Application of FDM frequency division multiplexing communication in real life 100

It refers to a multiplexing technology in which the carrier bandwidth is divided into a variety of sub-channels of different frequency bands, and each sub-channel can transmit a signal in parallel. FDM is commonly used in broadband networks where analog transmissions are made. In a communications system, the bandwidth provided by a channel is often much wider than the bandwidth required to transmit a signal.

If it is very wasteful for a channel to transmit only one signal, in order to be able to make full use of the bandwidth of the channel, the method of frequency division multiplexing can be used. In a frequency division multiplexing system, the available frequency bands of the channel are divided into several non-overlapping frequency bands, and each signal is transmitted in one of the frequency bands, so that they can be filtered out separately by a filter and then demodulated and received separately.

If the available bandwidth of a physical channel exceeds the bandwidth required for a single original signal, the total bandwidth of the physical channel can be divided into several sub-channels that are the same (or slightly wider) as the bandwidth of a single signal is transmitted; One signal is then transmitted on each sub-channel to enable the simultaneous transmission of multiple signals in the same channel. Before the multi-channel original signal is multiplexed, the spectrum of each signal should be moved to different segments of the physical channel spectrum through spectrum transfer technology, so that the bandwidth of each signal does not overlap with each other. Each signal is then modulated with different frequencies, and each signal is transmitted on a channel of a certain bandwidth centered on its carrier frequency. In order to prevent mutual interference, it is necessary to isolate each channel with anti-interference protection measures.

New applications of OFDM in modern high-speed wireless communication.

Abstract] With OFDM

Successively in DAB, DVB,

The use of OFDM as a key technology

It has become an extremely important technique in modern high-speed wireless communication. In this paper, the application background of OFDM is discussed, the working principle of OFDM is analyzed, and the OFDM is discussed on this basis

Released in the New Zen Mausoleum.

Standard as well as 4G

applications. There are charts in this**,I can't send it here.,If you feel the right counterpart and I'll ask for the full text for free.。

(1) Digital Acoustic Broadcasting Engineering (DAB).

The DAB Dabeureka147 project in Europe has successfully used OFDM technology. In order to overcome the heavy sound phenomenon that may be generated by multiple base stations, people have added a certain protection time slot in front of the OFDM signal, which effectively solves the co-channel interference between base stations, realizes single-frequency network broadcasting, and greatly reduces the frequency band width occupied by the entire broadcasting.

2) HFC network.

HFC (Hybrid Fiber Cable) is a kind of optical fiber coaxial hybrid network. Recently, OFDM has been applied to cable television networks, using optical fiber transmission on trunk lines, while coaxial cable is still used in subscriber distribution networks. This photoelectric hybrid transmission method improves the image quality and can be transmitted to a long distance, expanding the use of cable TV.

3) Mobile communications.

In mobile communication channels, the delay spread caused by multipath propagation is roughly a few microseconds to tens of microseconds in urban areas, which can bring inter-symbol interference and deteriorate system performance. In recent years, there have been studies on mobile communication systems using multi-carrier parallel transmission 16QAM modulation. The combination of OFDM technology, interleaving technology and channel coding technology can effectively fight against inter-symbol interference, which has become the research direction of anti-fading technology in mobile communication environment.

Frequency division multiplexing (FDM) is a frequency-division multiplexing technology. In actual communication, the available bandwidth of a physical channel is often greater than that of a given signal, and FDM takes advantage of this feature. In FDM, the channel is divided into multiple sub-channels according to frequency, and each sub-channel can transmit a signal.

For networks using FDM technology, the wider the frequency band, the more sub-channels can be divided within the bandwidth hole gap. FDM technology is commonly used in broadband computer networks.

Therefore, FDM is also used in the broadband LAN.

Differences and characteristics between frequency division multiplexing and time division multiplexing.

Frequency division multiplexing (FDM) is to divide the total bandwidth of the transmission channel into several sub-frequency bands (or sub-channels), and each sub-channel transmits one signal. Frequency division multiplexing requires that the total frequency width is greater than the sum of the frequencies of each sub-channel, and at the same time, in order to ensure that the signals transmitted in each sub-channel do not interfere with each other, an isolation band should be set up between the sub-channels, so as to ensure that the signals of each channel do not interfere with each other (one of the conditions). The characteristic of frequency division multiplexing technology is that the signals transmitted by all sub-channels work in parallel, and the transmission delay can be ignored when each channel is transmitted.

Time division multiplexing (TDM) is to divide the time provided to the entire channel to transmit information into several time slices (referred to as time slots), and assign these time slots to each signal source, and each signal occupies the channel in its own time slot for data transmission. Time division multiplexing technology is characterized by the fact that time slots are planned and allocated in advance and are fixed, so it is sometimes called synchronous time division multiplexing. Its advantage is that the time slot distribution is fixed, which is convenient for adjustment and control, and the appropriate section is purely pure for the transmission of digital information; The disadvantage is that when a signal source has no data transmission, the channel corresponding to it will be idle, and other busy channels cannot occupy this free channel, so the utilization rate of the line will be reduced.