What does the baseband of mobile phone mean?

Baseband is a circuit in the mobile phone, which is responsible for demodulating, descrambling, despreading and decoding the wireless signals in the mobile network, and transmitting the finally decoded digital signals to the upper processing system for processing.

In our mobile phone, it usually consists of two parts, one is the advanced processing part, which is equivalent to the computer we use; The other part is baseband, which is equivalent to the modem we use. What network standard does the mobile phone support (GSM, CDMA, WCDMA, TD-SCDMA, etc.)? ) is determined by it, just like the difference between ADSL modem and ordinary narrowband modem.

When we use mobile phones to make phone calls, surf the Internet, send text messages, etc. We send instructions (usually standard AT instructions) to the baseband part through the upper processing system, and these instructions will be processed and executed by the baseband part. After the baseband part is processed, a logical channel will be established between the mobile phone and the wireless network, and our voice, SMS or Internet data packets will be sent out through this logical channel.

Baseband transmission:

When the baseband signal is transmitted directly in the channel, it is called baseband transmission. The system used for baseband transmission is called baseband transmission system. The entire channel of the transmission medium is occupied by baseband signals. Baseband transmission does not need a modem, so the equipment cost is low, the speed is high and the bit error rate is low. It is suitable for short-distance data transmission, and the transmission distance is within 100 meters. Widely used in audio local telephone and computer network communication. In wired channel, the signal transmitted when communicating directly with teletypewriter is baseband signal. Enterprises or factories can connect a large number of terminals to the host in this way. Baseband data transmission rate is 0 ~ 10 MB/s, more typically, 1 MB/s ~ 2.5 MB/s, which is usually used to transmit digital information.

Extended data:

Baseband signal (baseband signal)

The unmodulated (spectrum shift and transformation) original electrical signal sent by the source (also known as the transmitter) is characterized by low frequency, and the signal spectrum starts from near zero frequency and has a low-pass form. According to the characteristics of original electrical signals, baseband signals can be divided into digital baseband signals and analog baseband signals (correspondingly, signal sources are also divided into digital signal sources and analog signal sources. ) is determined by the source. To put it more bluntly, a baseband signal is a signal that directly expresses the information to be transmitted. For example, the sound wave we are talking about is the baseband signal. (If a signal contains an AC component with infinite frequency and a possible DC component, it is a baseband signal. )

Because the attenuation of baseband signal is not great in a short distance, the signal content will not change. Therefore, when the transmission distance is close, computer networks all adopt baseband transmission mode. For example, signals from computers to monitors, printers and other peripheral devices are transmitted at baseband. Most LANs use baseband transmission, such as Ethernet and token ring network. The universal network design standard 10BaseT uses baseband signals.

References:

Baidu encyclopedia-mobile phone baseband