Actual Scenario in UMTS

[plannerguy]

Hi

Myself have a query on the power usage and footprint of UMTS network.
For e.g if we take case of UMTS cell which is radiating at 20watts, the pilot power is configured to 2Watts. that is 10% of the total power.
Since the UE measure the pilot channel the footprint will be only upto 2watts.now as the users gets latches the power allotted goes on increases and some moment full power starts radiating. so at antenna end now power is 20 watts.

Now questions is will the power 20watts gets radiated beyond the Pilot range?.if so will it cause interference to the another cell .

Rgds
Plannerguy

[s52d]

Hi!

It all depends on spreading factor.
In order to detect signal, it is not just signal strength, it is C/I after despreading and filtering that matters.

So, in short: while HSPA usable region matches pilot region, you do generate interference well beyond pilot detectable region.
And yes, more power, more interference.
Also: in isolated cell, coverage is limited by thermal noise. In real networks, cell coverage is limited by other cells.
(A point when you handover out of the cell).

On interference:
This is called cell breathing, where real covereage for some services depends on neighbor cell load.
Common in braodband networks, observable also in GSM.

BR
s52d

[plannerguy]

Thanks for the explanation.

So what i understood is jotted below

1)if cell is raditing at 20watts the actual signals will be there beyound the CPICH range.
2)The cell raditing at full power will effect the performance of near by cell.

So my next query is .

We can measure a cell radius by knowing the CPICH range through DT or through the OSS stats i.e PRACH report.
But both measure the Known range.
so how will we know that another cell performnce is tempered by a loaded cell working at 20 watts, which is raditing above CPICH range.

Rgds
Plannerguy

[srilasitha]

Maximum Power assigned for the channels depends on spreading factor. Power control is used to reduce the interference to outer cells. you can observe Ec/Io changes to identify interference increments with neighbor cell loading

Further there is a cell radius parameter to avoid distance users camp into a cell.

[s52d]

Thanks for the explanation.

So what i understood is jotted below

1)if cell is raditing at 20watts the actual signals will be there beyound the CPICH range.
2)The cell raditing at full power will effect the performance of near by cell.

So my next query is .

We can measure a cell radius by knowing the CPICH range through DT or through the OSS stats i.e PRACH report.
But both measure the Known range.
so how will we know that another cell performnce is tempered by a loaded cell working at 20 watts, which is raditing above CPICH range.

Rgds
Plannerguy

1 and 2:
Yes. As several cells use same bandwidth, interference can be observed much further as service are of the cell.
Even CPICH is interfereing other cells. Basics of CDMA.
More power, more interference.


Think about: if this is the only cell in the network, what is its coverage?
What happens if another one is 5 km away?

Now... Timing advance can be measured when terminals access the network.
If fhey access it, this cell is best server. If it is best server, then other cells are interfering it ;-).

Of course, in case when city cell with radius of 300 m is receiving traffic from hills 20 km away (I've seen it), then some actions shall be taken.
Most effective: tune antennas. Temporary: do not push people 20 km away from GSM.
Check for real traffic, LA/RA updates etc: they usually have different distance profiles.

In order to really detect interference, we analyze measurement reports. EIther from the system, or from real measurements.
Heavy users on the helicopter can make impressive wrong picture.
Top of high buildings is nice point to measure as well.
Problem is 3 dimensional.
I recall some tests with terminals and PN-scanners on two floors above average antenna hight. Well spend day.

In short: understand your cells, control interference using antennas.
RBS power can make few dB difference, antennas can make 10 dB easiliy.

BR
s52d