back to article WAM, bam, thank you QAM

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 …

  1. Anonymous Coward
    Anonymous Coward

    IF this is real

    It would be applicable to more than just mobile operators. The satellite industry would be willing to pay a lot for 10 db additional noise margin to play with!

    1. fLaMePrOoF

      Re: IF this is real

      Not to mention the cable industry, although replacing all linear amps across an HFC network would be very costly...

      I'll be very interested to see how this develops.

      1. Arnold Lieberman

        Re: IF this is real


        My understanding of the article suggests there is no requirement to change the amplifier type to something other than linear, but that the demodulator (hardware + algorithm) is the bit that needs updating. The implication is that there is less need for perfect linearity across the transceiver.

  2. fearnothing

    400 percent extra range on your base stations represents major savings on the number of cell towers needed to maintain full coverage...

    So, after they play with the numbers to show that the 'saving' was actually a 'cost', receiving the associated tax rebate, crowing to their investors about the improved infrastructure efficiency and to the customers about the increased level of service, the end user will be paying, oooh, about... minus ten percent less?

  3. Sykobee

    I look forward to this being applied to Freeview signals (mostly QAM-64 these days IIRC), so that we can get double the number of shopping channels.

  4. AndyFl

    There are physical limitations.

    With high order modulation schemes you need about 3dB Carrier/Interference(C/I) ratio for every bit of throughput per hertz of spectrum. This comes out of information theory - It is a physical limit.

    LTE operates within about 1dB of this physical limit plus around a 20% overhead for channel signalling. You can use signalling redundancy to tradeoff throughput for C/I. The eye-watering throughput claims of operators simply do not apply once you have multiple users on more than one LTE site in operation because they interfere with each other. In practice on a good day you might see around 20mbit downlink performance per cell sector on a 10MHz LTE channel and that is using MIMO. This figure will slowly increase in the future with higher order MIMO and also become more reliable with beam forming techniques.

    You cannot reduce the noise in the channel by fancy coding schemes only by raising your transmit power and QAM based systems use extremely linear transmitters to maintain orthogonality. If the new proposed system dispenses with the linearity requirement you can improve transmitter power efficiency and raise the power with existing devices thereby giving you an improved C/I and more throughput. This is providing the telecommunications regulatory authority lets you increase the power. Cellphone transmit powers are limited to stop you absorbing too much signal with your head.

    In any case most of the time a connection is 'interference limited' in that other transmissions impact the theoretical link C/I and reduce the throughput. If you have a short range connection then you may benefit with the new system but I suspect the improvements will be moderate rather than dramatic.


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