ALL THE CHARACTARE ARE IN THIS TIPS ARE REFERED FROM THE RECOGNISED NOTES UNDER THE GUIDENCE OF MY GODFATHER (VIKAS DESHMUKH).
IF THERE IS ANY DOUBT REGARDING TO THIS PLEASE GO TO HELL (ITS VERY EASY TO UNDERSTAND YAAR! ).
DEDICATED TO
MR. VINAYAK GARAD 09423171882 (MY Physicists)
ALL THE RIGHTS TO CHANGE ARE RESERVED TO (No need to give feed back at “khunesl
@gmail.com”)
HUNK IS SHANK
(VICE VERSA) KHUNE S LCELL PLAN TECH. PVT. LTD. PUNE. (INDIAN MULTINATIONAL).
HAND OVER
HAND OVER IS THE PROCESS IN WHICH, THE SERVICE TO THE
SUBSCRIBER IS TRANSFERRED FROM THE SERVING CELL TO
THE ANOTHER CELL DURING ACTIVE MODE OF MS AND THE
CALL WILL CONTINUE TILL MS DISCONNECT THE CALL.
WHY HAND OVER?
A] IN ORDER TO PROVIDE THE BETTER LINK QUALITY TO THE
SUBSCRIBERS.
B] MANAGE THE TRAFFIC DISTRIBUTION AMOUNG THE CELLS
OF THE NETWORK.
OR
1 TO MAINTAIN QUQLITY AND CONTINUETY OF CALLS.
2 CELL SIZE CONTROL IN ORDER TO MINIMIZE TOTAL
INTERFERENCE IN THE NETWORK.
NOTE:
HO IS THE EFFECT OF FREQUENCY HOPPING
GIVE THE SPECIFIC REASON FOR HANDOVER (H.O.)?
REASONS:
•
RECIEVER(RX) SIGNAL QUALITY
•
RECEIVER SIGNAL LEVEL
•
INTERFERANCE
•
POWER BUDGET
•
RX QUAL.: IF THE RX LEVEL BAD AND RX QUAL.IS ALSO BAD
THEN H.O. IS DUE TO RX QUAL.
•
RX.LEVEL: IF THE RX LEVEL IS BAD RX QUAL. IS GOOD THEN
HO IS DUE TO RX.LEVEL.
•
INTERFERANCE: IF THE RECIEVER LEVEL IS GOOD AND THE
RX QUAL. IS BAD THEN H.O. IS DUE TO INTERFERENCE.
•
(Receiver level is nothing but how much amount the signal
strength you get.)
(Receiver quality is nothing but the voice quality which we get
during call.)
(Interference is nothing but the disturbance or unwanted signal)
LEVEL
QUALITY
H.O
GOOD
BAD
INTERFERENCE
BAD BAD RX QUAL.
BAD GOOD RX LEVEL
WHAT ARE THE SHORT COMING IN HAND OVER?
1 CALL DROP
2 FAR AWAY CELL EFFECT
3 PING PONG H.O.
WHAT IS PING PONG HO?
PING HO IN WHICH (UNNECSESARY) NETWORK TAKING
CONTINIOSLY H.O.
LET US SUPPOSE 4 SITES. ARE SERVING IN ANY ONE AREA
THEN THEIR WOULD BE SUCH TYPE OF POINT AT THEIR ALL 4
SITES ARE GIVING THEIR OWN SIGNALS .SO WHEN U ENTER ON
THAT SPOT FIREST HO IS GIVEN TO 2’ND NO. SITE SIGNALS
,AFTER IMMEDIATELY RECIVEING THE 2’ND NO.SITE 3,RD NO
WILL TAKE HO ,AFTER 4’TH……AFTER 1’ST ……..2,ND SO
ON………
SECOND REASON OF PING PONG IS PARTIAL CABLE SWAP. (SEE
AT CABLE SWAP FOR DETAIL)
HOW IT CAN BE AVOID?
SO ALWAYS GIVE
THRESHOLD VALUE
ACCORDING TO
PLANNER OR FIX THE THRESHOLD VALUE.
Or
Adjust the mechanical and electrical tilt.
(Choose one of the above solution because its depends on the
clutter)
If clutter is dense then choose tilt solution because if we adjust
threshold then our QUALITY would be decrease.
WHAT IS THE BAD EFFECT OF PING PONG HO?
NETWORK QUALITY IS BAD.
WHAT IS INTELLIGENT HO?
1 NEAURAL NETWORK
2 FUZZY LOGIC
WHAT IS INTERNAL & EXTERNAL HO?
INTERNAL HO:
INTER BTS:
CALLS TRANSFER BETWEEEN TWO CHANNELS (TIME SLOT) IN
SAME CELL.
INTRA BSC:
CALLS TRANSFER BETWEEN BTS UNDER THE CONTROL OF
SAME BSC.
EXTERNAL HO:
INTER BSC (BSC - BSC):
1 CALL TRANSFER BETWEEN THE BTS UNDER THE
CONTROL OF DIFF. BSC.
INTER MSC (MSC - MSC):
CALL TRANSFER BETWEEN CELLS UNDER THE
CONTROL OF DIFF. MSC.
WHAT IS INTRACELL HO?
