# 5G NR Physical Layer Design
[TOC]
## 5G NR Physical Layer
There are main physical layer differences between 4G and 5G. In 5G, the use cases is mainly for Mobile Broadband Access (MTC) and it is emphasize the term of throughput or data rate. Latency up to 10 ms. Band below 6 GHz. Bandwidth up to 20 MHz. Subcarrier spacing is fixed which is 15 kHz. Frequency allocation is for UE that need to decode the whole bandwidth. The always on signal is used to cell specific RS, PSS, SSS, and PBCH. Meanwhile in 5G, the use cases are to service differentiation such as eMBB, mmTC, and URLL. Latency is less than 1 ms. Band up to 60 MHz. Bandwidth up to 100 MHz below 6 GHz / up to 400 MHz above 6 GHz. Subcarrier spacing is variable. Frequency allocation is use of bandwidth parts. 5G avoid always on signals, the only one is the SS block.
- **5G Modulation and Coding Schemes (MCS)**
MCS defines the number of useful bits which can carried by one symbol. 5G still use OFDM-based modulation as in LTE such as OFDMA, CP-OFDMA, and SC-FDMA. NR support QPSK, 16 QAM, 64 QAM, and 256 QAM. 256 QAM is used to support higher data rate transmission. In NR also support π/2-BPSK that is standard BPSK signal by multiplying the symbol sequence with a rotating phasor with phase increments per symbol period of π/2. This is used to reduce Peak-to-Average Power Ratio (PAPR) because other scheme will result in higher PAPR which cause higher power consumption. It also used to enhanced power amplifier efficiency at lower data rates which is important for mMTC services. Modulation defines how many bits can be carried by a single Resource Element (RE), irrespective of whether it’s useful bit or parity bits. As we can see on this table below.
- **Code Rate**
Code rate can be defined as the ratio between useful bit and total transmitted bit (useful + redundant bit). The redundant bits are added for Forward Error Correction (FEC).

## 5G NR Terminologies
- **Subcarrier Spacing**
The subcarrier spacing is scalable and specified as 15 x 2µ kHz, where µ is an integer and 15 kHz is the subcarrier spacing used in LTE. Subcarrier spacing can be also named as numerology. NR has a scalable OFDM numerology to enable diverse services on a wide range of frequencies and deployments. There are several different types of subcarrier spacing in the following table.
5G NR has different numerology because NR should cover very wide range of operating frequency such as 3 GHz, 6GHz, and mmWave and it is hard (almost impossible) to come up with sigle numerology (subcarrier space) that can cover the whole of these range without sacrificing too much of efficiency or performance.
- **Frame and Subframe**
Downlink and uplink transmissions are organized into frames with 10 ms duration, each consisting of ten subframes of 1 ms. Each frame is divided into two equally sized half frames of five subframes each with half frame 0 consisting of subframes 0 – 4 and half frame 1 consisting of subframes 5 – 9. In total, there are 10 subframes in one frame.
- **Slot**
Number of slots per subframe varies with carrier spacing that can be 1, 2, 4, 8, or 16 slots per subframe. As we can see in the following picture.

1 frame = 10 ms = 10 subframe
1 subframe = 1 ms
1 slot = 1 ms (15 kHz)
The larger carrier spacing, the slot become decrease
1 slot = 14 symbols

## MIMO in 5G
5G using massive MIMO that is the extension of traditional MIMO technology to antenna arrays having a large number of controllable antennas. Transmission signals from the antennas are adaptable by physical layer or phase control, so in 5G can enhance coverage and capacity.

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# Comment
The most important difference of physical layer in 4G and 5G is subcarrier spacing in 4G is fixed (15 kHz). Meanwhile subcarrier in 5G is variable named numerology. Also, 5G NR uses CP-OFDM for uplink as well as DFT-s-OFDM depending on use case. While in 4G using SC-FDMA.

# Personal Studying Report
- Create summary.
- Review the topic that has been learned today.
- Learned more about subcarrier spacing in 5G.

# Discussion with Team
- Discuss about final presentasion on group line.
- Discuss about the OFDM Assignment