Embed Size (px)
Citation preview
All
right
s re
serv
ed. P
assi
ng o
n an
d co
pyin
g of
this
docu
men
t, us
e an
d co
mm
unic
atio
n of
this
con
tent
s no
tpe
rmitt
ed w
ithou
t writ
ten
auth
oriz
atio
n fr
om A
lcat
el
©Re
serv
ados
todo
s os
dire
itos.
A c
ópia
ou
a en
trega
des
tedo
cum
ento
a
terc
eiro
s,
bem
co
mo
o us
o ou
a
com
unic
ação
do
seu
cont
eúdo
, nã
o sã
o pe
rmiti
dos
sem
auto
rizaç
ão e
scrit
a da
ALC
ATE
L PO
RTU
GA
L SA
Edition 01
Date 16 Oct 2003
Originators Nuno MARQUES, MND/DE [email protected] Alcatel Portugal
Approval Ricardo Dinares, MND/DE [email protected] Alcatel Portugal
3DF 01902 2060 UAZZA 1 / 16
QUALITY OF SERVICE REPORTQOS_031016
Frequency Hopping Optimization - TMN Network – Portugal -
Comparing Reuse1 with
Reuse3 / Discrete Hopping / Baseband Hopping
Results / Methods / Tools
All
right
s re
serv
ed. P
assi
ng o
n an
d co
pyin
g of
this
docu
men
t, us
e an
d co
mm
unic
atio
n of
this
con
tent
s no
tpe
rmitt
ed w
ithou
t writ
ten
auth
oriz
atio
n fr
om A
lcat
el
©Re
serv
ados
todo
s os
dire
itos.
A c
ópia
ou
a en
trega
des
tedo
cum
ento
a
terc
eiro
s,
bem
co
mo
o us
o ou
a
com
unic
ação
do
seu
cont
eúdo
, nã
o sã
o pe
rmiti
dos
sem
auto
rizaç
ão e
scrit
a da
ALC
ATE
L PO
RTU
GA
L SA
3DF 01902 2060 UAZZA Edition 01 RELEASED 2 / 16
SUMMARYA frequency planning optimization was performed in TMN network in Portugal in 2003, as part of a globalprogram for voice quality improvement.A comparison of Reuse1 with Reuse3, Discrete Hopping and Baseband hopping strategies is shown on thisreport. The later strategy allowed a global Quality of Service improvement: SDCCH drop (1.1% à 0.8%;improvement of 27%), RTCH assign fail rate (0.5% à 0.3%; improvement of 40%), call-droprate (1.2% à 1.0%; improvement of 17%), and handover success rate 96.8% à 97.5%(improvement of 22%). Globally, the revenue lost in the network due to radio interferenceswas reduced by 25%.An innovative approach for creating the frequency plan was followed, by using a tool chain including SONAR,a tool based on field measurements (BSS Type180 counters). A description of the use of the tool is alsopresented.
All
right
s re
serv
ed. P
assi
ng o
n an
d co
pyin
g of
this
docu
men
t, us
e an
d co
mm
unic
atio
n of
this
con
tent
s no
tpe
rmitt
ed w
ithou
t writ
ten
auth
oriz
atio
n fr
om A
lcat
el
©Re
serv
ados
todo
s os
dire
itos.
A c
ópia
ou
a en
trega
des
tedo
cum
ento
a
terc
eiro
s,
bem
co
mo
o us
o ou
a
com
unic
ação
do
seu
cont
eúdo
, nã
o sã
o pe
rmiti
dos
sem
auto
rizaç
ão e
scrit
a da
ALC
ATE
L PO
RTU
GA
L SA
3DF 01902 2060 UAZZA Edition 01 RELEASED 3 / 16
REFERENCES
[1] F. Colin, “Radio Frequency Hopping – Implementation Strategy”, ed. 2, (3DF 00976 0001 TQZZA);
INDEX
1 INTRODUCTION ........................................................................................................................ 4
2 TMN NETWORK......................................................................................................................... 4
3 FREQUENCY HOPPING STRATEGY: RESULTS OF OPTIMIZATION............................................. 5
3.1 Frequency hopping strategies.......................................................................................... 5
3.2 Field-trial: Reuse3 ............................................................................................................ 6
3.3 Field-trial: Discrete Hopping............................................................................................ 9
3.4 Field-trial: Baseband Hopping ...................................................................................... 11
4 USING THE SONAR TOOL ....................................................................................................... 14
4.1 Outline of the SONAR tool.............................................................................................. 14
4.2 Workflow with SONAR.................................................................................................... 15
4.3 Advantages of SONAR.................................................................................................... 16
All
right
s re
serv
ed. P
assi
ng o
n an
d co
pyin
g of
this
docu
men
t, us
e an
d co
mm
unic
atio
n of
this
con
tent
s no
tpe
rmitt
ed w
ithou
t writ
ten
auth
oriz
atio
n fr
om A
lcat
el
©Re
serv
ados
todo
s os
dire
itos.
