Channels and the Protocol Stack of UMTS

Previous posts showed UMTS Network Architecture and we will continue to introduce information and traffic flow through three types of channels:

1. Logical Channels - analogous to airline companies

• Logical channels are functional, conceptual groupings of information and/or traffic
• At this level, it is easy to understand the purposes and objectives of the channels, the types of activities being carried out on each channel, and the call processing steps involved.

W-CDMA Logical Channels

2. Transport Channels - analogous to scheduled flights

Transport channels are the intermediate, individual flows of information which carry subcomponents of the logical channels and which are represented by bits on the physical channels

W-CDMA Transport Channels

3. Physical Channels - analogous to individual aircraft

• These are the real over-the-air channels made up of bits
• At this level, the channels are just patterns of bits - multiframes,frames, timeslots, and the various fields of bits which are defined to occupy them

Logical, Transport, Physical Channel Mapping

Channels and the Protocol Stack

• The mapping between Logical and Transport channels is performed by the LAC layer
• The mapping between Transport and Physical channels is performed by the Physical layer

Channels and the Protocol Stack

Also read UTRAN Network Architecture and Terminology