Windows XP Wireless deployment technology and component Overview

Workstation

A workstation (STA) is a computing device equipped with a wireless LAN adapter. A personal computer with a wireless LAN adapter is called a wireless client. Wireless Clients can communicate with each other directly or through wireless access points.

Wireless Clients can be moved.

Wireless Access Point

A wireless access point (AP) is a network device equipped with a wireless LAN adapter. It acts as a bridge between the STA and a traditional wired network. Access points include:

At least one interface connecting an AP to an existing wired network (for example, an Ethernet trunk line ).

A radio receiving device that establishes a wireless connection with a wireless client.

The IEEE 802.1D bridge software enables it to act as a transparent bridge between the wireless data link layer and the wired data link layer.

The Wireless AP and the base station of the cellular telephone network are similar: the wireless client communicates with the wired network and other wireless clients through the Wireless AP.

A Wireless AP cannot be moved. It acts as a peripheral bridging device to expand the wired network.

Port

The port is the channel of the device and supports a single point-to-point connection. For IEEE 802.11b, a port is a logical entity through which a single wireless connection can be established. A typical wireless client with a wireless LAN adapter has only one port and can only support a single wireless connection. A typical Wireless AP has multiple ports and supports multiple wireless connections at the same time.

The logical connection between the port on the wireless client and the port on the Wireless AP is a point-to-point bridging lan network segment, similar to the Ethernet-Based Network Client Connected to the Ethernet switch. All frames sent from the wireless client, whether unicast, multicast, or broadcast, are sent to the point-to-point lan cidr block between the wireless client and the Wireless AP. For frames sent from Wireless AP to wireless clients, unicast frames are sent to point-to-point lan cidr blocks, and multicast and broadcast frames are sent to all connected wireless clients at the same time.

IEEE 1, 802.11

IEEE 802.11 is an industry standard for shared wireless LAN (WLAN). It defines the physical layer of wireless communication and the sub-layer of Media Access Control (MAC.

802.11 Physical Layer

In the physical layer, IEEE 802.11 defines the transmission standards for Direct Sequence frequency spreading (DSSS) and frequency hopping (FHSS. The original bitrate of IEEE 802.11 is 2 Mbps and 1 Mbps, using the S-Band 2.4-2.5 GHz industrial, scientific research and medical (ISM) Band. The maximum bit rate of IEEE 802.11b is 11 Mbps (using DSSS ). The maximum bit rate of IEEE 802.11a is 54 Mbps. It uses orthogonal frequency division multiplexing (OFDM) and C-Band 5.725-5.875 GHz ISM Band.

802.11 MAC Sub-Layer

On the MAC Sub-layer, IEEE 802.11 uses the guaranteed-performance multi-channel access (CSMA/CA) Media Access Control (MAC) protocol. The method is as follows:

The wireless workstation to transmit Frames first listens to the wireless channel to determine whether another workstation is in transmission (carrier listening ). If the media is in use, the wireless workstation calculates the random latency. The wireless workstation can listen to the transmitting workstation again only after the random delay time. Before the random delay starts, multiple workstations waiting for transmission will not end the transmission attempt at the same time (to avoid conflict ).

The CSMA/CA solution cannot ensure that conflicts do not occur, and it is difficult for transmission nodes to detect conflicts. In addition, the radio frequency (RF) barrier may prevent wireless clients from listening to other wireless nodes based on the location of Wireless AP and wireless client. This problem is known as a hidden workstation problem.

To provide better conflict detection and solutions for hidden workstation problems, IEEE 802.11 also defines the use of ACK frames to indicate that wireless frames have been successfully received, and the use of request sending (RTS) and clear sending (CTS) messages. When a workstation transmits a frame, it sends an RTS message indicating the time required to send the frame. A Wireless AP sends a CTS message to all workstations, grants a license to the requesting workstation, and notifies all other workstations that they are not allowed to be transmitted within the scheduled time of the RTS message. The exchange of RTS and CTS messages eliminates conflicts caused by hidden workstation problems.

1. How to deploy 802.1X in Windows XP
2. Wireless LAN technology and Windows XP
3. In-depth analysis of wireless technology rational selection of wireless products