Time
Domain Structure
In
the time domain, the signal is structured in the following parts:
Time Domain Signal Structure
|
Structure Element
|
Description
|
|
Radio Frames
|
10 ms length
|
|
Subframes
|
1 ms length. One frame consists of 10 subframes.
|
|
Slot
|
0.5 ms length. One subframe consists of two slots.
|
|
OFDM symbol
|
Approximately 71.4 μs length. One slot consists of 7 OFDM symbols.
|
Frequency
Domain Structure
Orthogonal
Frequency-Division Multiplexing (OFDM) utilize a large number of subcarriers.
Each subcarrier is orthogonal to all other subcarriers. Subcarrier spacing is
equal to the subcarrier bandwidth, which is 15 kHz, see Figure
Resource
Element
The
smallest resource unit handled in LTE consists of the combination of:
•
The smallest time domain unit, one OFDM symbol
•
The smallest frequency domain unit, one subcarrier
This
unit is called Resource Element (RE). An RE that is not used for transmission
is referred to as a hole
Resource
Block
A
number of REs are grouped into a physical Resource Block (RB). An RB is defined
as follows:
•
In the time domain: 7 OFDM symbol times (one slot)
•
In the frequency domain: 12 consecutive subcarriers
Scheduling
Block
A
scheduling block consists of two RBs adjacent in time and with the same subcarriers.
A scheduling block is the smallest unit that can be scheduled to user
equipment.