User's Manual

Configuration Parameters 20
Channel
802.11a devices spread a radio signal over a range of frequencies. The IEEE 802.11a
specification allocates the available frequencies in the 5 GHz band into a series of
operating Channels that are identified by a Channel number and a center carrier
frequency.
A PCI Card configured for Infrastructure mode receives a Channel assignment from its
Access Point. You cannot configure the Channel for a PCI Card configured for
Infrastructure mode.
For an Ad Hoc network, nodes must use same Channel in order to communicate. You
can configure the PCI Card to scan multiple Channels to locate an Ad Hoc network or
you can configure the card to use a specific Channel. See “Station Configuration” on
page 26 for details. Note that if you wish to install multiple Ad Hoc networks in the
same vicinity, Proxim recommends that you configure each network with a unique
Channel to avoid interference between networks.
The number of available Channels varies by country.
In the United States, the Harmony 802.11a PCI Card with integral antennas can use
eight Channels in 802.11a-compliant mode: Channel 36 (5.18 GHz), Channel 40 (5.20
GHz), Channel 44 (5.22 GHz), Channel 48 (5.24 GHz), Channel 52 (5.26 GHz), Channel
56 (5.28 GHz), Channel 60 (5.30 GHz), and Channel 64 (5.32 GHz).
In the United States, the Harmony 802.11a PCI Card with integral antennas can use
three Channels in 2X mode: Channel 42 (5.21 GHz), Channel 50 (5.25 GHz), and
Channel 58 (5.29 GHz).
Note: See “Radio Frequency Interference Requirements” on page 5 for important
regulatory information concerning Channel selection.
Maximum Send Rate
The IEEE 802.11a specification supports eight data rates: 54 Mbps, 48 Mbps,
36 Mbps, 24 Mbps, 18 Mbps, 12 Mbps, 9 Mbps, and 6 Mbps. Harmony’s 2X mode
supports eight data rates: 108 Mbps, 96 Mbps, 72 Mbps, 48 Mbps, 36 Mbps,
24 Mbps, 18 Mbps, and 12 Mbps.
As a mobile client travels further and further away from an 802.11a Access Point (when
in Infrastructure mode) or from other 802.11a nodes (when in Ad Hoc mode), the data
rate automatically decreases in order to maintain a usable radio connection.
In an Infrastructure network a client that is close to an Access Point may operate at
108 Mbps, but a client that is far away from the Access Point may operate at 12 Mbps.
By default, the Harmony 802.11a PCI Card automatically adjusts the transmit rate
depending on the mode of operation (802.11a-compliant or 2X). However, you can
manually set a maximum rate that the PCI Card will use.
For example, if you configure the Max Send Rate for 36 Mbps, the Harmony 802.11a
PCI Card will only operate at speeds of 36 Mbps or less.