An overview of 3G-UMTS Network

The network architecture describes all the network elements and the existing physical link between the network elements. The architecture defines the functionality of each network elements and their interaction with other network elements.

The UMTS (Universal mobile telecommunication system) is a 3G (Third generation) wireless system. The UMTS uses a wideband CDMA technology for transmission, and a more efficient modulation than the GSM (2nd Generation). This allows UMTS to reach higher utilization, and offer higher bandwidth to end user. UMTS offers bit rates up to 2Mbps for users.

UMTS consists of three domains:
1. Core network (CN)
2. UMTS terrestrial Radio access network (UTRAN)
3. User Equipment (UE)



A 3G network includes two main sections: a packet switched core network (PS-CN), which is based on IP, and one or more Radio access network (RAN). Each RAN is divided into subsystems, each consisting of one controller, called Base station controller (BSC) in GPRS and Radio network controller (RNC) in UMTS, connected to several Base Transceiver station (BTSs).

The interfaces involved in 3G network are: Iu, Iub, and Iur. The Iu interface is an interface between RNC and Core network elements. The Iub interfaces exist between the Node B and RNC. The Iur interfaces exist between the two RNCs. Additionally Uu represents Air interface between user equipment (UE) and Node B.
WCDMA is used in UTRAN air interface. WCDMA has two mode of operation: Frequency division duplex (FDD) and Time division duplex (TDD).

The functionalities of Node B:
1.Air interface transmission/reception
2.Modulation/Demodulation
3.CDMA physical channel coding
4.Micro diversity
5.Error Handling
6.Closed loop power control

The functionalities of RNC are:
1.Radio Resource control
2.Admission control
3.Channel allocation
4.Power control settings
5.Handover control
6.Macro diversity
7.Ciphering
8.Broadcast signaling
9.Open loop power control

User equipment (UE) has the same identity pattern as GSM.
1.International mobile subscriber identity (IMSI)
2.Temporary mobile subscriber identity ( TMSI)
3.Mobile station ISDN (MSISDN)
4.International mobile station equipment identity (IMEI)
5.Other patterns.

Global System for Mobile Communication (GSM) Network

Radio connections were first used for wireless communications in the late 19th century, we can consider this as first generation communication system.

A Further very significant development was second generation mobile system (e.g. GSM). GSM stands for Global system for Mobile Communication. The GSM standard is a consistent and open standard for Mobile communication system. GSM is the second generation mobile network system which provides very good voice quality with the coverage of wide frequency range from 900 MHz to 1800 MHz band. GSM is a digital Mobile communication system.

Some examples of the first and second generation mobile systems with GSM standards are:
1.Cellular mobile system
2.Satellite system
3.Paging system
4.Wireless Local Loop (WLL)

The GSM network Architecture



Mobile Station (MS) – carried by the user. Mobile station consists of Mobile equipment (ME) and Subscriber identity module (SIM).

Base Transceiver station (BTS) - it defines a cell* and responsible for radio link protocol with the MS.

Base Station Control (BSC) - controls BTS and manage radio channels setup.
Mobile Switching center (MSC) - is the main component of Network Switching Subsystem (NSS). It works as normal switching unit for ISDN and PSTN network and it’s provide the functionality as registration, authentication, location update, handover and call routing for the subscriber in roaming.

Home Location Register (HLR) – stores the current location of the subscriber, authentication details and the services which subscriber can access.

Visitor Location Register (VLR) – contains the some information of the subscriber from HLR. When subscriber move from one MSC to other MSC, VLR connected to the new MSC request the information from corresponding HLR.

Authentication Center (AC) - this unit is for security. AC provides the data for authentication and encryption function.

Equipment Identity Register (EIR) –is a database which contains the list of all valid mobiles equipments in the network. Every mobile equipment in the network has unique IMEI (international mobile equipment identity).

Operation and Maintenance control (OMC)

The GSM network structure is divided into three parts:
1.Network Switching Subsystem (NSS)
2.Base Station Subsystem (BSS)
3.Operation and Support Subsystem (OSS)


The NSS and BSS are the most responsible part in GSM network for call establishment. The NSS consists of MSC, HLR, VLR, AC and EIR. The NSS takes care of call control functions. Calls are always connected by and through the NSS.

The BSS consists of BTS and BSC. BSS is responsible for radio path control and every call is connected through the BSS.

The Operation and Support subsystem is connected to NSS and BSS. The OSS is the operation and maintenance related part of the network and it is needed for the control of the whole GSM network. The network operator observes and maintains network quality and service offered through the OSS.

All the three subsystems in GSM network are linked by air interface, A- interface and O&M interface.


*There are five different cell sizes in a GSM network—macro, micro, pico, femto and umbrella cells.

Wireless Communication

Before I cover detailed cellular network in my forthcoming blogs, I plan to cover wireless communication paradigm in short. As the name indicates, wireless communication, it clearly means the communication without the “wire”. The wireless communication has potential to provide high speed, high quality information exchange between the devices which are positioned in distant places.

Types of Wireless communication:
1. Radio transmission
2. Microwave transmission
3. Infrared and millimeter waves
4. Lightwave transmission

The range of wireless systems:


Applications of wireless in different spheres of operations
1.Broadcasting service
2.Mobile communication of voice and data
3.Fixed service
4.Satellite
5.Other uses as military and scientific use.

Having said this, in the current blog we limit to Mobile communication and glance thru the various generation of mobile communication and their features.

Evolution of Mobile communication:

1G- First generation:

1.Mobile network launched in 1980s.
2.Analogue in nature
3.Used for voice call only.
4.Analogue Modulation, mostly FM
5.FDMA/FDD multiple access (the system was a multiple access one, because a second caller could use the same channel, once the first caller had hung up. Such a system is called "frequency division multiple access" (FDMA).)
6.Examples AMPS

2G-Second generation:

2G - Second Generation mobile telephone networks were the logical next stage in the development of wireless systems after 1G, and they introduced for the first time a mobile phone system that used purely digital technology.
1.Developed for voice communication
2.Digital system, Digital modulation
3.TDMA/FDD and CDMA/FDD multiple access
4.Example: one of the successful 2G digital systems is GSM.
•TDMA/FDMA
•900 MHz and 1800 MHz band
5.IS-95
•CDMA

3G-Third generation:

3G – Third Generation mobile telephone networks are the latest stage in the development of wireless communications technology. This support much higher data transmission rates and offer increased capacity, which makes them suitable for high-speed data applications as well as for the voice calls.
1.Digital Modulation
2.The main 3G technologies include UMTS (Universal mobile telecommunication service) with WCDMA and cdma2000.
3.Support data service as multi-megabits mobile internet access and multimedia application.
4.Features as TV Streaming, video conferencing, web browsing, email, paging, fax.