共查询到16条相似文献,搜索用时 53 毫秒
1.
2.
为了应对移动数据日益增长的需求,3GPP(3rd Generation Partnership Project)对LTE(Long Term Evolution)扩展到非授权频段展开了相关讨论。LAA(Licensed-Assisted Access),亦称为LTE-U(Unlicensed LTE),与目前已经运行在5GHz非授权频段上的其他无线接入技术(如Wi-Fi)的共存问题,成为了研究的焦点。本文主要研究了在非授权频段上运行LTE和Wi-Fi系统共存的机制,设计实现了基于LAA和Wi-Fi共存场景的系统级仿真平台。仿真结果表明,在非授权频段上LAA能与Wi-Fi和谐共存。针对LAA系统设计一种合理的退避机制,能够同时提升LAA和Wi-Fi系统的吞吐量,提高资源分配的公平性和使用效率。 相似文献
3.
随着信息通信技术(information and communication technology,ICT)的进步以及数据流量的不断增加,需要越来越多的免授权频段资源支持无线通信和物联网的发展。为了研究未来免授权频段的通信发展方向以及频谱需求,首先综述了现有免授权频段政策、免授权频段通信技术及免授权频段通信的若干具体应用场景。以下一代Wi-Fi和超宽带(ultrawideband,UWB)技术为例,根据现有应用的数据流量预测,分析了未来的免授权频谱需求。结果表明,为了满足未来增强现实/虚拟现实(augmented reality/virtual reality,AR/VR)、高精度定位及8K高清视频传输等应用需求,更多的6 GHz以及60 GHz免授权频段资源需用来支持新型业务。最后对未来免授权频段的发展趋势进行探讨,指出干扰管理等技术是未来提升免授权频段利用效率的关键。 相似文献
4.
认知无线电是一种基于软件无线电的智能通信系统,它能够认知周围环境,并能通过一定的方法相应地改变某些工作参数来实时地适应环境,从而达到提高频谱利用率、缓解频谱资源紧张的目的.授权频段的频谱利用问题是认知无线电实现的关键技术之一.研究了授权频段的两种频谱利用方法:动态频谱接入和基于动态频谱接入模型之一的机会频谱接入. 相似文献
5.
LTE授权辅助接入(LAA)和WiFi网络的共存性能已经被广泛研究。然而,这些工作忽略了捕获效应,即当两个以上的信号在相同信道上同时传输时,最强的信号仍然可能成功接收。这种现象在共存场景中可能比在WiFi网络中更频繁地发生。基于此,该文深入研究了LAA和WiFi网络在捕获效应下的共存性能。具体地,在共存场景中首先提出了两个以上信号的捕获模型,并推导出了捕获概率;然后,将LAA接入方案建模为具有捕获效应的新的2维离散马尔可夫模型,其中退避计数器的减少不仅取决于空闲的时隙,还取决于捕获效应发生的时隙;最后推导出共存性能的表达式。大量的仿真和数值结果验证了所提出的马尔可夫链和捕获模型的有效性。而且,仿真结果也证明了考虑捕获效应的必要性。 相似文献
6.
7.
8.
文章首先介绍了LTE(Long Term Evolution)系统,然后描述了终端RRC(Radio Resource Control,无线资源控制)层的协议框架及主要服务功能,最后详细地说明终端RRC初始连接建立过程,包括RRC连接建立的消息流程图,MAC(Medium Access Control,媒介接入控制)层基于竞争解决的随机接入等过程. 相似文献
9.
10.
11.
12.
To enable the coexistence of Licensed Assisted Access (LAA) and Wi‐Fi in 5 GHz unlicensed bands, a new channel access mechanism is proposed. Accounting for the fairness between LAA and Wi‐Fi, the proposed mechanism finds the optimal transmission time ratio by adaptively adjusting the transmission durations for LAA and Wi‐Fi. In addition, we propose a new analytical model for the distributed coordination function of IEEE 802.11 through some modifications of conventional analytical models for saturation and non‐saturation loads. By computing the activity ratio of Wi‐Fi, the proposed analytical model is able to control the time ratio between LAA and Wi‐Fi, which is required for practical implementation of the proposed access mechanism. Through numerical simulations, the proposed channel access mechanism is compared with conventional methods in terms of throughput and utility. 相似文献
13.
介绍了无线接入网中的两种关键技术,OFDM(正交频分复用)和CDMA(码分多址),从调制技术,抗干扰能力,功率控制、网络规划,峰均功率比和均衡技术等方面全面系统地比较分析了OFDM和CDMA各自的优缺点,结果证明了OFDM技术的先进性及其令人瞩目的应用前景。 相似文献
14.
战场信息管控关键技术研究及应用 总被引:1,自引:0,他引:1
信息战已成为现代战争的主要特点,而要赢得信息战,在很大程度上取决于对战场信息的有效管理与控制。基于信息化战场的需求,考虑了战场信息海量、多元、复杂、动态、异构、移动等特点,以及信息交互的精确性、实时性、可靠性和安全性要求,从信息感知、信息访问、信息传送控制和支撑服务四个方面,对实现战场信息有效管控的关键技术进行了探讨,并结合实际工作提出了相应的解决措施和实践思路,以期对我军战场信息管控系统的研制与建设有所裨益。 相似文献
15.
In this paper, a dual‐polarized multiple‐input multiple‐output (MIMO) antenna system suitable for indoor wireless access point is proposed. The presented MIMO antenna system consists of two coplanar‐waveguide‐fed monopole antennas with orthogonally polarized modes. According to the closely spaced structure of the MIMO antenna system, the mutual coupling between the ports is a big challenge. Therefore, a new structure of parasitic element is introduced in order to improve the mutual coupling between the ports. For the purpose of validating the simulated results, the antenna prototype has been fabricated and measured; the comparison of the results shows that there is an acceptable agreement between the measurement and simulation results. The proposed design covers the frequency bands of WiFi (2.4 GHz), Worldwide Interoperability for Microwave Access (2.3 and 2.5 GHz), and Long‐Term Evolution (LTE; 1.5 and 2.6 GHz) applications with a reflection coefficient less than −10 dB and a mutual coupling coefficient better than −15 dB. The MIMO antenna system provides an envelope correlation coefficient less than 0.15, polarization diversity gain more than 9.985 dB, and quasi‐omnidirectional pattern within the expected frequency band. In addition, LTE downlink throughput measurements show that the proposed antenna system delivers data rates close to the theoretical maximum for quadrature phase shift keying, 16 quadrature amplitude modulation (QAM), and 64‐QAM modulations. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献