Chapter 3: System planning
Radio Frequency planning
Page
3-20
https://support.cambiumnetworks.com/files/colocationtool
For more information on 450 Platform Family co-location, see
http://www.cambiumnetworks.com/solution-papers
For Cambium co-location tool refer section Cambium co-location tool in Configuration Guide.
Co-location between Cambium PMP 450 Series 3 GHz devices and LTE
devices
When co-locating systems in the same geographical area it is important to select the correct system
parameters in order to avoid interference. Both Cambium PMP and LTE are TDD systems, which means
that the same frequency resources are used both in the downlink and in the uplink but multiplexed in
time. A TDD cycle or frame, is the minimum amount of time used to communicate in both directions,
including gaps for hardware turnaround and over the air propagation delays.
When multiple access points (APs) are deployed in the same geographical area, it is important that they
all transmit and receive at the same time. If one AP transmits when another receives, the AP that is
receiving might not be able to correctly decode the signal coming from the subscriber modules (SMs)
communicating with it, because of the interfering signal coming from the other AP.
In order to avoid this type of interference, three aspects need to be considered:
1.
The TDD cycle, or frame, needs to have the same length for all APs
2.
The TDD cycle, or frame, needs to start at the same time for all APs
3.
The frame parameters need to be selected in each AP so that there is no overlap between one
AP transmitting and another receiving. An example of these parameters is the duty cycle, i.e. the
ratio of the time dedicated to communication in the downlink direction over the total time
frame.
Ensure that these parameters do not need to be the same in all APs, but they need to be
selected to avoid interference. These features are needed regardless of the technology used by
the APs.
LTE frame configuration options
Below table summarizes the LTE frame configuration options.
LTE supports two frame lengths, 5 ms and 10 ms. Each 10 ms interval contains 10 subframes, which are
labeled in the Table as D for downlink transmission, U for uplink transmission, and S for special
subframe. The special subframe contains the turnaround time between downlink and uplink
transmissions.
Configuratio
n
Frame
time
Subframe number
0 1 2 3 4 5 6 7 8 9
0
5 ms
D S U U U D S U U U
1
5 ms
D S U U D D S U U D
2
5 ms
D S U D D D S U D D
Содержание PMP 450 AP
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Страница 161: ...Chapter 3 System planning Radio Frequency planning Page 3 31 Figure 56 cnMedusa Antenna...
Страница 189: ...Chapter 3 System planning Remote AP Deployment Page 3 59 Figure 65 Remote AP wired to SM that serves as a relay...