# <center><i class="fa fa-edit"></i> Learning the Fundamentals : 5G Basics and Improvement over 4G </center>
###### tags: `Pre-Internship`
:::info
**Goal:**
To gain a basic understanding of the 5G Networking using the existing knowledge of 4G/LTE
- [x] How 5G improves from 4G
- [x] Key Features of 5G
- [x] How Radio Access Network is implemented in 5G

**Resources:**
[Previous Note (4G LTE Systems)](https://hackmd.io/_c5q3GLcSpulNGFESq4eQQ)
[5G Mobile Networks : A System Approach](https://5g.systemsapproach.org/index.html)
:::
## Background
Cellular networks have undergone drastic improvements since its introduction many years ago. With 3G describing the transition to internet connectivity, the first two generations embraced voice and then text, promoting data speeds measured in hundreds of kilobits per second. The industry is currently at 4G (supporting data rates normally calculated in the few megabits per second) and progressing to 5G, promising a tenfold rise in data rates.


The table (which i found on google images) shows how much networking improves over generations of development. With 5G as the latest technology, it shows massive bandwidth, latency, and data rate improvement over the already fast 4G. But 5G is not just about increased bandwidth and lower latency, but 5G represents **a fundamental rearchitecture of the access network in a way that leverages several key technology trends and sets it on a path to enable much greater innovation**

The requirements for this architecture are ambitious, and can be illustrated by three classes of capabilities:

1. To support Massive Internet-of-Things, potentially including devices with ultra-low energy (10+ years of battery life), ultra-low complexity (10s of bits-per-second), and ultra-high density (1 million nodes per square kilometer).
2. To support Mission-Critical Control, potentially including ultra-high availability (greater than 99.999% or “five nines”), ultra-low latency (as low as 1 ms), and extreme mobility (up to 100 km/h).
3. To support Enhanced Mobile Broadband, potentially including extreme data rates (multi-Gbps peak, 100+ Mbps sustained) and extreme capacity (10 Tbps of aggregate throughput per square kilometer).

## Radio Transmission
### Frequency
As discussed in the [previous note](https://hackmd.io/_c5q3GLcSpulNGFESq4eQQ), the higher the frequency, the higher the capacity, but the drawback is the range of propagation. This limits the frequency used in the previous generations technology.

5G took a bold step and uses frequency that of **millimeter wave** (24 GHz-100 GHz) for radio transmission to increase capacity. By evolving the Architecture of 5G, the problem that prevents this high of frequency to be used for transmission in previous generations can be addresed.

### Propagation Loss Handling
The consequences of signal propagation through air are [path loss](https://www.electronics-notes.com/articles/antennas-propagation/propagation-overview/free-space-path-loss.php#:~:text=It%20is%20possible%20to%20calculate,of%20the%20frequency%20in%20use.) which degradates data, and **multipath propagation** which decreases link robustness and even link capacity.

Basically both 4G and 5G implemented [Multiple-Input-Multiple-Output](https://www.youtube.com/watch?v=hIl4ZQb-A70) (basically to put more antennas on a base station to further increase signal strength, with signal processing to handle the output) technology to overcame this problem. MIMO has a lot of advantage, it can be used to increase robustness of the channel, and also it can be used to increase capacity. With the introduction of 5G, MIMO is implemented as the main feature of 5G, called **Massive MIMO**. This implementation also opens a new gate into another feature called :

**Beamforming**

In antenna and propagation theory, if a collection of omnidirectional antennas were to be built in a certain way, and each were given the same signals but the with different phase, there's a phenomenon where each of the signals interfere with each other both constructively and destructively, that the directivity of the antenna changes. This means, if we have enough antennas, we can change the direction of propagation without actually having to rotate the antenna. This feature is used to intensify the energy transmitted to a target which increases range and robustness. More on antenna array designs can be read in [*Antenna Theory Analysis and Design by Constatine A Balanis chapter 6*](https://www.academia.edu/43257444/Balanis_C_A_Antenna_Theory_Analysis_and_Design_4th_Edition).

### Coding and Modulation
The Channel Coding and Modulation Techniquies which implemented in 5G is the same compared to 4G, in which both uses Forward Error Correction Channel Coding, and Orthogonal Frequency Division Multiplexing with QPSK, 16QAM, and 64 QAM for modulation process. Already discussed in [previous note](https://hackmd.io/_c5q3GLcSpulNGFESq4eQQ).

## Basic Architecture
In 4G, Radio Access Network are consisted of eNodeB (or eNB), which is short for evolved Node B. In 5G they are known as gNB. (The g stands for “next Generation”). The Mobile Core is a bundle of functionality (as opposed to a device) that is similar to Evolved Packet Core explained in the previous note.

### Radio Access Network
By analizing the image, the Radio Access Network of 5G has the same [basic layers with 4G](https://hackmd.io/_c5q3GLcSpulNGFESq4eQQ#Explaining-4G-with-Correlation-to-OSI-Layer) which consisted of Radio Resource Channel, Packet Data Convergence Protocol, Radio Link Control, Medium Access Control, and Physical Layer with generally the same functions.

#### Split RAN
In 4G, every process involving Radio Access Network was done in individual eNB(s).Going forward, the 3GPP standard has been extended to allow for multiple split-points, with the partition shown in image below being actively pursued by the operator-led O-RAN (Open RAN) Alliance. It is the split we adopt throughout the rest of this book.

This results in a RAN-wide configuration similar to that shown in image below, where a single Central Unit (CU) running in the cloud serves multiple Distributed Units (DUs), each of which in turn serves multiple Radio Units (RUs). Critically, the RRC (centralized in the CU) is responsible for only near-real-time configuration and control decision making, while the Scheduler that is part of the MAC stage is responsible for all real-time scheduling decisions.

#### Software Defined RAN


In Software Defined RAN, RRC is partitioned into two sub components : control plane provides a 3GPP-compliant way for the RAN to interface to the Mobile Core’s control plane, while the one on the right opens a new programmatic API for exerting software-based control over the pipeline that implements the RAN user plane.

### Mobile Core
The main function of the Mobile Core is to provide external packet data network (i.e., Internet) connectivity to mobile subscribers, while ensuring that they are authenticated and their observed service qualities satisfy their subscription SLAs. An important aspect of the Mobile Core is that it needs to manage all subscribers’ mobility by keeping track of their last whereabouts at the granularity of the serving base station. It’s the fact that the Mobile Core is keeping track of individual subscribers—something that the Internet’s core does not do—that creates a lot of the complexity in its architecture, especially given that those subscribers are moving around.

The 5G Mobile Core, which 3GPP calls the NG-Core, adopts a microservice-like architecture, where we say “microservice-like” because while the 3GPP specification spells out this level of disaggregation, it is really just prescribing a set of functional blocks and not an implementation. A set of functional blocks is very different from the collection of engineering decisions that go into designing a microservice-based system. That said, viewing the collection of components shown in Figure 15 as a set of microservices is a good working model.