A c
ópia
ou
a en
trega
des
tedo
cum
ento
a
terc
eiro
s,
bem
co
mo
o us
o ou
a
com
unic
ação
do
seu
cont
eúdo
, nã
o sã
o pe
rmiti
dos
sem
auto
rizaç
ão e
scrit
a da
ALC
ATE
L PO
RTU
GA
L SA
3DF 01902 2060 UAZZA Edition 01 RELEASED 4 / 16
1 INTRODUCTION
This report describes the operations and methods used for frequency hopping optimization in TMN Network(Portugal) in 2003.The voice quality issue is performing an increasing role in the assessment of the network’s quality in thecompetitive Portuguese mobile panorama. In this scenario, a set of operations was performed by Alcatel toimprove the global QoS. These operations included parameter tuning and a review of the frequency hoppingstrategy. This reports focuses on the latter, giving special emphasis to the use of the tools (SONAR tool).The main objective of these frequency optimization operations, leading to an improvement of the global voicequality, was to improve KPI by reducing the overall interference in the network.To this end, several frequency hopping strategies were tested. The evaluation was done both by traditionalQoS indicators analysis and drive-tests and by Voice Quality assessment campaigns (by using Qvoice tool).(extensive tests of parameter modifications were also done for these purposes, although its description andconclusions are not analyzed on this report).
2 TMN NETWORK
This section gives a short description of the TMN network.
LISBOA
Figure 1: TMN network: Alcatel turnkey area (GSM cells in black; DCS in red)
• 19 BSC with 1400 cells (urban and rural areas)• Dual-band network (28% of DCS cells installed on a traffic-needed basis)• Some high sites due to historical and topographic conditions• Azimuths with regular pattern with exceptions• Area controlled in the regime of turnkey to Alcatel team.
Frequency policy (before these optimization operations):• In GSM900: 21 frequencies for BCCH; 18 frequencies in RFH Reuse1• In DCS1800: 14 frequencies for BCCH; 16 frequencies in RFH Reuse1• Number of TRX per cell theoretically planned to allow less than 12% of Rfload (this rule is not
followed in many cases – see below)
All
right
s re
serv
ed. P
assi
ng o
n an
d co
pyin
g of
this
docu
men
t, us
e an
d co
mm
unic
atio
n of
this
con
tent
s no
tpe
rmitt
ed w
ithou
t writ
ten
auth
oriz
atio
n fr
om A
lcat
el
©Re
serv
ados
todo
s os
dire
itos.
A c
ópia
ou
a en
trega
des
tedo
cum
ento
a
terc
eiro
s,
bem
co
mo
o us
o ou
a
com
unic
ação
do
seu
cont
eúdo
, nã
o sã
o pe
rmiti
dos
sem
auto
rizaç
ão e
scrit
a da
ALC
ATE
L PO
RTU
GA
L SA
3DF 01902 2060 UAZZA Edition 01 RELEASED 5 / 16
• BCCH frequencies chosen cell-per-cell. The traditional method has used drive-tests, extensiveknowledge of field conditions, A955 for coverage estimation (mainly on rural areas) and Pianotool.
• The network presents a high RFload due to excessive number of TRX per cell, especially on urbanareas:
Band % cells with more TRX than recommendedGSM900 45% of cells have more TRX than recommended (for Rfload < 12%)DCS1800 85% of cells have more TRX than recommended (for Rfload < 12%)
Table 1: Excessive number of TRX per cell in TMN network
Data from drive-tests show that RxQual in hopping TRX is worse that RxQual in BCCH:
BCCH/Hop % bad RxQualBCCH (RxQual > 4) 10.4%
Hopping (RxQual > 5) 13.0%
Table 2: RxQual in BCCH and TCH bands (data from drive-tests)
3 FREQUENCY HOPPING STRATEGY: RESULTS OF OPTIMIZATION
The aforementioned figures, together with the need to improve voice quality as measured by the operator withtools like Qvoice, prompt us for a review of the strategy used for hopping.
3.1 Frequency hopping strategies
As an outcome of several technical discussions, the following strategies were elaborated:
1. Reuse 3: use reuse3 instead of reuse1. For this we divide hopping band in 3 separate parts (other optionwould be to use some frequencies for 2 parts simultaneously).
2. Discrete hopping: a configuration like Synthesized FH but where the number of frequencies to hop is small,or equal to the number of TRX in hopping).
3. Baseband hopping
Other ideas were elaborated but were not tested:
• Configure some TRX from high sites, or from cells with many TRX, to use fixed frequencies in the "BCCHband", possibly using concentric cells.
• Increase hopping band, reduce BCCH band.
• Interleave BCCH frequencies with hopping frequencies. In this way we can possible reduce adjacent-channelinterference (although this is not obvious). This is more interesting if operator accepts to reduce the "BCCHband" and increase the number of frequencies for hopping (bcch plan will become easier, since there is notlimitation of using 2 adjacent frequencies in two sectors). More information on QoS results using thistechnique can be found within the team of Alcatel Shanghai Bell (Jilin MCC Network).
• Split the TCH band in two sub-bands and use TRX_prefmark to give preference to TRX in the most cleanedband; only in busy hour the TRX with the not-so-cleaned band would be used (not a sufficient solution forTMN, as metrics are computed for busy-hour).
• Use multiband cells to reduce RFload in DCS band by using it completely for hopping (not a good solution inB6 as many new RACKs would be necessary).
All
right
s re
serv
ed. P
assi
ng o
n an
d co
pyin
g of
this
docu
men
t, us
e an
d co
mm
unic
atio
n of
this
con
tent
s no
tpe
rmitt
ed w
ithou
t writ
ten
auth
oriz
atio
n fr
om A
lcat
el
©Re
serv
ados
todo
s os
dire
itos.
