Cambium Networks PMP 450 Series, Руководство по установке

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Chapter 3: System planning 150
Configuration Frame time Subframe number
2 5 ms D S U D D D S U D D
3 10 ms D S U U U D D D D D
4 10 ms D S U U D D D D D D
5 10 ms D S U D D D D D D D
6 5 ms D S U U U D S U U D
Fr am e leng t h
TDD systems can be co-located only if they have the same frame length.
Below figure shows why it is not possible to co-locate APs supporting mismatched frame lengths.
Let us assume that AP1 operates with a 10 ms frame while AP2 operates with a 5 ms frame. Below figure
shows that in a 10 ms interval AP1 has one transmit time and one receive time, while AP2 has two transmit
times and two receive times.
The interference that mostly affects the system performance is the one at the AP receiver.
For example, in the time indicated with the green arrow in below figure, AP1 transmits when AP2 receives.
This may completely corrupt the reception of AP2’s uplink signal.
Also, in the time indicated with the orange arrow in below figure, AP2 transmits when AP1 receives. This
may completely corrupt the reception of AP1’s uplink signal.
As indicated above, LTE supports 5 ms and 10 ms frame lengths. Cambium PMP devices support 2.5 ms
and 5 ms frame length. The only option for co-locating LTE and Cambium PMP devices is for both systems
to operate with a 5 ms frame. This means that a Cambium PMP system can be co-located with an LTE
system operating with Frame Configurations 0, 1 or 2.
Ensure that frame configuration 6 also turns around twice in the 10 ms interval, and its frame length is 5 ms.
However, the two 5 ms frames in the 10 ms interval are not identical.
Since in the Cambium PMP system all frames have the same downlink/uplink structure, the Cambium PMP
system cannot be co-located with an LTE system operating with Frame Configuration 6.
In the Cambium PMP GUI the frame length is selected in the Configuration > Radio > Radio Configuration
page under Frame Period, as shown in below figure.
This parameter must be configured to 5 ms.