gsm session sabal may 2016.pptx

8/17/2019 GSM session SABAL May 2016.pptx

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GSM introduction/ Concepts

and technical views

5/7/16 Prepared by Eltayeb & Mohaed !hed 1


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GSM "E#$%' C%MP%"E"#S

5/7/16 Prepared by Eltayeb & Mohaed !hed Pa(e)

Another MSC

HLR/AUC

OMC

MS

Um

MS

A-bis

BSC

A

BTS

MSC/VLR


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#*

5/7/16 Prepared by Eltayeb & Mohaed !hed +

TRX A transmission/reception facility is called as a transceiver (TRX).

Typically, a cell has several TRXs, and one frequency is allocated to each

TRX. The capacity of a cell can therefore be measured in the number of TRXs.

A time slot that carries user traffic is also called as Traffic Channel (TC).!or administrative purposes, e.". providin" mobile terminals #ith control

information, there is also one $CC in each cell.

e%ample&

if one sector has ' TRXs, (time slots ) for *CC are confi"ured for it, and#e have for *ata ' T, so #e #ill have +'--' Time slot reserved for

speech, #hich can support theorically in best conditions 0 users

simultanously if #ith 1223 alf Rate.


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#* power

5/7/16 Prepared by Eltayeb & Mohaed !hed ,

$oard Type 4umber of TRXs 5utput 6o#er

7R!8919' ' 2

7R!89190 0 1

7R!8919 1

7RR8919' ' 2

7RR89190 0 1:

;RR8919' ' 2

;RR89190 0 1


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-re.uency oppin(

0/ ;ohammed Ahmed 0

!requency oppin" is mechanism in #hich the system chan"es the frequency

(uplin? and do#nlin?) durin" transmission at re"ular intervals

Types of !requency oppin" &

$ase $and !requency oppin" ($$)

ynthesi@er !requency oppin" (!)

Advanta"es of oppin" &

6rovide a similar communication quality for every user. hoppin" ma?es cell plannin" more fle%ible


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oppin( Paraeters


;A (;obile Allocation et)&

;A is the set of available R! bands #hen hoppin", containin" at most

' frequency carriers. The frequency bein" used must be those of the

available frequency

;A5 (;obile Allocation nde% 5ffset)

;A5 is used to define the initial frequency of the hoppin".

$e careful to confi"ure the ;A5 of same timeslot in all channels,

other#ise interference occurs.

4： oppin" equence 4umber （ 2～ :）

42： cycle hoppin".4B2： random hoppin". =very sequence number corresponds a

pseudo random sequence.


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adio !ccess #echnolo(y iin( !dvance 0#!

5/7/16 Prepared by Eltayeb & Mohaed !hed Pa(e7

F r e q u e

n c y

T i m e

U s e r

U s e r

U s e r

U s e r

U s e r

U s e r

U s e r

U s e r

TimeFDMA

Frequency

The mobie !hone shou"

sen" the si#n$ in $"%$nce&&

Tr$nsmission "e$y t

2 obile station oves away 3ro the base station durin( a call

2 43 the delay is too hi(h the tieslots o3 the si(nal 3ro a certain obile station and that o3the net si(nal 3ro another obile station received by the base station will overlap eachother


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#*

• #*8 iscontinuous #ransission

• Shut o9 the transission at voice intervals:

• %nly transit S4 3raes;

• #he transcoder at the * terinal producesco3ortable noise<

• =!8 =oice !ctivity etection

• 4pleented by the transcoder<

5/7/16 Prepared by Eltayeb & Mohaed !hed Pa(e>

Save battery life and

reduce interference

Actually, durin" the communication process, the mobile subscriber tal?s only '23 of the time

and there is not much useful information transmitted durin" rest of the time. f all the

information is transmitted to the net#or?, it #ill not only be a #aste of the system resources but also add more interference to the system. n order to overcome this problem, the *TX

technique is used in the 7; system

* & ilence *escriptor


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rol

•ave the battery life

•Reduce net#or? interference

•nclude both uplin? po#er control and

do#nlin? po#er control

•evel and quality are ta?en into account

5/7/16 Prepared by Eltayeb & Mohaed !hed Pa(e?


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Channels8 @o(ical Channel #ype

• GSM?AA and CS1>AA have the sae lo(ical channelcate(ory

5/7/16 Prepared by Eltayeb & Mohaed !hed Pa(e1A

Bro$"c$st contro ch$nne

'BCH(Contro ch$nneCommon contro ch$nne

'CCCH(

Voice ch$nne

'TCH(

FCCH SCH BCCH TCH/FA)CH RACH SDCCH FACCH

SACCH

TCH/H*CH

Common ch$nne

'CCH(

De"ic$te" ch$nne

'DCH(

Lo#ic$ ch$nne

'system in+orm$tion(


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System GSM 900 GSM 1800

Dplin ownlin >?A2?15 MF?+52?6A MF 171A217>5 MF1>A521>>A MF

$avelen(th ++ c 17 c

Bandwidth )5 MF 75 MF

uple istance ,5 MF ?5 MF

adio Channels 1)5 175

#ransission ate )7A bits/s )7A bits/s


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•

Cell selection/reselection processes areper3ored in idle ode<

• #he MS uses the cell selection al(orith toloo 3or a cell 0o3 the chosen P@M" where

it can cap on<• 43 the MS looses covera(e o3 that cell : it

will loo 3or the ost suitable alternativeand it will cap on that cellH cell

reselection<• urin( 4dle Mode the "etwor doesn;t

now the cell which the MS is capin( onit only nows the @ocation !rea where theobile re(istered hisel3 in<

