WAM, bam, thank you QAM
MagnaCom uncloaks high capacity modulation at CES
CES 2015 Startup MagnaCom is using CES to pitch a technology it reckons offers wireless comms an attractive combination of better spectral efficiency and higher capacity.
Those claims are based on what the company calls WAM, which it's pitching as a possible replacement for the ubiquitous QAM-based modulation.
QAM is a standard modulation scheme in which amplitude and phase are combined to represent as many as 256 states. However, as the number of bits increases, the signal-to-noise ratio deteriorates, capping the capacity of QAM schemes.
MagnaCom reckons it's created a modulation scheme that's both backwards-compatible with QAM, but offers significantly higher spectral efficiency.
Its specific claim at CES is that it's demonstrating a QAM-16384-equivalent 14-bit modulation scheme called WAM.
The company is coy on exactly how it achieves this, but CEO Yossi Cohen told The Register the key invention of co-founder and CTO Amir Eliaz is to add what amounts to a “third dimension” to QAM for far greater capacity.
“The reason QAM is two-dimensional is because there's an underlying requirement that you use a linear amplifier,” Cohen said. This, he explained, maintains “mathematical orthogonality between phase and amplitude” in the signal.
The multi-dimensional modulation Eliaz designed creates a lot of noise, Cohen told Vulture South, so the other key development was to deal with that noise.
“Eliminating the need for complete orthogonality … can only be done with a system that does not mandate linearity.”
The most Cohen would say about the third dimension is that it's “a purely digital implementation … the constellation is represented in a completely different way, we're not looking at phase and amplitude.”
In getting its technology to market, Cohen said, MagnaCom is looking at working with standards bodies like the IEEE and 3GPP, and is part of the 5G standardisation effort.
Getting into mass applications through standards is, however, a slow process, so the other market the company is targeting is the wireless backhaul space.
Mobile phone network operators need to deliver higher capacity to their towers, he said: “Everybody is struggling to deal with the massive data streams from the billions of cell phones out there, and with the massive emergence of the Internet of Things.
“What we are showing [at CES] is a 10dB system gain – that can be translated into significantly longer distances”, he said, with tests showing that distances can be increased by 400 per cent. Alternatively, the WAM scheme can be used to save system power, or to save spectrum.
“You can save in the neighbourhood of 40-50 per cent on your spectrum,” he claimed, and given the value of spectrum licenses, that's “a significant impact” on mobile carriers' costs. ®