Introduction to 3G, GSM, GPRS, EDGE Network

3G 3G refers to the third generation of mobile

telephony (that is, cellular) technology. The third generation, as the name suggests, follows two earlier generations

The first generation (1G) began in the early 80's with commercial deployment of Advanced Mobile Phone Service (AMPS) cellular networks. Early AMPS networks used Frequency Division Multiplexing Access (FDMA) to carry analog voice over channels in the 800 MHz frequency band.

The second generation (2G) emerged in the 90's in which some operators used Code Division Multiple Access (CDMA) to multiplex up to 64 calls per channel in the 800 MHz band.

Across the world, many operators adopted the Global System for Mobile communication (GSM) standard, which used Time Division Multiple Access (TDMA) to multiplex up to 8 calls per channel in the 900 and 1800 MHz bands.

GPRS is sometimes called 2.5G, since it predates 3G but is more advanced than 2G.

The International Telecommunications Union (ITU) defined the third generation (3G) of mobile telephony standards – to facilitate growth, increase bandwidth, and support more diverse applications.

For example, GSM could deliver not only voice, but also circuit-switched data at speeds up to 14.4 Kbps. But to support mobile multimedia applications, 3G had to deliver packet-switched data with better spectral efficiency, at far greater speeds.

technologies evolved as follows -

1. General Packet Radio Service (GPRS) offered speeds up to 114 Kbps.

2. Enhanced Data Rates for Global Evolution (EDGE) reached up to 384 Kbps.

3. UMTS Wideband CDMA (WCDMA) offered downlink speeds up to 1.92 Mbps.

4. High Speed Downlink Packet Access (HSDPA) boosted the downlink to 14Mbps.

GSM Global System for Mobile (GSM) is cellular standard developed to

cater voice services and data delivery using digital modulation. Its ubiquity makes international roaming very common between

mobile phone operators, enabling subscribers to use their phones in many parts of the world. GSM differs from its predecessors in that both signaling and speech channels are digital,

GSM also pioneered a low-cost (to the network carrier) alternative to voice calls, the short message service (SMS, also called "text messaging")

Newer versions of the standard were backward-compatible with the original GSM phones. For example, Release '97 of the standard added packet data capabilities, by means of General Packet Radio Service (GPRS). Release '99 introduced higher speed data transmission using Enhanced Data Rates for GSM Evolution (EDGE).

GSM System Architecture

BSC

BSC

MSC

MS

MS

MS BTS

BTS

BTS

GMSC

PSTNISDNPDN

EIRAUC

HLR

VLR

GSM System Architecture

Mobile Station (MS)

Mobile Equipment (ME)Subscriber Identity Module (SIM)

Base Station Subsystem (BSS)

Base Transceiver Station (BTS)Base Station Controller (BSC)

Network Switching Subsystem(NSS)

Mobile Switching Center (MSC)Home Location Register (HLR)Visitor Location Register (VLR)Authentication Center (AUC)Equipment Identity Register (EIR)

Mobile Station (MS)1. Mobile Equipment

Portable, hand held device Uniquely identified by an IMEI (International Mobile Equipment

Identity) Voice and data transmission Power level : 0.8W – 20 W 160 character long SMS.

2. Subscriber Identity Module (SIM) Smart card contains the International Mobile Subscriber

Identity (IMSI) Allows user to send and receive calls and receive other

subscribed services Protected by a password or PIN Can be moved from phone to phone – contains key

information to activate the phone

Base Station Subsystem (BSS)

1. Base Transceiver Station (BTS) Encodes, encrypts,multiplexes,modulates and feeds

the RF signals to the antenna. Communicates with Mobile station and BSC

2. Base Station Controller (BSC) Assigns Frequency and time slots for all MS’s in its

area Handles call set up It communicates with MSC and BTS

Network Switching Subsystem(NSS)

Mobile Switching Center (MSC)

Heart of the network Manages communication between GSM and other networks Call setup function and basic switching Call routing Billing information and collection Mobility management

- Registration- Location Updating

MSC does gateway function while its customer roams to other network by using HLR/VLR.

