WLAN标准IEEE802.11ac/ad及其关键技术

阐述了WLAN技术的发展现状,并详述IEEE802.11ac/ad标准中新增关键技术。MU-MIMO及MAC层增强技术是IEEE802.11ac标准中的两大新增技术,而多频段互操作快速会话迁移（FST）技术以及自适应波束赋形技术是IEEE802.11ad标准中的关键技术改进,同时进一步阐述了802.11ad标准中支持的不同物理层类型及其应用场景。     

Wi-Fi6的多用户技术

Wi-Fi6是Wi-Fi联盟对IEEE 802.11ax的新命名方式,以便于这项Wi-Fi新技术的推广。Wi-Fi 6技术聚焦高密度场景的多用户性能、效率等方面,引入OFDMA、上行MU-MIMO等多用户技术,极大提升系统容量,降低传输时延。阐述OFDMA、MU-MIMO、MU-RTS/CTS技术的原理,详细介绍多用户场景的通信流程,并从理论角度分析Wi-Fi 6的上下行并发用户能力,最后对Wi-Fi 6技术的应用前景进行展望和总结。     

IEEE 802.11ac标准的多用户MIMO信道容量研究

IEEE 802.11ac是第五代无线局域网(WLAN)通信标准,多用户MIMO技术的应用使其通信速率和信道容量得到巨大提升,从而使IEEE 802.11ac标准日趋成为无线局域网的主流标准。本文在IEEE 802.11ac标准的随机多用户MIMO无线信道容量的计算理论的基础上,对CSI未知与已知时的随机多用户MIMO无线信道容量进行仿真,并对比分析了CSI未知与已知时不同天线配置下的随机多用户MIMO无线信道的容量。     

美国高通公司创新优化频谱使用

正近日,美国高通公司的全资子公司高通创锐讯推出带多用户MIMO(MU-MIMO)技术的Qualcomm VIVE 4-stream802.11ac解决方案,可大幅提升Wi-Fi性能,应对家庭、办公室及公共热点中持续增加的联网设备需求。凭借高通创锐讯基于算法的创新技术提升,这一全新解决方案旨在优化Wi-Fi设备获得服务的方式,充分利用额外的容量,可将网络容量提高2~3倍。     

802.11ac技术的测试方法研究

根据802.11ac的技术规范,对802.11ac标准与前一代WLAN标准802.11n的主要技术指标进行了对比分析,介绍了802.11ac的主要技术提升和技术特点,研究了相关的测试项目与测试方法,对全面开展802.11ac产品测试有参考价值.     

基于IEEE 802.11ac的多用户MIMO传输方案的优化设计及其性能分析

在IEEE 802.11ac Draft 2.0标准草案的基础上,针对其新引入的多用户MIMO传输机制进行了深入研究,提出了几点改进的优化设计方案,并完成了相应的性能分析。最后对IEEE 802.11ac的多用户MIMO传输方案进行了系统的性能分析,仿真结果表明,改进的传输方案在误比特率(BER)和吞吐量方面获得了明显的性能增益,且与针对性能的理论分析与仿真结果相吻合。     

Strategy Analytics:下一波Wi-Fi元器件浪潮伴随着两位数Wi-Fi的增长

正高通旗下Atheros近日发布的802.11n/ac MU-MIMO"Wave2"芯片表明Wi-Fi芯片演进到更高数据传输速率和容量的产品组合的下一次革命,有助于刺激市场对Wi-Fi路由器和支持Wi-Fi功能的移动终端的需求。Strategy Analytics射     

应对5G Wi-Fi新一代无线测试的挑战

被业界认为是第五代Wi-Fi的802.11ac正在呼之欲出,它与之前的Wi-Fi标准制式有哪些方面的不同,为什么会被业界如此看好。802.11ac与802.11n的技术区别802.11ac的物理层是对802.11n标准的延续,而且要满足后向兼容。下面我们来着重探讨一下在802.11ac上的变化。表1则列出了在802.11ac上主要扩展的方面。理论上说802.11n在     

无线局域网IEEE 802.11ac基本原理与测量解决方案

根据IEEE 802.11ac的标准需求以及IEEE 802.11ac基本原理的理解,全面介绍了罗德与施瓦茨公司对无线局域网IEEE 802.11ac完整而成熟的测试解决方案。     

下一代无线局域网标准802.11ac

802.11ac是新一代无线局域网技术标准,是802.11n标准的延续。在继承了已有WLAN标准中许多先进技术的基础上,802.11ac在物理层和MAC层做了一系列的技术改进,来保证高质量、高传输速率的网络服务。就像以前的每次技术标准的进步一样,802.11ac标准同样有很强的向后兼容能力,能和已有的802.11a/n网络很好的共存,为用户体验网络服务提供更多的选择。     

A dynamic location management service for group applications in cellular networks

To cope with the increasing demand of multimedia applications, new IEEE 802.11 wireless local area networks devices have been defined such as IEEE 802.11aa and IEEE 802.11ac. The former proposes new intra-access categories (AC) differentiation based on stream classification service (SCS) scheme. The latter standard allows simultaneous downlink transmissions thanks to downlink multi-user MIMO technology and sharing transmission opportunity (TXOP) period scheme. In this paper, we focus on the basis of this technique and the behavior of the access point (AP) to manage the multi-user access. Then, we propose a hybrid access mechanism entitled multi-user multi-cast access mechanism (MUMAM) that supports downlink multi-user transmissions while considering intra-AC differentiation. MUMAN considers SCS scheme to prioritize between multicast and unicast flows of an AC and follows transmissions based on IEEE 802.11ac TXOP sharing technique. Extensive simulation and analysis show that MUMAM has a significant positive impact on delay and throughput performance of different AC(s).     

