Link Planner Guide - For Licensed Frequency Links

Hi Guys,

Do we have existing guides we can use when designing long/short distance licensed links (using LinkPlanner) specially intended for PTP820S, C & G devices with the following configurations:

1. 1+0

2. 1+1

3. 2+0

4. 2+2 and so on

We do not.

What would you like to see in a set of guides?

What kinds of information are you looking for?


Hi David,

Trying to work on some links using PTP820c. Currently new to this type of radio from Cambium, yet since we have this opportunity thus am trying to work on it. Reading for a while from the community and have already got so many pointers. However still got some questions for configuration options for links with capacity requirements starting from 750 up to 2GB of links with protection requirements. This is why I ask...

Anyway thank you.



How to design high capacity links…

Consider RF loss and system gain, combining traffic, surge suppression, and management.

RF Loss and System Gain

Instead of trying to design a single, high availability, high capacity link with extra large antennas to maximize the system gain, try dividing the throughput by two or four.

Recall that the Ethernet throughput is limited by the traffic on a single port, 1 Gbps.

Sometimes it’s easier to design two links at 500 Mbps each or four links at 250 Mbps each.

It’s easier because the link can achieve these throughputs at lower modulation modes. Lower modulation modes have better sensitivity, so this allows the link to have higher availability.

Combining the links to share an antenna requires mediation devices to connect all of the equipment together. These devices incur RF loss.

Two or four links that share an antenna will have some mediation device loss. Sometimes the mediation device loss is less than the gains the links achieve by operating at a lower modulation mode.

Two links sharing an antenna incur roughly 3 dB loss at each end with a splitter and roughly 0.3 dB loss at each end with an Orthogonal Mounted Transducer or OMT. (The splitter is for links that are Co-Polar, the OMT is for links that are Cross-Polar.)

Four links sharing an antenna incur roughly 6-7 dB loss at each end with a dual splitter and splitter and roughly 4 dB loss at each end with a dual splitter and an OMT.

So if you’re trying to design a high capacity link, you probably want Cross-Polar, since Cross-Polar mediation device losses are much less than Co-Polar mediation devices losses.

You won’t always have the luxury of designing only Cross-Polar links—this is why Co-Polar options exist.

LINKPlanner allows you to experiment with all of the link types to see which ones have the lowest RF loss and highest system gain.

Combining Traffic

What about combining the traffic from multiple Ethernet ports?

The link can use Multi-Carrier Adaptive Bandwidth Control (MC-ABC), internal aggregation (with PTP 820C built-in LAG), or external aggregation (using external Ethernet switches).

MC-ABC is a highly efficient Layer 1 mechanism that load balances traffic across two RF carriers.

PTP 820C internal LAG uses several mechanisms to load balance traffic across two Ethernet ports. (The primary mechanism is “hashing” MAC addresses. This mechanism can be inefficient if traffic doesn’t contain a nicely distributed set of MAC addresses.)

External Ethernet switches use a wide range of techniques to load balance traffic across two Ethernet ports.

If the combined traffic from your link(s) can reliably carry more than 1 Gbps, you may want to bring the traffic down the tower and combine the traffic externally.

If the combined traffic from your link(s) isn’t more than 1 Gbps, use MC-ABC to combine the traffic from the two radios. MC-ABC is more efficient than the PTP 820C’s internal LAG.

Surge Suppression and Management

The DC power port has built-in surge suppression.

ETH1 has built-in surge suppression, if the link uses Power over Ethernet.

So the link will need additional surge suppression if it needs out-of-band management, external DC power (with or without using ETH1), and/or copper Ethernet cabling with ETH2.

The PTP 820C has two “usable” Ethernet ports: one copper, and one SFP. If your switch doesn’t support mixed media for combining traffic, the link will have to use two copper Ethernet runs down the tower, and the link will use a copper SFP module for the 2nd Ethernet connection. That 2nd Ethernet connection doesn’t have built-in surge suppression, so that 2nd Ethernet cable run requires external surge suppression at the top and bottom of the tower.

The simplest links use in-band management, the PoE injector, and ETH1 for traffic. Another simple option is in-band management, external DC power, and a fiber connection to ETH2 for traffic.

Recall that in-band management requires separation of management and user data via VLAN tagging.

Out-of-band management is much simpler, but it requires another Ethernet cabling run, complete with surge suppressors at the top and bottom of the tower.

Does this help?

Is this kind of guidance what you’re looking for?

Do let us know if you have additional questions, and we’ll try to answer them!

All of this (and much, much more) is covered in our PTP 820 training classes. You may want to consider a class if you’re designing complex networks with PTP 820.


1 Like

Hi David,

These are very helpful and brings me a lot of pointers to initially understand licensed MW. I am hoping will be able to attend one of your certification someday.

Really appreciate what you did here....