Monday, September 9, 2013

Deriving the Total Throughput Supported in LTE


In LTE:

Each Resource Block refers to
   0.5 msec
   12 Sub carriers (Each Sub Carrier is of 15khz)
   7 Symbols (Normal Cyclic Prefix)

Which makes 84 Resource elements per Resource Block.


1 Sec = 2 Slots = 2 Resource Blocks

So For 20Mhz is the Bandwidth:
Number of RBS  X 2 Slot (per Sec) * Number of RES
= 100 * 2 * 84 
=16800 Resource Elements

So, per sec eNodeB total resources are 16800 Resource Eleements

Considering 64 QAM is the Modulation, Each Resource Element carries 6 Bits
=16800 * 6 
= 100800 bits per milli second
= 100800 * 1000 = 
= 100800K 
= ~100 Mbits per second

Considering 4 X 4 DL MIMO = ~400 Mbits per second

As we know that DL Grid also possess other entities like PDCCH, PSS, SSS, MIB, PHICH,Reference Signals, etc., and other Factors like Modulation,etc.,

Considering 25% of 400 Mbits occupies the above 
It brings down to ~300 Mbits per second

References:
TS 36.213 Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures
Section 7.1.7 - Modulation order and transport block size determination 





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