IT IS BASED ON THE UPLINK IDLE CHANNEL
UPLINK INTERFERANCE WHEN THE NETWORK LOAD IS
REASONABLE.
WHEN THE LOAD IS HIGH IN THE NETWORK, THE GAIN
OF INTRACELL HO IS LOW.
WHEN THE LOAD IS LOW THEN THE GAIN IS GOOD.
IN CASE OF HANDOVER DEFINE BUT HANDOVER WOULD
NOT TAKE PLACE?
CHECK FOR:
1) CHECK NEIGHBOUR DEFINED OR NOT?
FIRST SEE IN NET MONITER OR TEMS IF YES THEN
FOLLOW 2’ND STEP IF NOT THEN CALL MSC AND TELL
THEM TO DEFINE.
2) IS
FREQUENCY
AND
BSIC
SAME (SEE IN MCOM)
3) CHECK IS THAT FREQ.ON WHICH HO WILL TAKE
DEFINED IN
MBCCH FREQUENCY
LIST OR NOT?
(CALL MSC AND ASK)
4) CHECK NCC PARA (PARAMETER) IS SET OR NOT?
(CALL MSC AND ASK)
2) IS
FREQUENCY
AND
BSIC
SAME (SEE IN MCOM):
AT BELOW SEE 842 IS FREQ. AND (43) BSIC WHERE 4 IS
NCC 3 IS BCC.FREQ. AND BSIC IS SAME DOES NOT MEAN
TO CHECK 842 AND 43 IS SAME!
IT MEANS THE SITE WITH SAME FREQ.AND BSIC PAIR
SHOULD NOT BE IN THE 15 KM OR 20 KM RADIUS
.BECAUSE IF THIS HAPPENED, THEN THERE IS
INTERFERENCE DUE TO FREQ. HIT AND WE CAN’T FIND
IT, DUE TO SAME PAIR WE CANT FIND WHICH TWO FREQ.
ARE HITTING .
WHAT IS BASIC?
BASE STATION IDENTITY CODE IS THE CODE WHERE IN
THE FIRST DIGIT INDICATES NCC AND SECOND DIGIT
INDICATES BCC.
NCC: NETWORK COLOUR CODE
BCC: BASE STATION COLOUR CODE
THE NCC AND BCC HAVE VALUE RANGING FROM O TO 7
NCC: THE NCC IS FIXED FOR AN OPERATOR, SIGNIFYING
AT ANY GIVEN POINT THERE CAN BE MAXIMUM OF 8
OPERATORS IN AN AREA.
BCC: BCC DEFINES THE CLUSTER NO.WHICH MEANS A
GROUP OF 8 CLUSTERS CARRY UNIQE IDENTITY WHICH
ARE USED FOR ANOTHER GROUP OF 8 AND SO ON.
EX. IF BSIC IS 65 THEN 6 IS NCC AND 5 IS BCC
IF BSIC IS 55 AND FREQ.IS 55 THEN HO WOULD NOT
TAKE PLACE.
WHAT IS CLUSTER?
GROUP OF FREQ. CAN BE PLACED TOGETHER INTO
PATTERNS OF CELLS CALLED CLUSTER.
CLUSTER IS A GROUP OF CELLS IN WHICH ALL
AVAILABLE FREQ. HAVE BEEN USED ONCE AND ONLY
ONCE.
THE PRINCIPAL FOR ALLOCATION OF THE BSIC IS THE
SAME AS THE RF CARRIER BUT AT CLUSTER LEVEL
RATHER THAN CELL LEVEL.
MBCCH FREQ:
MBCCH NO. IS THE BCCH ALLOCATION (BCCH Allocation (BA) List is a
list of BCCH frequencies that every Idle mobile in a cell is supposed to
monitor. The list can be of two types - Idle BA List and Dedicated BA
List. Idle is used by Idle mobiles while Dedicated BA List is used by
Dedicated Mobiles. You always don’t need to make two BA lists, it
depends on your planning process whether you will be using single BAL
or BAL rotation or Dual BAL. We can use one BAL for all the mobiles
(idle & dedicated).)
i.e. IT INDICATES TO THE MS THE FREQ.MUST BE MONITERED AND
MEASURED IN IDLE .ACTIVE OR BOTH MODES.THIS NO. IS SENT TO MS
IN THE SYSTEM INFORMATION MESSAGES ON THE BCCH CHANNEL IN
IDLE MODE AND ON THE SACCH IN ACTIVE MODE.
UPTO 32 BCCH CARRIERS CAN BE DEFINED BY
SPECIFAYING THEIR ARFCN.
DEEP CONCEPT OF HO:
THE MEASUREMENT REPORT FROM THE MS IS SENT TO THE
BSC ON THE SACCH INDICATING THE SIGNAL STRENGTH AND
QUALITY OF THE SERVING LINK AND THE
SIG.STRENGTH, FREQ.AND BSIC
FROM THE
SIX BTS
WITH STRONGEST SIGNAL STRENGTHS.
ONLY MEASURMENTS FROM THE NEIGHBOURING CELLS THAT
FULLFILL THE REQUREMENT BY BCCH HAS A FREQ. AS
INDICATED BY MBCCH NO.
