مقال أعجبني ولو أنة يحش أسمي بس يالله للفائدة العامة 
What I Don't Like About BlueTooth
November 2 , 2002
Article by: Russ Smith, Senior News Editor
As you've no doubt read elsewhere, Microsoft has decided to embrace the BlueTooth technology and support it on an operating system level in a revision to Windows XP. That's good news from the standpoint that it will help to solve some of the conflicting implementation problems. Unfortunately, BlueTooth has a number of problems, inherent in its design, which have nothing to do with how well it's integrated on the desktop.
These problems all result of the BlueTooth standard trying to do too much. Because of that, many BlueTooth implementations can't do enough. Clear as mud? Try this: The creators of BlueTooth violated one of the key rules of networking: You don't mix the way in which information is transferred from one device to another with the services the device offers. The mechanism and protocols for moving packets of information from one device to another is a "low-level" function. Higher level functions such as file transfers, data security, and resource access, shouldn't care at all how the packets are moved. All they care is that they ask for some data and it gets there.
BlueTooth violates this principle in several ways. First, each device has a set of "profiles" it supports. The profiles determine how each device is able to access other devices -- a high-level function. Now there's no problem with a device "knowing" what it's capable of. It makes little sense for a headset to have file-transfer capabilities (unless it's got a built-in MP3 player). The problem is that the profiles are hard wired into the BlueTooth hardware. This means that although I've got a perfectly good BlueTooth radio in the USB-connected "dongle" on my desktop system, it will never be capable of acting as a LAN Host. I can use ActiveSync to my hearts content and, because of the pass through capability, I can even access the Internet. What I can't do, unless I buy new equipment, is to access network resources like my desktop's hard drive through the BlueTooth module.
I can understand, to some extent, why the creators of BlueTooth went the profile route. It allows devices to be "plug-and-play" (or perhaps I should say "proximity-and-play.") Because the profiles are built into the devices, you don't have to load a driver or some other software to use a BlueTooth headset on your cell-phone. As long as the two devices support the appropriate profiles, you don't have to do anything but put the two close enough together and enter the pass key if any and you're up and functioning. (Theoretically. Often, BlueTooth connectivity can be a bit difficult to get working.) Unfortunately, while that works well with "dumb" devices, it can make for great frustration with intelligent devices.
With WiFi, you have a pure network protocol. The WiFi circuitry and protocols don't "care" whether you're doing streaming video, ActiveSync, or browsing a network folder on your desktop. I can use WiFi modules from virtually any manufacturer on my desktop and on my Pocket PC -- I can even change which card I'm using -- without fear that some service will be unavailable. To take it a step further, I can replace my WiFi (802.11b) wireless LAN equipment with 802.11a wireless LAN equipment without changing any settings or software on either my desktop system or my Pocket PC (except for the low-level card driver) and everything will work just as it did before, except faster. I wish BlueTooth acted that way.
Another problem with BlueTooth is that security (such as it is) is also built into the specification. Again, the low-level "transfer mechanism" should not have anything to do with the higher-level encryption or security protocols. By mixing the two BlueTooth creates an unnecessary complexity. In order to protect your BlueTooth phone from being "pirated" by someone with a BlueTooth card, you set up a "PIN" that a connecting device must enter before it's allowed access. You can bypass this by "bonding" two devices, which keeps a record of the other device and allows quick connection. However, if I bond to my desktop, then purchase a different BlueTooth connector for it, I have to go through the bonding process again. That's because I bond with the connector, not the desktop itself.
Again, that's unlike pure networking where, once I set up my Pocket PC to get access to my Wireless Access Point, I could swap in another WAP with the same settings and the PPC would connect without any trouble. Conversely, if my WiFi card is lost or damaged, I can buy another one, use the same settings as the previous card and connect without doing anything to my Wireless Access Point. Again, I wish BlueTooth acted that way.
A third potential issue with BlueTooth is that it allows only seven connections to other devices. That seems like a lot and may work quite well for most folks but the it's another result of combining services with the transfer mechanism. Again comparing to WiFi, the only real limit to the number of devices I can connect to over a WLAN is that I can only have 255 devices in my local "sub-net." Currently, the Pocket PC (and Windows CE 3.0) operating system's support for WINS resolution as well as the ActiveSync software itself allows me to use ActiveSync with only two other computers on a network. That's a software limitation, however, and the WINS resolution issue will be corrected in WindowsCE.NET. That helps highlight the difference between a mixed networking protocol like BlueTooth and a more pure networking protocol like WiFi. BlueTooth "hard-codes" the limitations in such a way that a software solution is extremely difficult if not impossible.
The final, and most annoying aspect of this mixing of low-level and high-level functionalities is that it takes a lot more computer resources to load in all the BlueTooth functionality than it does to access the low-level driver for wired or wireless LAN access. Most of us with BlueTooth-enabled iPAQs have seen the most-annoying "You must perform a soft reset before you can turn on the BlueTooth radio" message -- something I've never seen when I plug in my WLAN card. You can solve the problem by leaving your BlueTooth radio on all the time at the expense of tied up RAM and power drain or you can resolve to reset your machine in order to be able to engage ActiveSync. The need to reset more than occasionally eats up any time savings you might have gained by bonding the two devices.
Don't think that my discussion of the problems with BlueTooth means that I don't find it useful and wouldn't recommend it for certain situations. For using a phone as a wireless modem it's quite useful. Unfortunately, I think its inherent flaws make it far less useful than it could be in other situations. Because of that I'm not planning to invest much in BlueTooth accessories. How about you? Do you think that the advantages of BlueTooth outweigh the issues? Will your next Pocket PC have to support BlueTooth or WiFi or both? Tap the "Discuss this Article" button below and let us know.
22-01-2003, 10:08 PM
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