Cisco WBPN User Guide - Page 27

Using the WBPN Wireless-N Bridge for Phone Adapters Configuration Utility Configuring Wireless Parameters 2 Beacon Interval Preamble Type Protection Aggregation Short GI 20/40MHz Coexist The Beacon Interval value indicates the frequency interval of the beacon. The beacon is a packet transmitted at regular intervals from APs in order to synchronize the wireless network. The preamble is at the head or front of the Physical Layer Convergence Protocol (PLCP), which is one of the parts of the wireless physical layer. Devices use the preamble type to start transferring data. Long-The long preamble ensures compatibility with legacy 802.11b devices but can slightly reduce throughput at high data rates. Short-The short preamble reduces the header's size by 50%, down to 9 bytes. The short preamble is optional for 802.11b. The 802.11g and newer standards all support the short preamble. If you do not have 802.11b devices in your network, you can enable the short preamble for a small throughput increase. If you apply RTS/CTS flow control on the communication with wireless LAN handsets, choose Enabled to improve communication speed. If you have few wireless LAN handsets, choose Disabled. With frame aggregation, up to 64 MSDUs (MAC Service Data Units, or Layer 2 frames) can be sent at one time. This "super" frame has one physical layer header and data frames (each with its own MAC header). Once all the data has been sent, a block acknowledgment is sent. Enabling aggregation can help reduce bandwidth size by reducing the "overhead" in networks with high transmission rates, and allows higher throughput. The guard interval (GI) is the space between symbols (characters) being transmitted. The short guard interval time is 400ns, which is half of the usual GI (800ns). Enabling short GI helps throughput. Allows data to be transmitted on both the 20 MHz and 40MHz channels of the wireless LAN. Cisco WBPN User Guide 27