IT IS NECESSARY THAT THE MEASURED CELL IS DEFINED AS
THE NEIGHBOUR OF THE SERVING CELL .
UPTO 64 DIFF. CELLS CAN BE DEFINED AS NEIGHBOUR.
HO PROCESS MAY BE TRIGGERED BY QUAL., FIELD
STRENGTH OR DISTANCE VALUES FALL BELOLW /
EXCEED THEIR THRESHOLD PERIODIC CHANGES.
The locating algorithm
: Works out the basis for
handover decisions .It is implemented in the base
station controller. It is the algorithm for cell selection
for active mobile stations (i.e. ongoing connection) after
immediate assignment.
INPUT:
THE I/P TO THE ALGORITHUM IS SIGNAL STRENGTH AND
QUALITY MEASUREMENT FROM THE MS AND FROM THE
BASE STATION CURRENTLY SERVING THE CONNECTION.
OUTPUT:
THE OUTPUT IS THE LIST OF CELLS THAT THE
ALGORITHUM JUDGES TO BE POSSIBLE CANDIDATES
FOR HANDOVER .THE CELLS IN THE LIST IS RANKED
AND STORED IN DESCENDING ORDER OF PREFERENCE
FOR HANDOVEAR.
THE ALGORITHUM WORKS CONTINUESLY, COMPLETING
A CALCULATION CYCLE IN GENERAL EVERY 480 ms.
MOST FREQUENTLY THE ALGORITHUM WILL
RECOMMEND NOT TO PERFORM A HANDOVER.
HANDOVER CRITERIA ARE BASED ON
THREE TYPES OF MEASUREMENT
1] FIELD STRENGTH (SIGNAL STRENGTH AND OR PATH
LOSS) OF THE CONNECTION AND OF
THE
BROADCAST CONTROL CHANNEL
CARRIERS
FOR NEIGHBOURS.
2] SIGNAL QUALITY OF THE CONNECTION (BIT ERRROR
RATE ESTEMATION MAPPED ON ALGORITHUM SCALE)
3] TIMING ADVENCE USED BY THE
MS.
WHAT IS TIMING ADVANCE?
IT IS A SOLUTION SPECIALY DESIGNED TO COUNTERACT
THE PROBLM OF TIME ALLIGNMENT .ITS WORKED BY
INSTRUCTING THE MIS ALIGNED MS TO TRANSMIT ITS
BURST EARLIER OR LATER THAN IT NORMALLY WOULD.
IN GSM TA INFORMATION RELATES TO BIT TIMES
.THUS ,AN MS MAY BE INSTRUCTED TO COMMENCE ITS
TRANSMISSION A CERTAIN NO OF BIT TIMES EARLIER
OR LATER ,RELATED TO PREVIOUS POSITION TO REACH
ITS TIMESLOT AT THE
BTS
IN RIGHT TIME.
WHAT IS THE DIFF. BETWEEN CELL RESELECTION AND
HANDOVER?
HAND OVER HAPPENED IN DEDICATED MODE AND
CELL RESELECTION IN IDLE MODE.
FREQUENCY HOPPING
Call is transmitted through several frequencies in order
to
Average the interference,
Minimizing the impact of fading.
OR
It is defined as sequential change
of carrier frequency on the radio
link between the mobile and base
station.
Advantage of frequency hopping:
Frequency diversity
Interference averaging
How in frequency hopping there is enhancement of
network ?
1
FH
implement will enable more aggressive frequency reuse pattern that leads to better spectrum efficiency.2 It can add more transceivers in the existing site, while maintains the network quality .
3 freq. hopping compressing the available spectrum to make room for extra freq.
Frequency reuses?
FREQUENCY REUSE IMPLIES THAT IN A GIVEN COVERAGE AREA THERE ARE SEVERAL CELLS THAT USES THE SAME SET OF FREQ.
THESE CELLS ARE CALLED COCHANNEL CELLS .AND THE INTERFERENCE BETWEEN SIGNALS FROM THESE CELLS ARE CALLED CO CHANNEL
INTEREFERENCE.
Define all the parameter in frequency hopping?
Following are the parameter in FH
MOBILE ALLOCATION (MA)
MOBILE ALLOCATION INDEX (MAI)
MOBILE ALLOCATION INDEX OFFSET (MAIO)
HOPPING SEQUENCE NO. (HSN)
MOBILE ALLOATION:
IT IS THE SET OF FREQ. The mobile allowed to hope over
.maximum of 63 freq. can be defined in MA list.
MOBILE ALLOCATION INDEX (MAI):
It is the no. ranging from zero to the no. of freq. in the
MA
list
subtracted by one.
It is the output of hopping sequence algorithms
.HOPPING SEQUENCE NO. (HSN):
It determines the hopping order used in the cell .it is possible
to assign
64
diff.setting .when HSN
= 0
provides cyclic
hopping (pattern).
In
GSM
there are 64 diff.patterns of FH.
One of them is a simple cyclic or sequential pattern.
The remaining 63 are known as pseudo random patterns
which an operator can choose from the MA list.
WHERE WE USE CYCLIC AND RANDOM PATTERN?
CYCLIC: IT IS USED IN THE AREA WHERE THE ITERFERENCE
IS NOT A PROBLEM.
