GSM Power Point

MOBILE COMMUNICATIONS

Alexandre ELAGUINE & Mikhail BAIAKOVSKI

31.01.2002

MOBILE COMMUNICATIONS

• Basic principles• Early analog networks• Digital networks, GSM• GPRS and EDGE• UMTS• Future networks

Wireless versus Mobile

BASIC NETWORK STRUCTURE

Propagation Mechanisms

• Reflection

• Diffraction (Shadowing)

• Scattering

• Doppler effects

• Fading

FREQUENCY REUSE

3/9 CELL PATTERN

BASIC NETWORK STRUCTURE

SYSTEM STRUCTURE

ANALOGUE MOBILE NETWORKS

NMT 450 NMT 900 AMPS TACS

Start 1981 1986 1984 1985MHz Up 453 - 457.5 890-915 824-849 890-915MHz Down 463-467.5 935-960 869-894 935-960No. of channels 180 1000 832 1000

DIGITAL MOBILE NETWORKS

GSM D-AMPS PDCStart 1992 1991 1993MHz Up 890-915 824-849 ~900 ~1400MHz Down 935-960 869-894 ~800 ~1400Multiplex TDMA TDMA TDMA

SIM: SUBSCRIBER IDENTITY MODULE

GSM frequency bands

• 900 MHz– 2*25 MHz Bands

– 45 MHz Duplex Spacing

– 125 carriers

• 1800 MHz– 2*75 MHz Bands

– 95 MHz Duplex Spacing

– 375 carriers

• 1900 MHz– 2*60 MHz Bands

– 80 MHz Duplex Spacing

– 300 Carriers

• 890-915 MHz Uplink

• 935-960 MHz Downlink

• 1710-1785 MHz Uplink

• 1805-1880 MHz Downlink

• 1850-1910 MHz Uplink

• 1930-1990 MHz Downlink

GSM: AREAS

THREE ACCESS METHODS IN CELLULAR SYSTEMS

• FDMA Frequency Division Multiple Access

• TDMA Time Division Multiple Access

• CDMA Code Division Multiple Access

TDMA: FRAME

D-AMPS

• The EIA/TIA (TDMA) standard has many names– TDMA (the most common)– US Digital Cellular (USDC)– North American TDMA (NA-TDMA)– Digital AMPS (D-AMPS)– IS-54 and IS-136

CDMA

• Every mobile in the network has a unique code, the chip sequence

• When a mobile sends a bit stream, each bit is replaced by the chip code

• A « one » in the bit stream is replaced by the chip code

• A « zero » in the bit code is replaced by the compliment of the chip code

• If the chip code is n bits long, each bit in the original bit stream is replaced by n bits

• Instead of some 10kbps in the original bit stream, Mbps is sent

• This is often referred as to « spread spectrum techniques »

GPRS, GENERAL PACKET RADIO SERVICE (1)

• Genera! Packet Radio Service (GPRS) is a new service designed for digital cellular networks (GSM, DCS, PCS).

• GPRS uses a packet-mode technique to transfer high-speed and tow-speed data and signalling in an efficient manner over GSM radio networks.

• GPRS can be used for carrying end user's packet data protocol such as IP andX.25

• GPRS is standardised in ETSI (European Telecommunications StandardsInstitute).

• New GPRS radio channels are defined, and the allocation of these channels is flexible: from 1 to 8 radio interface timeslots can be allocated per TDMA frame, timeslots are shared by the active users, and up and downlink are allocated separately.

• Various radio channel coding schemes are specified to allow bitrates from 9 to more than 150 kbit/s per user.

