This question appears in Mumbai University > Wireless Networks subject

Marks: 10 M

Year: May 15

UMTS Terrestrial Radio Access Network Overview :

i. A radio access network (RAN) is part of a mobile telecommunication system

ii. It resides between a device such as a mobile phone, a computer, or any remotely controlled machine and provides connection with its core network (CN), devices are varyingly known as user equipment (UE).

Fig13. UMTS Terrestrial Radio Access Network Overview

i. The UTRAN consists of a set of radio network subsystems (RNSs)

ii. The RNS has two main logical elements: Node B and an RNC.

iii. The RNS is responsible for the radio resources and transmission/reception in a set of cells.

iv. A cell (sector) is one coverage area served by a broadcast channel. An RNC is responsible for the use and allocation of all the radio resources of the RNS to which it belongs.

v. The RNC also handles the user voice and packet data traffic, performing the actions on the user data streams that are necessary to access the radio bearers.

Functions of Node B

A Node B is responsible for radio transmission and reception in one or more cells to/from the user equipment (UE). The following are the functions of the Node B:

i. Termination of Iubinterface from RNC

ii. Termination of MAC protocol for transport channels RACH, FACH

iii. Termination of MAC, RLC, and RRC protocols for transport channels: BCH, PCH

iv. Radio environment survey (BER estimate, receiving signal strength, etc.)

v. Inner loop power control

vi. Open loop power control

vii. Radio channel coding/decoding

viii. Macro diversity combining/splitting of data streams from its cells (sectors)

ix. Termination of Uuinterface from UE

x. Error detection on transport channels and indication to higher layers

xi. FEC encoding/decoding and interleaving/deinterleaving of transport channels

xii. Multiplexing of transport channels and demultiplexing of coded composite transport channels

xiii. Power weighting and combining of physical channels

xiv. Modulation and spreading/demodulation and dispreading of physical channels

xv. Frequency and time (chip, bit, slot, frame) synchronization

xvi. RF processing

UTRAN logical architecture :

UMTS terrestrial RAN (UTRAN)

UTRAN consist of Core Network (CN), Radio Network Subsystems (RNSs). The RNS has two main elements: Node B and a Radio Network Controllers (RNC).

1) Core Network (CN)

The UMTS network architecture is partly based on existing 2G network components and some new 3G network components. It inherits the basic functional elements from the GSM architecture on the core network (CN) side. The CN provides circuit switched (CS) functions as well as packet switched (PS) functions

2) Radio network controller (RNC):

• The RNC is responsible for control of the radio resources in its area. One RNC controls multiple nodes B.
• The RNC in UMTS provides functions equivalent to the Base Station Controller (BSC) functions in GSM/GPRS networks.
• The major difference is that RNCs have more intelligence built-in than their GSM/GPRS counterparts. For example, RNCs can autonomously manage handovers without involving MSCs and SGSNs.

3) Node B:

• The Node B is responsible for air-interface processing and some radio-resource management functions.
• The Node B in UMTS networks provides functions equivalent to the base transceiver station (BTS) in GSM/GPRS networks. UMTS operates at higher frequencies than GSM/GPRS and therefore the signal coverage range is less.

Fig14. UTRAN logical architecture