Ubiquiti AF-2X User Manual

Also see for AF-3X: User guide User guide User guide Quick start guide

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Ubiquiti AF-2X User Manual Manual pdf 46 page image

40Appendix B: Listen Before Talk airFiber® X User GuideUbiquiti Networks, Inc.Opportunities for Other Transmittersto OperateNo differences are performed between start-up modeand operational mode. The Master/Slave device goesinto an energy scanning mode where it is allowed to doone full cycle of energy detection before it is allowed totransmit. The scan is a mode where the average energyis accumulated to compare against the programmeddetection threshold. If the energy detected is less than thedetection threshold, the Master/Slave device is allowed tomake a transmission.In normal operational mode the system does not allowany transmission once the threshold has been detected.Once the energy is no longer present will the systembegin to transmit again.The Master and Slave uses the energy detected prior toeach transmit frame to control the muting of the transmitfunction.At any load level (no load, typical, or overload), thesystem transmits data based on the configuration for theuplink/downlink ratio The same amount of bandwidth isreserved for channel detection, so performance remainsunaffected.If there are two AF-3X systems on a co-channel, theywould share the spectrum as follows:• Since the system is a synchronized frame-based system,both systems would operate effectively with each otherbecause each system can be configured to transmit andreceive at the same point in time. The system uses aGPS synchronization to time-align the start-of-frame forall systems deployed.• If the users configure the number of uplink anddownlink slots and the duty cycle (uplink/downlinkratio) in an identical manner and each system uses thesame set of uncommitted uplink slots for the detectionsampling interval, then the two systems will co-existwith no knowledge of the others presence.• Each system listens prior to transmit and if it detectsactivity yields to the other system.• The system will shut down when the accumulatedenergy is above the detection threshold and willcontinue to transmit if it is below the detectionthreshold. When the co-channel system is clear of thechannel then the target system will go back into regularoperation. Regular operation will consist of a constantaveraging of the energy detected in the uplink slots.