A c
ópia
ou
a en
trega
des
tedo
cum
ento
a
terc
eiro
s,
bem
co
mo
o us
o ou
a
com
unic
ação
do
seu
cont
eúdo
, nã
o sã
o pe
rmiti
dos
sem
auto
rizaç
ão e
scrit
a da
ALC
ATE
L PO
RTU
GA
L SA
3DF 01902 2060 UAZZA Edition 01 RELEASED 6 / 16
3.2 Field-trial: Reuse3
3.2.1 Description
Reuse3 is theoretically suitable in areas where the coverage of cells is well controlled (as for Reuse1), so thatspill-overs are not significant, and where there is a regular pattern. On these conditions, the TCH frequencyband can be split in 3 groups. Each group will then be assigned to sectors pointing in the same direction.Starting by classifying each sector in one of 3 categories according with its direction, consider the followingfigure:
F
DE
A
C B
It is easy to understand that if the cells coverage is well controlled, cell A will perform more handovers to cell Dand E, and not so many to cell F. This also means that there can be a gain if frequency groups of cells A andD and E are different, even if the frequency group of A is equal to that of F.
3.2.2 Motivation
The main motivation was that the network presents a regular pattern (although with many exceptions), andthat coverage has been tuned cell-by-cell, through years of optimization.The BSC chosen for this test, QuintaConde, a rural BSC, follows this profile. An analysis was made concerningthe percentage of handovers (using T180 counters) between each sector and other sectors belonging to thesame category (excluding intra-site sectors, where there is no interference even in Reuse1 due to MAIOchoice). In this way, this BSC presented 28.9% of handovers between sectors pointing to the same directions.Note that the lower this value is, the better it is to apply Reuse3. If this value would be 33.3%, theoretically,there would be no advantage in using Reuse3. Although this value was not as low as desired, the Reuse3 field-trial was carried out.
3.2.3 Description of operation
Date Description1/Abr/2003 BSC frozen for hardware and parameter modifications.
4/Abr/03 à 5/Abr/03 Reuse1 à Reuse3 (separate groups). See configuration details below.Table 3: Description of operations for field-trial Reuse1à Reuse3
• Applied only in GSM900 band.• BCCH frequencies were not modified.• Majority of cells have at most 3 TRX in hopping.
All
right
s re
serv
ed. P
assi
ng o
n an
d co
pyin
g of
this
docu
men
t, us
e an
d co
mm
unic
atio
n of
this
con
tent
s no
tpe
rmitt
ed w
ithou
t writ
ten
auth
oriz
atio
n fr
om A
lcat
el
©Re
serv
ados
todo
s os
dire
itos.
A c
ópia
ou
a en
trega
des
tedo
cum
ento
a
terc
eiro
s,
bem
co
mo
o us
o ou
a
com
unic
ação
do
seu
cont
eúdo
, nã
o sã
o pe
rmiti
dos
sem
auto
rizaç
ão e
scrit
a da
ALC
ATE
L PO
RTU
GA
L SA
3DF 01902 2060 UAZZA Edition 01 RELEASED 7 / 16
• In order to see more visibly the effect on Reuse3 compared with Reuse1, TRX_prefmark wasconfigured before and during the trial to give priority to TRX in TCH band.
• Hopping groups configured as follows:
Hoppinggroup 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119
group 1 x x x x x xgroup 2 x x x x x xgroup 3 x x x x x x
The advantage of using intercalated groups is that, for a certain sector, we have separation of more than 2frequencies per TRX (and not only 2, as would be the case with consecutive frequencies per group).MAIOS:
TRX 1 TRX 2 TRX 3Sector 1 0 2 4Sector 2 1 3 5Sector 3 0 2 4
HSN must be the same for each site. In this way, intra-site collisions are avoided.As a rule, groups are applied as follows:
GroupSectors with azimuth >= 0 and < 120 1Sectors with azimuth >= 120 and < 240 2Sectors with azimuth >= 240 and < 360 3
For sites with 4 or more TRX in hopping or sites that do not follow the orientation pattern: in these cases, adifferent group (possibly with more than 6 frequencies) were created. These cells were analyzed case by case.
3.2.4 QoS results
Indicator Behaviour ConclusionTraffic BH BSC Stable ( ≈370 Erl.)Duration RTCH Stable (41 sec)Duration SDCCH Stable (2.9 sec)SDCCH Assign Fail Rate Stable (6.0%)RTCH Assign Fail Stable (0.5%)Call-drop Stable (1.1%)SDCCH drop Stable (1.0%)Handover Failure Rate Stable (ROC = 2.4%; Drop = 0.4%)Handovers Stable ( ≈ 180,000)HO/Call Stable (0.76)Causes HO (#) Better-cell: 90,000 à 90,000
Quality: 47,500 à 44,000Level: 50000 à 53,000
Causes HO Better-cell: 47% à 47%Quality: 24% à 23%Level: 27% à 28%
Transfer of Quality HO to Better-cell andLevel Handovers. This effect is morevisible during the period whereTRXprefmark was giving priority to TRX inhopping (Quality HO = 37% à 31%)
Table 4: QoS comparison between Reuse1 and Reuse3
Results from drive-tests:Drive-tests were performed before and after the operation (with traffic with priority to TRX in hopping):
All
right
s re
serv
ed. P
assi
ng o
n an
d co
pyin
g of
this
docu
men
t, us
e an
d co
mm
unic
atio
n of
this
con
tent
s no
tpe
rmitt
ed w
ithou
t writ
ten
auth
oriz
atio
n fr
om A
lcat
el
©Re
serv
ados
todo
s os
dire
itos.
