A number of issues come up frequently with mobile devices that affect their ability to connect to wireless networks and use their services. Here some of the problems that occur with a variety of mobile devices, including NICs, antennas, Palms and PocketPCs, cell phones, Bluetooth, wireless USB, and IrDA devices, to name but a few.

My laptop’s new NIC won’t connect to a working access point although the settings seem correct. What should I look at to correct the problem?

If you don’t get a signal where you know a signal exists and the lights on the NIC seem operational, you need to check your settings. Once you are certain that your wireless network settings are correct, you can move on to checking hardware. The wireless network settings that need to be correct are those for:

• SSID (these names are case-sensitive)
• Enabling the connection.
• Selecting the right channel.
• Providing the correct WEP/WPA key.
• Selecting the correct access mode (infrastructure or ad hoc)

If these settings are correct, check that your equipment is correctly installed in the Device Manager. You should see the NIC listed without an exclamation mark or yellow triangle next to it. If there is a yellow exclamation mark, it indicates that there is a resource or IRQ conflict.

Uninstall the NIC and reinstall it with the most up-to-date driver. Do not simply reinstall the adapter software because that will leave the current driver active on your system again. If none of this works, try swapping out for another network card.

My current Centrino notebook doesn’t support 802.11g. How do I get that standard in my computer?

The original Centrino notebooks came with built-in 802.11b wireless networking. Some of the current generation of laptops enable you to swap out the wireless card to go to the next generation. Most do not. The easiest way to add enhanced wireless capability is to add an additional wireless PC Card or wireless USB adapter to your computer.

With two different wireless transceivers in your notebook you run a minimal risk of creating a looping situation. You also want your notebook to choose the fastest adapter for throughput. Therefore, the best thing to do is to disable the on-board wireless NIC and use your faster card whenever possible.

The nice thing about 802.11b is that it is broadly compatible. If your upgraded PC Card can’t seem to connect, you can disable it and enable the on-board capability. However, most of the faster cards come with multiple standard support, and almost always support 802.11b.

Why can’t my laptop get a strong wireless signal in one specific location of my house even when I move an access point close to that location?

The most probable cause for a poor 802.11 signal is radio interference. The first thing to determine is whether this is an intermittent or constant problem because that will determine the type of device that might be responsible.

Interference occurs when two devices try to send packets over the same radio frequency as one another, resulting in timeout errors or data loss. For intermittent interference, check the following devices:

• Wireless phones.
• Microwave ovens.
• Wireless radios.
• Bluetooth devices.

For 802.11g networks, any device broadcasting in the 2.4 GHz range may cause a problem. For 802.11b networks, you may find a problem when you try to use a 900 MHz range.

You need to move your access point at least 10 feet away from a microwave oven at a minimum; 25 to 30 feet would be better. So moving the access point may be a simple solution to this problem.

For constant interference, consider these possible causes:

• A nearby wireless network.
• Overlapping access points with the same channel number.

Actually these are both essentially the same problem, and they have the same solution. Try changing the channels of adjacent radio transceivers so that they don’t overlap. If this is your neighbor’s network, you will have to seek some cooperation from them or try to alter your settings to compensate.

Do a site survey to see where you can see other networks or multiple access points, as well as their settings, and make appropriate changes. Another way of working around the problem of interference is to strengthen the power of your signal in the problem location.

The stronger signal essentially overwhelms or swamps the weaker signal, allowing devices to lock onto it. This may not make you popular with your neighbors, but it is effective. Also try changing the configuration parameters. In addition to changing the channels you can also use a different frequency hopping pattern.

The newer standards support 5-GHz signals, and there is less interference using this frequency. You will also find that upcoming 802.11e standards offer avoidance algorithms that help prevent RF signal interference.

Why is it that when I add an antenna to my wireless device the signal strength doesn’t change?

Assuming that your wireless device is compatible with the antenna, the most likely reason is that the antenna you added is not positioned correctly or is not of the correct type to provide you with the needed gain to notice a change in signal strength.

If you are located in the center of an access point’s range, adding an omnidirectional antenna would help your signal strength. However, if you are off to the side of a building, you may need a directional antenna to get the boost you need. Antennas and wireless devices are very sensitive to orientation.

That is, the characteristics of an antenna’s transceiver most often qualify the device as a horizontally or vertically oriented device. Small changes in both the antenna and the mobile device can make a large difference in signal strength.

Try changing the orientation of both devices as well as their positioning to see if it makes a difference. The chances of an antenna being broken, particularly a non-powered antenna, are small; however, if you have a powered antenna you should check that it’s getting its required amount of power.

My laptop can’t receive a signal from my access point, although I’m well within the advertised range of both devices. What could be the problem?

Several reasons exist for why a laptop’s NIC may not be able to detect an access point. The most important limitation is the number of intervening obstacles between your laptop and the access point. Walls, ceilings, and even metal doors can dramatically reduce the signal strength.

Also, the effective wall thickness is greatly enhanced by the angle of the wall between your laptop and access point. A 2-foot wall would appear 4 feet thick to a radio signal at a 45-degree angle, and over 52 feet thick at a 2-degree angle. What the obstruction is made of makes a big difference as well.

