Access Point, Subscriber, BHM definition

Good day
As a data network engineer I am investigating Cambium products for the first time.
I am reading up on this document > Products > PmP (PtMP) Fixed Wireless Broadband Access > PMP 450 FWA
I know it is PMP but let us say we have only 2 nodes to in effect P2P

Basic Model
In the context of the doc above is the following true?

  1. The 2 nodes in question would be an Access Point (AP) and a Subscriber.
  2. The subscriber is in essence a wifi client (e.g. 802.11ac for 5G wifi)
  3. The AP is basically a wifi AP to which the client associates

Assuming the above is accurate then I have these 2 terms understood.

Backhaul Module
For example in the URL above the 450b Retro Subscriber Module (SM)

“increases performance with the addition of the 450b Subscriber and Backhaul Module.”

  1. What then is a Back Haul Module? A piece of hardware that slots in the the parent hardware, in this case the 450b Retro SM?
  2. Does that equate to the acronym BHM? (I have seen BHM elsewhere)

Very much appreciate any help…

Cambium has a somewhat dizzying array of radio products and I can understand some of the confusion when trying to determine what rolls certain radios can play.

The PMP450 platform is a proprietary platform (i.e. It’s not wifi-based, and not compatible with any other Cambium product lines or 3rd party products.) primarily used for point to multipoint services. That being said, there’s nothing that would prevent you from using a PtMP AP with a single client, thus forming a point to point (PtP) link, and furthermore, there are client radios in the PMP450 family, like the PMP450b that can specifically be used as a PtMP client (SM) OR use two of them to form an inexpensive PtP link (backhaul mode).

Then there’s the PTP450 line, again, a proprietary platform, but these products are designed ONLY to be used for PtP’s and cannot be used as a PtMP client.

And yes, you’re right, when you see products being referred to as “BHM” then it’s intended use is specifically for PtP “backhaul” operations (typically in a master/slave roll).

In addition to the PMP450/PTP450 lines, there are other product lines, like ePMP, that also have similar capabilities, but they’re WiFi-based and are typically less expensive and in some cases more flexible in terms of whether a radio can serve multiple rolls like being a PtMP AP, or client, or PtP, even WiFi AP, etc.


Thanks so much Eric! Much appreciated. Let me absorb what you say… thanks again

Eric covered things pretty well.
Here’s another way of describing some of the terms, with a slightly different focus. (I hope I have all of the details correct.)

Cambium point to multipoint systems consist of Access Points (APs) and Subscriber Modules (SMs). For example each piece of PMP450i hardware is designated as an AP or an SM and can only function in the one mode. e.g. An AP cannot be configured to operate as an SM and vice versa.

You referred to BHM as Back Haul Module but I believe that Cambium generally uses BHM to mean Back Haul Master.
A Cambium point to point system consist of one BHM (Back Haul Master) and one BHS (Back Haul Slave). For example the PTP450i hardware can only be used to create point to point links. The BHM versus BHS role is configurable in software for PTP450i hardware.

PTP450i and PMP450i cannot interoperate.

450b Retro hardware can operate in point to multipoint SM mode or in point to point BHM and BHS modes. (But can never function as a multipoint AP.) 450b Retro in SM mode can connect to 450 family APs such as PMP450i and PMP450m.

I don’t know enough about ePMP to comment on it.



Thanks Don very helpful thank you