All radio frequency−based devices suffer interference problems due to other devices operating in the same frequency. When different types of devices operate in the same physical area, they may not cooperate with each other in terms of bandwidth usage.

Most wireless communication protocols require that, when they send a data packet to another wireless device, the receiving device must send an acknowledgment packet confirming the receipt of the data packet; otherwise it resends the data packet.

For example, if a wireless LAN adapter sends a data packet to an AP, the AP must reply upon successful receipt of the data packet; if the AP does not reply with an acknowledgment packet, the wireless LAN adapter keeps on retrying by retransmitting the packet.

The retransmission works under most circumstances, but if there is too much interference and data is not able to travel among the wireless LAN devices, they all become busy sending out packets and retrying, which quickly makes the wireless LAN bandwidth congested with retransmissions.

Devices that operate in the 2.4−GHz Industrial, Scientific, and Medical (ISM) unlicensed band, for example, 802.11b, are especially vulnerable to this problem. Following are some of the devices that operate in the 2.4−GHz band; their communication may disrupt the operation of an 802.11b−based wireless LAN.

• Bluetooth. Bluetooth−based wireless devices are short−distance radio devices that use 2.4−GHz band. Bluetooth devices are PDAs and small wearable electronic gadgets and require very little bandwidth, but their fast growth and RF band competition is adding a potential threat to the 802.11b wireless LANs.

• Microwave ovens. Many microwave ovens also operate in 2.4−GHz band and cause interference and bandwidth congestion in a wireless LAN.

• Cordless phones. The 2.4−GHz cordless phones are also known to disrupt the 802.11b wireless LAN operation.

The following are some of the best ways to avoid bandwidth congestion due to competing devices.

• Remove and minimize all devices that operate in the RF band of the wireless LA

• Users of the LAN should be informed that the LAN performance would be greatly degraded if they use devices that use the same bandwidth as the wireless LAN.

• Another option might be to use the 802.11a−based wireless LAN equipment. 802.11a equipment operates in the newly licensed 5−GHz band. The availability of fewer devices in the 5−GHz band makes it less vulnerable to the RF interference and bandwidth congestion.

• Additionally, you can experiment with relocating the AP and all competing devices. Switch to channel 1 or channel 11 on the access points. For example, if the computer with a wireless LAN adapter is near a cordless−phone base station, try using a card that allows you to use a remote external antenna.