Wireless performance on the Axim

ftyczka · 05-30-04, 10:32 AM

I've read in the FAQ that the maximum thoughput you can get with the Axim is aourind 1 Mbit/s - is that really true ?
Does anyone know what the cause of this is ?

Levon · 05-30-04, 03:26 PM

well the wifi built in can go up to 11mbps, but because its a PDA, you cant get more than 2mbps, so the x30/3i can get max of 2mbps not 1.

its still hella good for a pda

ftyczka · 05-30-04, 05:29 PM

Okay... but where's the bottleneck ?

jackwesleyroper · 06-18-04, 11:24 AM

So why only 2mb max? What causes it to run at that speed when the network is 11mbps? Im guessing encryption, error checking, noise etc decreases the signal and speed?

Howard2k · 06-18-04, 11:51 AM

The most you'll sustain on an 11Mb/s wifi network is 5-6Mb/s. The bottleneck on the X5 is probably the CF and the overall system performance. Typically PDAs with built in wifi seem to see higher performance that those using CF.

Enctryption really has very little impact. Some - but not a lot. On that note though it's better to run 64 bit WEP than 128 bit WEP for that reason.

jackwesleyroper · 06-18-04, 04:09 PM

CF=Compact flash right, doubling as a wifi card?

So why only 5 or 6mbs limit?
I understand why in a normal wired network, but why which factors affect wireless?
The throughput of an axim is only 2mb/s, why is it not 5 or 6mbs? Power problems? That would surely render PDAs with 802.11g cards useless (for now). Are they avaliable or are there any plans for 'g' super speed pdas?

OK thats a lot of questions, but hope you can help in my quest for knowledge!

Cheers
Jack

Howard2k · 06-18-04, 04:53 PM

Correct. In the current generation there is no use for an 802.11g network card if the objective is improvement in PDA network performance alone. There are other reasons to use one though. Linksys have announced that theirs is coming soon.

Think of standard 10Mb/s Ethernet. It's a shared (non-switched) medium and has to put in mechanisms such as CSMA/CD to ensure that two devices don't transmit at the same time (well, to handle the problem when this DOES occur). Wif is also a shared medium. Pretend that three people are in a room. Only one person can talk at a time, you can't have all three people talking.

This reduces the overall "talk time" in the room.

That's the gist of it. For wifi it's collision avoidance (and a shared medium) that gets you only 5-6Mb/s from the 11Mb/s of "air space".

For the actual specific throughput on the PPC I'd be interested to see some tests on the X30. See if the new processors have increased the throughput at all.

jackwesleyroper · 06-18-04, 06:41 PM

What sort of things hardware wise restrict the throughput of the axim? Im thinking heat would be a problem running it at higher power levels, due to more powerful processors. (a super cooled axim maybe?!)

Would a normal laptop wireless card produce 5-6mb/s throughput? If so, why so much more than the axim?

In other words, why does throughput depend on the device and not the network factors like CSMA/CD that reduce speeds?

Also, if running a mixed mode 802.11g router, i hear throughput is around 20mbs. Would the throughput of the axim increase relative to the network speed increase, seeing as it is working at a higher level 'b' speed?

I'm also conused about CF, does this refer to the network card inside a PDA? Is it removable/replaceable? I understand you can get sd cards with built in wireless receivers - is this the same concept but just with the compact flash format of cards?

Interesting.

Howard2k · 06-18-04, 09:40 PM

CF - Compact Flash. The little insertable cards.

802.11g mixed mode does decrease performance but will not result in a net gain on the Axim. In fact turning on the Axim will possibly decrease the overall throughput of the 802.11g network.

I believe the issue is not heat, it's just I/O limitations. There HAVE been improvements though in the PXA270 from what I hear.

Yep - in a laptop it has the processing power and bus speeds to drive 5-6Mb/s without a hitch. You'll get more.

CSAM/CA (CSMA/CD on Ethernet, CSMA/CA on Wifi) will reduce the speed to 5-6Mb/s. The Axim limitations reduce it further to 1-2Mb/s.

Sorry for the short reply - have to catch a train.

HighTymes · 06-19-04, 12:18 AM

With the new betaplayer you can benchmark your data rate transfer. I selected a video file from my network and benchmarked it and got a 3.2Mbit/sec transfer rate. This is the fastest it will ever go or at least it looks that way so far with all the files i have tested it on.

To benchmark your data rate transfer, disable video and audio once you select a file and then benchmark it. With my SD card i got 17.7Mbit/sec. I got 340Mbit/sec through my RAM. My BIS can transfer 45.3Mbit/sec :)

I am curious to see what you get Howard with SD/CF, RAM, BIS and Wifi.

06-19-04, 03:49 AM

i think these are very good results. especially the SD card controller (probably the PXA270) which is way above i ever saw.

my e800 results:
WiFi 2.7Mbit/sec
SD 7.1Mbit/sec (TwinMOS 256MB)
CF 8.1Mbit/sec (PQI 512MB)
RAM 267.9Mbit/sec

Howard2k · 06-19-04, 01:02 PM

Cool, do you have a link?

HighTymes · 06-19-04, 03:03 PM

http://beta.topcat.hu/

Download betaplayer and the 320x240 matrix trailer

jackwesleyroper · 06-20-04, 05:58 PM

Why would some axims be able to reach levels of throughput that you quote above, when overs report just over 1mb/s, if an increase in network speed does not increase the throughput?

HighTymes · 06-20-04, 06:57 PM

the network throughput might differ on the wireless routter you have even if it says it has the same.