What is a resource block and resource element in LTE


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Document Category Accounting
Document Target Users Telecom Engineers

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

What is a resource block and resource element in LTE

A Resource Block (RB) is a time- and frequency resource that occupies 12 subcarriers (12×15 kHz = 180
kHz) and one slot
(= 0.5 ms). RBs are allocated in pairs by the scheduler (then referred to as Scheduling Blocks).

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 ?

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
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
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.

What is the relation between transport and resource block in lte ?
LTE: What is the basic difference Resource Allocation type 0 and 1 ?
What is REG Resource Element Group in LTE?
LTE: is there any difference between resource block (RB) and Physical
Resource Block (PRB) ?

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