Cisco WBPN User Manual page 27

Using the WBPN Wireless-N Bridge for Phone Adapters Configuration Utility
Configuring Wireless Parameters
Cisco WBPN User Guide
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. 1 1b 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. 1 1b. The 802. 1 1g and newer standards
all support the short preamble. If you do not have
802. 1 1b 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.
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