evolucija gsm sistema (gprs & edge) - · pdf fileevolucija gsm sistema (gprs & edge)...

Elektrotehnicki fakultetUniverzitet u Beogradu

Evolucija GSM sistema (GPRS & EDGE)

Prof. dr Ðorde PaunovicDoc. dr Aleksandar Neškovic

Dr. Nataša Neškovic

Javni mobilni radio sistemi - pregled stanja u svetu -

Konvergencija govornog saobracaja ka mobilnim radio-sistemima

Razvoj javnih mobilnih radio-sistema do 2007. god. (predvidanje)

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Teritorijalna raspodela razlicitih tipova javnih mobilnih sistema

v Osnovni GSM 2G standard

v GPRS (General Packet Radio Services) – 2.5G,

v EDGE (Enhanced Data for GSM Evolution) - 2.5G, i

v 3GSM (tehnologija 3G mobilnih sistema primenjena na evoluiranoj GSM strukturi).

Evolucija GSM standarda

Arhitektura GSM mreže

Second Generation Mobile Network Architecture

PSTN / ISDN

• • • • • • • • • •MSC MSC

BSSBSS BSS BSS• • • • • •

Tehnicko-tehnološka koncepcija GSM sistema

BTS

MS

Um

BTS

BTSBSC

Base Station Subsystem (BSS)

A-bisA

Osnovna arhitektura GSM sistema

BTS: Base Transceiver StationBSC: Base Station ControllerHLR: Home Location RegisterVLR: Visited Location RegisterOMC: Operation & Maintenance CentreEIR: Equipment Identity RegisterAUC: Authentication Centre

MobileServicesSwitchingCentre(MSC)

HLREIR VLR OMC

AUC

F

H G

BC

other MSCs

E

PSTNISDNCSPDN PSPDN

other VLRs

other BSSs

D


GSM sistema- frekvencijski opsezi -


GSM sistema- osnovne specifikacije -

Frekvencijski opsezi i radio-kanali- 900 MHz -

Uplink 890 – 915 MHz 25 MHz

Downlink 935 – 960 MHz 25 MHz

100 KHz 200 KHz 100 KHz

1 43 1242 …………….

A 200 KHz carrier spacing has been chosen. Excluding 2x100 KHz edges ofthe band, this gives 124 possible carriers for the uplink and downlink. The use of carrier 1 and 124 are optional for operators.

Multiple Access TechniqueFDMA/TDMA. The total band is divided into 124x200 KHz bands (FDMA).Each group of 8 users transmit through a 200 KHz band sharingtransmission time (TDMA).

GSM sistem- radio interfejs (FDMA/TDMA) -

Radio interfejs (TDMA)- problem vremenskog kašnjenja -

Radio interfejs (TDMA)- timing advance -

Blok dijagram GSM radio-sistema

GSM sistem

GMSK(Gaussian Minimum

Shift Keying)modulacija

Channel Types

1. Traffic channels (TCHs)

The traffic channels are intended to carry encoded speech or user data.

2. Control Channels (CCHs)

The control channels are intended to carry signalling and synchronization data between the base station and theMobile station.

Traffic ChannelsTraffic channels are intended to carry encoded speech and user data.• Full rate traffic channels at a net bit rate of 22.8 Kb/s (TCH/F)• Half rate traffic channels at a net bit rate of 11.4 Kb/s (TCH/H)

Data Channels

Speech ChannelsSpeech channels are defined for both full rate and half ratetraffic channels. The latter for the future system.

Data channels support a variety of data rates (2.4, 4.8 and9.6 Kb/s) on both half and full rate traffic channels. The 9.6Kb/s data rate is only defined for full rate application.

Logical Channel Types

Logical Control Channels

Downlink UplinkBroadcast Control Channels• Frequency Correction - FCCH• Synchronization – SCH• Broadcast - BCCH

-

Common Control Channels• Access Grant - AGCH• Paging - PCH

Common Control Channels• Random Access - RACH

Dedicated Control Channels• Stand – alone Dedicated - SDCCH• Slow Associated – SACCH• Fast Associated - FACCH

• RF power control will be used in the GSM MS and BS to reduce the transmit power to the minimum required to achieve the minimum quality objective and hence reduce the level of co-channelinterference

• The MS will be capable of varying its transmit power form itsmaximum output down to 20 mW in steps of nominally 2 dB

• The BS calculates the RF Power level to be used by the MS and sends a 4 bit number instruction to the corresponding MS

Power control

1. Discontinuous transmission and reception (with the aid ofVoice activity detector)

• The level of co-channel interference is, on average, reducedBy about 3 dB

• For a hand-held portable unit, the battery life can be significantlyextended

Advantages:

GSM mandatory features - 1

2. Slow frequency hopping

1. The receive TDMA bursts with high error rates will be more spread in time

2. The co-channel interference is more evenly spread betweenall the MSs

Advantages:

GSM mandatory features - 2

v Teleservisi- pre-paid telefonija,- post-paid telefonija, - fax, - SMS, ...

v Bearer servisi- više tipova prenosa

podataka do 9600bps, ...

GSM servisi

v Više desetina postojecih servisa i stalni razvoj novih servisa.

v Dodatni servisi- razne kontrole poziva, - konferencijska veza, - govorna pošta, - faks-pošta, - medunarodni roaming, - virtualne privatne mreže (VPN)- Direktna veza PABX ↔ MSC, ...

Javni mobilni radio sistemi - pregled stanja u Srbiji -

v Dva GSM operatora u opsezima GSM900 i GSM1800:MOBTEL – 063 (od 1996.god), iTELEKOM – 064 (od 1998.god).

v Teritorijalna pokrivenost GSM servisom oko 75-80% teritorije i oko 87% stanovništva.

v TELEKOM I MOBTEL imaju oko 2 miliona korisnika, svaki.v Ambiciozni planovi razvoja u narednim godinama.v Do kraja 2005.god treba ocekivati

- pokrivenost teritorije od oko 80-85%,- pokrivenost stanovništva do 95%.

