This question appears in Mumbai University > Wireless Networks subject

Marks: 10 M

Year: Dec 2014

The channel types that are used in the UMTS

1. UMTS Air Interface.

UMTS Air Interface Specifications

2. UMTS Channels

i. There are three types of UTRAN channels: physical channels- these are basic physical resource; logical channels-these are control and traffic channels and are mapped between RLC and MAC; transport channels- these are mapped between MAC and PHY.

Logical Channels:

i. These are mapped between RLC and MAC. These are control channels or traffic channels for data transfer or information transfer between RLC and MAC.

Logical Channels

Transport Channels:

i. In UTRAN transport channelscan be either common (i.e., shared between users) or dedicated channels. They offer information transfer services to the MAC sublayer.

Transport Channels

Physical channels:

i. These are basic physical resource. These are identified using code and frequency and carry data to and from UE.

ii. There is mapping between transport channels and physical channels for the data transfer to and from the higher layers.

iii. The UL (Uplink) common physical channels are physical random access channel (PRACH) used to carry the RACH and fast uplink signaling channel, (FAUSCH)and physical common packet channel (PCPCH) to carry CPCH.

iv. The DL (Downlink) dedicated physical data channel is time multiplexed. The DL dedicated physical channel carries 10 X 2k (k = 0, 1, . . . , 7) bits per slot and may have spreading factor (SF = 512/2^k) from 512 to 4.

v. The DL common physical channels include the following channels: Primary common control physical channel (PCCPCH) carries BCH, rate 30 kbps, SF = 256; continuous transmission; no power control

vi. Secondary common control physical channel (SCCPCH) carries FACH and PCH, transmitted when data is available; SF range is from 256 to 4

vii. Synchronization channel (SCH) is used for cell search. It consists of two sub-channels: primary SCH transmits a modulated code of 256 chips once every slot, and secondary SCH transmits repeatedly 15 codes of 256 chips.

viii. Physical downlink shared channel (PDSCH) carries DSCH; shared by users based on code multiplexing; associated with DPCH.

ix. Acquisition indicator channel (AICH) carries acquisition indicators.

x. Page indicator channel (PICH) carries a page for UE; fixed rate, SF = 256

xi. Primary common pilot channel (PCPICH) is used as phase reference for SCH, PCCPCH, AICH, PICH, and default phase reference for all other DL physical channels, one per cell and broadcast over entire cell.

xii. Secondary common pilot channel (SCPICH) is a continuous channel with the same spreading and scrambling codes, transmitted on different antennas in case of DL transmit diversity; SF = 256. It may be transmitted over only part of the cell.

Responsibilities of the RNC and node B in the UMTS network.

1. Responsibilities of Radio Network Controller (RNC)

An RNC is responsible for the use and allocation of all the radio resources of the RNS to which it belongs. 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. The responsibilities of an RNC are:

i. Intra UTRAN handover

ii. Macro diversity combining/splitting of Iubdata streams

iii. Frame synchronization

iv. Radio resource management

v. Outer loop power control

vi. Iuinterface user plane setup

vii. Serving RNS (SRNS) relocation

viii. Radio resource allocation (allocation of codes, etc.)

ix. Frame selection/distribution function necessary for soft handover (functions of UMTS radio interface physical layer)

x. UMTS radio link control (RLC) sublayers function execution

xi. Termination of MAC, RLC, and RRC protocols for transport channels, i.e., DCH, DSCH, RACH, FACH

xii. Iub’s user plane protocols termination

2. Responsibilities 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 responsibilities 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