbo Wang Chao Hu 《International Journal of Communication Systems》2010,23(2):252-274
Cognitive radio makes it possible for an unlicensed user to access a spectrum opportunistically on the basis of non‐interfering to licensed users. This paper addresses the problem of resource allocation for multiaccess channel (MAC) of OFDMA‐based cognitive radio networks. The objective is to maximize the system utility, which is used as an approach to balance the efficiency and fairness of wireless resource allocation. First, a theoretical framework is provided, where necessary and sufficient conditions for utility‐based optimal subcarrier assignment and power allocation are presented under certain constraints. Second, based on the theoretical framework, effective algorithms are devised for more practical conditions, including ellipsoid method for Lagrangian multipliers iteration and Frank–Wolfe method for marginal utilities iteration. Third, it is shown that the proposed scheme does not have to track the instantaneous channel state via an outage‐probability‐based solution. In the end, numerical results have confirmed that the utility‐based resource allocation can achieve the optimal system performance and guarantee fairness. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
5.
Localizing machine‐type communication (MTC) devices or sensors is becoming important because of the increasing popularity of machine‐to‐machine (M2M) communication networks for location‐based applications. These include such as health monitoring, rescue operations, vehicle tracking, and wildfire monitoring. Moreover, efficient localization approaches for sensor‐based MTC devices reduce the localization error and energy consumption of MTC devices. Because sensors are used as an integral part of M2M communication networks and have achieved popularity in underwater applications, research is being conducted on sensor localization in both underwater and terrestrial M2M networks. Major challenges in designing underwater localization techniques are the lack of good radio signal propagation in underwater, sensor mobility management, and ensuring network coverage in 3D underwater M2M networks. Similarly, predicting the mobility pattern of MTC devices, trading‐off energy consumption and location accuracy pose great design challenges for terrestrial localization techniques. This article presents a comprehensive survey on the current state‐of‐the‐art research on both terrestrial and underwater localization approaches for sensor‐based MTC devices. It also classifies localization approaches based on several factors, identifies their limitations with potential solutions, and compares them. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献