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This visualization shows what format of of 802.11 frames (also called packets) is being used in the given WLAN area. Wi-Fi networks use three frame formats:
| § | Non-HT: This is a legacy frame format used by 802.11 a/b/g equipment that is not based on the latest 802.11n standard, in which a new High Throughput (HT) format was introduced. |
| § | HT-mixed: This is a new frame format introduced in the 802.11n standard. It uses a protection mechanism that allows 802.11n devices to coexist with legacy 802.11 a/b/g devices, including those that do not belong to your WLAN. |
| § | HT-Greenfield: This is a new frame format introduced in the 802.11n standard, too. Unlike in HT-mixed mode, devices operating in Greenfield mode assume that there are no legacy 802.11 a/b/g stations around using the same or adjacent channels. 802.11 a/b/g devices cannot communicate with Greenfield devices. Rather, their packets will collide, causing problems for both parties. |
Frame format is shown for the AP that has the strongest signal in the given map area among the APs selected for analysis. This mimics the roaming behavior of client adapters that connected to the strongest AP. While other audible APs may use other frame formats, a typical adapter will connect to the AP with the strongest signal. You can deselect one or several of the selected APs to see frame formats for less strong APs.
Among the three frame formats, the best throughput is provided by HT-Greenfield. In HT-mixed format, protection mechanisms that ensure coexistence with legacy equipment reduce throughput. However, it should be noted that as per the 802.11n standard, support for HT-Greenfield frame format is not mandatory, and currently, few APs support it.
Double-clicking on the Frame Format legend on the status bar allows you to configure the color scheme and change its value range.
Suggested Solutions
If you do not see the frame formats that you expect to see, the following solutions are suggested:
| § | Check your AP configuration. If you are using newer 802.11n equipment, see if Greenfield mode is available, if HT-Greenfield frame format is what you want. Note that some APs have the “802.11n only” option, but this option does not necessarily mean that HT-Greenfield frame format will be used. Rather, switching this option on may simply disable legacy data rates. |
| § | Your AP's ability to send frames in HT-Greenfield format depends on the wireless environment. A Greenfield-enabled AP may fall back to HT-mixed format in some situations (e.g., when a non-802.11n device connects to the AP or when other non-Greenfield APs are detected nearby). Because of the changing environment, the site survey results regarding the frame format may change from time to time. Perform site surveys regularly. |
| § | If you are using legacy 802.11 a/b/g equipment, consider upgrading to 802.11n. |
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