RB751U-2HnD

angboontiong · Wed Sep 28, 2011 3:14 pm

Hi...

is any one try this?
and what's that mean the antenna is the PIF antennas?

it's the pif antenna is the pifa antenna?

thanks

janisk · Fri Sep 30, 2011 1:08 pm

router has antennas in the case, but these are not the "usual" swivel. I like them, because result is - small white box without weird looking antenna sticking out.

there is a thread on the forum where someone made pictures of the board w/o case

angboontiong · Fri Sep 30, 2011 2:21 pm

router has antennas in the case, but these are not the "usual" swivel. I like them, because result is - small white box without weird looking antenna sticking out.

there is a thread on the forum where someone made pictures of the board w/o case

Hi janisk..
can we have option that, the casing can look like the ruckus or the ubnt unifi?

it will be more pretty for us to mount in the hotel.

appreciated it if mikrotik can consider on that.

Fri Sep 30, 2011 2:27 pm

what are you suggesting, that we copy the design of other companies

? or you have specific recommendation what you want to change in case design?

angboontiong · Fri Sep 30, 2011 3:05 pm

what are you suggesting, that we copy the design of other companies ? or you have specific recommendation what you want to change in case design?

Dear Normis..
if the cover can look like the smoke detector or some other else, it will look good.

the important thing is the AP image, as hotel guest like to see the thing which they will not see. ^_^

Fri Sep 30, 2011 3:22 pm

OK, I get your point!

By the way, you can partner with some MFM partner and develop your own case, for your specific needs.

laurinkus · Fri Oct 21, 2011 1:02 am

Why wireless uses so much of CPU even when no users are connected to the AP? What is behind unclassified?

angboontiong · Fri Oct 21, 2011 8:08 am

Why wireless uses so much of CPU even when no users are connected to the AP? What is behind unclassified?

That's is idle, you should check on the system > resources.

janisk · Fri Oct 21, 2011 9:02 am

also, what is the rest of wireless configuration, like ANI enabled.

laurinkus · Sun Oct 23, 2011 1:29 pm

That's is idle, you should check on the system > resources.

Do you really think I was asking why load is so "high" due to Idle ? Actually I was a bit surprised that AP in idle mode uses up to 18% of CPU. But that's probably because of ANI is enabled.

laurinkus · Sun Oct 23, 2011 1:42 pm

Does anyone else having problems with wireless on RB751U-2Hnd ?

I'm now testing this device in my home environment and facing some stability problems. Signal strength is good and stable, however TX CCQ drops below 10% from time to time, so does throughput. This is very annoying especially when watching IPTV over WLAN (~4.7Mbps of TCP traffic) and TX speed drops to 1-2Mbps. After some time it goes back to normal levels. Signal strength at the same time keeps nearly unchanged.

In a screenshot below you can see actual throughput when I tried to download file at a maximum speed from a local server using single HTTP connection.

Noise floor is ranging between -99 dBm and -115 dBm (depends on time of the day). Encryption - AES.

Here's an excerpt from my configuration:

[admin@MikroTik] /interface wireless> export 
# oct/23/2011 13:41:03 by RouterOS 5.7
#
<...>

