Evolution and Innovation of Multiple Access Technologies in 5G Communications

# 1. Introduction

## 1.1 Background and Development of 5G Communication

In today's society, as the level of informatization continues to rise, there is an ever-growing demand for high-speed, high-capacity, and low-latency wireless communication. As the fifth-generation mobile communication technology, 5G offers higher bandwidth, lower latency, and greater connection density. It is considered one of the key technologies for realizing intelligent societies, the Internet of Things (IoT), and the Industrial Internet.

The backdrop of 5G communication can be traced back to the previous generation of mobile communication technology, 4G. With the widespread adoption of 4G networks and the increasing demand for high-speed mobile broadband among users, traditional multiple access technologies have struggled to meet the requirements of large-capacity wireless communication. Consequently, researchers began exploring new multiple access technologies to improve the efficiency of wireless spectrum usage and communication quality.

## 1.2 The Importance and Applications of Multiple Access Technology in 5G Communication

Multiple access technology is a method that allows multiple users to share limited spectral resources. It achieves parallel transmission by assigning different users' signals to different times, frequencies, or codes, thereby enhancing spectrum utilization and communication capacity.

In 5G communication, multiple access technology plays a crucial role. Due to the need for 5G networks to support a massive number of connections and an enormous amount of data transmission, multiple access technology can effectively manage spectrum resources, allowing multiple users to communicate reliably at the same time. Moreover, multiple access technology can increase system capacity and coverage, providing users with a better communication experience.

Multiple access technology has various applications in 5G communication, including Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA), and Orthogonal Frequency Division Multiple Access (OFDMA). Each multiple access technology has its unique characteristics and advantages and plays a significant role in 5G communication. Below, we will introduce each multiple access technology and its applications and developments in 5G communication.

# 2. FDMA

In 5G communication, multiple access technology is widely used to improve spectrum utilization and system capacity. The first generation of multiple access technology is Frequency Division Multiple Access (FDMA). In FDMA, channels are divided into different frequency bandwidths, and each user is assigned an independent frequency bandwidth for communication.

### 2.1 Principles and Characteristics of FDMA

The principle of FDMA is to divide the frequency band into several small narrowbands, with each user being allocated a frequency band for communication. In this way, the signal frequency bands of different users do not overlap, allowing for parallel data transmission.

The characteristics of FDMA technology include:
- Clear division of frequency band resources, with each user being assigned a fixed frequency band, avoiding spectrum conflicts.
- Good real-time performance, as each user can exclusively occupy a frequency band, free from interference from other users.
- Suitable for applications with high real-time requirements, such as voice communications.

### 2.2 Optimization and Improvements in 5G Communication

Although FDMA technology was widely used in the first generation of mobile communication, it still has some limitations in 5G communication. To better utilize spectrum resources in 5G, FDMA has undergone some optimization and improvements.

#### 2.2.1 Dynamic Spectrum Allocation

Considering the characteristics of a large number of users and dynamically changing communication requirements in 5G communication, dynamic spectrum allocation mechanisms have been introduced. This means that frequency band resources are no longer fixedly allocated to each user but are dynamically allocated according to actual needs to achieve higher spectrum utilization efficiency.

#### 2.2.2 Adaptive Modulation and Coding Technology

To further enhance the performance of FDMA in 5G communication, adaptive modulation and coding technology has been introduced. Different modulation methods and coding rates can be adopted based on the qua