Cisco Digital Modulation Technology

Modern mobile communication systems all use digital modulation technology. Because digital communication is flexible in network construction, it is easy to use digital error control technology and digital encryption to facilitate integration and access the Integrated Service Network (ISDN ), therefore, all communication systems are crossing the data in analog mode. As a part of the entire network, mobile communication will inevitably transition from analog to digital. Therefore, digital communication will be a direction and trend for future development.

So what is digital modulation technology? What is the difference between it and Analog modulation technology?

650) this. width = 650; "src =" 51cto.com/uploads/allianz 111027/1430445262-0.jpg "style =" width: 259px; height: 142px "height =" 100 "width =" 180 "/>

Introduction to Digital Modulation Technology

As you know, when we mention digitalization, we will think of a series of "100110101" binary, which has become a representative of digital signals. Yes, digital signals are represented by a large amount of binary signals. The difference between a binary signal and a decimal signal is that a decimal signal is regarded as a decimal signal, while a binary signal is regarded as a decimal signal. For example, decimal 4 is represented as "100" in binary format ".

So what are the advantages of digitalization? First, the processing speed is improved. As we all know, machines and people are different and they will not directly process decimal items, the simplest method of diode in a machine is "on" and "off", so the machine language is a binary language. That is why binary is used. The difference between the simulation and the number lies in whether the signal is digitalized and whether the binary signal is used to represent the original continuous signal. Of course, this is not strictly defined, however, this helps us better understand the differences between simulation and numbers.

So, for example, the analog signal is a continuous signal in both time and value. We sample the data at a certain interval, and then obtain the time discontinuous, continuous numerical signal. Then we use the binary signal to represent each sampling value and obtain our digital signal.

Analog modulation is to use analog signals to modulated the carrier.,Digital Modulation is to use digital signals to modulated the carrier. There are many benefits to using digitalization. The most obvious difference is that anti-interference performance is enhanced and encryption is easy.

In the past decade, the development and development of the new digital mobile communication system has made great progress, requiring both digital signaling and digital information transmission. Therefore, digital modulation technology must be used in the system. However, ordinary digital modulation technologies, such as amplitude key ASK), Phase Shift key PSK) and Frequency Shift key PSK) cannot meet the requirements of mobile communication due to low transmission efficiency, it is necessary to study some modulation technologies with strong anti-interference performance, good error code performance, and high spectrum utilization, so as to increase the bit rate of data transmitted within the Unit band to meet the requirements of mobile communication. In order to apply the 25 kHz channel bandwidth for mobile communication, various narrowband digital modulation methods are proposed. Currently, it has been widely used in digital cellular mobile communication systems, including orthogonal phase shift keying-PSK), orthogonal amplitude modulation (QAM), minimum frequency shift keying (MSK), and Gaussian least Frequency Shift Keying (GMSK). Here, we will only introduce scientific knowledge, so we do not want to introduce these modulation methods one by one. Interested friends can refer to some materials by themselves. However, no matter what modulation method we study, the goal is the same, that is, to meet the requirements of mobile communication's digital modulation and modem technology.

The requirements for digital modulation and modem technology for mobile communication are as follows:

1) The error rate should be as low as possible in the case of channel fading;

2) narrow emission spectrum, with little interference to adjacent channels;

3) Efficient Demodulation to reduce power consumption and further reduce volume and cost;

5) provides a high transmission rate;

6) easy to integrate.

Digital Modulation is divided into linear modulation and constant envelope modulation. linear modulation can be divided into two types: spectrum efficiency and power efficiency. in mobile communication systems, due to the serious decline, the "signal-to-noise ratio" required is relatively high.

In short, the final purpose of the modulation technology we adopt is to make the signals after modulation have a strong resistance to interference, and at the same time, it has little interference with adjacent channel signals, demodulation is convenient and easy to integrate.