CRO not working

[thewatcher]

Hi,

Using 2G e******* network with 2 bands (900/1800).
I have a site where I'm trying to make MS to camp on 900MHz cells instead of the 1800MHz cells.

Even when applying a negative CRO of 126 dB (by setting the cro to 63 and PT=31) MS still camp on 1800Mhz cells. I confirm that by monitoring RACH KPI.

I have to possible guess as to why it does not work:
1. we have HCS enabled in the network and the priority of the 1800 MHZ is 4 and the 900MHz is 7.
2. we have PBCCH enabled, so maybe MS use the C31/C32 instead of C1/C2

Will much appreciate you help
Thanks in advance.

[gprastomo]

Are yous sure,that you applied to a correct value ?
There is no negatif CRO actually.

Try to put CRO of 900 become larger and put CRO of 1800 to be 0.

You will use C31/32 only when PCCH active and the Ue is attached for GPRS.

So to utilize 900, put larger positif value of CRO on 900 and put 0 CRO for 1800.

Just check also the cell reselection parameter indication should be active so C2/CRO will be applied

[thewatcher]

When configuring PT=31 the value you put for the CRO becomes negative. That what it says in Alex.

also I read in Alex that GPRS attached MS will not use the C1/C2 criteria for reelection but they will use C31/C32 criteria.

any ideas?

[punto]

Actually , you get CRO "positive" or "negative", dependent to penalty time ... thewatcher applied it in correct manners ... also your option is OK

let`s see the 3GPP definition to be clear - theres are 2 formulas (3GPP TS 45.008 V4.18.0 (2009-02))

All values are expressed in dBm.
The path loss criterion (3GPP TS 43.022) is satisfied if C1 > 0.
The reselection criterion C2 is used for cell reselection only and is defined by:
C2 = C1 + CELL_RESELECT_OFFSET TEMPORARY OFFSET * H(PENALTY_TIME T) for
PENALTY_TIME <> 11111
C2 = C1 - CELL_RESELECT_OFFSET for PENALTY_TIME = 11111
where
For non serving cells:
H(x) = 0 for x < 0
= 1 for x >= 0
For serving cells:
H(x) = 0
T is a timer implemented for each cell in the list of strongest carriers (see subclause 6.6.1). T shall be started from zero at the time the cell is placed by the MS on the list of strongest carriers, except when the previous serving cell is placed on the list of strongest carriers at cell reselection. In this, case, T shall be set to the value of PENALTY_TIME (i.e. expired).
CELL_RESELECT_OFFSET applies an offset to the C2 reselection criterion for that cell.
NOTE: CELL_RESELECT_OFFSET may be used to give different priorities to different bands when multiband operation is used.
TEMPORARY_OFFSET applies a negative offset to C2 for the duration of PENALTY_TIME after the timer T has started for that cell.
PENALTY_TIME is the duration for which TEMPORARY_OFFSET applies The all ones bit pattern on the PENALTY_TIME parameter is reserved to change the sign of CELL_RESELECT_OFFSET and the value of TEMPORARY_OFFSET is ignored as indicated by the equation defining C2.
CELL_RESELECT_OFFSET, TEMPORARY_OFFSET, PENALTY_TIME and CELL_BAR_QUALIFY (see table 1a) are optionally broadcast on the BCCH of the cell. If not broadcast, the default values are CELL_BAR_QUALIFY = 0, and C2 = C1. The use of C2 is described in 3GPP TS 43.022.
These parameters are used to ensure that the MS is camped on the cell with which it has the highest probability of successful communication on uplink and downlink....
Hope this is clearer now ! P

[iara]

Hi,

Using 2G e******* network with 2 bands (900/1800).
I have a site where I'm trying to make MS to camp on 900MHz cells instead of the 1800MHz cells.

Even when applying a negative CRO of 126 dB (by setting the cro to 63 and PT=31) MS still camp on 1800Mhz cells. I confirm that by monitoring RACH KPI.

I have to possible guess as to why it does not work:
1. we have HCS enabled in the network and the priority of the 1800 MHZ is 4 and the 900MHz is 7.
2. we have PBCCH enabled, so maybe MS use the C31/C32 instead of C1/C2

Will much appreciate you help
Thanks in advance.

MS camp on 1800 Band because of his layer: in fact, if the Signal level of 1800 are sufficient to be on high priority (above layerthr) MS will camp on this band. You can anyway adopt new strategy: block 1800 for access so MS will camp on 900 Band first and then do HO to 1800.

[thewatcher]

I believe I had some success to move MS from the 1800 to 900 based on RACH KPI results. but was unsuccessful to move all MS to the 900 cells (I still see RACH on the 1800 cell)

I believe the source of the problem is that the 1800 has higher HSC layer then the 900.
So when I applied a negative CRO to the 1800, MS moved only to neighboring 1800 cells but not to the neighboring 900 cells. therefore some MS could not move from my 1800 cell since they could not measure any 1800 neighbors, and disregarded the 900 neighbors because of the diffident HCS layers between the bands.

any thoughts?

[electron]

I believe I had some success to move MS from the 1800 to 900 based on RACH KPI results. but was unsuccessful to move all MS to the 900 cells (I still see RACH on the 1800 cell)

I believe the source of the problem is that the 1800 has higher HSC layer then the 900.
So when I applied a negative CRO to the 1800, MS moved only to neighboring 1800 cells but not to the neighboring 900 cells. therefore some MS could not move from my 1800 cell since they could not measure any 1800 neighbors, and disregarded the 900 neighbors because of the diffident HCS layers between the bands.

any thoughts?

1.HCS is working just in dedicated more not in Idle mod

2. In this case try to bar the 1800 cell! CB=On in htis case all cal lset up will perform on 900 and and if needed will give HO to 1800 cell!

3. Why you are not trying to have coverage restriction by physical changes?!

[taomomteling]

Dear thewatcher,

I think ther is something wrong with the CRo if you have changed the CRO to 126dB and PT to 31, normaly you have to camp on the 900! please check if you're using C2 or still C1 trough the parameters "Cell Parameters Indicator", if it's set to 1 mean's you're using C2 and if it's 0, mean the CRO is not used, and C2=C1.

Cheers,

[thewatcher]

electron, thanks for the reply,
HCS does work for idle MS. When a MS is GPRS attached and is in packet idle mode and the cell has PBCCH enabled. In this case the MS will use the C31/C32 criteria that takes into account the layer propriety.

Can not do any physical change and also would not like to have the cell barred, the CRO solution should provide the best performance.

taomomteling,
I could not find the parameter your talking about, do you have the OSS command for that?

thanks

[taomomteling]

electron, thanks for the reply,
HCS does work for idle MS. When a MS is GPRS attached and is in packet idle mode and the cell has PBCCH enabled. In this case the MS will use the C31/C32 criteria that takes into account the layer propriety.

Can not do any physical change and also would not like to have the cell barred, the CRO solution should provide the best performance.

taomomteling,
I could not find the parameter your talking about, do you have the OSS command for that?

thanks

Hi,

Sorry, it's Cell Reselect Parameters indicator:

I am not very surabout the exact indicator in E*******!

CELL_RESLECT_PARAM_IND: Indicates whether C2 parameters are broadcast
Y/N
Nokia and Huawei MML name = PI
Settings:CELL_RESLECT_PARAM_IND = N
then C2=C1 and no other parameters will matter

CELL_RESLECT_PARAM_IND = Y
then C2 is calculated using additional parameters.