A c
ópia
ou
a en
trega
des
tedo
cum
ento
a
terc
eiro
s,
bem
co
mo
o us
o ou
a
com
unic
ação
do
seu
cont
eúdo
, nã
o sã
o pe
rmiti
dos
sem
auto
rizaç
ão e
scrit
a da
ALC
ATE
L PO
RTU
GA
L SA
3DF 01902 2060 UAZZA Edition 01 RELEASED 8 / 16
Bad RxQual - before Bad RxQual - after
16.7% 15.2%
Table 5: QoS from drive-tests
We notice a slight reduction on the number of samples with bad quality, but not very significant.
QVOICE results:Qvoice results did not show significant modifications before and after the operation.
GPRS results:GPRS tests were performed for FTP throughput, Web, Wap access and menu access, and ping delays. Testswere performed in static and also mobility modes. Results show no significant difference comparing Reuse1with Reuse3.
3.2.5 Analysis of the Reuse3 field-trial
• Reduction in Quality HO; increase of Better-Cell and Level HO (results more visible with priority forTRX in hopping).
• No significant modification of other QoS indicators or in Qvoice measurements.Reuse3 did not show significant modifications over Reuse1, having the disadvantage that it needs extraworkload to define and tune the frequency group of each cell, or after a modification of tilts or azimuths.Also, the reduction of Quality HO may not necessarily means better voice quality, since a reduction in thenumber of hopping frequencies may cause the number of Quality HO to reduce (OFFSET_HOPPING =1 andwas not changed with this trial) without improving the quality of the voice. See details of this subject on thefollowing section.
All
right
s re
serv
ed. P
assi
ng o
n an
d co
pyin
g of
this
docu
men
t, us
e an
d co
mm
unic
atio
n of
this
con
tent
s no
tpe
rmitt
ed w
ithou
t writ
ten
auth
oriz
atio
n fr
om A
lcat
el
©Re
serv
ados
todo
s os
dire
itos.
A c
ópia
ou
a en
trega
des
tedo
cum
ento
a
terc
eiro
s,
bem
co
mo
o us
o ou
a
com
unic
ação
do
seu
cont
eúdo
, nã
o sã
o pe
rmiti
dos
sem
auto
rizaç
ão e
scrit
a da
ALC
ATE
L PO
RTU
GA
L SA
3DF 01902 2060 UAZZA Edition 01 RELEASED 9 / 16
3.3 Field-trial: Discrete Hopping
3.3.1 Description
“Discrete hopping” consists of using a fixed frequency for the BCCH TRX and using synthesized frequencyhopping in n frequencies for the other TRX. n is usually a small number. On this trial, n was equal to thenumber of TRX in hopping. That is:
Number of TRX in the cell Number offrequencies to hop
1 BCCH TRX + 1 TRX 11 BCCH TRX + 2 TRX 21 BCCH TRX + 3 TRX 31 BCCH TRX + 4 TRX 41 BCCH TRX + 5 TRX 51 BCCH TRX + 6 TRX 61 BCCH TRX + 7 TRX 7
Table 6: Number of frequencies to hop per cell used in the field-trial “Discrete Hopping”
On the OMC, this configuration is like RFH (synthesized frequency hopping) [1]. The obvious difference now isthat is requires intelligence to plan frequencies for each cell. On our trial, these frequencies were chosen usingthe SONAR tool (see Chapter 4 for details).
3.3.2 Motivation
Individual frequencies can be chosen, allowing higher control of bad quality cases. The advantage isespecially important on high sites, or in areas under strong spill-overs, which cause much degradation withreuse 1. Also, the availability of the SONAR tool, allowing producing a frequency plan based on real field-data (and not only theoretical data from coverage estimations) and previous successful field-trials in SouthAfrica (contact Alcatel South Africa radio team for details) prompted us for this trial.
3.3.3 Description of operation
Date Description12/May/2003 BSC frozen20/May/2003 Reuse1 à Discrete Hopping. See configuration details below.
Table 7: Description of operations for field-trial Reuse1à Discrete Hopping
• Applied in GSM900 and DCS1800 bands• BCCH frequencies were not modified• TCH frequencies chosen using SONAR (see Chapter 4 for details)
3.3.4 QoS results
Results are shown for a dense-urban BSC (Tgp1); other BSC presented similar results.
All
right
s re
serv
ed. P
assi
ng o
n an
d co
pyin
g of
this
docu
men
t, us
e an
d co
mm
unic
atio
n of
this
con
tent
s no
tpe
rmitt
ed w
ithou
t writ
ten
auth
oriz
atio
n fr
om A
lcat
el
©Re
serv
ados
todo
s os
dire
itos.
