Cambium PTP 670 Series, User Manual

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Chapter 1: Product description Wireless operation
Page 1-15
The asymmetric options are available independent of TDD Synchronization.
The available Link Symmetry options in HCMP topology depend on Channel Bandwidth and
the number of Slaves, as shown in
Table 3 .
Table 3 Link symmetry options in HCMP
Channel Bandwidth Number of slaves Supported Link Symmetry options
20 MHz Two 3:1, 2:1, 1:1, 1:2, 1:3
Three 2:1, 1:1, 1:2
Four 1:1
40 MHz Two, Three 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4
Four 3:1, 2:1, 1:1, 1:2, 1:3
Five, Six 2:1, 1:1, 1:2
Seven, Eight 1:1
Further reading
For information about… Refer to…
Link symmetry in synchronized networks TDD synchronization on page 1-26
Effect of link symmetry on link data throughput
capacity Calculating data rate capacity on page 3-26
Data throughput capacity tables on page 3-86
How to configure link symmetry Wireless Configuration page on page 6-25
OFDM and channel bandwidth
The PTP 670 series transmits using Orthogonal Frequency Division Multiplexing (OFDM). This
wideband signal consists of many equally spaced sub-carriers. Although each sub carrier is
modulated at a low rate using conventional modulation schemes, the resultant data rate from
the sub-carriers is high. OFDM works exceptionally over a Non-Line-of-Sight (NLoS) channel.
The channel bandwidth of the OFDM signal is configurable to one of the following values: 5,
10, 15, 20, 30, 40 and 45 MHz. Higher bandwidths provide greater link capacity at the expense
of using more bandwidth. Systems configured for a narrower channel bandwidth provide
better receiver sensitivity and can also be an appropriate choice in deployments where the
amount of free spectrum is limited.
Each channel is offset in center frequency from its neighboring channel by 10 or 5 MHz.
Note
The Channel Bandwidth must be configured to the same value at both ends of the link.
Not all channel bandwidths are available in all regulatory bands.