Wi-Fi 6 (802.11ax): 5 Things to Know

Wi-Fi最初是1x1 - 一个单一流，具有单个客户端与路由器交谈 - 但它已进化为8x8 MIMO（多输入/多个输出）解决方案，其中多个客户端同时与路由器交谈。目前的Wi-Fi标准，802.11ac(nowcalled Wi‑Fi 5），在2013年底完全发布，它在家庭环境中工作得很好。但与以前的Wi-Fi标准一样，当房屋中可能有50个节点时，它可能会达到2022左右的限制Organisation for Economic Co-operation and Development（经合组织）。

802.11ax(nowcalled Wi‑Fi 6）是下一个进化IEEE 802.11 Wi-Fi standardand will become prevalent in very dense environments, such as urban apartment complexes, college campuses, concert venues, or sports stadiums, where many clients will access the internet over Wi‑Fi. The IEEE standard currently is in development and expected to be publicly released in 2019.

Let's take a look at five key things you need to know about 802.11ax (Wi‑Fi 6) and the next generation of Wi‑Fi.

＃1：802.11ac（Wi-Fi 5）和802.11ax（Wi-Fi 6）之间的关键差异是什么？

#2: Wi‑Fi 5 (802.11ac) promises 6.9 Gbps but public Wi-Fi doesn't attain these speeds. Will Wi‑Fi 6 (802.11ax) remedy this problem?

6.9 Gbps just isn't possible in a home or public Wi-Fi network. We will never see the theoretical speeds listed on the box of a router on the shelves at Best Buy, Walmart or other big-box stores.

家中最限制的因素是来自互联网提供商的连接 - 进入家庭的互联网接入。如果路由器可以支持1.6 Gbps但与家庭的连接只有100 Mbps，则客户端将永远不会意识到从广域网（WAN）下载更高的速度。

The data stream into a home and the access point will establish the initial internet bandwidth benchmark. From there, other factors can slow the network speed:

• Distance between the client and the access point
• Interference from other clients on the same frequency
• Inherent Wi-Fi overhead for acknowledgments, transmit, and clear channel assessments

A Wi‑Fi 6 access point will provide a more efficient environment, mitigating the problems of Wi-Fi overhead — in other words, the fixed "cost" associated with the communication that isn’t a part of the data transmission. 11ax will attack the overhead differently, scheduling when a device operates and handling the information and clients more efficiently.

此外，advanced filtering techniques启用更好的共存和BandEdge性能。这有两种影响：

• Allows a broader spectrum to operate at full power
• Improves the quality of service and range in the once-limited bandedge channels

完全，提高效率和过滤将有助于802.11ax具有比11AC更快的速度。

#3: How does OFDMA create a more efficient payload delivery system?

802.11a高达802.11ac使用OFDM., or orthogonal frequency-division multiplexing, to deliver Wi-Fi data packets. Under OFDM, a device uses a fixed 20 MHz or 40 MHz of bandwidth to deliver the packets, regardless of whether it's transmitting video or just sending a simple text message over a Wi-Fi network.

Wi‑Fi 6 (802.11ax), however, usesOFDM.A, or orthogonal frequency-division multiple access, which allows resource units (RUs) that divide the bandwidth according to the needs of the client and provides multiple individuals the same user experience at faster speeds.

一个简单的类比使用卡车可以说明difference, as shown in the image below. Each truck is hauling a payload, or user data — one surfing the web, another uploading video from a soccer game and a third sending a text message, for instance. Under OFDM, a device had to use three trucks of the same size to send the data, regardless of how empty or full each truck was. In other words, OFDM inefficiently uses the bandwidth, leaving a lot of empty space. OFDMA, in contrast, allows a device to fill an entire truck with RUs (i.e., data) — a payload delivery model that uses the bandwidth much more efficiently.

＃4：Wi-Fi 6（802.11AX）支持1024 QAM。这种更高调制方案的影响是什么？

With 1024 QAM modulation, there are more bits per symbol — 10 bits per symbol versus 8 bits in 256 QAM. More bits equals more data, and the payload delivery of data is more efficient — like having a bigger truck.

At the same time, OFDMA decreases the spaces between the subcarriers, packing even more resource units into the truck, so to speak.

但随着数据速率的增加，error vector magnitude(EVM) on the RF front-end becomes paramount. With 1024 subcarriers in Wi‑Fi 6 (802.11ax), theconstellationis flooded and so dense that the system must distinguish one of the points from another. It takes a very sophisticated system to decode (or demodulate) these constellation points, and it requires devices to have better EVM.

Wi‑Fi 5 (802.11ac) requires -35 dB PA EVM, while Wi‑Fi 6 (11ax) requires -47 dB PA EVM. Higher modulation schemes require better EVM so that a device can attain the higher efficiencies of the data packet.

#5: What are the differences for Wi‑Fi 6 for a handset or other client versus access points?

As already said, Wi‑Fi 6 (802.11ax) pushes the EVM requirements down to -47 dB, but access points and clients still have to meet the same spec. There’s no difference.

Power levels can be very different, though. Access points orcustomer premises equipment (CPE)typically operate at much higher power than a client — 24 dBm versus 14-20 dBm for a mobile handset. Ultimately, a lot more power means更多的热量必须消散如此，与移动解决方案相比，连接解决方​​案可能需要更严格的热需求。