Wireless Modulation Technologies - Cisco DX650 Administration Manual

WLAN Standards and Technologies
1 Adjusts dynamically when associating with an AP if the AP client setting is enabled.
Note
2 Advertised rates by the APs are used. If the Restricted Data Rates functionality is enabled in the Cisco
Unified Communications Manager Administration phone configuration, then the Traffic Stream Rate
Set IE (CCX V4) is used.
For more information about supported data rates, Tx power and Rx sensitivity for WLANs, see the Cisco
Desktop Collaboration Experience DX650 Wireless LAN Deployment Guide.

Wireless Modulation Technologies

Wireless communications use the following modulation technologies for signaling:
Direct-Sequence Spread Spectrum (DSSS)
Prevents interference by spreading the signal over the frequency range or bandwidth. DSSS technology
multiplexes chunks of data over several frequencies so that multiple devices can communicate without
interference. Each device has a special code that identifies the data packets for the device and all other
data packets are ignored. Cisco wireless 802.11b/g products use DSSS technology to support multiple
devices on the WLAN.
Orthogonal Frequency Division Multiplexing (OFDM)
Transmits signals by using RF. OFDM is a physical-layer encoding technology that breaks one high-speed
data carrier into several lower-speed carriers to transmit in parallel across the RF spectrum. When used
with 802.11g and 802.11a, OFDM can support data rates as high as 54 Mbps.
The following table provides a comparison of data rates, number of channels, and modulation technologies
by standard.
Table 18: Data Rates, Number of Channels, and Modulation Technologies by IEEE Standard
Item
Data rates
Nonoverlapping
channels
Wireless
modulation
Cisco Desktop Collaboration Experience DX650 Administration Guide, Release 10.1(1)
80
802.11b 802.11g
1, 2, 5.5, 11 Mbps 6, 9, 12, 18, 24, 36, 48,
54 Mbps
3 (Japan uses 4) 3
DSSS OFDM
802.11a 802.11n
6, 9, 12, 18, 24, 36,
• 20 MHz
48, 54 Mbps
• 40 MHz
Up to 23 13 or 24
OFDM OFDM
Channels: 7 -
72 Mbps
Channels: 15
- 150 Mbps