high speed wifi module (non-USB) ?

[morison20]

Dear all,
Is there any high speed wifi module for Raspberry pi?

I am planning to use raspberry pi as a custom routing device. However, The current method of using wifi is through USB dongles which is limited by the USB speed.

Any suggestion?

[SirLagz]

My suggestion ? Don't use the Pi.
There are only 2 non-USB interfaces on the Pi, and neither of them will work with a WiFi adapter.

[trouch]

There are only 2 non-USB interfaces on the Pi, and neither of them will work with a WiFi adapter.

Actually you can use any wifi arduino shield or any wifi module with SPI
But high speed... quite hard on raspberry pi

[SirLagz]

There are only 2 non-USB interfaces on the Pi, and neither of them will work with a WiFi adapter.

Actually you can use any wifi arduino shield or any wifi module with SPI
But high speed... quite hard on raspberry pi

Sorry, should have specified 2 non-USB high speed interfaces.
I agree, it's possible to use a wifi module with SPI though.

Best bet ? use a USB wifi stick. I'm using one as a router and it's getting decent throughput.

[jnihil]

WiFi is half-duplex, so your throughput will suffer no matter how fast your 802.11n adapter is. I think the Pi's interfaces are USB 2.0 from memory, so if you attach a Gigabit Ethernet USB adapter you should be able to reach 250Mbps or so. I have an ASIX chip-based GbE USB interface I could try out on the Pi if anyone is interested. I remember getting around 230-280Mbps over that adapter on a 1st-gen Intel ATOM netbook running the 2.6 kernel.

[SirLagz]

It's not the ddapter's speed that will be the bottleneck
It's the Pi itself, and its inefficient USB stack.

Though since you already have a gigabit ethernet USB stick, why not try it out and see how fast you can get it ?

[jbeale]

... you should be able to reach 250Mbps or so.

Didn't realize that kind of data rate was ever achieved via USB2.0, on any system. I can pretty much guarantee you won't see that on the Pi, at any rate.

[jnihil]

You got me curious about the Pi's throughput, and I wanted to check what throughput I saw on my USB GbE adaptor some years ago, so I connected it up to my Pi:

(dmesg from the pi)
[1252007.361766] usb 1-1.2.1: new high-speed USB device number 36 using dwc_otg
[1252007.475437] usb 1-1.2.1: New USB device found, idVendor=0b95, idProduct=1780
[1252007.475485] usb 1-1.2.1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[1252007.475505] usb 1-1.2.1: Product: GU-1000T
[1252007.475520] usb 1-1.2.1: Manufacturer: PLANEX COM. Inc.
[1252007.873476] asix 1-1.2.1:1.0: eth1: register 'asix' at usb-bcm2708_usb-1.2.1, ASIX AX88178 USB 2.0 Ethernet
[1252007.875912] usbcore: registered new interface driver asix
[1252011.803700] asix 1-1.2.1:1.0: eth1: link up, 1000Mbps, full-duplex, lpa 0xCDE1

Configured the interface on a separate subnet:

$ sudo ifconfig eth1 192.168.100.2/24

Then run a quick ethernet throughput test using UDP:

$ sudo iperf -c 192.168.100.1 -u -b300M
------------------------------------------------------------
[ 3] local 192.168.100.2 port 48522 connected with 192.168.100.1 port 5001
[ ID] Interval Transfer Bandwidth
[ 3] 0.0-10.0 sec 136 MBytes 114 Mbits/sec <----- huh? 114Mbps...

Only getting 114Mbps, however the Pi's CPU is pegged at 100%:

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
2583 root 20 0 19664 1144 960 S 97.4 0.2 0:04.79 iperf
2581 jnihil 20 0 5204 1404 1028 R 1.0 0.3 0:00.42 top

You're quite right. You won't get 250Mbps on a Pi.

I then moved the same USB NIC to a laptop with more cpu power and did the same test:

$ sudo iperf -c 192.168.100.1 -u -b300M
------------------------------------------------------------
[ 3] local 192.168.100.2 port 40604 connected with 192.168.100.1 port 5001
[ ID] Interval Transfer Bandwidth
[ 3] 0.0-10.0 sec 286 MBytes 240 Mbits/sec <----- Much better

This time we're not cpu-bound (Core2 Duo U7500 1.06GHz):

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
3534 root 20 0 96716 1108 928 S 35 0.1 0:02.53 iperf
3302 jnihil 20 0 31020 2264 1408 R 3 0.1 0:03.40 htop

So, using a GbE USB adaptor, you can get up to 240Mbps (one-way) using USB 2.0 if your CPU is fast enough.

I believe the Pi's CPU will be the bottleneck, not the actual USB port.

[EDIT] After reading SirLagz's comment on Pi's USB stack, it could just as well be the culprit for the high CPU usage, leading to a lower throughput. Anyway, I wouldn't expect anything near 114Mbps using TCP, but it's probably still better than using wireless.

Regards.

[cleverca22]

sounds like a decent job for oprofile!

[morison20]

Thank you very much for your replies. I was looking for a single board computer with bulit-in wifi and I kind of thought to use Raspberry Pi. However, based on the fact that it cannot achieve the high speed of 802.11n efficiently, I had to look for other options. And I had found 2 more options
1. Panda board which is more expensive and seemed a little complicated
http://www.digikey.com/product-highligh ... 686#tabs-2

2. UDOO, a new kickstarter project with built-in wifi + Arduino support. This one is interesting, however, it's delivery date is in September which is a little late for my project.
http://www.kickstarter.com/projects/435 ... ngle-board

Do you guys have any idea and/or experience on this? Any better option?

[jbeale]

If you need it cheap, and WiFi is the key element, you could try putting a distribution like OpenWRT on a WiFi router? There are a lot to choose from, see http://wiki.openwrt.org/toh/buyerguide

Be aware this route will not have as large a support community for any specific hardware, as R-Pi does.

[SirLagz]

There's quite a few low cost boards available nowadays

http://en.wikipedia.org/wiki/List_of_si ... _computers <-- here's a list of em for you to dig through