modified on 16 June 2009 at 17:16 ••• 14,674 views

SR71

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Contents

SR71-A miniPCI MIMO

Author: Skyhook 06 June 2009
Contents: Firt test of UBNT SR71-A MIMO radio module on RouterOS/Mikrotik board

Introduction

Starting from v4.0beta3, RouterOS support 802.11n draft wireless card.
To enable 802.11n support you need:

  • upgrade RouterOS to v4.0beta3 or above
  • upgrade RouterOS Licence Key to new format
  • upgrade Routerboard BIOS to the latest version (recommended 2.20 or newer)

Refer to RouterOS ducumentation for more detailed info.

RouterOS info about UBNT SR71-A:

[admin@MikroTik] /interface wireless> pr
Flags: X - disabled, R - running 
0  R name="wlan1" mtu=1500 mac-address=00:15:6D:84:06:66 arp=enabled interface-type=Atheros 11N 
     mode=ap-bridge ssid="test!" frequency=5180 band=5ghz-onlyn scan-list=default 
     antenna-mode=ant-a wds-mode=disabled wds-default-bridge=none wds-ignore-ssid=no 
     default-authentication=yes default-forwarding=yes default-ap-tx-limit=0 
     default-client-tx-limit=0 hide-ssid=no security-profile=default compression=no 

note: interface-type=Atheros 11N ;-)

[admin@MikroTik] /interface wireless info> pr
0 interface-type=Atheros AR5416 chip-info="mac:0x40/0x0, phy:0xb0, a5:0xc0, a2:0x0, eeprom:0x0" 
  pci-info="00:14.0" capabilities=tx-power-control,ack-timeout-control,virtual-ap,alignment-mode,
                                  scanning,nstreme,sniffing,ht40-a,ht40-g,wmm 
  default-periodic-calibration=enabled supported-bands=2ghz-b,5ghz,2ghz-g,5ghz-11n,2ghz-11n 
  2ghz-b-channels=2412:0,2417:0,2422:0,2427:0,2432:0,2437:0,2442:0,2447:0,2452:0,2457:0,2462:0 
  5ghz-channels=5180:0,5185:0,5190:0,5195:0,5200:0,5205:0,5210:0,5215:0,5220:0,5225:0,5230:0,
                5235:0,5240:0,5260:0,5265:0,5270:0,5275:0,5280:0,5285:0,5290:0,5295:0,5300:0,
                5305:0,5310:0,5315:0,5320:0,5745:0,5750:0,5755:0,5760:0,5765:0,5770:0,5775:0,
                5780:0,5785:0,5790:0,5795:0,5800:0,5805:0,5810:0,5815:0,5820:0,5825:0 
  2ghz-g-channels=2412:0,2417:0,2422:0,2427:0,2432:0,2437:0,2442:0,2447:0,2452:0,2457:0,2462:0 
  5ghz-11n-channels=5180:0,5185:0,5190:0,5195:0,5200:0,5205:0,5210:0,5215:0,5220:0,5225:0,5230:0,
                    5235:0,5240:0,5260:0,5265:0,5270:0,5275:0,5280:0,5285:0,5290:0,5295:0,5300:0,
                    5305:0,5310:0,5315:0,5320:0,5745:0,5750:0,5755:0,5760:0,5765:0,5770:0,5775:0,
                    5780:0,5785:0,5790:0,5795:0,5800:0,5805:0,5810:0,5815:0,5820:0,5825:0 
  2ghz-11n-channels=2412:0,2417:0,2422:0,2427:0,2432:0,2437:0,2442:0,2447:0,2452:0,2457:0,2462:0

Hardware setup

This test are performed between two indoor (about 5 m distance) devices with:

  • 1 x RB433AH
  • 1 x SR71-A miniPCI MIMO Radio Module
  • 3 x antenna omni 5dBi on MMCX pigtail


Basics 802.11n configuration options

I have tested SR71-A on 5 GHz band, 5180 MHz, starting from default configuration value and settign as below:

  • band: 5ghz-onlyN
  • frequency: 5180 MHz
  • ht-ampdu-priorities: 0
  • ht-guard-interval: any
  • ht-extension-channel: above-control
  • ht-txchains: 0-1-2 (all chains)
  • ht-rxchains: 0-1-2 (all chains)
  • tx-power: 5 dB, Card Rate (due to short distance, setup a low power to prevent radio saturation...)

More detail on some 802.11n configuration options

  • ht-ampdu-priorities (0,1,2,3,4,5,6,7 - any combination of these)
    A-MPDU (Aggregated Mac Protocol Data Unit) Frame Aggregation allows the transmissions of multiple ethernet frames to a single location as burst. Iin other word, this protocol allows several MAC-level service data units (MSDUs) to be aggregated into a single MPDU. Some study dimonstrate that A-MPDU aggregation allows to achieve a high channel utilization of 95% in the ideal case while without aggregation the channel utilization is limited by just 33%.
  • ht-extension-channel (above-control | below-control | disabled)
    The current 802.11n draft allow wireless channel bonding. There is one 20Mhz channel defined as the "control channel" while the "secondary channel" (or exended channel) can then be set to sit above or below the control channel. I recommends channel bonding be used in the 5GHz band due to the limited number of non-overlapping channels available in the 2.4GHz band (remeber: exended channel = base channel + 20 MHz).
    For more info visit 802.11n Channel Bonding
  • ht-rxchains/ht-txchains (0,1,2 - any combination of these)
    Which antenna connector to use for TX or RX. We can use one of these or combination of these . UBNT SR71-A support up to 3 MMCX antenna connectors and to use all antenna ht-tx/rx-chains need to be check 0,1 and 2 for max perfomances.

Test results

From a first test, the results are interesting, but can be emproved: over 82 MBits TCP throughput, over 211 MBits UDP throughput.


TCP throughput

Image:SR71-A_TCP_test.png

UDP throughput

Image:SR71-A_UDP_test.png

Retrieved from "http://wiki.ubnt.com/SR71"