/interface wireless
set 0 adaptive-noise-immunity=ap-and-client-mode allow-sharedkey=no antenna-gain=2 antenna-mode=ant-a area="" arp=enabled band=2ghz-b/g/n basic-rates-a/g=6Mbps basic-rates-b=1Mbps \
    bridge-mode=enabled channel-width=20/40mhz-ht-below compression=no country=lithuania default-ap-tx-limit=0 default-authentication=yes default-client-tx-limit=0 \
    default-forwarding=yes dfs-mode=none disable-running-check=no disabled=no disconnect-timeout=3s distance=indoors frame-lifetime=0 frequency=2412 frequency-mode=regulatory-domain \
    frequency-offset=0 hide-ssid=no ht-ampdu-priorities=0 ht-amsdu-limit=8192 ht-amsdu-threshold=8192 ht-basic-mcs=mcs-0,mcs-1,mcs-2,mcs-3,mcs-4,mcs-5,mcs-6,mcs-7 ht-guard-interval=\
    any ht-rxchains=0,1 ht-supported-mcs=\
    mcs-0,mcs-1,mcs-2,mcs-3,mcs-4,mcs-5,mcs-6,mcs-7,mcs-8,mcs-9,mcs-10,mcs-11,mcs-12,mcs-13,mcs-14,mcs-15,mcs-16,mcs-17,mcs-18,mcs-19,mcs-20,mcs-21,mcs-22,mcs-23 ht-txchains=0,1 \
    hw-fragmentation-threshold=disabled hw-protection-mode=none hw-protection-threshold=0 hw-retries=7 l2mtu=2290 mac-address=00:0C:42:E2:24:44 max-station-count=2007 mode=ap-bridge \
    mtu=1500 name=wlan1 noise-floor-threshold=default nv2-cell-radius=30 nv2-noise-floor-offset=default nv2-preshared-key="" nv2-qos=default nv2-queue-count=2 nv2-security=disabled \
    on-fail-retry-time=100ms periodic-calibration=default periodic-calibration-interval=60 preamble-mode=both proprietary-extensions=post-2.9.25 radio-name=000C42E22444 \
    rate-selection=advanced rate-set=default scan-list=default security-profile=testprofile ssid=20A station-bridge-clone-mac=00:00:00:00:00:00 supported-rates-a/g=\
    6Mbps,9Mbps,12Mbps,18Mbps,24Mbps,36Mbps,48Mbps,54Mbps supported-rates-b=1Mbps,2Mbps,5.5Mbps,11Mbps tdma-period-size=2 tx-power-mode=default update-stats-interval=disabled \
    wds-cost-range=50-150 wds-default-bridge=none wds-default-cost=100 wds-ignore-ssid=no wds-mode=disabled wireless-protocol=unspecified wmm-support=enabled
/interface wireless manual-tx-power-table
set wlan1 manual-tx-powers="1Mbps:17,2Mbps:17,5.5Mbps:17,11Mbps:17,6Mbps:17,9Mbps:17,12Mbps:17,18Mbps:17,24Mbps:17,36Mbps:17,48Mbps:17,54Mbps:17,HT20-0:17,HT20-1:17,HT20-2:17,HT20-3:1\
    7,HT20-4:17,HT20-5:17,HT20-6:17,HT20-7:17,HT40-0:17,HT40-1:17,HT40-2:17,HT40-3:17,HT40-4:17,HT40-5:17,HT40-6:17,HT40-7:17"
/interface wireless nstreme
set wlan1 disable-csma=no enable-nstreme=no enable-polling=yes framer-limit=3200 framer-policy=none
/interface wireless align
set active-mode=yes audio-max=-20 audio-min=-100 audio-monitor=00:00:00:00:00:00 filter-mac=00:00:00:00:00:00 frame-size=300 frames-per-second=25 receive-all=no ssid-all=no
/interface wireless sniffer
set channel-time=200ms file-limit=10 file-name="" memory-limit=10 multiple-channels=no only-headers=no receive-errors=no streaming-enabled=no streaming-max-rate=0 streaming-server=\
    0.0.0.0
/interface wireless snooper
set channel-time=200ms multiple-channels=yes receive-errors=no

Previously I used Linksys E1000 which was operating in the same channel. Had no issues at all. Both devices (Linksys and RB) have integrated antennas. Could it be the cause of a problem on RB? I don't have a MMCX antenna to test but if there is even a small probability that it will help I will definitely buy it.

DBob · Sun Oct 23, 2011 2:13 pm

I do have some problem as well, but different kind of.

laurinkus · Sun Oct 23, 2011 8:27 pm

In my case client's adapter is integrated Intel PRO Wireless 3945ABG (no 11n)

zervan · Tue Oct 25, 2011 1:01 pm

I've bought two pieces for testing (because CE certification is not finished) and I've spent few hours to test them yesterday... I must say I am disappointed

First I tried to set maximum value for L2MTU on ether1 (just to see if it works) and it stopped to work at all when there was a cable connected to any of ether ports during booting. Well, after upgrade to 5.8-beta it is fixed, so this is not what bother me.

I've connect configured RB751 to the same place where my old Canyon CNP-WF514N1 and started to measure performance between my laptop and testing point (not RB751) - it means I was testing "normal" 802.11n. I was testing RB751 in the role of NAT router and also AP. Both of them are slow - only 50 Mbps (at best, see later) throughput - old Canyon has 80 Mbps in the same situation. Why? First I though that's because the internal antenna is not so good, but it is so slow also when I am 1 meter near RB751 too.

Connection was very unstable in default state. I was "tweaking" many parameters and found out that using both chains causes instable connection. After disabling chain1, stability was much better, throughput as well (but only 50 Mbps). Setting HT Guard Interval to "long" improves stability too.

There is also very interesting behavior: when I disabled all firewall and NAT rules and connection tracking, CPU usage was lower, but throughput was lower too! If I enabled at least one firewall rule (doesn't matter which one) or connection tracking only, CPU usage was higher, but throughput too. Why?

Tue Oct 25, 2011 1:10 pm

what signals values you saw on chain0 and on chain1?
Try out the rate-selection=advanced and repeat the tests.
How do you test the throughput?

zervan · Tue Oct 25, 2011 2:03 pm

what signals values you saw on chain0 and on chain1?

cca -63 dBm on chain0 and -77 dBm on chain1 (chain1 is weaker all the time, but difference is bigger during test) with older 802.11 DraftN "integrated" card (capable of 150 Mbps - obviously not using chain1) - CCQ low (cca 50%) even with long HT Guard interval in the same room;
cca -59 dBm / -62 dBm using newer USB 802.11n (300 Mbps) card - CCQ good (cca 80%) with long HT Guard interval in the same room.

