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新路由器是否真正表现更好?第二部分

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222ba 发表于 2014-1-22 00:32:41 | 显示全部楼层 |阅读模式

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原文:http://www.smallnetbuilder.com/w ... -performance-part-2
WILL A NEW ROUTER REALLY IMPROVE PERFORMANCE? PART 2

Last time, I promised to show the results of one more experiment aimed at showing what improvements (or not) moving up from "legacy" (A/B/G) and N gear to AC might bring.



The previous experiments involved using different wireless adapters, which introduces another source of variation into the results. But what if we could use the same router and adapter? Turns out I could do just that by using the wireless mode controls on the ASUS RT-AC66U router and ASUS USB-AC56 adapter.

I ran four sets of tests with the router and client configured to represent the following scenarios:

  • AC1750 router connected to AC1200 client
    • Represents the scenario that many users are considering upgrading to
    • Router and adapter wireless mode set to auto.
    • 5 GHz maximum link rate: 867 Mbps
    • 2.4 GHz maximum link rate: 130 Mbps (20 MHz mode)
  • AC1750 router connected to N600 client
    • Represents the common scenario where only the router is upgraded
    • Router wireless mode set to auto. Adapter set to a/n or g/n mode
    • 5 GHz maximum link rate: 300 Mbps
    • 2.4 GHz maximum link rate: 130 Mbps (20 MHz mode)
  • N900 router connected to N600 client
    • Represents the typical current configuration for many users
    • Router wireless mode set to N+AC, bandwidth to 40 MHz. Adapter set to a/n or g/n mode
    • 5 GHz maximum link rate: 300 Mbps
    • 2.4 GHz maximum link rate: 130 Mbps (20 MHz mode)
  • A/G54 router connected to N600 client
    • Represents a configuration where a user has perhaps never upgraded his / her router, but has purchased a new wireless computer
    • Router wireless mode set to Legacy. Adapter set to a/n or g/n mode
    • 5 GHz maximum link rate: 54 Mbps
    • 2.4 GHz maximum link rate: 54 Mbps

What I would expect to see is different maximum throughput with low attenuation values (strong signals) for different modes. But I also would expect the same or very similar range as signal levels decline. Remember from the previous article that maximum range is indicated by the point where throughput falls to 0 Mbps. The longer throughput stays at its highest level, the better the range performance of the combination of router and client.

I'm going to look at 5 GHz results, because that is the only band that benefits from the additional bandwidth that AC can provide. The 2.4 GHz band in an AC router is the same at that in an N router. (I'm ignoring AC1900 for the moment, which I recommend you also do.)

The downlink plot generally matches expectations. The N client provides no benefit for a "Legacy" router; throughput is limited by the slowest device, which is the router in this case.

Stepping up to an N router allows the client's N link rates to come into play. This boosts best case throughput by almost 700%! What I didn't expect to see was higher throughput at the lower signal levels. From 30 to 42 dB throughput is about 2X "Legacy" throughput. This could provide more reliable or usable connections in areas that previously didn't have them. But the largest performance gain is still where signals are strong to moderate.

ASUS RT-AC66U / USB-AC56 wireless mode comparison - 5 GHz downlink

Note that moving from an N to AC router doesn't affect performance significantly. That's because the N client is now the limiting factor.

The top trace in the plot shows significant improvement in maximum throughput as I would expect. But it also surprisingly shows improved effective range, both from higher throughput at lower signal levels and almost an order of magnitude higher throughput at the 45 dB maxium test point. This means that if throughput continued to decline at the same rate, using AC mode could boost range by 6 dB or more. It's impossible to say what that represents in distance or area. But it is a significant gain that would be noticeable in real-world use.

Ah, but wireless giveth, it also can taketh away. The 5 GHz uplink plot is so different, you might think it was produced by a different router. First, note that all strong signal throughput (left side of plot) is lower than downlink, except for the bottom "Legacy" trace. But even worse, the full AC trace is downright awful. Best case throughput is about 100 Mbps lower than downlink. And that glitch at 24 dB was repeated in a second test run.

ASUS RT-AC66U / USB-AC56 wireless mode comparison - 5 GHz uplink

Even worse is that from 39 dB on, throughput is below what I got with N operation. These are clearly things that you would notice in real-world use.

I used a slightly different method to compare 2.4 GHz modes. This time, instead of keeping the client in N mode, I changed it to match the router's mode. So the 2.4 GHz downlink plot below shows what using "matched" client and router can do.

Lowest throughput is once again in Legacy mode, with link rate capped at 54 Mbps. But I was surprised to see higher maximum throughput with the router and client explicitly forced to N link rates, vs. the default Auto setting. Theoretically, since the maximum link rates for AC devices in the 2.4 GHz band are N link rates, I would expect both curves to be essentially the same.

But it appears for this particular combination of router and client, forcing N mode results in higher maximum throughput. I suspect this is due to implementation differences in the Broadcom-based router and Realtek based client's wireless drivers.

ASUS RT-AC66U / USB-AC56 wireless mode comparison - 2.4 GHz downlink

My expectation of similar maximum range seems to be upheld by the plot. Once signal levels drop at 45 dB and higher attenuation, the throughput of all three modes tracks pretty closely.

The 2.4 GHz uplink plot is a better illustration of how wireless class affects performance. Both N andAuto mode traces track very closely with strong to moderate signal levels, then join the Legacy trace at lower signal levels.

ASUS RT-AC66U / USB-AC56 wireless mode comparison - 2.4 GHz uplinkClosing Thoughts

There are key takeaways from these results that you should keep repeating to yourself next time you are tempted by the next shiny router dangled in front of you.

