CHGR0 CHGR1

Hi Campus,

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.

Regards,
SHELDON

Campus,

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.

Cheers
pix

thank you
sheldon i am sorry , i didn’t read well, i am just a beginner..

hi pix, thank you
but i would ask if you have any easy documentation of HOPPING, please??

ok
i can have ALEX..
thankx

Hi Bijoy,

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.

Regards,
SHELDON

Sheldon,

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.

Cheers
pix