SOLUTION 1: PROCEDURE SOLUTION 2: CONDITIONSAlternative 1: Switch on ciphering with following settings (this isrecommendation as per 2009 when wring this procedure):Best choice: A5/3 and A5/1 for the mobiles and BTS equipmentthat don't support A5/3Second best: A5/1Third best: NOCIPHA5/2 is not recommended

Alternative 2: Identify interfering cells and make minor configuration changesStep 1)Identify cells with high number of dropped calls because of"Sequence Errors". See trace in solution #2.*) Make sure that TSC (Training Sequence Code) is not the same for cells that could co-interfere. We recommend different TSC settings for different sectors of a site even when MAIO separation should prevent co-interference. That is, to reduce the risk for mistake at future expansion.*) Change frequency plan to avoid interference (maybe too obvious to mention).*) Use frequency hopping*) Use random hopping (avoid HSN=0)*) Use different MAIO settings for different sectors of asite when same frequencies are re-used for the different sector.*) Differentiate HSN (Hopping Sequence Number) between cells that could co-interfere.*) Add more frequencies to hop on to reduce the risk foraccidental collision.

Important: Note that even when MAIO and HSN are set in a good way there may still be accidental collisions. Especially if number of frequencies in the hopping sequence is small.

1- Use the following trace to determine if there are dropped calls due to "Sequence Error":

TEST SYSTEM;TMSIZE=32000;TELMI:LOAD=85,TI=5;TERM;CLEAR;ON VAR ROTRAN 44;ON IN RMCR RMCONRELINIT4;ON IN DO:IF DR2=4,IF DR3=8,IF DR4=7;FOR 50 TIMES;print DR16,;INIT;

2- Get the cell pointer corresponding to the cell where the error occurs (DR16 in RMCONRELINIT2).

Example:PROGRAM TRACING (1)ON INSIGRMCR DR16=H'0000 0179ENDThe cell pointer in the previous case is H'0179.

3- Get the cell name:

TEST SYSTEM;PRIN SV ROTRAN CELLPOINTER:44;end test;

4- Check all cells in the TG have the same number of frequencies, and the HSN setting is the same.

Example:<rlcfp:cell=XXXXA;CELL CONFIGURATION FREQUENCY DATACELLXXXXACHGR SCTYPE SDCCH SDCCHAC TN CCHPOS CBCH HSN HOP DCHNO0 1 0 1 TN NO 1 OFF 5961 0 0 1 TN NO 44 ON 588589602END

<rlcfp:cell=XXXXB;CELL CONFIGURATION FREQUENCY DATACELLXXXXBCHGR SCTYPE SDCCH SDCCHAC TN CCHPOS CBCH HSN HOP DCHNO0 1 0 1 TN NO 1 OFF 5901 0 0 1 TN NO 44 ON 588589602END

5- Check the MAIO settings:<rlchp:cell=XXXXA;CELL CONFIGURATION FREQUENCY HOPPING DATACELLXXXXACHGR HSN HOP MAIO0 1 OFF DEFAULT1 44 ON 0

24 ---------> TRX with MAIO = 4

END

<rlchp:cell=XXXXB;CELL CONFIGURATION FREQUENCY HOPPING DATACELLXXXXBCHGR HSN HOP MAIO0 1 OFF DEFAULT1 44 ON 4 ----------> TRX with MAIO = 4END

<rlchp:cell=XXXXC;CELL CONFIGURATION FREQUENCY HOPPING DATACELLXXXXCCHGR HSN HOP MAIO0 1 OFF DEFAULT1 44 ON 6

8END

In the example the MAIO=4 is an incorrect setting, and must be changed in sector A or B.

PROCEDURE:1- Change the incorrect MAIO setting.Example:<rlchc:cell=XXXXA,chgr=1,maio=10;RLCHC:CELL=XXXXA,CHGR=1,MAIO=10;EXECUTED2- Confirm no more dropped calls due to "Sequence Error" occur on the same cell (use the trace provided in the "CONDITIONS" section).