TCHDrop reason (1)The classification ofTCHDrop Reasons are arranged in the order of priority:1.Excessive Timing Advance2.Low Signal Strength3.Bad Quality4.Sudden Loss of Connection5.Other Reasons

Excessive Timing AdvanceTheTCHDrop counters due to Excessive Timing Advance will pegged when the during the time of disconnection, the last Timing Advance valuerecordedwas higher than the TALIMParameter. This drop reason is commonly apparent to isolated or island sites with a wide coverage area.Action:Check if the cellparameterTALIM is < "63"Solution:Set TALIM to a value close to 63.Tilt antenna/reduce antenna height/output power, etc. for co-channel cells.

TCHDrop Reasons (2)Low Signal Strength on Down or Uplink or Both LinksThedropscounters due to Low Signal Strength will be pegged when the Signal Strength during the last MeasurementReportbefore the call dropped is below the LOWSSDL and/or LOWSSUL Thresholds. LOWSSDL and LOWSSUL are BSCExchange Propertyparameterswhich is used only for statistics purposes and does not affect the behavior of calls. If both UL and DL Signal Strength are below the thresholds, only Drop due to Low SS BL will pegged. Normally a call is dropped at the border of large rural cell with insufficient coverage. Bad tunnel coverage cause many dropped calls as well as so called coverage holes. Bad indoor coverage will result in dropped calls. Building shadowing could be another reason.Visit Out Forum For more Optimization Tips

Action:Check coverage plots.Check output power.Check powerbalanceand link budget.Check if Omni site.Check antenna configuration & type.Check antenna installation.Perform drive tests &site survey.Check TRX/TS with high CONERRCNT.

Solution:Add a repeater to increase coverage in for example a tunnel.Change to a better antenna (with higher gain) for the base station.Add a new base station if there are large coverage holes.Block/Deblock TRX

TCHDrop Reasons (3)Poor Quality on Down or Uplink or Both LinksThedropscounters due to Bad Quality will be pegged when the Signal Strength during the last MeasurementReportbefore the call dropped is above the BADQDL and/or BADQUL Thresholds. BADQDL and BADQUL (expressed in DTQU) are BSCExchange Propertyparameterswhich is used only for statistics purposes and does not affect the behavior of calls. If both UL and DL Quality are above the thresholds, only Drop due to BAD Quality BL will pegged.Problem on Bad Quality is usually associated with Co-channel Interference on BCCH orTCH. Faulty MAIO assignment can cause frequency collisions on co-sited cells especially on 1x1 Reuse. External interference is also one possible cause of problem on quality.If you like this than Become our Friend on Facebook Click HereAction:Check C/I and C/A plots.Check Frequency Plan (Co-BCCH or Co-BSIC Problem).Check MAIO, HOP, HSNparameters.Check FHOP if correctly configured (BB or SY).Check for External Interference.Perform drive tests.