8/11/2019 1789-03
1/8
SiemensTrainin Centerfor C ommunicationNetworks
Overload Handling
Objectives
The participant is able to
explain the overload control mechanisms
Contents
1 Introduction
2 Timer Control of Overload Reduction
3 Overload Detection and Counter Measures
A3 1!1"#1$!%"# &" 1"$'3( 3 " 1
8/11/2019 1789-03
5/8
SiemensTrainin Centerfor C ommunicationNetworks
$ Timer Control o Overload %eduction
hen *ettin* informed on an overload situation in a -T.= in the
M.C or in the -.C itself=the -.C performs the :rst step for tra)c
reduction and starts t6o timers T1$ and T1!6ith T1! E T1$0
Durin* run time of T1$ all overload messa*es 6ith the same cause
as the initialiFin*messa*e are i*nored in order not to reduce the
tra)c too rapidl+0
If the overload situation is still present after expir+ of T1$=
but durin* runtime of T1!= thenext step of tra)c reduction is
initiated and T1$ and T1! are started a*ain0 This step b+step
reduction of tra)c is maintained until the maximum reduction is
obtained arrivin*at the last step0
If time T1! expires ,i0e0 no overload messa*e is received/= the
-.C increases the tra)cb+ one step ,i0e0 stops the tra)c reduction
measure of the last step/ and restarts timer
T1!0 This increment 6ill continue until full load has been
resumed0
A3 1!1"#1$!%"# &" 1"$'3( 3 " (
8/11/2019 1789-03
7/8
SiemensTrainin Centerfor C ommunicationNetworks
& Overload Detection and Counter Measures
'TS Overload Handling
no TCJ available call re ected ,in future release; Lueuin* and
directed retr+= i0e0servin* the call b+ a suitable nei*hbor
cell/
no .DCCJ available
re ection b+ immediate assi*nment re ect messa*e= ne6access is
barred for a certain time ,timer T3122/
A9CJ overload ,i0e0 -. is not able to for6ard immediate
assi*nment or immediateassi*nment re ect messa*es/0 1st step; -.C
barrs the :rst half of access classes of that cell 2nd step; -.C
barrs the second half of access classes of that cell
CJ overload; CJ overload is detected 6hen the free bu er space
in the -T. forpa*in* messa*es is Fero or belo6 a threshold ,*iven
b+ the parameter,CCCJ BOAD TJR?.J//0 Then the -.C is periodicall+
,period *iven b+ parameterCCCJ BOAD I D ?RIOD/ informed on the
current load on the CJ0 The reaction ofthe -.C is pa*in*s for the
concerned -T. are discarded and the M.C is noti:ed0
'SC Overload Handling
-.C overload is detected 6hen
the Tx bu ers of the CC.$ lin s are con*ested
the percenta*e of bus+ ,level 3/ re*isters to handle incomin*
call reLuests is above athreshold ,% N/
The real time processor load of the telephon+ processor TD C is
above a certainthreshold set b+ the O M parameter OPB.TTJR0 .endin*
of overload messa*es isstopped 6hen the load is belo6 a second
parameter OPB? TJR 6ith OPB? TJR HOPB.TTJR0
hen -.C overload is detected= the follo6in* steps for tra)c
reduction are performed
1st step; the -.C barrs the :rst half of access classes in a
*roup of cells2nd step; the -.C barrs all access classes in that
*roup of cells3rd step; -.C performs step 1 and 2 for the next
*roup of cells&th step; 000 ,and so on till the overload
situation disappears/
ithin the tra)c reduction al*orithm= a round robin mechanism is
used0 This means iffor counteractin* one overload situation= cells
1 to & had been barred and the overloadends= the & cells
are unbarred0 If an overload situation occurs a*ain= the
overloadhandler starts barrin* from the (th cell and not from the
:rst one0
A3 1!1"#1$!%"# &" 1"$'3( 3 " $
