Asus RT-AC51U Throughput?

[WhizzWr]

Hi AC51U owner, what kind of wireless throughput are you getting from this router?

I have 100Mbit/s WAN but when I tested the router with with Intel 7260N 2x2 (300 Mbps link speed) Laptop, the downlink throughput is capped at 82 Mbit/s, strangely uplink reaches 98 Mbit/s just fine. . Same goes with my wireless-AC Android phone (433 Mbps link speed), uplink is maxed, but it's getting 15-20 mbps lower than the actual WAN speed. Test is done in point blank range (ca 2 m laptop/phone <--> router)

Any pointer? CPU is on 40% or so during speed test, setting is left mostly as default. This is reproduceable with stock firmware and Padavan's build, both 5 Ghz and 2.4 Ghz given the same distance.

 

[wouterv]

A few thoughts, although I cannot find exact specs of the RT-AC51.
2.4 GHz seems to be max 300Mbps, pointing to two data streams of 150Mbps max in wireless n at 40MHz.
5 GHz seems to be max 433Mbps, pointing to one data stream in wireless ac at 80MHz.
The 300 and 433 count up to the advertised and rounded up 750Mbps.

2.4 GHz will only under ideal situations (in rural areas) keep up 40MHz, it will usually scale down to 20MHz, resulting in half of the maximum connection speed, so in practise 150Mbps.

The same is true for the 5GHz signal, I am not sure if the RT-AC51 does support the higher DFS channels, with a nearby neighbor router at 5GHz your router may not be able to keep up 80MHz and fall back to 40MHz, resulting about 200Mbps connection speed.

Maximum througput is in practice about half of the connection speed: with above in mind you may easily fall back to maximum throughputs of 75Mbps at 2.4GHz and 100 Mbps at 5GHz.

Be sure to use the best wireless channels for your location, a program called inSSIDer may help you.
Distance and free line of sight between the router and client is crucial, walls and objects will cause degraded wireless connections.
Also other electronics (bluetooth, microwaves, DECT telephones) or a bad power supply may degrade the wireless connection.

 

[WhizzWr]

A few thoughts, although I cannot find exact specs of the RT-AC51.
2.4 GHz seems to be max 300Mbps, pointing to two data streams of 150Mbps max in wireless n at 40MHz.
5 GHz seems to be max 433Mbps, pointing to one data stream in wireless ac at 80MHz.
The 300 and 433 count up to the advertised and rounded up 750Mbps.

2.4 GHz will only under ideal situations (in rural areas) keep up 40MHz, it will usually scale down to 20MHz, resulting in half of the maximum connection speed, so in practise 150Mbps.

The same is true for the 5GHz signal, I am not sure if the RT-AC51 does support the higher DFS channels, with a nearby neighbor router at 5GHz your router may not be able to keep up 80MHz and fall back to 40MHz, resulting about 200Mbps connection speed.

Maximum througput is in practice about half of the connection speed: with above in mind you may easily fall back to maximum throughputs of 75Mbps at 2.4GHz and 100 Mbps at 5GHz.

Be sure to use the best wireless channels for your location, a program called inSSIDer may help you.
Distance and free line of sight between the router and client is crucial, walls and objects will cause degraded wireless connections.
Also other electronics (bluetooth, microwaves, DECT telephones) or a bad power supply may degrade the wireless connection.

Thanks for the reply. Like I said I tested this on very short range, so interference from other AP/client are mostly out of the equations (my AP signals would always be higher, RSSI around -31 dbm).

Most of your assessment is correct except AC51U only have 1x1 5Ghz antennae, so in 5Ghz N mode the speed is reduced to 150 Mbps max.
Meanwhile I found a discussion in other forum (it's non-English though) http://4pda.ru/forum/index.php?showtopic=712598&view=findpost&p=52808757 that clearly shows AC51U Wireless can go beyond 90 mbps just fine.

Still trying to figure out what's wrong with my downstream :/

 

[wouterv]

Most of your assessment is correct except AC51U only have 1x1 5Ghz antennae, so in 5Ghz N mode the speed is reduced to 150 Mbps max.

Right, but I wrote:

5 GHz seems to be max 433Mbps, pointing to one data stream in wireless ac at 80MHz.

Your assumptions about short range can be wrong.

• Did you check check the wireless spectrum of your neighborhood?
• Did you verify the actual channel bandwidth of your router?

Wireless network traffic is anyhow like driving on the highway, with no other traffic you can drive fast, with other traffic you will slowdown.

 

[WhizzWr]

Right, but I wrote:

5 GHz seems to be max 433Mbps, pointing to one data stream in wireless ac at 80MHz.

Your assumptions about short range can be wrong.

• Did you check check the wireless spectrum of your neighborhood?
• Did you verify the actual channel bandwidth of your router?

Wireless network traffic is anyhow like driving on the highway, with no other traffic you can drive fast, with other traffic you will slowdown.

Hmm yeah should have written this in the first post, but the standard procedure is done, but I'll elaborate for clarity.

1. There are literally two 5 GHz AP near me, both of them in channel 112, I'm using channel 40. The 2.4 Ghz is crowded but I make sure to move my 2.4 GHz to least occupied channel, although as far as I observed the speed in 5 and 2.4 Ghz is the same given short enough distance, let's assume I'll use 5 GHz to eliminate "crowded neighborhood/interference/microwave/bluetooth" factor.

2. The router reports this information (I think this will answer your second question)

MAC (AP Main) : 70:XX:CD:B5:FB:6C
Operation Mode : AP
Channel Main : 40

AP Main Stations List
----------------------------------------
MAC PhyMode BW MCS SGI LDPC STBC TRate RSSI PSM Connect Time
90:XXC4:C8:F5:79 VHT 80M 9 YES NO NO 433M -44 NO 00:12:55
A4:XX:94:A9:57:31 HTMIX 40M 7 YES NO NO 150M -48 NO 00:12:13

The first device is my phone, the second device is laptop, 4 meter away from router, direct sight no obstructions. I don't have 5 GHz DECT cordless phone or anything that might interfere.

Speed by Cable

Speed 2.4 GHz

Speed 5 Ghz

It's evident that uplink is doing fine but I'm losing~8-10 mbps downlink speed, not that much but I really would like to know why my router cannot sustain my WAN bandwidth.. while in the linked discussion above, several people prove their hardware can.

 

[WhizzWr]

Update: reflashed to stock FW. Done some speed test, turns out my AC51U can reach 90Mbps just fine within ideal condition+stock FW. Something in Padavan capped the downlink to 82 Mbps, but okay doesn't matter too much to me.