LAC Design

[Ericsson_RND]

Dears I have sites inside urban, and other sites outside the main city, what is the recommendation for LAC design:

Is it recommended to set two different LAC for the same BSC or One LAC is better in this case.

Note all the sites are carried by one BSC.

If there is document for this issue please share.

Thanks in Advance.

Regards
E*******_RND

[s52d]

Dears I have sites inside urban, and other sites outside the main city, what is the recommendation for LAC design:

Is it recommended to set two different LAC for the same BSC or One LAC is better in this case.

Note all the sites are carried by one BSC.

If there is document for this issue please share.

Thanks in Advance.

Regards
E*******_RND

Hi!

LA size is limited by paging. Paging depends on traffic profile, of course.
And GPRS/EDGE generate pages as well.

In our network, one LA can handle over 2000 Erlangs of voice.
Thus, we have some capacity for for New Year overload etc.
In E///, remove PAGLIM from TRHs, it is no more needed.
Decide if you can do NCOMB BCCH: takes some SDCCH capacity, but increases paging.
AGBLK=0 adds some capacity as well.
If needed, add multiple CCCH, and enough Abis capacity: then you might handle much more.
Common LA 2g/3g needs some more paging capacity, but as there is less LAU, it is worth it.
Use TMSI for both first and second page: global IMSI pages were needed
15 years ago, no terminal is forgetting TMSI today.

So, look at paging stats. Watch cells for rejected pagings.
Look at last new year and simmilar events stats.

So, it is not BSC size defining LA, it is traffic.
Small BSC can handle one LA, big one needs more.
Try to avoid LA borders in the city. ANalyze handovers and minize H/O over LA borders.

And last: with layered architecture + MSC in pools, there is no more need to
match LA and BSC areas. One LA can span several BSCs.

BR
s52d

[gprastomo]

Hi,

LAC design in 2G should be based on the paging calculation and it will be depends on the CCCH config (either combined or un combined). Then after you get the number of LAC, you can distribute to all cells. Its better to choose the border LAC which has minimum mobility to avoid LAU frequently on those border.

Basically in the Radio interface, the max teoritical paging capability is around 400k paging per hour. But in practical its better to maintain the paging load around 200-300k paging per hour.

To get this calculation you need to extract the paging stats. Then you can decide how many LAC you will have. Then choose the best border LAC.

[aomma]

The paging block capacity of a BTS
Non combined BCCH/SDCCH cells:
(AGBLK = 1): 8/0.2354 = 33.98 paging blocks/second
Each paging block can fit 4 TMSI pages or 2 IMSI pages. Assuming 6% second pages (IMSI), and no global pages, the number Paging Attempts per paging block is:

4 / (1 + 2 * 6%) = 3.57 PA / paging block (1 PA = 1 TMSI + ¼ IMSI)

(AGBLK=1): 3.57 * (8 / 0.2354) = 122 PA / second

(AGBLK=1): 1.12 * 122 = 137 Paging Commands / second

(AGBLK=1): 137 * 3600 = 493200 Paging Commands /hour

You can compare with statistic

The Paging commands/hour is calculated by:
Pag_Int = NLAPAG1LOTOT+ NLAPAG2LOTOT+PAGPSBSC+PAGCSBSC



You should be monitored statistic after you design it.

Recommend monitor in cell CCCH (AGCH + PCH)




Percentage of Page discards --> PCH



Number of Immediate Assignment --> AGCH



aomma

[Ericsson_RND]

Dear Experts;
Many thanks for your usual support.
I would like to know if we are not familiar with the subscribers’ behavior and the network is new is there any estimation number of TRX to be designed per LAC.

Note than: The BSC is E******* 07B, and the Cells are Non combined BCCH/SDCCH.

Thanks for hard efforts

Regards
E*******_RND

[s52d]

Dear Experts;
Many thanks for your usual support.
I would like to know if we are not familiar with the subscribers’ behavior and the network is new is there any estimation number of TRX to be designed per LAC.

Note than: The BSC is E******* 07B, and the Cells are Non combined BCCH/SDCCH.

Thanks for hard efforts

Regards
E*******_RND

2000 Erl of traffic.
This might be 1000 one TRX cells, or 100 four TRXes cells.

[Ericsson_RND]

Dear S52d;

Thanks for your response, is there any document concerning these values.


Regards
E*******_RND

[s52d]

Dear S52d;

Thanks for your response, is there any document concerning these values.


Regards
E*******_RND

Hi, look for Erlang B formula! Erlang (unit) - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Erlang_%28unit%29)

Of course, there is no "only 1 TRX" or "only 4 TRX" networks, so you have to
do it for yourself.

[sran]

Dear S52d;

Thanks for your response, is there any document concerning these values.


Regards
E*******_RND

Given the Erl, you may need GoS (assumption or requirement from customer) in order to figure out the number of TCH channels.

Note that these channels are of 16Kbps in the air interface.

One GSM carrier (TRX) can accommodate such 8 channels.

[sran]

Hi!

...
Common LA 2g/3g needs some more paging capacity, but as there is less LAU, it is worth it.
...
BR
s52d

Hi s52d,

You mentioned about common LA for 2G and 3G. Could you please clarify more about this? Or you have any related tech docs?

Thanks,
sran

[s52d]

Hi s52d,

You mentioned about common LA for 2G and 3G. Could you please clarify more about this? Or you have any related tech docs?

Thanks,
sran

http://www.finetopix.com/live-optimization/11554-common-la-between-2g-3g.html

[revolution]

HI Friends
I have some docs regarding LAC Design .

I hope it is useful

I will try to find somthing else

BR

[revolution]

18953

18954

HI Friends

Sorry

I re attached the Docs

BR

[zeldalcl]

Hi Man!
Do u have any LAC dimensionning Formula template (excell format) may be in 2G.

BR!