Introduction to Communication Multiple Access Technology: Achieving Multi-User Sharing of Communication Resources

# 1. Introduction

## 1.1 What is Multiple Access Communication Technology

Multiple access communication technology is a technique that enables multiple communication users to share limited communication resources. In communication, multiple users share limited spectrum, time, or code resources, and by reasonably allocating resources and effectively coordinating communications, they achieve interference-free communication among users. Multiple access communication technology is widely used in areas such as wireless local area networks, mobile communication networks, and data center networks.

## 1.2 The Role and Significance of Multiple Access Communication Technology

Multiple access communication technology can improve the utilization of communication resources, reduce the equipment costs of communication systems, and effectively manage scenarios where multiple users access simultaneously, ensuring communication quality. Therefore, multiple access communication technology is of significant importance in addressing issues such as mass user access and limited spectrum resources.

In practical applications, multiple access communication technology can be divided into three types: shared multiple access technology, random multiple access technology, and hybrid multiple access technology. Each type has different specific implementations. Next, we will delve into the principles and applications of these technologies.

# 2. Shared Multiple Access Technology

In wireless communication, in order to achieve simultaneous communication among multiple users, the communication system needs to adopt multiple access technology. Multiple access technology refers to a technique that allows multiple users to transmit information simultaneously or almost simultaneously in limited frequency, time, or code resources. Multiple access technology is divided into shared multiple access technology, random multiple access technology, and hybrid multiple access technology.

### 2.1 Frequency Division Multiple Access (FDMA)

Frequency Division Multiple Access (FDMA) refers to dividing the total bandwidth into several narrower frequency bands, with each user occupying a frequency band for communication. Since each user occupies a different frequency band, there is no interference between users.

// Java code demonstrating the implementation of Frequency Division Multiple Access
public class FDMA {
     public static void main(String[] args) {
         int totalBandwidth = 100; // Total bandwidth
         int numUsers = 5; // Number of users
         int bandwidthPerUser = totalBandwidth / numUsers; // Bandwidth allocated per user
         for (int i = 0; i < numUsers; i++) {
             System.out.println("User " + (i+1) + " uses frequency band: " + i*bandwidthPerUser + "Hz - " + (i+1)*bandwidthPerUser + "Hz");
         }
     }
}

The Java code above demonstrates the implementation of FDMA. Assuming a total bandwidth of 100Hz and five users needing to communicate, each user is allocated a bandwidth of 20Hz, with users not interfering with each other.

### 2.2 Time Division Multiple Access (TDMA)

Time Division Multiple Access (TDMA) refers to dividing the total communication time cycle into several time slices, with each user communicating within their own time slice. Through time allocation, data transmission for different users does not result in conflicts. Below is a code demonstration for TDMA:

# Python code demonstrating the implementation of Time Division Multiple Access
totalTime = 100 # Total communication time cycle
numUsers = 5 # Number of users
timePerUser = totalTime / numUsers # Communication time allocated per user
for i in range(numUsers):
     print("User " + str(i+1) + "'s communication time slice: " + str(i*timePerUser) + "ms - " + str((i+1)*timePerUser) + "ms")

The Python code above demonstrates the implementation of TDMA. Assuming a total communication time cycle of 100ms and five users needing to communicate, each user is allocated a communication time of 20ms, with users not experiencing conflicts.

### 2.3 Code Division Multiple Access (CDMA)

Code Division Multiple Access (CDMA) refers to using different code patterns to distinguish the signals of different users on the same frequency and time. Each user uses a unique code pattern for spectrum spreading, and then the signals are superimposed on the same frequency for transmission. The receiving end uses the pre-agreed code patterns to despread and obtain the signal of a specific user.

// JavaScript code demonstrating the implementation of Code Division Multiple Access
const users = ['user1', 'user2', 'user3']; // Users
const codes = ['101', '110', '011']; // Code patterns corresponding to users
const signal = [];
for (let i = 0; i < users.length; i++) {
     signal.push({user: users[i], code: codes[i]});
}
console.log(signal);

The JavaScript code above demonstrates the implementation of CDMA. Users use different code patterns for spectrum spreading, and then the signals are superimposed on the same frequency for transmission. The receiving end despreads the signals based on code patterns to obtain the signals of specific users.

Shared multiple access technology has extensive applications in wireless communications. Different multiple access technologies have their own unique characteristics and advantages, and suitabl