It means use Fewer BCCH frequencies in the network. Thus more frequencies can be used in
other channel groups in order to increase the Network traffic capacity,
The
capability of this feature is to make it possible to use fewer BCCH frequencies.
This is achieved by applying separate pathloss and DTCB criteria to the BCCH
CHGR. That makes it possible to use a tighter reuse than without the feature,
or to enhance the speech quality and keeping the existing reuse.
Tighter
BCCH frequency reuse is possible regardless of if subcells are used or not.
Statics Counters
are used in Tight BCCH Frequency Reuse:
BCDTCBCOM is stepped by
intra-cell handover attempt out of BCCH CHGR, BCCHDTCB
criteria.
BCLOSSCOM is stepped by
intra-cell handover attempt out of BCCH CHGR, BCCHLOSS
critera.
BCDTCBSUC is stepped by
successful intra-cell handover out of BCCH CHGR, BCCHDTCB criteria.
BCLOSSSUC is stepped by
successful intra-cell handover out of BCCH CHGR, BCCHLOSS criteria.
In
a tight BCCH re-use plan, careful planning is required in order to avoid BCCH
confusion during handover, which can have a negative impact in the performance,
particularly for fast moving MS (e.g. in highways); in this case, the mobile
initially decode the correct BSIC of the neighbor cell and will continue measuring
that frequency but won’t decode the BSIC information for every measurement
report the MS shall attempt to
demodulate the SCH on the BCCH carrier of as many surrounding cells as
possible, and decode the BSIC as often as possible, minimum at least once every
10 seconds, to confirm that it is monitoring the same cell), if both co-BCCH
cells are closely located, after
a
few seconds a fast moving mobile could be measuring a different cell (the co-channel
BCCH) but will report it incorrectly with the old BSIC (the BSIC originally
decoded from the neighbor cell) to the system. Since sometimes it’s impossible
to avoid close co-BCCH cells in a tight re-use plan, then in order to minimize
the effect of BSIC confusion, the closest co-channel BCCHs should be allocated
away from highways, preferably towards areas with low mobility MS (e.g.
residential areas).
Main Controlling Parameters
BCCHREUSE is a parameter
activating/de-activating the feature Tight BCCH Frequency Reuse, set per cell.
BCCHLOSS is a parameter
indicating maximum allowed path loss of the BCCH carrier, set per cell.
BCCHDTCB is a parameter
expressing the limit of the calculated difference in signal strength between
the BCCH of the serving cell and the strongest non-cosited neighbor cell within
the same frequency band, set per cell.
BCCHLOSSHYST is a
parameter for the hysteresis of the BCCHLOSS
parameter, set per cell.
BCCHDTCBHYST is a
parameter for the hysteresis of the parameter BCCHDTCB, set per cell.
Value
Ranges and Default Values
Parameter name
|
Default value
|
Recommended value
|
Value range
|
Unit
|
BCCHREUSE
|
0 (NORMAL)
|
0,1 (0=NORM AL, 1=TIGHT)
|
||
BCCHLOSS
|
200
|
0 to 200
|
dB
|
|
BCCHDTCB
|
-63
|
-63 to +63
|
dB
|
|
BCCHLOSSHYST
|
3
|
3 0 to 63
|
dB
|
|
BCCHDTCBHYST
|
2
|
3 0 to 63
|
dB
|