Izvor podataka GSM MoU: http://www.gsmworld.com

Novembar 2003

Javni mobilni radio sistemi

- pregled stanja u Srbiji -

• GPRS omogucava vece protoke podataka u okviru postojecih GSM mreža!• GPRS se oznacava kao 2.5G tehnologija.

• Princip udruživanja vremenskih slotova u okviru jednog radio-nosioca.

• Kroz GPRS uvodi se paketski prenos podataka na radio-ineterfejsu.• Teorijski, maksimalan protok iznosi 160kbs (za korisnika 115kbs).• U praksi raspoloživi protoci znatno manji (tipicno 40-50kbps). • Brza uspostava veze (ne uspostavlja tzv. dial-up veza).

GPRS (General Packet Radio Services)

• Oko 190 GSM operatora u svetu investiralo je u GPRS. • TELEKOM i MOBTEL GPRS servis zapoceli su tokom 2003.god.

v Client-server services, which enable access to data stored in databases. The most famous example of this is access to the World Wide Web (WWW) through a browser.

vMessaging services, intended for user-to-user communication between individual users via storage servers for message handling. Multimedia Messaging Service (MMS) is an example of a well-known messaging application.

v Real-time conversational services, which provide bidirectional communication in real-time. A number of Internet and multimedia applications require this scheme such as voice over IP and videoconferencing.

v Tele-action services, which are characterized by short transactions and are required for services such as SMS, electronic monitoring, surveillance systems, and lottery transactions.

Novi dopunski GPRS servisi(mobile Internet technology)

v Infrequent data transmission, as when the time between two transmissions exceeds the average transfer delay (e.g., messaging services);

v Frequent transmission of small data blocks, in processes of several transactions of less than 500 octets per minute (e.g., downloading of several HTML pages from a browsing application);

v Infrequent transmission of larger data blocks, in processes of several transactions per hour (e.g., access of information stored in database centers);

v Asymmetrical throughput between uplink and downlink, such as for data retrieval in a server where the uplink is used to send signaling commands and the downlink is used to receive data as aresponse of the request (e.g., WEB/WAP browser).

Prenos podataka – tipovi i karakteristike

Novembar 2003

Zahtevi u pogledu kvaliteta servisa (QoS)

Definicija klasa saobracaja

Novembar 2003

End User Performance Expectations-Conversational/Real-Time Services

Novembar 2003

End User Performance Expectations-Streaming Services

Novembar 2003

End User Performance Expectations-Interactive Services

•Relativno jednostavna i elegantna instalacija•Koristiti ista postojeca celijska struktura. •Radio-pokrivanje je približno isto kao i za govorne servise.•Nije neophodno novo frekvencijsko planiranje.•Zahtevaju se izmene samo u upravljacko-komutacionim cvorištima.

Novembar 2003

Uvodenje GPRS-a u postojecu GSM mrežu

SGSN - Serving GPRS Support NodesGGSN - Gateway GPRS Support Node

Novembar 2003

GPRS - arhitektira

v The class A mobile can support simultaneously a communication in circuit-switched mode and another one in packet-switched mode. It is also capable of detecting in idle mode an incoming call in circuit or packet-switched mode.

v The class B mobile can detect an incoming call in circuit-switched mode or in packet-switched mode during the idle mode but cannot support them simultaneously. The circuit and packet calls are performed sequentially. In some configurations desired by the user, a GPRScommunication may be suspended in order to perform a communication in circuit-switched mode and then may be resumed after the communication release in circuit-switched mode.

v The class C mobile supports either a communication in circuit-switched mode or in packet-switched mode but is not capable of simultaneously supporting communications in both modes. It is not capable of simultaneously detecting the incoming calls in circuit-switched and packet-switched mode during idle mode. Thus a class C mobile is configured either in circuit-switched mode or in packet-switched mode. The mode configuration is selected either manually by the user or automatically by an application.

Klase mobilnih GPRS uredaja

• Promena na osnovnom fizickom nivou radio-interfejsa.

• Povecanje protoka iznosi oko tri puta u odnosu na GPRS protoke.

• Struktura i nacini realizacije servisa prakticno se ne menjaju.

• Novi tip modulacije i novi tip kanalskog kodovanja na radio-interfejsu.

• Striktno se poštuju TDMA struktura rama, širina radio-kanala (200kHz).struktura logickih kanala, kao i sistemski GPRS mehanizmi.

•Maksimalni protok podataka za korisnika 384kbs (GPRS - 115kbs).

•Teorijski protok na fizickom nivou 473.6kbs (GPRS – 160kbs). Novembar 2003

EDGE (Enhanced Data for GSM Evolution)

• EDGE u pogledu komutaciono-upravljackog sistema, u potpunosti koristi strukturu definisanu u okviru GPRS-a.

• Zahteva se zamena primo-predajnih jedinica u okviru baznih stanica.

• Nedostatak, zahteva se veci odnos C/I nego u slucaju GPRS-a.

• Neminovno uvodenje novih baznih stanica u radio-mrežu.

• Ocekuje se pun razvoj multimedijalnih servisa, brzi pristup Internetu, prenos pokretnih slika, itd.

Novembar 2003


Izmena nacina modulacije na radio-interfejsu – povecanje protoka!

Novembar 2003Uporedni prikaz GMSK i 8PSK modulacija.


evolucija gsm sistema (gprs & edge) - · pdf fileevolucija gsm sistema (gprs & edge)...

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