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

Not quite correct;

As you can see above, a PMP 450 AP can be used as a SM.

@Shaun - it helps; please see below;

PMP 450 forms apart of Cambium Networks Fixed Wireless Access (FWA) range of products; they do not use 802.11 protocols to form a wireless link - however the System on Chip (SoC) may share cards or radios with commodity chips from the same 802.11 manufactures.

To build a Point to Multipoint (PMP or PtMP) FWA network with PMP 450 you’ll need an Access Point (AP) or a Subscriber (SM).

Please note the following;

PMP 450 AP can act as a SM except for 450m
PMP 450 SM can turned into a Point to Point (PTP) link, but a AP cannot!

When a SM is turned into a PTP Link configuration, this is called Backhaul and a PMP 450 SM in BH has to be either a Master or Slave configuration - these are called BHM and BHS.

Current Range of PMP 450 Product are:

Access Points:

  • PMP 450i AP
    – 2x2 MIMO Access Point
    – Workhorse of the PMP 450 range
    – Used in Mission Critical Applications
    – Industrial and Rugged design
  • PMP 450m AP
    – 14x14 Massive Multi-User MIMO
    – High Density FW Access
    – Absolute Beast of a AP
  • PMP 450 MicroPop
    – Lower cost AP
    – Setup coverage in hard to reach areas
    – Omni or Directional Antenna


  • PMP 450b SM
    – Low-Cost Commodity SoC
    – Non Industrial
    – User Friendly Installation
    – 450b Retro = 9db
    – 450b Mid-Gain = 17db
    –450b High Gain = 24dB

  • PMP 450i SM
    – Mission Critical Subscriber
    – Industrial design and build quality
    – Amazing dynamic interference filtering

Hope that helps, if you’re looking at any large or small project, Cambium Networks has online training courses for partners and there are Instructors around the world to help; If you’re in Oceania, Southeast Asia etc I might be able to help out.


1 Like

A few clarifications:
450 P11 hardware can be a PMP SM or PTP based on Feature Key (and flashing a new image on)
450 P12 hardware can only be Point-to-Multipoint Access Point (PMP AP) and it cannot run as a SM.
450i P13 hardware can be a AP/SM/PTP based on the Feature Key (just needs reboot)
450m P14 hardware can only be a PMP AP (edited)
450b P15 hardware, like 450i, can be a AP/SM/PTP based on the Feature Key (just needs reboot)
450v P16 hardware is still being developed but will operate similar to 450i and 450b


Thank you guys!
All this wisdom!
Much gratitude…


Absolutely happy to help, it’s a great community here.

The PMP 450 series has been around for a long time; it’s a constant evolution. Hence it can be a little confusing at the moment, but’ll make sense if you ever do get your hands on equipment.

As you mentioned that you’re a data network engineer, is this project for your company or are you looking to design a solution for a client/customer

I can assure you, Cambium Networks has the best Demo/NFR program

Thanks for the P numbers; I’ll try and remember that for my training courses

Thanks again for all the product/architecture help, much appreciated.
Another question… does the term Fixed Wireless mean anything in particular in the context above?
Thanks again…

“Fixed Wireless” or typically referred to as “Fixed Wireless Access” aka FWA is just another term for point to multipoint (PtMP) access where you have a base station feed one or more wireless clients that are stationary or “fixed” in their position. This is opposed to nomadic (slow moving or semi-mobile access… e.g. clients at a construction site, marina, campus, etc slowly moving within the coverage area of 1 or possibly several base stations), or mobile access (think traditional cel phone mobility quickly roaming across possibly multiple base stations).

Cambium provides equipment solutions for all 3 situations.

Got it! Thanks Eric!!!

This is minor but might want to not call the new version 450v. Over the phone it is too close to b and on the keyboard it is right next to b. Maybe another letter such as 450q.

Agree with your feedback, but this choice is above my pay grade. :slight_smile:

I’ve had to say “450Vector” already before.

1 Like

When I hear the word vector, I think disease vector. Hopefully Cambium management does not want to be associated with such an ill term.

450Victor I meant :slight_smile:


Not Vector from Despicable Me?