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From lowest to highest data rates, the available modulation/FEC settings are:
•
BPSK- ½
•
QPSK- ½
•
QPSK- ¾
•
QAM16- ½
•
QAM16- ¾
•
QAM64-
⅔
•
QAM64- ¾
•
AUTO
Modulation settings on the Base Station are used as a global default value for all Client units. See
section 9 for details on how to configure modulation settings for each client individually. (or some
mention of how these settings are over ridden on a per client basis)
Adaptive Coding and Modulation (ACM)
The AUTO setting above will enable the ACM function in
the network. This feature allows the system to determine the best TX modulation and MIMO settings
based on current RF conditions. At power-up (or reset), the ACM function will begin operation at the
most robust modulation and MIMO settings (BPSK-1/2, 1 stream). If link conditions warrant, higher
order settings will be tested and selected for use.
The ACM function operates continuously, i.e. – if RF link conditions change, then the modulation and
MIMO settings will respond in order to maximize link capability without compromising reliability.
The system relies upon user traffic to determine the optimal modulation settings. When ACM is
enabled, user traffic must be available in order to bring link performance up to its maximum
capability.
ACM is a feature that is enabled on a per-radio basis. It is not necessary for both radios to share the
same state ACM enable/disable configuration.
ACM seeks to optimize the TX modulation of the radio on which it has been enabled. Since RF
conditions may not be the same on either side of the link, due to impairments such as interference,
the system may not select the same TX modulation/MIMO settings for each side.
The RF power settings will not be adjusted by the ACM system.
If the RF power is set above one of the power/modulation thresholds listed in the
Transmit Power
section, the ACM system will not likely reach higher order modulations. For example, if the radio
power is set to 23dBm, then the ACM will not be capable of achieving QAM16 or QAM64 operation.
Tx Streams
The power of MIMO technology rests on the ability to define the number of data
streams that are carried across the two (2) RF links. At all times, the Access 100 Series radios
utilize a 2x2 dual-chain MIMO format where 2 RF transmit and 2 RF receive chains are enabled and
active. However, these dual chains can be used to carry 1 or 2 data streams.
In a 2 stream configuration, unique data is carried across each RF chain, greatly increasing the
amount of data capacity over a non-MIMO system. The 100 Mbps capability of the product requires
that 2 streams operation be configured.
