No N speed on Raspberry Pi+OpenELEC

[sefsh]

I have the TP-Link WN725N connected directly to a Raspberry Pi Model B, running latest stable version of OpenELEC. It works out of the box regarding general connectivity. But it only gets a max speed of 54 Mbps. If I reconfigure the router for N connections only, the wifi doesn't get discovered at all by the Pi. The Pi gets its juice from a 2.4A power supply.

[sefsh]

Others experiencing the same thing.

[sefsh]

I've also tried the new 3.95.1 and 3.95.2 beta builds. Same thing.

[EliaCereda]

I'm having a similar problem with Arch Linux, using a kernel that I compiled myself from the linux-raspberrypi-latest package in Arch's repositories. The driver I'm using is the one that's contained in the mainline kernel. This is the uname:

Linux raspberrypi 3.13.5-1-ARCH #1 PREEMPT Sun Mar 2 13:42:54 MST 2014 armv6l GNU/Linux

This is iwconfig's report, it seems to say that N is working:

wlan0     IEEE 802.11bgn  ESSID:"***********"  Nickname:"<WIFI@REALTEK>"
          Mode:Managed  Frequency:2.437 GHz  Access Point: **:**:**:**:**:**   
          Bit Rate:150 Mb/s   Sensitivity:0/0  
          Retry:off   RTS thr:off   Fragment thr:off
          Power Management:off
          Link Quality:0  Signal level:0  Noise level:0
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:0   Missed beacon:0

But if I run iperf I only get about 30Mb/s with the Pi within 2m of the router.

Unlike @yusf, though, if I disable B and G on my router the Pi connects just fine (it still doesn't use the full bandwidth but at least it connects).

[MrEngman]

You are using a Raspberry Pi! What speed do you expect?

You are connected at 150Mb/s it's just that the Pi is incapable of transferring anywhere near the full speed. 30Mb/s for a Pi is good. In normal use it's likely to be quite bit less.

[EliaCereda]

Why would it be incapable? iperf over Ethernet easily reaches 80-90Mb/s, Wi-Fi should do the same.

Raspberry is more than capable to reach those speeds, there's no hardware bottleneck that would prevent it. Plus, people on the forum thread that @yusf linked are able to reach 120Mb/s using Raspbian or Raspbmc, so this has to be a driver problem.

[lwfinger]

Yes, it probably is a driver problem; however, I do not know what it is. In addition, working on that driver is quite low on my TODO list. If you have patches that improve the performance, please submit them to me or to the staging project of the kernel.

You do need to be reasonable about your expectations. The RTL8188EU is a 1x1 (1 TX radio, 1 RX radio) device, and is limited to 150 Mbps; however, wifi is a half-duplex medium. Calculating the maximum throughput is complicated, but 50% of the raw rate is a good guess. From that, you need to subtract for interference from other devices on the channel, and numerous other effects.

[EliaCereda]

I'm not expecting anything spectacular, but other people have said they have reached 120Mb/s so it has to be possible. I'm setting up Raspbian on my Raspberry to check myself.

EDIT: as to fixing the driver myself, I don't know anything about driver programming, I wouldn't know where to start looking. I might give it a shot if I find some time to do it, but it's unlikely as I don't really need the extra bandwidth at the moment, I was just wondering why it doesn't go faster.

[sefsh]

@lwfinger Thanks for the input.

[miigotu]

I'm having much worse performance here on kernel 4.0.2 with OpenELEC on a Pi 2. Using 2.4GHz band, about 25ft from my EA6500 router I get 0.78Mb (yes bits) on 20Mhz channel width, and ~2Mb on 40Mhz channel width.

Seems to have major stability issues on 5GHz band?

I also had some serious issues with nfs over my local network until I turned on NO ACK in WMM settings of my router.

@lwfinger do you know which band and channel width is working well with this chipset and the current driver?