User's Manual

Wireless operation
Product description
1-16
pmp-0047 (June 2013)
Link operation – Dynamic Rate Adapt
PMP 450 Series products offer four levels or speeds of operation – 1x (QPSK), 2x (QPSK-MIMO-B), 4x (16QAM-
MIMO-B), and 6X (64QAM-MIMO-B). If received power is less due to distance between the AP and the SM or
due to obstructions, or if interference affects the RF environment, the system will automatically and dynamically
adjust links to the best operation level.
The system chooses its operation rate dynamically, based on an internal ARQ (Automatic Repeat reQuest) error
control method. With ARQ, every data slot of every frame sent over the air (except downlink broadcast) is expected
to be acknowledged by the receiver, and if acknowledgement is not received, the data is resent. The sending unit
monitors these resends, and adjusts the operation rate accordingly. A normal system may have links that change
levels of operation as the RF environment changes. Furthermore, the links operate independently; normal operation
can have a downlink running at 6X while the uplink RF environment only supports 2x.
Optimal sector utilization involves having as many links as possible running at 6x. This provides as much capacity
as possible for the sector.
Table 6 Link Budget Details – Dynamic Rate Adapt, 2.4 GHz Variant
Product
Parameter
Performance Details
2x
4x
6x
PMP 450
Modulation
QPSK-MIMO
16-QAM-
MIMO
64-QAM-
MIMO
2.4-GHz Max.
LOS Link
Budget (no
fade margin) –
20 MHz
channel
bandwidth
with Integrated SM
antenna
10.0
4.6
2.0
with connectorized
antenna that adds 14 dB
to SM Range
with Reflector Dish that
adds 14 dB to SM
Range
63.4
28.9
12.9
2.4-GHz Max.
LOS Link
Budget (no
fade margin) –
10 MHz
channel
bandwidth
with Integrated SM
antenna
14.2
6.5
2.9
with connectorized
antenna that adds 14 dB
to SM Range
with Reflector Dish that
adds 14 dB to SM
Range
89.6
40.8
18.2
2.4-GHz Max.
LOS Link
with Integrated SM
antenna
20.1
9.1
4.1