TANDBERG D12809 Benutzerhandbuch

Seite von 8
TANDBERG 
TANDBERG and Wireless LANs
 
1.  Overview Of Wireless Standards 
1.1  802.11 Wireless Ethernet 
Ethernet was pioneered by Xerox in the 1970’s and was in fact a registered trademark of 
Xerox Corporation.  After further development, the technology was improved and became 
known as Ethernet II.  Xerox, with the help from Digital and Intel began establishing and 
publishing the standards.  Realizing the international community would not recognize the 
standard, IEEE was charged with formalizing the standard along with other LAN 
technologies.  The 802 committee was assembled to investigate Ethernet, Token Ring, Fiber 
Optic, and other LAN technology.   
1.1.1  802.11a 
The 802.11a specification applies to wireless ATM systems and is primarily used in access 
hubs.  This specification operates at 5GHz and 6GHz.  By using a modulation scheme of 
orthogonal frequency division multiplexing (OFDM), 802.11a can achieve speeds up to 
54Mbps.  However, speeds of 6Mbps, 12Mbps and 24Mbps are more common.  
1.1.2  802.11b 
The 802.11b specification, also known as Wi-Fi, uses complementary code keying (CCK) 
phase-shift keying (PSK) instead of the traditional phase-shift keying (PSK) used in 802.11.  
The use of CCK allows for higher data speeds and less interference to multipath-propaga tion 
interference.  802.11b operates at 2.4GHz and allows for speeds up to 11Mbps. 
1.1.3  802.11g 
The 802.11g specification allows for speeds up to 54Mbps over short distances.  The 
802.11g standard also operates at 2.4GHz and is compatible with 802.11b. 
 
1.2  BlueTooth 
BlueTooth is another wireless standard named for the 10
th
 Century Viking king Harald 
Blåtand of Denmark.  The Bluetooth wireless specification defines a low-power, low-cost 
technology that provides a standardized platform for eliminating cables between  mobile 
devices and facilitating connections between products.  Bluetooth operates at the unlicensed 
2.4GHz frequency.  The standard uses a spread spectrum, frequency hopping, full-duplex 
signal at up to 1600 hops/sec. The signal hops among 79 frequencies at 1 MHz intervals to 
give a high degree of interference immunity.