A c
ópia
ou
a en
trega
des
tedo
cum
ento
a
terc
eiro
s,
bem
co
mo
o us
o ou
a
com
unic
ação
do
seu
cont
eúdo
, nã
o sã
o pe
rmiti
dos
sem
auto
rizaç
ão e
scrit
a da
ALC
ATE
L PO
RTU
GA
L SA
3DF 01902 2060 UAZZA Edition 01 RELEASED 10 / 16
QoS indicators Behaviour Conclusion
SDCCH drop 1.2% à 1.2% StableRTCH assign fail 0.6% à 0.6% StableCall-drop 1.1% à 1.1% StableHandover success rate ROC: 3.4% à 3.3%
Drop: 0.5% à 0.5%Stable
HO causes Better-cell: 43% à 42%Qual HO: 34% à 29%Level HO: 19% à 23%
Reduction of Quality HO:transference to Level HO
Interference bands(% in band 1)
54% à 68% Higher number of TS in band 1
HO/call 0.64 à 0.61 Slight reduction of HO/call
Table 8: QoS results on the trial “Discrete Hopping” (results are averages computed before (avg of 12-16/May/2003) and after (avg of 21-22/May/2003).
Split of standard HO Causes
0
10
20
30
40
50
%DL Qual
%UL Qual
%DL Lev
%UL Lev
% DL interf
% UL Interf
% BC
Figure 2: Evolution of HO causes in field-trial Discrete Hopping (BSC Tgp1).
QVOICE results:Qvoice results (1 full day measurements before and after operation) showed improvements:
Hopping Reuse 1 Discrete Hopping
VQ – good 88.9% 90.9%VQ – sufficient 6.7% 6.1%VQ – bad 4.4% 3.1%
Table 9: Qvoice measurements for Discrete Hopping trial
These results were based on extensive measurements made in the area, on a pre-defined route and on a pre-defined time period. Even though they were taken into consideration, they are particular and may not reflectthe behavior of all the area. The ideal would be to have QoS indicators related with voice quality, but that isnot available in the B6 release.
3.3.5 Analysis of the Discrete Hopping field-trial
• Reduction in HO Quality (see note below).• Slight reduction of HO/call, although not very significant.• Higher percentage of TS in interference band 1;• Qvoice measurements (1 day measurements before and after) showed improvement.
Another trial was made considering at least 4 frequencies to hop on each cell, even if the number of TRX percell was 2 or 3. However, improvements were less noticed than with this trial. This seems to show that the
All
right
s re
serv
ed. P
assi
ng o
n an
d co
pyin
g of
this
docu
men
t, us
e an
d co
mm
unic
atio
n of
this
con
tent
s no
tpe
rmitt
ed w
ithou
t writ
ten
auth
oriz
atio
n fr
om A
lcat
el
©Re
serv
ados
todo
s os
dire
itos.
A c
ópia
ou
a en
trega
des
tedo
cum
ento
a
terc
eiro
s,
bem
co
mo
o us
o ou
a
com
unic
ação
do
seu
cont
eúdo
, nã
o sã
o pe
rmiti
dos
sem
auto
rizaç
ão e
scrit
a da
ALC
ATE
L PO
RTU
GA
L SA
3DF 01902 2060 UAZZA Edition 01 RELEASED 11 / 16
better controlled the frequencies are per cell, the better the results are. All in all, the results are not excellent,and a trial of BBH was tested, as described in the next section.
Note about the reduction of HO quality with reduction of hopping frequencies:With these tests (Reuse3, Discrete Hopping with a minimum of 4 frequencies to hop per cell, Discrete Hoppingwith a number of hopping frequencies equal to the number of TRX in hopping) we note that the percentage ofQuality HO is reduced when we reduce the number of frequencies to hop. However, in some tests, the Qvoiceresults do not show visible improvement even with a significant reduction of Quality HO.This can be explained considering that the higher the number of frequencies we use to hop, the higher is thepossibility to suffer from short term interference (collisions). These collisions deliver a high BER for a shortperiod of time. RXQUAL decreases based on increased BER average. The probability of collisions is alsoincreasing with higher traffic. On the other hand, the degraded BER should be more than compensated by thefact that GSM benefits higher from de-interleaving and de-channel coding (benefit against fading especiallyfor slow mobiles). This effect is not visible in RXQUAL.So, on frequency hopping, a certain threshold of voice quality is achieved with worse RxQual (comparing withfixed frequencies). This is why the hopping algorithm uses the parameter OFFSET_HOPPING for power-controland quality handovers. The ideal Offset should lead to the HO Trigger at the same Voice Quality as withouthopping and no Offset, and shall be a function of number of hopping frequencies and traffic.We use OFFSET_HOPPING equal to 1, based on defaults/historical reasons in Alcatel, and we did not perform(due to lack of time) tests on this parameter (which should be synchronized with Qvoice campaigns).Concluding, the bare fact of reduction of Quality HO may not necessarily mean an improvement in VoiceQuality in the network.
3.4 Field-trial: Baseband Hopping
3.4.1 Description
Classical Baseband Hopping, where there are as much frequencies per cell as number of TRX [1].
