What is logical channel prioritization and how does it work ?

Question

I read tat there ll be only 1 logical channel prioritization entity and 1 scheduler per cell. If so, then where it will be? And how UE-MAC will communicate with it?

Answer 1

The Logical Channel Prioritization procedure is required to make sure that all UE serves the UPLINK logical channels in the following sequence (in case of downlink the same can be applied by eNodeB):
- All the logical channels are served in a decreasing priority order up to their configured priority
- if any resources remain, all the logical channels are served in a strict decreasing priority order up to their configured

For the above purpose Each Logical Channel is provided
Prioritized Bit Rate (PBR) and
Maximum Bit Rate (MBR) - Optional

1. In case no MBR is configured the logical channel is served until either the data for that logical channel or the UL grant is exhausted, whichever comes first.
2. Logical channels configured with the same priority shall be served equally the by UE.

src: http://tech.queryhome.com/25830/logical-channel-prioritization-in-lte

Answer 2

Logical Channel Prioritization is used to create MAC PDUs.In LCP,all the three logical channels are allocated upto PBR,which is being specified by RRC.Token bucket model is used as the principle.