Cisco Systems 8961 Wireless Modulation Technologies, Data Rate Range Receiver Sensitivity 802.11b

Chapter 6 Understanding the VoIP Wireless Network

Understanding WLAN Standards and Technologies

Table 6-2	Tx Power, Data Rates, Ranges, and Decibels by Standard (continued)
Standard	Maximum Tx Power1	Data Rate2	Range	Receiver Sensitivity
802.11b
	17 dBm	1 Mbps	1,010 ft (308 m)	-96 dBm
		2 Mbps	951 ft (290 m)	-85 dBm
		5.5 Mbps	919 ft (280 m)	-90 dBm
		11 Mbps	902 ft (275 m)	-87 dBm

1.Adjusts dynamically when associating with an AP if the AP client setting is enabled.

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 Cisco Unified IP Phone 9971 Wireless LAN Deployment Guide.

Wireless Modulation Technologies

Wireless communications uses 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 its data packets and all others 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. OFDM, when used with 802.11g and 802.11a, can support data rates as high as 54 Mbps.

Table 6-3provides a comparison of data rates, number of channels, and modulation technologies by standard.

Table 6-3	Data Rates, Number of Channels, and Modulation Technologies by IEEE Standard
Item		802.11b	802.11g	802.11a
Data Rates		1, 2, 5.5, 11 Mbps	6, 9, 12, 18, 24, 36, 48,	6, 9, 12, 18, 24, 36, 48,
			54 Mbps	54 Mbps
Non-overlapping		3 (Japan uses 4)	3	Up to 23
Channels
Wireless		DSSS	OFDM	OFDM
Modulation

Cisco Unified IP Phone 8961, 9951, and 9971 Administration Guide for Cisco Unified Communications Manager 8.5 (SIP)

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