New Zealand firm 4RF has unveiled its new media access control (MAC) system to help improve channel capacity on SCADA and telemetry radio networks.
4RF has already introduced its Aprisa SR and Aprisa SR+ point-to-multipoint radios, which provide secure communications for telemetry and SCADA applications, along with the Aprisa XE point-to-point link for long distance, carrier-class communications.
4RF claims its Aprisa SR+ system provides the “best channel efficiency” thanks to “its ground breaking capacity, excellent range, and great real world coverage”.
The company refutes the idea that its results are achieved in the lab with just a couple of devices connected to the base station. It said: “Because speed is one thing and throughput is another, and let’s face it – in the real world, when you start loading up the network it gets saturated at around 30% - 40% of the channel capacity.”
However, 4RF says it has found a way round this. “Not only do we deliver breakthrough capacity of 60 kbit/s at 12.5 kHz, 120 kbit/s at 25 kHz and over 200 kbit/s at 50 kHz, we actually achieve 80% - 90% of channel efficiency,’ it claims.
The secret behind this channel efficiency is 4RF’s sophisticated media access control (MAC) implementation. The reason most data heavy networks are saturated at 30% - 40% channel capacity is because they are using traditional CSMA (carrier sense, multiple access) MAC where each radio listens before it sends, the company explains.
4RF uses the analogy of a classroom, where everyone (including the teacher) is allowed to speak at will as long as no one else is speaking. Eventually two or more students will speak at once, especially if something interesting is going on, causing frustration and the need for everything to be repeated.
“What we did is bring the ‘raise your hand’ concept to the SCADA world. Like the classroom teacher one radio, the base station, is in charge. In our deterministic MAC system the base station controls channel access for the entire network using an 'access request with access grant' scheme (AR/AG),” the company says.
“The remotes must request access (or raise their hand), and only when it is granted (or when they’re called upon) can they transmit. This AR/AG dMAC system eliminates data collision and drives channel efficiencies past 80% (so clearly our radios are a bit more obedient than the average classroom student). CSMA does have some advantages in certain situations, but the mainstream works better with our dMAC,’ 4RF asserts.
4RF is now offering potential users trials of its new system. The company HQ is in Wellington, New Zealand, while its European office is based in Nottingham, UK.