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WiFi

The reason why WiFi USB adapters suck

Juli 9, 2006 von Franz Hieber

People use USB WiFi adapters for a number of reasons, maybe their laptop doesn’t have built-in WiFi, or like me, there are no cards yet available that fit the tiny pseudo-PCMCIA slot of the MacBook Pro. Yes, I know the MBP has built-in WiFi, but my personal interest and professional activity involve using WiFi in alternative ways, so I need to test antennas, adapters, software and so on.

A few weeks ago, I bought a D-Link DWL-G122, the thought being that since it could be connected to a long USB extension cable, there wouldn’t be any of the RF losses associated to coaxial cables – and so I could go wardriving with a potentially better setup than the usual PCMCIA card with a pigtail and coax running to a roof-mount antenna. And I was wrong. The results were appaling – even the Vaio’s internal IPW2200 card was much better, detecting over twice as many access points as with the D-Link.

How could this be? Logically, having the antenna attached directly to the RF port of the WiFi adapter should reduce loss considerably – but it wasn’t the case. To be sure, I went shopping again, and this time bought a Conceptronic C54RU. One would think that the D-Link, costing around 39$, would have better performance, since the Conceptronic only cost me 25$ – there just had to be something there to justify the price difference. To my surprise, performance was almost identical. This prompted me to pry open the two adapters, and this is what I found:

181730312_9f9b647046
No, I didn’t just photoshop a clone of the first PCB. It is the same PCB for both adapters – which means that some OEM/ODM company is manufacturing these devices, and selling them in customized plastics to whoever wants them. Paying attention to quality? Probably not their very first priority.

The next two photographs show a little explanation on the structure of the RF section of these adapters. Do not confuse the PCB antenna as a diversity arrangement, it is basically a center-fed dipole. The designer paid no attention to the large mass of grounding material right next to the large pads of the antenna, and the matching circuit could probably not do much to alleviate the poor design. Here is the actual stripline [click the image for a larger version]:

181730309_4ffed07273

And the test connector:

181730313_8376d519b7

Bottom line: if you are close to your access point, and don’t really care about the range and quality of the link, this may be the adapter for you. But, if your intention is to take these devices for a wardrive, well, don’t.

No A2DP in OSX – maybe if Apple made a Bluetooth stereo headset…

Juli 2, 2006 von Harald Puhl

Last night I was watching a DVD on my MacBook Pro, and remembered that I still kept a Motorola Bluetooth stereo headset from the time I was working at SouthWing and we designed such devices.

Bluetooth stereo headsets use a profile called Advanced Audio Distribution Profile (A2DP), which allows them to receive medium-quality audio at 16kHz from compatible devices. Most USB Bluetooth dongles sold recently have the profile in their drivers, and there are some mobile phones from Nokia, Samsung and Motorola that also feature this profile. The advantage is that you can listen to music wirelessly, and also control the player from the headset, as they feature the usual forward, back, play and pause controls.

Once I found the headset, I switched on Bluetooth on the Mac, and started the pairing process. The headset was recognised just fine, and pairing completed, but I noticed that it had been connected as a Handsfree device, with A2DP nowhere to be found. Since there doesn’t seem to be a method of connecting the headset permanently, so the audio is always routed from the Mac to it, the attempt was frustrated – I couldn’t even listen to the DVD in low-quality audio.

Why has Apple left out this profile, is it a blunder, or a calculated approach? As to this date, Apple doesn’t manufacture or resell any Bluetooth wireless headsets (only one can be found at their store, and it comes with a dongle for the iPod, so it doesn’t count). So, why would they have an interest in adding the A2DP profile, so that we could use any other headset? If they are in the process of designing their own, they might want to keep the profile away from Macs until they launch it.

Then again, if we give Apple a vote of confidence that they are not that insidious, it could be a blunder. And a big one. Windows has been able to work with A2DP headsets since late 2005, so they have had plenty of time to add the profile to their Bluetooth stack.

A few myths and facts about Bluetooth, versions and profiles for the curious:

1. Profiles are mostly independant of the Bluetooth version. It is perfectly possible to have A2DP in a V1.2 Bluetooth device, just the same as a V2.0 + EDR can have just two profiles and miss many of the usual ones – the mix is up to the manufacturer and driver supplier.

2. EDR stands for Enhanced Data Rate – this does not increase the range, just increases data throughput from around 700kbps to around 2.1kbps, by using a different modulation scheme. The Bluetooth protocol and profiles stay just the same – the advantage is that since data takes almost 1/3rd of the time to send compared to non-EDR devices, there is a considerable power consumption reduction.

3. “Device Y doesn’t support profile Z”. Again, this is up to the manufacturer, and it’s hard to add new profiles, specially in embedded devices. Some chipsets use masked ROM, which means that the Bluetooth stack, profiles and other settings are burned at the time the silicon is printed – so, no software updating on these. Masked ROM is considerably cheaper, although has an initial setup cost of $100.000, so it’s only good for high-volume production runs. The chips can drop $1 to $2 compared to the flash EEPROM counterparts.

As an example of a very poorly implemented Bluetooth solution we can find the Logitech MX5000 keyboard and mouse combo – it sucks. A lot. I am preparing a review that will try to investigate why it does the stupid things it does, such as repeating the first letter you type when it wakes up a dozen times, or why the mouse starts wondering around the screen as if it was possessed by a poltergeist.

The WARTHOG – a WiFi router on steroids

Juni 16, 2006 von Harald Puhl

Since I first started tinkering with the Linksys WRT54G router a couple over a year ago, replacing the stock firmware with OpenWRT, I have been thinking about making something special with it.

