optimization

Hello Tufail,

It would be nice of you to give further details about “antenna hopping” …
As far as I could find on internet, this is usually called “spatial diversity”, isn’t it ?

Karthi,

It’s quite surprising to reduce the drops by implementing spatial diversity on “faulty” cells. I agree this solution will work, but :

1: The diversity should already be installed by default on all your GSM sites. It’s almost a mandatory step in order to maximize the coverage and the “radio quality” of your cells.

2: The spatial diversity depends on your antenna configuration. Meaning that if you want to use spatial diversity, you need to replace the current antenna (from vertical polarization to cross polarization), or add a second antenna (+ 1 vertical polarized antenna). It’s not just a radio parameter you can “enable” when you want.

I don’t know… is antenna hopping = space diversity ?

Regards,

Antenna hopping has already delivered on our vendor. It is diversity technique for DL path, namely Tx Diversity.
Downlink performance is limited by multipath fading and interference “holes”. Using frequency hopping can only partly compensate for that limitation.
By combining Frequency and Antenna Hopping the multipath fading can be significantly reduced.
The peformance improvement is dependent on (multiplication of)
# of frequencies and antenna locations;
# frequency and antenna combinations.
It requires two trasnceiver module to handle single TRX funtionality.
Up to 3 dB gain by hopping on two uncorrelated antennas for low speed terminals in urban environment, even higher gain for quasi static mobiles and indoor coverage by outdoor BTS.
Keep bear in our mind that normal radio design is limited by capability of equipment being used when we’re calculating the link budget which is normally higher path loss occured on the UL since power transmitted by the MS lower than BTS.
In case you enhance DL gain using Antenna hopping you have to compensate the UL gain.
In Karthi case, i assume that that it was frequency hopping since activation of antenna hopping is requires quite alot of effort.

In every post, someone is talking about something different. So I’ll write this “recap”, and please comment on this…

There is 2 types of antenna diversities :
the RX diversity and the TX diversity.

And there are two ways to implement them : with crosspolar antennas (2 branches per antenna) or vertical polar antennas (1 branch per antenna)

The Rx Diversity is a very standard feature of a BTS : two or four branches are used to collect the signal from the MS’s.
It improves the UL sensitivity by 2 to 6dB, depending on environment and MS speed.
In urban areas, crosspolars are recommended.
In rural / open areas, vertical polars are recommended.
Average gain in UL RX for 2-Rx Div = 3dB
Average gain in UL RX for 4-Rx Div = 5dB

The Tx diversity is quite recent, and is used by the BTS as well : two branches are used for emitting the DL signal :
the power is increased by 3dB (double power) and 2 to 3 additional dB’s are gained thanks to diversity. Therefore the DL TX is increased by 5 to 6 dB.

aso,

i said v-pol for rural and open areas..
Not urban !!

Xpolars in rural/open don’t work : there are not enough multipath reflections to induce a change of polarization of the MS Tx signal.

Therefore the signal that reaches the BTS antenna has only one polarization, and not multiple polarizations. The signal is not decorrelated enough.

V-pol in urban works fine, but they use more space, bigger support structures, etc. It is vsually preferable to use X Pol. X pol and V pol achieve the same gain in urban areas, so it’s just a matter of installation costs / impacts.

regards,

How do you activate TCC (Transmitter Coherent Combining) on Ericsson system? I mean parameters required to do it.

What are the possible reasons for SDCCH drop and what are thier remedies?

yang,

everything is explained below.. any particular question ?