MindMap Gallery wireless access technology
Mind map of wireless access technology. Wireless access technology is an access technology that uses some or all wireless means from the switching node to the user terminal. Its characteristics are: nomadic access; complex transmission technology (limited frequency interference, complex fluctuating channels) ;Efficient modulation, powerful error correction and effective MAC protocol
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This is a mind map about bacteria, and its main contents include: overview, morphology, types, structure, reproduction, distribution, application, and expansion. The summary is comprehensive and meticulous, suitable as review materials.
This is a mind map about plant asexual reproduction, and its main contents include: concept, spore reproduction, vegetative reproduction, tissue culture, and buds. The summary is comprehensive and meticulous, suitable as review materials.
This is a mind map about the reproductive development of animals, and its main contents include: insects, frogs, birds, sexual reproduction, and asexual reproduction. The summary is comprehensive and meticulous, suitable as review materials.
wireless access technology
Wireless Access Overview
Overview of Wireless Access Technology
Access technology that partially or completely uses wireless means from switching nodes to user terminals
Features: Nomadic access; complex transmission technology (limited frequency, fluctuations in interference, complex channels); efficient modulation, powerful error correction, and effective MAC protocol
BWA Standardized 802.11 WLAN 802.15WPAN 802.16 WMAN 802.20MBWA Mobile Broadband Wireless Access
Wireless access technology classification
Technical Special Investigation Classification
Fixed: DBS (Direct Broadcast Satellite) system MMDS (Multiple Channel Multipoint Distribution Service) LMDS WLAN WiMax
Mobile: Cellular mobile communication system WeChat mobile system WiMax
Coverage: WPAN WMAN WLAN WWAN (Wide Area Network)
Wireless local area WLAN network access technology
Overview of WLAN network
Radio frequency technology replaces twisted pair copper wires
Network structure: Ad-hoc (no center), AP (with center)
MAC protocol: CSMA/CA protocol
Frequency band: 2.4GHz (ISM band), 5GHz
WLAN network structure
Ad-hoc (no center): equal status of mobile sites; at least two sites; no central station; the service area covered is called independent basic service set IBSS; it is inconvenient to use directional antennas; when users increase, conflicts are severe; suitable for small and medium-sized users Small range networking
AP (with center): mobile station and central site, all mobile stations access through AP; basic service set BSS (a basic WLAN unit network) extended service set ESS;
WLAN system structure: wireless access point AP, wireless network card (station adapter, connection device between computer terminal and wireless LAN), access controller AC (new gateway for broadband network applications)
WLAN frequency band allocation
IEEE802.11 standard
Full name: Wireless LAN Media Access Control and Physical Specification (explaining that WLAN has only two layers)
Standard inclusions:...
Reference model
MAC sublayer
Functions: Access control (DCF and PCF), correlation, authentication encryption, frame fragmentation and reassembly
Physical layer: physical layer convergence sublayer PLCP, physical medium related sublayer PMD
Detailed explanation of the agreement
802.11 works in the 2.4G frequency band, with a transmission rate of 1M/S or 2M/S
802.11b operation: 2.4GHz; frequency range: 2.4--2.4835GHz, 83.5M bandwidth; 13 sub-channels, sub-channel width 22Mhz; adjacent center frequency spacing 5MHz; non-overlapping channels 1 6 11, non-overlapping spacing 25MHz
802.11a maximum rate: 54Mbps; working at 5GHz; OFDM
802.11n 600Mbps 2.4GHz (20MHz mode is enabled by default in this frequency band) 5GHz
802.11ac 5GHz
802.11ax 2.4GHz 5GHz
WLAN security technology: The security protocol has SSID matching check WEP Wired Equivalent Privacy Protocol TKIP Temporary Key Integrity Protocol CCMP Counter Mode Cipher Block Chain Message Integrity Code (based on AES encryption algorithm)
Robust Security Network RSN
Wireless metropolitan area network access WMAN technology
fixed wireless access network
Wireless access: the transmission facility between the user terminal and the network node, part or all of which adopts wireless transmission; fixed wireless access: the wireless access where the location of the user terminal is basically fixed
Features: User terminals are not mobile; provide access to fixed users in a specific area; do not have handover and roaming functions; high operating frequency, in the microwave band; high transmission capacity and multiple services
Basic structure: Generally, a central structure is adopted, and the central station is called a base station; the central station controls the access of all terminals and accesses the wired network at the same time; all terminal stations cannot communicate directly and must be forwarded through the base station
Typical fixed wireless access: LMDS MMDS high-orbit satellite access latest technology 802.16WiMax
Local multipoint distribution service system LMDS wireless optical fiber
High-speed wireless optical fiber; used for integrated video, voice and high-speed data services...