The router itself is a great piece of hardware, having a WiFi adapter, and two wired LAN interfaces. OpenWRT allows hackers to do almost anything with the device – there are plenty of mods, such as the dual serial ports, SD card to add storage space, and more.

I tried to look for a GSM/GPRS mod, which would add a module to the router, allowing it to communicate with the outside world using data and SMS – but there was no such thing, at least integrated into the router’s casing. So, the challenge was born, to design a PCB that would hold an SD card reader, a GSM/GPRS engine, and a GPS receiver. What could you do with this device? Here is a short list:

  • An autonomous wireless IDS with logging and SMS alerts. This could warn you when a pirate is trying to break into your network via WiFi. It would be completely autonomous, only needing a power source to run.
  • Self-contained wardriving box, which can save logs to the SD card, and be controlled via SMS messages. It could also periodically send you a status report to your mobile phone.
  • Mobile hotspot – by bridging the GPRS data connection to the WiFi signal in AP mode. Not very fast, but wait until 3G modules come out…

Here is a first picture of the PCB mounted onto the WRT54G. It doesn’t show the mess of cables that covers it, but gives an idea of what it will look like.

My Fon router has arrived!

Juni 8, 2006 von Harald Puhl

I ordered a Fon router when they dropped the price to 19$ from the usual 25$, to try the service and see how it performs. My feelings right now are mixed, as had I waited one day, I could have purchased it for 4$.

This ‘rubbery price’ approach was explained a few days ago in Martin Varsavsky’s blog, as a demand elasticity test. Basically, you drop the price, and see if hordes of people jump on the offer. Yesterday, after having been back at 25$ for a few days, they changed the price to 1$, but only for a few hours.

Fon: maybe a not-so-social router

Juni 7, 2006 von Harald Puhl

I have recently been following Fon, a movement that aims at creating a worldwide WiFi network, with Bills, Linuses and Aliens sharing their broadband with others, some for free, others for profit – split with Fon. The basis of Fon is that you connect a Linksys WRT54Gx WiFi router running special firmware to your broadband internet connection. This firmware turns the router into a captive portal, which then allows you to control access to the internet.

During the last couple of weeks, there has been some noise at Fon about having finally achieved production of their own WiFi router – they call it La Fonera. The move may seem obvious, as right now, they are buying the Linksys routers at full reseller price, in turn reselling them heavily subsidized at $25 a piece $1, as I’ve just read a minute ago. What I still don’t get is the title of the recent post in Martin Varsavsky’s blog, ‘Fon, the Social Router’.

A few days ago, Fon announced the purchase of 1.000.000 (literally!) of these new routers from the taiwanese manufacturer Accton. This company already manufactures WiFi routers, amongst other devices, and so it’s perfectly plausible that they can manufacture a customized router for Fon.

The main reason for manufacturing anything in China or Taiwan is the labour costs are extremely low. The electronics aren’t cheaper over there, and as a matter of fact, most of the core components are sold by western companies, such as Broadcom, Intel and Atmel. Labor conditions in chinese plants vary, from outright slavery to pretty good, but even then, one thing is a fact: they work all year round, including all weekends, only having ten days off for the Chinese New Year.

Reading Accton’s site, it appears that they treat their workers very well, and I applaud that. But this also means that they cannot produce as cheaply as the sweatshop-style manufacturers. A WiFi router with the horsepower required to run Fon’s platform is not cheap – let’s estimate roughly $22 per unit, for a purchase of 1 million units. If this estimate is correct, Fon would have blown on these routers a tad more than the entire funding they got from Skype, Sequoia, Index and Google.

If they were to give away the routers, to recoup this investment Fon would have to sell approximately 11 million 24-hour access packages, at $2 each. That is assuming Fon takes 100% of the money – with the Bill model, they would only get 50% of the income, as it is shared with the person providing the broadband and maintaining the hotspot. If they were to sell the routers at cost, they’d still have a huge logistics nightmare in their hands. Failure rates in mass-produced electronics range between 1% and 3%, meaning they could have up to 30.000 returns, costing them $1.32 million in hardware, plus logistics and other costs. One thing is to be a promoter of social WiFi – another is to turn into a hardware manufacturer – be it by ODM contracts, or by making the devices yourself.

So, I leave some open questions: has Fon chosen a company that respects human rights, treats its workers with dignity, but won’t give them a good deal as they could have gotten somewhere else, thus affecting their ROI expectations? Does investing in 1 million routers make economic sense with their current business model?

The most expensive wardrive ever

Juni 6, 2006 von Franz Hieber

If you’ve done a more expensive one, I’d like to hear it!

Today I had to get to the center of Geneva from the airport, and in a bit of a hurry as the meeting I had to attend was getting close. I decided to take a taxi, which would also allow me to do a quick wardrive using my Qtek and a Bluetooth GPS. Finding almost 80 WiFi access points on the way was great, but the bill was painful! In all, the round trip from and back to the airport cost me 60 euros, some quick math makes each AP cost 75 cents (around $0.96).

Tomorrow, I will post some stats and a quick map of the captured APs. The stats will of course go to WiGLE, and the map will be made using an updated version of StumbVerter I’m working on – this will use MapPoint as usual, but you will also have the option of creating maps in Google Earth format. However, they will not look like the usual 2D icon maps that can be made using existing scripts, but will feature the traditional Netstumbler towers in 3D. How to show the signal strenght is being worked on, any suggestions?

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