3.4.2 Motivation
It makes sense to use BCCH frequencies to hop, since in TMN network RxQual is presently worse in TCH TRX,while the number of BCCH frequencies is greater than the number of hopping frequencies. So we try to usethe BCCH band to reduce the RFload in the network. On the other hand, severe interference cases on the callspresently handled by the beacon TRX, causing sometimes call-drop, could be reduced by using hopping.In summary, BBH combines the benefits of intelligent frequency planning and the benefits of frequencyhopping.The frequencies for each cell are, for this trial, the same as those used for the Discrete Hopping trial.
3.4.3 Description of operation
This trial was done after the trial of Discrete Hopping. In this way, we can make better comparisons.
Date Description12/May/2003 BSC frozen20/May/2003 Reuse1 à Discrete Hopping. See previous section for details.23/May/2003 Discrete Hopping à Baseband hopping. See configuration details
below.Table 10: Description of operations for field-trial Reuse1à Discrete Hopping à Baseband Hopping
• Applied in GSM900 and DCS1800 bands• BCCH frequencies were not modified
All
right
s re
serv
ed. P
assi
ng o
n an
d co
pyin
g of
this
docu
men
t, us
e an
d co
mm
unic
atio
n of
this
con
tent
s no
tpe
rmitt
ed w
ithou
t writ
ten
auth
oriz
atio
n fr
om A
lcat
el
©Re
serv
ados
todo
s os
dire
itos.
A c
ópia
ou
a en
trega
des
tedo
cum
ento
a
terc
eiro
s,
bem
co
mo
o us
o ou
a
com
unic
ação
do
seu
cont
eúdo
, nã
o sã
o pe
rmiti
dos
sem
auto
rizaç
ão e
scrit
a da
ALC
ATE
L PO
RTU
GA
L SA
3DF 01902 2060 UAZZA Edition 01 RELEASED 12 / 16
• Frequencies per cell are the same as those used in the field-trial for Discrete Hopping (chosen usingSONAR. This means that only the type of hopping was modified in the OMC.
3.4.4 QoS results and analysis
Results are shown for a dense-urban BSC (Tgp1); other BSC presented similar results.
SDCCH Drop
02000400060008000
100001200014000
01-M
ai-2
003
03-M
ai-2
003
05-M
ai-2
003
07-M
ai-2
003
09-M
ai-2
003
11-M
ai-2
003
13-M
ai-2
003
15-M
ai-2
003
17-M
ai-2
003
19-M
ai-2
003
21-M
ai-2
003
23-M
ai-2
003
25-M
ai-2
003
27-M
ai-2
003
29-M
ai-2
003
31-M
ai-2
003
02-Ju
n-20
03
04-Ju
n-20
03
06-Ju
n-20
03
08-Ju
n-20
03
10-Ju
n-20
03
12-Ju
n-20
03
14-Ju
n-20
03
00.20.40.60.811.21.41.6
Drop - BSS
Drop - HO
Drop - Radio
% Drop
Figure 3: Evolution of SDCCH drop in field-trial Baseband Hopping (BSC Tgp1).
RTCH assignment failure
050000
100000150000200000250000300000350000
01-M
ai-2
003
03-M
ai-2
003
05-M
ai-2
003
07-M
ai-2
003
09-M
ai-2
003
11-M
ai-2
003
13-M
ai-2
003
15-M
ai-2
003
17-M
ai-2
003
19-M
ai-2
003
21-M
ai-2
003
23-M
ai-2
003
25-M
ai-2
003
27-M
ai-2
003
29-M
ai-2
003
31-M
ai-2
003
02-Ju
n-20
03
04-Ju
n-20
03
06-Ju
n-20
03
08-Ju
n-20
03
10-Ju
n-20
03
12-Ju
n-20
03
14-Ju
n-20
03
00.10.20.30.40.50.60.70.80.9
Fail - BSS
Fail - Radio
Success
% Fail
Figure 4: Evolution of RTCH assign fail in field-trial Baseband Hopping (BSC Tgp1).
Call drop
0
1000
2000
3000
4000
5000
6000
01-M
ai-2
003
03-M
ai-2
003
05-M
ai-2
003
07-M
ai-2
003
09-M
ai-2
003
11-M
ai-2
003
13-M
ai-2
003
15-M
ai-2
003
17-M
ai-2
003
19-M
ai-2
003
21-M
ai-2
003
23-M
ai-2
003
25-M
ai-2
003
27-M
ai-2
003
29-M
ai-2
003
31-M
ai-2
003
02-Ju
n-20
03
04-Ju
n-20
03
06-Ju
n-20
03
08-Ju
n-20
03
10-Ju
n-20
03
12-Ju
n-20
03
14-Ju
n-20
03
00.20.40.60.811.21.41.6
Drop - BSS
Drop - HO
Drop - Radio
% RTCH drop
% Call Drop
Figure 5: Evolution of CDR in field-trial Baseband Hopping (BSC Tgp1).
All
right
s re
serv
ed. P
assi
ng o
n an
d co
pyin
g of
this
docu
men
t, us
e an
d co
mm
unic
atio
n of
this
con
tent
s no
tpe
rmitt
ed w
ithou
t writ
ten
auth
oriz
atio
n fr
om A
lcat
el
©Re
serv
ados
todo
s os
dire
itos.
