PCFICH - Physical Control Format Indicator Channel
Physical channels carries Control signals as wells as Data signals. PCFICH is the channel which carries the control signals in DL.
PCFICH carries the control format indicator CFI, which will tell about the PDCCH usage. So without decoding the PCFICH, its not possible for the UE to decode the PDCCH & in turn PDSCH.
How PCFICH RE's are allocated?
PCFICH is carried in the 1st OFDM symbol of every Subframe in 4 REG's each having 4 RE's.
So total RE's in a PCFICH = Number of Resource Element groups * Number if RE's per group
= 4 * 4 = 16 RE's in every Subframe
This implies, PCFICH will be carried on the 1st OFDM symbol of every subframe over 16 subcarriers in the frequency domain.
One important info to be noted down is, All the 16 subcarriers are not continuous. Lets see how the Resource Element Grouping made for PCFICH.
PCFICH Positioning:
PCFICH positioning can be identified by the UE, with the help of 2 parameters, which UE already knows about it.
1. CELL ID
2. Channel Bandwidth
Both the parameters UE's would have got it from the PSS & SSS decoding. Now its to make use of it & decode other channels in the treasure hunt.
3GPP Spec 36.211 talks about the PCFICH decoding.
The 4 REG's are mapped to 4 different values calculated from the above formula.
You can find the PCFICH resource allocation in the Grid for the Cell ID = 0 & Ch BW = 1.4 Mhz below:
Similary the REG spacing will differ for different bandwidth. PCFICH plays an important role in the Physical cell allocation of the live LTE network for better cell edge signalling & throughput. we will discuss more about it in the later blogs.
Physical channels carries Control signals as wells as Data signals. PCFICH is the channel which carries the control signals in DL.
PCFICH carries the control format indicator CFI, which will tell about the PDCCH usage. So without decoding the PCFICH, its not possible for the UE to decode the PDCCH & in turn PDSCH.
How PCFICH RE's are allocated?
PCFICH is carried in the 1st OFDM symbol of every Subframe in 4 REG's each having 4 RE's.
So total RE's in a PCFICH = Number of Resource Element groups * Number if RE's per group
= 4 * 4 = 16 RE's in every Subframe
This implies, PCFICH will be carried on the 1st OFDM symbol of every subframe over 16 subcarriers in the frequency domain.
One important info to be noted down is, All the 16 subcarriers are not continuous. Lets see how the Resource Element Grouping made for PCFICH.
PCFICH Positioning:
PCFICH positioning can be identified by the UE, with the help of 2 parameters, which UE already knows about it.
1. CELL ID
2. Channel Bandwidth
Both the parameters UE's would have got it from the PSS & SSS decoding. Now its to make use of it & decode other channels in the treasure hunt.
3GPP Spec 36.211 talks about the PCFICH decoding.
The 4 REG's are mapped to 4 different values calculated from the above formula.
You can find the PCFICH resource allocation in the Grid for the Cell ID = 0 & Ch BW = 1.4 Mhz below:
Similary the REG spacing will differ for different bandwidth. PCFICH plays an important role in the Physical cell allocation of the live LTE network for better cell edge signalling & throughput. we will discuss more about it in the later blogs.
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