한국   대만   중국   일본 
Understanding Access Points - An On-Line Tutorial
The Wayback Machine - https://web.archive.org/web/20161130213232/http://www.connect802.com//access_points.htm

802.11 Wi-Fi wireless LAN access point tutorial to aid in understanding how access points work in a WLAN system. You can buy 802.11 WLAN access points from Connect802.


CSS Mega Menu Css3Menu.com

 

 

Understanding 802.11 Wi-Fi Access Points

Connect802 can help with the selection and system design for many manufacturer's access points. We are also an authorized, value-added access point reseller for a number of major manufacturers.

If you have questions, please don't hesitate to call us today! We'll be happy to provide you with any technical explanation that you need to help you assure a successful wireless networking deployment.

An Access Point is a Wi-Fi wireless networking radio transceiver that allows an appropriately equipped computer or other wireless client device (phone, camera, barcode scanner, etc). to connect to a data network. The resulting connection functions exactly like a wired Ethernet connection.

What does an Access Point do?

An 802.11 Wi-Fi access point provides a connection between the electrical data path formed by an Ethernet cable and the RF signal data path formed by the Wi-Fi radios. In addition, access points provide a number of additional features and capabilities related to access control, data encryption, fault tolerance and network management. In essence, an access point is a translational bridge, converting the TCP/IP data packets from their 802.11 frame encapsulation format in the air to the 802.3 Ethernet frame format on the wired Ethernet network. There are some caveats to this definition but the definition provides a basic concept of what an access point does.

The IEEE 802.11 Standards

The Institute of Electrical and Electronics Engineers ( IEEE ) formed a committee in February of 1980 to set standards for Local Area Network (LAN) communication. The committee took the number "802" (because it was formed in February of 1980). Many working groups have since been formed with the IEEE 802 committee and the 802.11 working group is responsible for wireless LAN (WLAN) standards. The following is a very high-level summary of the standards that are most significant when making a Wi-Fi design or purchase decision.

802.11b This was the first widely used standard and it's found today in every HotSpot and supported by every typical notebook computer and handheld PDA. Specification says data rates can go to 11 Mbps but expect no more than 6 Mbps in practice. Interference is possible from cordless phones, microwave ovens, and wireless IP cameras.
   
802.11a This standard uses a higher frequency band than 802.11b (5.8 Ghz) but, as a consequence, is more susceptible to signal loss through walls and other obstacles. This is due to the physics of higher frequencies versus lower frequencies. Specification says data rates can go to 54 Mbps but expect no more than 25 Mbps and very often more in the range of 10-20 Mbps. 802.11a equipment tends to be more expensive than 802.11b equipment and that has resulted in less users in the 802.11a frequency range. The lack of congestion in the band is often cited as a reason to use 802.11a for backbone networks or for Voice-over-WLAN when other 802.11b devices are present.
   
802.11g In essence 802.11g uses the higher bit rate technology that lets 802.11a operate with a specified maximum bit rate of 54 Mbps but the technology is implemented in the lower frequency band used by 802.11b (2.4 Ghz). The practical throughput remains closer to the 10-27 Mbps range and the potential interference from both 802.11b and other 802.11g devices remains. 802.11g is the status quo for Wi-Fi wireless networking (supplanting 802.11b as the predominant standard).
   
802.11n Instead of being limited to 54 Mbps with an effective throughput cap of 27 Mbps, 802.11n has a connection rate up to 300 Mbps with roughly 75% of the connection rate usable for TCP/IP throughput. From a practical standpoint, an 802.11n connection should provide at least 50 Mbps of actual throughput and may provide closer to 150 Mbps (of actual TCP/IP throughput). It's unlikely that most users will be able to connect at a full 300 Mbps rate and achieve 225 Mbps of actual TCP/IP throughput. 802.11n is best suited for environments where a high user density demands maximum capacity in each coverage cell.
 

Definitions of Access Points that you might find on the Web:

  • Transceiver that connects devices on a wireless LAN to the wired infrastructure.
  • A transceiver or radio component in a wireless LAN that acts as the transfer point between wired and wireless signal, and vice versa. The AP is connected to antennas as well as to the wired LAN system.
  • A hardware device or a computer's software that acts as a communication hub for users of a wireless device to connect to a wired device
  • A WLAN transceiver that operates either as a bridge in a peer-to-peer connection or as a connector between the wired and wireless segments of the network.
  • Base station that plugs into Ethernet hub or server. Like a cellular phone system cell, users can roam between access points.
  • An interface between the wireless network and a wired network. Access points combined with a distribution system (e.g. Ethernet) support the creation of multiple radio cells (BSSs) that enable roaming throughout a facility.
  • A wireless LAN/WAN transceiver that acts as a center point of an all-wireless network or as a connection point between wireless and wired networks.
  • A wireless LAN transceiver that acts as a center point and bridges ( OSI Layer 2) between wireless and wired networks.
  • A device that acts as a central point between wireless 802.11and wired 802.3 Ethernet networks.
  • A device that transports data between a wireless network and a wired network (infrastructure). This device acts as an Ethernet Bridge which handles roaming from one microcell to another microcell
  • An internetworking device that seamlessly connects wired and wireless networks together.
  • A device that transports data between a wireless network and a wired network infrastructure. Also referred to as a base station.