Metal and concrete have higher stopping power than does wallboard and glass. Check also that your radio signal isn’t being interfered with by other radio transmitting devices. The common problems involve appliances operating on a similar frequency, for example 2.4-GHz cell phones interfering with an 802.11g network.

Other possible sources of interference can be access points set up with the same channel number that overlap. Experiment with positioning your mobile device and its antenna to improve your signal strength.

My NIC advertises that it supports an enhanced version of 802.11a or 802.11g, but I get nowhere near that throughput. What is wrong?

All of the enhanced versions of different 802.11 protocols are based on proprietary tweaks in the software or chip set used by a particular vendor.

In order to get something like D-Link’s Super G or Super AG mode to work, you need to have devices on both ends that support it. In most instances that not only means devices from the same vendor, but devices in the same series from the same vendor.

How do I find the MAC address for the NIC in my laptop?

Often the MAC address is located on a label on the card itself. If you need to locate the address while the card is in the laptop, there are several methods you can use. Perhaps the easiest one is to use IPCONFIG /ALL to obtain the address.

The Toshiba Portege 3505 shown in Figure 25-1 contains a 10/100 wired Ethernet connection, a built-in internal Intel modem and the Toshiba Wireless LAN Mini PC Card (internal), and a D-Link AirPremier PCMCIA (PC Card) external NIC. To get the MAC address in Windows XP, do the following:

1. Click Start>Run.
2. Type CMD and click OK.
3. Type IPCONFIG /ALL. Look down at the section for your wireless adapter for the line starting “Physical Address.” That line contains your MAC address.

To perform the same procedure in Windows ME/98/95, do the following:

1. Click Start>Run.
2. Type winip.cfg and click OK. The IP Configuration dialog box appears, with the MAC address listed as the Adapter Address.

My Palm is having trouble connecting wirelessly. What could be wrong?

Different models of Palm-type phones have different problems, so if you are using a Palm or Treo PDA as a phone, or a Samsung or Kyocera phone with the Palm OS built in, you should check for the problems specific to your model first.

One common problem is that some of these devices must be put into wireless mode first before they can be used. To do so you might need to hold the power button or the disconnect button for a certain length of time, after which you will see an icon on your screen for a wireless connection or you might get a confirmation tone.

Like all phones, when a Palm is outside of its wireless area, it won’t be able to connect. Try moving to a different location. For locations where your Palm device is having trouble locking onto a network, try restarting the device and letting it search for a network again.

Sometimes doing this helps you connect successfully. If your battery is low, you might not be able to switch successfully into wireless mode.

Why does the new wireless USB adapter I just plugged in fail to detect the network?

A number of reasons exist for why a wireless USB adapter may not be working properly. The first and most obvious reason is that the plug isn’t connected properly; or if the device is a powered USB device, that you forgot to plug in the power adapter.

Sometimes you need to plug a wireless USB device directly into a powered USB hub. Try plugging the device directly into the USB port that’s located on your computer itself because all of those ports are powered.

When the wireless USB device is properly connected, the power light should be on and you may see data lights flash if the unit has them. Another reason why a wireless USB adapter might not work could be that the software isn’t installed properly. Uninstall the device, and then reboot and reinstall the device.

Wireless USB is plug and play in Windows XP, so the new hardware should be detected and initiate the setup program. If the install fails to solve your problem, go to the vendor’s Web site and look for a more up-to-date driver to install.

Use the Device Manager to open the device and then install the new driver in place of the old one. If your wireless USB adapter can receive a signal from an access point in the infrastructure mode but can’t log on, check its settings. The two devices must:

• Be set to the same broadcast channel.
• Be set to the same SSID.
• Be set to the same security options.
• Be part of the same workgroup or domain, and each computer have a unique name.
• Have TCP/IP enabled, be on the same subnet, and have a unique address.

I can’t seem to get my IrDA device to work properly. What are the issues?

IrDA devices are really pretty simple serial communication devices. The number one problem with getting them to work is having a COM port conflict or having set the COM port incorrectly. The first thing you can try is to alter the COM setting for the IrDA device.

If that doesn’t work, change the COM port setting for your mouse or modem if those are serial devices on your system. Doing this may allow your IrDA device to work properly at its default settings. You change these settings in the Mouse or Phone and Modem Options control panels.

You can also change the COM settings in the Device Manager for each of these devices. Not all motherboards support IrDA natively. If yours doesn’t, you will need to pick an IrDA device that doesn’t need motherboard support. IrDA drivers are part of the Windows operating system, although some vendors supply their own drivers.

If your IrDA device is installed properly, but doesn’t seem to actually control the device it’s intended to control, check that the two devices are within the effective range of one another. You can also try lowering the rate at which data is exchanged and seeing if that improves the communication.

Finally, check that your IrDA device is compatible with the device you are trying to control. Several different types of IrDA devices are on the market, and each one can work with only a subset of the TVs, printers, computers, phones, and other devices that accept IR signals.

My two Bluetooth devices don’t connect. What could be the problem?

If you expect to make a connection between Bluetooth devices, the first thing to check is that Bluetooth is actually installed on the devices in question and that you’ve turned the Bluetooth service on.

