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

Technical Special Investigation Classification

Coverage: WPAN WMAN WLAN WWAN (Wide Area 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

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;

Full name: Wireless LAN Media Access Control and Physical Specification (explaining that WLAN has only two layers)

Standard inclusions:...

Reference model

Detailed explanation of the agreement

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

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

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

Overview: 50km; QoS guarantee, high transmission rate, rich services

structure

Services: Active authorization service UGS, real-time polling service rtPS, non-real-time polling service nrtPS, best-effort service BE

Reference protocol model

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

Relative bandwidth>20% or bandwidth>500MHz

Technical features

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