RANDOM: IT IS USED IN THE AREA WHERE INTERFERENCE IS
A PROBLEM.(HIGH TRAFFIC AREA).
MOBILE ALLOCATION INDEX OFFSET (MAIO):
Determines inside the FH sequence which freq. the mobile
starts do transmit on.
The value of MAIO ranges between zeros to N-1.
Where N is the no.of freq.defined in the MA list.
Presently MAIO is set on per carrier basis.
What are the types of
FH
and? What is dif.between them?
Two types of freq. hopping.
Base band FH (BBH)
Synthesized FH (SFH)
Diff.:
BBH: IN BBH no. of hopping freq. same as no.of TRX. (TRU)
SFH: No. of hopping freq. can be in the range of 1 to 63.
- here the ARFCN wud be more than the no. Of TRX/TRU in bts.also
we have better hopping gain here.& also we need not to go for new
frequency scheme when we add new trxs to the site as this is to be
do done in Base band hopping.
Definition of SFH AND AMR:
SFH is synthesizer freq hopping and AMR is adaptive multirate. These
two terms are in all different from each other. One defines the way of
using fewer frequencies more efficiently and other defines the way of
controlling the quality of call in FULL RATE as well as HALF Rate so as
to increase capacity indirectly with controlled quality.
What is the effect of freq. hopping?
1 Hand over
2 Call set up
3 Frame eraser rate (FER)
These are the eff. of FH.
What is FER?
IT IS THE RATIO OF DISCARDED SPEACCH FRAMES COMPARED TO ALL THE RECEIVED SPEECH FRAMES.
It is the right measure of voice quality.
It is performed on speech and signaling frame.
FFR 0 to 4 % good
4 to 15 % slightly degrade
Greater than 15 %
FORMULA:
% OF FER = (NO.ERASED BLOCKS÷TOT.NO.
OF BLOCKS) × 10O
Deep concept:
MAIO:
It is a parameter that will allow the operator to specify a list of
up to 32 MAIO values in order in which they are to be allocated to
a channel group. This parameter set to
default
which
removes the manual MAIO list in favor for the default MAIO list.
The no. of MAIO values in list stretches from zero up to one less
than no. of freq. in the HFS.
Ex. 9(0 to 8) freq. their than maio list will be 0 to 7.
The actual MAIO values to be used for a channel group
depend on the no. of TRX in the channel group.
Default list:
In order of the MAIO values in the default list is arranged in a
“first even then odd.” MAIO values manner.
This means that the beginning of the list will consist of all the
even values in ascending order.
After the even values all the odd values are arranged an
ascending order.
Ex.
For hopping group with 9 freq. the default list will be 0, 2, 4, 6, 1,
3, 5 and 7.
MA
: MA LIST IS A LIST OF HOPPING FREQ. TRANSMITTEED TO
A MOBILE EVERY TIME .IT IS ASSIGNIED TO
HOPPING
PHYSICAL CHANNEL.
THE MA LIST IS A SUBSET OF
CA
LIST.
#WHAT IS CA LIST?
THE MA LIST IS AUTOMATICALLY GENERATED
IF THE BASEBAND HOPPING IS USED.
IF THE NETWORK UTILISES THE RF HOPPING
THE MA LIST HAVE TO BE GENERATED FOR
EACH CELL BY THE PLANNER
.
The MA list is able to point the 64 of freq. defined in the CA
list .However the BCCH freq. is also included In the CA list ,
so
The freq. in the MA list is required to be in increased order
because of the type of signaling used to transfer
the MA list.
HOPPING sequence algo?
Input: The hopping seq. algo. Takes HSN &
FN (freq.no.) as an input.
Output: Mobile allocation index (MAI) is the
O/P.
MAIO:
WHERE THERE ARE MORE THAN ONE TRX IN THE BTS USING THE SAME LIST THE MOBILE ALLOCATION INDEX OFFSET IS USED TO ENSURE THAT EACH TRX USES ALWAYS AN UNIQUE FREQ.
EACH HOPPING TRX IS ALLOCATED A DIFF. MAIO.
MAIO IS ADDED TO MAI WHEN THE FREQ. TO BE USED DETERMINED FROM THE MA LIST.
MAIO AND HSN ARE TRANSMITTED TO
A MOBILE STATION TOGETHER WITH
MAIO LIST.
HSN DEFINES WHICH HOPPING SEQUENCE TO BE USED. MAIO DECIDES STARTING POINT OF HOPPING.
WHAT IS SLOW FREQ.HOPPING AND WHAT IS FAST
FREQ.HOPPING?
THE PRINCIPAL OF FREQUENCY HOPPING USED
WITHIN GSM IS THAT:
“SUCESSIVE TDMA BURST OF CONNECTION IS
TRANSMITTED VIA. DIFF. FREQ.”
THAT FREQ. BELONGING TO A RESPECTIVE CELL
ACCORDING TO NETWORK PLANNING. THIS METHOD
IS CALLED SLOW FREQ. HOPPING.
SINCE TRANSMISSIOMN FREQ. REMAIN CONSTENT
DURING ONE BURST.
IN CONTRAST FAST FRFEQ. HOPPING WHERE THE
TRANSMISSION FREQ. CHANGES WITHIN THE ONE
BURST.
