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What is a resource block and resource element in LTE?

+5 votes

How the capacity depends upon these resource blocks and how large it is ?

posted Feb 21, 2014 by Iti Jindal

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2 Answers

+4 votes

A Resource Block (RB) is a time- and frequency resource that occupies 12 subcarriers (12x15 kHz = 180 kHz) and one slot
(= 0.5 ms). RBs are allocated in pairs by the scheduler (then referred to as Scheduling Blocks).

Resource Block
12 subcarriers á 15 kHz = 180 kHz in frequency domain and one slot (0.5 ms) in time domain

answer Feb 21, 2014 by Hiteshwar Thakur
well explained.
Well, there is a statement above MAC scheduler allocates resource in RB pair. where it is mentioned and why ? Can you please provide some detail about scheduler ?
+4 votes

Resource Element = Covered by 1 sub carrier and one symbol period i.e 1 Symbol
Resource Block = Covered by 12 Subcarriers and 6 or 7 symbols(Based on Cyclic prefix)

We can calculate the capacity if we know the Bandwidth allocated,Modulation scheme used and Cyclic Prefix type.
Bandwidth Allocated = 5MHz
Modulation Scheme = QPSK(2 its per symbol)
Cyclic prefix used = Normal Cyclic Prefix (7 symbols in a slot)

Capacity = No of bits transferred in a sub frame / Duration of the Subframe(i.e 1milli sec)

Calculation No of Bits transferred in a Subframe

Total number of Resource block in a slot = Bandwidth / (Each subcarrier bandwidth * no of subcarriers in a Resource Block)
Bandwidth = 5Mhz
Each sub carrier width = 15Khz
No of sub carriers in a Resource Block = 12 (As 12 Subcarrier is 1 Resource block )

Calculation of total no of resource blocks in 5MHz Bandwidth

so Resource block in one slot = 5 Mhz / (15 KHz *12 ) = 27.77 (But used RBs will be 25 for 5MHz bandwidth)
so Total Resource block in one subframe = 2 * Resource blocks in a slot = 50 RBs

Calculation of total no of symbols/Resource Elements in 5MHz Bandwidth
Total no of symbols / Resource Elements = 50 * no of symbols(REs) in a Resource block
No of symbols(REs) in a resource block = 12 subcarrier * 7 symbols = 84 symbols(REs)
Total symbols(REs ) in 50 Resource blocks = 50 * 84 = 4200 Resource Elements.

****Calculation of total no of bits sent in 5MHz Bandwidth in one subframe ****

In one symbol we can send no of bits at a time which depends on the modulation scheme (like BPSK,QPSK ,64QAM
BPSK - 1 bit,QPSK - 2 bit ,64 QAM - 6bits in a Symbol/ Resource elements
We will consider QPSK Scheme so in one symbol 2bits we can send.
So 1 Symbol = 2 bits.

So total no of Bits sent in a subframe = 2 * 4200 = 8400 bits.

So capacity = 8400 / 1ms = 8.4 MBPS

So capacity in 5MHz Bandwidth with QPSK Modulation with normal cyclic Prefix is 8.4MBPS.

if Modulation scheme is BPSK, 1 bits in a symbol = 1 * 4200 / 1ms = 4.2 MBPS
if Modulation scheme is 64QAM , 6 bits in a symbol = 6 * 4200 / 1ms = 25.2 MBPS.

answer Feb 26, 2014 by Sachidananda Sahu
No of symbols is 7/6 but REs are 84.Please be clear with ur answer.
Thank you sahu.
can you explain down link channel allocation in resource block?like PHICH,and7 other channels.
Its very old thread, will you like to ask fresh question?
thank you
Very helpful. Thanks!
very helpful... i need help in resource block allocation in matlab. can you help me
I don't have idea about MATLAB to simulate these things, Search for online resource you may get it.
Well explained Mr Sahu
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+1 vote

I need help in MATLAB coding. I am working on resource allocation in LTE. Can someone help me in coding. I am not getting a point how to allocate resource blocks to the user at downlink and what parameters should I consider.
If I am having system BW 15 MHz, the number of resource blocks will be 75. I have 25 small cells and random user. Now I have to allocate these resource blocks among small cell users.

Kindly help me how should I code?