- This topic has 83 replies, 1 voice, and was last updated 14 years, 11 months ago by kuldeep.
26th September 2005 at 11:58 #36643JDGuest
I m new in RF optimization. Please could u answer few my question that will help to clear some basic conecpt.
We r using ericsson R10 system. We have three sectors per cell. Total no. of freq. are 25 i-e 1-25. In most of the cells we r using 4:4:4 config.
Freq. 2-16 are BCCH frequencies. 17 is gaurd band. Rest is hopper. In each sector 29 Ts for TCHs. 2 for SDCCH and 1 for BCCH.
My questions are:
1) if there r 4 radio is there any priority exist. I mean 1st then 2nd …
2) Is BCCCH on always TS0 OF trx1. Can we place to TS0 of radio 2?
3) Where do we place SDCHHs, is like first SDCCH on TS1 OF radio 1 and 2ND SDCCH ON TS1 OF radio2.
4) As a mentioned the hopping freq. How does it work, i mean in 1 sector where there are 4 radios.
Does it aassign all the hoping freq. per radio or does it take all four radios together.
5)if both the BCCH and SDCCH is on radio 1 and in case of radio 1 switch off or got some problem then what gonna happen.
As i m new in this area thats why i m bit confused.
Kindly explain me these things.
Thanks and regards.
JD27th September 2005 at 05:55 #36644RaksGuest
i cannot answer all of your answer execpt os 5. if your tx1 having bcch and sdcch fails then bcch & sdcch is transferred in second tx and any call which is present in TS0&TS1 of tx2 is dropped.27th September 2005 at 07:13 #36645ChefoGuest
Hi JD, I’ll try to answer all your questions.
1. The priorities during TCH assignment are vendor specific and as I don’t have Ericsson experience I am not sure about your case. There are some features in assignment priorities to have some more loaded and less loaded frequencies or your BSS may use pseudo-random assignment sequence. Refer to your vendor’s documentation for this.
2. The BCCH is ALWAYS located on timeslot 0 on the TRX which carries the BCCH frequency (not mandatory to be TRX 1).
3. As SDCCH has very important role during call setup and all assignment procedures, it should use the most clean of interferences frequency as is a frequency from the BCCH set. Normaly the timeslots are 1, 2, etc. in case of combined BCCH/CCCH. In case of bigger cells you can spread SDCCHs of the other TRXs, using timeslots 0, 1, etc.
4. When you are using base-band hopping and the assigned timeslot is different than 0 then normaly you are hopping over all available frequencies. In case of timeslot 0 – the hopping list is all the frequencies except the BCCH freq. BCCH does not hop!
5. In case of BCCH TRX failure, depending on the vendor’s software release there is a possibility for the cell to continue operation in degraded mode. After detection of such failure the structure of the BCCH frequency is transfered to the second TRX and all the calls in this cell are released. Normaly this procedure takes from 30 sec. up to 2 min. (depending on the vendor and the load of the BSC)
I hope that this answers all your questions.
Chefo27th September 2005 at 15:48 #36646BOBOOGuest
1) You must take into account the feature of your vendor. According to my nortel’s experiences, there is a priority for the TS allocation like hereunder:
1st : TRX hopping & without interference
2nd TRX no hopping & without interference
3rd TRX hopping & interference
4nd Trx non hopping & intereference .
4) frequency hopping depend on several parameters:
At first, the kind of frequency hopping that you want to implement (SFH or BBH)
And the Vendor features.
You must check if you are able to check the MAIO and the MAL. Because some vendor don’t use the MAIO for exemple.
(In case of SFH), They ‘re just going to implement the MAL to each sector. That means you must have 3 MAL in your case. Another vendor will implement 1 MAL by site with 1 MAIO by sector.
Don’t forget in SFH, the BCCH TRX aren’t supposed to hope
5) in Nortel features, you are not allowed to lose BCCH TS. If there is a problem on radio 1, the BCCH switch on automatically on radio 2 (or radio 3 if radio 2 has also a problem).
I hope I helped you. Don’t hesitate if you want more information.
BOBOO29th September 2005 at 05:05 #36647JDGuest
Thanks Chefo and BoboO for your help. It really helped me alot. Please do not mind if i ask questions more frequently as i m new in this field.
