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can anyone tell me what is MAIO (Mobile allocation offset index)
can anyone tell me what is MAIO (Mobile allocation offset index)
In a hopping group (a set of frequencies to hop over) as defined by the MA (mobile allocation, i.e. which the frequencies are), there can be as many (actually BPCs) full-TCH channels as frequencies. The channels are denoted by the their “offset” (from zero) in that group. (offset = 0..number_of_freq-1)
The offset is actually a add (modulo) to make to the ARFCN (frequency compared with a “base-hopping frequency sequence”)This index is used to prevent interference among the TRXs of the same cell(as they are using same MAL so same MAIO will interfer each other).Different TRX should have different MAIO of the same cell to prevent interferences between them.
Suppose,if you have 4 TRXs in a cell that is using SFH,u can set the MAIO 0,2,4 for the 3 TRXs (3 MAIO for 3 TRXs as the BCCH TRX cannot HOPE in SFH).hello RH,
why do you set the MAIO with an offset of 2:
MAIO 0, 2, 4, 6, …why not:
MAIO 0, 1, 2, 3, …since frequency n and frequency n+1 are not correlated at all (they are probably not adjacent).
that’s something i never understood…
thanks for your views on this,
pixup, for RH…
Hi Pix,
Please consider my example for the case where ARFCNs in the MAL are adjacent.
If they are not adjacent I also dont find any problem to use 0,1,2,3…RH,
But even if the MA list contains adj. frequencies (ie. 50,51,52,53,54,55,56,…,70)
The HSN will order those frequencies in a pseudo random order, so that the ordered list of frequencies might look like:
55,52,63,53,67,61,69,51…
two consecutive frequencies are not adjacent (they could be, but rarely).But all recommendations I have read say that MAIO shall be spaced by 2, even in this example. IMO, whether it is spaced by 1 or by 2 doesn’t change anything.
mmm… actually, it does: if MAIO are consecutive, then it means that one frequency will be used consecutively by all TRX of the cell. For instance, 12 TRX, Maio=0,1,2,3…11. The frequency #11 in te MA list will be used by all TRX in a row, during 12 consecutive TDMA frame.
whereas a spacing of 2 MAIO means that one frequency will be used during 1 TDMA out of 2. In previous example, f11 will be used during 12 alternate TDMA out of 24.
I don’t know if it makes sense? 🙂 Am I correct you think ?
Hi Pix,
I am not so much expat in this.As my simple understanding I realize as below.Please let me correct if I am wrong.
Mobiles, using the same Mobile Allocation and the same timeslot in a TDMA-frame must have
different MAIOs.
MAIO-Indicates the start position (frequency) of the MA list to start the hopping sequence algorithm.
So,if the MAL are of adjacent frequency and MAIO=0,1,2,3…then the same TS of different TRX should have always adjacent frequency if we use the same HSN for all the TRX in the same cell.but the MAL is not made of consecutive frequencies.. for instance the frequencies 50 -> 70 are randomly “mixed” accordingly to the HSN number.
Therefore, MAIO 0 = f1, MAIO 1 = f2, but f1 and f2 are not consecutive.I think my explanation below is valid until someone else states otherwise 😀
Let us take a cell with 4 TRX.
TRX-1 BCCH so lets forget it.
TRX-2
HSN-2
MAL= f1 f2 f3 f4 f5 f6 f7 f8 f9 f10 f11 f12 f13 f14.
MAIO=2TRX-3
HSN-2
MAL= f1 f2 f3 f4 f5 f6 f7 f8 f9 f10 f11 f12 f13 f14.
MAIO=4TRX-4
HSN-2
MAL= f1 f2 f3 f4 f5 f6 f7 f8 f9 f10 f11 f12 f13 f14.
MAIO=6All the TRX (from 2 to 4) are IDLE at a time (say).
A MS1 gets a TCH on TRX2. In RF/SFH case the TRX2 will start the hopping from f3 and will follow the HSN2 pattern. If in-between this another MS2 is allotted a TCH on TRX2 then it WILL NOT start hopping from f3, It will follow the MS1…the frequency the MS1 has transmitted in the last TDMA frame or the frequency MS1 is going to transmit on in the coming TDMA. After that HSN2 pattern will be continued.
At the same time if an MS3 is allotted a TCH on TRX3 then it will start at f5 (as MAIO=4) and will follow the HSN2 over MAL.