A c
ópia
ou
a en
trega
des
tedo
cum
ento
a
terc
eiro
s,
bem
co
mo
o us
o ou
a
com
unic
ação
do
seu
cont
eúdo
, nã
o sã
o pe
rmiti
dos
sem
auto
rizaç
ão e
scrit
a da
ALC
ATE
L PO
RTU
GA
L SA
3DF 01902 2060 UAZZA Edition 01 RELEASED 13 / 16
The following table allows comparison between Reuse1, Discrete Hopping trial and Baseband hopping trial:
QoSindicators
Reuse 1 Discretehopping
Basebandhopping
Obs
SDCCH drop 1.2% 1.2% 0.8% Significant improvementRTCH assignfail
0.6% 0.6% 0.4% Significant improvement, showingclearly a reduction of interference
Call-drop 1.1% 1.1% 0.9% Significant improvementHandoversuccess rate
96.2% 96.2% 96.4% Improvement more visible in someother BSCs
HO causes Better-cell: 43%Qual HO: 34%Level HO: 19%
Better-cell: 42%Qual HO: 29%Level HO: 23%
Better-cell:41%Qual HO: 32%Level HO: 22%
Still reduction of Qual HO with BBH,but less noticed than with Discrete
Interferencebands(% in band 1)
54% 68% 61% Improvement is visible with BBH butless noticed than in Discrete
HO/call 0.64 0.61 0.58 Reduction with BBH even morevisible in other BSCs: showsimprovement in Voice Quality
QVOICE results:
Hopping Reuse 1 Discrete Hopping BasebandHopping
VQ – good 88.9% 90.9% 90.8%VQ – sufficient 6.7% 6.1% 6.8%VQ – bad 4.4% 3.1% 2.6%
Table 11: Qvoice measurements for Discrete Hopping trial
Drive-tests made in the same conditions as those for previous tests. An improvement is seen in Basebandcomparable with that of the Discrete trial.
From these results we conclude:• Clear reduction of general interference in the network: indicators show a clear reduction of SDCCH
drop, RTCH assign fail, and Call-drop.• Reduction of HO/call.• QVoice results were good but in other BSCs did now show a clear improvement over Discrete
hopping. We concluded that the method intrinsic to QVoice method (drive-tests in 1 day, in apredefined route) was insufficient to make conclusive comparisons, when the improvements are sosmall in percentage.
These results were considered very good and this hopping strategy was generalized to all network (19 BSC).The SONAR tool and the method we followed to use it, proved also to be efficient and to produce goodresults.
Applied to all the network, the following improvements were obtained:• SDCCH drop: 1.1% à 0.8% (improvement of 27%)• RTCH assign fail: 0.5% à 0.3% (improvement of 40%)• Call-drop: 1.2% à 1.0% (improvement of 17%)• Handover Success Rate (execution): 96.8% à 97.5% (improvement of 22%)
• Call Success Rate: 97.2% à 97.9%, which means that the revenue lost in the network due to radiointerferences was reduced by 25%.
All
right
s re
serv
ed. P
assi
ng o
n an
d co
pyin
g of
this
docu
men
t, us
e an
d co
mm
unic
atio
n of
this
con
tent
s no
tpe
rmitt
ed w
ithou
t writ
ten
auth
oriz
atio
n fr
om A
lcat
el
©Re
serv
ados
todo
s os
dire
itos.
A c
ópia
ou
a en
trega
des
tedo
cum
ento
a
terc
eiro
s,
bem
co
mo
o us
o ou
a
com
unic
ação
do
seu
cont
eúdo
, nã
o sã
o pe
rmiti
dos
sem
auto
rizaç
ão e
scrit
a da
ALC
ATE
L PO
RTU
GA
L SA
3DF 01902 2060 UAZZA Edition 01 RELEASED 14 / 16
Analyzing these results, we may also suspect that the improvement also came from the calls previouslyhandled by BCCH TRX, as explained before. We may then predict that a global new BCCH plan using SONARwould produce even better QoS results. This was not done in this trial.
4 USING THE SONAR TOOL
The frequency plans used in the field-trials “Discrete Hopping” and “Baseband Hopping” described in thisreport were obtained with a new tool called SONAR originally developed by Alcatel South-Africa. This toolallows the choice of frequencies for each cell based on T180 counters.This section presents a brief description of this tool and of the method we followed to use the tool.
4.1 Outline of the SONAR tool
The basic ideia behind SONAR is that the more handovers with a target cell, the larger overlap zone and thehigher the possibility of suffering interferences.As input, the SONAR tool uses the number of HO attempts between cells (BSS counters type 180) to computethe best frequencies for each cell.To quantify the interference for each ARFCN, SONAR uses a penalty value weighted by a value. Consideringall penalties and some specific planning restrictions (like maintaining a separations of 2 or 3 in thefrequencies in a same cell, for example), an equivalent to an interference matrix is build, from where the bestfrequencies for each cell are chosen.SONAR is available in “Perl” language having a HTML interface. It works with GSM900 and DCS1800 bands.Inputs have to have a specific format to be read by the program. The output is a list of frequencies per cell.It is planned, however, this algorithm to be incorporated in the A955 tool in the short term.
All
right
s re
serv
ed. P
assi
ng o
n an
d co
pyin
g of
this
docu
men
t, us
e an
d co
mm
unic
atio
n of
this
con
tent
s no
tpe
rmitt
ed w
ithou
t writ
ten
auth
oriz
atio
n fr
om A
lcat
el
©Re
serv
ados
todo
s os
dire
itos.