GPRS, GENERAL PACKET RADIO SERVICE (2)

• GPRS introduces two new network nodes in the GSM PLMN: The Serving GPRS Support Node (SGSN), which is at the same hierarchical level as the MSC, keeps track of the individual MSs' location and performs security functions and access control. The SGSN is connected to the base station system with Frame Relay. The Gateway GSN (GGSN) provides interworking with external packet-switched networks, and is connected with SGSNs via an IP-based GPRS backbone network. The HLR is enhanced with GPRS subscriber information, and the SMS-MSCs are upgraded to support SMS transmission via the SGSN. Optionally, the MSC/VLR can be enhanced for more-efficient co-ordination of GPRS and non-GPRS services and functionality: e.g., paging for circuit-switched calls which can be performed more efficiently via the SGSN, and combined GPRS and non-GPRS location updates.

EDGEEnhanced Data rates for GSM Evolution

• ECSD - Enhanced CSD (Circuit Switched Data)• EGPRS - Enhanced GPRS• For higher data rates• New coding and modulation schemes• The base stations need to be up dated• EGPRS up to 384 kbps (48 kbps per time slot)• ECSD 28.8 kbps

IMT-2000

• FPLMTS: Future Public Land Mobile Telecommunications System

• IMT 2000: International Mobile Telecommunications

• UMTS: Universal Mobile Telecommunications System

• UMTS: Specificed by ETSI, CEPT and UMTS forum

• UMTS: Specificed by ETSI, CEPT and UMTS forum

IMT-2000

• The main characteristic of 3G Systems, known collectively as IMT-2000, are a single family of compatible standards that have the following characteristics

• Used worldwide

• Used for all mobile applications

• Support both packet-switched and circuit-switched data transmission

• Offer high data rates up to 2Mbps (depending on mobility/velocity)

• Offer high spectrum efficiency

IMT-2000• IMT-2000 stands for

– IMT: International Mobile Communications2000: the frequency range of 2000 MHz and the year 2000 (WARC'92: 1885-2025 MHz and 2110-2200 MHz)

• All 3G standards have been developed by regional standard developing organizations (SDOs)

• In total, proposals for 17 different IMT-2000 standards were submitted by regional SDOs to ITU in 1998. 11 proposals for terrestrial systems and 6 for mobile satellite systems (MSSs).

• Evaluation of the proposals was completed in 1998, and negotiatians to build a consensus among different views were completed in mid 1999. All 17 proposals have been accepted by ITU as IMT-2000 standards. The specification for the

Radio Transmission Technology (RTT) was released at the end of 1999.

The most important IMT-2000 proposals

• UMTS (W-CDMA)– as the successor of GSM

• CDMA2000 – universal wireless communication-13 6

(UWC-136)/EDGE as the successor of the interim standard'95 (IS-95)

• time division-synchroneous CDMA (TD-CDMA)– as the TDMA-based enhancements to D-

AMPS/GSM

ITU IMT2000 Radio Interface Specifications

• 5 were approved by the ITU in November 1999

– IMT DS Wideband CDMA (WCDMA)

– IMT MC cdma 2000

– IMT SC UWC-136 (EDGE)

– IMT TC UTRA TDD or TD-SCDMA

– IMT FT DECT

– DS: Direct Sequence, MC: Multi-Carrier, TC: Time Code, FT :Frequency Time

Key Differences between W-CDMA and cdma2000

Parameter cdma2000 W-CDMAChip rate 3.68 Mc/s 3.84 Mc/sSinchronisation Synchronous AsynchronousFrame duration 20 ms 10 ms

Foreward PilotCommon code

multiplexed pilot

Dedicated time division

multiplexed pilotSignaling ANSI-41 GSM-MAP

UMTS

• UMTS is being developed by Third-Generation Partnership Project (3GPP), a joint venture of several SDOs

– ETSI (Europe)

– Association of Radio Industries and Business/Telecommunication Technology Committee (ARIB/TTC) (Japan)

– American National Standards Institute (ANSI) T-1 (USA)

– Telecommunications Technology Association (TTA) (South Korea)

– Chinese Wireless Telecommunication Standard (CWTS) (China)

Towards UMTS

Evolutionary Concept

Maximum Data Rates