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Wifi speed?

Posted: Thu Feb 04, 2016 9:01 am
by magnusl
Hi!

I'm fairly new to the Raspberry Pi, using it for astronomy purposes (controlling my telescope). It is critical for me to have as fast wifi connection as possible from the Pi to my LAN. Right now I have a wifi dongle, according to lsusb it is Ralink Technology, Corp. RT5370 Wireless Adapter. My problem is that the speed I get currently is too low. It's somewhere between 18 and 24 Mb/s. Anyone knows of a way to increase this? Do I need another dongle, or can I use another driver, or what?
(on the same location, my laptop has 54 Mb/s)

Magnus

Re: Wifi speed?

Posted: Thu Feb 04, 2016 9:23 am
by fruitoftheloom
magnusl wrote:Hi!

I'm fairly new to the Raspberry Pi, using it for astronomy purposes (controlling my telescope). It is critical for me to have as fast wifi connection as possible from the Pi to my LAN. Right now I have a wifi dongle, according to lsusb it is Ralink Technology, Corp. RT5370 Wireless Adapter. My problem is that the speed I get currently is too low. It's somewhere between 18 and 24 Mb/s. Anyone knows of a way to increase this? Do I need another dongle, or can I use another driver, or what?
(on the same location, my laptop has 54 Mb/s)

Magnus
The RT5370 is well supported out-of-the-box you should be able to achieve with USB 802.11n WiFi: 45 Mbits/sec (5.5 MB/sec) if got a strong signal from router !

How have you determined your performance figures ??

Re: Wifi speed?

Posted: Thu Feb 04, 2016 10:12 am
by gregeric
If there's a lot of metal around WiFi dongle (eg other USB cables in adjacent sockets) then its RF performance will be compromised (eg you'll see low signal strength in the output of iwconfig). Fit the dongle on the end of a short USB extension cable so it's in the open air and you may get nearer the 150Mbps it's capable of.

Re: Wifi speed?

Posted: Tue Feb 16, 2016 2:55 pm
by magnusl
Hi!

Now I've been experimenting a lot. I've upgraded my accesspoint, so my laptop consistently has 144 Mb/s in speed. I've upgraded the Pi to latest Raspian, and tried with various USB extension cables, so it is free of other cables and other stuff. However, not good results. At best, it is up to 34 Mb/s, and more often, something like 5-10 Mb/s. Again, at the same very location, my laptop can have 144 Mb/s.

Any ideas on how to increase my speed? As it is now, I need to have a cable - this low speed wifi is totally useless for my astro applications.

Any advice warmly welcome!

Magnus

Re: Wifi speed?

Posted: Tue Feb 16, 2016 3:21 pm
by Forrrge

Re: Wifi speed?

Posted: Tue Feb 16, 2016 3:27 pm
by texy
Wired ethernet is out of the question then?
Texy

Re: Wifi speed?

Posted: Tue Feb 16, 2016 3:31 pm
by Forrrge

Re: Wifi speed?

Posted: Tue Feb 16, 2016 5:53 pm
by pksato
How far the RPi is from the access point?
The further away, the antenna aperture should be bigger.
A passive parabolic reflector can improve antenna aperture.

Re: Wifi speed?

Posted: Tue Feb 16, 2016 6:13 pm
by ronnyvdbr
You could try to disable your wifi power management features, sometimes this seems to give trouble for some people.

For another model it's specified as:
To turn off powersave, add the following to /etc/modules, or create a file (8192cu.conf) in /etc/modprobe.d/ with the line(s):
# prevent power down of wireless when idle
options 8192cu rtw_power_mgnt=0 rtw_enusbss=0

Next reboot (or rmmod/insmod) it should disable the power management.

Don't know if it will fit for your wireless card however.

Re: Wifi speed?

Posted: Wed Feb 17, 2016 9:42 am
by magnusl
Hi!

Wired is what I need to do now, but having a cable run through a slightly open door and leaving it there the whole night is not exactly the elegance I was after....;)

As for distance, we are talking some 10-15 meters, but there us a wall between the AP and the Pi when it is outdoors, however, nothing brick or concrete, only wood and other less dense materials (that I don't know the english names for.....) and glass.

I'll have a look at the other suggestions and return.

Magnus

Re: Wifi speed?

Posted: Wed Feb 17, 2016 9:50 am
by stubright
I'm not sure where in the world you are but wouldn't something like this help.
http://www.amazon.co.uk/TP-LINK-PA411KI ... +powerline
Stu

Re: Wifi speed?

Posted: Wed Feb 17, 2016 9:54 am
by magnusl
But...second thoughts:

Part of the mystery here, is that even when I place my R-Pi directly beneath the AP (2 meters from it), the wifi speed is maybe 50 MB at best. Far from any 150 Mb. that this device SHOULD be able to produce. Right now, it sits there, nothing between the Pi and the AP, 2 meters apart, and iwconfig shows 21.7 Mb/s. My laptop, some 8 meters away, show 72 Mb/s.

So what's going on here? Is there no way to better measure, or influence, the wifi speed through software?

Magnus

Re: Wifi speed?

Posted: Wed Feb 17, 2016 10:43 am
by pksato
Hi Magnus,
The usb wifi adapter have a external antenna?
These small one not have a external antenna, only a low sensitive integrated antenna. Need to stay very near to router antenna to get high speed.
If have external antenna, replace it with high gain, >9dBi. Directional is best.
Popular DIY antenna is the biquad.

Re: Wifi speed?

Posted: Mon Feb 22, 2016 5:54 pm
by magnusl
Hi!

OK, now I got me one of these:
http://www.modmypi.com/raspberry-pi/acc ... 0wodqnIFIA

It should be able to produce 150 MB/s. And I have the R-Pi ow 2 m from the AP. But still get only 53 MB/s. THe AP is clearly capable of more, as my laptop currently scores 130 Mb/s. THis is as given by iwconfig in the terminal:
pi@raspberrypi:~ $ iwconfig
wlan0 IEEE 802.11bgn ESSID:"VISTA-UNIFI"
Mode:Managed Frequency:2.462 GHz Access Point: C2:9F:DB:2F:7C:0C
Bit Rate=52 Mb/s Tx-Power=20 dBm
Retry short limit:7 RTS thr:off Fragment thr:off
Power Management:off
Link Quality=61/70 Signal level=-49 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:3 Invalid misc:60 Missed beacon:0
The AP says this about the raspberry:
Overview
ESSID VISTA-UNIFI
Connected AP dc:9f:db:2e:7c:0c
Channel 11 (11ng)
Signal 99% (-39 dBm)
TX Rate 72.222M
RX Rate 1M
Power Save Not Enabled
Activity
Down Pkts/Bytes 388 / 75.7K
Up Pkts/Bytes 328 / 62.5K
So why is it not faster? There must be something limiting this in the R-Pi - somehow the device, or something is wrong?

And attaching the same dongle to my laptop, I get 130 Mb/s.... So the device is capable.

Magnus