Home Location Registers (HLR)

- permanent database about mobile subscribers in a large service area (generally one per GSM network operator)

- database contains IMSI, prepaid/postpaid, roaming restrictions, supplementary services.

Visitor Location Registers (VLR)

- Temporary database which updates whenever new MS enters its area, by HLR database

- Controls those mobiles roaming in its area

Authentication Center (AUC)

- Protects against intruders in air interface- Maintains authentication keys and algorithms and

provides security.- Generally associated with HLR

Equipment Identity Register (EIR)- Database that is used to track handsets using the IMEI

(International Mobile Equipment Identity)- Only one EIR per PLMN (public land mobile network )

GPRS (General Packet Radio Service)

General Packet Radio Service (GPRS) is a new bearer service for GSM that greatly improves and simplifies wireless access to packet data networks,e.g to the internet.

It uses the existing GSM network to transmit and receive TCP/IP based data to and from GPRS mobile devices.

GPRS is a non-voice service added to existing TDMA time division multiple access networks, one of the 2.5G technology upgrades. TDMA is the underlying transport mechanism used by GSM networks.

Comparison of GSM & GPRS GSM GPRS

Data Rates 9.6 Kbps 14.4 to 115.2 Kbps

TDMA Uses one out of seven time slots

uses 4 +1 time slots

Billing Duration of connection

Amount of data transferred

Type of Connection

Circuit – Switched Technology

Packet - Switched Technology

Benefits of GPRS

High Speed (Data Rate 14.4 – 115 kbps) Efficient use of radio bandwidth (Statistical

Multiplexing) Circuit switching & Packet Switching can be

used in parallel Constant connectivity

GPRS BACKBONE NETWORK

inter-PLMN

GPRS backbone

External Packet Data Network (PDN)

intra-PLMN

GPRS backbone

intra-PLMN

GPRS backbone

PLMN1

PLMN2

SGSN

SGSNSGSN

GGSNGGSN

Border gatewayBorder

gateway

Gp

GnGi

Gn

Gn

BTS BTS

BSCBSC

HostRouter

LAN

MS

Gi

Gn

GnGp

GPRS Network

GPRS network provides mobility management, session management, and transport for internet protocol packet services in GSM network.

GPRS Support Node (GSN)- It is node which support use of GPRS in GSM network. There are two key variant-

1. GGSN

2. SGSN

GGSN (Gateway GPRS Supporting Node)

It is main component of GPRS for internetworking between GPRS and external network. Thus it is router for sub network.

It converts GPRS packets to appropriate PDP format to send them on corresponding data network. In other direction PDP address to GSM address of destination host.

It is responsible for IP address assignment.

SGSN (Serving GPRS Supporting Node)

It is responsible the delivery of data packets from and to the mobile with in geographical area.

The location register of SGSN stores location information (current cell, VLR) and user profile of GPRS users registered with SGSN.

Access point When a mobile user wants to use GPRS it must first

activate PDP context (IP address and IMSI) When a GPRS mobile phone sets up a PDP

context, the access point is selected and access point name is determined,

An access point is: An IP network to which a mobile can be connected A set of settings which are used for that connection A particular option in a set of settings in a mobile phone

• This access point is then used in a DNS query to a private DNS network. This process (called APN resolution) finally gives the IP address of the GGSN which should serve the access point

EDGE Enhanced Data Rates for GSM Evolution (EDGE) is

used to increase network capacity and data rates in mobile networks. EDGE provides data rates up to 384 Kbps.

EDGE uses the same TDMA (Time Division Multiple Access) frame structure, logic channel and 200kHz carrier bandwidth as today's GSM networks, which allows it to be overlaid directly onto an existing GSM network. For many existing GSM/GPRS networks, EDGE is a simple software-upgrade.

EDGE is particularly useful as a GPRS solution for the larger data services, such as streaming video and video conferencing.