GSM Radio Network Features
Slide
Intra Cell Handover
03813-LZU 108 3704 Uae Rev E
Slide
GSM Radio Network Features
1 (1 (14)
Intra-Cell Handover • A chann channel el chang change e within within the cell cell in situatio situations ns of bad quality and high signal strength.
Bad quality despite of high signal strength
f1
A
f2
03813-LZU 108 3704 Uae Rev E
03813-LZU 108 3704 Uae Rev E
Slide
2 (1 (14)
GSM Radio Network Features
1
GSM Radio Network Features
Slide
Achievements • Intra-cell handover can solve temporary co- and adjacent channel interference as well as intermodulation problems. • Permanent interference and time dispersion cannot be solved.
03813-LZU 108 3704 Uae Rev E
Slide
3 (14)
GSM Radio Network Features
Graphic display of the FQSS Table
03813-LZU 108 3704 Uae Rev E
03813-LZU 108 3704 Uae Rev E
Slide
4 (14)
GSM Radio Network Features
2
GSM Radio Network Features
Slide
The Intra-Cell Handover Criteria The intra-cell handover algorithm states that an intra-cell handover shall be requested if: – rxqual-ul > QOFFSETUL + FQSS( RXLEV_UL + SSOFFSETUL )
or – rxqual-dl > QOFFSETDL + FQSS( RXLEV_DL + SSOFFSETDL )
RXLEV_UL/DL is the received filtered UL/DL values of the signal strength rxqual_ul/dl is the received filtered quality values UL/DL
03813-LZU 108 3704 Uae Rev E
Slide
5 (14)
GSM Radio Network Features
The Intra-Cell Handover Criteria for AMR FR The intra-cell handover algorithm for AMR FR states that an intra-cell handover shall be requested if: – rxqual_ul > QOFFSETULAFR + FQSS(RXLEV_UL+SSOFFSETULAFR)
or – rxqual_dl > QOFFSETDLAFR + FQSS(RXLEV_DL+SSOFFSETDLAFR)
where: SSOFFSETULAFR and SSOFFSETDLAFR are signal strength offset parameters, which shift the curve in the hor izontal direction for the case when traffic using AMR FR transcoder QOFFSETULAFR and QOFFSETDLAFR are quality offset parameters, which shift the curve in the vertical direction for the case when traffic using AMR FR transcoder.
03813-LZU 108 3704 Uae Rev E
03813-LZU 108 3704 Uae Rev E
Slide
6 (14)
GSM Radio Network Features
3
GSM Radio Network Features
Slide
FQSS Table RXLEV <=30 31 32 - 35 36 - 38 39 - 41 42 - 45 46 - 48 49 - 52 53 - 55 56 - 58 59 - 62 >=63 03813-LZU 108 3704 Uae Rev E
Slide
rxqual infinity 60 59 58 57 56 55 54 53 52 51 50 GSM Radio Network Features
7 (14)
Selection of a new Channel In the traffic case intra-cell handover, it is important to find channels with characteristics that differ compared to the characteristics of the originating channel. 1.
The group of idle channels according to the following intra-cell handover strategy is selected. Note that it is possible to go from non-hopping channels to hopping channels, and vice versa. With frequency hopping:
Without frequency hopping:
2.1 Among the groups of idle channels, select the ones
2.1 Among the idle channels, select the ones
that belong to another channel group than t he
that are on a different frequency than the
current channel.
current channel.
2.2 If no idle channels have been found with the
2.2 If no idle channels have been found with
criterion above, (e.g. there are only one channel
the criterion above, select the idle timeslots
group defined in the cell), select t he idle channels
that are on the same frequency as the
in that channel group, but with different timeslot
current channel, but with different timeslot
numbers than the current channel.
numbers than the current channel.
2.3 If no idle channel has been found with the criteria above, select the idle channels on the same channel group and timeslot as the current channel.
3.
