Ans:

1. 1. Ad-hoc is a mode of wireless networking in which each wireless device communicates directly with other wireless devices in a network without an AP.
2. IBSS, or Independent Basic Service Set, is a special type of ad-hoc network, in which all clients are set to have the same Basic Service Set Identifier (BSSID) to form an independent group.
3. Infrastructure is a mode of wireless networking in which an AP is used to route transmissions between a wireless network and a wired network, or between any two wireless clients.

1. WLAN uses the following technologies to prevent data theft:
1. Direct Sequence Spread Spectrum (DSSS) provides a high degree of protection against eavesdropping and interference. This technology has long been used in the military, and has only recently been deregulated for commercial use. With DSSS, data is modulated through a special coding before transmission, and therefore is afforded a reliable security.
2. Access Control Table: In the WaveLAN security control, if Access Control Table is activated, only authorized users or computers can gain access to data on the wireless network. Even identical devices in the vicinity cannot gain access without permission.
3. Wired Equivalent Privacy (WEP): The IEEE 802.11 standard requires data encryption in the MAC layer to provide the wireless network with a level of security that is equivalent to the security found on a wired network. WEP uses a type of RC4 algorithm, which is currently used by Microsoft, Netscape, and Oracle. Due to the stringent security this technology affords, the 802.11 Working Group had selected it for the 40-bit encryption, adding to the existing DSSS technology from the military, in order to strengthen the security for the entire system.
4. Wi-Fi Protected Access (WPA) 1.0/2.0: To ensure interoperability among IEEE 802.11 products, the Wi-Fi Alliance (WFA) defined the extended security features in WPA 1.0 and 2.0.
2. There is no impenetrable computer system in the world. The question is how much time and resource is required for someone to penetrate the security system.
3. Wireless networks are generally more vulnerable to data theft than wired networks. Someone who intends to steal information over a wireless network can do so by analyzing protocols being transmitted in the air. On a wired network, however, the attacker must first find the cable before any damage can be done.

1. Your location must be within the service range of an access point (AP).
2. The wireless network card's driver must be installed and working properly.
3. Enter the user's name and password or select the IEEE 802.1X MD5-Challenge for authentication.
4. You can get online once you are successfully authenticated.

Ans:

1. The WLAN card is not installed properly.
   
2. Your computer is not within the service range of the wireless network. Try moving the computer into the service range. You can use the WLAN card's LED or its utility program to determine the signal strength.
   
3. The computer is not set to obtain automatically an Internet Protocol (IP) address through the Dynamic Host Configuration Protocol (DHCP), or it has not yet received an IP address. Please wait for a minute, or execute the "ipconfig /renew" command to obtain an IP address.

Ans: In order for the WLAN card to operate properly, three conditions must be met:

1. 1. hardware—the driver is compatible with the operating system, has been installed and configured properly, and is not in conflict with drivers of other devices;
   
2. connection—connection has been properly established; and
   
3. signal—being within range of the wireless network.
   Therefore, the probable cause of your problem might be:
   
   1. 1. the driver is not compatible with the operating system;
   2. the connection has not been properly established;
   3. there is a hardware conflict, especially with a (wired) network card; or
   4. the computer is outside the range of the wireless network, or the signals are too weak or have been distorted due to interference.