# Difference between LTE and 5G NR Physical Layer Timing

This page mentions difference between LTE physical layer timing units and 5G NR physical layer timing units. It mentions formula for 5G NR Physical layer sampling time, 5G NR frame duration and 5G NR subframe duration.

Introduction:
As shown in the figure-1, a 5G NR frame is of 10ms duration. A frame has 10 subframes having 1ms duration each. The number of slots per subframe depends on subcarrier spacing. Each slot can have either 14 OFDM symbols or 12 OFDM symbols based on cyclic prefix type.

Refer 5G NR Frame structure >> and LTE frame structure >> for more information. Physical layer sampling instant depends on number of FFT points and subcarrier spacing. Let us understand physical layer parameters.

## 5G NR Physical layer Sampling Time

Following formula-1 is used to calculate 5G NR physical layer time unit (Tc). It is known as sampling time in time domain.

➤Example:
• For ΔFmax = 480000 Hz (i.e. 480 KHz subcarrier spacing)
• Nf = 4096 (i.e. FFT size)
• Tc = 0.509 ns

## 5G NR Frame duration and subframe duration

Following formula-2 is used to express 5G NR frame duration and 5G NR subframe duration.

➤Tf = (480000*4096/100)*0.509*10-9 = 0.010 sec = 10 ms
➤Tsf = Tf/10 = 1 ms

## LTE Physical layer Sampling Time

Using LTE system bandwidth of 20 MHz having 2048 FFT points and subcarrier spacing of 15 KHz, LTE sampling time unit (Ts) is derived as follows using formula-1 above.
• ΔFmax = 15000, Nf = 2048
➤ Ts = (1/(15000*2048)) = 3.2552 x 10 -8
➤ Ts = 32.552 ns

## Relation between LTE and 5G NR Sampling Times

➤ K = LTE sampling time/5G NR sampling time = Ts/Tc
➤ K =64