The point-to-multipoint radio network is the shape most SCADA radio systems actually take: one master radio at the center, many remotes arranged around it, all sharing a single channel. It is a star, with the master as the hub and each remote as a spoke, and its central challenge is coordinating many radios so they do not talk over each other on the one frequency they all share. This guide explains the topology, how polling and channel-sharing schemes like TDMA keep it orderly, and why it dominates field telemetry.
Point-to-Multipoint Network in one line: A point-to-multipoint radio network is a star topology in which a single master radio communicates with many remote radios over one shared channel, typically by polling each remote in turn so only one transmits at a time. It is the dominant SCADA radio architecture because one master and one channel can serve dozens of field sites economically, and the whole design centers on avoiding collisions - either through disciplined master-controlled polling or a time-slot scheme like TDMA that assigns each remote its own moment to transmit.
In a point-to-multipoint network there is one privileged site - the master, usually with an omnidirectional antenna so it reaches remotes in every direction - and many remote sites, each typically with a directional antenna aimed back at the master. All of them operate on the same radio channel. This is fundamentally different from a point-to-point link, which dedicates a channel to just two radios, and from a mesh, where any node can relay for any other. The star keeps the intelligence and coordination at the hub.
Sharing one channel is what makes the architecture economical - a single frequency and a single master radio can serve an entire field of remotes - but it is also the source of the central problem. Radio is a broadcast medium: if two remotes transmit at the same instant on the same channel, their signals collide at the master and both are garbled. Everything about how a point-to-multipoint network is run exists to prevent that collision.
The star shape also concentrates dependency. Because every remote talks only to the master, the master site is critical infrastructure - if it fails, the whole network goes dark, whereas the loss of one remote affects only that site. This is why master and repeater sites are built to higher reliability standards than individual remotes.
The classic way to keep order on the shared channel is master-controlled polling. The master addresses one remote, asks for its data, waits for the reply, then moves to the next remote, cycling through the whole list in turn. Because only the remote that was just addressed is allowed to answer, and the master itself decides who speaks when, collisions are avoided by design. The cost is time: the master must work through every remote sequentially, so a large network with many remotes takes longer to complete a full poll cycle.
The main enemy is the collision that happens when two radios transmit at once. Pure polling sidesteps it entirely by never inviting two remotes to talk simultaneously, but it can be slow. An alternative is a time-division scheme, TDMA, in which the master synchronizes all remotes to a common clock and assigns each one a specific time slot to transmit. Every remote knows its slot and stays silent otherwise, so many remotes can share the channel efficiently without waiting to be individually polled, and the channel time is used tightly.
The choice between straightforward polling and a TDMA scheme is a trade between simplicity and efficiency. Polling is easy to implement and understand and works well for modest networks; TDMA extracts more capacity from the same channel and reduces the delay between a remote's updates, which matters as the number of remotes grows or as faster reporting is required. Both share the same goal - one channel, many radios, no collisions.
Point-to-multipoint dominates field telemetry because it matches the shape of the problem. Oilfield and pipeline operators have one control point and many scattered assets - wells, tanks, compressors, meters - which is exactly a star. Serving all of them from one master on one channel is dramatically cheaper than dedicating a link to each site, and the polling model maps naturally onto how SCADA already gathers data: ask each remote in turn for its register values.
The architecture scales by adding remotes to the poll list and, where terrain intervenes, by adding repeaters that extend the star's reach without changing its logic. A remote behind a hill is simply reached through a relay, but from the master's point of view it is still just another entry in the polling sequence. This combination of a single coordinating master and optional repeaters is what lets one radio network cover a wide, rugged operating area.
A cloud SCADA such as Merobix sits above this radio layer and treats the point-to-multipoint network as one of several ways data arrives. The master gathers each remote's values over the shared channel and hands them up to the cloud, which trends, alarms, and controls across the whole field. Because the master already sequences the remotes, the SCADA host also naturally sees per-site communication health - which remotes answer promptly, which need retries, and whether a whole branch behind a repeater has gone quiet - making the polling structure a built-in diagnostic map of the field.
A point-to-point link connects exactly two radios, often with a channel dedicated to that single link. A point-to-multipoint network connects one master to many remotes over a shared channel in a star topology, with the master coordinating who transmits when. Point-to-multipoint is far more economical for SCADA because one master and one channel can serve dozens of field sites.
Most commonly through master-controlled polling: the master addresses one remote at a time and only that remote may reply, so two remotes never transmit at once. An alternative is TDMA, where the master synchronizes all remotes to a shared clock and assigns each a time slot, letting many share the channel efficiently. Both approaches ensure only one radio transmits on the shared channel at any instant.
Because it matches the field's shape - one control point and many scattered assets form a natural star - and because serving all remotes from a single master on one channel is far cheaper than dedicating a link to each. It also maps directly onto how SCADA gathers data by polling each remote in turn, and it extends over terrain simply by adding repeaters without changing its logic.
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