Evolution from GSM to UMTS

Evolution from GSM to UMTS

Difference between 1G and 2G:
– Symmetric data transfer possibility.
– Service palette adopted from Narrowband ISDN.

Driving idea in GSM: to define several open interfaces.
– Operator may obtain different network components form different suppliers.
– Strictly defined interface determines how the functions are proceeding in the network
and which functions are implemented internally by the network element.

GSM Network elements
• MS: mobile equipment + subscriber data (SIM - Service Identity Module)

• Base Station Controller (BSC):
– Maintains radio connections towards Mobile Station.
– Maintains terrestrial connection towards the NSS.

• Base Transceiver Station (BTS):
– Air interface signalling, ciphering and speech processing.

• Mobile Service Switching Centre (MSC):
– Call control.
– BSS control functions.
– Internetworking functions.
– Charging,
– Statistics,
– Interface signalling towards BSS and external networks.

• Serving MSC: BSS connections, mobility management, inter-working.

• Gateway MSC: Connections to the other networks.

• Visitor Location Register (VLR): local store for all the variables and functions needed to handle calls in the area related to VLR.

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STEP 1

Value Added Service (VAS) platform

Simple platform for supporting certain type of services in GSM. (Short Message Service Centre (SMSC), Voice Mail
System (VMS))
– Use standard interface towards GSM. May or may not have external interfaces
towards other networks

STEP 2

GPRS

STEP 3

EDGE

• Exchanged Data Rates for Global/GSM Evolution (EDGE):
– New modulation scheme. (8 PSK)
– Different coding classes. Maximal data rate 48 kbps per channel.
• EDGE phase 1:
– channel coding and modulation methods to provide up to 384 kbps data rate.
– One GPRS terminal gets 8 time slots. The channel should be good.
• EDGE phase 2:
– Guidelines for achieving high data speed for circuit switching services.
• Data rates achieved almost equal to the ones provided by UMTS.
• Data rates not available everywhere in the cell

STEP 4

New Radio interface.
• More suitable for packet data support.
• Interoperability with GSM:
– GSM radio interface modified to broadcast CDMA system information. WCDMA networks transfer also GSM data.
– Possibility to set 2G MSC/VLR to handle the wideband radio access, UTRAN.
• Customised applications for Mobile network Enhanced Logic (CAMEL):
– Possibility to transfer service information between networks.
– In the future almost CAMEL will be involved in all transactions between networks.
• CS domain elements are able to handle 2G and 3G subscribers.
– Changes (upgrades) in MSC/VLR and HLR/AC/EIR.
– For example SGSN
• 2G responsible for mobility management (MM) for packet connections
• 3G MM divided between RNC and SGSN.
• Services
– Initially 3G offers same services as 2G.
– Services transformed into PS domain.
• Trends
– Separation of connections in control and services.
– Conversion of the network towards all IP.
– Multimedia services provided by the network.

STEP 5

The 3GPP R4 introduces separation of connection, its control, and services for CN CS domain.
• Media Gateway (MGW): an element for maintaining the connection and performing switching function when required.
• MSC server: an element controlling MGW.
• Packet switched voice (Voice Over IP).
– The CS call is changed to the packet switched call in MGW.
– For higher uniformity the CS and PS domain is mediated by IP Multimedia Subsystem.
• CAMEL will have a connection to the PS domain elements.

STEP 6