UMTS - Channels

3views

written 8.7 years ago by

teamques10 ★ 68k

• modified 5.4 years ago

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:

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

Channel type	Channel	Mainly used as/for	Direction( Uplink -UL/Downlink -DL)
Control channel,(CCH)	Broadcast control channel (BCCH)	Broadcasting system control information	DL
-	Paging control channel (PCCH)	Transfer of paging information	DL
-	Dedicated control channel (DCCH)	Transmission of dedicated control information	Bidirectional
-	Common control channel (CCCH)	Transmission of control information	Bidirectional
-	Shared Channel control channel (SHCCH)	Transmission of control information for TDD only	Bidirectional
-	Opportunity Driven Multiple Access(ODMA)Dedicated control channel (ODCCH)	Transmission of dedicated control information between UEs	Bidirectional
-	ODMA Common control channel (OCCCH)	Transmission of control information between UEs	Bidirectional
Traffic Channel (TCH)	Dedicated traffic channel (DTCH)	Transfer of user information	Bidirectional
-	ODMA Dedicated traffic channel (ODTCH)	Transfer of user information between UEs. An ODTCH exists in relay link.	Bidirectional
-	Common traffic channel (CTCH)	Transfer of dedicated user information for all or a group of specified UEs.	DL

Transport Channels:

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

Channel,type	Channel	Mainly used as/for	Direction( Uplink -UL/Downlink -DL)
Common transport channel (CTCH)	Random access channel (RACH)	A contention based channel to transmit small data	UL
-	ODMA random access channel (ORACH)	A contention based channel in relay link	Bidirectional
-	Common packet channel (CPCH)	A contention based channel to transmit bursty data traffic	UL
-	Forward access channel (FACH)	Small data transmission without closed loop power control	DL
-	Downlink shared channel (DSCH)	Shared channel by several UEs carrying dedicated control/traffic data	DL
-	Uplink shared channel,(USCH)	Shared channel by several UEs carrying dedicated control/traffic data in TDD mode only	UL
-	Broadcast channel (BCH)	Broadcasting system information into an entire cell	DL
-	Paging channel (PCH)	Broadcasting control information into an entire cell	DL
Dedicated transport channel (DTCH)	Dedicated channel (DCH)	A channel dedicated to one UE	UL or DL
-	fast uplink signalling channel,(FAUSCH)	To allocate dedicated channels in conjunction with FACH	UL
-	ODMA dedicated channel (ODCH)	A channel dedicated to one UE used in relay link	UL or DL

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 signalling 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.

ADD COMMENT EDIT