Quadrature Amplitude modulation (QAM)
Table of Contents
What is QAM (quadrature amplitude modulation)?
Two amplitude modulation (AM) signals are combined into one channel using QAM (quadrature amplitude modulation). Its effective bandwidth is doubled as a result of this method. In digital systems, such as wireless applications, QAM is also used in conjunction with pulse AM (PAM). Similar to a translator, a QAM modulator aids in the seamless conversion of digital packets into analog signals.
High levels of spectrum usage efficiency are attained using QAM. To achieve this, a form of modulation is provided using both the amplitude and phase components. The QAM signal in this instance has two carriers. The term quadrature refers to a pair of waves that have the same frequency but differ in phases by 90 degrees, or one-fourth of a cycle.
The I signal and the Q signal are the names of the two signals, respectively. One of the signals can be mathematically represented as a sine wave, and the other as a cosine wave. At the source, the two modulated carriers are combined for transmission. The carriers split apart at the destination, where the data is extracted from each. The original modulating information is then updated with the new data.
What is quadrature amplitude modulation in Wi-Fi?
Since Wi-Fi 5’s introduction, networking equipment has used 256-QAM. It is known as 256-QAM when there are 256 possible combinations for 8 bits. The term “1024-QAM” refers to a communication method where 10 bits are sent over a single time period. With improvements like 1024-QAM in Wi-Fi 6, this technology performs well in domestic applications and has a marginally higher bandwidth utilization. This is especially true for connections using Gigabit Ethernet at high speeds.
What is the difference between analog and digital QAM?
QAM systems are used in some analog transmissions, such as AM stereo. QAM, however, excels in applications involving data. This is because when used in anything from mobile phones to Wi-Fi, it offers a very effective form of modulation for data. The majority of high-speed data transmission techniques use QAM. Carriers can send multiple analog signals thanks to analog QAM. Phase Alternating Line and National Television Standards Committee systems, for instance, both employ QAM. In this instance, the signal can carry color or chroma data components thanks to the various channels provided by QAM.
AM stereo radio applications use a system referred to as Compatible QUAM. In this case, the various channels allow for the stereo pair of channels to be carried by a single carrier. Quantized QAM is a common name for digital QAM. The majority of data-based radio communications systems have them built in. Different QAM formats, for instance, are used by radio communication technologies ranging from Long-Term Evolution to Worldwide Interoperability for Microwave Access and Wi-Fi. Expect to see more QAM systems used in radio communication technologies as the field develops.
What is QAM in cable TV?
QAM systems are popular in the cable television industry.
QAM is used by MSOs (multiple system operators) and other network operators to deliver voice, video, and data services. In hubs where signals are analyzed and distributed across the cable operator’s network, QAM systems offer formatting services. Cable modems and set-top boxes convert QAM signals back into their original format once they reach the subscriber’s home. Network operators have an increasing demand for QAM channels. Consumer use of high-definition televisions, high-speed data, video conferencing, and other technologies is what is causing this explosion in demand. MSOs require QAM from the perspective of overall costs.
What are the advantages and disadvantages of using Quadrature Amplitude modulation?
The effective use of bandwidth is the main advantage of QAM variants. This is due to the fact that QAM uses more bits per carrier. 256-QAM, for instance, maps to 8 bits per carrier, while 16-QAM, maps to 4 bits per carrier. Although QAM increases the effectiveness of radio communication transmissions by using both amplitude and phase variations, there are some serious drawbacks. For instance, QAM is more noise-sensitive. This is due to the close proximity of the transmission states, which results in less noise being needed to move the signal from one location to another.
Receivers with phase or frequency modulation, as opposed to QAM systems, can limit amplifiers and eliminate any amplitude noise. This method reduces the reliance on noise. Additionally, linear amplifiers are not required when the phase or frequency modulated is amplified in a radio transmitter. However, linearity must be preserved in QAM that has an amplitude component. Unfortunately, the efficiency of these linear amplifiers is subpar, and they use more energy. Comparing QAM receivers to those of other modulation types and systems reveals that they are also more complicated. They are not the ideal option for mobile applications, therefore.