哇。802.11ac Wave 2.这是什么内容？
好吧，比以往任何时候都关乎天线。你必须做对了。
The primary functional enhancements/differentiators to 11ac are:
- 更广泛的频道
- More streams
- 802.11AC显式波束形成
- Mu Mimo
让我们看看这个。更广泛的渠道是自我解释的。
Bigger is better. Right? (Well maybe, but that is the topic for another blog)
The other 3 items are intimately tied to the transceiver and antenna sub-system in the access point.
本文是众多文章中的第一篇，它将带您从最简单的天线构造中，电子构造，电子在电线上流动到Mu Mimo，这是当今无线电芯片组和精制天线中可用的令人敬畏的计算功率的最终混合物设计。
You'll notice that I did not say complicated antenna design. It is quite the opposite in fact. 11ac beamforming and 11ac MU MIMO drive radio system design to use high quality but VERY simple antenna designs, usually omnis.
Here are some concepts to start your brain:
1. 11AC射击实际上是该功能提供的标签不足的标签。
- Beamforming implies that the function is somehow limited to the AP and its local antenna subsystem
- A far better description of this would be to refer to it as 11ac channel optimization. This is because the scope of this capability includes EVERYTHING that is in the path between the digital portion of the AP and the digital portion of the client. All of the analog impairments in the transmitters and receivers, and all of the interactions of the RF waves and the objects around the AP are included in the calculation. The capability, in a single exchange of a channel sounding packet, establishes the optimum excitation of the antennas on the APs to deliver the highest possible signal strength to the client AND maximizes MIMO operation at the same time. This is repeated many time per second to track the user as they moveBy contrast "smart antenna" steered beam solutions attempt to maximize signal strength, they take a while to build up their location estimate, and they can actually impair the capability of the client/AP system to support multiple streams.
2.支持更多的流需要更多的自由度
Q: What the heck does that mean?
A: In the simplest terms this relates to the number of antennas and the number of paths (bounces) excited.
- A closed space like a meeting room, an enclosed courtyard, and so on will have MANY MANY reflection paths. In those situations even 2 or 3 bounce paths may have a lot of energy on them. As a result these spaces are characterized as having many degrees of freedom. If the degrees of freedom exceeds the number of antenna then the full number of streams may be supported with single user MIMO and Multi user MIMO
- 一个没有反射表面或遥远反射器的开放区域（意味着反射上的低信号强度）没有或非常有限的自由度，因此将难以为MIMO操作支持超过1个流
- An open field environment MAY be able to send signals to more than one use in MU MIMO operation but only with very specific conditions in place.
- The number of streams cannot exceed the minimum of the number of antennas at the transmitter or the receiver
Q: What does that mean for antenna design?
答：让我们考虑一下：
- 让我们看一下室内案例。我们知道，许多/大多数室内环境都提供了许多自由度。最大程度地提高反射路径并为以角度质量质量元素为角度广泛间隔的用户是最好的解决方案。这些情况通常不需要极化多样性。还请注意，反射过程也随机化了极化。使用固定或转向方向溶液将降低自由度，因为将大大减少对天线方向性的路径数量。因此，“智能天线”与优质的多流单用户MIMO或多用户MIMO不一致。
- 在单用户MIMO的室外情况下，我们可以引入2nddegree of freedom by using antenna polarization. Polarization is the direction of the electric field. Horizontally and vertically polarized waves are physically and mathematically distinct and so can be used to send 2 streams of independent data. Thus, polarization can be used to create a 2nddegree of freedom in this environment. NOTE: there are only two polarizations that are separate. Anything else is a combination of the two independent states.
- 在户外的情况下for multi user MIMO there are certain instances where you can use an array of antenna elements to create beam patterns that are distinct. In general for N antennas you can create N-1 nulls. The tradeoff is that all of the elements in the array have to be the same polarization AND in general they need to be matched omni patterns. The simplest case I can give you is if a MU MIMO radio has to send to one user in front and one behind the basic radiating element needs to be able to see both clients at the same time. This has significant implications for providers of "smart antenna" solutions that steer directional antenna patterns. Simply put those solutions are completely inconsistent with MU MIMO operation in outdoor situations.
因此，那些高级快照。如图所示，更多的文章将遵循并详细解释这些文章（图片），以及更深入的潜水范围的实际工作方式，访问点上的天线放置如何影响该光束，并最终如何将其映射到MU MIMO。
Next Article:http://community.arubanetworks.com/t5/Technology-Blog/Wave-2-MIMO-and-Polarization/ba-p/234087
