slide 8 gsm overview

7/31/2019 Slide 8 GSM Overview

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Slide 8

Global System for MobileCommunication

(GSM)


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GSM Architecture


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Base Station Subsystem(BSS)

BSS terdiri dari dua buah perangkat :

Base Transceiver Station (BTS)

BTS merupakan tranceiver yang mendefinisikan sebuahsel dan menangani hubungan link radio dengan MS.

BTS terdiri dari perangkat pemancar dan penerima,seperti antenna dan pemroses sinyal untuk sebuahinterface.

Base Station Controller (BSC) BSC mengatur sumber radio untuk sebuah BTS atau lebih.

BSC menangani radio-channel setup, frequency hopping,and handover intern BSC.


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Network Sub-system (NSS)

NSS terdiri dari : Mobile Switching Center (MSC).

Home Location Register (HLR). Visitor Location Register (VLR).

Authentication Center (AuC).

Equipment Identity Register (EIR).


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Mobile Switching Center (MSC)

Melakukan fungsi switching dasar

Sebagai penghubung antara satu jaringan GSMdengan jaringan lainnya melalui InternetworkingFunction (IWF)


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Authentication Center (AuC)

Berisi parameter authentikasi pelanggan untukmengakses jaringan GSM.

AuC mekanisme authentication.


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Home Location Register (HLR)

HLR berisi rekaman database permanen daripelanggandan merupakan database user yang

utama. HLR juga berisi rekaman lengkap lokasi terkini

dari user.


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Visitor Location Register (VLR)

VLR berisi database smentara dari pelanggan, digunakanuntuk pelanggan lokal dan yang sedang melakukanroaming.

VLR memiliki pertukaran data yang luas daripada HLR dandiakses oleh MSC untuk setiap panggilan, dan MSCdihubungkan dengan VLR.

Setiap MSC terhubung dengan sebuah VLR, tetapi satu VLR

dapat terhubung dengan beberapa MSC.


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Equipment Identity Register

(EIR)

EIR merupakan register penyimpan data seluruhmobile stations

EIR berisi IMEIs (international Mobile EquipmentIdentities), yang merupakan nomor seri perangkat +tipe code tertentu.


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Operation Sub-system (OSS)

Operation and Maintenance Jaringan.

Pengaturan pelanggan dan tagihan.

Pengaturan Mobile Equipment.


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Kanal Pada GSM (1)

Struktur kanal pada GSM, terbagi menjadi dua, yaitu kanalfisik dan kanal logik.

Kanal fisik berhubungan dengan kanal frekuensi radio dan

time slot, sedangkan kanal logik berhubungan denganinformasi dan kontrol data pensinyalan.

Seperti yang telah dibahas pada pertemuan sebelumnya,bahwa teknik multiplexing GSM menggunakan TDMA &FDMA.


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Kanal Pada GSM (2)

FDMA membagi kanal menjadi 125 kanal, dimana 124 kanalmerupakan kanal komunikasi, dan 1 kanal untuk keperluanpensinyalan.

Tiap kanal pada GSM memiliki lebar 200kHz, dimana setiapkanal dibagi lagi menjadi 8 time slot, dengan setiap slotmemiliki durasi 576,9 s.

Sehingga 8 slot memiliki durasi 4,615 ms.


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MS (Mobile Station) States (1)

The mobile station does not answer paging messages,therefore there is no contact between the MS and thenetwork. The network does not get any information on where

the MS is. This state is considered as MS detached. When the MS is turned on or MS attached it can be in two

states : MS Idle & MS Active.


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~ MS Idle

While moving around - roaming - the mobile station listens tothe best cell for paging messages.

The MS decides by itself which cell is the best one. This isdone by comparing own cell to neighboring cells.

If a neighboring cell is considered better, the MS will changecells and, if necessary, inform the system about the newLocation Area (LA).

This is called location updating. In idle state the MS can

receive short messages or cell broadcast messages.


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~ MS Active

MS is considered active (or busy) when there is a call (speech,fax or data), or a call set up procedure, going on.

In this state the MS does not decide by itself if it is necessary

to change cell. Based on measurements provided by the MS and the BTS, the

BSC makes the decision on change of cell. The decisionmaking is considered as locating, while the actual change ofcells is considered as handover.

In active state the MS can at the same time receive shortmessages, but not cell broadcast messages.

H d B C ll C ll d b


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Handover Between Cell, Controlled by

The Same BSC

1. BSC orders to the new BTS to activate a

TCH (Traffic Channel).

2. BSC sends a message to the MS via theold BTS containing information about the

frequency and time slot to change to,and also what output power to use. This

information is sent over FACCH (FastAssociated Control Channel).

3. MS tunes to the new frequency, andtransmits Handover (HO) access bursts in

the correct time slot.4. When the new BTS detects the HO bursts

it sends information about timingadvance. This is sent on FACCH.

5. MS sends a Handover Complete messageto BSC via new BTS.

6. BSC tells the old BTS to release the oldTCH.

H d B t C ll Th Diff t


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Handover Between Cell : The Different

BSC, Same MSC/VLR (1)

1. The serving (old) BSC sends a Handoverrequired message to the MSC together withthe identity of the target cell.

2. MSC knows which BSC that controls this BTSand sends a Handover request to this BSC.

3. New BSC orders target BTS to activate a TCH.

4. New BSC sends a message to the MS via MSC,old BSC and old BTS containing informationabout the frequency and time slot to changeto, and what output power to use. Thisinformation is sent over FACCH (FastAssociated Control Channel).

5. MS tunes to the new frequency, and transmitsHandover (HO) access bursts in the correcttime slot.

6. When the new BTS detects the HO bursts itsends information about timing advance. Thisis sent on FACCH.

7. MS sends Handover Complete message toMSC via new BSC.

8. The MSC sends an order to old BSCpreviously to release the old TCH.

9. The old BSC tells the old BTS to release thepreviously used TCH.


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Handover Between Cell : The Different

MSC/VLR (1)

1. The serving (old) BSC sends a Handoverrequired message to the serving MSC, MSCA,together with the identity of the target cell.

2. MSCA realizes that this cell belongs to anotherMSC, MSCB, and asks for help.

3. MSCB allocates a handover number in order toreroute the call. A Handover request is thensent to the new BSC.

4. New BSC orders target BTS to activate a TCH.

5. MSCB receives the information, and passes iton to MSCA together with the handovernumber.

6. A link is set up to MSCB, possibly via PSTN.7. MSCA sends a HO command to MS, via old BSC

containing information on which frequency andtime slot to use, and what output power to use.This information is sent over FACCH (FastAssociated Control Channel).

8. MS tunes to the new frequency, and transmits

Handover (HO) access bursts in the correct timeslot. The HO bursts are transmitted on FACCH.

9. When the new BTS detects the HO bursts itsends information about timing advance.This is sent on FACCH.

10. MS sends Handover Complete message toold MSC via new BSC and new MSC/VLR.

11. A new path in the group switch in MSCA is

established, and the call is switchedthrough.

slide 8 gsm overview

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