- This topic has 15 replies, 1 voice, and was last updated 11 years, 5 months ago by Pix.
20th April 2010 at 16:40 #62262campusGuest
what’s the meaning of CHGR0 CHGR1??
thanks23rd April 2010 at 20:33 #62263SHELDONGuest
Loosely put, a channel group is a group of channels which transmit on the same frequency or set of frequencies.
Normally, in every cell, we have the BCCH TRX transmitting on one frequency(usually non-hopping), and some other TRXs hopping on a set of frequencies.
The channels(timeslots) in the BCCH TRX belong to one channel group, usually referred to as CHGR0, because they all on the same frequency. The other channels on the other TRXs( which all hop on the same set of frequencies) also belong to one channel group, referred to as CHGR1. Note that you can have other channel groups other than 0 and 1, eg, you can decide to define a channel group 2 or 3.
SHELDON26th April 2010 at 14:10 #62264campusGuest
thanks for your kind answer; is that called BBH??27th April 2010 at 08:23 #62265PixGuest
No, that is called SFH (synthetized hopping)
in BBH, the BCCH is also hopping (only the TS0 of TRX1 is not hopping)
in SFH, the whole BCCH TRX (the 8 TS) is not hopping.
pix27th April 2010 at 10:33 #62266SHELDONGuest
I didn’t understand your question. BBH is just one kind of hopping, the other being SFH. If you read my post well, I said that all channels which hop on the same set of frequencies belong to the same channel group, regardless of the hopping method.
I think it’s also possible to hop on the BCCH TRX even when you’re doing synthesized hopping. It’s more complicated, but ericsson has a mechanism for implementing it.
SHELDON27th April 2010 at 14:44 #62267campusGuest
sheldon i am sorry , i didn’t read well, i am just a beginner..28th April 2010 at 08:56 #62268PixGuest
Ok, that would be a smart feature 🙂 Alcatel didn’t implement that yet…28th April 2010 at 09:06 #62269campusGuest
hi pix, thank you
but i would ask if you have any easy documentation of HOPPING, please??28th April 2010 at 10:23 #62270SHELDONGuest
Do you have ALEX? If you do, there’s a very good explanation of frequency hopping in there.
Regards28th April 2010 at 10:51 #62271campusGuest
i can have ALEX..
thankx1st May 2010 at 20:40 #62272BijoyGuest
Could you please expalin how BCCH TRX’s TCH Hop in case of SFH and what is is this marvellous feature called in ericsson??
Bijoy3rd May 2010 at 13:40 #62273SHELDONGuest
I really wished I wouldn’t have to explain this here, but since you asked, I’ll give it a try:
First of all, I was just trying to point out the fact that the difference between synthesized and baseband hopping is not in whether the BCCH TRX hops or not.
In baseband hopping, each TRX transmits on a single frequency, whereas in synthesized hoppng, each TRX transmits on all the hopping frequencies. In baseband hopping, you can easily make the BCCH TRX hop because each time you need to transmit a burst on the BCCH, you just direct the burst to the appropriate TRX which is transmitting at the BCCH frequency.
The main problem with hopping on the BCCH TRX is the transmission of the dummy bursts( also known as c0 filling in ericsson), and in baseband hopping, this is easily done. For synthesizer hopping, it’s more complicated, and there are two methods used to achieve it.
1. An extra transmitter operating purely as a c0 filler is used. Anytime there are bursts to be transmitted on the BCCH freq, they are routed to this transmitter. If there are no bursts to be transmitted, then dummy bursts are transmitted instead. This method is in fact, a mixture of both baseband and synthesizer hopping
2. The timeslot handler of one of the transceivers is used only for the BCCH time slot (timeslot 0 of the BCCH frequency)and filling only. Thus, one FULL TRX will be used for ONLY the BCCH timeslot.
I hope this makes sense to you.
Let me add that it is not some extra “marvellous feature” as you said(I sense the sarcasm in there). It is a part of the frequency hopping feature. If you include the BCCH frequency in your hopping list, then one of the two features above is automatically used. If you have ALEX, you can read the frequency hopping document in there. It is well-explained.
SHELDON4th May 2010 at 05:04 #62274BijoyGuest
I think since we need an extra TX or a TRX remains unused to carry Trafic,this concept has remained dormant.
Bijoy4th May 2010 at 06:57 #62275PixGuest
I am too a little disappointed here 🙂 But don’t take it personally, thanks a lot for your explanation.
I think we called it “dummy” TRX in ALU, but it has never been used.
I didn’t understand the difference between the 1st method and the 2nd method. In both case, you need one additional TRX, and that TRX won’t handle traffic. Is that correct ?
In ALU, in BBH, one TRX is using different frequencies. It is called pseudo-BBH 🙂 Each TRX is swicthing frequencies each TDMA frame. The TCH stays put on its TRX. TCH are not TRX-hopping… it is the TRX that is “freq-hopping”. (it is ALU way of doing it)
So you see, the difference between BBH and SFH is not
“In baseband hopping, each TRX transmits on a single frequency, whereas in synthesized hoppng, each TRX transmits on all the hopping frequencies.”
It is rather :
in BBH, if there are n TRX in the cell, there are only n hopping frequencies.
In SFH, number of frequencies is higher than number of TRX.
pix4th May 2010 at 08:28 #62276SHELDONGuest
What are you disappointed about? I was describing the ericsson implementation of frequency hopping, which is what Bijoy asked. And it’s also worth noting that “In baseband hopping, each TRX transmits on a single frequency, whereas in synthesized hoppng, each TRX transmits on all the hopping frequencies.” is how it’s done in ericsson. Also, it’s easy to infer from that statement that “in BBH, if there are n TRX in the cell, there are only n hopping frequencies. In SFH, number of frequencies is higher than number of TRX.”
And this indeed reiterates my point that the difference between the two hopping methods is also not that “in BBH, the BCCH is also hopping (only the TS0 of TRX1 is not hopping). In SFH, the whole BCCH TRX (the 8 TS) is not hopping.” I was trying to point this out as tactfully as possible, that’s why I said “I THINK it’s possible to hop on the BCCH in synthesized hopping”. I don’t like to contradict experts, that’s why I was careful.
I’m not taking this personally…just trying to let us understand each other.
The difference between the first and second methods is that, in the first method, you need an additional TX, with no TS handler, whereas in the second method, it’s an additional TRX, with a TS handler. And yes, that additional TX/TRX does not handle traffic. Bijoy, your statement is very correct…I mean, who would sacrifice an additional TX/TRX just to implement some fancy hopping method? It’s scarcely used, but it can be done.