DETAILS OF FRAME ERASER RATIO:
IT IS THE RATIO OF DISCARDED SPEACH FRAMES COMPARED TO ALL THE RECEIVED SPEECH FRAMES.
A SPEECH FRAME IS GENERALLY DISCARDED IF AFTER THE DECODING AND ERROR CONNECTION PROCESS ANY OF THE CATEGORY A BIT IS FOUND TO BE CHANGED BASED ON THE THREE PARITY BITS FOLLOWING THEM IN A SPEECH FRAME.
FER IS MEASURE OF HOW SUCESSFUL THE SPEECH FRAME WAS RECIVED AFTER THE ERROR CORRECTION PROCESS AND IT IS THUS A BETTER
INDICATION OF THE SUBJECTIVE SPEECH QUALITY COMPARED TO THE LINK QUALITY IN TERMS OF BER .THE RECIEVER QUALITY DOES NOT INDICATE HOW THE BIT ERRORS WERE DISTRIBUTED IN A SPEECH FRAME.
“THE BIT ERROR DISTRIBUTION AFFECTS
THE ABILITY OF THE CHANNEL DECODING
TO CORRECT THE ERRORS”.
A BLOCK IS ERASED WHEN PARITY CHECK FAILED.
BIT ERROR RATE:
IT IS THE RATIO OF THE NO. OF ERRORNEOUS BIT RECIEVIED TO THE TOTAL NO.OF BITS RECEIVED.
IT IS PERFORMED ON DEMODULATED SPEECH FRAMES THAT ARE NOT MARKING CORRECT.
WHAT HAPPENS WHEN SPEECH FRAMES DISCARDED IN FER?
ANS: SYSTEM WILLS INTERPOLUTE.
SPEECH QUQLITY INDEX DEPENDS ON FER AND
BER.
SPECCH QUALITY IS DEPENDING ON BER.
TROUBLSHOOTING
WHAT IS CABLE SWAP AND PARTIAL CABLE SWAP?
THERE ARE TWO TYPES OF CABLE SWAP/SECTOR SWAP. FIRST CABLE SWAP/SECTOR SWAP AND ANOTHER IS PARTIAL
SWAWP.
CABLE SWAP IS NOTHING BUT WHEN TWO WIRES WHICH IS COMING FROM GSM AND CONNECTED IN TRX/TRU IN BTS WIL CONNECT
WRONGLY. MEANS FIRST SECTOR TWO CABLE (POSITIVE AND NEGATIVE) CONNNECTED IN SECOND SECTOR TRU/TRX OR SECOND
SECTOR TWO CABLE CONNNECTED IN THIRD OR THIRD SECTOR IN FIRST .
WHAT IS THE SOLUTION OF TCH OR CALL
DROP?
BOTH PROBLEMS WOULD BE OCCURRED DUE TO THE POSSIBILITY OF CABLE SWAP OR FREQUENCY HIT.
CABLE SWAP : TWO WIRES CAME FROM THE GSM AND JOIN AT THE TRX IN BTS ROOM. WHILE CONNCTING THESE WIRE THEIR COULD BE MISMATCH OR SWAPPING.BECAUSE FROM THESE TWO WIRES ONE WIRE IS OF
TRANSMETER SECTION (+ SIGN ON THAT CABLE ) AND ANOTHER SIGN IS OF RECIEVER ( - SIGN IS ON THAT CABLE).SO THERE SHOULD BE CHANCES THAT + WIRE WOULD BE ATTACHED TO - AND VICE VERSA.
TWO SOLVE THE PROBLEM OF CABLE SWAP WE WANT TO SEE WHETHER THESE CONNECTION IS EXACT OR NOT.
DUE TO CABLE SWAP THERE WOULD BE CHANCES OF CALL DROP. SECOND CASE:
FREQUENCY HIT: THIS MEANS ADJUCENT FREQUENCY WOULD BE HIT TOWARDS AREA.
SOLUTION OF THIS CASE GIVES DOWN TILT TO OUR GSM.
WHAT IS PARTIAL CABLE SWAP?
THERE ARE TWO TYPES OF CABLE SWAP ONE IS ABOVE AND SECOND IS PARTIAL CABLE SWAP.
IN FIRST CABLE SWAP TWO WIRES ARE FROM ANY ONE SECTOR IS CONNECTED IN ANOTHER SECTOR TRX/TRU .BUT IN PARTIAL CABLE SWAP ONLY ONE WIRE WOULD BE SWAP MEANS ONE WIRE FROM ANY ONE SECTOR
AND ANOTHER WIRE FROM ANY OTHER SECTOR IS CONNECTED AT ONE TRX/TRU.
WHAT IS THE SOLUTION FOR PROBLEM OF UPLINK?
SEE AROUND YOUR SITE ANY CDMA SITE IS PRESENT IF YES THEN USE CDMA FILTER.
IF NOT THEN SEE IS THEIR SECTOR EXPANTION PRESENT THEN CHECK FOR THE ORIENTATION OF BOTH EXPANSION ANTEENA AND MAIN ANTENA IS
DIFF. OR SAME.