JD30th September 2005 at 07:49 #36648JDGuest
Hi Chefo & Boboo,
We have dual band (900/1800) on our sites. We r facing intra cell HO probelm i-e when the calls on DCS with signal strength of around -89dbm with RX_qual from 0-2, in this case the SS of 900 band is better than SS of DCS band so it handovers to 900 band, after HO to 900 band on the basis of SCLD=ON it checks the traffic load threshold on 900 and again HO back to 1800. This is a very chronic issue and you might know that
Increase in HO rate = Suspected Increase in Drop call rate.
We r using erisson and the value we have set for LOL=130 with LOLHYST=3?
Any suggesion regarding this issu.
JD30th September 2005 at 12:52 #36649ChefoGuest
Is it “dual-band” or “concentric” cell?
Try to make signal strenght difference smaller (power reduction on 900 or something else). Then try to adjust the HO parameters (I am not familiar with Ericsson, sorry) to avoid these “ping-pong” HOs,
Chefo1st October 2005 at 07:20 #36650JDGuest
It is dual-band. 1800 defind in OL and 900 in UL. LOL=150, LOLHYST=3, FBOFFS=8.
I think we have to play with these values in order to stop ping-pong handover.
Wht do u think?
JD4th October 2005 at 08:53 #36651BobooGuest
Even if I didn’t understand what is OL & UL. I will try to help you.
I’m not familiar with ericson parameters but for manage HO, you must tune the HO margin parameters. It ‘s a margin to use for PBGT handovers to avoid subsequent
handover, in PBGT formula. This handover is preventive and ensures best allocation of a serving cell for a given communication. Usually it is set at about 5 dB.
you must increase or decrease its value in order to impact HO.
Set in a upper value in the way 900 to 1800 shoud be favour the layer 900.
Set in a negative value in the 900 to 1800 should be favour the layer 1800
This parameters is set in the adjacent cell handover parameters for Nortel. Maybe it ‘s the same in ericson.
Pay attention because it could impact congestion on your layer that you would favour.
Tell me if you need more information.
Boboo4th October 2005 at 09:07 #36652JDGuest
Sorry but could not understand fully. What does PGBT stand for?
Can u explain me in detail?
JD4th October 2005 at 10:00 #36653BobooGuest
PBGT stand for “power budget”.
what kind of details do you want to know ?
Boboo6th October 2005 at 08:32 #36654samGuest
i have few question:
1. on forward channel we have BCCH & SDCCH reserved on TS0&TS1 on one of TX but which logical channel we have which correspond to BCCH & SDCCH timeslot TS0&TS1 on Reverse channel ?
2.Where do this cyclic multiframe & superframe repeat? On one site, one bts or complete network.
3. what is difference between SFH & base band hopping? Do channel containing BCCH & SDCCH hops?
4. what are protection ratio for co-channel& adjacent channel?
5. you are given a area to cover say 1,000 kmsquare with 5,000 subscriber & planning tool? which are the minimum set of parameters you start with.just mentioned the steps only.
pls reply,thanks in advance,
sam7th October 2005 at 04:42 #36655M.ThyagarajanGuest
1. BCCH is only on the forward direction and not in the reverse direction.(it is only in the Downlink).For SDCCH it is a subtimeslot in TS1 it self.
2.It has to be at the network as well as the Mobile has to syncronise with the network to get to be able to be in TDM(time division multiplex).
3.BCCH TRX is not allowed to be in hopping.(the types of hopping u mentioned can be searched on the net.).
4.What do u mean by protection ratio.
If u mean C/I for cochannel and adjaent channel.
they are network specific it depends on the desigh and number of frequencies u have.
5.u need to have the min erl per subcriber that u predict,then by multiplying u 5000 and this merl u can get the total erl of the area and then u get the minimum number of sites as well as the site configuration based on the frequency specturm that u have u can plots the sites and get the prediction on the planning tool. Then u have to have the link budget and the model tuning done on the area u are planning for and there are some more steps.7th October 2005 at 09:46 #36656samGuest
Thanks Mr.Thayagarajan, your reply helped me but still i have small doubt like,
1. it means that ts0 on reverse channel doesn’t carry any information.
3. do we have sets of hopping and non hopping frequency?
5.you mean link budget between site and possible subscriber??
also, what is Model tuning? please mention steps ahead?
sam10th October 2005 at 03:24 #36657rhemGuest
im using ericson tems DT tool. In the error report it always indicates sync report not decoded. Can anyone tell me what this message implies?