The service is turned on in software. After that, the next most likely thing is that the profiles are missing on one or both devices, or that the two profiles don’t match. For example, if you want to connect a mobile phone to a headset, both devices must have the same profile, which in this case is the headset profile.

To connect a Palm or PocketPC that is Bluetooth-enabled to that same phone, you would need a dial-up networking profile; and should you wish to print from your PDA, you would have to have the Basic Printing Profile (BPP) on both devices. These profiles are specific to each manufacturer and model.

With devices that have Bluetooth built into them, chances are that the service is on and has the correct profiles to find companion devices. A Bluetooth profile is rather specific for the kind of device being used. If you have a Bluetooth keyboard or mouse, those devices are supported by a profile called the Human Interface Device, or HID, profile.

Because a mobile phone wouldn’t come with this profile, you shouldn’t expect Bluetooth keyboards or mice to be able to connect to one another. Another issue is that the two devices might be out of range of one another.

If you figure that Bluetooth has about a 30-foot bubble, that range could be lower if the two devices are separated by a wall. Try moving the devices closer.

What does the Bluetooth message “Devices not found” mean?

The pairing or bonding process works by passing a protected passkey from one device to the other over an encrypted link. Depending on the security settings, you may not be able to make a direct connection. For example, you wouldn’t normally leave on a device-to-device connection for personal address book or contact exchange.

When you wanted to exchange the data, you would turn security off for the short time you were in range. If you see a message like “Devices not found,” device discovery may not be enabled.

On some Bluetooth devices, depending on the manufacturer, there is a setting that turns on device discovery. If that setting is turned off, you will not be able to make that connection. Some Sony and Ericsson mobile phones have this feature on a discoverable menu.

What does the message “Pairing unsuccessful” mean?

The fact that you got this message means that the two devices engaged in a handshaking operation but didn’t have the correct information to proceed in establishing the connection. Most often this means that there was a wrong password or PIN presented.

It’s possible to also create a pair and still not have the two devices work in the way they should. The usual reason for this to happen is that the devices are trying to use different profiles. Check the manual for the two devices or the online Web site of the manufacturers to see what profiles are supported.

What different Bluetooth devices does the iPAQ support?

The iPAQ hx4700 series Pocket PC supports the following Bluetooth profiles

• Basic Printing Profile.
• Dial-Up Networking Profile.
• File Transfer Profile.
• General Access Profile.
• Generic Object Exchange Profile.
• Hard Copy Replacement Profile (printing)
• LAN Access Profile.
• Object Push Profile.
• Personal Area Networking Profile.
• Serial Port Profile.
• Service Discovery Application Profile.

Any device with one of these profiles can connect to, transfer data to and from, and be commanded by this particular iPAQ.

What is bluejacking and how can I prevent it?

Bluejacking is the unauthorized access of one Bluetooth device by another. It’s relatively easy to do, and for phones and other devices it can have consequences. To bluejack another person’s phone, the intruder uses Bluetooth on his phone to discover any available phones in the vicinity.

When the handshake completes and the devices are paired, the two phones are linked and information on one phone can be seen on the other. Most often, the other person will be doing this as a prank or be using the method to communicate something to you anonymously, but in some instances the practice is much more insidious.

There are reports that once the pairing is complete, it is possible to suppress the display of the intruder’s device on the target phone. Once the trust is established, anything in memory can be backed up to the intruder’s phone. The stealing of contacts in this manner is called bluesnarfing.

Worse still, once a phone is bluejacked, the trust relationship stays in the memory of the cell phone until all the memory is erased. The easiest way to eliminate the threat of bluejacking is to turn off your autodiscovery feature. If an intruder can’t see you, he can’t pair up with your phone.

Also remember that if your phone is bluejacked, the person doing the bluejacking must be nearby because the intruder is using Bluetooth for a transmission mechanism. For more information go to BlueJackq.com.

Why do I hear static or cross talk on my mobile phone?

Several reasons exist for why you might get static on your cell phone. If you are operating on a low battery, there may be sufficient charge in the device to make the phone call and connect, but not enough charge to lock the signal. If your battery is low, try changing it or using a car charger.

If you are hearing constant static, you may be in an area with electronic interference. Move away at least 25 feet from powered devices such as microwaves, blenders, or other mobile phones, and your reception may improve. Constant static also occurs when your phone has a defective antenna, or if your phone is damaged in some way.

Make sure that your antenna is pulled all the way out because an antenna that is partially retracted can be a cause of static and dropped calls. If the static isn’t constant, but varies from one location to another, the most likely reason that static exists is that you are in a poor reception area.

You should move to a better area. You’ll also get static when there are electrical storms in your area. Under most conditions, a digital phone is less susceptible to static than an analog one. You may also find that if you have an analog phone, you experience cross talk.

Cross talk is when you can hear other peoples’ conversations in the background of your own. It more often occurs in land lines inside buildings with multiple lines carried over wires that are near to one another.

The signal leaks from one line to the other. The simple solution to cross talk is to switch from analog to digital if your cell phone allows this. You should also report the problem to your service provider because they may be able to correct it.