WHAT IS THE SOLUTION FOR DOWNLINK PROBLEM?
THE SOLUTION FOR THE DOWNLINK IS SAME FOR THE TCH /CALL DROP.
WHAT IS TH E SOLUTION FOR SD DROP?
IF SD DROP INCREASED THEN ASSIGN ONE MORE TIME SLOT BY USING PLANNER.
WHAT IS THE REASON FOR SDCCH DROP?
1>high interference of freq., like co-channel
2>sdcch time slot faulty
3>poor TRX DL quality
4>hardware fault like antenna or duplexer malfunction
5>may be feeder cable and connectors are faulty.
6>site taking calls from a very far distance.
7>Bad Radio link quality (any sort of interference, if highly) Bad Radio
link quality (any sort of interference, if highly destructive)
8>Could be a problem at NSS end
and may be some other reasons....
SD drop happens after SD is assigned, and if TCH is not free but SD is
assigned and there is no directed retry, then in that case what
happens? SD waits for a timer value and then also if it doesn't find a
TCH it can't hold SD, so drops………..
WHAT IS VSWR?
VOLTAGE WAVE STAND RATIO:
IT IS THE RATIO OF FORWARD POWAR TO THE REFLECTED POWER.[(1-ROW)/ (1+ROW)]IT THE PROBLEM OF LOOSE CONNECTOR OR DUST OR SHARE
BENDING OR RAIN WATER . DUE TO THIS PROBLEM THERE IS LESS COVERAGE IN THAT AREA.
WHENEVER THIS PROBLEM OCCURRED THERE IS ALARM FOR THIS IS IN
THERE ARE LOTS OF TYPE OF ALARMS ANOTHER IS IF BTS DOOR IS OPEN THEN THERE IS ALSO ALARM WILL OCCURD IN MSC.
TO SOLVE THE PROBLEM OF VSWR PROBLEM WE CONNECT TIGHTLY (LOOSE CONNECTOR) ALL CONNECTOR/CABLE WHICH ARE LOOSE.
WHAT IS TEMS?
TEST EQIPEMENT MOBILE SYSTEM IS A TESTING TOOL USED TO READ AND CONTROL THE INFORMATION SENT OVER AIR INTERFACES BETWEEN BASE
STATION AND THE MOBILE STATION .IT CAN BE USED FOR
RADIO
COVERAGE MEASUREMENS.IN ADDITION TO FIELD
MEASUREMENT AND POST PROCESSING.
ALL KIT CONSIST OF MOBILE STATION WITH SPECIAL SOFTWARE, A PORTABLE PC AND OPTIONALLY A GLOBAL POSITONING SYSTEM
RECIEVER.THE PC IS USED FOR PRESENTATION ,CONTROL AND MEASUREMENT STORAGE .
MS IS USED IN ACTIVE OR IDLE MODE.
WHICH WINDOW WE NEED TO CHECK IN DRIVE TEST?
1] CURRENT CHANNEL 2]SERVING NEIGHBOUR 3]RADIO PARAMETER 4]C/I
5] C/A
TELL US ABOUT DETAILS?
1] CURRENT CHANNEL:
CELL NAME
CGI (MCC NCC LAC (BSC) CI) BAND 900/1800/1900
CHANNEL TYPE CHANNEL MODE SPEECH CODEC CIPHERING ALGORITHUM
SUB CHANNEL NO. HOPPING CHANNEL
MAIO HSN
2]SEERVING NEIGHBOUR: FULL SUB
HERE THE DEFINED NEIGHBOUR WILL APPEAR.
3]RADIO PARAMETER : FULL SUB
A] RX LEVEL RANGE -10 TO -120 -10 TO -70 BEST
-91 TO -120 BAD PURPOSE NEW SITE AT THIS AREA.
B] RX QUALITY (ITS DEPEND ON INTERFERENCE ) RANGE 0 TO 7 0 TO 3 GOOD 4 TO 5 AVG. 6 TO 7 BAD C] FER ACTUAL D] BER ACTUAL E] SQI 21 TO 30 OK
ABOUT SQI :IF BSIC AND FREQ ARE SAME THEN SQI GOES NEGATIVE.
4]C/I (WORST /BEST) RANGE 5 TO 25
15 AVG. 10 TO 15 5 TO 10 BAD
MS POWER CONTROL LEVEL DTX
TA 1 TA = 500m
(RECEIVING LEVEL)RL TIME OUT COUNTER (MIN) RL TIME OUT COUNTER (MAX)
MS BEHEVIOR MODIFIED
5] C/A
ANOTHER NETWORK PROBLEM:
C/I:CARRIER TO INTERFERENCE RATIO
IT IS DEFINED AS THE RATIO BETWEEN THE LEVEL OF THE RECIVED DESIRED SIGNAL TO THE LEVEL OF RECIVED UNDESIRED SIGNAL. C/I IS DEPENDENT ON THE INSTANTANEOUS POSITION OF THE MOBILE STATION AND IS AFFECTED BY TERREIN DETAILS AND VARIOUS
SHAPES,TYPES AND NO.OF LOCAL SCATTERS.
