LevelOne WHG-1000 - Manual (Page 38)

WHG-1000 300Mbps Wireless PoE Hotspot Gateway
User's Manual
38
ACK Timeout is adjustable due to the fact that distance between two radio links may vary in different
deployment. ACK Timeout makes significant influence in performance of long distance radio link. If ACK
Timeout is set too short, transmitter will start to “Resend” packet before ACK is received, and throughput
become low due to excessively high re-transmission.
ACK Timeout is best determined by distance between the radios, data rate of average environment. The
Timeout value is calculated based on round-trip time of packet with a little tolerance, So, if experiencing re-
transmissions or poor performance the ACK Timeout could be made longer to accommodate.
Slot Time and ACK Timeout settings are for long distance links. It is important to tweak settings to achieve
the optimal result based on requirement.
 RSSI Threshold : RSSI(Received Signal Strength Indication) Threshold is in the range of -127 ~ 128. The
default value is 24. RSSI Threshold can be used to control the level of noise received by the device.
 Beacon Interval : Beacon Interval is in the range of 40~3500 and set in unit of millisecond. The default value is
100 msec.
Access Point (AP) in IEEE 802.11 will send out a special approximated 50-byte frame, called “Beacon”. Beacon
is broadcast to all the stations, provides the basic information of AP such as SSID, channel, encryption keys,
signal strength, time stamp, support data rate.
All the radio stations received beacon recognizes the existence of such AP, and may proceed next actions if the
information from AP matches the requirement. Beacon is sent on a periodic basis, the time interval can be
adjusted.
By increasing the beacon interval, you can reduce the number of beacons and associated overhead, but that
will likely delay the association and roaming process because stations scanning for available access points may
miss the beacons. You can decrease the beacon interval, which increases the rate of beacons. This will make
the association and roaming process very responsive; however, the network will incur additional overhead and
throughput will go down.
 DTIM Interval : The DTIM interval is in the range of 1~255. The default is 1.
DTIM is defined as Delivery Traffic Indication Message. It is used to notify the wireless stations, which support
power saving mode, when to wake up to receive multicast frame. DTIM is necessary and critical in wireless
environment as a mechanism to fulfill power-saving synchronization.
A DTIM interval is a count of the number of beacon frames that must occur before the access point sends the
buffered multicast frames. For instance, if DTIM Interval is set to 3, then the Wi-Fi clients will expect to receive
a multicast frame after receiving three Beacon frame. The higher DTIM interval will help power saving and
possibly decrease wireless throughput in multicast applications.