Continue the selection as stated in chapter Channel Administration at TCH Channel selection for single slot connection. 03813-LZU 108 3704 Uae Rev E
03813-LZU 108 3704 Uae Rev E
Slide
8 (14)
GSM Radio Network Features
4
GSM Radio Network Features
Slide
Channel Allocation at Intra-Cell Handover Non - hopping cell: First choice at IHO (change of frequency)
f 1 f 2
Last choice at IHO (same frequency but different timeslot)
f 3 allocated channel
Hopping cell: f 1
First choice at IHO (change of channel group) Second choice at IHO (change of timeslot)
f 2 f 3
Last choice at IHO (same channel group and timeslot)
f 4 allocated channel 03813-LZU 108 3704 Uae Rev E
Slide
GSM Radio Network Features
9 (14)
IHO Timers and Counters
TMAXIHO starts
TMAXIHO starts TMAXIHO starts
4th iho attempt
TMAXIHO starts
Iho inhibited Ihoc = 1 Ihoc = 2 Ihoc = 3Ihoc = 0
TINIT starts
TINIT starts
TINIT starts
Ihoc = 1 time
TINIT starts TIHO starts
Iho = Intra-cell handover Ihoc = Intra-cell handover counter MAXIHO = 3
•TMAXIHO is the maximum time between intra-cell handovers, which are considered consecutive. The parameter is set per subcell. • MAXIHO is the maximum number of allowed consecutive intra-cell handovers. The parameter is set per subcell. • TIHO is a timer during which intra-cell handover is inhibited. This timer will not start before TINIT has elapsed. The parameter is also used when inhibiting a subcell change from an underlaid to an overlaid subcell. The parameter is set per subcell. 03813-LZU 108 3704 Uae Rev E
03813-LZU 108 3704 Uae Rev E
Slide
10 ( 14)
GSM Radio Network Features
5
GSM Radio Network Features
Slide
Interactions with OL/UL Subcells • A subcell change, from OL to UL or UL to OL, due to Intracell handover may be attempted if MAXIHO has been reached. The prerequisites are: – the criteria for intra-cell handover is fulfilled – the TINIT timer has elapsed and the TMAXIHO timer is still running
• In case of congestion, a subcell change may occur: – If congestion occurs in the overlaid subcell, a subcell change to the underlaid subcell is attempted. – If congestion occurs in the UL subcell, it is possible to allow a subcell change due to intra-cell handover, by choosing CHAP 5, 6, 8 or 10.
03813-LZU 108 3704 Uae Rev E
Slide
11 ( 14)
GSM Radio Network Features
Parameter Summary (I) • SSOFFSETUL sets the offset to the signal strength in the uplink direction • SSOFFSETULAFR sets the offset to the signal strength in the uplink direction for traffic using the AMR FR codec type • SSOFFSETDL sets the offset to the signal strength in the downlink direction • SSOFFSETDLAFR sets the offset to the signal strength in the downlink direction for traffic using the AMR FR codec type • QOFFSETUL sets the quality offset in the uplink direction • QOFFSETULAFR sets the quality offset in the uplink direction for traffic using the AMR FR codec type • QOFFSETDL sets the quality offset in the downlink direction. • QOFFSETDLAFR sets the quality offset in the downlink direction for traffic using the AMR FR codec type 03813-LZU 108 3704 Uae Rev E
03813-LZU 108 3704 Uae Rev E
Slide
12 ( 14)
GSM Radio Network Features
6
GSM Radio Network Features
Slide
Parameter Summary (II) •
IHO is the parameter to switch intra-cell handover on/off. The parameter is set per BSC. This parameter is however not considered in case of an intra-cell handover due to channel rate change.
• IHOSICH switches intra-cell handover on signaling channels on/off • TMAXIHO is the maximum time between intra-cell handovers, which are considered consecutive • MAXIHO is the maximum number of allowed consecutive intra-cell handovers • TIHO is a timer during which intra-cell handover is inhibited after having performed too many consecutive intra-cell handovers. The parameter is also used when inhibiting a subcell change from an underlaid to an overlaid subcell • HNDSDCCH determines if intra-MSC handover on a signaling channel is allowed (= 1) or not (= 0). 03813-LZU 108 3704 Uae Rev E
Slide
GSM Radio Network Features
13 ( 14)
Parameters Parameter name
Default value
Recommended value
Value range
1
1
0, 1
HNDSDCCH IHO
Unit
OFF
ON
ON, OFF
SSOFFSETUL
0
-10
-30 to 30
dB
SSOFFSETULAFR
0
-10
-30 to 30
dB
SSOFFSETDL
0
0
-30 to 30
dB
SSOFFSETDLAFR
0
0
-30 to 30
dB
QOFFSETUL
0
-50 to 50
dtqu
-50 to 50
dtqu
-50 to 50
dtqu
-50 to 50
dtqu
freq. hop: 0 no freq. hop: -10
QOFFSETULAFR
0
freq. hop: 10 no freq. hop: 0
QOFFSETDL
0
freq. hop: 10 no freq. hop: 0
QOFFSETDLAFR
0
freq. hop: 20 no freq. hop: 10
TMAXIHO
6
MAXIHO
3
7
0 to 60
TIHO
10
10
0 to 60
OFF
OFF
ON, OFF
freq. hop: 2
seconds
0 to 15
no freq. hop: 3 IHOSICH
03813-LZU 108 3704 Uae Rev E
03813-LZU 108 3704 Uae Rev E
Slide
14 ( 14)
seconds
GSM Radio Network Features
7