OTHER FACTORS SUCH AS ANTENNA TYPE DIRECTIONALITY AND HEIGHT ,SITE ELEVATIONS ,POSITIONS AND THE NO. OF LOCAL SOURCE OF
INTERFERENCE ALSO EFFEECT THE DISTRIBUTION OF THE C/I RATIO IN A SYSTEM .
C/A: CARRIER TO ADJUCENT RATIO
IT IS DEFINED AS THE RELATION IN DB IN SIGNAL STRENGTH BETWEEN THE SERVING AND AN ADJUCENT FREQ.
COCHANNEL INTERFERENCE:
FREQUENCY REUSE IMPLIES THAT IN A GIVEN COVERAGE AREA THERE ARE SEVERAL CELLS THAT USES THE SAME SET OF FREQ.
THESE CELLS ARE CALLED COCHANNEL CELLS .AND THE INTERFERENCE BETWEEN SIGNALS FROM THESE CELLS ARE CALLED CO CHANNEL
INTEREFERENCE.
SOLUTION:TO REDUCE CO CHANNEL INTERFERENCE CO CHANNEL CELLS MUST BE PHYSICALLY SEPERATED BY A MINIMUM DISTANCE IN ORDER TO PROVIDE SUFFIECIENT ISOLATION.
WHAT IS BASIC?
BASE STATION IDENTITY CODE IS THE CODE WHERE IN THE FIRST DIGIT INDICATES NCC AND SECOND DIGIT INDICATES BCC .
NCC :NETWORK COLOUR CODE BCC: BASE STATION COLOUR CODE
THE NCC AND BCC HAVE VALUE RANGING FROM AN O TO 7
NCC: THE NCC IS FIXED FOR AN OPERATOR ,SIGNIFYING AT ANY GIVEN POINT THERE CAN BE MAXIMUM OF 8 OPERATORS IN AN AREA.
BCC : BCC DEFINES THE CLUSTER NO.WHICH MEANS A GROUP OF 8 CLUSTER CARRY UNIQE IDENTITY WHICH ARE USED FOR ANOTHER GROUP OF 8 AND SO ON.
EX. IF BSIC IS 65 THEN 6 IS NCC AND 5 IS BCC
IF BSIC IS 55 AND FREQ.IS 55 THEN HO WOULD NOT TAKE PLACE. WHAT IS CLUSTER?
GROPU OF FREQ. CAN BE PLACED TOGETHER INTO PATTERNS OF CELLS CALLED CLUSTER.
CLUSTER IS A GROUP OF CELLS IN WHICH ALL AVAILABLE FREQ. HAVE BEEN USED ONCE AND ONLY ONCE.
THE PRINCIPAL FOR ALLOCATION OF THE BSIC IS THE SAME AS THE RF CARRIER BUT AT CLUSTER LEVEL RATHER THAN CELL LEVEL.
Transmission problem:
Path loss:
Path loss occurs when the received signal becomes weaker and weaker due to increasing distance between MS and BTS ,even if there are no obstacles between the transmitting and receiving antenna .The path loss problem seldom leads to a dropped call because before the problem becomes extreme a new transmission path is established via another BTS .
Shadowing
: Shadowing occurs when there are physical obstacles including hills and building between the BTS and MS .The obstacles create a shadowing effect which can decreases the received signal strength .when the MS moves the signal strength fluctuates depending on the obstacles between the MS and BTS .
FADING DIPS: A signal influenced by fading varies in
signal strength .
Drops in strength are called fading dips.
Multipath fading : It occurs when there is more than
one transmission path to the MS or BTS .This may be
due to building or mountains either close to or far from
the rec
dBi, dBd,dBm
dB itself is a measure of power on logarithmic scale...when we talk
abt dBi (one more thing i want add here is dBd ), these indicate gain of
a given antenna with respect to isotropic and Lambda/2 dipole antenna
respectively....isotropic antenna is a non existent ideal antenna and
Lambda/2 as it indicates is half-wavelength antenna., here iso.. is an
omni directional antenna while Lambda...is a directional antenna ..
When we measure gain wrt iso..Antenna,.gain is more bcoz it radiates
lesser in distance ..bt its less with Lambda/2 antenna ... bcoz its
radiation is directional hence more. Here is the relation...
dBi (gain of the given antenna wrt Isotropic antenna)=dBd(Gain wrt
Lambda/2 antenna +2.15 dB).
READ THIS AFTER LEARN THE DT FOR 10 DAYS!
ANALYASING THE LOG FILES?
AFTER HAVING THE ENTIRE NETWOR OR A GIVEN PART OF THE NETWORK, THE LOG FILES SHOULD BRE ANAYLIESD .WHEN ANALYISING THE LOG FILES ,THE MAIN THINGS TO LOOK FOR :
1. INTERFERENCE
2. LOW SIGNAL STRENGTH 3. MISSING NEIGHBOUR
OFTEN, THESE PROBLEMS CAN BE SPOOTEED BY LOOKING AT THE RXQUAL LEVELS AND /OR DROPPED CALLS.HOWEVER DUE TO LITTLE OR NO TRAFFIC IN THE SYSTEM, IT IS NOT POSSIBLE TO SPOT ALL THE PROBLEMS THAT MIGHT OCCUR WHEN THERE IS MORE TRAFFIC IN THE SYSTEM.FOR EX.