A c
ópia
ou
a en
trega
des
tedo
cum
ento
a
terc
eiro
s,
bem
co
mo
o us
o ou
a
com
unic
ação
do
seu
cont
eúdo
, nã
o sã
o pe
rmiti
dos
sem
auto
rizaç
ão e
scrit
a da
ALC
ATE
L PO
RTU
GA
L SA
3DF 01902 2060 UAZZA Edition 01 RELEASED 15 / 16
Figure 6: Input to SONAR tool
It is important also to refer EasyRNP: another tool whose core algorithm is based on SONAR’s. EasyRNP wasdeveloped by Alcatel Shanghai Bell and adds an interesting user-friendly interface, allowing frequencyoptimization cell-by-cell (but not new frequency plans from scratch like SONAR).
4.2 Workflow with SONAR
The following workflow was used:
Step1: Check HO relation in the networkAs SONAR uses T180 as the input for its calculations, it is important to verify that the network is not
suffering from many missing HO relations. Therefore, this verification shall be done, and an operation ofadding HO relations shall be performed if necessary.
Step 2: Data capturingT180 counters shall be retrieved from the OMC (either by the use of a script in the OMC, or using a TSL
script in NPA) correspondent to a period of 2 or 3 weeks. During this period, the network shall be stable, inthe sense that no major modifications are performed (like new sites, planning modification, etc.). Note that it isnot necessary the network to be completely frozen, so frequency modifications are allowed, as well as someparameter optimization. What it is important is the flow of HO in the network. Note that this is a majoradvantage over other methods used by competitors, where a complete freeze is necessary over long periods.
All
right
s re
serv
ed. P
assi
ng o
n an
d co
pyin
g of
this
docu
men
t, us
e an
d co
mm
unic
atio
n of
this
con
tent
s no
tpe
rmitt
ed w
ithou
t writ
ten
auth
oriz
atio
n fr
om A
lcat
el
©Re
serv
ados
todo
s os
dire
itos.
A c
ópia
ou
a en
trega
des
tedo
cum
ento
a
terc
eiro
s,
bem
co
mo
o us
o ou
a
com
unic
ação
do
seu
cont
eúdo
, nã
o sã
o pe
rmiti
dos
sem
auto
rizaç
ão e
scrit
a da
ALC
ATE
L PO
RTU
GA
L SA
3DF 01902 2060 UAZZA Edition 01 RELEASED 16 / 16
For the data retrieval, it is also important to verify that there are no periods with missing data for a certain BSC(or else, cells on these BSC would be treated by the tool has having less HO than the reality, creatingabnormal results).Also, note that T180 are counters based on incoming HO, so cells in the frontiers have to be subjected to amore careful procedure (see below).Other inputs to SONAR are:
• updated “cell.csv” file (from the daily RNL export from the OMC);• file with a list of frequencies to computed per cell.
Step 3: Run SONARSONAR was firstly developed for the Vodafone network in South Africa by Alcatel South Africa. At the time thisproject was carried out, SONAR had some particularities for this specific network, so some data adaptationwas needed to use it (for example, create fake CI for all cells, as the algorithm was prepared to identify cellsbelonging to the same site through CI). Not all details are describe here, as new versions of SONAR shallappear. For more details, the Alcatel South Africa team is the best source.SONAR uses an iterative method trying to find a combination of frequencies for the network so that the total of“penalties” be minimized. The “penalty” is a measure of the interference that a certain frequency will create onthe network.On our trial we did not modify in general the default options and constants used in the program. However, theoption Co-Site – Adj Channel was modified from “avoid” to “allow” producing a better result.
Step 4: VerificationA cell-by-cell verification of the final frequency plan was performed. A special attention was given to cells inthe frontier, as the result may be less accurate due to lack of information of HO flow of the cells outsideAlcatel area. For this verification, the tool EasyRNP was used, as it has a good interface and allows computingthe new total “penalty” after a modification. A small number of modifications were made for very specificsituations but in general the SONAR result proved itself, after implementation, very trustable. Note that due tothe intrinsic form of the SONAR algorithm, the cells with more handovers will be preferred to apply a cleanerfrequency (which is interesting from to the customers point of view) and that it may be necessary to carefullycheck and optimize, if necessary, specific situations like an important street or highway or delicate points(special clients, etc).
Step 5: ImplementationThe new plan was implemented in the network by MLU. QoS monitoring followed. The description of theseoperations is out of the scope of this report.
4.3 Advantages of SONAR
Data input: Based on real field data, and not theoretical coverage predictions. The format of SONAR allows,in theory, to optimize networks not necessary using Alcatel BSS, providing the HO counters are available.Network state: Although the network shall not suffer many important modifications during the period ofextraction of the T180 counters, it is not necessary to freeze the network in terms of frequencies and some BSSparameter optimization. This is an important advantage over other concurrent existing tools.Duration: A complete frequency plan (around 2900 TCH frequencies) for the complete network (19 BSC)took around 2 week to produce with SONAR. This period includes the data preparation and the cell-by-cellverification prior to implementation. The executable time of SONAR is negligible.Results: An important improvement in QoS was obtained, using a network plan produced by SONAR, on anetwork subjected to constant optimization operations and where QoS indicators presented already veryacceptable figures.
– END OF DOCUMENT –