Improving DL-MU-MIMO performance in IEEE 802.11ac networks through decoupled scheduling

The IEEE 802.11ac standard introduces new downlink multi-user MIMO (DL-MU-MIMO) transmissions to up to four users in order to increase spatial reuse in wireless local area networks (WLANs). We argue that even better WLAN performance can be achieved by slightly modifying the DL-MU-MIMO scheduling. To this end we propose a new queuing mechanism based on the decoupling of EDCA and DL-MU-MIMO scheduling (DEMS) to avoid head-of-line blocking. We show that DEMS outperforms traditional 802.11ac scheduling based on first in, first out transmission queues. The improvement is shown in terms throughput achieved with: (a) more efficient channel usage, (b) increased probability of transmission of high priority traffic, and (c) decreased competition between frames destined to distinct users.

     

A Novel CSI Feedback Method for Dynamic SU/MU MIMO Adaptation

Channel state information (CSI) reporting at one mobile station (MS) often targets maximizing the throughput of one single link, hence is optimized for single-user multi-input multi-output (SU-MIMO) transmission at base station (BS). However, the system wide throughput may not be maximized when BS is performing multi-user multi-input multi-output (MU-MIMO) transmission utilizing the SU-MIMO optimized CSI reports, and vice versa. This CSI mismatch can cause system throughput degradation. In this paper, a novel CSI feedback method is proposed which can switch between SU-MIMO optimized CSI reporting mode and MU-MIMO optimized CSI reporting mode when instructed by BS’s signaling. System level simulation results show when BS is performing MU-MIMO transmission, significant throughput gain can be obtained if MS feeds back MU-MIMO optimized CSI reports instead of SU-MIMO optimized CSI reports. With the instruction of the BS signaling to dynamic indicate MS to switch between SU-MIMO and MU-MIMO optimized CSI reporting modes, the SU-MIMO performance is not compromised either.     

Multiuser MIMO Transceiver Design for Uplink and Downlink with Imperfect CSI

This paper considers a joint linear transmitter and receiver design for multi-user multiple-input multiple-output (MU-MIMO) systems using total mean square error (TMSE) criterion, subject to a total transmit power constraint assuming imperfect channel state information. Both the uplink and downlink MU-MIMO systems, which is employed with improper constellations such as binary phase shift-keying and $M$ -ary amplitude shift-keying are considered. A minimum TMSE design is formulated as a nonconvex optimization problem under a total transmit power constraint and the closed-form optimum linear precoder and decoder for both the downlink and uplink MU-MIMO systems with improper modulation are determined by solving this nonconvex optimization problem. A novel contribution in this paper is to derive a closed-form optimum linear precoder and decoder for both the downlink and uplink MU-MIMO systems with improper modulation by solving the nonconvex optimization problem under total power constraint. The simulation results show that the performance of the proposed design is improved over the previous design.     

Efficient QR-Based Multi-Mode Precoding for Limited Feedback Multi-User MIMO Systems

This paper proposes QR-based criteria for efficient selection of multi-mode precoders in multi-user multiple-input multiple-output (MU-MIMO) precoded systems with a limited feedback. In particular, a MU-MIMO QR based precoding scheme is developed which takes advantage of the overall precoder design among users in conjunction with QR detection. A selection criterion is developed to identify the precoder that yields the maximum free distance. Efficient mode selection and tree search strategies are adopted to reduce the complexity associated with the identification of the optimum precoder. To further improve the detection performance in correlated channels, an efficient QR-based MMSE V-BLAST detector is proposed. Computer simulations confirm that the proposed QR-based precoding scheme attains the performance of existing schemes with a significantly lower complexity level.     

On the sum-rate scaling law of downlink MU-MIMO decomposition transmission with fixed quality imperfect CSIT

In recent years, downlink multi-user multiple-input multiple-output (MU-MIMO) transmission techniques have attracted much attention because of their potential to significantly increase system capacity compared to single-user (SU) transmission. Unfortunately, accurate channel state information at the transmitter (CSIT) is crucial for these techniques to efficiently separate multiple users in the space domain so as to realize their capacity gain. In practice however accurate CSIT is difficult to obtain. In this letter we investigate the impact of imperfect CSIT on the system performance in terms of sum-rate scaling law for systems employing MU-MIMO decomposition scheme for downlink transmission. In particular, we derive the sum-rate scaling factors for various system configurations and find that imperfect CSIT has different effects on different categories of system configurations. Simulation results demonstrate the accuracy of our analysis.