Features: Large communication capacity, system bandwidth up to 1.3GHz
System overview: point-to-multipoint microwave transmission technology; transmission frequency band: Weibo range 20G~40GHz my country 26GHz; bandwidth 1.3GHz; coverage: 3~5km; multi-access mode: FDMA TDMA; modulation mode: QPSK 16QAM 64QAM; communication rate n×64kbps~155Mbps
system structure
Base station user management system backbone network; the communication service range is divided into multiple cellular cells, each cell consists of a base station and several user terminals. A cell can be divided into multiple sectors. Each sector can provide different services according to user requirements. Its capacity is 200Mbps.
System structure: cellular communication structure (area providing services = service area, a base station is set up in each service area as a central station, and the base station communicates with terminal stations in the area through point-to-multipoint wireless links; the base station does not provide user switching across service areas )
System components: terminal station, base station
Point-to-multipoint wireless link
Frequency reuse: base station frequency reuse; orthogonal polarization; multi-carrier
Technical features: centralized control (base station control), uplink and downlink asymmetry, QoS guarantee, duplex communication FDD/TDD, multiple access: TDM/TDMA FDM/FDMA, large system capacity, large capacity provision
China LMDS frequency allocation: 26GHz FDD downlink: 24.507~25.515 uplink: 25.757~26.765
Services provided: Voice service Data IP video
Global Interoperability System for Microwave Access 802.16WiMax Wireless DSL
Overview: 50km; QoS guarantee, high transmission rate, rich services
structure
Point-to-multipoint PMP base station BS user station SS relay station RS interface (G interface connects to the data terminal, F interface connects to the core network)
mesh
There are direct communication interfaces between SSs; SSs have relay/forwarding functions; wireless links between SSs form a mesh structure
Five major advantages of mesh: rapid deployment and easy installation, non-line-of-sight transmission, robustness, flexible structure, high bandwidth
Involving key technologies: multi-channel negotiation, channel allocation, network discovery, routing and forwarding, mesh security
Services: Active authorization service UGS, real-time polling service rtPS, non-real-time polling service nrtPS, best-effort service BE
Reference protocol model
mac layer: business convergence sublayer CS MAC common sublayer encryption sublayer PS
physical layer
Wireless personal area network WPAN access technology
WPAN overview
Located at the end of the entire network chain, it is used to connect terminals at the same location.
Category: low speed, high speed, super high speed
IEEE802.15
Bluetooth system 802.15.1: data rate 720kbps; communication range 10m; TDM and spread spectrum frequency hopping FHSS technology form a piconet (Piconet) without a base station; piconet = master device slave device (up to 7); multiple piconet net=diffusion net
Coexistence 802.15.2
UWB802.15.3
Relative bandwidth>20% or bandwidth>500MHz
Technical features
Insensitive to channel fading
The power spectral density of the transmitted signal is low
low interception capability
Low system complexity
Can provide positioning accuracy of several centimeters
ZigBee802.15.4
Physical layer: using direct sequence spread spectrum
Media access control MAC layer: follow CSMA/CA
Features: short distance, low complexity, low power consumption, low data rate, low cost, large network capacity, short delay, small effective range, flexible working frequency band; emphasis on power saving, simplicity and low cost
Comparison of several wireless networks