Everything About 4G Modulation Techniques

In the previous article, we delved into 3G modulation techniques, identifying QPSK and 8PSK as the major modulation techniques used in the Third Generation network.

In this article, we will discuss 4G modulation techniques. We will begin by explaining some of the fundamentals of modulation and proceed to cover the various modulation techniques employed in 4G.


In Case you are in a rush, here is a quick summary of this article on 4G modulation techniques:

Quadrature Amplitude Modulation (QAM) and Quadrature Phase Shift Keying (QPSK) are the two major 4G modulation techniques.

4G utilized these modulation techniques alongside multiplexing technologies like OFDM,  FDM, CDMA and SDMA to enable the faster voice and data transmission achieved in the 4G era.

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Understanding Modulation: A Brief Overview

Modulation is the process of Joining a message signal with a carrier signal and transmitting both together to the receiver.

Message signals usually have low strength and will weaken before getting to the destination, so carrier signals help extend them to the receiver. At the receiver, the message signal is then extracted from the carrier signal( a process known as demodulation).

As we mentioned in the 3G modulation technique, there are two primary forms of modulation: analog modulation and digital modulation.

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Analog modulation techniques were predominant in earlier mobile network generations. However, digital modulation techniques are adopted in later-generation networks, like in 2G modulation, 3G modulation and 4G modulation.

What is  Digital Modulation?

Digital modulation is the process of encoding digital information into a carrier signal for transmission. Unlike analog modulation, which deals with continuous signals, digital modulation operates on discrete signals represented by binary digits or bits, typically denoted as 0s and 1s.

Image showing analog signal and digital signal

Digital modulation techniques map the digital information onto specific characteristics of the carrier signal, such as amplitude, frequency, or phase.

The image below shows a carrier signal modulated with a Digital signal. As you can see, when the amplitude of the digital signal (the message signal) is 1, the amplitude of the modulated signal becomes maximum, and when the amplitude of the Message signal becomes 0, the Amplitude of the modulated signal becomes 0.

An image showing Digital modulation

 4G Modulation Techniques

The two major 4G  modulation techniques are Quadrature Phase Shift Keying and Quadrature Amplitude Modulation. However Quadrature Amplitude Modulation is further divided into 3 other forms. We will cover all of them one-by-one.

1) Quadrature Phase Shift Keying (QPSK): QPSK is commonly used in 4G networks for digital data transmission. It encodes two bits of information per symbol by modulating the carrier signal’s phase.

2) Quadrature Amplitude Modulation (QAM): QAM is a modulation technique that simultaneously adjusts both the amplitude and phase of a carrier signal to encode digital data. It’s a combination of amplitude modulation (AM) and phase modulation (PM). The term “quadrature” comes from the use of two orthogonal carriers, one in phase (the I channel) and the other in quadrature (the Q channel), to encode the information.

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QAM allows multiple combinations of amplitude and phase, enabling it to transmit multiple bits of data per symbol. The constellation diagram, a graphical representation, shows these combinations as points in a grid-like pattern.

constellation diagram

Quadrature Amplitude Modulation is subdivided into three: 16-Quadrature Amplitude Modulation, 64-Quadrature Amplitude Modulation, and 256-Quadrature Amplitude Modulation

16-QAM (16-Quadrature Amplitude Modulation): 16-QAM divides the constellation diagram into 16 distinct points, representing 16 possible combinations of amplitude and phase. Each point encodes a unique pattern of four bits of digital data. This means that each symbol carries four bits of information.

64-QAM (64-Quadrature Amplitude Modulation): 64-QAM further subdivides the constellation diagram into 64 points, offering 64 possible combinations of amplitude and phase. Each point encodes a specific pattern of 6 bits of digital data, allowing each symbol to carry 6 bits.

256-QAM (256-Quadrature Amplitude Modulation): 256-QAM takes the concept further by dividing the constellation diagram into 256 points, enabling 256 unique combinations of amplitude and phase. Each point corresponds to a pattern of 8 bits of digital data, resulting in each symbol carrying 8 bits.

The Significance of 4G Modulation Techniques

4G networks brought many advancement in terms of data speeds, capacity, and overall network performance to wireless communication technology. .

Let’s explore some of them.

  1. High Data Rates: One of the features of 4G networks is their ability to deliver exceptionally high data rates. This is possible because it uses advanced modulation techniques such as OFDM and higher-order QAM schemes. These techniques allow for the transmission of larger amounts of data within a given time frame. This capability ensures a good experience for bandwidth-intensive applications like video streaming, online gaming, and large file transfers.
  2. Enhanced Spectral Efficiency: Spectral efficiency refers to the efficient utilization of the available frequency spectrum. 4G modulation techniques, particularly OFDM, excel in this aspect. By dividing the frequency band into subcarriers and allocating them based on channel conditions, 4G networks optimize spectrum utilization. This results in a higher number of users being able to access the network simultaneously and supports improved data throughput.
  3. Improved Signal Quality: 4G modulation techniques are designed to enhance signal quality and combat various channel impairments. Advanced modulation schemes like QAM and MIMO help mitigate the effects of multipath propagation, fading, and interference. These techniques enable improved signal reception, reduced transmission errors, and enhanced reliability of wireless communication in 4G networks.
  4. Multimedia Support: 4G networks are built to support a wide range of multimedia services, including high-definition video streaming, video conferencing, and real-time gaming. The high data rates and low latency achieved through this advanced modulation techniques ensure smooth multimedia experiences. Users can enjoy bandwidth-intensive applications without compromising on quality or experiencing disruptive buffering.
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