Wi-Fi 802.11ax @ 好人勿用™

迎接Wi-Fi新時代！2019年起Wi-Fi全面以數字命名
https://www.nownews.com/news/20181005/2999504/

Wi-Fi 聯盟現正欲改變這套規則。

未來 Wi-Fi 改以數字命名，如現行的 802.11ac 將改為 Wi-Fi 5，
下一世代 802.11ax 則為 Wi-Fi 6。

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Wi-Fi 始祖: 802.11 (1997) @ 2.4GHz
Wi-Fi 1：802.11b (1999) @ 2.4GHz
Wi-Fi 2：802.11a (1999) @ 5GHz
Wi-Fi 3：802.11g (2003) @ 2.4GHz
Wi-Fi 4：802.11n (2009) @ 2.4GHz/5GHz by MIMO (Multi-Input Multi-Output)
Wi-Fi 5：802.11ac (2014) @ 5GHz by MU-MIMO + 256 QAM
Wi-Fi 6：802.11ax (2016) @ 2.4GHz/5GHz by 4x IEEE 802.11ac

Wi-Fi 4 æ¨èªã Wi-Fi 5 æ¨èªã Wi-Fi 6 æ¨èªã

再來... Wi-Fi AP上的ACxxxx數字的由來:

AC xxxx = 5Ghz 速率 + 2.4Ghz 速率

要增加ACxxxx的傳輸速率的幾種方法...

1.) 增加天線數目
2.) 多複製一套WIFI頻道 (多頻)
3.) 提高QAM的編碼率規格

NITRO-QAM = 1024QAM by Broadcom

https://wikidevi.com/wiki/Broadcom_NitroQAM

正交振幅調變（QAM，Quadrature Amplitude Modulation）@ 數位調變
https://en.wikipedia.org/wiki/Quadrature_amplitude_modulation

What is QAM?
https://blogs.arubanetworks.com/solutions/mobility/what-is-qam/

512-QAM vs 1024-QAM vs 2048-QAM vs 4096-QAM | Difference between 512-QAM, 1024-QAM, 2048-QAM, 4096-QAM
http://www.rfwireless-world.com/Terminology/Difference-between-512QAM-vs-1024QAM-vs-2048QAM-vs-4096QAM.html
512-QAM Modulation 1024-QAM Modulation

1024 QAM - Capability to transmit 10 bits per symbol using QAM;
prior Wi-Fi gens (11ac) were limited to 256 QAM, which can transmit up to 8 bit per symbol.

(越高的QAM對信號品質(信噪比)要求亦越高，也就是說越容易被干擾。)

當然... 要使用1024QAM就還需要1024QAM網卡...
@ 全球唯一一張支援1024-QAM的網卡 - ASUSPCE-AC88網卡
https://www.asus.com/tw/Networking/PCE-AC88/overview/
https://wikidevi.com/wiki/ASUS_PCE-AC88

PCE-AC88網卡無線晶片來自Broadcom BCM4366

AC5400 5G WiFi XStream Router Platform Diagram
https://www.broadcom.com/products/wireless/wireless-lan-infrastructure/bcm4366#overview

802.11ax 又稱為「高效率無線標準」
High-Efficiency Wireless (HEW)，旨在實現一項極具挑戰性的目標：
將使用者密集環境中的每位使用者平均傳輸率提升至 4 倍以上。
這項嶄新標準超越了 802.11ac 的原始連結速度，可於人潮洶湧的環境下運用多項機制，為更多使用者提供一致且穩定的資料流。

無庸置疑... 802.11ax還是要...
Backward compatiblewith 802.11a/b/n/ac

(1) 2, 5, 10MHz are Resource Units(RU) allocations –the BW is still 20,40,80

Wi-Fi傳輸速率示意圖 (色塊越大... 意味著傳輸速率越快!)

紫色色塊中的白色線條為11ax獨特有的...
OFDMA: (Orthogonal Frequency Division Multiple Access)

802.11ax新制式獨有的OFDMA: 頻率空間切小格(RU = Resource Unit)

OFDM: (Orthogonal Frequency Division Multiplexing)
OFDMA: (Orthogonal Frequency Division Multiple Access)

MU-MIMO: 空間域高架橋

Gigabit 等級 LTE by 4x4 MIMO

液晶聚合物最熱門應用：LCP天線
https://www.pixpo.net/others/0IYu51JR.html

(http://xqdoc.imedao.com/161fe6780ed20f583fd0a0d0.pdf)

MIMO–Multiple-Input-Multiple-Output:
A method for multiplying the capacity of a radio link using multiple transmit and receive antennas
MU-MIMO (Multiple User MIMO):
Capability of AP to simultaneously communicate with multiple clients in the same channel
while benefiting from the availability of additional antennas in the AP

MU-MIMO: