Windows 7 / Networking

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Support for IEEE 802.11 Standards

Windows Vista, Windows Server 2008, Windows XP, and Microsoft Windows Server 2003 provide built-in support for 802.11 wireless LAN networking. An installed 802.11 wireless LAN network adapter appears as a wireless network connection in the Network Connections folder. Although there is built-in support for 802.11 wireless LAN networking, the wireless components of Windows are dependent upon the following:

• The capabilities of the wireless network adapter: The installed wireless network adapter must support the wireless LAN or wireless security standards that you require. For example, Windows Vista supports configuration options for the Wi-Fi Protected Access (WPA) security standard. However, if the wireless network adapter does not support WPA, you cannot enable or configure WPA security options.
• The capabilities of the wireless network adapter driver To allow you to configure wireless network options, the driver for the wireless network adapter must support the reporting of all of its capabilities to Windows. Verify that the driver for your wireless network adapter was written for the capabilities of Windows Vista or Windows XP and is the most current version by checking Microsoft Update or the Web site of the wireless network adapter vendor.

Table-1 lists the IEEE wireless standards supported by Windows and by wireless network adapters, their maximum bit rate, range of frequencies, and their typical usage.

Table-1 802.11 Standards

Standard	Maximum Bit Rate	Range of Frequencies	Usage
802.11	2 megabits per second (Mbps)	S-Band Industrial, Scientific, and Medical (ISM) frequency range (2.4 to 2.5 GHz)	Obsolete. Not widely used.
802.11b	11 Mbps	S-Band ISM	Widely used
802.11a	54 Mbps	C-Band ISM (5.725 to 5.875 GHz)	Not widely used due to expense and limited range.
802.11g	54 Mbps	S-Band ISM	Widely used. 802.11g devices are backwardcompatible with 802.11b devices.
802.11n (standards development in progress)	250 Mbps	C-Band and S-Band ISM	Pre-standard ratification devices are available starting in August 2007. 802.11n devices can be backward-compatible with 802.11a, b, and g devices.

Note: The S-Band ISM uses the same frequency range as microwave ovens, cordless phones, baby monitors, wireless video cameras, and Bluetooth devices. The C-Band ISM uses the same frequency range as newer cordless phones and other devices. Due to this overlapping use, there may be contention when multiple devices are active at the same time.

802.11 Operating Modes

Wireless LAN networks for all the IEEE 802.11 standards use the following operating modes:

• Infrastructure mode The wireless network contains at least one wireless access point (AP), a device that bridges wireless-based computers to each other and to a wired network such as the Internet or an intranet.
• Ad-hoc mode The wireless network contains no wireless APs. Wireless-based computers connect and communicate directly with each other. This tutorial does not describe ad-hoc mode wireless networks.

Regardless of the operating mode, a Service Set Identifier (SSID), also known as the wireless network name, identifies a specific wireless network. You configure the SSID on the wireless AP for infrastructure mode or the initial wireless client for ad-hoc mode. The wireless AP or the initial wireless client periodically advertise the SSID so that other wireless nodes can discover and join the wireless network.