Wireless_LAN

Wireless LANs provide the capability of accessing Internetworking Resources without "wired".

WLANs gadgets:

inside-building access

LAN extension

outside building-to-building communicaton

public access

SOHO communications

WLANs Architecture

                                Router or AP
          Clients ----------- AP(Access Point)------------WLAN
         PCs|Stations
         Smart Phones

SSID

it is Service Set Identifier, showing the name in WLAN, it can be 2 ~ 32 characters in Length. All devices shall have this SSID to communicate with others in WLAN.

IEEE 802.11

it implements wireless LANs at speed of 1Mbps and 2 Mbps using DSSS (Direct Sequence Spread Spectrum) and Frequency.

DSSS 直接序列展頻

plz ignore the watermark in this graphic

                                   -------------------
data ---- Encode ----- Modulate -------Channel----------Demodulate -------Decode ------ Content of Data
                                   -------------------

IEEE 802.11b

it is used for "hight-rate". Not only 1 & 2 Mbps, it also provides speed of 5.5 & 11 Mbps.

Wi-Fi

it is Wireless Fidelity (保真)！ Wi-Fi means the certificate for IEEE 802.11b. This certificate is governed by WECA, Wireless Ethernet Compatibilty Alliance.

CSMA/CA

it is the method to access with avoidance of collisiom. Since each WLAN station listens to see whether there is a station transmitting.