Wireless Network Standards

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Be aware of the following regarding several possible wireless

network implementations:

· The

actual speed depends on several factors, including distance, obstructions (such

as walls), and interference.

· The

actual maximum distance depends on several factors, including obstructions,

antenna strength, and interference. For example, for communications in a

typical environment (with one or two walls), the actual distance would be

roughly half of the maximum.

· The

speed of data transmission decreases as the distance between the transmitter

and receiver increases. In other words, in practice, you can get the maximum

distance or the maximum speed, but not both.

· The

ability of newer devices to communicate with older devices depends on the

capabilities of the transmit radios in the access point. For example:

oSome

802.11n devices can transmit at either 2.4 GHz or 5.75 GHz. However, a single

radio cannot transmit at both frequencies at the same time.

oMost

802.11g devices can transmit using DSSS, CCK, DQPSK, and DBPSK for backwards

compatibility with 802.11b devices. However, the radio cannot transmit using

both DSSS and OFDM at the same time.

This means that when you

connect a legacy device to the wireless network, all devices on the network

operate at the legacy speed. For example, connecting an 802.11b device to an

802.11n or 802.11g access point slows down the network to 802.11b speeds.

· Many

802.11n access points can support clients running other wireless standards

(802.11a/b/g). When a mix of clients using different standards are connected,

the access point must disable some 802.11n features to be compatible with

non-802.11n devices, which decreases the effective speed.

· A dual

band access point can use one radio to transmit at one frequency, and

a different radio to transmit at a different frequency. For example, you can

configure many 802.11n devices to use one radio to communicate at 5.75 GHz with

802.11a devices, and the remaining radios to use 2.4 GHz to communicate with

802.11n devices. Dual band 802.11a and 802.11g devices are also available.

· When

you configure an access point, some configuration utilities use the term mixed

mode to designate a network with both 802.11n and non-802.11n clients.

In this configuration, one radio transmitter is used for legacy clients, and

the remaining radio transmitters are used for 802.11n clients. For example,

802.11b/g/n mixed mode allows for shared access with wireless 802.11 b, g, and

n devices at the same time and at the specified rates for each standard.

· Some

newer 802.11a or 802.11g devices provide up to 108 Mbps using 802.11n pre-draft

technologies (MIMO and channel bonding).