1. Changing wireless class on both router and client is required to get the largest performance improvement.
You might even see greater coverage in 5 GHz from moving to AC. This comes more from starting with more throughput to lose than through any router design magic.
2. Most performance improvement comes in the form of higher throughput at strong to moderate signal levels. At low signal levels, devices fall back to essentially acting as N, then A/B class devices.
3. If you don't change wireless class on both router and client, you are depending on router design differences to provide improved performance.

The last point is definitely one to ponder. SmallNetBuilder provides the best data for comparing relativerouter performance you'll find anywhere. But these experiements show that even with a very limited mix of routers and clients and even with products from the same manufacturer, your mileage may vary...a lot!

The folks trying to get you to buy new stuff want you to forget that 802.11ac is still in early days. But these very simple, limited, tests show that if you want performance stability and predictability, you're better off sticking with N gear. N has had years to work out interoperability quirks and will provide much more predictable performance.

AC is still on a steep learning curve and will continue to give people fits with odd behavior, unexpectedly low throughput and other treats. And more fun is just around the corner. All the brouhaha around AC1900 will be quickly forgotten as companies proudly trot out 4x4 AC and MU-MIMO stuff for you to drool over at CES in January. If you think getting all the advertised performance out of AC is difficult now, just you wait!


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无线爱好 发表于 2014-3-29 13:25:34 | 显示全部楼层
我用猎豹翻译了,如下
http://www.smallnetbuilder.com/w ... -performance-part-2将新的路由器是提高性能?最后的2部分,我答应过一个实验,旨在展示如何改善结果(或不)从“遗产”(a / b / g)和N档交流会。以前的实验涉及使用不同的无线适配器,它引入了另一个源的变化的结果。但如果我们能用同样的路由器和适配器吗?原来我能做的只是通过无线方式控制在华硕华硕usb-ac56 rt-ac66u路由器和适配器。我跑了四套的路由器和客户端配置为代表的以下情景测试:ac1750路由器连接到ac1200客户代表的情况下,许多用户考虑升级到无线路由器和适配器模式设置为自动。5 GHz的最大连接速率:867 Mbps的2.4 GHz的最大连接速率:130 Mbps(20 MHz模式)ac1750路由器连接到客户代表N600普遍的情况下,只有路由器升级路由器的无线模式设置为自动。适配器设置一个/ N和G / N模式的5 GHz的最大连接速率:300 Mbps的2.4 GHz的最大连接速率:130 Mbps(20 MHz的模式)的N900路由器连接到客户代表N600许多用户路由器的无线模式设置为n +交流典型的当前配置,带宽为40兆赫。适配器设置一个/ N和G / N模式的5 GHz的最大连接速率:300 Mbps的2.4 GHz的最大连接速率:130 Mbps(20 MHz模式)/ G54路由器连接到客户端的配置在N600代表用户也许没有提升他/她的路由器,但已购买了新的电脑无线路由器的无线模式设置为Legacy。适配器设置一个/ N和G / N模式的5 GHz的最大连接速率:54 Mbps的2.4 GHz的最大连接速率:54 Mbps我所希望看到的是不同的最大吞吐量和低的衰减值(强信号)的不同模式。但我也希望相同或非常相似的范围内的信号水平下降。记住,最大范围的吞吐量下降到0 Mbps的点表示,以往的文章。较长的吞吐量保持在最高水平,更好的路由器和客户端相结合的范围内的性能。我要去看看5 GHz的结果,因为这是从额外的带宽,可以提供好处,唯一的乐队。在交流路由器2.4 GHz频带是在N路由器一样。(我暂时忽略,1900,我建议你也这样做。)下行情节一般比赛的期望。N客户端提供不利于“遗产”路由器;吞吐量是由慢设备有限公司,它是在这种情况下,路由器。加紧N路由器允许客户端的连接率来发挥。这提高了最好的情况下的吞吐量接近700%!我不希望看到在低信号水平更高的吞吐量。从30到42分贝的吞吐量是大约2倍的“传统”的吞吐量。这可以提供更可靠的或可用的连接的地区,以前没有的。但最大的性能增益,仍然是在信号是强大的适度。华硕rt-ac66u / usb-ac56无线模式比较- 5 GHz的下行链路的注意,从N AC路由器不显著地影响性能。这是因为,客户现在的限制因素。在情节上的痕迹显示最大的吞吐量的显着改善,我希望。但它也出人意料地显示出改进的有效范围,从更高的吞吐量,较低的信号电平,几乎一个数量级更高的吞吐量在45 dB最大测试点。这意味着,如果吞吐量继续以相同的速率下降,使用交流模式可以由6分贝或以上升压范围。很难说什么表示距离或地区。但这是一个明显的增益,在现实世界中使用的是明显的。啊,但无线所赐,它也夺去。5 GHz的上行链路的情节是如此的不同,你可能会认为这是由不同的路由器产生。第一,注意所有的强信号的吞吐量(图左)低于下行,除了底部的“传统”的痕迹。但更糟糕的是,完整的AC微量简直是可怕的。最好的情况是100 Mbps的吞吐量低于下行。这问题在24分贝是在第二次测试运行重复。华硕rt-ac66u / usb-ac56无线模式比较- 5 GHz的上行链路更糟糕的是,从39 dB,吞吐量低于我与操作。这些都是明确的事情,你将在现实世界中使用的通知。我用一个稍微不同的方法为2.4 GHz的模式比较。这一次,而不是让客户在N模式,我改变了它与路由器的方式。所以2.4 GHz的下行链路的图显示出使用“匹配”客户端和路由器可以做。最低吞吐量再次在传统模式下,与链路速率为54 Mbps。但我很惊讶地看到更高的最大吞吐量与路由器与客户明确
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