1. Setting Up an Ad-Hoc Wi-Fi Net
Question: How do I set up a wireless network between two computers without a router? Can they share an Internet connection this way?
Answer: The ability to create a quick and dirty network between two (or more) computers or PDAs is an underutilized Wi-Fi capability that is really quite simple to set up. You can even connect Macs and PCs this way. First, be sure both computers are disconnected from any router. Then set manual IP addresses so that the two computers will be able to see each other on the network (normally a router performs this task). They should each be something like 192.168.2.x, where x is a number from 1 to 255 and different for each computer (more than two computers can be in the ad-hoc group). The subnet mask for each should be 255.255.255.0.
Then open your Wi-Fi adapter setup utility (unless your card has a proprietary setup program, this means opening the Windows Wireless Connection Manager in the Windows XP System Tray or choosing "Create Network" from the AirPort menu in Mac OS X). Then make sure the adapters in each computer are set to "Ad-Hoc" mode (as opposed to "Infrastructure," which is for connecting to routers), with the same SSID (case-sensitive) and channel number. They should also be in the same Wi-Fi mode, such as b, g or enhanced-g, as applicable. A MIMO card in MIMO-only mode won't be able to talk to a plain-g card, for example. Don't bother with encryption if it's just a one-time connection in a non-public place. If you do need encryption for a regular connection, get things working without encryption first, then add the same type of encryption on each end, with the same password.
You can also share an Internet connection with computers on your Ad-Hoc network. In Windows XP, go to the Network Connections control panel, click on the connection you want to share, then choose "Change settings of the connection." Click on the Advanced tab, and then turn on Internet Connection Sharing. In Mac OS X, open the Sharing control panel in OS X and click the Internet tab, then turn on sharing. Note that you do this ONLY on the computer that is physically connected to the Internet, not on the computers that will share the connection. This is also a great way to share a hotel room Ethernet connection.
2. Sharing Files Over Wi-Fi
Question: How can I share files between two computers over Wi-Fi?
Answer: One of the great things about home Wi-Fi networks, is that not only can you share a fast Internet connection, you can also use the network to share files among all the computers in your house. But at the same time, you probably don't want to open up your entire directory to your kids (and their friends). Here's how to share files safely with Windows XP Simple File Sharing.
First, organize files you expect to share, such as photos, music, and the family calendar, into their own folder or folders on your hard drive. Then decide who else should have access to these folders, and if you want to require a password for access. Finally, configure Simple File Sharing access permissions using the steps detailed here.
On a Mac, sharing files is even easier. Just put any files or folders you'd like to share in your Public folder, then open the Sharing panel under System Preferences and turn on Personal File Sharing.
You can also share files over an ad-hoc network by following the ad-hoc connection tips above first.
3. How and When to Turn Wi-Fi OFF
Question: For my job, I have my laptop mounted in my vehicle. As I drive around various cities, I'm always getting an annoying popup asking if I want to connect to a Wi-Fi net. Seems as if everybody and their uncle has a Wi-Fi network in their home. How can I avoid this annoying popup everytime I go by a hotspot?
Answer: First of all, the popup is not just annoying, it's a sign that you are leaving your computer unprotected. For every time you get the popup, there are probably several other times where your computer is automatically attaching itself to a network with a familiar SSID like "linksys" or "tmobile." Since these networks would be unencrypted, you could be vulnerable to hacking.
We always recommend that users turn Wi-Fi OFF when on the road between hotspots. Turning it off not only makes sure you can't accidentally associate with a hotspot, it saves precious battery life. To turn Wi-Fi off in Windows XP, simply left-click on the wireless network icon in the system tray and choose "Disable."
This also removes the icon from the tray, so to turn Wi-Fi on again, you'll need to open the Network Connections Control Panel (from the Start Menu), then just double-click on your wireless connection to enable it again. (Note that you can also disable the Wi-Fi adapter from this Control Panel.) That's all there is to it. If you expect to turn Wi-Fi on and off a lot, you might want to create a shortcut to this control panel.
On the Mac, turning Wi-Fi on and off is even easier. It's the first option under the AirPort menu in the Finder. You should also turn off Bluetooth between uses. Bluetooth is not as critical security-wise, but also uses a lot of power on your laptop.
4. By the Numbers: Real-World Throughput Rates for DSL & Wi-Fi
Ask JiWire: Why is the upload speed for Internet connections always so much slower than that for downloads? I have to send a lot of large pictures to clients and it is faster to do this at Starbucks than at home with my DSL line! And why does my Wi-Fi router say 300Mbps when I'm lucky to get a fraction of that?