Try out the rate-selection=advanced and repeat the tests.

I've used advanced rate selection during my testing - connection speed was raising slower (so it was worse) with standard rate selection

How do you test the throughput?

using BTest (TCP connection, 60 KB packets) between my laptop on WiFi network and RB750G on my local network acting as BTest server only (this was not bottleneck, because if I connect by cable, speed is much higher, more than 100 Mbps)

Tue Oct 25, 2011 3:14 pm

please write to the support@mikrotik.com with support output file which is created when you are doing that test.
Have you tested with the UDP protocol?
You tested in NAT setup or simple routing, or bridging?

zervan · Wed Oct 26, 2011 1:22 am

please write to the support@mikrotik.com with support output file which is created when you are doing that test.

Well, I have made the supout files in 4 situations:

access point mode (just bridged ether1 + wlan),
routing mode (no firewall, no NAT, no connection tracking, only routing between wlan and ether2),
NAT mode (it was difficult to get supout file during testing - Mikrotik restarted itself, so I had to stop bandwidth test shortly after generating supout was launched)
and NAT mode using laptop with older 150 Mbps adapter.

First 3 were done between two computer - one connected by cable (point A), other by WiFi (point B). The fourth situation had laptop on point B and it seems that it is much less stable when using both chains. Once again - I get only cca 50 Mbps using RB751, but 80 - 90 Mbps using old Canyon WiFi router (on my laptop too).

Have you tested with the UDP protocol?

Yes, it was limited only by ethernet bandwidth (almost 100 Mbps).

You tested in NAT setup or simple routing, or bridging?

All of them - there is almost no difference, but routing was a little slower (I've mentioned that before) and NAT was less stable.

Wed Oct 26, 2011 9:47 am

Have you tested with the UDP protocol?
Yes, it was limited only by ethernet bandwidth (almost 100 Mbps).

This alone indicates that your TCP test method is flawed. Apprently you are not making enough TCP connections, or one of the test ends runs out of CPU resources to do the test.

zervan · Wed Oct 26, 2011 10:00 am

This alone indicates that your TCP test method is flawed. Apprently you are not making enough TCP connections, or one of the test ends runs out of CPU resources to do the test.

When I set TCP packet size to 60 kB, there was no (or just a little) difference between one connection and two connections. UDP throughput is higher because there is no control mechanism and TCP is degraded by low link quality. CPU resources on end-points should not be a problem (one of them is Intel G620, other Intel E8200), because if I measure TCP throughput using gigabit cable between end-points, it is much higher than 100 Mbps.

Nevertheless, it is all irrelevant, because if I use old WiFi router, throughput is much higher in exactly the same situation.

Wed Oct 26, 2011 10:02 am

but why is this happening?

cca -63 dBm on chain0 and -77 dBm on chain1 (chain1 is weaker all the time, but difference is bigger during test)

are you sure your power amplifier is not damaged? the chain power levels should not be that different.

zervan · Wed Oct 26, 2011 10:24 am

are you sure your power amplifier is not damaged? the chain power levels should not be that different.

I'm not sure about that - I could use stronger 24 V later today, but I think it should not be a problem, because the big difference between chains is appearing only when I use an older 802.11 DraftN "integrated" card (capable of 150 Mbps). If I use newer USB 300 Mbps card on the same laptop, there is only a little difference.

Sometimes I saw a weak value on chain2 as well for a short time - what's that? Empty external antenna socket?

I have two RB751U units - one of them is absolutely free to re-configure. You may send me any saved configuration "as simple as it can be" to eliminate some settings I've used that may lower performance and I can test it again with them.

laurinkus · Sat Oct 29, 2011 1:45 pm

So any ideas why throughput is so unstable?

Advanced rate selection is set, both chains are enabled, signal level is stable on both chains. Distance 5 meters, indoor environment.

Throughput pattern keeps repeating over time:

zervan · Sat Nov 05, 2011 9:39 am

I've realized that the "low speed issue" with 802.11n compared to common WiFi routers is not related to RB751 only, but it is practically the same on RB433 as well (I've made some testing). More general discussion about that is here: http://forum.mikrotik.com/viewtopic.php?f=7&t=35767

imaljko4 · Tue Apr 02, 2013 4:09 am

Hi janisk..
can we have option that, the casing can look like the ruckus or the ubnt unifi?

it will be more pretty for us to mount in the hotel.

appreciated it if mikrotik can consider on that.

Yes I agree, we also need that kind of look for the Hotel.

RB751U-2HnD

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