LTE :PRB : The actual transmission!

To begin with, Lets start with Physical resource blocks.. Before we move into what to transmit and how to transmit, Let's look at the actual transmission..

The physical channel: means of actual transmission , is made of multiple resource blocks and resource elements.. A resource element is one single carrier over single OFDM symbol. 
Resource block is the smallest portion of the resource that can be allocated.

Here are the different channels for uplink and downlink

Downlink Physical Channels

There are six different types of downlink physical channels.
1. Physical Downlink Control Channel : PDCCH - It contains information regarding transport format and resource allocation.

2. Physical Downlink Shared Channel : PDSCH - It contains information user data and signalling.

3. Physical Downlink Broadcast Channel : PDBCH - It carries system information

4. Physical Multicast Channel : PMCH - multicast or broadcast information is carried.

5. Physical Hybrid ARQ Indicator Channel : PHICH - It carries ACK/NAKs associated with data transmission

6. Physical Control Format Indicator Channel : PCFICH -  Indicates number of OFDM symbols used.


Uplink Physical Channels 

There are just three different uplink channels.

1. Physical Uplink Control Channel : PUCCH - It carries ACK/NAK information along with the CQI 

2. Physical Uplink Shared Channel : PUSCH - It is similar to PDSCH - It carries user data along with some signalling.

3. Physical Random Access Channel - PRACH - It has the random access permeable sent by UE.