INTERFERENCE FROM THE NON BCCH CARRIERS DOES NOT AFFECT THE QUALITY .THEREFORE IT IS IMPORTANT THAT THE LOG FILES ARE
CAREFULLY ANYLYSED EVEN THOUGH THERE ARE NO SIGNS OF
POOR
QUAL.
POOR QUAL:
THERE ARE THREE MAJOR REASONS FOR POOR QUALITY.
INTERFERENCR PROBLEM, LOW SIG. STRENGTH OR A MISSING NEIGHBOUR. THE REASON FOR THE POOR QUAL.CAN BE:
1. MS DOES NOT ON BEST SERVER 2. INTERFERENCE
3. LOW SIGNAL STRENGTH
MAKE THE NECERRY CHANGES /ADJUSTMENTS DEPEPNDING ON THE REASON FOR THE POOR QUAL.
MISSING NEIGHBOUR RELATIONS:
MISSING NEIGHBOUR RELATIONS DISABLES A HANDOVER AND MIGHT LEAD TO POOR QUALITY AND EVENTUALLY A DROPPED CALL.
INCLUDING ALL THE BCCH FREQ. IN THE MEASURING LIST DURING THE INTIAL TUNING, MAKES MISSING REALATIONSHIP EASIER TO DETECT. NEIGHBOUR THAT ARE NOT INCLUDED IN THE NEIGHBOUR LIST ARE NOT NOT EVALUATED BY LOCATING.
IF HANDOVER IS NOT PERFORMED TO WHAT SEEMS TO BE THE BEST SERVER, THERE IS A POSSIBILITY OF A MISSING NEIGHBOUR RELATION.
IF THAT IS NOT THE CASE AND TH EQUAL.IS POOR, HAND OVER HYSTERISIS, OFFSET, L- CRITERION PARAMETERS (IF USED) AND HCS – PARAMETER (IF USED) SHOULD BE REVIEWED TO FIND THE REASON FOR THE MS NOT BEING ON THE STRONGEST CANDIDATE.
THERE IS SITUATION WE CAN IMPROVE THE COVERAGE, BY INCREASING THE OUTPUT POWER AND/OR MAKING ANTENNA ADJUSTMENTS.
OUTPUT POWER:
BY INCREASING THE OUTPUT POWER,THE DOWNLINK SIGNAL STRENGTH INCREASE .HOWEREVER ,IF THE O/P POWER IS TOO HIGH (APPROXIMATELY -43 DBM OR MORE),A HIGHER O/P POWER WILL NOT GREATLY AFFECT THE OVERALL PERFORMANCE DUE TO THE LACK OF POWER BALANCE BETWEEN UPLINK AND DOWNLINK .
BUT AN INCREASE IN O/P POWER MAY LEAD TO HIGHER INTERFERENCE IN COCHANNEL AND ADJUCENT CHANNEL CELLS.
THE CELL BORDERS ARE ALSO AFFECTED.
ANTENNA ADJUSTMENTS: A HIGHER ANTENNA POSITION GENERALLY
INCREASE THE CELLS COVERAGE AREA .SOMETIMES THE RE – DIRECTION OF AN ANTENNA MAY HELP THE SITUATION. IF THE ANTENNA IS
DOWNTILTED ,A DECREASES OF THE TILT GENERALLY INCREASE THE COVERAGE AREA.
JUST LIKE THE CHANGING THE O/P POWER ,AN ANTENNA ADJUSTMENTS AFFECTS THE ENTIRE CELL PLAN REGARD TO CELL BOARDERS AND
INTERFERENCE.
INTERFERENCE PROBLEM
MAJOR IINTERFERNSE PROBLEMS REQUIRE A CHANGE OF FREQ. ON ONE OR MORE CELLS.
FOR A CELLS SEVERE PROBLEM ,ANATENNA DOWNTILTS CAN HELP SITUATITIONS .
MINOR INTERFERENCE PROBLEM CAN SOMETIMES BE ELIMINATED OR REDUSED BY PARAMETER CHANGES .MOVIING CELL BOARDER AND /OR CHANGING THE HANDOVER (EX. SMALLER HANDOVER HYSTERIS AND SHORTER FITER LENGTHS ) CAN TAKE CARE OF LOCAL INTERFERENCE PROBLEMS.
ANTENNA ADJUSTMENTS:
ANTENNA ADJUSTMENTS SUCH AS ANTENNA TILT AND HEIGHT AFFECTS THE SIGNAL STRENGTH AND THEREBY THE CELLS BOARDERS AND
INTERFERENCE LEVELS .
BY DOENTILTING THE ANTENNAS ,A CALMER BEHAVIOR IS GENERALLY ACHIEVED IN THE NETWORK .THE SIGANL STRENGTH BECOMES MORE CONCENTRATED TO THE AREA CLOSE TO THE SITE .DOWNTILTING AN ANTENNA CAN REDUCE IN INTERFERENCE IN CO- CHANNEL OR ADJUSTENT
CHANNEL CELLS AS WELL AS IN THECELL ITSELF.
THE MAJOR DRAWBACK OF HAVING TOO MUCH DOWNTILT IS THE RISK OF A LOSS IN OVERALL COVERAGE.
