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4th April 2010 at 17:15 #61949DaliGuest
I’m currently developing application to locate MS in GSM network based on Timing advance of the served cell and Rxlev of neighbor cells. so please could you tell me how neighbor cells send their Rxlev to the MS and what is the difference between the messages BS power control and MS power control4th April 2010 at 20:34 #61950PixGuest
MS is measuring the BCCH level of each neighbour and reporting the 6 strongest to the BSC.
The neighbours are not “sending” the RxLev.
Rxlev is a measurement !
different between MS Power control and BS power control
MS PC : it is the Tx Level of the MS, absolute power.
BS PC : it is the Tx level of the TRX (on that timeslot). The value shown is an “attenuation” compared to the max power of the TRX (= relative power).
pix4th April 2010 at 21:05 #61951DaliGuest
Thank you Pix for your kind answer, i have took traces on the air interface, i find Timing advance value and many differents measures sent by MS but i can’t extract real values, can you please guide me and advice? and does the MS send the RxLev to BSC of the neighbor cells in which format?5th April 2010 at 07:48 #61952pixGuest
the MS sends measurement reports in UL.
this message is a list of measurements
DL RxLev of the serving cell : 0 = -110dBm, 63 = -47dBm (or more)
then all the neighbours :
index (= 1 to 6) ; BSIC(i) ; DL RxLev(i)
the index is defined by the BSC for each neighbour, for example, cell A is the serving, cell B and C are neighbours. The BSC send in DL (in the SACCH SI2) the list of neighbours and their index :
cell B BCCH = 47 ; index = 1
cell C BCCH = 51 ; index = 2
the index is actually the position of the cell in the neighbour list.
The MS does not report the Timing Advance to the BSC, it is the BSC that sends the current T.A. to the MS (in DL).
Be sure to look at the correct message, it sounds like you are looking at DL messages…13th April 2010 at 06:35 #61953JACKGuest
I NEED YOUR APPLICATION AND I CAN HELP YOU TO DEVELOP IT.
PLEASE EXPLAIN YOUR POJECT.
I THINK GIS IS THE BEST SLOUTON.13th April 2010 at 22:19 #61954DaliGuest
Thank you Pix for your kind answer, @Jack: the aims of the project is to develop application using Java environment, the location of MS in the GSM network using only the TA gived by the serving BTS (we can get the distance from TA) and the RxLEV measured by the MS of the neighbor Cells, but the problem here how to know the distance between the MS and the others neighbor cells basing on the RxLEV only?14th April 2010 at 06:12 #61955PixGuest
It is impossible to compute the distance based on RXLEV only. You need to get the TA for that. That is th whole purpose of the TA.
If the RXLEV could be translated into TA, then the TA wouldn’t exist 🙂
Cheers$pix14th April 2010 at 07:17 #61956DaliGuest
Thank you Pix for your quick reply, but the neighbor cells didn’t give us the TA, only they inform us about the RXLEV you see?14th April 2010 at 08:42 #61957PixGuest
Yes yes, i understand that 🙂
Now, you must understand that there is zero correlation between the RxLev and the distance.
The only way would be to force the MS to handover to the neighbour cells. But that is probably impossible to do (only test mobiles are allowed to force these artificial HO… but forcing it on standard phones would seriously degrade the QoS statistics and voice quality !)
You know, 3GPP already worked hard on trying to localize MS. They came up with the GPS positionning features :
1/ MS is not GPS-capable : the available location of the MS is based on serving cell’s coordinates + serving cell’s TA + sector orientation. That gives a rough idea of where is the MS.
2/ MS is GPS capable : the BSS asks the MS to retrieve its coordinates by GPS and report them back to the BSS.
3/ same as 2, but here there is also a GPS server in the BSS, to speed up the GPS localization of the MS.
pix14th April 2010 at 10:25 #61958RF trackerGuest
can anyone explain me obout TNDROP in ericsson system.
BR//15th April 2010 at 19:53 #61959DaliGuest
Hi Pix, can you please tell me, what is the max power emitted by cell, and can you give me the relation between signal attenuation? i mean is there formula? and thx16th April 2010 at 08:52 #61960pixGuest
max cell power = TRX power – Combining losses – Feeder losses – Jumper losses – “Main” losses (TRX/ANC cables & ANC/BTS cables) + Antenna Gain
Typical values :
Combining loss = 4.5 dB for 1 ANC & 3.5dB for 1 ANY
Feeder = 6dB loss / 100m
Jumper = 1dB loss / 1m
Main = 0.2dB loss / cable
Antenna Gain = +17dBi
Cell power = 46.5 – 4.5 – 3dB – 2dB – 0.4dB + 17dBi
pix23rd April 2010 at 18:03 #61961DaliGuest
Pix Please i will ask you a stupid question :), what is the difference between dBi and dBm? the power measured the MS is in dBi or dbm?
just other point, i find that the attenuation of the power emitted by the BTS is in function of (1/r2) with r is the ray of the BTS magnetic field sphere.
please can you confirm this information and advise
Dali23rd April 2010 at 20:23 #61962pixGuest
no stupid question, don’t worry 🙂
dBi is a “gain” from an antenna. It is not a power. Just a difference of power : what is out from the antenna = what is in + the gain.
For example, take one antenna with gain = 15dBi
if you input 40dBm in the antenna, the output will be 55dBm.
However, you understand that the antenna doesn’t “produce” energy. It just redirects the energy forward, in the front lobe, while it removes energy from side, top, bottom and behind 🙂
It is a “directional” antenna… and this “gain” comes from the comparison with a “non directional” antenna, also called “isotropic” antenna.
dB also follows the same principle, it is a “gain” or a “loss”, in other words dB is a difference of powers.
dBm is an actual power.
0dBm = 1mW
3dBm = 2mW
33dBm = 2W
36dBm = 4W
Attenuation of power from an antenna, it increases with the distance from the antenna.
Usually, the attenuation is function of log(d).
… what is r ?
and what about the magnetic sphere ? I never noticed that antennas acted as giant magnets… :))
Pix26th April 2010 at 10:22 #61963ManiaGuest
Great explanation PIx.