Evolucija GSM sistema (GPRS & EDGE) - Telfor

Elektrotehnicki fakultet
Univerzitet u Beogradu
Evolucija GSM sistema
(GPRS & EDGE)
Prof. dr Ðorde Paunovic
Doc. dr Aleksandar Neškovic
Dr. Nataša Neškovic

Javni mobilni radio sistemi
- pregled stanja u svetu -
Konvergencija govornog saobracaja ka mobilnim radio-sistemima

Javni mobilni radio sistemi
- pregled stanja u svetu -
Procenat korisnika [%]
Razvoj javnih mobilnih radio-sistema do 2007. god. (predvidanje)

Javni mobilni radio sistemi
- pregled stanja u svetu -
Teritorijalna raspodela razlicitih tipova javnih mobilnih sistema
v Osnovne

Evolucija GSM standarda
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).

Arhitektura GSM mreže
PSTN / ISDN
MSC
•
•
•
•
•
•
•
•
•
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MSC
BSS BSS
BSS BSS
•
•
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Second Generation Mobile Network Architecture

Tehnicko-tehnološka koncepcija
GSM sistema
AUC
other VLRs
U m
Base Station Subsystem (BSS)
BTS
A-bis
BSC
BTS
BTS
MS
other BSSs
A
H G
D
EIR HLR VLR OMC
F
C
B
Mobile
Services
Switching
Centre
(MSC)
other MSCs
E
PSTN
ISDN
CSPDN
PSPDN
Osnovna arhitektura
GSM sistema
BTS: Base Transceiver Station
BSC: Base Station Controller
HLR: Home Location Register
VLR: Visited Location Register
OMC: Operation & Maintenance Centre
EIR: Equipment Identity Register
AUC: Authentication Centre

GSM sistema
- frekvencijski opsezi -
v Osnovni GSM 2G
standard

v Osnovni GSM 2G
standard
GSM sistema
- osnovne specifikacije -

Frekvencijski opsezi i radio-kanali
- 900 MHz -
Uplink 890 – 915 MHz 25 MHz
Downlink 935 – 960 MHz 25 MHz
1 2 3 4 ……………. 124
100 KHz 200 KHz 100 KHz
A 200 KHz carrier spacing has been chosen. Excluding 2x100 KHz edges of
the band, this gives 124 possible carriers for the uplink and downlink. The
use of carrier 1 and 124 are optional for operators.
Multiple Access Technique
FDMA/TDMA. The total band is divided into 124x200 KHz bands (FDMA).
Each group of 8 users transmit through a 200 KHz band sharing
transmission time (TDMA).

GSM sistem
- radio interfejs (FDMA/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 the
Mobile station.

Traffic Channels
Traffic 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)
Speech Channels
Speech channels are defined for both full rate and half rate
traffic channels. The latter for the future system.
Data Channels
Logical Channel Types
Data channels support a variety of data rates (2.4, 4.8 and
9.6 Kb/s) on both half and full rate traffic channels. The 9.6
Kb/s data rate is only defined for full rate application.

Logical Control Channels
Downlink
Broadcast Control Channels
• Frequency Correction - FCCH
• Synchronization – SCH
• Broadcast - BCCH
Common Control Channels
• Access Grant - AGCH
• Paging - PCH
Uplink
-
Common Control Channels
• Random Access - RACH
Dedicated Control Channels
• Stand – alone Dedicated - SDCCH
• Slow Associated – SACCH
• Fast Associated - FACCH

Power control
• 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-channel
interference
• The MS will be capable of varying its transmit power form its
maximum 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

GSM mandatory features - 1
1. Discontinuous transmission and reception (with the aid of
Voice activity detector)
Advantages:
• The level of co-channel interference is, on average, reduced
By about 3 dB
• For a hand-held portable unit, the battery life can be significantly
extended

GSM mandatory features - 2
2. Slow frequency hopping
Advantages:
1. The receive TDMA bursts with high error rates will be more
spread in time
2. The co-channel interference is more evenly spread between
all the MSs

GSM servisi
v Više desetina postojecih servisa i stalni razvoj novih servisa.
v Teleservisi
- pre-paid telefonija,
- post-paid telefonija,
- fax,
- SMS, ...
v Bearer servisi
- više tipova prenosa
podataka do 9600bps,
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), i
TELEKOM – 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%.

Javni mobilni
radio sistemi
- pregled stanja u
Srbiji -
Izvor podataka GSM MoU:
http://www.gsmworld.com
Novembar 2003

GPRS (General Packet Radio Services)
• 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).
• Oko 190 GSM operatora u svetu investiralo je u GPRS.
• TELEKOM i MOBTEL GPRS servis zapoceli su tokom 2003.god.

Novi dopunski GPRS servisi
(mobile Internet technology)
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.
v Messaging 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 wellknown
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 video
conferencing.
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.

Prenos podataka – tipovi i karakteristike
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 a
response of the request (e.g., WEB/WAP browser).

Zahtevi u pogledu kvaliteta servisa (QoS)
Novembar 2003

Definicija klasa saobracaja

End User Performance Expectations-
Conversational/Real-Time Services
Novembar 2003

End User Performance Expectations-
Streaming Services
Novembar 2003

End User Performance Expectations-
Interactive Services
Novembar 2003

Uvodenje GPRS-a u postojecu GSM mrežu
•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.
SGSN - Serving GPRS Support Nodes Novembar 2003
GGSN - Gateway GPRS Support Node

GPRS - arhitektira
Novembar 2003

Klase mobilnih GPRS uredaja
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 GPRS
communication 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.

EDGE (Enhanced Data for GSM Evolution)
• 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

EDGE (Enhanced Data for GSM Evolution)
Izmena nacina modulacije na radio-interfejsu – povecanje protoka!
Novembar 2003
Uporedni prikaz GMSK i 8PSK modulacija.