Cell selection & reselection wheredo 4 cap onI

1)


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e.uireents 3or GSM handover The process of handover or handoff #ithin any cellular system is of "reat

importance. t is a critical process and if performed incorrectly handover can

result in the loss of the call. *ropped calls are particularly annoyin" to users

and if the number of dropped calls rises, customer dissatisfaction increases

and they are li?ely to chan"e to another net#or?. Accordin"ly 7;

handover #as an area to #hich particular attention #as paid #hen

developin" the standard.

andover

1+


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andover cont<

1,

Types of 7; handover Dithin the 7; system there are four types of handover that can be performed for

7; only systems&

ntra-$T handover& This form of 7; handover occurs if it is required to

chan"e the frequency or slot bein" used by a mobile because of interference, or

other reasons. n this form of 7; handover, the mobile remains attached to the

same base station transceiver, but chan"es the channel or slot.

nter-$T ntra $C handover& This for of 7; handover or 7; handoffoccurs #hen the mobile moves out of the covera"e area of one $T but into

another controlled by the same $C. n this instance the $C is able to perform

the handover and it assi"ns a ne# channel and slot to the mobile, before

releasin" the old $T from communicatin" #ith the mobile. nter-$C handover& Dhen the mobile moves out of the ran"e of cells

controlled by one $C, a more involved form of handover has to be performed,

handin" over not only from one $T to another but one $C to another. !or this

the handover is controlled by the ;C. nter-;C handover& This form of handover occurs #hen chan"in" bet#een

net#or?s. The t#o ;Cs involved ne"otiate to control the handover <


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Case !nalysis


;issin" relations appearance

Case !nal sis


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;issin" relations occurred&-

!a?e overshootin" case , you may #onder #hy this cell isservin" in the areaEF

- Too many reasons could lead to such a case

Availability issues on near by cells, Cross sector on the cell should

be coverin" #hich may lead to call be served by the #ron"

nei"hbors to the crossed sectorGGetc

- $Cs $order areas andover issues.

Case !nalysiscont<



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Case !nalysis 8 overshootin(



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Case !nalysis cont<

5/7/16 Prepared by Eltayeb & Mohaed !hed 1>

5vershootin" cases

- 5vershootin" effects&

Appearance of missin" relations nterference8n #anted traffic increase #hich may lead to con"estion

issuesGGetc- *o#n tilt / 8p tilt solutions


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Case !nalysis8 inter3erence

5/7/16 Prepared by Eltayeb & Mohaed !hed 1?


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Case !nalysis cont<

5/7/16 Prepared by Eltayeb & Mohaed !hed )A

nterference Case

- nterference effects&Appearance of bad quality spots

*ropped callsandover failures- olutions&- ;A list #ap or plit (depends on the operatorHs actual

!requency plan).

- 6hysical actions& *o#n tilt/ 8p tilt dependin" on actual TA;easurements (traffic distribution/failures) of the interfered

cells. o it is important to stren"then the carrier and decrease

po#er of the interferer by do#n-tilt


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Case analysis8accessibility

5/7/16 Prepared by Eltayeb & Mohaed !hed )1


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Case !nalysis cont<

5/7/16 Prepared by Eltayeb & Mohaed !hed ))

• Althou"h radio conditions are "ood in "eneral and #e can see

very "ood levels of the nei"hbor cells but servin" cell is an1+22 band cell instead, #ith an accepted but not "ood levels

inside.

• There are bad level samples because of the handover priority

issue bet#een band 1+22 and I22.

• Recommended is to ma?e J4-Alhalfaya-2'-7-0I0-: (I22

band) serves because it has very "ood radio conditions.

•uch a radio condition can affect the accessibility sometimes,

because the ; is served at the ed"e of the cell.

• De can solve it by different solutions , either tilts or modifyin"

the andover parameters

C ! l i t


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• uch a radio condition can affect the accessibility sometimes,

because the ; is served at the ed"e of the cell.

• De can solve it by different solutions , either tilts or modifyin"

the andover =*7= parameters ta?in" into consideration the

actual po#er control and andover al"orithms used K #hich is

vendor specific.

Case !nalysis cont<

5/7/16 Prepared by Eltayeb & Mohaed !hed )+

i i


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Cell reselection to +G 3ailures

!ny su((estionsIJJJ

andovers 3ro +G 3ailures

Probles and solutionsIJ

! very iportant point is to have your +G/)G

in3oration lined in to(ether in order to

understand the interoperability between such

technolo(iesKKeselection andover

redirectionK


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Sabal %ptiiFation #eaThan? you

gsm session sabal may 2016.pptx

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