GPRS/EDGE Capacity dimensioning

[cormon]

Hi, I've problem in GPRS/EDGE Capacity dimensioning for "Existing GPRS/EDGE Network". I've been trying to find the guideline for Nokia Equipment, but only find for new GPRS/EDGE deployment.
My question are around :
- how we calculate CDEF (when do we need to add more or reduce the default GPRS timeslot ?)
- what ND report and statistic can we use for CDEF calculation

If anyone have ever been doing this for Nokia BTS please share the guideline for defining CDEF.

Thanks...

[cormon]

Someone with (E)GPRS knowledge please help...

[RF engineer]

Hi, I've problem in GPRS/EDGE Capacity dimensioning for "Existing GPRS/EDGE Network". I've been trying to find the guideline for Nokia Equipment, but only find for new GPRS/EDGE deployment.
My question are around :
- how we calculate CDEF (when do we need to add more or reduce the default GPRS timeslot ?)
- what ND report and statistic can we use for CDEF calculation

If anyone have ever been doing this for Nokia BTS please share the guideline for defining CDEF.

Thanks...

Dear
I will give general view i really not have Nokia but all the idea is the same
normally for dimensioning the PS data you have to do it on the basis of minimum throughput so in GPRS minimum CS is CS1 and CS2 and each coding scheme is used as CS1 is 41% and CS2 is 59% so if you calculated on the basis on their throughput ( CS1 is 8Kb/s and CS2 is 12kb/s) so if you take the percentage for both it will give 10.36kb/s now you have the base line then on the basis on data services( WAP usage,WWW usage and MMS usage) let say in your network
WAP is 10 kb/s ( if you have)
WWW is 40 kb/s
MMS is 40 kb/s
So total is 50 kb/s then you 10.36 kb/s per TS this will give you approx 5 PDCH ( put I PDCH fixed and give rest dynamic) or put all dynamic.
BR
RF

[cormon]

Dear
I will give general view i really not have Nokia but all the idea is the same
normally for dimensioning the PS data you have to do it on the basis of minimum throughput so in GPRS minimum CS is CS1 and CS2 and each coding scheme is used as CS1 is 41% and CS2 is 59% so if you calculated on the basis on their throughput ( CS1 is 8Kb/s and CS2 is 12kb/s) so if you take the percentage for both it will give 10.36kb/s now you have the base line then on the basis on data services( WAP usage,WWW usage and MMS usage) let say in your network
WAP is 10 kb/s ( if you have)
WWW is 40 kb/s
MMS is 40 kb/s
So total is 50 kb/s then you 10.36 kb/s per TS this will give you approx 5 PDCH ( put I PDCH fixed and give rest dynamic) or put all dynamic.
BR
RF

Hi, thank u for your reply.
Question :

- "each coding scheme is used as CS1 is 41% and CS2 is 59%" --> why is the proportion use 41% and 59%, how did u get this number ?

- The proportion of data services (WAP, WWW etc) is based on assumption or on measured statistic counters? or can we just use total payload in PS busy hour ?

- Do this apply also for EDGE ?

Thanks again.

[RF engineer]

Hi, thank u for your reply.
Question :

- "each coding scheme is used as CS1 is 41% and CS2 is 59%" --> why is the proportion use 41% and 59%, how did u get this number ?

- The proportion of data services (WAP, WWW etc) is based on assumption or on measured statistic counters? or can we just use total payload in PS busy hour ?

- Do this apply also for EDGE ?

Thanks again.

for 1st question is you can from GPRS statistic take get your CS1 and CS2 usage and take out the percentage .
for 2nd question it assumption come from marketing engineer when they bring you the download and if you donot have you can use tolal download.
for 3rd question yes you can use the same way but here you use MSC6 as minimum throughput which it is 29.6 kb/s.
BR
RF

[cormon]

Hi, I just found a problem again what about if blocking happen in ps for example showed by "No radio resources are available for downlink/uplink TBF" counter, cause this will affect also the amount of payload for the timeslot calculation (I'm using real payload data from oss measurement). Also what about multiplexing, I think this will affect also the timeslot calculation since this multiplexing related to blocking problem (CMIIW). So, how can we calculate the optimal value for the timeslot regards to this ps blocking ?

Thanks again.

[RF engineer]

Hi, I just found a problem again what about if blocking happen in ps for example showed by "No radio resources are available for downlink/uplink TBF" counter, cause this will affect also the amount of payload for the timeslot calculation (I'm using real payload data from oss measurement). Also what about multiplexing, I think this will affect also the timeslot calculation since this multiplexing related to blocking problem (CMIIW). So, how can we calculate the optimal value for the timeslot regards to this ps blocking ?

Thanks again.

Do you have dynamic PDCH in you system and how much you give it .
BR
RF

[cormon]

For example we have a GPRS only cell with 2 TRX configuration with default parameter set 31% or 4 ts for default/dynamic and 1% or 1 ts for dedicated PDCH. TCH available for voice is 12 (all assigned to Dualrate TCH). From BH PS statistic shows : (by maximum direction uplink/downlink)
PS Hard blocking : 70%
CS traffic at PS BH : 12.7 erl
CS traffic at CS BH : 21.43 and TCH Block 0.67%
TCH Usage CS : 97.8%
TCH Usage PS : 15.8%
Average TBF per Ts : 8.78
Average TS requested : 3.8
TS allocated : 10.4%
RLC Payload : 9111.0643 KByte
Total Thruput per used TSL :12.6 kbps

So how much timeslot is needed for dedicated pdch, aside from adding 1 TRX to cover the CS traffic in BH ?

Thanks again.

[RF engineer]

For example we have a GPRS only cell with 2 TRX configuration with default parameter set 31% or 4 ts for default/dynamic and 1% or 1 ts for dedicated PDCH. TCH available for voice is 12 (all assigned to Dualrate TCH). From BH PS statistic shows : (by maximum direction uplink/downlink)
PS Hard blocking : 70%
CS traffic at PS BH : 12.7 erl
CS traffic at CS BH : 21.43 and TCH Block 0.67%
TCH Usage CS : 97.8%
TCH Usage PS : 15.8%
Average TBF per Ts : 8.78
Average TS requested : 3.8
TS allocated : 10.4%
RLC Payload : 9111.0643 KByte
Total Thruput per used TSL :12.6 kbps

So how much timeslot is needed for dedicated pdch, aside from adding 1 TRX to cover the CS traffic in BH ?

Thanks again.

Sure you can not handle both traffic with 2TRXs because Capacity for 2 TRX with 50% halfrate and having one PDCH as statistic it can be around 13 ERL so there will be no enough TS for PDCH because Priority will be for voice and for the RLC payload which you have if this is for one hour then you have almost 20kbit/s so if taking minimum CS for both CS1 and CS2 which give you almost 13kbit/s minimum you need 2 PDCHs but in your case cell can not give more than one that is why you have congestion expand one TRX and see the congestion is going down.
BR
RF

[cormon]

Do the addition of 2 dedicated PDCH is enough to accomodate also the loss of payload ? Since we don't know how much the actual payload should be.
Cause there is a possibility that the payload can be greater from the value when blocking happen. So is it enough for just using this payload data ?