RPMA (Random Phase Multiple Access) LPWAN (low power wide area network) technology was designed from the bottom up to optimise wide area connectivity for Machine-to-Machine and Internet of Things (M2M and IoT) devices.
It was created by Ingenu, who have deployed an RPMA public network in the U.S. that currently covers more than 30 metro markets. It’s scheduled to serve over 100 by the end of 2017, making it the world’s largest IoT-dedicated network. Partners are currently operating 38 similar networks in Europe and other countries.
The functionality is impressive. It has to be because LPWANs are one of the foundations that underpin the IoT and there are several low-power competing technologies, each of which will involve a trade-off, e.g. between range, data rate, frequency, channel bandwidth, and power consumption, says Bob Emmerson, freelance writer and IoT industry observer.
Vendors are therefore vying for position in what is set to be a highly competitive environment. ABI Research estimates that by 2021 the number of LPWAN connections, excluding legacy cellular technologies, will reach between 400 and 500 million worldwide. Most IoT devices use less than 3MB of data a month, so there is clear need for networks that can sustain the billions of devices having such low resource requirements.
Conflicting claims can be complex to understand, but Ingenu’s marketing is largely based on simple, factual statements. For example, one RPMA access point (AP) provides the equivalent coverage area to18 LoRa™, 30 NB-LTE cellular and 70 Sigfox® APs.
Although LoRa is positioned as a LPWAN technology, its versatile functionality makes it ideal for LPLAN applications. For example, LoRa and RPMA could complement each other in scenarios involving a local area network comprising hundreds or even a few thousand devices communicating with a LoRa-compliant MultiTech gateway. An RPMA module embedded in the gateway would enable wide area connectivity over RPMA networks.
u-blox, a provider of wireless and positioning modules and chips, has partnered with Ingenu to develop and manufacture products that support RPMA technology. Andreas Thiel, u‑blox co‑founder and executive vice president said: “The demand for low-power, wide-area network technologies is growing across the globe. We believe that Ingenu has superior technology to support growth of unlicensed spectrum technologies for professional applications.”
Large footprints, secure messaging
Ingenu’s networks, which operate in the licence-free 2.4 GHz band, has an uplink capacity that supports up to 2 million devices per tower. The cost of putting up a tower, which can cover up to 300 square miles (480 sq. kms) is less than US$15,000. These features translate into low connectivity prices and a high profit margin for the operator.
The channel bandwidth is 80MHz and there is a 1MHz buffer between channels, which allows the system to support 40 simultaneous 1MHz channels. One channel can support an entire network. San Diego Gas & Electric’s entire 4,100 square mile private RPMA network runs on a single 1MHz buffer.
Ingenu employs direct sequence spread spectrum modulation as well as additional proprietary algorithms. This combination results in a guaranteed message arrival for a packet error rate of up to 50%. This means even if half the message packets drop out, the entire message can still be decoded.
Addressing issues
Interference is set to become a key issue in line with increased use of the 2.4GHz band. Ingenu states that RPMA was designed to withstand extreme interference and highlights the -142dB receiver sensitivity. This means that signals get through even when the noise is 3,000 times louder. Normally the wanted signal can only be heard if the interfering signal is quieter. This is a big claim that the company backs up with a detailed technical white paper.
Security is another key issue. Security is built into the system from the ground up. With 256-bit encryption as well as two-way authentication, not only is the message garbled, it is guaranteed via a 16-byte hash. What this kind of hash means is that there is only a 1 in 2256 chance of someone randomly guessing the signature. And once again there is a detailed technical white paper on this topic.
A future-proof design?
Nobody knows how many connected devices will be deployed by 2020. Earlier predictions were unrealistic and there are wide variations. Highs of 50 billion have come down to less than 10 billion, a figure that doesn’t include smartphones, tablets, and computers.
However, it’s clear that the world is entering a new era, where the economic and political importance of cities is growing rapidly and it is in smarter cities where the most critical decisions and actions relating to resource consumption and carbon emissions will be taken. Therefore, we can expect predictions, which are really ‘guestimates’, to start rising. In turn this indicates the need for IoT-centric networks that are cost-effective now (not over-engineered); that will scale massively; and that won’t need replacing in 20 years’ time.
Ingenu has created a communications technology and is deploying networks that match those demanding criteria. That is their marketing pitch, but does it resonate with the solution providers. Do they see RPMA as a way of future-proofing their systems? And how are they responding to alarming environmental issues like pollution in cities?
At the Smart Cities Summit that took place at the end of December in Boston, MA, Ingenu demonstrated an environmental monitoring solution that integrated its network technology with Libelium’s RPMA-enabled Plug&Sense! device that collects information on pollution levels with PTC’s ThingWorx Analytics platform that provides automated predictive modeling.
David Gascón, Libelium’s CTO, said: “LPWAN technologies make IoT solutions affordable for rising markets like environmental monitoring, agriculture or asset tracking. In fact, LPWAN technologies like RPMA facilitate not only a huge number of connections, but also massive access to information that is accelerating new sharing economies and business models that will shape the IoT market of the future.”
Conclusions
There is a lot to like about this technology. It has the requisite functionality, which includes: more than 20 years of battery life for some connected devices; adaptive data rates that help minimise transmit times; and unlike LP-IoT (also known as LP-LTE), RPMA devices do not require certification by carriers. However, while NB-IoT technology is somewhat late to the LPWAN party, it is backed by the combined resources of connectivity ecosystems such as those of Nokia, Telit and Vodafone.
The author of this blog is Bob Emmerson, a freelance writer and IoT industry observer
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