Table of Contents
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Chapter 1: Product description
Note
PTP LINKPlanner includes an estimate of mean data rate, the data rate provided by
each modulation and the percentage of time spent in each modulation mode.
MIMO
Multiple-Input Multiple-Output (MIMO) techniques provide protection against fading and increase
the probability that the receiver will decode a usable signal. When the effects of MIMO are
combined with those of OFDM techniques and a high link budget, there is a high probability of a
robust connection over a non-line-of-sight path.
The PTP 650 transmits two signals on the same radio frequency, one of which is vertically
polarized and the other horizontally polarized. Depending on the channel conditions, the PTP 650
will adapt between two modes of operation:
•
Dual Payload: When the radio channel conditions allow, the PTP 650 will transmit two different
and parallel data streams, one on the vertical channel and one on the horizontal channel. This
doubles the capacity of the PTP 650.
•
Single Payload: As the radio channel becomes more challenging, the PTP 650 has the ability to
detect this and switch to a mode which transmits the same data stream on both vertical and
horizontal channels. This provides polar diversity and is another key feature which allows the
PTP 650 to operate in challenging non- line of sight radio channels.
Lower order modulations (BPSK 0.63 up to QPSK 0.87) only operate in single payload mode.
Higher order modulations (16QAM 0.63 to 256QAM 0.81) are available in single payload mode and
dual payload mode. The switching between modes is automatically controlled by the adaptive
modulation feature described in
Note
The system automatically chooses between dual and single payload to try to increase
the capacity of a link. However the user can disable the dual payload mode, forcing
the more robust option of single payload.
Adaptive modulation
on page 1-10.
Page
1-11
Wireless operation
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