Motorola PTP 500 User's Guide download pdf (Page 66)

Wireless operation Chapter 1 Product description

phn-1115_006v000

1-26

Sep 2010

The PTP 300 and PTP 500 transmit two signals on the same radio frequency, one of

which is vertically polarized and the other horizontally polarized. The system also has

the ability to adapt between two modes of operation:

• Dual Payload: When the radio channel conditions allow, the system 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 system.

• Single Payload: As the radio channel becomes more challenging, the system 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 system to operate in challenging non- line

of sight radio channels.

The two modes have been implemented by the introduction of two sets of modulation

modes. The lower order modulations (BPSK 0.50 up to QPSK 0.50) are only available

as single payload modes. Each of the higher order modulations (QPSK 0.75 to

64QAM 0.83) are available in single payload mode and dual payload mode. The

switching between modes is automatically controlled by the adaptive modulation

feature described in Adaptive modulation on

ge 1-25.

NOTE

The system automatically chooses between dual and single payload to try to

increase the capacity of a link. However the user may choose 'single payload

only' at installation time, forcing this more robust option.

Intelligent dynamic frequency selection

The PTP 300 and PTP 500 Series use an interference mitigation technique known as

Intelligent Dynamic Frequency Selection (i-DFS). Both the Master and Slave

continually monitor for interference on all channels and then select the best frequency

of operation. This is a dynamic process where the system can continually move

channels in response to changes in interference. Two modes of operation are available:

• The first mode is where the two link directions are forced to select the same

frequency. This is determined by the Master.

• The second mode is where the frequency of operation can be determined

independently for each direction. This uses the CAC measurements. It enables

the system to operate successfully in areas where other radio equipments are

operating within the same band. It is not permitted in radar regions.

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Motorola PTP 500 User's Guide Page 66