Symbol Technologies WS 2000 - Manual (Page 45)

WLAN—Setting Default Access Port Settings
5. Check the Antenna Diversity checkbox to enable Antenna Diversity if the Access
Port has an external antenna. Antenna Diversity should only be enabled if the Access
Port has two matching external antennas.
6. Check the Support Short Preamble checkbox to allow the Access Port to
communicate with the MUs using a short 56-bit preamble.
A preamble is the beginning part of a frame. The preamble comprises such elements as
robust carrier sensing, collision detection, equalizer training, timing recovery, and gain
adjustment. The administration can choose between a long or short preamble for data-
frame transmission from the WLAN’s adopted access ports.
Use the long preamble setting (the default) for legacy wireless equipment that is not
capable of dealing with short preambles. Use the short preamble setting where legacy
equipment is not an issue and maximum throughput is desired, for example when
streaming video or Voice-over-IP applications are used.
7. Set the Request to Send Threshold (RTS Threshold) by specifying a number.
RTS is a transmitting station’s signal that requests a Clear To Send (CTS) response
from a receiving station. This RTS/CTS procedure clears the air when many mobile
units (MUs) are contending for transmission time. Modifying this value allows the
administrator to control the number of data collisions and thereby enhance
communication with nodes that are hard to find because of other active nodes in the
transmission path.
In this field, the administrator can specify a Request To Send (RTS) threshold (in bytes)
for use by the WLAN’s adopted access ports.
This setting initiates an RTS/CTS exchange for data frames that are larger than the
threshold, and sends (without RTS/CTS) any data frames that are smaller than the
threshold.
Consider the tradeoffs when setting an appropriate RTS threshold for the WLAN’s
access ports. A lower RTS threshold causes more frequent RTS/CTS exchanges. This
consumes more bandwidth because of the additional latency (RTS/CTS exchanges)
before transmissions can commence. A disadvantage is the reduction in data-frame
throughput. An advantage is quicker system recovery from electromagnetic interference
and data collisions. Environments with more wireless traffic and contention for
transmission make the best use of a lower RTS threshold.
A higher RTS threshold minimizes RTS/CTS exchanges, consuming less bandwidth for
data transmissions. A disadvantage is less help to nodes that encounter interference and
collisions. An advantage is faster data-frame throughput. Environments with less
wireless traffic and contention for transmission make the best use of a higher RTS
threshold.
Set the Access Port beacon settings by clicking on the Beacon Settings button. The
following window appears.
Copyright © 2004 Symbol Technologies, Inc. All Rights Reserved 45
WS 2000 Wireless Switch: 1.0 Date of last Revision: March 2004