ORLA/OLAA：LAA和WiFi在未许可频谱中的正交共存
ORLA/OLAA: Orthogonal Coexistence of LAA and WiFi in Unlicensed Spectrum
摘要：
未来的移动网络将利用未授权频谱来提高容量，并以成本效益的方式满足不断增长的用户需求。3GPP最近定义了授权辅助接入（LAA）方案以实现全球非授权LTE（U-LTE）部署，旨在（$i$）确保与现有WiFi网络的公平共存，即，对它们的性能的影响不超过另一个WiFi设备，以及（$ii$）与WiFi相比，实现更好的通话时间效率。在本文中，我们表明，标准化的LAA未能同时满足这些目标，并设计了一种替代的正交（无冲突）先说先听的共存模式，提供了一个显着的性能改善，但不对现有的WiFi网络的惩罚。我们推导出两个LAA最优传输策略，ORLA和OLAA，最大化LAA吞吐量在异步和同步（即，与许可的锚帧边界对齐）操作模式。我们提出了一个全面的性能评估，通过它，我们证明，当聚合数据包，IEEE 802.11 ac WiFi可以比3GPP LAA更有效，而我们的建议可以达到100%更高的吞吐量，而不会损害WiFi。我们进一步表明，长的U-LTE帧在使用3GPP LAA时，在WiFi上会导致高达92%的吞吐量损失，而ORLA/OLAA即使在存在非饱和WiFi和/或多速率场景的情况下，也可以免费维持$>$ 200%的增益。
英文摘要：
Future mobile networks will exploit unlicensed spectrum to boost capacity and meet growing user demands cost-effectively. The 3GPP has recently defined a Licensed-Assisted Access (LAA) scheme to enable global Unlicensed LTE (U-LTE) deployment, aiming at ($i$) ensuring fair coexistence with incumbent WiFi networks, i.e., impacting on their performance no more than another WiFi device, and ($ii$) achieving superior airtime efficiency as compared to WiFi. In this paper we show the standardized LAA fails to simultaneously fulfill these objectives, and design an alternative orthogonal (collision-free) listen-before-talk coexistence paradigm that provides a substantial improvement in performance, yet imposes no penalty on existing WiFi networks. We derive two LAA optimal transmission policies, ORLA and OLAA, that maximize LAA throughput in both asynchronous and synchronous (i.e., with alignment to licensed anchor frame boundaries) modes of operation, respectively. We present a comprehensive performance evaluation through which we demonstrate that, when aggregating packets, IEEE 802.11ac WiFi can be more efficient than 3GPP LAA, whereas our proposals can attain 100% higher throughput, without harming WiFi. We further show that long U-LTE frames incur up to 92% throughput losses on WiFi when using 3GPP LAA, whilst ORLA/OLAA sustain $>$200% gains at no cost, even in the presence of non-saturated WiFi and/or in multi-rate scenarios.
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