I've cruised through several posts, but the best path and product is not clear to me...

I want to do wireless, and I see that installing a hub or "station" in the car is the way to go. Which is the easiest? Those who have done this - can you reply?

More details:
I want to sync with the unit in my car from my desk, which is typically about 500 feet away.

Ideally, I'd also llike to be able to get file-level access through bluetooth (transfer a song to/from my iPaq 3870). I know this is more tricky than just the wireless platform, but would also involve knowing how to create and read the files straight from the empeg volume.

Thoughts?

I had my Orinoco Silver card in an Ethernet Converter, then plugged directly into my car bay. I was able to transfer files this way very easily. I also added an external antenna which I mounted in my engine compartment for better range. Seemed to do the trick. Had to take it out as it got demolished when I had my wreck, but I will put it back eventually and take pictures.

I used an Intel 2011 access point with a crossover cable straight into the back of the empeg. I power both the empeg ignition sense and the Intel AP via a relay which is controlled through the Clifford Alarm. This way when I want to sync, press the remote button on the alarm, both the empeg and AP power up. The AP takes about 15 seconds before I can associate with it but then I have have full sync and ftp,http...

I found that in my old car, if you have the AP on all the time the battery will drain to a nonstarting level in about 3 days. So a remote power up method is a good thing.

Thanks Dava.

What was the power input for the Access Point? Did you have to install some sort of inverter/converter?

What was the range of the AP? I'm finding that the rangings vary dramically from 500 ft to 3.5 miles (yes, I actually saw an ad for one of these puppies!)

I have both an intel and a Cisco AP. The Intel one is 12V which is why I chose it. I would not recommend wiring it directly to the car due to negative spikes, varying voltages etc. I used a power regulator from one of our products at work. This gives a clean 12V @ 1A to the AP.

As far as range goes, it works fine from my house through 2 walls and an aluminium door to my garage. I have also parked it around 100m away from my office in the company car park with no problems.

I have to say that the speed for syncing large amounts of data is piss poor. You may want to look at the 56Meg stuff which is now dribbling into the market (still some licence issues in the UK).

Although 802.11b is supposed to be 11Mb/s, with the overhead you get a real life throughput of around 6-7Mb/s. If I were to start again, I would go 802.11a. At 56Mb/s you will surely fill the bandwidth of the 10Mb/s empeg port.

Isn't there overhead in the wired ethernet standards too? I've never seen 10Mb/s on standard ethernet or 100Mb/s on fast ethernet.

Stu

In reply to:

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I'sn't there overhead in the wired ethernet standards too? I've never seen 10Mb/s on standard ethernet or 100Mb/s on fast ethernet.

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yes there is a tcp/ip header overhead thats included in both ways (wired and wireless), but there is no error correction in wired, so therfore less overhead.

Well, 10 Megabit's per seccond isn't the same thing as 10 Megabytes per seccond. That's usually where people get more of the misunderstanding. A byte has 8 bits, so you're only going to see 1.25 megabytes per seccond on a 10bT link at the most. Then, you've got to deal with the overhead of protocols. Ethernet packets/frames are about 1500 bytes and have a small header(basicaly the MAC address of the sender and recipient). IP packets can be up to 64k and have a relativly larger header that has the addresses of the sender and the recipient, time to live fields, a checksum on the header, and other things I can't remember. It's a twisted web, but it all works out in the end.

Matthew
PS: All my numbers are from memory, so I could be grossly misrepresenting something...

I browsed around at a local electronics place and did see some of the new 802.11a devices. I didn't find the Intel or any that took 12v. I'll check the web.

BTW, what is this power regulator device you mention? Sounds like I should plan on buying that too.

I am sure there is, but my point was that the overhead on wireless is a much higher percentage (like about 50%). So for anyone simply looking at the rated speed and gathering up some expectations...downgrade them.

The regulator I used was an IC from a PSU we had lying around in my office. I would suggest that firstly you decide on the AP/convertor that you are going to use and check its current requirements. There is no reason that you have to have a 12V AP, it is just that this matched the parts I had available and the Intel boots in around 15 seconds as opposed to the Cisco which takes about a minute.

You should then be able to get a regulator from an electronics supplier which will satisfy the device's current and voltage requirements. If you have soldering skills then an IC will cost you around £5, otherwise budget on around £10 for and off the shelf cig. lighter adapter or something and modify it.

Important point to remember here is the actual throughput on an 11Mb 802.11b network (assuming noise level is such that it doesn't need to drop down to 5.5Mb) is higher than 10Mb Ethernet. The overhead on 802.11b is LOWER than Ethernet.

So you won't have any badwidth issues at the wireless end if you have 10baseT for your wired end.

And I've never seen the overhead get up as high as 50%, even on the earliest 11Mb kit Telxon produced, way back when they were the only producers of 802.11b DS kit.

Hmmm thats strange, I get much higher throughput with the wired link than I do with wireless and I am always at 11Mb/s.

I get around 600KB/s as opposed to 900KB/s.

Perhaps due to encryption level? My wireless network running encrypted is noticably slower than when I turn it off.

-Zeke

I noticed this too so I turned WEP off. It is still very slow.

I wonder if it is due to the multi vendor mix of equipment. I have a Xircom PCMCIA card (admittedly is states "Wireless by Cisco" on it), a Cisco AP and an Intel AP.

What kind of throughput do you get during a sync?

XPs task manager says that I am between 40% and 50% utilisation.

I don't use my wireless for syncing the empeg, just for browsing & file transfer to my Ipaq w/2 GB Toshiba HD. I've read about great differences in speed between WiFi vendors equipment. There's a good deal of information at http://www.practicallynetworked.com/reviews/ . This might be helpful. I also have heard of problems with XP and certain 802.11b devices, although I've nothing concrete to say in that regard.

-Zeke

I don't use my wireless for syncing the empeg, just for browsing & file transfer to my Ipaq w/2 GB Toshiba HD. I've read about great differences in speed between WiFi vendors equipment. There's a good deal of information at http://www.practicallynetworked.com/reviews/ or http://www.practicallynetworked.com/support/wireless_range_probs.htm . This might be helpful. I also have heard of problems with XP and certain 802.11b devices, although I've nothing concrete to say in that regard.

-Zeke

Admittedly Cisco (Aironet/Telxon) and Symbol encryption (WEP, EAP and LEAP) are not handled very quickly. Your best bet is not to do any encryption at the access point. From a security perspective there is little point anyway as they are all based on RC4, which is a poor algorithm. WEP can be broken in a matter of hours, and EAP and LEAP just increase the time needed.

All major 802.11b vendors agree - use IPSec if you want some degree of protection from hijacking, sniffing or unauthorised access. Using MAC ACL's obviously helps as well, and from my experience I would never run an 802.11 WLAN without a firewall between it and my LAN as they are so trivial to crack.

OOOps - went off on one there. My main point was to avoid using the encryption offered by the Wireless device, and do all that CPU intensive stuff on a fast CPU or not at all (depending on security desires.)

Yup, gotta use IPSEC to stay secure.

I have a couple of boxes here with software settable MAC addresses..