- This topic has 12 replies, 1 voice, and was last updated 10 years, 6 months ago by Eagle.
29th July 2008 at 00:38 #53275marianoGuest
I’d like to know if drops using freq. hopping due to co-ch or adj interference are because of bad C/I over all the hopping channels.
For ex. in TEMS, I’ve a cell using FH over 5 channels. Several ‘Undecoded SACCH msj’ are displayed before drop occurs.
BR29th July 2008 at 08:11 #53276pixGuest
what are the 5 channels ?
your assumption is good : it is correct to say that there is probably a bad C/I on about 3 frequencies in this list. Maybe not all frequencies though… this is not necessary.
pix30th July 2008 at 06:15 #53277peyoGuest
You’re using base band hopping, right?
in BBH Tch in use is moving from TRX to TRX. SACCH are from FACH which are stolen for TCH so they are moving to. Of course all what can interfer with TCH (co-chan, interference) will interfer with SACCH. which can be a first point for investigation.
You also have strong dependencies with Antennas system. If for any reason antenna path on TRX1 has less loss than antenna path on TRX2 then there will be TCH effect (so SACH effect) .
What i’ll do is stop frequency hopping and try to find any HW issue (TCH losses, BER..)30th July 2008 at 19:07 #53278PixGuest
Baseband hopping is not necessarily moving from TRX to TRX. In alcatel, the BBH is “synthetized” : the TCH remains on the same TRX, and the frequency changes each TDMA frame.
The SACCH, FACCH and TCH are three different channels, each located on the TCH multiframe.
FACCH is stolen from TCH bursts on demand.
SACCH is regularly sent on timeslot 12 of the TCH mframe.
pix31st July 2008 at 03:49 #53279marianoGuest
Yes, pix, usually the cells are using synthetized FH.
In particular, this cell is from Ericsson, but in the network coexists both Siemens and Ericsson.
mariano.31st July 2008 at 06:40 #53280pixGuest
you cannot do SFH on only 5 frequencies.. even if you have just one hopping TRX, you’d need at least 6 or 7 frequencies to achieve good quality (in SFH1x1).
in 1×3, with 5 frequencies, you could have just one hopping TRX max.
could you write down the radio configuration of this cell, exactly ?
pix31st July 2008 at 07:10 #53281BlitzGuest
In our network, we have no problem with configuration 2/2/2 for sites
using SFH system. Because each freq is hopping in MOBALOC, the more you allocate freq for MOBALOC the better you can get quality (C/I) for your network.31st July 2008 at 09:42 #53282pixGuest
that’s exactly what i said. if you use only 5 frequencies in your MOBALLOC, that’s not enough and you’ll suffer from bad quality.
the more the better.
the rule (in sfh1x1) is to have :
no of freq = 8.3 * no of TRX’s
pix31st July 2008 at 11:00 #53283blitzGuest
thanks pix, I thought 5 frequencies you said was for TRX configuration.3rd August 2008 at 08:09 #53284jackGuest
can you tell me where in TEMS you found this message( layer 3 or ,,,,,)5th August 2008 at 00:49 #53285marianoGuest
This messages are under ‘Error Reports’.
Presentation -> Signaling -> Error Reports
BR.6th August 2008 at 12:51 #53286PeyoGuest
you’re no longer using cavity combining block in alcatel BSS?24th September 2010 at 12:23 #53287EagleGuest
Im using huawei equip anf RF hoping and im geting the same error