But even the use of MAIO doesn’t guarantee the exclusion of interference.
Take a case with reference to above.
MS1 AND MS3 request comes to network at such a time that there is a difference of two TDMA frames between them.
So, when MS1 was at f5 the MS3 starts from f5. As the HSN are same for both the TRX’s the both MS’s ie MS1 and MS3 will now follow the same frequencies during the whole period for which they remains in the dedicated mode.
Hence I am of the opinion that it is not the MAIO, which is criticle, but it is the HSN.
Unfortunately what i have seen is that HSN is kept same in RF hopping by the RF planners even though there is no scarcity of it.
Regards
MKTMKT,
All TRX are synchronized and they start their hopping sequence at the exact same time.
It’s not the arrival of one MS that will start the sequence.
In your example, the MS3 on TRX3 will use a frequency f10 at TDMA = i. This frequency f10 is going to be used by MS1 on TRX2 during TDMA = i + 2 (the MAIO difference between TRX 2 and TRX 3).
In other words, TRX 2 is always 2 frequencies behind TRX 3:
initialization of TRX:
TDMA = 0, TRX 2 = f2 (MAIO2), TRX3 = f4 (MAIO4)
next TDMA
TDMA = 1, TRX 2 = f3, TRX3 = f5
TDMA = 2, TRX 2 = f4, TRX3 = f6
TDMA = 3, TRX 2 = f5, TRX3 = f7
…It’s always like this, whether or not there is a MS on a TRX or not. Even when a TRX is “idle”, the sequence continues (even though there are no frequencies emitted in the Air)
Regards,
PixHi all,
After frequency planning from BBH to FHS on Alcatel BSS we observed hight increase of HO cmd, multiply by 4 beetwen cell 1 and cell 2 (in fact all cell impacted in this FreqPlan).
HO cause are mainly ping-pong on level_UL and better cell, obviously due to interference.
Do you think the same HSN can be the root cause for this or is there something else ?
tx in advance.
Cell 1
======TRX 0 :
——-
FREQ = 15TRX 1 :
——-
FREQ = 46,41,36,31,32,42,47,48,43,38,33,34,39,44,49,50,45,40,35,30,29,28,27,26,37
FHS ID = 1
HSN = 25
MAIO = 10Cell 2
======TRX 0 :
——–
FREQ = 10TRX 1 :
——-
FREQ = 46,41,36,31,32,42,47,48,43,38,33,34,39,44,49,50,45,40,35,30,29,28,27,26,37
FHS ID = 1
HSN = 25
MAIO = 20TRX 2 :
——–
FREQ = 46,41,36,31,32,42,47,48,43,38,33,34,39,44,49,50,45,40,35,30,29,28,27,26,37
FHS ID = 1
HSN = 25
MAIO = 22hello flo,
Level UL and Better Cell HO increase is not a consequence of interference !! It means that your TRX are transmitting with less power than before.
What about UL QUAL HO, DL QUAL HO, UL INTERFERENCE HO, DL INTERFERENCE HO, do you notice anything ?
can you check the value of the PathBalance_avg for those cells ? (can be found in the list of indicators)
Finally, are you saying that the problem occurs in all cells of your network ??
There was an issue with some Alcatel trx (TRADE or TRAGE), but it generates huge amount of HO Quality and a very poor Call Setup Sucess Rate and Call Drop Rate. You can check the TRX Assignment Efficiency % (it’s an indicator that you will find in RNO, under “TRX”) per TRX.
But this problem doesn’t lead to Level problems and HO pingpong.
Regards,
PixHi Pix,
The problem occurs on all cells impacted by the freq plan to FHS.
– You were right, HO cause DLQ and ULQ also increase, the thing is that we modify the threashold HOqual from 2.9 to 3.9 so it’s back to normal.
– HO cause DL-level and UL-level increased as well (multiply by two).
– HO cause Better cell is the worst (2500 -> 4000/day). We set anti PP to 5 secondes and handicap to 15db but with no effect.
Path_balance_avg for cell 2 is between 3.25 and 4, and for cell 1 it is more or less 1.1.
– TRX_ass_efficiency is still very good thus it seems not to be related to the TRX.
– Noisy calls due to UL interference is stable but due to DL interference increase.
– Noisy call DL and UL due bad coverage also increase by 3.
– RxQual distrib is still good, unfortunatly there is no history in RMS data.
Thank you and BR,
Flo
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