Modern communication network
- Communication network: A network that transmits and exchanges according to pre-agreed rules (protocols).
- Three stages of communication technology:
(1) Voice and text communication stage
(2) Electrical communication stage
(3) Modern communication stage - The evolution of communication technology
Connection network: from metal contacts to digital switches (discrete components—> integrated components—> optical switches)
Information form: from analog to analog / digital hybrid, to full digital (current—> electric pulse—> optical pulse)
Information content: from text to language; from images and videos to VoIP and big data.
Modulation and demodulation: from analog modulation AM (amplitude modulation), FM (frequency modulation), PM (phase modulation), to digital modulation GMSK (Gaussian minimum frequency shift keying), OQPSK (quadrature four-phase phase shift keying), QAM (quadrature amplitude modulation), etc.
Error correction coding: from parity error correction codes, CRC (cyclic redundancy error correction), to convolutional codes, interleaved codes, Turbo codes, etc.
Multiplexing: from traditional space division, frequency division, time division multiplexing, to statistical time division, code division, orthogonal frequency division multiplexing, and dense wavelength division, coarse wavelength division, polarization multiplexing, etc.
Control methods: from electromechanical to electronic, to stored program control (SPC), and now to intelligent control.
Signaling method: from the associated signaling to public signaling, and now to various broadband signaling and protocols based on packet networks.
Multiple access methods: frequency division multiplexing multiple access, frequency division, time division multiplexing multiple access, code division multiplexing multiple access and orthogonal frequency division multiplexing multiple access.
Switching technology: from circuit switching to packet switching, ATM switching, to soft switching, IMA (IP Multimedia Subsystem).
Transmission mode: from single carrier, from microwave to satellite, from PDH (quasi-synchronous digital series) to SDH (synchronous digital series), MSTP (multi-service transmission platform), to now ITN (packet transmission network).
Transmission bandwidth: Whether it is from wired to wireless, or from copper wire to optical fiber, the change from narrowband to broadband is basically achieved.
- The communication network is generally composed of terminal equipment, transmission systems and switching nodes. There are three elements of the communication network.
- Wireless transmission channel
Long wave channel: The frequency is below 300KHz and the wavelength is above 1000m.
Medium wave channel: frequency band is 0.3 3MHz, wavelength is 100 1000m.
Shortwave channel: The frequency band is 3 30MHz, and the wavelength is 10 100m, also known as high frequency channel.
Ultrashort wave channel: The frequency band is 30 ~ 3000MHz.
- The development of
modern networks Modern communication networks are developing in the direction of intelligence, personalization, dataization, digitization, broadbandization, and integration.
Data services are mainly divided into the following 5 categories: video services (including streaming media multicast, on-demand TV, video telephony, etc.), high-speed Internet services, VoIP services, interactive games and other media game applications, information service applications.
computer network
- The end systems are connected together through communication links and packet switches.
Physical media: coaxial cable, copper wire, optical fiber and radio spectrum.
TCP: Transmission Control Protocol.
IP: Internet Protocol.
The end system is often referred to as a host, and the host is divided into clients and servers.
- Internet access
Home Internet access: DSL (Digital Subscriber Line), cable, FTTH, dial-up and satellite.
Corporate Internet access: Ethernet and WiFi.
- The message can be understood as information, this is just my personal understanding, because the English message of the message.
- Grouping: In order to send a message from the source system to the destination system, the source divides the long message into smaller data blocks, which are called packets.
Packet switches: routers and link layer switches.
- Packet loss: Due to limited buffer space, an arriving packet may find that the buffer has been completely filled with other packets waiting to be transmitted. In this case, packet loss will occur, also known as packet loss.
- There are two basic methods for moving data through network links and switches: circuit switching and packet switching.
- Types of delay: node processing delay, queuing delay, transmission delay, and propagation delay.
- The protocol stack of the Internet is composed of 5 layers: physical layer, link layer, network layer, transport layer and application layer.
- The 7 layers of the OSI reference model: application layer, presentation layer, session layer, transport layer, network layer, data link layer, and physical layer.
References:
Modern Communication Network Second Edition
Computer Network Top-down Sixth Edition
