TRENDnet 14dBi User Manual page 25

ACK Timeout: ACK timeout is in the range of 1~372 and set in unit of microsecond. The default value is 48

microsecond. All data transmission in 802.11b/g request an "Acknowledgement" (ACK) send by receiving
radio. The transmitter will resend the original packet if correspondent ACK failed to arrive within specific
time interval, also refer to as "ACK Timeout".
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 throughputs
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.
RTS/CTS
Adjustment of RTS Threshold can be done to turn on RTS. CTS Timeout will take effect only when RTS is turned
on.
Unlike wired Ethernet, radio transmission may begin with a RTS (Request to Send) frame, and receiver
responds with a CTS (Clear to Send) frame. The RTS/CTS mechanism is called Channel Cleaning, all stations that
received CTS will back off for certain period of time, multiple of the slot time.
Each CTS packet has a NAV (Network Allocation Vector) number n, the channel is reserved for sender and
receiver for additional n-millisecond. The NAV guarantees the channel is free of interference in next n-
millisecond. The last packet of ACK will set NAV to zero, indicated that connection is done and free the channel
to others.
CTS Timeout: CTS Timeout is in the range of 1~744 and set in unit of microsecond. The default value is 48

microsecond.
CTS Timeout will take effect only when RTS is turned on. Adjustment of RTS Threshold can be done to turn
on RTS. When hidden wireless stations are present in the wireless network RTS can be considered to turn
on to minimize collisions and increase performance. Ensure CTS timeout is long enough to avoid frequent
re-transmission of RTS.
Slot Time and ACK/CTS Timeout settings are for long distance links. It is important to tweak settings to achieve the optimal
result based on requirement. The device's default settings should be sufficient for most applications.
TEW-455APBO High Power Wireless Outdoor PoE Access Point
22
User Manual