Answer: What you are experiencing with your DSL line is the difference between asymmetric connections with differing up/down speeds, and symmetric ones, where bandwidth is the same in both directions. Most home DSL lines are asymmetric, with uploads much slower than downloads, since ASDL allows for voice connections on the same line. Symmetric DSL is also available, but is more expensive and requires a dedicated line. Similarly, dedicated T1/T3/T+ lines are symmetric. T-series lines are even more expensive than SDSL, and offer speeds starting at 1.5Mbps. Businesses are the primary users of both SDSL and T lines, since they may be hosting a Web site, or have a large number of users sharing a line.
ADSL typically supports data transfer rates from 1.5- to 9Mbps downstream, but only 16- to 640Kbps upstream. Upload rates vary by provider, but are usually 15 to 50 percent of download speeds. That superfast-sounding 1.5Mbps DSL line you're paying extra for may be only giving you 125Kbps for uploads -- about three times as fast as dialup! The kicker is that all T-Mobile Hotspots (such as Starbucks) use at least T1 lines, so assuming you're not sharing the line with a lot of other users, your upload speeds will indeed be much faster at a hotspot than at home.
A side note is that cable and cellular modem data rates are also asymmetric. Cable modem standards provide for a maximum of 30Mbps downstream and 10Mbps up, but this is divided between all users in your area, and individual rated speeds are typically 500Kbps-6Mbps down and 256-750Kbps up. For cellular carriers, there is only so much space in the wireless frequency bands they own, so they purposely divide the limited number of "slots" unevenly between up and down data. Most people do a lot more downloading than uploading, so more slots get allocated to downloads. EV-DO Rev. A has vastly improved upload speeds over the Rev. 0 version, however.
To measure the real-world upload and download speeds you are getting from any of these connection types, use CNET's Bandwidth Meter or SpeedTest.net
And what about those Wi-Fi speeds? Sometimes we can get blinded by the numbers on the router box: 108Mbps, 125Mbps, or even 300Mbps with the latest generation of draft-802.11n routers. Actual data rates are always going to be much less, but just how much throughput should you expect to get under real-world conditions?
The rule of thumb is that you'll start with about half the stated throughput. So for a plain vanilla 54Mbps 802.11g, we'd be happy to get 27Mbps out of it, and double that for an enhanced-g 108Mbps router. Then you need to cut that number even further depending on the distance from your router, the number of simultaneous users, and whether you're using encryption. Throughput drops dramatically with distance, as signal strength decreases. So even with a 300Mbps router, in our house we would get barely 80Mbps in the upstairs rooms, even less with encryption.
Similarly, simultaneous users will cut available throughput. Home routers have only ONE Wi-Fi radio, which must maintain communication with ALL the Wi-Fi clients attached to it. So even if all equipment were in the same room at maximum signal strength, two clients downloading large files at the same time would cut throughput for each by more than 50 percent, since there is also overhead involved. And throughput will be shaved even more when you are running mixed networks of different types of clients, such as 802.11b, g, and n, or if you are in range of neighboring Wi-Fi nets or 2.4GHz cordless phones, which can cause interference. <
What all this means is that to get the maximum throughput under any given load, the best strategy is to start out with as fast a router as you can buy. Starting out with a draft-n router like the Netgear RangeMax Next won't actually give you 300Mbps throughput, but it WILL give you nearly five times the performance of a typical g router.
5. When Bluetooth Doesn't Bite
Ask JiWire: I bought a Bluetooth headset so I can use VoIP services with my laptop when I'm at Wi-Fi hotspots. The headset seemingly "pairs" with the laptop, but I don't get any sound. What gives?
Answer: Unlike Wi-Fi equipment, which can interoperate at least at a basic 802.11b or g level, different Bluetooth devices support only specific capabilities, called "profiles," appropriate to their function. For example, a headset has no need to be able to receive an image from a Bluetooth camera, nor sync data from a computer. Likewise, a camera has no need to connect to a headset or a mouse. While these examples are obvious, there are so many different Bluetooth profiles, with new ones cropping up all the time, that there are many instances of seemingly logical connections that can't be made. Not all laptops support the headset profile, although they may support the Serial Port, Fax, Dial-up Networking, and Synchronization profiles, among others.
Adding to the confusion is the emergence of new stereo audio Bluetooth profiles designed for listening to music from portable players, which may also be phones or laptops. As a rule, you should check that any device you buy supports the specific profile(s) you need, including any copy-protection schemes. But all is not lost in your case. Since laptops have USB ports, you can usually add Bluetooth "dongles" that support whatever profile is missing from the internal Bluetooth stacks. Just be sure to turn off the built-in radio so as not to confuse things.
In the future, Bluetooth will get both simpler and more complex. Pairing will become much easier, but encryption will be improved, and bandwidth will get much higher, enabling cordless VoIP handsets, fast audio and video data transfer between home entertainment system components, and more. For a roundup of current Bluetooth devices, including the best headsets and hands-free car kits,
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