802.11n WIFI speeds

Stephen Morris samorris at netspace.net.au
Tue Jan 5 21:42:24 UTC 2016


On 06/01/16 04:50, Rick Stevens wrote:
> On 01/04/2016 06:34 PM, Jack Craig wrote:
>> how due you calculate throughput? i have a wireless config for 54 
>> Mbit/sec
>> but never measured...
>>
>> On Mon, Jan 4, 2016 at 4:30 PM, Wolfgang S. Rupprecht
>> <wolfgang.rupprecht at gmail.com <mailto:wolfgang.rupprecht at gmail.com>> 
>> wrote:
>>
>>
>>     Does Fedora/Linux support the faster than 54 Mbit/sec 802.11n 
>> speeds?
>>
>>     My OpenWRT AP has a status page that claims that the 5 Ghz radio is
>>     configured for a 150 Mbits/sec 40Mhz (double-wide) channel. I'm only
>>     seeing a 54 Mbit/sec throughput over WIFI though.  (Over ethernet 
>> to the
>>     same router I'm seeing the expected 180 Mbits/sec to the internet.)
>>
>>     This is what lshw(1) has to say about the wifi card:
>>
>>                *-network
>>                      description: Wireless interface
>>                      product: RTL8821AE 802.11ac PCIe Wireless Network
>>     Adapter
>>                      vendor: Realtek Semiconductor Co., Ltd.
>>                      physical id: 0
>>                      bus info: pci at 0000:03:00.0
>>                      logical name: wlp3s0
>>                      version: 00
>>                      width: 64 bits
>>                      clock: 33MHz
>>                      capabilities: pm msi pciexpress bus_master cap_list
>>     ethernet physical wireless
>>                      configuration: broadcast=yes driver=rtl8821ae
>>     driverversion=4.2.8-300.fc23.x86_64 firmware=N/A ip=192.168.75.107
>>     latency=0 link=yes multicast=yes wireless=IEEE 802.11abgn
>>                      resources: irq:52 ioport:3000(size=256)
>>     memory:b2000000-b2003fff
>>
>>     Does this ring any bells?  I can easily believe that the faster 
>> speeds
>>     are proprietary extensions but figured I'd check.
>
> AFAIK, 802.11n has a theoretical limit of 160Mbps. However, that's over
> that full, 40MHz double-wide channel with no channel contention and no
> other radios active. The radio on your AP is shared among all users of
> the AP so you have to take that into account. The theoretical limits
> of the radio are probably only approached in a lab environment for any
> wifi technology. The real world is, well, different. :-)
>
> If you want higher speeds, then 802.11ac is a better route. Note that
> it only works over the 5GHz radio (not the 2.4GHz that 802.11n can
> use), so it doesn't have the range or "penetration power" (ability to
> go through walls, etc.) that the 2.4GHz band has. None the less, it is
> faster (theoretically over 8 times faster than 802.11n due to a number
> of additional things done in the protocol, muxing, antenna handling and
> session management).
Just one point on this, I have a Belkin 1750 ac modem/router that has 2 
usually used SSID's, one that runs only over the 2.4GHz band and one 
that runs over the 2.4GHz band and the 5GHz band as documented (I'm also 
being told that ac gets its faster throughput because it does use the 
2.4 GHz and 5GHz bands at the same time). The issue I have found is that 
with the 2.4GHz mode I lose about 200 KiloBytes/sec download over the 
802.11n modem/router I replaced, and, the mode that uses both bands 
doesn't change that but that mode is notoriously unreliable for playing 
online games. I'm also using a usb wireless card on my pc to get the ac 
compatibility, but I need to compile the driver every time the kernel 
changes because it has a chipset in it that is not supported by Fedora, 
and I'm told it never will be.
These are just things that need to be considered when evaluating whether 
or not to swap from 802.11n to 802.11ac, you may also want to consider 
whether or not you want/have a need to change to the 802.11 protocols 
beyond 802.11ac as well.

regards,
Steve

>
> As always, YMMV. I find 802.11n fine for what I need wifi for, although
> I do have 802.11ac available as well. If I need higher speed, my house
> is fully CAT6-ified with an Extreme Summit 400-48T 48-port switch in the
> middle, so I can "go copper" if I need higher speed (sorta gilding the
> lily since my Internet link is only 100Mbps upload (download is faster,
> but I do a lot of uploading due to my job).
> ----------------------------------------------------------------------
> - Rick Stevens, Systems Engineer, AllDigital ricks at alldigital.com -
> - AIM/Skype: therps2        ICQ: 226437340           Yahoo: origrps2 -
> -                                                                    -
> -       Blessed are the peacekeepers...for they shall be shot at     -
> -                 from both sides. --A.M. Greeley                    -
> ----------------------------------------------------------------------

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