Rts/Cts

User Manual

TEW-455APBO High Power Wireless Outdoor PoE Access Point

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.

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.