Physical Control Format Indicator Channel (PCFICH)

Physical Control Format Indicator Channel (PCFICH)

• Since both the PDCCH and PDSCH share the available resources in every subframe (Transmit Time Interval -TTI of 1ms duration), the number of simultaneous users (a measure of capacity) who can be served in a cell will be limited by the availability of PDCCH resources.

• PDSCH throughput is inversely proportional to the PDCCH size (or resources). That is, the smaller the resources reserved for PDCCH the larger the resources available for PDSCH which means higher throughput is achieved in the TTI.

• Where PDCCH occupies larger resources due to the requirement of higher number of users to be served which means large capacity. Now, PDSCH is left with lesser resources to carry data leading to lower throughput. From the above discussion we see that LTE provides us with a handle to leverage either capacity or throughput every TTI as the scenario may warrant.

• The key to this kind of leverage is through the use of the PCFICH (Physical Control Format Indicator Channel). The PCFICH provides the information about the PDCCH resources (number of OFDMA symbols) in the present TTI or subframe.